[Chas325]

Swapped to winter wheels today and realised that I bought the wrong tyres for the back wheels. So I’ve got 225/45 up front and 225/40 on the back... do I need to change them urgently or will it be ok for now - 325d m sport on 400m wheels for winter

[teaston]

Could affect the speedo but as long as it's not Xdrive there shouldn't be any problems, although it's not ideal.

[robbiep]

It's a 3.5% difference. Certainly not ideal, though it shouldn't cause any damage if the car is sDrive.
xDrive would be a different matter though.

[HighlandPete]

Originally Posted by robbiep

It's a 3.5% difference. Certainly not ideal, though it shouldn't cause any damage if the car is sDrive.
xDrive would be a different matter though.

BMW (from memory) used to say no more than +/- 1.5% variation from the standard tyre sizing.

This applies for ABS control function. DSC allows tyre logic tolerance of 3 - 4% for the ASC, without loss of performance on RWD models.

ABS is more critical in winter conditions, look out for irregular and/or unexpected ABS/DSC intervention.

[sensible]

This is how the tyre sizes differ, assuming they are 18"

[Chas325]

As I thought. I’m a numpty. Looks like I’m buying 2 more on Monday then!

[Chas325]

Correct size ordered for delivery Tuesday - thanks guys

[crazyoll]

Sorry to jump onto another thread however, I didnt want to add yet another winter tyre query thread.
I've got myself a nice new set of 18" wheel for winter - 8 & 8.5 in.
I'm getting Continentals to go on them but wondered if fitting 225,60's and 255,55's would be an issue?
Also, with that much sidewall, it has potential to look like a landrover OR go the other way and fill the arches nicely.
Anyone have any experience fitting large tyres to an F3X?

The backup plan is to fit 225,45's and 255,40's
Price form tyreleader looks alright.
Any help appreciated.

[sensible]

Firstly....you are joking, right?

225 60 18 is defiantly the wrong size. The wheels will be too big with a completely different rolling circumference than your originals.

60 is the percentage od the width, so you are getting a sidewall 60% of 225 = 135 mm , as opposed to 45% of 225 which is 101 mm

[crazyoll]

Cheers,
Thats what I thought. Worth asking though.
Update, I cant seem to find 255,40's that match the fronts (TS850P) Do you reckon fitting 45's bot fornt and back would be alright?

[sensible]

Originally Posted by crazyoll

Cheers,
Thats what I thought. Worth asking though.
Update, I cant seem to find 255,40's that match the fronts (TS850P) Do you reckon fitting 45's bot fornt and back would be alright?

255''s are not the ideal size for an 8.5j wheel anyway they are slightly oversized but acceptable for the wheel.

BMW recommend 225 45 18 all round for a winter tyre but that isn't ideal for that size wheel either as it is one of the smallest tyres for that wheel....but again it is acceptable for that wheel size.

I decided to stick with what is said on my plate inside the door with 8j fronts and 8.5j rears.

(M + S stands for mud and snow....winter tyre)

[sensible]

Originally Posted by crazyoll

Cheers,
Thats what I thought. Worth asking though.
Update, I cant seem to find 255,40's that match the fronts (TS850P) Do you reckon fitting 45's bot fornt and back would be alright?

No that's not a good match either.

245 40 R18 is a good match and a better tyre size for an 8.5j wheel if you are set on having bigger rear tyres.

[teaston]

Originally Posted by crazyoll

Cheers,
Thats what I thought. Worth asking though.
Update, I cant seem to find 255,40's that match the fronts (TS850P) Do you reckon fitting 45's bot fornt and back would be alright?

I couldn’t get my tyre of choice in 255 either (Dunlop winter sport 5), so I put 245/40’s on the rear, and will get the same for the front when they need replacing.

[sensible]

Originally Posted by teaston

I couldn’t get my tyre of choice in 255 either (Dunlop winter sport 5), so I put 245/40’s on the rear, and will get the same for the front when they need replacing.

Wouldn't the 245''s on the rear and 225' work much better that 245 all round considering the fronts are on 8j wheels and they are wide for front tyres?

[teaston]

Originally Posted by sensible

Wouldn't the 245''s on the rear and 225' work much better that 245 all round considering the fronts are on 8j wheels?

Yea you could do that as well, 245's are fine on 8j wheels though.

[Hooded]

How about 235/45/18 on an 8.5j for winter tyres?

[sensible]

Originally Posted by Hooded

How about 235/45/18 on an 8.5j for winter tyres?

The tyre size is 1.36% bigger than the OEM size but that is in acceptable limits so would work. It's probably a better tyre size for the 8.5j wheel than the 225 too.

[Hooded]

Originally Posted by sensible

The tyre size is 1.36% bigger than the OEM size but that is in acceptable limits so would work. It's probably a better tyre size for the 8.5j wheel than the 225 too.

That's what I was thinking. Seems the closest you can get to 255/40/18 rears in Michelin crossclimates. The Tyre calculater I used shows only a 1mph difference at 90mph too.

[teaston]

Originally Posted by Hooded

How about 235/45/18 on an 8.5j for winter tyres?

They will have 8mm higher side walls than 245/40’s, so for that reason I’d stick with 245/40’s, the side walls are already pretty large.

[Hooded]

Originally Posted by teaston

They will have 8mm higher side walls than 245/40’s, so for that reason I’d stick with 245/40’s, the side walls are already pretty large.

Unfortunately they don't do cross climates in 245/40/18, ...235/45/18 is the closest they do to 255/40/18
The circumference is only 1inch difference

[sensible]

Originally Posted by Hooded

Unfortunately they don't do cross climates in 245/40/18, ...235/45/18 is the closest they do to 255/40/18
The circumference is only 1inch difference

So your not going for 'winter tyres' then....Cross climates are All Season tyres for all year round. Good tyres if you plan to leave them on all the time, but not as good as having winter tyres and summer tyres.

[Hooded]

Originally Posted by sensible

So your not going for 'winter tyres' then....Cross climates are All Season tyres for all year round.

Yes I only use one set of wheels and the cross climates are the best compromise for uk weather. More like a summer tyre but with close to winter tyre snow traction to keep you moving when we get occasional snow.
I use them on my 320d and have been very impressed with them, comparable performance in the summer to the continental run flats I had on before and were very good in the snow we just had in the West Midlands.

I'm just sizing them up for the 18" m sport wheels I'll most likely have on the 330/335d I buy soon. 225/45/18 fronts and 255/40/18 rears .. closest I can get for the 8.5j rear wheels is 235/45/18 in cross climates.