Does the X5M brakes fit to X5 4.8i?

[blue dragon]

Yes, the shape of the contact patch changes, but not the size.

[JCL]

Size of the contact patch is, at the highest level, not directly a function of profile. However, it is related to the strength or stiffness of the sidewall, and lower profile tires have stiffer sidewalls by design. You can have larger or smaller contact patches with lower profile tires, depending on all the other variables. But the contact patch will always be a different shape than with a higher profile tire.

I would say that race teams went to lower profile tires so that they could manage thermodynamic effects. Lower profile tires turn in better (stiffer sidewalls) but they don't necessarily have better cornering, that is a function of what temperature you can get the tire to, and the compound being used. Back to heat effects.

Also, it depends on what type of racing you are talking about. Road courses with lots of corners brings a focus to turn-in and lateral grip. Drag racers worry about traction, and they will go to higher profile tires to improve traction.

[ard]

Originally Posted by JCL

Size of the contact patch is, at the highest level, not directly a function of profile. However, it is related to the strength or stiffness of the sidewall, and lower profile tires have stiffer sidewalls by design. You can have larger or smaller contact patches with lower profile tires, depending on all the other variables. But the contact patch will always be a different shape than with a higher profile tire.

I would say that race teams went to lower profile tires so that they could manage thermodynamic effects. Lower profile tires turn in better (stiffer sidewalls) but they don't necessarily have better cornering, that is a function of what temperature you can get the tire to, and the compound being used. Back to heat effects.

Also, it depends on what type of racing you are talking about. Road courses with lots of corners brings a focus to turn-in and lateral grip. Drag racers worry about traction, and they will go to higher profile tires to improve traction.

People way smarter than us have written extensively on tires... There are some very good white papers floating avout...The whole concept of 'lower profile equals stiffer sidewalks equals better handling" is only part of the equation, as dynamic slip and the ability of the contact patch to actually conform to the road surface as you turn can be compromised with lower profiles.

[dimis55]

Teff, back to the original question. i just got a 13' X5M and have a 21' 128 wheel set from the previous x5 i had. i wanted to put the 21' rims on the new M. The rear rim fits no problem, even though i had to use a centric ring, but the front rim will not even set onto the hub because the M caliper is too big. Its not a height problem, but the caliper is so fat that it bumps into rim. So if you upgrade the brakes, you'll probably have to change wheels as well to accommodate the caliper, not just diameter size, but design as well.

[X5X]

Originally Posted by dimis55

Teff, back to the original question. i just got a 13' X5M and have a 21' 128 wheel set from the previous x5 i had. i wanted to put the 21' rims on the new M. The rear rim fits no problem, even though i had to use a centric ring, but the front rim will not even set onto the hub because the M caliper is too big. Its not a height problem, but the caliper is so fat that it bumps into rim. So if you upgrade the brakes, you'll probably have to change wheels as well to accommodate the caliper, not just diameter size, but design as well.

Have you tried spacers?

[dimis55]

I think spacers could solve the problem, but not to keen on putting 15 plus mm spacers on. They really weren't even close to fitting

[95wildtt]

Does anyone happen to know if 214s will clear the larger calipers in the front? I'm seriously thinking of doing this when my brakes need to be serviced in 20k miles, but I want to understand what I'm in for...

Do the M and non-M X5s (I have a 2008 4.8i) use all of the same brake system components, other than the obvious calipers and rotors?

Thanks...

[blue dragon]

^^ I would think the stability control systems are different too.

[mavic1010]

They will clear 214s. Someone on the board overseas did this. I also have a set of X5M calipers that I will be putting on my e70. Just waiting to get them painted.

[95wildtt]

I also have a set of X5M calipers that I will be putting on my e70. Just waiting to get them painted.

Do you have 214s, and will you be going to larger rotors as well?