For a given steering angle, how fast a car turn (or "change direction") is linear to the speed the car travels. That means any toe issue is amplified by speed.

Red MX5, revising toe settings is a good start, but I don't recommend reducing front camber especially if you have only 1.0 to start with. Like I said, try to narrow down whether it's overly responsive front end or twitchy backend that's causing your grief. A rear wing will help taming down a twitchy back end, but will not help an overly responsive front end. If you aren't in a rush to fix all problems at once, I would leave the wing for after testing out alignment changes. The wing will definitely tame down a twitchy back end. But if you do both alignment and wing the same time, you'll never know if the wing is masking an alignment/tire/suspension problem or not.

 

Maybe there isn't a mechanical problem (though I think you need at least 1/8" rear toe-in), but just needs smoother, slower steering inputs at high speed? I would think any corner at 130 is going to feel less stable and scarier than at 100, and require gentle inputs. Sounds like this is the first you have gotten to such high speeds.

 

wtf... are you on crack.. thats not even 1 degree.. 0.75 is not / \ it will still be | | now if it were 75 degress it would be like this / \

 

[QUOTE=smracer31,Mar 8 2006, 05:34 PM] wtf... are you on crack.. thats not even 1 degree.. 0.75 is not / \ it will still be | |

 

Ok...so I have a question for you. Have you recently had any of your tires flopped? I'm sorry I don't know the proper term, but what I am talk about is have you had any of the tires from the right side of your car dismounted from their wheels and mounted on a wheel on the left side? I ask this because recently I had my wheels PC'd and reused my front tires...well since they had inside wear the tire guy asked if I wanted to have them "flopped" and I said sure...well then a couple days later I went for a spirited drive (not reaching high speeds), it was SCARRY and I very quickly stopped going fast...under braking the rear was SO loose it had me worrying. I can understand why being that the front had so little traction. But anyway, just to get rid of some of the obvious.

As far as toe...try adding a little toe-in on the rear...you need some, and like others have said, at least 1/8". That should calm it down somewhat as it wont want to wander as much. Although, I have been under the assumption that as the car "squats" under acceleration that the rear wheels toe-out naturally and the toe-in is needed to keep them tracking straight, as well as calm the rear down. I would then assume that as the rear lifts that toe-in on the rear increases.

I am also a tracking newbie so I don't know all there is to know yet and am still learning, if I have said anything false, somebody correct me. Not only for others sake, but I also want to understand.

Also, I agree with Race Miata in the fact that you need to figure out if it is an overly responsive front or a twitchy rear. If you like the way the car is set-up under low speed conditions though, I honestly would consider a wing...this would let you keep the same low speed character to the car and have a high speed feeling that you like. Not necessarily covering up any problem but rather getting the best of both worlds

 

maybe for the street, not for the track

 

Whatever you're smoking, I'll have 2.

 

I disagree, a little bit. The back end is definitely getting light in T1. However, the bumpsteer is a bigger issue there.

 

Like I've said before in another thread, there IS a reason why a certain range of toe settings is ideal. Anything way off like 1.5 degrees total toe is just covering up problems and you have your inside tire working AGAINST your outside tire.

 

I've done 130 in a straight line on stock suspension and it's not entirely confidence inspiring. The car is only designed to go 140+ max which puts you into the red zone of nearing the capabilities of the stock suspension. This is why I suggest that your problem may not be tweeked alignment but rather the suspension itself.

If you are going to be running on the outer edge then I again suggest you consider some better than stock shocks and also consider lowering it a fair bit. A wing is not going to be your friend at 130+ as it's not really meant to to provide downforce at high speed (wings are designed for slow speed cornering where downforce benefit > drag penalty. To get high downforce at high speed you'll need to lower the car and ideally although difficult clean up the airflow under it with a diffuser. In a 1500lb 600HP race car 130MPH is low speed but on a 240HP 2800lb road car it's fairly high.

Dropping the car a full 1.5" will make a big difference as will raking it toward the front a tiny bit. It will lower your center of gravity, increase your negative camber adjustments and reduce the airflow under the car by 25-30%. Bump up your spring rates a bit to reduce turn in body roll. All in all you'll get a much faster car which feels solid, planted and predictable. A bump steer kit is good but you can get compensate for moderately bumpy corners with a 1/8" of rear toe in.