Question about alignment, or How bad would it be if ...?

[parsonsj]

I'd like to take my car to a local autocross tomorrow morning, and I spent the week trying to find a place to help get the suspension aligned. I wanted to get the corner weights and cross weights all sorted out, and then do a precision alignment.

So ... two local shops said they couldn't do it (car is too low, they say). Another local chassis builder claimed to be able to do it, but then blew me off all week.

Now it's Saturday, the autocross is tomorrow, and the best I can do is:
1. measure the wheelbase side to side (within 1/16" with my high precision tape measure, framing squares, and laser level).
2. measure the toe. It is also within 1/16" (using the same highly accurate tools, with bonus help from my 12 yr old daughter).
3. measure the camber. It is between -0.5 and -1.0 degrees using my precision analog angle finder.

The autoX is about 80 miles away or so.

Anybody got an informed opinion of the likelihood of tire damage? Think I'll be ok? Bad idea, stay home?

Any other thoughts?

thanks!

jp

[jeffandre]

I am no expert here, but I believe you can get it all close using the tools you mentioned. Precision may be off a tad but if you use a temp gun on the front tires and measure the inner, middle, and outer areas of the tire patch you can get a decent idea if you are overworking any areas of the tires. How much caster do you have?

Not sure how well the tires would heat up, but I would drive it on a local semi-twisty road to warm up the ties and start taking temp measurements. Then adjust the camber/caster a bit until you see relatively even warming of the tires. Try this on the freeway too.

Definitely find a local shop that will take care of your alignment when time there is no time pressure, and work it out where you can take it back once or twice for fine tuning depending on tire temps/wear. Good luck, and if you go to the autocross let us know how you did! Vids are even better!!!

[parsonsj]

Jeff,
I have no temp gauge. Sounds like something to pick up soon. Wonder if any of the other autoX'ers might have one.

Caster, I have no idea. Katz designed to 7 degrees, and I've put the cross-shafts in the middle of the adjustment range. Other than that, who knows?

jp

[slowcamaro]

Sounds like you'll be fine. I've been running -1.0 for a year and no noticeable odd wear. My friend ran -2.0+ daily on his last car and with tire pressures dialed in he didn't have any extreme wear either.

Toe is your biggest concern. Though 1/16th shouldn't kill you either. Especially on such a short trip. Now just get your tire pressures dialed in.

Caster doesn't affect tire wear so no real worries there.

I drove my car 40+ miles after eyeballing my front suspension rebuild. Didn't tear anything up on that drive.

Your close enough to have a little fun. Do it, and get video.

[Bow Tie 67]

John,

I think you'll be fine, and hope you did attend. Even if everything is not exactly where you want it you'll have a blast. Had you been able to get the alignment your tires will still take a beating, it's the nature of the beast.

Matt

[David Pozzi]

Sorry for the late reply, hope it worked out for you.
As long as you get the toe-in pretty close, you should be OK.
Get a smart level digital protractor at Sears and use that to measure camber, it's accurate to .1 deg.

Caster can be measured by turning the wheel in, taking a camber reading, then turning it out the same degrees and take another.
The trouble is measuring the turn angle precisely enough to have repeatability. Even with turntables it's not easy. Try some kind of protractor against the wheel.

Look here at the Smart Level tool, download the .pdf owners manual, there are charts to help you figure out caster angle.
http://www.smartracing.net/alignment.htm
David

[parsonsj]

Thanks for all the replies guys. I did go to the autoX ... in my Duramax. I'm glad I did, because I got lost going and coming home! Anyway, I met the club president and talked with the local alignment guru. The guy does lots of local racer setups, he's got a level pad, corner scales, etc. I'm going over there next week.

I hung out and watched as the locals put their cars through the paces. The course was *very* tight. Two U-turns, 2 complete circles, and a tough left-hander that was over 90 degrees. I don't know how well my pavement pounder would have done on such a course ... I'd guess the Mini Coopers would beat it!

Next action is the 2nd week of May.

jp

[silver69camaro]

John,
I always set up cars without a professional shop. If you're careful, you can get it VERY accurate. Heck, that's what we did for Art's '55 and '60 Vette, and those both did very well.

I use David's method for caster too. All I use to get up the car is a digial protractor, turntables, corner scales, and a tape measure. Works great for me.

[parsonsj]

All I use to get up the car is a digial protractor, turntables, corner scales, and a tape measure. Works great for me.

You forgot a level pad. Though even with no level pad, I agree, and I may get into that myself. The only tool that I own of those is a tape measure. Frank (ProdigyCustoms) and I have talked about splitting the cost of picking up a set, but we haven't done it yet.

Actually, that's how I expect the guy to do it when I get there. He's got a level pad and the ability to work underneath the car with it at ride height.

I'll let everyone know how it goes ...

jp

[chicane67]

So how'd the Duramax do thru the cones ... ?? ...

As David stated... if you get the toe nailed... you should be ok. For ever and a day, I ran -1.75 with +3.5 and 0.0625 to 0.125 toe out without any real adverse wear. I have heard that it takes about 500 miles of a funked-up alignment to set wear in a tire, with normal/non performance driving.

At home alignments are quite simple with an SLA or SA/Strut suspension. At Guldstrand... we used a 10+ year old Longacre bubble camber/caster guage, a pair of 12' 2x2 aluminum I beams, two tape measures, two clothes pins and four 4x4 blocks each about 12" long. I purchased the very same components for myself and have been using them ever since... and to think, the greater majority of those cars went 200+ MPH.

If that isnt scarry enough for you... we also used a bubble tire balancer (eg. static) that he has used since the late 60's... on those very same cars.

