Enter your username:
Do you want to login or register?
  • Forgot your password?

    Login / Register



    Page 3 of 20 FirstFirst 1 2 3 4 5 6 7 8 13 ... LastLast
    Results 41 to 60 of 388
    1. #41
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Quote Originally Posted by SSLance View Post
      I'm questioning to myself if the changes I made to the rear suspension had an effect on the front geometry, or if the driving of the car in several autox events last fall created some bushing deflection...or if it was just the alignment rack readings off just a bit to cause the slightly different readings when no changes were made up front mechanically?

      It sure looks like something changed in the left front between the two alignments? Could possibly different amounts of gas in the tank have an effect on how the rear end sat and that cause the changes in the front readings?
      The front reading variations ...between times on the test equipment ... are pretty normal & occur with variables in how the test equipment is installed on the car, minor wheel variations, etc. But you should be aware, settings can change from impacts, potholes, curbs & wear.

      The only thing here that might be different on the front, caused by changes in the rear, would be slight variations in caster if you changed the ride height of the rear, affecting the car's rake, and therefore affecting A-arm & spindle rake.



      I'm more concerned that something is out of square on the LR wheel. Your rear end housing is slightly bent up & forward, giving it camber & toe in.

      When we build trick floater rear ends, we will sometimes build in a little camber, but you would want it the same on both sides ... or otherwise ... the car will handle differently on left turns versus right turns.

      But the "toe in" of the LR wheel & tire isn't healthy. It isn't the end of the world, but down the road when you have some down time, I'd take the rear end to a chassis shop with a rear end jig & have them straighten the left tube.


      If anyone has any questions, feel free to chime in on this thread.

      Ron Sutton


    2. #42
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Hi Lance,

      I put come comments in blue, after your questions.



      Lot to digest there... I read it once, now I'm going back to read it again.

      Ron I think I remember the alignment shop guy telling me that my static camber was 1.5 degrees negative and with 15 degrees of steering input it went to 2.5 degrees negative after the alignment with the new arms. We did not get into dive though.
      That's good ... going the right direction ... but doing it "statically" at ride height only gives us part of the picture ... versus knowing what they are "dynamically" ... meaning in full suspension dive & with body roll at it's maximum. Static is helpful, just not complete.

      Not sure if you can tell anything by this but I'll pass it along as something I did after putting the DSE upper control arms on the car.

      http://youtu.be/i0haoUpFmPs
      OMG ... great, simple video ... and you can clearly see you changed the car from having camber loss (going positive) to having camber gain (going negative) with the DSE arms.


      http://youtu.be/XcvkHx8LXYM
      Another great, simple video ... and you can clearly see you helped reduce the camber ills while turning ... by increasing the caster ... with the DSE arms that relocate the upper ball joint back.

      Now ... you need to take this further, by adding more caster, to help correct the tire camber while "dynamically" in dive & turning.


      When I made those changes I wanted to record how those changes were different than the stock pieces and this was the best way I knew how, crude but a start.
      Love it.

      I appreciate your taking the time to lay all of that out above Ron. I've heard and read bits and pieces about front end geometry before and it is starting to sink in more and more, but the way you lay it out helps makes things even clearer.
      No worries. Glad to help.


      I have one question to ask, and not that it will make any difference to me in a real sense...but how will setting a front end up like you are describing above for optimum handling on an autocross course effect every day street driving? Will an alignment (or a complete front end setup) arranged for the best cornering be less than optimum for street driving both in tire wear and over all steering feel?
      For the most part, there are no negative results on the street. Improving or correcting camber, camber gain, caster, caster gain, roll centers, etc, all make the car drive better on the track & street.

      One difference "can be" the toe setting.

      Slight toe-in makes the car more stable at speed, but negatively affects steering response & cornering ability. Slight toe-out will make the car's steering response sharper, & improve cornering ability, but can make the car a bit "darty" at speed & will "wander" over rough surfaces.

      In short track racing, tight corners in road racing & AutoX ... the optimum set-up will have the tires "toed-out" slightly in dive, with the wheels turned. There are three ways to achieve this.

      1. Static toe-out
      2. Built in Ackerman (or increased Ackerman)
      3. Built in "bump out" when the car's suspension compresses "in dive"

      I have done it all three ways & each has it pros & cons. If you set your car to have static toe out of 1/8" ... with no Ackerman & no bump out ... it will corner awesome, but cause excessive tire wear in everyday driving. It can "wander" on uneven roads & be a little darty.

      If you set the car to have zero (0) toe (straight up, not toed out nor in) ... and have the bump steer dialed in to be zero throughout the usable suspension travel ... and build in enough Ackerman to achieve the same toe out of 1/8" "dynamically" in dive, while turning ... it will corner awesome (even better than static toe-out, but the difference is marginal) ... and the car will not have excessive tire wear in everyday driving. It "can" still "wander" & be a little "darty" ... but minor, & for sure less than with 1/8" toe out.

      If you set the car to a small amount of toe in (1/16" total) ... and have the bump steer dialed in to provide "some" bump-out as the car's suspension compresses in dive ... and build in enough Ackerman ... so the ackerman & bump-out COMBINE to achieve the same toe out of 1/8" "dynamically" in dive, while turning ... it will corner awesome. The car will not have excessive tire wear in everyday driving ... AND ... it won't "wander" or be "darty."

      --------------------------------------------------------------------

      This section is an Edit/add-on.

      I want to add something to my answer about your question, "how will setting a front end up like you are describing above for optimum handling on an autocross course effect every day street driving?"

      I left something out. When you optimize the front suspension geometry ... meaning KPI/SAI, caster, caster gain & camber gain ... you do NOT need to run as much STATIC Camber ... which is a benefit to tire wear on the street.

      --------------------------------------------------------------------





      Now, back to reading again... :D
      I understand. There is a lot to digest here.



      If anyone has any questions, feel free to chime in on this thread.

