2 Questions re rubbing and Traction Control

[GregSM3]

Apex ec-7 - Frt. 19x9.5 et22 with PS4 275/35/19 and
Rear 19x11 et44 305/30/19.
So works out to be .3" taller in frt = 1.1% diff and .5" shorter diam in the rear which is 1.9%. Stock is .4" taller rear to frt and with my suggestion would be .4" shorter rear to frt.

I have eibach springs with Bilsteins. So slight lowering from stock not much.

So question will this rub? AND will this mess up Traction Control?

Thanks for the help!

[x.shell]

Originally Posted by GregSM3

Apex ec-7 - Frt. 19x9.5 et22 with PS4 275/35/19 and
Rear 19x11 et44 305/30/19.
So works out to be .3" taller in frt = 1.1% diff and .5" shorter diam in the rear which is 1.9%. Stock is .4" taller rear to frt and with my suggestion would be .4" shorter rear to frt.

I have eibach springs with Bilsteins. So slight lowering from stock not much.

So question will this rub? AND will this mess up Traction Control?

Thanks for the help!

Will not rub suspenion -- as long as the Bilstein spring perch is in the same location as the OEM perch. The key is that the perch has to sit ABOVE the tire.

May rub the fender liner on full lock. Yes.

Mess up traction control? Yes.

If you are worried about Traction Control not working properly, then you should go with a 275/30/19 for the front.

If you don't really care about TC too much, I'd still go for a 265/35/19 on the font -- at least the overall diameter will be the same you keep the 305/30/19 rear.

[GregSM3]

x.shell - thanks for info. Sorry a bit confused, agree the 265/35/19 is same wheel diameter as stock, why would that impact TC and the 275/30/19 which is not same is about .8" less than stock diameter?

[x.shell]

Originally Posted by GregSM3

x.shell - thanks for info. Sorry a bit confused, agree the 265/35/19 is same wheel diameter as stock, why would that impact TC and the 275/30/19 which is not same is about .8" less than stock diameter?

TC is programed to your OEM tire's diameter stagger. OEM tires have a smaller diameter on the fronts vs the rears -- the closer you get to that stagger ratio, the better. TC issues aren't due to the actual diameters of the tires -- they issues happen when the front/rear diameter ratio is off.

And I didn't say 265/35/19 is the same diameter as stock -- it isn't. I was referring to it being the same overall diameter as a 305/30/19. So with that set up, you'll still have TC issues, but not as bad as if you had 275/35/19 front.

[GregSM3]

ahh gotcha so the key is the stagger ratio. So i'm now looking at the ps4 bmw star options, watched the video and seems quite the difference. The G80 comes with 19 frt and 20 rear. As I am buying wheels I could do that as well. if I go with 275/35/19 on frt. What would be good for the rear -looks like it might be 295/35/19 =27.1 diam which is .5 diff. or could do the 295/30/20 which is 27"

[MineralWhiteF80]

Originally Posted by GregSM3

ahh gotcha so the key is the stagger ratio. So i'm now looking at the ps4 bmw star options, watched the video and seems quite the difference. The G80 comes with 19 frt and 20 rear. As I am buying wheels I could do that as well. if I go with 275/35/19 on frt. What would be good for the rear -looks like it might be 295/35/19 =27.1 diam which is .5 diff. or could do the 295/30/20 which is 27"

a 275/35/19 is a little too large for the front fender well of the F8X chassis. Anything over 26.3 inches diameter will rub the fender liner to some extent, and depending on wheel offset and how much the car is lowered (or how much the suspension is compressed) will likely rub the actual fender, front bumper edge, and fender liner. Additional negative camber can help to some degree, but not front and rear fender liner rubbing.

The factory front to rear stagger makes the rear tire 0.6" larger in diameter.

A 265/35/19 pairs best with a 285/35/19 rear tire (actually what I run on the street).

Ideally, best I can recommend is:
Front: Keep tire diameter at 26.3" or less
Rear: Keep tire diameter at 27.1" or less
Keep front to rear stagger as close as possible to where the rear tire is 0.6" larger than the front.

There is some wiggle room and exceptions to the rules, but this is a good starting point. Camber, ride height, actual tire make/model, how the car is driven can definitely change what tire sizes rub and what wont rub.

