twistedneck

I'm going to try and get the fatter tire for more rear grip. Will that big boy fit on a typical brembo package rim? i think the wheels are only 9" wide not 9.5" like the Laguna / Boss and may not handle the wider 285 / 35 R19.


In the process of stiffening the rear by adding 26mm stabilizer bar, and i think w/o the larger rear tire it will have too much oversteer. Thoughts? Stock is 24mm for the bbp, 25mm for boss.

Thanks!

99mstng

go with a 275/35 . . . 285 on a 9" rim would "fit" but I wouldn't run it

also you can do 275 all the way around so you can rotate your tires

twistedneck

thats what i was wondering thank you. the wider tire in back had a function of gaining back rear grip counteracting the huge 26mm laguna rear bar swap out. i dont know if ford also knew it needed even more rear grip because they also pitched the body forward for more turn in. seems like laguna is a track full of understeer and thats what it took


however the spring rates are much lower in bbp..


but yea then i cant rotate this hides

Dave07997S

275's are widest you would want to go, even that won't be optimal. Yes a 275 is the max for a 9" rim but it isn't optimal, which would be 9.5". The minimum rim width for most tires in the 285 width is going to be 9.5" with 10" wide optimum.

Dave

twistedneck

that sounds bad.. what happens when you put a 275 on a 9" rim??

300AGT

I have a brembo GT i went with P275-40 19" on the stock rims in the back and keep the stock 255-40 19" in the front .I think twice before going up to the 26 mm rear bar.I try the car with the tire set-up you pick first before changing the rear bar .

LagunaBeach

The Brembo wheels are 19x9.5, and 285 tires do fit just fine on them.

jsnyng

What problem are you trying to fix with a 26mm rear bar? I stepped DOWN to a 22mm adjustable because snap oversteer was such a problem for me with the 24mm.

jsnyng

Wrong. They are 19x9, and while a 285 may fit it is definitely not optimal.

LagunaBeach

You're right, got my wheel sizes mixed up.

jsnyng

No worries my friend.

bob

If its in an acceptable rim width range then its not so much as bad as it changes the way the tire reacts under a load. Generally speaking it would reduce the lateral stiffness in the sidewall changing the way the tire reacts (slower and softer) compared to a tire where the rim is equal to or wider that than the reccomended fitment. There is also a very minimal effect on the section width of the tire and possibly its contact patch.

At the very least your introducing yet another variable into tuning the suspension

twistedneck

i want to enhance and increase roll couple to the max. you are right there is no vehicle model to simulate snap oversteer!! hmmm but the big bars must help or boss and laguna would not need. of course many other things like springs cloud.

twistedneck

After doing more research it looks like the reason there was a 26mm bar had to do with the extreme grip provided by the 285 tires on Laguna, along with its x-brace it had so much rear grip they needed to loosen it up by adding a huge rear stabar.

I will stick with a 25mm boss rear stabar to replace my 24mm and hopefully that will add just a little bit of oversteer and body roll reduction to make the car easier to toss w/o going into 'snap oversteer' ouch.

The quote below from chief engineer essentially spells this out. Whats up with that ultra grippy rear tire?

Five Oh Brian

Every 2003-4 SVT Cobra left the factory on 9" wide rims wearing 275's at all 4 corners. I trust that SVT wouldn't have done so if it was a bad idea.

I'll be running 275's on my '11 BBP GT when the factory tires wear out without any worries.

bob

275/40R18's IIRC - Its not quite a simple as just saying 275's on 9" rims since the aspect ratio dicates the approved rim widths for the tire. That 5% difference in sidewall changes the character of the tire completely.

All about the G's and being able to get the power down without seeing it going up in a blue haze as you get on the throttle real early.

Gabe

The 03 Cobra came with 275/40R17's on 9" wide rims ... I have one in the shop now and paid close attention to the tire/rim sizes listed on the warranty (OASIS) printout when I printed the Repair order this morning ... factory-fit was 17x9 rims, 275/40R17 tires.

bob

17's then, I couldn't remeber exactly, but again the issue isn't so much that SVT decided to run 17 x 9's with 275/40R17's which is great as it pertains to a Terminator however in the case of the S-197, running a 9 x 19 rim with a 275/35R19 is something altogether different by dint of the shorter sidewall. Your talking half an inch difference between the two sidewalls with the 275/35 obviously being shorter even though the 275/35R19 is about 1 inch larger in OD.

Even in the case of the Terminator, a 17 x 9 rim was sub-optimal as the measuring rim width used at least in the case of Michelin was 17 and 19 x 9.5 rendering a section width (from sidewall to sidewall) of 10.9" which could be thought of as providing the best compromise between ride comfort, road holding and steering response. Going toward the 9 inch rim favors ride comfort over road holding and steering repsonse. Going to 10-11 rim will sharpen steering repsonse and increase lateral stiffness at the cost of ride comfort.

Thats why you see the GT500 and Boss riding on 255/40R19s with 19 x 9.5" wheels up front.

11SHELBYGT500

285 mm is more than 11inches wide and with that low of a profile, you can't safely put that on a 9inch wheel.

Gabe

I use 1010tires.com a lot for their tire size calculator ( http://www.1010tires.com/tiresizecalculator.asp ) and they list rim width range of 9-11" for a 285/35R19 tire ...



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