      Ron Sutton

    3. #43
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Quote Originally Posted by SSLance View Post
      That actually might be easy to try as my DSE arms came with slugs that fit into where the arm bolts to the frame. I believe I can pull the nuts, work the slugs out and put the new slugs in which should give me another 1.5 degrees of caster if I remember right?
      That would be a good, easy, no-cost improvement. Adding 1.5 degrees to the 5.6/5.7 you currently have will put you a smidge over 7 degrees. Anytime you can reduce the KPI/Caster split, the tires contact patches will improve.

      You will need to reset the toe. And this WILL effect bump steer.

      Has your car had the bumpsteer corrected? Regardless, bumpsteer should be one of the things we work on, after you get the rest of the front suspension geometry optimized.

      Regardless, add the caster & set the toe-out to 1/8" (only for now) ... then go run it at the AutoX & see how it performs. I'm confident it will corner better for you. When you feel the result & see the lap time gain, our next step will be to get the caster more than the KPI/SAI and really cut the tight corners!




      If anyone has any questions, feel free to chime in on this thread.

      Ron Sutton

    4. #44
      Join Date
      Aug 2012
      Location
      Peoria, AZ
      Posts
      1,730
      Country Flag: United States
      The bumpsteer never has been real bad with this car and got much better with the addition of the DSE arms. It is real nice to drive down the highway now as it sits.

      I believe the only issue I will run into adding the extra caster might possibly be a rubbing issue on the back of the fender wells, won't really know until we try it though and it won't be the first time these have been touched by the tire.

      I don't mind putting it on the alignment rack once again and I have until June 30th before the next AutoX event. My new front street tires came in today and hopefully I'll have them on the car by tomorrow. What I think I'll do is try to get the slugs in the arms maybe this weekend and then take it back to the alignment shop next week and go ahead and work to get the caster more than the KPI/SAI and the toe set all in one shot.

      While it is on the alignment rack, can we maybe put a rachet strap on the K member and pull the front of the car down compressing the suspension to check the camber gain? I'm all about combining projects to gather as much information as I can at a time. The shop I go to is full of racers and charges by the hour and doesn't mind me helping while the car is on the rack.
      Lance
      1985 Monte Carlo SS Street Car

    5. #45
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Quote Originally Posted by SSLance View Post
      I'm curious what option I have in this regard if you are aware of any.

      I am in the process of trying to upgrade my front brake package right now which is most likely going to mean modifications to my existing spindles. If there was a better option KPI/SAI wise that would also allow me to do a brake upgrade that might make pretty good sense right now.
      Lance,

      There are a ton of spindle options ... way more than most people know. I think of them in 4 categories:

      1. Factory spindles from another application.
      2. Off-the-shelf aftermarket spindles, typically with lowering built-in
      3. Off-the-shelf racing spindles, in standard & lowered heights
      4. Custom spindles

      There are several factors to take into account in spindle design:
      a. Overall height & the individual distances from the spindle pin to the top & bottom ball joint mounting surfaces. (which is how lowering spindles are achieved)
      b. KPI/SAI (King Pin Inclination or Steering Angle Inclination, depending on the term you're familiar with.)
      c. The ball joint tapers & sizes ... but there are relatively easy to change & I don't let this prevent me from picking a spindle I want.
      d. Steering arm length ... way more important they many realize.
      e. Steering arm height ... as it affects wheel/tire clearance & what's required to get bumpsteer correct.
      f. Amount of Ackerman built into the steering arm.
      g. The actual spindle pin diameter & length ... affect strength & therefore spindle deflection ... critical in dive on hard, fast corners.
      h. What bearings it uses ... affecting strength, load capacity & therefore high speed cornering safety.
      i. What hubs it uses ... affecting weight, strength, wheel fitment, brake rotor placement, etc.
      j. What brake calipers fit & how.
      k. Weight ... its unsprung ... so it matters more. But it's not "rotating" ... so not as critical as wheels, tires & brake rotors.

      Soooo ... yeah ... there are a lot of variables & spindle options.

      When I'm designing a front suspension for a specific class with rules on what spindle we can run, I pick the best spindle available under the rules and design everything else to either fix or compliment that spindle. Factory spindles usually have a lot of KPI/SAI. When I have to run a factory spindle, like yours, around 8.75 degrees of KPI/SAI ... I know I'm going to end up with 10 degrees of caster ... or more.


      Remember the KPI/Caster Split concept ... if the caster is slightly greater than the KPI, the outside wheel is going to gain camber as the steering is turned, creating a flatter, better tire contact patch. The inside wheel also gets cambered the correct direction (for the inside wheel) and both front tires have more grip, better turning & higher corner speeds.

      I designed & raced NASCAR modifieds with 8.75 KPI & 10-10.5 degrees of caster with awesome results. We had a crew chief go off the range with set-ups & try 6-7 degrees of caster, but the cars always pushed in mid corner ... and snapped loose on exit. He was used to running less caster, but didn't take into account the KPI/SAI of the spindles we had to run.

      The whole combination of KPI/SAI, caster, caster gain, camber, camber gain, Ackerman, toe, steering ratio, etc. ... ALL have to be designed together for optimum cornering performance. All of them are important, but the KPI/Caster split is critical.

      When I'm designing a front suspension with no rules on what spindle we can run, I design the spindles & have them built. Then I'm not trying to fix anything

      ... and everything else in the front suspension can be designed to compliment that spindle. For a road racing car, I designed the spindle with 3 degrees of KPI/SAI ... and designed the rest of the the front suspension around what is called a "zero scrub" set-up ... & we ended up with 4.0 degrees of caster for optimum handling. This car did not require a high caster number, because the spindle KPI was lower. What is optimum for tight cornering is having the KPI/Caster Split slightly favoring the Caster.

      Another successful car I designed with 5 degrees of KPI/SAI ... ended up with optimum handling with 6.5-7.0 degrees of caster ... depending on the track. Again, the key was the KPI/Caster Split slightly favoring the Caster.

