Good Video showing a handling trait that is key to cornering

[Ron Sutton]

This is a good Youtube video, showing how the inside rear tire needs to "disengage ... to a degree" in race car cornering. The gentler the radius, the less it needs to disengage ... the tighter the radius, the more. You can learn a lot, just by watching the tires. Expand to to full scene & watch the inside rear tires of the cars in front of him. Freeze frame it if you need to see it better.

Plus, watching the blue & white #9 overdrive the car at end of the video is entertaining.

Watch: HERE (http://www.youtube.com/watch?feature=player_embedded&v=lwgFinrFOMY)

[rustomatic]

Analyzing pictures and performance of my Falcon in a recent autocross brought to mind a similar scenario. It looked like I was nearly three-wheeling in some corners; I didn't really know what to take from this, short of the following (at first):

1. This put me into a plowing situation, pushing the front of the car under braking (too late?). I'm blaming some of this on timing/bushing bind.

2. I first figured my tires just weren't sticky enough--I do not have race tires...

3. I started to think my front sway bar might be a bit too fat, but the pictures showed me a roll angle that did not make this appear as a reality.

I've made the following choices relative to my findings:

1. I'm rollerizing my upper control arms and spring perches--short of the sway bar mounts and tie rod ends, these are the only remaining pivot points in my front end that do not have bearings. This will make the action somewhat more predictable...

2. I'm still not putting on a rear sway bar (I have a Panhard bar that's currently at about axle tube height).

3. I'm putting on better shocks (Koni), so as to decrease compression stiffness on the front (KYB, anyone?) and increase rebound damping in the rear (keep the front corner from tipping in so quickly). My previous rear shocks were of low (Gabriel) quality, and were largely chosen to avoid skipping the rear through turns (as would happen with KYBs).

4. I considered going to softer coils in front, but again, the pictures kind of told me that my current 600-or-so pound springs are probably still decent.

5. I stupidly, finally realized that I hit the bump stops on my front end fairly quickly. The angle grinder should facilitate way more articulation, which will of course facilitate better contact with the loaded front wheel (maximizing the free component movement)...

7821878219

How much of that Porsche's rear wheel lift is attributable to the sway bar? Granted, I guess you don't want to do an IRS without one...

Cheers!

[Ron Sutton]

Can your crop the original top photo to zoom in on the RF tire & wheel & repost it ?

[MIKE67]

Ron, I always read threads you have contributed to. You obviously have a great deal of knowledge, but you don't always put it forward. You challenge us to think and may make statements that aren't obvious at first. I find that if you then get it, you really understand and can apply it to other situations. I am a little leery of getting into something with you and showing what I don't know.

But, here goes. Where did the quote "disengage ... to a degree" come from? Is this disengagement a requirement for "good" handling or is it a consequence/compromise of other choices/set-up decisions?

Thanks for your input on this forum.

[parsonsj]

Here's a question: what's the deal with the very early apex on the right hand 90 degree turn? Seems slow -- the camera car keeps catching up during the turn. Or is that a compromise to keep the car behind from out-braking them to the inside?

And another: is this lifting inner rear tire trait more of a rear engine car kind of deal?

[Ron Sutton]

Ron, I always read threads you have contributed to. You obviously have a great deal of knowledge, but you don't always put it forward. You challenge us to think and may make statements that aren't obvious at first. I find that if you then get it, you really understand and can apply it to other situations. I am a little leery of getting into something with you and showing what I don't know.

But, here goes. Where did the quote "disengage ... to a degree" come from? Is this disengagement a requirement for "good" handling or is it a consequence/compromise of other choices/set-up decisions?

Thanks for your input on this forum.

Hi Larry,

Thanks for chiming in. The term is mine, which is rare. Most of my terms came from mentors & associates over the years. "Disengage ... to a degree" means we are reducing the load & even reducing the contact patch on that inside rear tire.

This is critical to a good handling car on grippy tires & tight corners.