Also, everything is quite interconnected and defining exactly what your plans are with the car will dictate what suspension you should run, which then dictates the tire width and sizes you should run, which then all dictates the size/width/offset of wheel you need to choose. And hopefully the style of wheel you like comes in those sizes LOL

[GregSM3]

I have Eibach springs and Bilsteins, so a very slight lowering frt and rear from stock. Did a bit more research and found this - From Bosch who make the system:

Dear Mr. ____,

Thank you for your question and interest in our mobility solutions.

The dynamic stability control is very robust, which means that it can cope with all approved tire combinations. Any measurable differences in the tire circumference are detected and compensated by the system. The angular speed of the wheel is corrected without any changes in the application parameter.
Mit freundlichen Grüßen / Best regards

Which also makes sense as I believe a lot of folks use a square set up for winter tires and seem to have no issues. So with that in mind for a performance and look will probably go with 265/35/19 and 305/30/19 which is pretty close to square.

[x.shell]

Originally Posted by GregSM3

I have Eibach springs and Bilsteins, so a very slight lowering frt and rear from stock. Did a bit more research and found this - From Bosch who make the system:

Dear Mr. ____,

Thank you for your question and interest in our mobility solutions.

The dynamic stability control is very robust, which means that it can cope with all approved tire combinations. Any measurable differences in the tire circumference are detected and compensated by the system. The angular speed of the wheel is corrected without any changes in the application parameter.
Mit freundlichen Grüßen / Best regards

Which also makes sense as I believe a lot of folks use a square set up for winter tires and seem to have no issues. So with that in mind for a performance and look will probably go with 265/35/19 and 305/30/19 which is pretty close to square.

The key words you need to pay attention to is "ALL APPROVED TIRE COMBINATIONS". The "compensation" he was talking about refers to the minute differences in sizes from one manufacturer to another manufacturer. For example, a Michelin PS4S will be a different diameter from an RT660, even when they are the same listed sizes.

265/35/19 AND 305/30/19 is not an approved tire combination for any F8X and the TC will bug out a bit when it's pushed. I know because I ran this tire size set up on multiple wheel sets on multiple different brand of tires.

That being said, I think you're over thinking it. TC is good to keep you safe, but if you drive like an a-hole on the street, TC is going to annoy you no matter what.

[GregSM3]

Fair points, I do tend to overthink these things. But still confused on how folks can run square set-ups and not have TC issues. Perhaps they are not driving crazy so does not interfere. Thanks

[mitch32]

I am actually planning to run 275/35/19 and 305/30/19 for track setup as well. The TC is a concern, I wonder if the euro or CS MDM helps the situation. A few important things:

- Apex and everywhere seems to recommend 275/30/19 and 305/30/19 as the proper option but there are almost no options for tires in that combination. If you go 275/35/19 your options greatly open up.
- Currently I am running a 275/30/20 on stock 666m front wheels and KW coilovers with 0 rub, the 275/35/19 are 2.5mm different in diameter which is not significant.
- My current 666m setup 275/30/20 and 295/30/20 setup which has the proper diameter stagger is horribly intrusive on track with the Canadian/USA TC turned on. So intrusive that it's frustrating and sometimes completely downright scary. I honestly do not know what to do with the TC other then turn it off, it also destroys the brake pads if your too aggressive and F8x blue calipers are heat sensitive.

[cliffordm4]

Just wanted to join in since I need to order a new set of tires and am not sure what direction to go in.

I currently run RT660s, 275/30/19 front and 305/30/19 rear on Apex VS5-RS (19x10 ET 25 front, 19x11 ET 44 rear). Even with Euro GTS MDM, TC still gets very very irked, both on and off track.

Stock EDC shocks, lowered on Macht Schnell springs. Using adjustable Turner and SPL arms gets me -2.2 deg camber and 8.8 deg caster. I'm waiting till I get Ohlins to do camber plates, so this is maxed out for now.

I want add some more sidewall to either just the front or both front and rear as well.

I'm considering the following 3 setups (all with RT660, preferably - I would get RE71RS but they don't make anything wider than a 285 for the rear at the moment):

275/35/19 front, 305/30/19 rear

265/35/19 front, 305/30/19 rear

265/35/19 front, 295/35/19 rear

Any thoughts? Anyone try specifically running a 275/35 with the RT660 in the front? I know they run pretty wide... 0.7" more than a Cup 2 in the same size. I don't mind fender liner rub, but don't want to hit the bottom of the strut.