Options on tire size for stock autocross needed

I got a set of 16" exploder rims to put on my Mustang. They are 7" wide. I have 2 tire sizes in mind, a 245/50R16 which would be the max width I can run without modes, and a 225/55R16. They are both slightly smaller in diameter than stock which is what I want. The 245's are at the max of the rim width.

The tires for 245 are Firestone Firehawk Wide Oval Indy 500 which is what I was leaning toward. The 225 has a lot more options.

One more question. In the class I was in last year there were max tire width rules. I could not find any limit on tire width or size, just in wheel width and size for Stock classes.

I messed up the title options should have been opinions.

For Stock/Street class autox, none of the above...Much more competitive rubber compounds are available in 225/50-16.

I'm going to run 225/45/16's Dunlop Direzza's on my Mustang this year. Rims are 16x7's. I wanted to go 245's but price jump and lack of options and the fact that I found these Dunlops used made my decision.

For a 7" wheel, 205/50 or a 225/50 will fit better. 245/50 will be too wide for the best handling setup.

rustysteel wrote: I'm going to run 225/45/16's Dunlop Direzza's on my Mustang this year. Rims are 16x7's. I wanted to go 245's but price jump and lack of options and the fact that I found these Dunlops used made my decision.

This, much better rubber than what you are looking at.

225/50/16 is too wide for a 16" wheel in most "street" tires. DOT R-comp's, I'd consider it.

There's a very good reason I'm going from 225/50/16's this year to 205/55/16's on my 16x7's. Ideally, I'd like to go to a 195/55/16, but there's not much available.

You have to be the only person who wants narrower tires, other than the ones that like to stretch their tires like their pants. Wait, are you wearing skinny jeans right now?

I don't wear pants.

Aside from that, I've merely become aware that wider isn't always better. As I said, with an R-compound, you can get away with REALLY wide widths, much wider than what a typical "street" tire is comfortable with on the same width wheel. Drag, weight, excess area, etc are all factors that I'm trying to 'tune out' with this car, and I've found the 225/50/16 isn't as optimal as say, a 205/55/16 or 195/55/16 would be with a 7" wide wheel. Just take a look at the guys running 195's in ST classes and dominating rather than the 225 width limit on 7.5" wheels. There's more to grip than just adding tire width, and some tires measure out to be MUCH wider than other tires with the same width rating. A lot is dependent on the specific car setup and which tire is used, though, so there's a lot of experimenting to do before you really nail down what works best.

Thanks all, I have decided on BFG g-Force Sport COMP-2 in a 225/55 size. I know going with a smaller diameter will give me more power but I don't want to change that much from what I am used too. I am sure this will stop a lot of the tire squealing I had last year.

beans wrote: Aside from that, I've merely become aware that wider isn't always better. As I said, with an R-compound, you can get away with REALLY wide widths, much wider than what a typical "street" tire is comfortable with on the same width wheel. Drag, weight, excess area, etc are all factors that I'm trying to 'tune out' with this car, and I've found the 225/50/16 isn't as optimal as say, a 205/55/16 or 195/55/16 would be with a 7" wide wheel. Just take a look at the guys running 195's in ST classes and dominating rather than the 225 width limit on 7.5" wheels. There's more to grip than just adding tire width, and some tires measure out to be MUCH wider than other tires with the same width rating. A lot is dependent on the specific car setup and which tire is used, though, so there's a lot of experimenting to do before you really nail down what works best.

the ST guys have been running 195's for 2 reasons …

1) they do fit better on 7" rims

2) they are Toyo's (most likely) and have the sticky compound all the way to the cords …. whereas the 205's and 225's change compound at about the 3/32" mark … and the serious auto crossers usually shave their tires to that level to start with …

with 7 1/2" rims you can easily go to 205's and even 225" … the Toyo R1R 225 tread width (per Tire Rack spec sheet) measures 7.8" … .3" wider than the rim … not a real problem

you'll have to check other tire brands for their tread widths to see which fit best on your rims

pjbgravely wrote: Thanks all, I have decided on BFG g-Force Sport COMP-2 in a 225/55 size. I know going with a smaller diameter will give me more power but I don't want to change that much from what I am used too. I am sure this will stop a lot of the tire squealing I had last year.

tire sizes (or brand) won't change anything about the amt. of power your engine makes .. what it will do is change the how quickly the engine can rev … moving the torque curve around a bit … same amt of hp and torque …

On the 195 vs 205 or 225 idea, if the wider sections are not getting up to temperature effectively, using the narrower section COULD get the temps up into the proper range faster. Purely a thought exercise, but it sounds right. That might mean you run the narrow stuff in the cooler temps and the wider stuff as it gets hotter...

wbjones wrote: tire sizes (or brand) won't change anything about the amt. of power your engine makes .. what it will do is change the how quickly the engine can rev … moving the torque curve around a bit … same amt of hp and torque …

Ok you got me, I meant acceleration not power. It will change effective power to the ground via gearing.

Going with narrow tires is moot as there are no summer tread tires in 205 and 215 in the diameter that is close to stock on tire rack.

yep … I've found that to be the case with my CRX … on track I run 13" R-Comps … aids in cornering (wider tires) and helps me dig out of the corners better … combination of tire width and higher rpms on corner exit …

for a-x, I'm on narrower 15" "street" tires … no sticky street tires in 13" plus the gearing advantage on track would be a detriment for a-x