Tyre Sizing Options??

Tyre Sizing Options??

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W8PMC

Original Poster:

3,345 posts

237 months

Friday 26th June 2015
quotequote all
Got another dilemma in my desire to fit Pilot Sport Cup 2's to my F10 M5.

They're available in my OEM front tyre size, that being 265/40/19, however they're not made in my OEM rear tyre size of 295/35/19 & not made in a wider size of 305/35/19.

What is available for the rear however is 295/30/19 so my question is how would this work with 265/40/19 upfront or would i need to drop the depth of the front tyre to a 265/35/19? Would this scenario be safe & not upset the cars dynamics?

I'm fitting H&R springs soon & that will drop the ride height to CP level, that being a drop of 10mm so i need to be sure i'm not going to upset the dynamics of the car.

Thanks in advance for your assistance.

RichardM5

1,733 posts

135 months

Friday 26th June 2015
quotequote all
Going from 295/35 R19 to 295/30 R19 will give you nearly 5% speedo error and drop the ride hight by 14.75mm, that's a lot. I'd not do it.

285/35 R19 would be just 1% speedo error and 3.5 mm reduction in ride height, probably the best option on the stock 19s.

325/30 R19 would be 1.7% speedo error and 5.75mm reduction in ride height, stock rims are a bit narrow for this size and I don't know if it would rub.

W8PMC

Original Poster:

3,345 posts

237 months

Friday 26th June 2015
quotequote all
RichardM5 said:
Going from 295/35 R19 to 295/30 R19 will give you nearly 5% speedo error and drop the ride hight by 14.75mm, that's a lot. I'd not do it.

285/35 R19 would be just 1% speedo error and 3.5 mm reduction in ride height, probably the best option on the stock 19s.

325/30 R19 would be 1.7% speedo error and 5.75mm reduction in ride height, stock rims are a bit narrow for this size and I don't know if it would rub.
Wow, i'd not have imagined such a drop with only a small change to the profile.

Would this difference be dialled out if i reduce the front profile from a 40 to a 35?

So want to try out Cup Sport 2's on track later this year. Can't find any other track tyre options for the stock sizes & Cup Sport 2's appear the closest.

RichardM5

1,733 posts

135 months

Friday 26th June 2015
quotequote all
You're still getting a ride hight drop (and wheel arch gap gain) by dropping the profile. Reducing both front and rear will be better but you'll still get the speedo error. If you really want to use PS Cup 2 on the stock 19 inch rims then I think the 285/35 R19 is the size to use at the rear.

W8PMC

Original Poster:

3,345 posts

237 months

Monday 29th June 2015
quotequote all
RichardM5 said:
You're still getting a ride hight drop (and wheel arch gap gain) by dropping the profile. Reducing both front and rear will be better but you'll still get the speedo error. If you really want to use PS Cup 2 on the stock 19 inch rims then I think the 285/35 R19 is the size to use at the rear.
Thanks Richard, i'll look into the 285's then. I guess dropping from a 295/285 should be countered with the better on track grip of the Cup Sport 2's.