rear wheel spin

[CM/FFdriver]

Hello All,

So had an interesting event this weekend, with some work I have got the front end of the FF/CM to turn in great on entry of turn, Mid turn in great and exit of turns good to great very happy but now I seem to have a more pronounced wheel spin. I know that the front is gripping better and the next event will try the front sway bar adjustment but other then F springs and F sway bar adjustment what other thing can I try?

Spec:

Front camber -1.5
Caster +4.5
toe -1/16

Rear camber -1.0
caster ?
toe +1/32

front to rear rake 1/4

I thought I read somewhere that there was other things that affect the rear and the way it plants the power to the ground so any help would be great. I had a 14 turn course today and if you see wheels spin out of every turn that could be .700 of a second. Just the way my brain works.

Ben

[ewcmr2]

Less rear bar?

[Purple Frog]

Lots you can do. Many of the things on the list to help the rear might compromise the front that you now like. Setups are almost always a compromise.

In solo, most would rather error to the side of oversteer, rather than understeer.

First rule. Don't chase bad tires.

Since most solo courses are very flat and aero does not play a big role, can you lower the rear ride height any?

Do you have in-car video? Any chance you are not unwinding the wheel fast enough from apex to corner exit?

If rebound in the rear shocks is too stiff, inside wheel can't drop fast enough when car rolls hard to one side.

[CM/FFdriver]

Lots you can do. Many of the things on the list to help the rear might compromise the front that you now like. Setups are almost always a compromise.


First rule. Don't chase bad tires.


Do you have in-car video? Any chance you are not unwinding the wheel fast enough from apex to corner exit?

Getting new tires next week but the tires I have now are pretty good to great, got TTD so they can't be that bad.

I'm working on a Video right now

Ben

[CM/FFdriver]

Less rear bar?

I did put less bar in and it was getting better but not the wheel spin

Ben

[provamo]

i have successfully added WEIGHT to a corner to reduce/eliminate wheelspin

(this was on a solid axle car)

[S Lathrop]

Try removing the rear bar.

Your wheel spin is because you are rolling the car about the inside front to outside rear axis. This roll is unloading the inside rear maybe even lifting the tire off the ground.

You may need stiffer rear springs, more front ARB and maybe stiffer front springs.

My bet is that when the car is fully loaded, you have a lot of load on the outside front tire and if it was not for completely unloading the inside rear, you would have a strong push.

In short, something is too soft, be it sway bars or springs.

[Roux]

Could Steve's diagonal loading come from the current caster setting plus too much scrub radius?

[S Lathrop]

Could Steve's diagonal loading come from the current caster setting plus too much scrub radius?

Caster can be an issue. I seldom ever use more than 3 degrees. But I doubt that reducing caster will fix the problem by itself. 4.5 degrees seems like a reasonable number.

Front and rear roll centers locations can cause wheel spin in some situations.

[mwizard]

Ben, That is enough caster to add close to 1 degree of negative camber in turns which may be too much.
I had the same problem when I disconnected the front bar, great turning and rear wheel spin on exit. I built a new adjustable front bar and set it to min and that solved it(mostly).
At my last event I upped the front low speed compression 4 clicks(out of 30) and was very happy with the turn in; did the whole back side of the course in 4th including a box and slalom. Only got to try that once
Mark

[CM/FFdriver]

I'm feeling I found out why, well the small adjustment the front bar made a big difference to the rear wheels spin for me. It's funny how the smallest adjustment make a big difference in the way these cars work, I usually make big adjustments like an 1/8 of an inch but with these cars that's to big and I back it off 3/32 to find the right feel. Crazzy!

Ben

[B17overhead]

Sounds like almost everything was covered by others.

However, I don't think I saw rear droop travel mentioned- except in the context of rebound damping speed.

While obviously your roll couple distribution towards the rear has a significant effect upon unloading the inside rear- you probably STILL would like to run as much rear stiffness vs. front stiffness as you can w/out wheel spin.

Chuck

[CM/FFdriver]

well I'm thinking that the old stock shock for an 84 VD is my problem right now, adjusted the front sway bar and I will again this weekend but because I don't know what the rebound settings are on these shock because over all the FF/CM car feel great, no push at all well maybe the very slow turns. Shock should be here next month, can't wait.

Had a National Champion drive my FF/CM car and he like it very much, quote: lots of mechanical grip and Steven (DM driver) was 1.3 sec behind me, I'm good with that. This last weekend Mark drove my car and really like the way it turned in with very little over steer, Mark like to lock up my front brakes ???

Very fast event this weekend can't wait to make more adjustments.

