audipwr1

Guys any idea why I am over steering?

Now don't tell me it's because I have no rear wheel or suspension - I know that's not what's causing it, it has something to do with the front end, maybe move the sway bar one notch? Let's discuss

mmuller

I think you need more camber.......

Ray S

LOL....

ProCoach

Don't ever let anyone say that RLer's aren't eternal optimists...

Of course, it is Kibort!

danielyonker

Anyone have more potato chips?

TFBoxster

There is no such thing as a perfectly smooth track surface. As has been said the physics do not change. Get the car off the bumpstops.

Theoretical optimum pyro temps and camber settings don't always produce the best handling/fastest laptimes.

Try different settings.

Once you've done this analyse your driving - brake release technique...

Veloce Raptor

Ye of little faith. It's now 5 going on 12

mark kibort

yep, we all agree that there is no perfect surface, but my question is about steady state push, on a "realtively" smooth surface. I also agree about the pyro temps... all that tells you is that you are getting nice average wear on the tire and doesnt really indicate handling optimization. however, it can point to changes that can help reduce wear .

and, again, im not on the bump stops on the turns in question.

Yes, willl try a few setting changes that make sense.

mark kibort

Well, if you look at the interaction and weeds between the VR posts where usually, 3 posts are needed just to explain the question or point to him, and the joshing around, its expected.

the funny thing is, there is a lot of advice to point to driving styles by guys that might have as much experience on the track, but the knee jerk reactions to the monday morning quarterbacks are usually driving. Ive done enough coaching to know that sometimes its the car and sometimes the driver. while in the car, its easy to feel and or change while riding with someone too. however, in this case. this car has been in more races at laguna seca than most any cars around. you can see clearly the same car in the two video shots above, at the same turn doing greatly different things at that same turn. entry, through and exit. there are tests to see if there is imbalance is present, and clearly to me , there is. further proof is when i ran SpeedVision GT races there on 280 tread wear tires. Not just me, but the etire field was a full 4 seconds off their times, yet , in the car, you would never know it.. including me. why, because the car was balanced front to rear, by small suspension changes. Also, in the rain, where grip and drving style to approach turns is GREATLY diffeent, i have video of the GTGP rain race with Sofro and the car is loose, not pushy but generally still under me. so, i am no stranger to changing the stlyle to help the car get around the track and not cause unruly characteristics.

So the point is, in this case, i have a slight push... im looking at the group to share ways they have solved this issue. i believe firmly that it is a combination tire and set up issue...... proven by the fact with newer, not even brand new, the set i have now, works amazingly well. 1:36.1 at laguna is pretty decent time for a car of this level technology. a lot has to be right to do it.
However, as soon as the tire quality goes down, the push rears its ugly head and im loooking at ways to tune it out. If i do, i have no issue with a looser car, in fact i enjoy that, but i think it willl be more adaptable and keep its balance as the tire grip changes.

again, the car is not on the bump stops other than the exit down the corkscrew and you can see by any video there is no adverse effects, other than possibly i might be able to go quicker down that section by making changes. however, if you watch can pro events, you can see that most cars bottom out here and in fact, you can hear the suspension hitting the ground , with sparks flying( talk about infinite spring rates! )

anyway, i thought there would be a little more chassis change suggestion rather than the usual bantering (VR) , but somethings never change!

can you guys keep the discussion around roll couple and things you have done to fix pushy cars? So far, i have to try and stiffen the rear sway bar from what Scott said during the roll couple dist discussion, and that makes the most sense so far. I might also try reducing the bump in the rear to take a set better, but i dont think that will change steady state push as much. the only other thing is checking the Weisache rear end settings to see if its toe'ing in too much on throttle lift or in compression (or steady state turns where the lifting wheel could be toeing in)

Matt Romanowski

Mark, this is the crux of the issue - you are trying to fix things with too many unknown factors causing it and you are discounting things. Be systematic about what you are doing. Make sure the car is not on the bump stops, not just tell us that. As I showed you, all tracks are bumpy. Then, fix your bump steer problem. Then we have something we can work with and fix. Until then, it's mental masturbation.