      This higher amount of caster seems odd to most mechanics & street car guys, but when you look at the newer Corvettes you'll see they run a lot more caster than what most think of as "typical" in the 1.5-3 degree range. The Factory GM specs for the C6 ZR1 is 7.7+ degrees of caster, with a 9.15 degree KPI spindle. The KPI/Caster Split is LOW, but still slightly favoring the KPI by 1.45 degrees. But owners that compete & win in the C6's increase the caster to 9.5-10.5 degrees of caster ... with the KPI/Caster Split slightly favoring the Caster.

      The common thread is we are almost always running more caster than KPI/SAI ... if we can. We run smaller KPI/SAI where we can too ... but it requires running wheels with more back spacing to get the scrub radius low (or sometimes zero). So simply ordering a spindle with smaller KPI/SAI is not a bolt-on solution.



      ...


      ...


      ...

      Yeah I know ... lots of information & no answer on what spindle you should run. The answer .... for now ... is it depends on your goals, plans & budget. We can make the suspension work better without changing spindles. But, if upgrading your spindles make sense for your goals, plans & budget ... Here is what I think ...

      a. For your specific car & application ... stay with a KPI/SAI around 7-8.75 degrees ... or the scrub radius will get ugly.
      ** Less KPI/SAI would require different wheels with more backspacing & longer upper & lower A-arms for a good scrub radius. That is how I would build an Road Race & AutoX killer ... BUT, if I understand your goals & car usage ... that doesn't fit. Stick with 7-8.75 KPI/SAI.

      b. A taller spindle ... combined with the the right height BJs ... would allow you to improve the roll center location & improve camber gain ... and then use spring adjusters to keep the car at the height you desire. Of course where it is taller ... and the dimensions from spindle to BJ pads ... are critical.

      c. You could go with a lowering spindle ... ONLY if you want to lower the car. But you'll need to lower the rear too. Or utilize a std height lowering spindle ... which moves both ball joint pads down ... and run a long upper BJ ... creating in effect a taller spindle ... improving the roll center location & camber gain ... and use spring adjusters to keep the car at the height you desire.

      d. A shorter steering arm would be beneficial. It would quicken up the steering without having to buy a new steering box.

      e. You need Ackerman for your application, so exclude any non-ackerman spindles.

      f. You are getting significant spindle deflection, so if you could get a bigger spindle pin, that would be beneficial.

      g. Getting larger bearings ... especially on the outer hub bearing ... would improve both performance & safety.

      h. You need a spindle that will allow 11.75-12.19" rotors. You can go with bigger rotors, but I wouldn't for your AutoX & street application. Just get the correct M/C, calipers & pads ... along with quality, curved vane rotors ... and you'll have all the braking force you need ... all the braking force your tires can handle ... without adding unnecessary rotating weight.


      Hmmm. I'll need to do some research, compare available spindles & see what fits this criteria best. I'll get back to you tomorrow.


      If anyone has any questions, feel free to chime in on this thread.

      Ron Sutton

    6. #46
      Join Date
      Aug 2012
      Location
      Peoria, AZ
      Posts
      1,730
      Country Flag: United States
      So swapping out the plugs on the A arms to gain caster won't work, I've already got the offset plugs in the passenger side. I'd forgot we did that during the first alignment.

      Here is the current shim stack on the Passenger side




      Here is the current shim stack on the driver's side





      And I did get my BFG Rivals put on the front this evening and was able to take the car out for a cruise on the street...first time in over a month. Man I like driving this car.


      Lance
      1985 Monte Carlo SS Street Car

    7. #47
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      I see that now after watching the video again, things look pretty decent and the car is sticking into the corner then with the extra bit of steering input for the sharpest part of the corner it all goes to hell.
      Yup! Sure does. Glad you can see it now too.

      You can really tell when it happens by watching the tire roll under the rim.
      Correct. The initial "tightness" you feel in the steering wheel before it breaks into a push indicates the tires have gripped at their limit & the front end of the car is at it's maximum roll angle ... which COMPOUNDS the problem. If your car is rolled over 2.5 degrees ... that is 2.5 degrees of camber lean the wrong direction.

      When the KPI/SAI being greater than the caster ... more steering input makes outside tire & wheel LEAN OUT at the top, known as losing camber (technically called going positive). My rough calcs say it is probably at 2.7+ degrees (at 20 degrees of steering input) ... the wrong way. Not only does the tire "roll under" ... but the contact patch narrows immediately ... and a lot. Probably going from 8" of tire contact patch to 5-6" ... maybe less.

      If you were at the limits of tire adhesion ... with 8" of contact patch ... and that shrinks to 5-6" (25% less tire) ... at speed, under maximum load, in the corner ... well ... the front tires immediately break traction and the car goes into a push/understeer condition.


      It doesn't look like the ride height is changing much at this point, so am I correct in assuming the KPI has more to do with causing this than camber loss because of suspension compression?
      You are correct again. More KPI/SAI than Caster is the cause, not more body roll.

      Here's why it happens.

      Before the car breaks into a push ... the tires were gripping at their absolute limit ... therefore the front end of the car is at it's maximum roll angle ... MEANING the outside front spring is loaded as HARD as it is going to be. The spring is at maximum compression for that corner.

      Then, as you give it more steering input ... and more KPI/SAI than caster causes the tires contact patches to shrink ... causing the tires to break traction & push. The car does not roll over any further. It can't ... it just lost traction. No traction = no body roll.

      The outside corner will actually start to come up a little & the car will flatten out a little ... meaning the chassis/body roll actually reduces ... but only a small amount, say fraction of a degree ... until you unwind the steering wheel to exit the corner.



      And does the camber gain on the inside tire happen at the same point that the camber loss on the outside tire happens?
      Yes. So you're losing contact patch on the inside tire too.

      I like to think of it this way ... there is no way a car driven at the true limits of tire adhesion ... with 16" of contact patch (both front tires) ... suddenly shrinking to 10-12" (again, both tires) ... at speed, under maximum load, in the corner ... can hold. The front tires are going to break traction to some degree and the car goes into a push/understeer condition.