Your question: "Is it a consequence/compromise of other choices/set-up decisions?" ... has me struggling a little to correctly explain. Disengaging the inside rear tire to a degree ... is the intended goal. But I feel that the "best" suspension set-up ... is always the "best compromise or balance" of handling. Stated another way ... if all we cared about was optimum straight line acceleration, like drag racing ... we could achieve that ... but at the expense of our cornering performance.

If we were road racing, we still need the car to accelerate out of the corner & down the straight ... but the best set-up compromises some of that straight line performance for cornering ability. Obviously, if we can't get the car to turn well, we're not going to be fast

As I'm sure you've seen many times ... there are ALWAYS exceptions ... such as, it is NOT critical to disengage the inside rear tire to a degree if:
a. You can get the rear end to "glide" (think slight, controlled slide) around a tight corner (easier to do on hard tires).
b. The car has a complete open diff, like Formula Fords.
c. You're oval track racing & running staggered tires (outside rear tire a much larger diameter than the inside rear tire.)
d. The corners are not tight, but instead they are big sweeping corners.
e. The corner has significant banking.

"To a degree" means we are not lifting the tire off the ground completely. We may not even be close. It simply means we are reducing the load & the contact patch on that inside rear tire.

"To a degree" also implies ... correctly ... that we want to control how much. This is key. If we do not disengage the inside rear tire enough, we struggle with a tight/pushy car. If we disengage the inside rear tire too much, we now have a loose car to deal with.

How much is right? The answer depends on many factors. The video of the Porsches shows the "degree" to be quite high. That's why I posted it ... so it was clear to see. The "degree" the Porsches are disengaging the inside rear tire is correct for these cars, but they have the engine in the rear, so they have to disengage it more than an evenly balanced, or front heavy car.

The amount the Porsches are disengaging the inside rear tire in the video ... would be excessive for a typical P/T car with 51-55% front weight. But the concept is the same.

"Re-engage" means we want to "plant" the inside rear tire hard on corner exit ... to regain & achieve a full contact patch ... so we have 2 full tire's worth of contact patch for accelerating. This actually happens as the driver unwinds the steering wheel. "How much" is determined by suspension geometry, shocks, springs, etc.

Make sense?


Now I have a question for you. If your name is Larry, why is your user name Mike67? :poke:

[Ron Sutton]

Here's a question: what's the deal with the very early apex on the right hand 90 degree turn? Seems slow -- the camera car keeps catching up during the turn. Or is that a compromise to keep the car behind from out-braking them to the inside?

And another: is this lifting inner rear tire trait more of a rear engine car kind of deal?

Hi John,

I agree. It didn't make sense. I find less experienced drivers often get mad after being passed. It could be that he /she started making emotional/irrational decisions after he/she got passed for lifting too early into that corner a lap earlier.

A few times he/she had too early of an apex on 1 of the left hand turns too. It was clearly costing him/her time & positions. I guess that explains why he/she was a mid pack runner. If I was coaching him/her, I'd be suggesting late apexes on all the tight corners ... & use ALL of the track. Oh well. I only shared that video because it had great low camera footage of the rear tires on the cars in front of it.

To answer your 2nd question, "disengaging the inside rear tire ... to a degree" ... meaning we are reducing the load & even reducing the contact patch on that inside rear tire is critical to a good handling car on grippy tires & tight corners. I wrote out the exceptions & more detail in the post above.

The amount/degree the rear engined Porsches are disengaging the inside rear tire in the video ... would be excessive for a typical P/T car with 51-55% front weight. But the concept is the same.

[MIKE67]

Thanks for your answer Ron.

Now I have a question for you. If your name is Larry, why is your user name Mike67?

This was the first forum I ever registered for, so I used a made up name. Later I added my real name and haven't changed my user name yet:)

[Ron Sutton]

Okie Dokie. Thanks for clearing that mystery up. :)

Don't hesitate to ask questions or chime in on forum threads. That's how we all learn.