Longacre 78260 = 129.00
2x 12' I beam = local metal supply @ 35.00
2x 25' tapes = 25.00
2x clothes pins = You should be able to con the wife out of a pair for cheap
4' for 4x4 = I am sure you have this laying around the shop somewhere

With the 78260, you should be able to do a complete alignment, within 1/8 to an 1/4th of 1.0 degree, in about 20 minutes. For another $70.00... the digital 78290 unit will hold 0.1 degree with even more ease of use.

[Salt Racer]

John,

Just get the corner balance done properly, with you or simulated weight in the driver's seat.

Alignment isn't a black magic. I've been doing my own alignment for years using el-cheapo tape measures and a digital protractor - it's been good enough for 1:43 flat at Willow Springs big track in a stockish 134-hp BMW, and I didn't kill myself to boot. You won't feel a difference between backyard alignment and super-precise alignment unless your name is Michael Schumacher.

I wouldn't worry too much about tire wear. They are wear items when you do cone-dodging or track driving. It's an expensive hobby no matter how you approach. Funky wear pattern could also develop due to poor driving too, so consider the first set as throw away tires for learning. I'm not saying you are a bad driver, but you are unexperienced (as far as I know - otherwise, my apology).

The methods David and Tom described work just fine, and is the right way to do for home-brew alignment jobs. If you are not running inner fenders, you can also put a digital protractor against vertical surfaces on the knuckles or horiz surface on the steering arm to get pretty accurate caster measurement. Besides the ease of fabrication, that's why your knuckles have vertical surfaces.

For cone-dodging and tight road courses, start out with 1/8" toe-out, -2.2~2.5* camber and +7-ish caster as starting point. Once that's set, at this point, you should really concentrate more on getting comfortable with the car and improve your driving skills IMO.

Remember, a skilled welder can lay beautiful beads using a $300 flux-core wire feed machine while an $8000 equipment is only good for making abstruct art work "Wires sticking outta burnt hole" in the hands of Joe JBweld. Cars are no different - they can only be as good as the driver.

If you can't drive consistently, changes in setting won't mean much and only add confusion and variables. I'd limit the adjustment to tire pressure, and possibly anti-roll bar (only if the car has excessive under/oversteer to a point it won't respond well to throttle steer).

Have fun! Off to Pahrump NV for a track event.

[silver69camaro]

Good to see you on here, Katz.

[TheMonkey]

i didn't see that anyone mentioned it above... how much to turn the wheels when measuring for caster, and the multiplier for the difference.

if you turn the wheels 20* to the right, take your camber measurement, then 20* to the left, take your camber measurement. most likely, they will have opposite signs (one tipping in, one tipping out). so, if you have one measurement of 1.75* in, and the other is 1.25* out, then the difference is 3*. multiply that by 1.5 to find caster.

i think 20* turns multiplied by 1.5 is normal. this gets you very close. some people use bigger turn angles with a smaller multiplier, or smaller turn angles with a bigger multiplier, but offhand, i'm not sure what angles/multipliers work. it is not a straight line relationship. it is math that i cannot do, so i have to take the numbers at face value.

[parsonsj]

Katz!!!!

It's good to hear from you. You are right about the most important variable: the driver. Me, I've no real experience, other than some drag racing such a long time ago that it embarrasses me to say when it was.

I'm really looking for confirmation that the car is built square and level, and that the thrust angles from the back wheels are reasonable. I just want to be sure that I eliminate excuses when I get out there and lose to Mini Coopers on the autoX.

One thing the car does that I'd like to understand is that it tends to push right when I get on it. It especially happens when I shift gears, as if the unloading of the rear tires causes something goofy. Pre-loaded springs might cause it.

And actually, right now the rear housing is out of the car and it and the axles are being narrowed a half inch. The rear wheels were just too close to the sheetmetal during severe body roll. I'll have it back together in a couple of days. I noticed that one of the rear ARB bushings was loose when I pulled it apart. Maybe that caused the push.

My front bar is too big (according to your spreadsheet), because the swing arms ended up shorter to accommodate the radiator. I think it will push a bit ... but I'll know soon enough.

jp

[69Nova]

John where was the autox at? Let me know next time you want to go and I'll meet you there.

[parsonsj]

Andrew,

The autoX was at Lake County Tech Center. Just about an hour from my house, assuming I don't get lost again. The next one is in a couple weeks. I'll let you know.

jp

[69Nova]

Cool. Also if I was you I'd try and go to the next one at the gainsville roadcourse. I liked it alot. It was basicly a roadcourse with cones set up to keep speeds down. Lots of fun.

(the red is the course I ran)

[parsonsj]

Deal on Gainesville! That looks like fun. When is the next event? Is it SCCA? Or the Martin SCC?



jp

[Norm Peterson]

i think 20* turns multiplied by 1.5 is normal. this gets you very close. some people use bigger turn angles with a smaller multiplier, or smaller turn angles with a bigger multiplier, but offhand, i'm not sure what angles/multipliers work. it is not a straight line relationship. it is math that i cannot do, so i have to take the numbers at face value.

20° with a 1.5 multiplier is probably common partly because the commercially-available bubble type caster-camber gauges use that angle. But 14.5° and 2.0 works, as does 30° and 1.0 (if you can get that much steer angle).

It's not all that difficult or expensive to fab a fairly accurate caster-camber gauge that works off the wheel flanges (and uses a dial indicator). Careful choice of some dimensions makes it (almost) direct-reading.

Good to see you drop in, Katz. I was beginning to wonder if you'd fallen off the face of the earth.


Norm

[69Nova]

Deal on Gainesville! That looks like fun. When is the next event? Is it SCCA? Or the Martin SCC?

jp

I'm going to pm you some info right now.