      -------------------------------------------------------------

      And then ... (sounds like a camp fire story)

      When the front tires do regain traction, the outside front corner dips again, unloading the inside rear tire ... causing it to lose a degree of grip ... and you get the loose condition on exit.

      As you can tell, push/understeer conditions are the worst thing for competition cars. I hate them, so I've spent my racing career understanding causes & cures.

      The good news is your car is already WAY better than it was stock. With the changes you already made, you have made big steps at improving the handling. The even better news will come when you get the suspension fully optimized, and cure the small ills it has now. Better lap times & more fun at the track will be our result.


      **back to reading**

      Me too. I have more of your questions & comments to read ... plus some spindle research to do.

    8. #48
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Hi Lance,

      Quote Originally Posted by SSLance View Post
      The bumpsteer never has been real bad with this car and got much better with the addition of the DSE arms. It is real nice to drive down the highway now as it sits.

      I believe the only issue I will run into adding the extra caster might possibly be a rubbing issue on the back of the fender wells, won't really know until we try it though and it won't be the first time these have been touched by the tire.

      I don't mind putting it on the alignment rack once again and I have until June 30th before the next AutoX event. My new front street tires came in today and hopefully I'll have them on the car by tomorrow. What I think I'll do is try to get the slugs in the arms maybe this weekend and then take it back to the alignment shop next week and go ahead and work to get the caster more than the KPI/SAI and the toe set all in one shot.

      While it is on the alignment rack, can we maybe put a rachet strap on the K member and pull the front of the car down compressing the suspension to check the camber gain? I'm all about combining projects to gather as much information as I can at a time. The shop I go to is full of racers and charges by the hour and doesn't mind me helping while the car is on the rack.
      A few things ...

      1. I don't think you can get all the caster you need with your existing upper A-arms. I suspect the slugs in the upper A-arms will only allow you to come back a degree or so. To get more caster with the Upper A-arms, you will need different upper A-arms, with the upper ball joint moved back more than the DSE arms you have ... or you need different lower A-arms that move the lower ball joint forward. DSE makes Lower A-arms for your car that move the ball joint forward to add another 2-3 degrees of caster. That is the route I suggest. So there is a cost, and time.

      2. As you lay the spindle back more, you're going to change the bumpsteer more. Your car hasn't been properly "bumpsteered" yet anyway (racer term for working out the bump steer on both side to achieve either zero bumpsteer, or a predetermined amount of "bump out" depending on your handling goals & preferred strategy). This requires specific small parts & takes AWHILE to dial it in perfectly. I'd hate to see you do it over & over every time you make a change, so I suggest you do it once, after we work out your front suspension package.

      3. You're mentioned a brake upgrade & we discussed potentially changing spindles too. Could be some advantages, with a better designed spindle, as we discussed in another post. I suggest we weigh these out & decide the total package, and do it once ... and then dial in the bumpsteer.

      4. We REALLY need to map out your front suspension geometry, which will tell us your current A-arm Instant Centers, Camber Gain, Scrub Radius, and both Static & Dynamic Roll Center locations. You will need to do all the measuring & get me the #'s ... and I'll enter them into the geometry program.

      5. THEN ... with the DSE lower A-Arms (for sure) ... "probably" some different height ball joints ... and "maybe" a different spindle (or not) ... all to optimize your caster, KPI/SAI, Camber, Camber Gain & Roll Centers ... and we'll be able to pull your car's front geometry together for race car like handling on the AutoX course.


      Cost estimations:

      DSE Lower Control Arms $700
      Special Height Howe Ball joints $150-300
      Custom Spindles $500
      Bumpsteer parts $120
      Spring Adjusters $80

      Digest that & we'll talk more next week.

    9. #49
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Quote Originally Posted by SSLance View Post
      So swapping out the plugs on the A arms to gain caster won't work, I've already got the offset plugs in the passenger side. I'd forgot we did that during the first alignment.
      I see. So we won't be able to get much more out of the upper A-arm. But if we can get .4 of a degree with the uppers ... and with the DSE lowers, we can get another 2-3 degrees ... to add to your current 5.6 ... you'll end up in the 8-9 degree range. That will be "closer" to optimum with your current spindles. If we change to spindles with 7.5 degrees of KPI/SAI & get 8.5-9.0 degrees of caster, that will be real good.

      If we dial in the right amount of camber gain, caster gain & Ackerman, then bump steer it ... you'll be golden.

      I want to work out the scrub radius before I can confidently suggest spindles with less KPI/SAI. So getting the suspension pivot measurement numbers should be your next project before we try to lock down parts or specs.

    10. #50
      Join Date
      Aug 2012
      Location
      Peoria, AZ
      Posts
      1,730
      Country Flag: United States
      For some early Sunday morning reading, I went back and re-read everything Ron has discussed in this thread. As I'm getting a better handle on the terminology and the thought process behind suspension geometry, more and more is sinking in when I re-read his posts.


      Quote Originally Posted by Ron Sutton View Post

      4. We REALLY need to map out your front suspension geometry, which will tell us your current A-arm Instant Centers, Camber Gain, Scrub Radius, and both Static & Dynamic Roll Center locations. You will need to do all the measuring & get me the #'s ... and I'll enter them into the geometry program.

      [/B]

      Ron, I'll be happy to do what I can here on this but I need a bit of direction from you on exactly how to measure and map out my suspension geometry to give you the information you need to see the whole picture.
      Lance
      1985 Monte Carlo SS Street Car

    11. #51
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Excellent. Tomorrow, I'll put together instructions & tips for you to measure all of the pivot points in your front suspension, track width, sway bar, shock & spring points in three dimensions.


