F Stock / Autocross R compounds

[Rapid]

I have a budget for dedicated wheels and tires for this season in F Stock. I can find either 18 or 19 inch stock GT wheels. Hoosiers or Khumo, 18 or 19?

Looks like I should stay pretty close to stock on width, 245 / 45, so the side wall will stay stiff.

The car is a 2010 GT with stock 19 inch wheels and tires.

They did not put 17s on the 2010 GTs so they are not an option.


Thanks for your thoughts.

 

[Cone Sweeper]

Depends on how big your pockets are to be honest. 18's to 19's in a bit of a difference for the price of a rim as well as the tires. I'd go with some 18's and go that route.

 

[jayel579]

Youll want to go as big as you can, especially for autocross but then again it depends on your budget. If the 17" wheels werent available on your car then I would go with an 18" rim and find tires from there. 19" r-comps are just stupid expensive. Nice thing about Ho-Ho's is they are made in just about any size, Kumho's are a little more select. Presonally I do not have the budget to run Hoosier A6's, they wear out to quickly; so I run Kumho V710. Kumho's can last a full season (150+ runs), unlike a Ho-Ho though not as fast.

 

[Vapour Trails]

Youll want to go as big as you can, especially for autocross but then again it depends on your budget. If the 17" wheels werent available on your car then I would go with an 18" rim and find tires from there. 19" r-comps are just stupid expensive. Nice thing about Ho-Ho's is they are made in just about any size, Kumho's are a little more select. Presonally I do not have the budget to run Hoosier A6's, they wear out to quickly; so I run Kumho V710. Kumho's can last a full season (150+ runs), unlike a Ho-Ho though not as fast.

I agree with everything said here. As much tire as you can stuff on the rim! A friend of mine runs 275/40/17 V710s on an 8" rim.

I also use V710s because they live longer and I am not a rich man.

Also, just because your car came with 19s, shouldn't mean you couldn't use a 17" wheel. As long as you have stock GT brakes, fitment should not be an issue.

Tirerack carries A6/V710, I'd check the available sizes.

 

[Sam Strano]

I have a budget for dedicated wheels and tires for this season in F Stock. I can find either 18 or 19 inch stock GT wheels. Hoosiers or Khumo, 18 or 19?

Looks like I should stay pretty close to stock on width, 245 / 45, so the side wall will stay stiff.

The car is a 2010 GT with stock 19 inch wheels and tires.

They did not put 17s on the 2010 GTs so they are not an option.


Thanks for your thoughts.

Just be aware that you can only run the size wheels that were an option on your car. Just saying, if you have a package that only came with 18's, you can't legally run a 19" wheel unless the car was able to be ordered that way from Ford----and vice-versa.... if it came with 19's as part of a package from Ford, then you can't run 18's. And whatever wheel you run must be the same width and the offset can only vary from stock by 1/4".

My 2011 is a Brembo car. Came with 19x9's, lots of other Mustangs in '11 came with other sized wheels. But because my car is Brembo car in FS I can't run anything but a 19x9" with an offset within 1/4" of 42mm as no other wheel was an option for my car. If I had a non-Brembo car than could run 18x8, or 19x8.5 as they were options on those cars...... Those cars can't run the 19x9's as they weren't an option for them.

In a way, it's simple--in a way it's hard to get because of the number of options on mustangs in general.

Anyway, if you can, then run the 18x8.5's... they cost less than 19's and give a shorter tire, a lower Cg too. Unless you run on sites that are big where the taller 19" might allow you to carry 2nd and not have to go to 3rd (gearing dependent--again I don't know what you have).

Kumho's are certainly the better wearing option. Not quite as quick as Hoosiers, but more tolerant of big slip angles and just more long lasting... you'll probably heat cycle them out before you cord them.

 

[Rapid]

You could add 19s to a Stock GT with out a package. 18s were the base wheel size.

Does that satisfy what you are saying? I can get pretty confused reading the rules.

I can also ask our local SCCA tech guy I suppose.

Thanks!

 

[Rapid]

Another question.

Khumos require shaving before running? I don't understand why they are manufactured with tread that has to be removed.

 

[Sam Strano]

Another question.

Khumos require shaving before running? I don't understand why they are manufactured with tread that has to be removed.

Depends on which Kumho's.... V700's are faster if you shave them (last a little longer too). V710's need no shaving.

As for the wheels, I seem to recall maybe we discussed this before. Did your car come on 19's? Did you option them, or were they standard as part of your package? If you optioned them then you can run a stock sized 18". If they were part some package that is on the car, then you need to run the 19's to be legal.... that's of course if you really care about being legal.

