Tire size question on stock wheels

[Elonheater32]

Hey there guys, I have the standard front wheel 15x7 and the upgraded wheels for the rear 17x9. Right now I have the factory tires on the Atom (205 front and 245 on the rears). I am strongly considering going 235/50/15 R888 for the front and 275/40/17 R888 for the rears. I figure by giving the same bias of a difference of 30mm between the front and back will give the Atom the same handling traits except with more traction. Also, both tires would be the same height as the factory ones so that would not change the ride height either.
Will those tires hold up well to track conditions on those wheels as the tires are a bit wide for a 7 inch and 9 inch wheel, but seems like guys on this forum do it all the time. Any suggestions and input that you guys can give me?
I figure that this tire combo would give me much better traction on the track (corners) and also improved traction for the street (straight line accelerations). Nothing is fun about this car snap oversteering!!!

[9and3]

I spoke with TMI on tire sizes as I too thought bigger tires will give me more grip. They cautioned me on bigger tires on my SRA, they said that because the car is so light that its very hard to get enough heat into the bigger tires to get them to give you grip. I am still unclear what is the best tires setup for an SRA which will be solely for HPDE. Any thoughts.

[Richard Buckingham]

I've been running my SRA for >4 years and I've settled on 205/50-15 at the front and 275/35-15 at the rear running Hoosier R7s. For wheel size at the track you want to max out wheel for whatever tire you run so the tire sits right on the wheel and you get the max contact patch and even wear, so for the 275/35-15 I run a 15x11 wheel, for the 205/50-15 I hear you can go as large as a 15x9 (so the Miata guys tell me!) though I have not tried that large yet.

For larger wheels for your SRA you probably can't do any better than to get the 949 Racing 6UL wheels, we share the same 4x100 bolt pattern as the Miata. For the Atom 3... I have no idea.

TMI are correct that getting heat in bigger tires is harder... but not that hard at the rear on the Atom. Of course it depends how hard you drive the car but heavy braking and acceleration will put plenty of heat in the rears. For the fronts you just have to work them real hard on the brakes too, but on a cold track it just is not going to happen. Some people run A7s to compensate for that. Downforce at the front helps of course if you want to invest in some aero but its not really necessary in order to have a good time and a high performing car. Running lower pressures than you might think is right too. You want to monitor heat as soon as you get off track (probes are not cheap but best, cheaper IR gun can work) and monitor wear. Tune pressures, brake bias, dampers, toe & camber as you see fit for optimal lap times but you should just be able to have a single configuration for everything that at least works ok everywhere and is comfortable and balanced. The factory TMI set-up for the SRA is not bad, although I hear they ship spring rates as 400 front and 300 rear which is weird to me, I run very little toe but add a bit more camber to the back but you can get to those tweaks over time, also depends of course on what tire and dampers you run how you want to adjust those.

[762]

I spoke with TMI on tire sizes as I too thought bigger tires will give me more grip. They cautioned me on bigger tires on my SRA, they said that because the car is so light that its very hard to get enough heat into the bigger tires to get them to give you grip. I am still unclear what is the best tires setup for an SRA which will be solely for HPDE. Any thoughts.

My 225 front and 275 rear hoosier A7s get enough heat in them in an autocross environment (and completely changed the performance of the car so that the chassis could really work). On track you would be fine. Next time I buy street tires I will also be going wider to at least 225/255 as well.

[Richard Buckingham]

I am strongly considering going 235/50/15 R888 for the front and 275/40/17 R888 for the rears.

It will work, its not ideal though and you'll want to watch tire wear. If you're eating up tires at the track it gets expensive quickly. From a performance standpoint you might want to try a smaller tire for that 17x9 wheel and see if it really makes a difference. For the front you just don't need that kind of width, there's not enough weight to justify it. (IMHO)

[Elonheater32]

I do about 6 HPDE a year at VIR so honestly tire wear is not an issue besides I use my M3 for some of these events when the weather isn't ideal for the Atom. I agree that going wider in the front really won't offer me any extra benefits, but I thought that it would be safe to maintain the same bias between the front and back tires. As the Atom will never ever understeer I suppose going wider in the front will not make a difference.
About 90% of people that track their Atom that have quite a bit of experience have gone wider for the tires.
My question is will the 275 tires fit securely on my 17x9 wheel? Also, would I be better off keeping the 205's up front or should I go wider to maintain the Factory bias between the front and rear tires?
Also when I take my Atom out for a drive in town.... sometimes it can be a bit scary making a hard shift from 1st to 2nd and sometimes 2nd to 3rd if the weather is cool....so wider tires will help a bit in the daily driving department as well.
Thanks guys.