      You’ll provide me the measurements & I will input them into one of my suspension software packages & we’ll get clear on your CURRENT …
      A-arm Instant Centers
      Static Roll Center location
      Dynamic Roll Center location*
      Scrub radius
      Camber Gain per inch
      Dynamic Camber in dive & roll*
      Spring Motion Ratio
      Actual spring rate at the wheel
      Sway Bar Motion Ratio
      True rate of your Sway Bar
      Shock Motion Ratio
      Shock Valving rate at the wheel**

      From there, we’ll be able to make informed decisions on A-arms, ball joints, spindles, etc … to achieve optimum geometry for your goals. So we can dial in the whole list above to the optimum settings (within physical possibilities).

      I will show you how the information can guide us on part & tuning decisions, after we lay it out, along with what all the info means. If there are Engineers following this post, you’re going to dislike some of my terms. I apologize in advance. Sometimes I use the engineering term. Other times I use what I call “car guy” terms.


      Notes from above:

      * We can only do these after we know your shock travel on course. So for your next AutoX event (June 30th ?) you will want to use lowbuck shock measurement data acquisition devices ... known as rubber O-rings or zip ties (tied real tight) on all 4 shock shafts, pushed up against the shock body. As you run the course, each shock will travel & therefore move the rubber o-rings or zip ties down the shaft.

      After each run & definitely before the next run ... measure & record your shock travels & the run # ... then push the o-ring/zip tie back up against the shock body. Do that for all of your runs & share the info with me online after the event. I'll show you how we use that info to determine a lot of key things.



      ** This would require dyno'ing your current shocks which I don't think is valuable, because they are close to worn out. But when you get new shocks, and we get a dyno sheet, we'll be able to use this info.

    12. #52
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Lance, I think I remember you’re leaving town for a few days. Take this & digest, so you can plan to do this sometime after you return. This takes time & patience.

      ----------------------------------------------------------------------

      In this post, I’ll lay out a method to measure all of the pivot points in your upper & lower A-arms … plus track width, sway bar, shock & spring points.

      There are hundreds of ways to doing most things. I’m laying out one way I think most car guys can do in their garage. You will need some basic tools & creative body language when it comes to getting into difficult spots.

      This method will take a little longer, but we will have accurate numbers … AND … as you make changes, you will need to take only a few measurements & we’ll still know where everything is.

      These dimensions are important, so taking your time, measuring several times & even measuring different ways will insure we have accurate numbers.

      ----------------------------------------------------------------------

      Tools:
      You will need a good tape measure. Use just one … so if the end isn’t dead zero perfectly accurate, at least all the measurements are the same. Every 1/16” matters.

      Tool check list or shopping list:
      Good, readable tape measure.
      4-6” dial or digital caliper.
      Short laser level (6-10”)
      String
      2 Bob weights.
      Chalk line (blue will come off your floor eventually. Red is not coming out … ever)
      Roll of quality string
      Removable masking tape (Blue 3M works best)
      Sharpie fine point marker(s)
      Brake Cleaner & paper towels
      Note pad & pens

      Sears has everything in one stop if you need something.

      Laser levels
      http://www.sears.com/shc/s/p_10153_12605_00948292000P
      http://www.harborfreight.com/2-in-1-...vel-67800.html

      ----------------------------------------------------------------------

      Pre-measure Ball Joints:
      If you have some spare upper & lower joints ... great. If not, make a stop at your local, friendly auto parts store where you buy parts. You’ll need to borrow an upper & lower ball joint to measure at the counter.

      Lance, you need a Moog K5208 for the upper & Moog K6145 for the lower. Unless your DSE upper A-arms have a special ball joint in them. Call DSE & find out “for sure” as this is CRITCAL.


      Name:  balljoint.jpg
Views: 2203
Size:  34.5 KB


      Name:  Lower_Control_Arm_Pivot_v2_pass_l.jpg
Views: 2174
Size:  69.8 KB


      Name:  Upper_balljoint_pivot_v2_final_pass_l.jpg
Views: 2302
Size:  88.0 KB


      Refer to the photos I’ve attached here. Take a ball joint & lean it all the way to the right & draw a Sharpie line on the housing … in line with the BJ pin. Now lean it left & do it again. Now straight up & do it. There is your true pivot center. Take your dial/digital calipers & measure from the pivot center to the top of the housing & again from the pivot center to the end of the stud.

      Do both ball joints & write down all the numbers. When you’re under the car, getting to the top off the housing or the end of the stud will be WAY easier to achieve. You just need to do the math … along with measuring … to arrive at the true pivot center locations on your car.

      What was the brake cleaner & paper towel for? To clean off your Sharpie marks on the ball joint housings.

      ----------------------------------------------------------------------

      Before you start:
      a. Plan for this to take half a day.
      b. You’ll need a helper to hold the other end of the tape and to “spot” for you.
      c. Work out how you’re going to put your weight in the seat. Don’t use a person. (We use lead)
      d. Put your AutoX tires on & set the tire pressures just like you compete with.
      e. Get the car as close to “race ready” as possible: fuel level, stuff out of (or in) the car, etc.
      f. CRITICAL: Document all numbers & details on paper, so we can refer back later.

      ----------------------------------------------------------------------

      Platform:
      The tires & suspension have to be “loaded” just like the car is on the ground. So you can not use a chassis lift or jack stands. You can use a drive on lift.

      The car needs to be on its tires, just like ride height, but you need to be able to get under it. We use 10” Joe’s Racing stands & simply add 10” to all of our height numbers.

      Name:  Joes_Racing_Products-10_Wheel_Stands-29600_1247.jpg
Views: 2043
Size:  9.5 KB

      You “may” be able to do this on the garage floor, but it is harder. Depending on ride height you may not be able to get under the car well, or at all. If you’re doing this on the floor, pick a spot as flat as possible with no dips.

      I’ve seen guys use car ramps & stands … shimmed so all 4 to the exact same height. I’ve seen guys with shops use muffler & oil change pits, where they can walk under the car. So give this some thought on where & how works best for you.