The fact that it works until the front tires are dead (way before the rears) just tells us it's working them too hard and there is a problem. It's not indicative of a solution.

If you want help, you have all the answers you need. If you want to do whatever it is you want to do, then go for it, but leave us out. We are all trying to help you.

mark kibort

Thanks. of course ill take the help .
its not on the bump stops as you can see that on the video for the turns in question. I have marked (tie wapped) the shocks to prove that too. you can see from the video that there are some turns where the wheel and tire are not moving vertically, so very smooth. I kinow there is not a perfectly smooth track, but ive also not seen any greater issue with bumpy tracks like old buttowillow.
as far as the fronts wearing out first, doesnt it make sense if most of the forces are on the fronts, with brakikng and trail braking far exceeedng the acceleation forces on the rear tire even under power exiting turns? it makes sense they would go first as most do. i would be surprised if you dissagree with that. however, the reason i had a lot of push in that one video, was due to the fronts, in particular being older and less grippy than the rears. (just bad luck with the used tires) the general push, is what im talking about. some here have said, basically, get used to it, its a problem with front engine cars, but ive driven enough other race and street cars on the track, to prove that that isnt always true. the mustang i was coaching in, was much more loose and had a ton of grip up front. It has alll the best bolt on mods for the mustang suspension, curing all the bad stuff the stock geometry causes.

Im also asking if there is experience fixing the bump steer and seeing marked results? i would think its pretty common in the pursuit of making a production car into a race car that lowering would hurt the bump in most cases. so, im wondering if there is some similar stories of someting like, "i had a push and when i put the lower control arm extentions, my roll center was better and reduced the understeer". something like that. maybe i am discounting the effects of the drooping tire, but that is also something im inquiring about. does that tire that when level , having 850lbs on it, do much when its toe is out of wack due to bump steer issues, when its force drops by half to 425lbs and the compressing side goes to 1275lbs? ive already mentioned that the compressing side bump steer effects only desensitizes the steering, but the drooping wheel is loosing part of the ackerman effects, or maybe neutralizing it. If so, then the bump steer fix is a good idea. I dont know if there is anything available for the 928. I know Anderson in the much better prep'ed 928 had all the stock attachments modified and fixed that issue. ive driven that car and it was more nimble. but, it also was on slicks , with a wider track.

Ill do some more verification and testing to see where things are at. But so far, without major changes im left with tightening the rear swaybar and checking the rear alignment for excess rear toe in. (as well as testing higher ride height to reduce the bump steer issue)

Veloce Raptor

Mark, the comments by Earlierapex regarding your driving "style" contributing to the problem big time are spot on. Take it or leave it , but I finally watched the videos and he is absolutely correct.

mark kibort

Ill disagree with you Dave. the style has nothing to do with it. look no farther than the video from a later date, same track, same car no other changes but tires. (and slightly faster times) look at the dramatic difference in hand position.

if you were correct, i would keep the same speed of turn entry and have the same problem, but the proof is that i didnt. An even faster speed, and none of the ill effects of the push. You would also see a problem in my WCGT video, and there was not. (and thats at 4 seconds slower a lap using street tires), and in the rain race... no issues there either. you are discounting a major element of a race car , the tire and the tire grip balance between front and rear. Further proof, later in the video, i slowed way back to do exactly as earlyapex had suggested, (this is basic stuff) and tried the slow in faster out approach, to no avail. there was absolutely no front grip at all. during constant radius turns, punching the throttle to get rotation was impossible. the fronts were just gone

Sometimes, you just have a push and its due to the tires and there is nothing you can do to drive around it.
In the push video earlyapex commented on, is a clear example of front to rear inbalance. newer tires in the front seemed to cure it almost entirely.

TXE36

Are you kidding? This thread is just getting warmed up.

-Mike

winders

If you would stop driving on $hit tires the car would behave more consistently and you would be able to use normal chassis tuning tools (sway bars) to tune the chassis balance.

Of course, it would be good to fix any bump steer and shock travel issues as well. Maybe your buddy Mark Anderson has some tips for you in these areas.