[MySport]

Could anyone let me know what tyre sizes are fitted to the 21” rims that come as part of the M Sport + pack?
I’m looking to order a M40 in the next couple of weeks, but runnng costs are a consideration as I do 25,000 miles a year. I have priced up the standard 20’s and they’re within budget, but I don’t want to lumber myself with onerous replacement costs if I go for 21’s.
I’m also curious to know if anyone has had experience with regards to their life expectancy.

Thanks.

[skier219]

So far my 21" tires are wearing extremely well, and I don't anticipate them wearing out before I'd expect. You can compare the tread wear ratings of 20" and 21" tire offerings to see if there is a marked difference.

The 21" tires have very limited selection, just a few brands, and the costs are quite a bit higher. So that is a definite downside to going 21".

I think by comparing tread wear ratings and replacement costs, you can come up with a good quantitative decision.

[Dandle]

21" wheels are 275/35R21 and 245/40/21

20" wheels are 275/40R20 and 245/45/20.

The tyres are between £80 to £100 each more expensive in the 21" version in the UK. I've been looking too.

As for tyre life I guess it depends how hard you drive. I don't own one yet but one of the cars I've enquired about one had 12k miles on it and the rear tyres were at 3mm and the fronts at 5mm (fitted with Bridgestone Alenzas).

[verysideways]

Don't forget you can also order the M sport plus pack with the 20's and high performance non-runflat tyres.

[teaston]

Originally Posted by MySport

Could anyone let me know what tyre sizes are fitted to the 21” rims that come as part of the M Sport + pack?
I’m looking to order a M40 in the next couple of weeks, but runnng costs are a consideration as I do 25,000 miles a year. I have priced up the standard 20’s and they’re within budget, but I don’t want to lumber myself with onerous replacement costs if I go for 21’s.
I’m also curious to know if anyone has had experience with regards to their life expectancy.

Thanks.

They are at least £250 each for decent ones, and there's very little choice, hence why I went for the 20's with "high performance tyres" (non RFT's)

[sinbad4]

21" wheels should have no affect on tire life. 21" wheels impact is limited only to tire radius and width. In theory.

Tire life is strongly tied to "UTQG treadwear rating" Lower the number, lower the mileage expected on the tire. Generally, lower rated tires are softer and "stick" better to the road. This also increases road friction. Sport tires typically have a treadwear rating < 320 and generally get < 20,000 miles.

Low wear commuter tires are generally hard and have low road friction. They last much longer. They generally have treadwear ratings >500 and can last well over 30,000 miles.

The, "in theory" part of the wheel size is that, when I looked last fall, I only found soft sport tires available for the 21" 718M wheels were soft, sport tires from 200-320 treadwear rating.

[teaston]

Originally Posted by sinbad4

21" wheels should have no affect on tire life. 21" wheels impact is limited only to tire radius and width. In theory.

Tire life is strongly tired to "UTQG treadwear rating" Lower the number, lower the mileage expected on the tire. Generally, lower rated tires are softer and "stick" better to the road. This also increases road friction. Sport tires typically have a treadwear rating < 320 and generally get < 20,000 miles.

Low wear commuter tires are generally hard and have low road friction. They last much longer. They generally have treadwear ratings >500 and can last well over 30,000 miles.

The, "in theory" part of the tire size is that, when I looked last fall, I only found soft sport tires available for the 21" 718M wheels were soft, sport tires from 200-320 treadwear rating.

Where do you find these tread wear ratings? I don't think I've ever seen them.

[MechX3M40i]

Originally Posted by teaston

Where do you find these tread wear ratings? I don't think I've ever seen them.

The rating should be listed on the sidewall of the tire. You can also find the rating at Bridgestone's website or other online tire stores.

For example, the rear Bridgestone 20" run flat I have is rated 300 A A (treadwear, traction and temperature respectively).

[nvestr]

All tires have a treadwear rating. The number is a percentage of life compared to a reference test tire. For example the reference tire is worn out at 100%. If you have a tire with a treadwear rating of 300, for example, that means your tire should last 3 times longer than the reference tire. That in itself means nothing but if you compare across tires, it can give you an idea of how a tire should wear in perfect conditions (with a perfect alignment) relative to another. It is certainly not a perfect metric.

[teaston]

Originally Posted by MechX3M40i

The rating should be listed on the sidewall of the tire. You can also find the rating at Bridgestone's website or other online tire stores.

For example, the rear Bridgestone 20" run flat I have is rated 300 A A (treadwear, traction and temperature respectively).

I had a look and my P Zero’s do have a wear rating on them! 320

My Goodyear winter tyres and my wife’s Continentals don’t have it though, so I guess it’s just tyres that are supplied to US that have it, which my P Zero’s have as they were fitted in Spartanburg!

[HampshireUK]

It seems there are more non RFT tyre options appearing for 21" especially the rear tyres, lets hope this continues for the fronts..

Love the 21"wheels and their relative exclusivity. Glad I didn't go for 20" wheels and lots of X3 3.0D's appearing in the work car park with those 20" wheels.

[verysideways]

Originally Posted by teaston

I had a look and my P Zero’s do have a wear rating on them! 320

My Goodyear winter tyres and my wife’s Continentals don’t have it though, so I guess it’s just tyres that are supplied to US that have it, which my P Zero’s have as they were fitted in Spartanburg!

All tyres should have treadwear ratings on the sidewall. I'll have a look at mine later.

[i4M50Guy]

Been looking into what I could get to replace the run flats that come with the 21" rims.

Looks like I can get Michelin rears but not the same for the front.

What has everyone else went with?

[nvestr]

Do you absolutely want/need runflats?

[i4M50Guy]

Originally Posted by nvestr

Do you absolutely want/need runflats?

I would much rather it. The tyres will need changed soon anyway so it makes sense to change to normal ones at the same time.

[i4M50Guy]

Will the X3M tyres fit?

[i4M50Guy]

From what I can see the 21" rim widths are 8.5J and 9.5J therefore they should be able to handle a 255 (front) and 275 (rear) maximum tyre width.

Would anyone else agree with this?

M40i 21” Rims
245/40ZR21 100Y Front 8.5J 225min - 235-245reccomended - 255max
275/35ZR21 103Y Rear 9.5J 245min - 255-265reccomended - 275 max

X3M 21” Rims
Front: 255/40ZR21 (102Y) XL
Rear: 265/40ZR21 (105Y) XL

[i4M50Guy]

Can anyone confirm?

[teaston]

Originally Posted by M140iGuy

Can anyone confirm?

Yes they definitely fit, at least a couple of forum members have done it.

[i4M50Guy]

Originally Posted by teaston

Yes they definitely fit, at least a couple of forum members have done it.

Perfect. Thanks.

Seems like the best upgrade then.