      If you rig something up to raise the car, all 4 stands need to be the EXACT same height. Any height will do, but they have to be the same. Whatever the number is, you will be subtracting it from your height numbers to get true numbers, as if the car was on the ground.

      ----------------------------------------------------------------------

      Pull the car into your “space” straight. Make sure the front wheels are “dead true straight” as you roll it in & do NOT turn the steering wheel once you’re in your spot. Back up & do it again if you need to.

      A simple way to check & confirm the front wheels are “dead true straight” … is to pull a long, taut string across rear tire & front tire on one side … at the same height (preferably axle centerline) … and pay attention to how it lays across the front tire. Do both sides.

      If the car is toed-in, the gap between the string & front sidewall, of the front tires, should be the same on both sides. If the car is toed-out, the gap between the string & rear sidewall, of the front tires, should be the same on both sides. If a gap is bigger on one side, the steering is not straight.

      You don’t want to have to turn the wheels … in their spot … and leave them, as there will be “tire bind” (unless you have some way of freely sliding one wheel). Get it true & back the car up 2’ & roll it into place again if you need to.

      ----------------------------------------------------------------------

      3 types of measurements.

      1. Height … from the ground up to the pivot point
      2. Left or right … always from the car centerline
      3. Forward or backwards … of the front axle spindle centerline.

      What you’re measuring … in order:
      a. Car ride height.
      b. Car centerline.
      c. Front axle centerline.
      d. All four ball joints ... at true center of their pivot.
      e. All 8 A-arm pivot centers (2 for each upper & lower A-arm).
      f. Shock pivot centers
      g. Spring end centers
      h. Sway bar attachment points to A-arms.
      i. Track width

      ----------------------------------------------------------------------

      Here is detail for each area of measurements.

      a. Car ride height.
      Pick a spot on the bottom of the frame rails that will be easy to measure now & in the future. The further apart you go, the more accurate. Most racers usually pick a spot in front of the rear tires & behind the front tires … if the frame rails are wide at that point & out near the rocker panel. Either pick a spot with identifying holes or marks on the bottom side of the frame rails … or make something to permanently mark these spots. You’ll use these for the life of the car, no matter what changes you make.

      ----------------------------------------------------------------------

      b. Car centerline.

      Before we start … “mark down” … means using either the laser or plumb bob & string … to put a mark on the floor exactly where a point is. Some people use the term “transfer” … meaning to transfer a point on the chassis or suspension onto the ground.

      I don’t like marking on my epoxy coated floors, so I put blue masking tape down first & write on it with the Sharpie marker.

      This measuring process is difficult & somewhat subjective. Pick a section of the frame that looks symmetrical … and either go inside or outside (but use the same on both sides of the car) & “mark down” … putting a dot or “x” on the floor. Do this in 3 spots, using 3 different sections of the front frame. Then, do this in the rear, using 3 sections of the rear frame.

      Name:  Chassis Top View with Marks.jpg
Views: 2223
Size:  119.6 KB


      Now find the center of those 6 frame sections, using tape & sharpie again.

      Next, with a friend’s help, pull your chalk line taut … down the center of the car … on the floor … and the string “should” hit all 6 frame section centers. If it doesn’t, either recheck your measurements and/or re-evaluate your choice of locations. Ultimately, you’re going to put a chalk line on the floor using the marks you trust.

      That is the car centerline that everything is going to be measured from & to.

      ----------------------------------------------------------------------

      c. Front axle centerline.

      A simple way to do this is to pull a taut string behind the front tires, on the floor, and mark the string location on both sides. Do the same in the front. Split the difference & that is the front axle centerline. Problems only occur with this method with different tires, different pressures, suspension or tire bind from not rolling it into place straight.

      Put a chalk line on the floor representing the front axle centerline. Many things, but not all, will need to be measured from & to this point.

      For all things in front of the front axle centerline, express them in negative or minus numbers. Example: if something is 2 & 3/8” in front of the front spindle centerline, write it down as -2 & 3/8”.

      Everything behind the front axle, express as positive numbers.


      ----------------------------------------------------------------------

      d. Locate all four ball joints ... at true center of their pivot.

      Since you have already pre-measured the ball joints, this part is not as tough as it would be if you were trying to find the pivot centers while measuring. Eyeballing these pivot centers ALWAYS leads to inaccurate data.

      Use your measurements from the top off the housing, or the end of the stud, to the axle centerline & work out the math. Double check by eyeballing to see if your math places the pivot center where it actually is.
      Your roll center locations & camber gain numbers will only be as accurate as your measurements. This is a time consuming & somewhat tedious operation. I always suggest people take the time to do it right the first time, so you don’t have to do it over (or suffer handling problems from incorrect tuning).

      You need to measure the location of each ball joint in 3 directions … all based on the true pivot point of that ball joint. You need the …
      1. Height … from the ground up to the pivot point
      2. Left or right … always from the car centerline
      3. Forward or backwards … of the front axle spindle centerline.


      Reminder: for all things in front of the front axle centerline, express them in negative or minus numbers. Example: if something is 2 & 3/8” in front of the front spindle centerline, write it down as -2 & 3/8”. Everything behind the front axle, express as positive numbers.


      I can’t stress this enough. Make sure your tape is both straight & a true 90 degrees to what you’re measuring. Having the tape measure angled any direction other than a true 90 degrees will produce incorrect numbers. This is hard to see when you’re holding the tape under the car in a tight spot.

      Use your friend as a “spotter” to insure your tape is straight up & down for height measurements on 2 planes ... and 90 degrees to the car centerline & level for right & left distance measurements.

      There are times when it is more accurate to …
      • Use a tape and measure directly.
      • Hang a plumb bob on a string off the point, or near it, and measure.

      Name:  Plumb_bob.jpg
Views: 2083
Size:  17.7 KB

      • Utilize the laser (and level) to point up or down & transfer the measurements.
      • Use the level to extend a point out to where you can use the tape measure.
      • You’ll just have to use your best judgment or try it different ways.