[parsonsj]

If I was coaching him/her, I'd be suggesting late apexes on all the tight corners ... & use ALL of the track.That's what I would have told them too, but I am only a humble HPDE warrior, not a racer. Thanks for the response.

[Rod]

Analyzing pictures and performance of my Falcon in a recent autocross brought to mind a similar scenario. It looked like I was nearly three-wheeling in some corners; I didn't really know what to take from this, short of the following (at first):

1. This put me into a plowing situation, pushing the front of the car under braking (too late?). I'm blaming some of this on timing/bushing bind.

2. I first figured my tires just weren't sticky enough--I do not have race tires...

3. I started to think my front sway bar might be a bit too fat, but the pictures showed me a roll angle that did not make this appear as a reality.

I've made the following choices relative to my findings:

1. I'm rollerizing my upper control arms and spring perches--short of the sway bar mounts and tie rod ends, these are the only remaining pivot points in my front end that do not have bearings. This will make the action somewhat more predictable...

2. I'm still not putting on a rear sway bar (I have a Panhard bar that's currently at about axle tube height).

3. I'm putting on better shocks (Koni), so as to decrease compression stiffness on the front (KYB, anyone?) and increase rebound damping in the rear (keep the front corner from tipping in so quickly). My previous rear shocks were of low (Gabriel) quality, and were largely chosen to avoid skipping the rear through turns (as would happen with KYBs).

4. I considered going to softer coils in front, but again, the pictures kind of told me that my current 600-or-so pound springs are probably still decent.

5. I stupidly, finally realized that I hit the bump stops on my front end fairly quickly. The angle grinder should facilitate way more articulation, which will of course facilitate better contact with the loaded front wheel (maximizing the free component movement)...

How much of that Porsche's rear wheel lift is attributable to the sway bar? Granted, I guess you don't want to do an IRS without one...

Cheers!

I don't want to high jack the thread, but racing at the goodguys event that you won we noticed that you're car was very soft and (for lack of better term) wallowy, perfect for that size track with the bumps, were many of our cars were set up stiffer I know that some of the guys went faster after softening up there cars for the track I personally removed all the low speed compression from my shocks and had only a little high speed to off set the drainage ditch, and I reduced the rebound to half of what I run to let my own car wallow more on the track I know that some disconnected front and rear sway bars to wallow there cars, on a faster higher speed track the softer, wallowy suspension will have to much roll at higher speeds and the car will be slow trying to recover from the weight transfer, just my opinion and observation

[Ron Sutton]

Rod,

I think you have Rustomatic confused with Craig510. It was Craig that won the SM AutoX class at GG.

I know ... all those Falcon guys look alike. :lol:


On a more serious note, that track, with the dips in the middle, was so rough ... I don't see how anyone with a tie down shock package (lot of rebound) could get around it without skipping the front end across the track. :eek:

I sure hope they don't continue running the track in that location. :fingersx:

.

[rustomatic]

Ron and Rod,

I'm always thankful for more input, and having my car confused with Craig's is not a bad thing. Rod has brought up an excellent point, in that many of us are kind of trained to think that the flat-turning (no body roll) car is one that handles well. For the average person on an average drive, this is a reasonable assumption, and I've fought with this mindset for a very long time. I'm only now coming to realize that short of a supercar chassis, which tends to have Forumula One engineering on board (a chassis nothing like a '60s muscle car), some body roll is not a bad thing. Many very fast vintage racing cars roll on purpose, as Walt Hane (Mustang/Shelby guru) openly advertises; the Maeco Motorsports Falcon that everyone loves (including me) does a very noticeable roll into the corners, but also does pretty well at places like Laguna Seca.

At any rate, I'm beginning to re-think my "good handling approaches," as my previous iterations of "good handling" cars have crashed...

One idea I got from Rod's "Autocross 101" site was the de-arching of leaf springs for a bit of lowering, instead of a bigger block that would just make a bigger lever between the axle and the spring. Today, I removed one of the five leaves in each of my packs (while working on my installation of a biscuit bar)...