[Richard Buckingham]

The 275 will fit ok I just don't think you'll really notice much benefit from changing out both tires, rears is all you need to add. I wouldn't worry about the 30mm difference, I don't think that's really the right balance for the tires anyway (which is why I run 205:275) but I don't take my Atom on the street, for daily driving it might help I really don't know about that.

[9and3]

I've been running my SRA for >4 years and I've settled on 205/50-15 at the front and 275/35-15 at the rear running Hoosier R7s. For wheel size at the track you want to max out wheel for whatever tire you run so the tire sits right on the wheel and you get the max contact patch and even wear, so for the 275/35-15 I run a 15x11 wheel, for the 205/50-15 I hear you can go as large as a 15x9 (so the Miata guys tell me!) though I have not tried that large yet.

For larger wheels for your SRA you probably can't do any better than to get the 949 Racing 6UL wheels, we share the same 4x100 bolt pattern as the Miata. For the Atom 3... I have no idea.

TMI are correct that getting heat in bigger tires is harder... but not that hard at the rear on the Atom. Of course it depends how hard you drive the car but heavy braking and acceleration will put plenty of heat in the rears. For the fronts you just have to work them real hard on the brakes too, but on a cold track it just is not going to happen. Some people run A7s to compensate for that. Downforce at the front helps of course if you want to invest in some aero but its not really necessary in order to have a good time and a high performing car. Running lower pressures than you might think is right too. You want to monitor heat as soon as you get off track (probes are not cheap but best, cheaper IR gun can work) and monitor wear. Tune pressures, brake bias, dampers, toe & camber as you see fit for optimal lap times but you should just be able to have a single configuration for everything that at least works ok everywhere and is comfortable and balanced. The factory TMI set-up for the SRA is not bad, although I hear they ship spring rates as 400 front and 300 rear which is weird to me, I run very little toe but add a bit more camber to the back but you can get to those tweaks over time, also depends of course on what tire and dampers you run how you want to adjust those.

Wow what a great write up. I had a chance to catch a couple videos of you on Laguna which were great watch. Some of your earlier video illustrated the learning curve I should expect, but the later videos were really impressive. In watching the earlier ones it was difficult to see what was causing the car to step out, even the spin was not obvious. I am concerned with how unpredictable this car will be, especially till I get used to it. Anyway appreciate your insight. thanks

[turrbo]

@Elonheater32 You and I seem to be on the same page. I've had my Atom on the street (canyons) for a little over a year now with 205/245 A048's. I've gone through about 4 sets now. I really like the tire, it's very predictable and heats up very quickly. I live about 20 miles from the base of the mountain so there is no trouble in getting heat into the tires on my way up. It's the way down that is a little bit of an issue. I just pull over to a looking point and do a donut or a light burn out to get heat into the rears and then just ease into speed for about 3 miles to get the fronts warmed up. I actually like the process because it keeps me safe and more attentive.

I've recently been thinking about going wider with both the front and the rear, and I have the same wheel set up as you. However I was going to try something a little different...

Fronts: 225/50/15 R888R
ToyoÂ*Proxes R888R

Rears: 275/40/17 R888
ToyoÂ*Proxes R888


My justification is two fold here...

1A) I don't have any aero in the front, so I need to get my tires to heat up faster in the front than the rear. From what I've heard from people the R888R heats up faster than the R888. In theory the fronts and rears will warm up at similar time/rate. Again, this is a theory.

1B) Tire wear is at 2 rear sets for every one front set, hence why I'm going with a more aggressive tire in the front so that they wear at similar rates. Granted they both have the same wear rates, I've been told that the R888R's tend to go towards oblivion faster than the R888's

2) They don't make a R888R in a 275... they do however make a 255.


It's not ideal to put a 275 on a 9" wheel, a 265 would be much better but no one makes a street-able slick type tire in a 265/40/17. At least not one that I've found. I just put on my last set of A048's, let me know what route you go. I'm interested, I see myself buying a new set of tires in the next 2 months or so.

[FourFather]

Here is a public answer to a private message question.

For ten years so far, I have enjoyed my Ariel Atoms, first on the street, and then quickly, and almost exclusively, on track, once I experienced how fabulous these cars are, on track.

Here is my experience/input regarding the question of "what tire to use".

I have never been disappointed in Hoosier's latest autocross tires, when mounted on their recommended wheel width, and at pressures on the low side, to allow for the extreme light weight of the Ariel.

Cheers,

Eddie FourFather Hill