      I like to mark on tape on the floor … so I don’t forget (I’m old). I put “points” on the tape along with the measurement … so I can find the point again easily to re-measure if I want or need to … and so I can re-check my measurements.

      I check my numbers & recheck them several times. So when I capture them all … I KNOW THEY’RE RIGHT … and can trust the data & results.

      ----------------------------------------------------------------------

      e. All 8 A-arm pivot centers (2 for each upper & lower A-arm).


      You need to measure the location of all 8 A-arm pivots in 3 directions … all based on the true pivot point of the bushing. You need the …
      1. Height … from the ground up to the pivot point
      2. Left or right … always from the car centerline
      3. Forward or backwards … of the front axle spindle centerline.

      For the upper A-Arms … you can simply measure off the ends of the pivot shaft. For the lower A-arms, I need you to measure each bushing bolt … on both sides … and average the numbers.

      For example: If the center of the bolt at front of the driver side lower A-arm is 8-11/16” in the front of the bushing & 8-9/16” in the back of the bushing … you will average that to 8-5/8”. That is the height of that bushing.

      When measuring from the car centerline, the differences are bigger, because the lower A-arm is angled a lot. So, from car centerline, if the center of the bolt in front of the bushing is 10-1/16” & the center of the bolt on in the back of the same bushing is 10-7/16” … you will average that to 10-1/4”. That is the distance from the car centerline to the centerline of that bushing.

      If this same bushing is 1-1/2” ahead of the axle centerline on one side & 1-7/8” ahead of the axle centerline on the other side … you will average that to 1-11/16” … and because it is AHEAD of the front axle centerline, you need to express it as a negative, so write it as -1-11/16”

      We need all 3 dimensions on all 4 bushings.

      ----------------------------------------------------------------------

      f. Shock pivot centers

      The process should be getting simpler by now. You’re measuring to find shock pivot point centers. We need all 3 dimensions on all 4 front shock bushings.

      ----------------------------------------------------------------------

      g. Spring end centers

      A little tricky to measure … but we need measurements from the center of the spring top … to the front axle centerline & car centerline … and the height.

      We need the same thing for the bottom of the spring … and for both front springs.

      ** Anyone who is following along with us
      … if you have coil-overs … all you need to do is locate the shock pivot centers, as the spring does whatever the shock does.

      ----------------------------------------------------------------------

      h. Sway bar attachment points to A-arms.

      I saved the simple stuff for the last two. We do not need measurements for height or distance to front axle centerline.

      For this part, all we need are accurate measurements from the center of the car to the center if the connection points on the A-arm.

      ** Anyone following along with us, if your sway bar has linkages that mount off the side of the sway bar arm … you want to measure to the center of the connection points on the A-arm … NOT the center of the sway bar arm.

      Sway bar arm length matters to calculate your actual sway bar rate. So now is a good time to measure & record it. Measure from center of main sway bar to center of pivot on sway bar arm … 90 degrees from the main sway bar … regardless of angle or shape of the arm.

      ----------------------------------------------------------------------

      i. Track width

      Just for clarification … “tread width” is outside to outside of the tread. “Track width” is center to center. A lot of people get those confused & our conversations get sidelined.

      We need to know the track width … the true center to center of the front tire contact patches. Several options, but here is a quickie.

      On the front side of the tires … measure from the outside of the tread width on one tire … across to the inside tread width on the other side. Do the same on the back side of the front tires … and average the two numbers … to account for any toe in or out.

      If you get 55-1/2 in the front & 55-3/8” in the rear, average that to 55-7/16”.

      ----------------------------------------------------------------------

      Tips:
      • Remember to subtract the distance you raised the car up from ride height for all height measurements.
      • Reminder: for all things in front of the front axle centerline, express them in negative or minus numbers. Example: if something is 2 & 3/8” in front of the front spindle centerline, write it down as - 2 & 3/8”. Everything behind the front axle, express as positive numbers.
      • Your roll center locations & camber gain numbers will only be as accurate as your measurements & small #’s make a big difference. I measure everything I can on my cars with a digital caliper to the thousandth. It is that important.
      • Take your time & be precise. Don’t just “eyeball it.”
      • Getting true measurements is difficult. Experiment & be creative with measuring methods, but be accurate.
      • This a time consuming & somewhat tedious operation. I always suggest people take the time to do it right the first time, so you don’t have to do it over (or suffer from incorrect tuning).
      • Because you got frame heights on 4 corners of the car, you will be able to make many adjustments to the car, and know what changed & where you are, by rechecking frame heights.
      • For example, if you lower the whole car ½” … all of your frame mounted pivots just went down ½” … and your ball joints did not. That is easy to change in the roll center programs & know what your geometry is then.


      When you have the numbers, post them here on the Forum in an order that matches the numbers in this photo. After I enter them all, I’ll run calcs & post the graph.

      Name:  Blank-Front-End-Worksheet.jpg
Views: 2669
Size:  247.5 KB



      We won’t be able to determine true roll angle or dive numbers until you get shock travel measurements from your June 30th AutoX event.

      --------------------------------------------------------------------------


      If anyone has any questions, feel free to chime in on this thread.


      Ron Sutton
      Last edited by parsonsj; 06-17-2013 at 06:49 PM.

    13. #53
      Join Date
      Aug 2012
      Location
      Peoria, AZ
      Posts
      1,730
      Country Flag: United States
      Oh my...

      I have access to a drive-on lift at my office, so that will alleviate at least one of the more difficult parts of what I've read above.

      Now I need to read it all again to try to absorb even more of it.

      It does sound like a half day project at least, but not undoable at all.

      Thanks Ron...I'll get started gathering things up.
      Lance
      1985 Monte Carlo SS Street Car

    14. #54
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      LOL ...

      Lance, work at your pace. I'm just here to help.

      ------------------------------------------------------------------

      On another note, I have been doing some spindle research for you. I found spindles that achieve a slightly lower KPI & shorter steering arms, but overall they are too short for optimum geometry & big brake options are limited.

