Track - Autocross wheel size poll

[949Racing]

We are curious to see what wheel sizes you all are looking for for your S550/S650 for competition style driving.

If the wheel size you are looking for isn't in the poll options, add it in a reply.

All the options assume adequate clearance for whatever brake system you are running and correct offset for stock fenders. Some of the wider options might require extra camber and fender rolling. Thanks for sharing!

Sponsored

 

[philly gt]

I don't autocross, but I run a 20x10, 20x11 staggered setup on my 2016 GT. I have 275/35s on the front and 315/35s on the rear. I wish someone would sell a 20×11.5 -12 so I could run a 335 or 345.

 

[kz]

The answer is only one - the widest that can fit (18x11,19x11) or possibly 12" wide but that requires some modifications.

Don't know why would anyone want anything narrower, even tires that aren't super wide benefit from wider wheel and more support. I have some doubts whether the people that cast some of the votes autocross and are actively shopping for the wheels (I get that someone already has wheels and want to use them, but while shopping, no reason for anything less than 11" wide).

 

[Jstang23]

The answer is only one - the widest that can fit (18x11,19x11) or possibly 12" wide but that requires some modifications.

Don't know why would anyone want anything narrower, even tires that aren't super wide benefit from wider wheel and more support. I have some doubts whether the people that cast some of the votes autocross and are actively shopping for the wheels (I get that someone already has wheels and want to use them, but while shopping, no reason for anything less than 11" wide).

No, the answer is not always the widest. Grip to weight ratio gets very important when you go larger than a 11 inch wide wheel in the rear. The grip you get becomes marginally better while still gaining all of the weight of the larger wheel and tire. Rotating mass is extremely valuable to us because our cars are so heavy from the get go. Saving as much weight as possible really "outweighs" the need for marginally better grip.

I've seen phenomenal results from 19x10 and 19x11 staggered as well as 19x10 square.

Cheers

 

[949Racing]

Added some more 20" options. Some class regulations may limit wheel width. For others that are more casual HPDE drivers, 11-12" might not be the answer. But yes, for autocross specifically, the widest wheel is usually fastest. Contact patch to weight ratio wins autocross but isn't always the fastest on a road course.

But the poll isn't a "what's fastest?" poll.

 

[kz]

Added some more 20" options. Some class regulations may limit wheel width. For others that are more casual HPDE drivers, 11-12" might not be the answer. But yes, for autocross specifically, the widest wheel is usually fastest. Contact patch to weight ratio wins autocross but isn't always the fastest on a road course.

But the poll isn't a "what's fastest?" poll.

The question is - what do you have to offer I am sure poll is for a reason. Apex is doing pretty well with the wheel offerings for this part of the market.

 

[949Racing]

The question is - what do you have to offer I am sure poll is for a reason. Apex is doing pretty well with the wheel offerings for this part of the market.

We don't current offer and 18-19-20". We have 18" going into production soon and have plans for 19-20" early next year. We're quite aware of Apex and they are definitely aware of us They formed their company a year or two after we incorporated and have followed a similar path. We branched out in to our ow line of brake, engine and suspension products for Miatas early on. After about a 5 year hiatus from wheel production, we're circling back to re-enter the market.

We're a very small company that doesn't always have the resources to launch 10-20 new fitments at once. We will roll them out a few at a time. The poll certainly helps us prioritize.

 

[kz]

We don't current offer and 18-19-20". We have 18" going into production soon and have plans for 19-20" early next year. We're quite aware of Apex and they are definitely aware of us They formed their company a year or two after we incorporated and have followed a similar path. We branched out in to our ow line of brake, engine and suspension products for Miatas early on. After about a 5 year hiatus from wheel production, we're circling back to re-enter the market.

We're a very small company that doesn't always have the resources to launch 10-20 new fitments at once. We will roll them out a few at a time. The poll certainly helps us prioritize.

Hopefully you get reasonable data.
I'd say for me important thing wheels being hub centric and not a large universal bore diameter requiring centering rings - which is what is nice about Apex offerings.
I think 18x11" and 19x11" ET50ish wheels that are reasonably lightweight and don't cost million dollars would find interest.

 

[949Racing]

Hopefully you get reasonable data.
I'd say for me important thing wheels being hub centric and not a large universal bore diameter requiring centering rings - which is what is nice about Apex offerings.
I think 18x11" and 19x11" ET50ish wheels that are reasonably lightweight and don't cost million dollars would find interest.

Yup, wide 18's coming first.

Actually, hub rings serve no function once the wheel is torqued down. They do make installation a bit easier. Round wheels that are concentric with the the BCD eliminate vibration, not hub rings. All 949 Racing wheels use common hub center bores and can accept standard size hub rings for those that want them. Enkei, Rays, BBS, Weds all use standard hub center bores and not application specific bores.

For what it's worth, if you are going to use hub center rings on a track or autocross car, they must be aluminum. Plastic rings will melt

 

[mavisky]

19x11 square to clear the GT350 brakes. If someone made a good tire wide enough to make use of them for autocross I'd run 19x12 square.

 

[949Racing]

19x11 square to clear the GT350 brakes. If someone made a good tire wide enough to make use of them for autocross I'd run 19x12 square.

