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Discussion Starter #1
Just installed BC Racing BR type coilovers on my spyder and it's oversteering like crazy during autocrosses now. Im running 205/50/15 bridgestones (re-11) all around which probably doesn't help since it isn't a staggered setup. I finally got the perfect rollover on the rears (about 36 psi) still couldn't get the correct rollover on the front (went down to 32 psi). I started out with the struts fully hard on all 4 corners, then ended up setting the struts to level 0 on the fronts and 5 on the rears which helped a tad. So trying to decide on what to do, bridgestone makes a 195/50/15 in the re-11 which i could try in front, or I could put some hankook slicks in the rear (225/45/15) and leave the bridgestones up front to try and get rid of some of the oversteer, but then I have no idea how it will handle with two different sets of tires. What should I try!? Advice is greatly appreciated.
 

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BC Racing coilovers are 5k front, 7k rear unless otherwise specified. A lot of autocross guys will run something stiffer (like 8k) up front for better turn in. A car that oversteers a little is not an entirely bad thing for autocross:), although it could bite you on the street. I think you answered your own question regarding the square tire fitment--I'm sure you can feel why this car is spec'd with stagger. When I bought my 91 MR2 it had no stagger--it would rotate in a hurry--the first thing I did was new wheels and tires with stagger.

If I were you I would consider two sets of wheels--one set of street tires with about 20mm of stagger, and some autocross wheels. And maybe add some rear camber. Or... keeping driving it that way in a controlled environment to learn about weight transfer.

By the way, the spring rates are on the springs themselves--it will either say "005" or "007".
 

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Discussion Starter #8
then they are 5k front and 7k rear. i have a seperate pair of autocross wheels and tires, I got them second hand from my uncle so i didnt have a choice on staggered, whats your opinion on putting slicks on the rear and still running the re-11's up front?
 

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then they are 5k front and 7k rear. i have a seperate pair of autocross wheels and tires, I got them second hand from my uncle so i didnt have a choice on staggered, whats your opinion on putting slicks on the rear and still running the re-11's up front?
Haven't done it so I shouldn't comment--but it sounds weird and like you would be trading one symptom (oversteer) for another (understeer). Oversteer is not an entirely bad thing. Most skilled drivers want the car to rotate--they will trail-brake to bring the back end around and use throttle inputs to transfer weight to the rear tires. As you get comfortable with the car, you will probably prefer that for autocross--but in a panic you could put it in a ditch (or worse) out on the street. That is why square for autocross, and stagger for every-day seems like a winner.
 

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Rake buddy, what about rake?

Rake is huge. A little bit too much rake will make the car oversteer like an SOB at the limit. On the Elise's coilovers, 10mm difference in front to rear height made the car go from beauty to scary-really!

No matter what the ride height "looks" like, you need to compare your current rake to your original rake. If your car was steering neutral before (with same tire stagger or lack thereof), then you want to be near that same rake, just lower front and rear by the same amount. For more understeer, less rake (like even heights front and rear). If you don't know your original ride heights, I recommend starting 10mm lower front than rear, and take it from there in 5mm rake changes.

That is for steady state traction in a large radius corner. I recommend doing the stuff above before fine tuning the damping.

After that, then you need to consider where is it over/understeering. Turn in/trailbrake/corner entry, or near apex, or after apex? You can adjust those with damping-of which you'll probably find some comprehensive guidelines online.
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It's probably your "stock spec" alignment that's most to blame. What exactly are your alignment numbers?
 

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Discussion Starter #13
It seems like there is just too much oversteer, do you think moving to a 195/50/15 in the front would help at all, or should I just try to get used to the way it is and mess around with the heights?
 

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I would start with more air pressure in the front tires than the rear. Stiffer damper setting in the front than the rear. With the current tire pressure and shock settings I would expect it to oversteer.

If that doesn't work and you continue to run no stagger then you may need more roll stiffness in the front.
 

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Discussion Starter #16
"Today 08:38 PMcosmin
It's probably your "stock spec" alignment that's most to blame. What exactly are your alignment numbers?"

To be honest I have no idea what my alignment numbers are, if I were to change it, it would need to be something that didn't wear the inside of the tire too much since it is my daily driver, any recommendations?
 

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I sort of fail to see how staggered tire sizes would have much to do with it. We all know the trope by now, wide tires don't give you more rubber on the road or more grip. About the best you can hope for with them is the ability to run softer compounds since they disperse heat more effectively across the patch, but when tire wear over the course of a race isn't a concern (like an autox run) that's really not a relevant advantage. You could run a larger rear tire at slightly less pressure, which might help a little, but seems pretty insignficant to me at a near stock stagger of just a few mm's.

Sounds like a pure suspension issue to me. Stiffness in the front or less stiffness in the rear is the go-to cure. Your tires should be fine.
 

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A wider tire has a wider and shorter contact patch. This shorter longitudinal dimension is what gives the tire additional grip. At high slip angles the rear part of the contact patch is scrubbed sideways. First the carcass will deform so the tire remains stationary with respect to the surface. At some point the tire will lose contact and will slide. The higher the slip angle, the more the proportion of the contact patch which is sliding. The shorter the contact patch, the lower is the proportion of its area which is sliding. That is why wide/short contact patch have more grip at high slip angles.

Considering the slip angles involved in Autox, wider tires are very noticeable.

This particular car in question probably has mutliple issues besides tires. Nonstaggered tires can be made to work, just not very well with 5/7 springs.
 

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I didn't say that a wide tire never had an advantage, I said I fail to see how a near factory stagger would provide a significant effect, or more specifically, how his slight deviation from that could be so disastrous. I think that if you are only going to move from a 205 to a 215 or something like that, your potential advantage is going to be more about tuning with pressures and compunds than it will a possible, maybe, couple millimeters increase in contact width.
 

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I've posted my opinion here about this many many times and I wont go back into it pointlessly here. A tire size change will not make enough difference in handling bias at the limit to fix an "Oversteer!!!" problem. Increasing front pressure to lose grip, or any of the other proposed kill-grip-at-the-front solutions are dumb on anything but event day in desperation.

You need camber, you don't need toe. Chances are the random alignment you currently have is favoring understeer, and getting more grip by fixing it will favor oversteer at the same time as it gives you more grip.

I'd fix the alignment to something appropriate with zero toe, lots of negative camber in the rear, and even more in the front. I'd do that just after swapping the springs front to rear. With the springs swaps, you should be in the ball park, and can tune from there. If you aren't going to fix the alignment, then you can't swap the springs, since that needs an alignment afterwards. In that case, I'd either disconnect the rear bar and try that, or run a stiffer front bar than you currently have.

If you are still listening, I'd say a good suspension for an autocross spyder does not have a rear swaybar, has a lot more front roll stiffness than rear (like on the order of 50% more), and has a lot less compression damping than most you you guys are running.
 
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