Good evening gentlemen.
I have read many many threads on the positives of going non-staggered, 255 or 245. I then came across a very compelling argument that i then couldn't find any more information on. The argument was actually against a square set up even though many track guys do it. He argued that the reason behind this 255 square set up is that 1) with only a few exceptions 17's only come as big as 255's which explains why there wasnt a bigger rear tire to go staggered and 2) was to get more front grip which throws the handling of the s2000 off as the car doesnt need more front grip. People were just after more grip but because the "only as big as 255 tire" issue the set-ups became square and then compensate with a larger front sway bar to make the car more neutral. He also argued that all good things that come from a 255 square set-up could be gained by a 245 or 255 front and a 275 or 285 rear plus gaining more rear grip.

My question and purpose here is to spark a discussion of this subject that seems not to have been explored.
If you had no rules and were going for best possible set-up, If your fender didnt limit your tire size; Would you still run non-staggered? This then brings in the argument of 17 vs 18 inch wheels and unsprung weight. I mean not to introduce that argument but they can be used in your argument. I mean more in the abstract.

My set-up: I am going to run some 18 X 9.5 +40 Enkei NT-03's. I have downforce front fenders(+30 mm for those that dont know) and will be doing custom rear fenders to fit some meat under there. I also have buddy club n+ coils(I know not the best but thats what I have)

ok Go!

 

NS, you can rotate the tires more often = cheaper?!

 

The problem is the best street tires in sizes that fit our cars (RS-3 and Star Spec) do not come in 275 or 285 sizes. So most people choose to run 255 square rather than run inferior tires that are a little wider in the rear (and have to have wider, heavier wheels to do it). You can get R compound tires in those wider sizes, but I've heard of cars having difficulty getting those wider R-comps up to proper operating temperature, because we are light cars with limited power. A narrower tire that is properly up to temp may grip better than a cold wide tire.

Now if you could get RS-3 in 285-35-17, it might be a different story.

 

The goal is the most total grip, and that will be achieved with the most tire everywhere. Forget about differences in tires size as they relate to 'front grip' or 'rear grip.' Any oversteer/understeer handling imbalance needs to be tuned out via front-to-rear roll stiffness or aero.

For example, say running 245 front 255 rear makes the car balanced, but running 255 square means oversteer, then just change your front-to-rear roll stiffness distribution and you will have more ultimate grip with the 255 setup. With a properly setup car, more tire everywhere means faster lap times, period.

 

You are still sticking to issue number 1. Dont as I have 18's.

 

ok so if the goal is most total grip they you are still arguing against yourself. Yes you are right that a 245/255 may have less total grip than a 255/255 set up(which I think is arguable too). But you are still staying with issue number 1. If you could go larger in the rear would you? With your argument I think yes as it would give even greater rear grip and a more natural and neutral handling too.

Think outside the box of the 255 limitation

 

18" tires are way more expensive...??

And why not run a 275 or 285 on all four?

The truth is:

Add as much grip as you can IE the largest good tire you can fit under all four and then adjust how much each tire is loaded via suspension to achieve desired handling characteristics.

 

I have to disagree with this. More tire means more weight and more aerodynamic drag. Spinning up those 4 monster wheels and tires saps horsepower. You can definitely have too much tire. As a thought experiment let's take your statement to the extreme. Consider a car that's limited to 165s up front but can run 285's in the rear. Do you really think you can balance that car's handling using roll stiffness or aero? You'd overheat the front tires on the first lap with all the understeer so front grip would be even lower than what a 165 would normally give you.


There's more than one type of handling balance. There's corner entry under trail braking, mid-corner with maintenance throttle, corner exit under heavy throttle; then high, medium and low speed corners. It's not as simple as "tune it via front-to-rear roll stiffness."


This is definitely a concern with light cars like the Miata and S2000. You have to get r-comps up to their optimum temp to get optimum grip, and with too much grip difference front to rear you will overheat the slipping tires.

I'm not saying that running 285's in the rear is definitely going to be slower but it sure seems the fastest normally aspirated S2000s are running non-staggered. There can be a big difference between max tire and max grip and as a general rule in suspension and aero tuning, "more doesn't equal more."

My racing budget is limited so I really like being able to rotate the tires around for maximum longevity.

As a quick example of the complexities of suspension tuning I was having problems keeping up with a car in a low speed, accelerating corner (Summit Main Turn 6). The other car was running similar lap times to me so I wanted to "fix" this handling problem. I softened the front damper rebound settings and sure enough I got more drive out of the corner without the understeer I was experiencing but my lap times decreased by almost a half second. It turned out the shift to more front grip for Turn 6 caused more oversteer on most of the rest of the track. The oversteer lead to overheating the rear tires which caused problems all over the track. Needless to say I went back to the previous front damper settings.

It's things like this that require so much practical experience to go with theoretical knowledge to get the last few tenths from your competitors.

 

Now this is the type of reply i was looking for. Robrob you state that some of the fastest n/a s2000's are running a square set-up(presumably 255's). You also talk about tire size vs. power. In view of my car; turbo with 400 whp this idea changes as my rear tires are in much higher demand than a 200whp s2000. What do you think? I am interested in your view. Also what do you think becomes just too much front tire for our cars no matter the power... 265's? 275??? What about the rears. I know this is very subjective but either way i am interested in your thoughts.
Thanks

 

A forced induction S2000 would most likely benefit from more meat in the rear but you'd need to adjust how you drive the car. With the extra hp you would deviate more from the geometric line through a corner and apex later so you can get on the throttle earlier and benefit from the extra torque. If you're fighting power-on understeer you can sometimes compensate by apexing later so you have less steering to worry about as you're powering out of the corner. A low power Miata will normally benefit from driving the geometric line (not early or late apex) to conserve momentum, but a poor handling muscle car will benefit from a very late apex to take advantage of its near straight line performance.


I don't know, but it wouldn't surprise me if it were north of 275. If fitment and rubbing weren't an issue I would have tried the big meats at all four corners.