Ben

[R. Pare]

I would look at increasing the rear spring rate and dropping the rake down to below 1/2 inch. Having a too-high rear ride height frequently gives a wheelspin problem, especially right after a hard braking event where the rear goes even higher.

[CM/FFdriver]

I would look at increasing the rear spring rate and dropping the rake down to below 1/2 inch. Having a too-high rear ride height frequently gives a wheelspin problem, especially right after a hard braking event where the rear goes even higher.

You know R. Pare I just looked over my first post and saw I made a mistake on the Rake so it's at 1/4 of rake at this time.

I will say that maybe a lot of experience with wheel spin is base on what site we go to. Just got back from a great event at Crow landing, very big site, lots of grip and more increasing radius turns instead of decreasing radius turns so I didn't have any wheel spin that I heard of course.

Ben

[B17overhead]

Wow Ben, you must have been really tuned in on that course, Driver + car.

I looked at the results, and you buried everyone including the F125 guy.

W/out any slow tight and then on the gas in 1st or 2nd stuff like at Marina, I would imagine inside wheel spin would not be as easily encountered. Less torque to the lightly loaded tire if you were coming out of the corners in a higher gear.

The on-line map surprised me with what looked a neater twistier course than the marginally "Solo 2" ones with street cars getting over 100 mph. You know, where the course designer ran out of cones and/or imagination.

-Chuck

[CM/FFdriver]

Wow Ben, you must have been really tuned in on that course, Driver + car.

I looked at the results, and you buried everyone including the F125 guy.

W/out any slow tight and then on the gas in 1st or 2nd stuff like at Marina, I would imagine inside wheel spin would not be as easily encountered. Less torque to the lightly loaded tire if you were coming out of the corners in a higher gear.

The on-line map surprised me with what looked a neater twistier course than the marginally "Solo 2" ones with street cars getting over 100 mph. You know, where the course designer ran out of cones and/or imagination.

-Chuck

Hey Chuck,

The course never got over maybe 85 MPH in one area of the course and yes they ran out of cones at the end of the course.

I believe the slow turns at Marina has help me with my set up I guess, the problem I was having at this event was exit oversteer and lift oversteer which I guessing is my shocks like I said. The thing is I'm trying not to over think this stuff, you can kill yourself overthinking car setup with this and that, so my biggest goal is learning how to drive this car.

New shocks are going to change all this, how fun is that going to be.

Ben

PS. Chuck you should come out again

[B17overhead]

Ben,
No single roll couple setup is likely to be optimum both places given the big difference in surface and courses. Good shocks might help you handle the transient situations better at both, however.

I'm picking away at my own car again now trying to work on it inside the little 7x12 box trailer. My car sure has suffered from a case of arrested development. I spent the last year and a half working on our house and landscaping and we finally sold it 3 months ago.

-Chuck

[chrisw52]

Ben,
remember that marina will always have a slippery surface compared to crows... any wheel spin problems will be exaggerated at marina.

Chuck, you should bring your car out! it would be great to have some more competition.

[CM/FFdriver]

Ben,
remember that marina will always have a slippery surface compared to crows... any wheel spin problems will be exaggerated at marina.

Chuck, you should bring your car out! it would be great to have some more competition.

I think your right Chris, Marina is nothing like crows but I still like Marina for the technical courses and will go there more often then not.

Ben

[B17overhead]

Thanks for the invitation to get on out there again. Now that I've sold the house, I have more time to work on the car. Finishing up another muffler so I can have 3 in series. Who woulda thought only 893 cc needs that many mufflers?

[CM/FFdriver]

So after this last event at Marina the event that I ran, it's the site that has the problem with wheel spin, from the last event at Crows to Marina I have a handle on which way to go. The course I ran on had 2 fast sweepers and 4 90 degree turns at Marina, the car felt great but I know which way to go now, I'll just keep tuning for the best handling for this site and for Crows.

Ben

[CM/FFdriver]

Well wheels spin is fixed, shock were dead, both front shock were not working at all, left rear was working? right rear had no compression and tons of rebound.
So all new Penske and problem solved very happy camper.

Ben

[pleavens]

Well wheels spin is fixed, shock were dead, both front shock were not working at all, left rear was working? right rear had no compression and tons of rebound.
So all new Penske and problem solved very happy camper.

Ben

That's great Ben.
Did it take much adjustment of the new shocks to get there, or did it just work "out of the box"?

Phil

[CM/FFdriver]

Well it worked right out of the box but I'm tuning it for how I like to drive so getting better with each event.

Ben

[mwizard]

Ben, When I disconnected the front bar, I got great turning, but lots of rear wheel spin on exit. I set my new adjustable front bar to min and the rear wheel spin went away(well about 95%). So play with the front.
Mark