Us Sundae Cuppers are limited to 205's, but we are trying to put those on the wides wheels we can. Pinched tires squirm (245/255 on an 8" wheel for instance) where slightly stretched do not. If you're running an 8" wheel, I'd stay a 235 width. 9" I'd go 245, MAYBE a 255 depending on actual tire.
But the big thing is compound. a 205 RT660 has a lot more grip than a 225 Conti EC.
On my racecar, I run 245 40 15 on a 10 inch wide wheel.
The car would be exactly the same pace on a 205 on an 8 inch wheel. The difference is that the 245 last WAY longer. Maybe even more than twice as long.
The wider tire has more ability to shed heat.
The Mustang I referred to is a warmed up 08. My other Mustang is an 89 4 cylinder, it is much faster on a Miata spec tire 205-225 with on a 15 inch rim than it is with the 245's on 17 inch rim. Mostly due to the diameter and weight. Steady state cornering didn't suffer at all, in turns 7-10 at Gingerman.
Short answer: Wider tire lasts way longer in my experience
Long answer explanation:
My experience is limited to the cutlass so.....Heavy, not ideal suspension, mild power
First season when getting started was on 225/245 340tw tires. They did ok and kept me slow enough not to get into trouble until I started getting pretty good at the end of the year they were junk due to heavily overheating them.
Second season I used the same tire but in a 275 square setup. Less auto X and more big track events and they didn't suffer from heat during a session. Significant time improvements (some or a lot of which was due to other upgrades as well) and by the end of the year the tires were still in great shape...maybe even another season in them???
This year the only big changes were adjustable shocks, aero and 200tw (up to a 285 wide as well) with a few smaller upgrades too. Significantly faster again. As Bobzilla said...compound is the biggest factor for speed.....AND wear. It took me about 3 sets just to get through this season which was also my busiest so far. In auto X it wasn't a risk of overheating (and massively increasing the wear) the tire, where as the track events really ate away at them. Rough estimate the compound switch was worth as much as the previous changes of wider tire and lots of suspension upgrades. Same Auto X event each year overall I placed around 90th, then around 65-70th, and this year around 40th out of 130.
What I learned from this all was that if a car doesn't have enough tire under it then it'll be slower and have increased wear. So going wider is more cost effective and beneficial in speed. Staying the same width and going sticky will greatly increase speed but at a large cost to wear. If looking at only doing auto X then by all means go for that sticky tire because its unlikely it'll get overheated and really wear fast. If doing more HPDE stuff then its a decision between the additional speed and cost of wearing through tires vs a slower compound that lasts much longer. In regards to how wide a wheel/tire combo I'd consider more for wear/longevity reasons. As I said above, the wider tire lasted way better over the course of a season than the narrower set. Now on a sticky tire I have wear problems again and I would guess that if I were to go to a 315 that would help reduce wear from overheating of the tire, plus speed as well. But the class I run in most is a 285 wide cap so I'm looking at other tires to try to find a compromise of wear and speed so that costs stay in check.
A wheel and tire thread is on the second page and no pics yet?
I think there are too many factors to say that "X" is better that "Y". The weight of the car, the power, staggered, square, balance, FWD, RWD.... The pictured wheels were my favorite on each of those cars.
The red '97 with 16s (6" front, 7" rear) and skinny tires is a blast to throw around on the back roads. The 2.5L engine and manual steering appreciates the light weight corners and handles great.
The white '01 had 20 x 11s on the rear with a 285 tire. I forget the weight, but it was probably more than twice what the 16s weigh. For driving on smooth roads and looking 'good' it worked, but the grip was no better than 18s and there's sure to be a penalty in performance for boat anchors on all corners.
The black '00 has lightweight 18 x 10, x 7.5 (Turbo I - hollow spoke). It's a great mix of weight, width, and size for that car.
Overall my favorite for the 986 Boxsters is 17 x 9 square for trying to compete and 17 x9, x7 staggered for street play and that has no bearing on what would be best for a Miata.
A nice reference for some Porsche wheels: http://www.944racing.de/wheelweights.php
On the street I prefer wider tires to a point. I went from 245s to 275s with similar quality tires and on the street it seemed to handle and brake better. Going wider than that would have made it faster at the AutoX but price went up considerably, so I stuck with a square 275 setup.
If you have a 255/40/17 and you want wider the 275/40/17 was a go to for a long time and should be considerably cheaper than a 275/35/19, with a bunch of performance options available, at least the last time I looked.
This has actually been enlightening!
I would have expected wider tires to have more of an impact than they apparently do.
However, i never thought that the width and longevity were related. Makes sense.
Lots to think about here for life after the challenge. Challenge will be on 17x8 wheels, or 18x8. Cause cheap.
I like wide tires and I cannot lie, but they are a very money-inefficient way of increasing grip or especially of making a car faster in general. If you can choose between stickier or wider tires, stickier will win every single time. Also keep in mind that around a track, the increased drag and rolling resistance of wider tires can take a chunk out of the time gained by the increased grip, problems you don't have with stickier tires of the same size.
bobzilla said:Us Sundae Cuppers are limited to 205's, but we are trying to put those on the wides wheels we can. Pinched tires squirm (245/255 on an 8" wheel for instance) where slightly stretched do not. If you're running an 8" wheel, I'd stay a 235 width. 9" I'd go 245, MAYBE a 255 depending on actual tire.
But the big thing is compound. a 205 RT660 has a lot more grip than a 225 Conti EC.
Also depends on wheel diameter, oddly enough. 245/40R15 on a 15x8 is a very squeezed fit, but 245/40R18 on an 18x8 is a square fit.
I'm also of the mindset that, unless it's a chassis that is severely limited in the tire width you can cram under it, you are almost better off not going so huge that you need fender flares, at least when you are autocrossing. Sure, you now have monster grip, but you are also having to steer the car around more to avoid cones. I saw a CAM-T Camaro this summer that had flares that would make Kei Miura blush to cram 335-width Rivals under it all the way around. And, yeah, I'm sure it probably had grip for days, but when you take a car that's already on the large size for the course and then widen it a good 4-6", you're really just making things harder on yourself.
Going wide does help with heat resistance though. We have a very fast driver in the area and he bought a Focus RS when they came out and was running it in D/Street with OEM-sized RPF-1s with 275-width(!) Rivals. So I got talking to him and he said that he had done extensive testing and found that peak grip and the fastest runs were the same between the 245s and 275s, but the 245s were much more prone to overheating and he was having to spray them a lot to keep them on pace, while the 275s he could pretty much hot-lap it with minimal or no spraying and the run times would stay consistent.
This is interesting.
I'd never given consideration to wear as I'm only interested in lap times, I also run Hoosiers so I'm not expecting to get more than 7 days on track with them.
I don't understand a common refrain in this thread.
Stickier or wider. DO BOTH!
Going from the 215 Primacy's to 255 Star Specs on my BRZ was mind bending.
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