Ron, I'll be practicing my picture-taking skills at the MotoGP event at Laguna Seca next weekend. Maybe next time I'll have more communicable pics...

[Ron Sutton]

Sounds good on the pics.

All handling cars have to travel the suspension to work. There are two strategies that work.

Roll Angle vs Pitch angle

The car can’t run flat … it needs to travel … so it’s either got to Roll or Pitch … that’s the primary difference in the two tuning concepts I’ll outline.

• It can’t pitch a lot AND roll a LOT … it would be dangerous & undrivable
• It can’t pitch AND roll a LITTLE … it would just skate on the road surface.
• It can pitch a lot & roll a little … OR it pitch a little & roll a lot

You need to pick a path … so here is what they look like.

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

Conventional:
• Stiff front springs
• Small, soft sway bars
• More Roll
• Less Pitch

Old School – Let it Roll
• Moderate to High Roll Angle (3 to 6 degrees)
• Front suspension doesn’t compress much on entry. (3/4” to 1-1/2”)
• Load the outside tires for grip & unload the inside tires so it will turn.

Drawbacks:
• Too much roll angle overworks the outside tires in corners & underworks the inside tires.
• The tires heat up quicker & go away quicker, providing a better short run set-up.
• After tires “come in” the car is “knife edgy” to drive.
• Very line sensitive … drivers say, “can’t drive it just anywhere” … meaning it handles poorly out of its optimum groove.
• As the track grip increases & the car rolls more … these problems magnify.
• When it rolls a lot & you brake hard, the inside rear tire has no grip. So to prevent from being loose on entry you must run stiffer front springs.
• The stiffer front springs make the car tight/pushy in the middle … requiring the driver to brake more and run slower corner speeds.


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

High Travel:
• Soft front springs
• Big, stiff sway bar in front
• Known as SS/BB … soft spring/big bar … if no bump stop or coil bind is utilized.
• Same concept used in conjunction with travel stops: Bump Stops or Coil Bind
• Less Roll
• More Pitch

New School – Get the nose on the ground & run the car flatter
• Roll angle is minimal, controlled primarily by the sway bar in front & stiffer rear suspension. (1 to 1.75 degrees)
• Front suspension travels a LOT in dive (compress) to put maximum load & grip on front tires. (3” +)
• Load the outside tires only slightly more than inside corners for optimum 4 tire corner grip.

Disadvantages:
• Even when optimized … it still can not be driven as deep on corner entry as a conventional set up.
• When racing door-to-door in a field of race cars running a mixture of set-ups, the SS/BB set-up is susceptible to dive bomb passes.

Advantages:
• Flatter Roll Angle works the tires more evenly.
• The tires heat up slower & last longer … making a better long run set-up as the tires are “good” way longer.
• Less line sensitive … drivers say, “I can drive it just anywhere” … meaning any line on the track.
• As the track grip increases … the advantages show more.
• The soft spring/high travel front end puts creates maximum grip on front tires for highest cornering speeds.
• Will produce faster cornering speeds & quicker lap times over conventional set-up, all other things being equal.

So the old school car you have seen run so well is using the first strategy & sounds like they have it worked it all out & fine tuned it to its optimum. It wouldn't be a fast a car with a modern high travel/low roll suspension that was also worked all out & fine tuned it to its optimum ... but it would faster than those that aren't. :)

[Bryce]

Rod,

I think you have Rustomatic confused with Craig510. It was Craig that won the SM AutoX class at GG.

I know ... all those Falcon guys look alike. :lol:


On a more serious note, that track, with the dips in the middle, was so rough ... I don't see how anyone with a tie down shock package (lot of rebound) could get around it without skipping the front end across the track. :eek:

I sure hope they don't continue running the track in that location. :fingersx:

.

There are to many falcons now. haha.