Added option. Surprised I forgot that as that's what we ran our our GT350. oops

 

[Jstang23]

Added some more 20" options. Some class regulations may limit wheel width. For others that are more casual HPDE drivers, 11-12" might not be the answer. But yes, for autocross specifically, the widest wheel is usually fastest. Contact patch to weight ratio wins autocross but isn't always the fastest on a road course.

But the poll isn't a "what's fastest?" poll.

Again, no widest is not always the answer. Its incredible to me the amount of people that don't understand the physics behind contact patch, slip angle, sidewall strength, etc. A wider wheel might have a larger contact patch and strong enough sidewall. In fact some tires on an 11 inch wheel have a smaller useable contact patch than their 10 inch relative. Not to mention their are fewer tire options for 12 inch wheels. There is absolutely a happy medium. Even in autocross where weight doesn't play as big of a roll as with road courses, you could actually suffer from too wide of a wheel, poorer turning radius, snap off oversteer, unable to get tires to temp. Its also quite common for people to step up to a wider tire and not learn the proper driving technique, further enforcing poor driving skill. There is a reason most race instructors don't allow their students to race with slicks in the beginning. In addition to many of the classes people run, CAM-C etc. have wheel size restrictions.

 

[kz]

Again, no widest is not always the answer. Its incredible to me the amount of people that don't understand the physics behind contact patch, slip angle, sidewall strength, etc. A wider wheel might have a larger contact patch and strong enough sidewall. In fact some tires on an 11 inch wheel have a smaller useable contact patch than their 10 inch relative. Not to mention their are fewer tire options for 12 inch wheels. There is absolutely a happy medium. Even in autocross where weight doesn't play as big of a roll as with road courses, you could actually suffer from too wide of a wheel, poorer turning radius, snap off oversteer, unable to get tires to temp. Its also quite common for people to step up to a wider tire and not learn the proper driving technique, further enforcing poor driving skill. There is a reason most race instructors don't allow their students to race with slicks in the beginning. In addition to many of the classes people run, CAM-C etc. have wheel size restrictions.

CAM-C does not have a wheel width restriction. I've been running in CAM-C for 4 years now.
In fact one of the fastest CAM-C drivers run 295/35R18 Bridgestone on 12" wide wheel. So great story, really.

 

[Jstang23]

CAM-C does not have a wheel width restriction. I've been running in CAM-C for 4 years now.
In fact one of the fastest CAM-C drivers run 295/35R18 Bridgestone on 12" wide wheel. So great story, really.

You do realize running a 295 on 12 inch wheel is extremely stretched right Not even using the full potential of the 12 inch wheel.

 

[949Racing]

The poll is meant to give us an idea of what you folks are shopping for. Not intended as a debate on what the "best" size is. But since we're debating it anyways

There is absolutely a finite maximum optimal width depending on use case. i.e, there is a such a thing as too wide

Radials will develop their maximum lateral grip at a certain slip angle, typically 1-2°. They will develop less grip if they are at zero slip angle. It takes a bunch more power to push a tire across the ground at any given slip angle than it does at zero slip angle. Just basic tire physics. This power demand is key top understanding set up.

One key variable is minimum corner speed, the lowest speed the vehicle sees during a turn. For tuning, we look at both the min and max (fastest and slowest turns) but primarily the average min corner speed. For autocross, the mins run from about 20 to 70mph, the average being about 45mph. For road courses, the min-max is more like 35-120 with an average of about 80mph. A key component is that autocross does not have long straights that have a big effect on lap time the way road courses do. The optimum tire size is one that the car has enough power to keep the tire at that slip angle on all the most important turns. For autocross, that's basically every turn since they're all about the same min speed. For road course, the fastest turns are where lap time is made up. You can afford to be overpowering your tires in the low speed turns on a road course. You just modulate throttle. But if you have so much tire that you can't maintain the slip angle of all four tires in the fast turns, you'll generally be a tick faster on the next size down tire.

This is why a stock S550 Ecoboost would want 335's for Autocross but maybe only 275 or 295 for a fast rad course. Vehicle weight matters too as a wider tire dissipates heat but just running a tire that's too wide to lower tread temps doesn't always result in a lower lap time.

So we're not implying that everyone needs narrower tires. Only clarifying that in some cases, that extra 1-2" of width might not be lowering your lap times as much as you think. The thing to look for is tread temps and handling balance. If you're getting good temps across the tread on the loaded side of the car and it rotates the way you want in the fastest turns, you're probably OK. If it understeers like a pig and your tire temps are low, you might have a bit too much tire. If you can easily drive through the fastest turns on a road course and almost feel likes its bogging down, you might have too much tire.

Most S550/650's are going to be fastest in autocross with 11 or 12" wheels all round. For track, some lighter cars with less power might be a tick faster on some tracks with a 10/10 or 10/11 setup. But competition has rules and depending on your organization, you might be stuck with a smaller wheel or limited by fender clearance with your chose alignment.

Matching wheel to tire width:
The general rule for max grip and performance is wheel width should be equal to , or slightly wider than actual tread width. "actual tread width" is the key here. Not the casing width and not the number stamped on the sidewall. Look up the tread width specs or measure the tire you plan to run, choose the wheel width that matches. Round up if say your tire is 9.8" tread width, choose a 10" wheel. Choosing a narrower wheel still works fine but gives up some steering linearity, feedback and peak grip.

Here is our FAQ on tire pyrometers and setting pressures

Sponsored