      I found spindles that have the same KPI, are taller, use bigger bearings with a stronger spindle, offer better brake options, but are too long above the spindle & too short below it.

      Lastly, I spec'ed out some custom spindles that do it all, but cost $600 with bearings, but will require a hub/rotor change. If you're upgrading brakes, it may justify the expense. Once we map out your front suspension geometry, I can better advise you if they'll be worth it or not.

      A few advantages to think about for now are:
      * Much quicker steering, without buying a new steering box.
      * Bigger spindle pin & bearings ... safer, less camber deflection under load.
      * 12" x 1-1/4" wide, combination rotor & hubs available drilled & grooved around $125 each.
      * Easier to get the caster above the KPI.

      Let me know if you have questions on measuring suspension points.


      Ron Sutton

    15. #55
      Join Date
      Aug 2012
      Location
      Peoria, AZ
      Posts
      1,730
      Country Flag: United States
      After re-reading the above and thinking about how I'm going to do this, I do not think using a drive on lift is going to help. Sure it's the best way to get all four tires level and gain access to under the car, but I can't see how I can get accurate measurements to the floor with the lift ramps in the way?

      I think I'm going to make a set of these.



      and use a laser level to make sure I get them all exactly level and square on my slightly sloped shop floor and use my two post lift to set the car on them before starting the measuring process. My only other obstacle that I can think of right now is the linear floor drain that runs right down the center between the posts of my lift. I guess I can set my car up to one side or the other of it so the snapped center line has a clear surface to be on.

      I also have to figure out a way to get the front tires to relax to a normal position once setting on the stands as it'll be hard to roll it back and forth once on them.

      Ideas? I can NOT get under my car as it sits at ride height, heck it's hard enough to just get a floor jack under it to raise it up.
      Lance
      1985 Monte Carlo SS Street Car

    16. #56
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      After re-reading the above and thinking about how I'm going to do this, I do not think using a drive on lift is going to help. Sure it's the best way to get all four tires level and gain access to under the car, but I can't see how I can get accurate measurements to the floor with the lift ramps in the way?

      You can use a drive on lift. I have seen it used successfully many times & it is the easiest by far. In this scenario, you don't measure to the shop floor ... you measure to the lift "floor." Take a long string with bob weights on each end (or simply heavy bolts) and lay them across each ramp. That string line is a VERY good measuring point and can be easily moved to take measurements "almost" anywhere.

      With this method, you are still putting all 6 of your frame measurements on the lift ramps, but then you run a long string (instead of a chalk line) & it hangs over the ends of the lift. Once you have the string at the car's true center, mark the ends of the lift where the string goes (just in case it moves). Use bob weights or heavy bolts to keep tension on it & tape it in place (duct tape here).

      Name:  Lift-with-strings-&-Tube.jpg
Views: 2177
Size:  96.8 KB

      Now you have a string running down the centerline of the car at ground level. Most old school chassis builders prefer this method. You can take your strings & weights that run overs the sides of the lift ramp runners & move them "almost" anywhere to get a measurement.

      This method also works well with a laser lever set (level) on the ramp runners & pointed where ever you need a line. You just need to take the distance of the laser above the ramp runner into your math.

      Another method for measuring a lot of the front suspension points that are near the front axle CL, is cutting a piece of STRAIGHT, square tubing (or angle) slightly shorter than the distance BETWEEN your front tires. You simply lay it on the ramp runners & move it anywhere you want to measure something ... running your tape to the bottom of it ... which is your floor.


      I think I'm going to make a set of these.



      and use a laser level to make sure I get them all exactly level and square on my slightly sloped shop floor and use my two post lift to set the car on them before starting the measuring process. My only other obstacle that I can think of right now is the linear floor drain that runs right down the center between the posts of my lift. I guess I can set my car up to one side or the other of it so the snapped center line has a clear surface to be on.

      I also have to figure out a way to get the front tires to relax to a normal position once setting on the stands as it'll be hard to roll it back and forth once on them.

      Ideas? I can NOT get under my car as it sits at ride height, heck it's hard enough to just get a floor jack under it to raise it up.

      These wheel stands will work too. But not as easy or accurate as the drive on lift ... because the floor ... your real floor is not as straight as a a string. Having the drain in the middle sounds concerning, but you know it best. If you don't think the floor is flat & straight enough, I'd pick another option. If the floor is flat enough, of course it will work. But I still prefer the drive on lift.



      If anyone has any questions, feel free to chime in on this thread.

      Ron Sutton

    17. #57
      Join Date
      Aug 2012
      Location
      Peoria, AZ
      Posts
      1,730
      Country Flag: United States
      Drive on lift it is then...I can make that work.

      Is it crucial for the lift itself to be exactly level?
      Lance
      1985 Monte Carlo SS Street Car

    18. #58
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      No, it's not crucial for the lift to be exactly level. If the "floor" tilts more than 2-3 degrees, it may start to affect things, as the car will lean. Otherwise, you're just measuring height from "floor" to pivot points.

      One tip though, and we do this when we are out at the track & can not make something level ... if you use a digital angle finder/level ... and learn your "floor" of the lift is 0.7 degrees to one side ... take that into account when & if you use a level to measure anything ... and set it at the 0.7 degrees the same direction.


      If anyone has any questions, feel free to chime in on this thread.

      Ron Sutton

    19. #59
      Join Date
      Apr 2001
      Location
      Central CA USA
      Posts
      6,090
      Country Flag: United States
      Ron, Great info here. Thanks for the input in our forum. I'm sticking this thread to the top of the forum index.
      67 Camaro RS that will be faster than anything Mary owns.

    20. #60
      Join Date
      Nov 2012
      Location
      Sacramento, CA
      Posts
      1,918
      Country Flag: United States
      Thanks David.

      Take care.


      Ron Sutton

    Page 3 of 20 FirstFirst 1 2 3 4 5 6 7 8 13 ... LastLast