[Rod]

opps...sorry Rusto, for mixing you up with another car, very sorry about that, no disrespect intended, and thanks for reading my site! PM me your address and size I will send you some swag




On a more serious note, that track, with the dips in the middle, was so rough ... I don't see how anyone with a tie down shock package (lot of rebound) could get around it without skipping the front end across the track.

Trent says they will have it there again, but there going to make it larger

[Ron Sutton]

Trent says they will have it there again, but there going to make it larger

That's too bad. An AutoX course with drainage ditches running through it doesn't make sense.

[QuarterD25]

There are to many falcons now. haha.

Its the new non-conventional oreo.....

[Craig510]

I don't want to high jack the thread, but racing at the goodguys event that you won we noticed that you're car was very soft and (for lack of better term) wallowy, perfect for that size track with the bumps, were many of our cars were set up stiffer I know that some of the guys went faster after softening up there cars for the track I personally removed all the low speed compression from my shocks and had only a little high speed to off set the drainage ditch, and I reduced the rebound to half of what I run to let my own car wallow more on the track I know that some disconnected front and rear sway bars to wallow there cars, on a faster higher speed track the softer, wallowy suspension will have to much roll at higher speeds and the car will be slow trying to recover from the weight transfer, just my opinion and observation

Hey Rodney,

Sorry I didn't jump in sooner, I bought a house a few weeks ago, and just got my computer set back up today. Truth be told I got lucky that my setup worked so well and the track was so rough and slippery. I only have a 1" front sway bar, however, I just ordered the Ridetech 1.25" bar today (got a great deal with my $250 gift certificate). When I first built my car a couple of years ago, I was basically building a GT350 clone with a falcon body. I had several good conversations with Walt Hane at EPS (eps-hane.com) and use his 1.75" wide "B" Mustang rear springs and 600# front based on is recommendations. After I got my car running and ran my first event in March 2012 I knew I was out gunned, but I couldn't drive well enough for it to matter. I spent the rest of the year making my car drive-able (power steering and new trans) and worked hard on my driving.

After I burned the corners off of my tires and flipped them on the rims and burned the corners off again from trying too hard and plowing into the corners I decided I needed to step up to some bigger wheels and tires. I studied Maier's car and quizzed him on the drop spindles and he shared that he shortened the steering arms as well. I spent hours under my car taking measurements and more hours on SolidWorks modeling parts and the geometry to get the big tires to fit. I spent a few weeks in the garage on a mad thrash session building parts and fixtures to get a couple of runs in the 2013 March meet, ran SCCA in April, and had it dialed by June.

Walt builds cars with the "Lean to Win" philosophy and it works fairly well. One of Walt's concepts that I used is not to worry to much about what the static alignment is and focus on getting the tire in the right place during hard cornering. The thing I found is the more caster I ran, the better the car got, way more than most people are comfortable with.

I am very impressed that Ron is sharing so much of knowledge with us. I finally feel like I know how much is too much and just learned what to do with my panhard bar, and his description of vehicle dynamics is absolutely spot on. Mid corner my car pushes fairly bad, but the GG coarse was so small and slow, it didn't really matter; the speeds (and surface) did not allow for hard braking so you could not generate enough pitch to plant the tires and use the stiff bar. I have also noticed that on longer coarse I start to loose traction at about the 40-45 second point, it is probably my tires getting over heated. It will be interesting to see how the car works with the stiffer front bar. It should let the inside tire do more work and ultimately provide more grip.

I will be running SCCA this Sunday at the Oakland Colosseum. It will be my last outing before the bigger bar goes on. I should get a couple more days in before GG in November and I will be road tripping out to Scottsdale for the shootout. Maybe some of the NorCal guys can get a caravan going.

This is a video of my winning run, you can see the car push mid corner, I almost over-cooked it on turn 3 the second lap, and I stall as I brake across the dip (I might have gotten on the brakes to hard before I got the clutch in)
http://www.youtube.com/watch?v=Wy7YC9Xpc4o