 

[Rapid]

Yes. I really do care.

The window sticker reads:

19" Premium Painted Wheel 895.00

The strut bar was included when the 19s were ordered.

Is that the kicker? Running 18s with the bar?

Thanks again for the info.

 

[Rapid]

If I remove the strut bar for competition weekends, I would then meet the rlues with 18 inch wheels and tires.

Would I hurt my overall performance with 18s and no bar?

This seem to be an overall less expensive altenative cause there are more 18 inch tires out there.

Seems like 19s and the bar would be faster. Tire Rack is out of 235/35 19 Hoosiers. Any other distributors to consider?

So lost.....

 

[SoundGuyDave]

Well, I can give you a little bit of data... I REGULARLY pull 0.5G on accel, 1.1G on decel, and 1.4G lateral, and have no strut-tower brace at all. 275/35-18 Hoosiers... I would pull the brace, and go 18" in a heartbeat. Better tire selection, lower cost, and no benefit from the part that causes all the hoopla. For Hoosier tires, check out Phil's Tire Service or Havoc Motorsports.

 

[HareBrained]

In stock autocross, the tire mass is probably the most significant allowable modification. You need to go as wide as necessary and as light as possible. In the Grassroot Motorsports articles about their STR Miata, a 245/17 wheel/tire combo was 0.5 sec faster on a 45sec course than the class legal 255/18. The Miata obviously couldn't make use of the extra width but responded well to the 6 lbs less per corner. As a corollary to that, Strano won the FS National Championship on 19" wheels ... so they don't have to be slow.

Just some food for thought. BTW, have you upgraded your shocks, brake pads, and other allowable mods? The thing I found hardest was arriving at the site with a low tank. That takes more planning than I wanted to put into it.

 

[Rapid]

I have doen nothing yet but add negitive camber which helped a lot more than I would have thought.

The tires being the most significant allowable change is what I am doing first.

I will add pads before the next season starts and Koni yellows when the budget is built back up.

Thanks for all of the help!

 

[Sam Strano]

Ok, 19's are an option... but not stand-alone. Which means if you want to run 18's, anything that was added because of the 19" wheels must go. So if the STB is the only thing that was added then if you take it off, you can legally run a *stock sized* 18" wheel.

As for sizes, you need to go bigger than 235, 245... The car works better and is faster with "oversized" tires on a "too small" rim. I tested 275, 285, and 295 18's on the Shelby and my Mustang GT (the 'old '07) and the 275 was the slowest. FWIW, all these were on 18x8.5" rims. The 285 and 295's were faster, largely because they were much smaller in height helping gearing and lowering the Cg significantly. The car transitioned hugely better. Ultimately I preferred the feel of the 295 over the 285, so I stayed with that.

 

[Rapid]

Great!

I now have a plan.

Thanks again.

 

[latch5]

Sam - 295s fit on the front without issue?

 

[Sam Strano]

I've had 295/30-18's on the Shelby on 18x8.5" wheels, stock offset. I've had them on my old '07 on 18x10" wheels, 45 offset. I've had 295/30-19's on my '11 on 19x9's both 40 and 42mm offset. No trouble in any case.

 

[latch5]

I have been running 235 or 245s on what I think are stock mustang 17" rims. The rims look to be 9" wide (but I have already proven on this forum that my measuring skills are questionable at times). Can anyone advise if ford made a 17 X 9" for the S197 - if so does any one have the weight?
After shopping the prices of track tires, it seems financially prudent to stay with 17s as 295 and 285 are readily available. Anyone using these rims for track duty? Tire size recommendations?

 

[jayel579]

The stock OE S197 17's are 17x8. They weight around 25 lbs I believe. I have read that the Cobra R rims, which are 17x9, will mount right up without any fitment issues. If you are going with a 17" rim, IMO the best tire size and most cost effective is a 275/40/17. They will fit a lot better on a 17x9 then a 17x8.

 

[Sam Strano]

I have been running 235 or 245s on what I think are stock mustang 17" rims. The rims look to be 9" wide (but I have already proven on this forum that my measuring skills are questionable at times). Can anyone advise if ford made a 17 X 9" for the S197 - if so does any one have the weight?
After shopping the prices of track tires, it seems financially prudent to stay with 17s as 295 and 285 are readily available. Anyone using these rims for track duty? Tire size recommendations?

Ford did not make a 17x9 stock for S197..... you have 17x8's. I'd recommend a 275/40 on stock 17x8's.