WINTER TYRES

[md23]

Hi All

Currently trying to get SWMBO mobile in this weather! Can't get a delivery date for BMW winter wheel/tyre set and the dealer was useless when I asked them this question!

So, I have a spare set of OEM wheels for her indoors 320d M Sport (17 inch). The OEM tyre sizes are 255/40/17 (rear) and 225/45/17 (front). What I'm not sure of is what size tyres I could get away with. Obviously I could try to get the OEM sizes but could I, for example, drop to 245 (or 235)/45 and 205/50? Delivery is the main problem so potentially looking at Fleabay hence would be useful to know what I could get away with. Would 45's all round work (notwithstanding the fact that the speedo might be slightly out).

Thanks in advance!

m

[cslwannabe]

I'd go with 225/45/17 front and rear as the difference in rolling radius is negligible (0.75mm) (thats what I used on my E46 330Ci, despite it being a sport model with wider rears as std (18s)? Plus means you can swap the fronts and rears next time.

I'd try mytyres or Reifen (german website but select the Union Jack). Costco worth a try if you're a member. This time last year I still had 2 complete sets of wheels plus tyres but have since sold them.

Edited by cslwannabe on Tuesday 7th December 14:07

[Zod]

The handbook will give you the official winter tyre and wheel sizes.

(or at least mine always have)

[ghibbett]

cslwannabe said:

I'd go with 225/45/17 front and rear as the difference in rolling radius is negligible (0.75mm) (thats what I used on my E46 330Ci, despite it being a sport model with wider rears as std (18s)? Plus means you can swap the fronts and rears next time.

Same as I have on my 330i Sport. Personally think they're better than the Summers too....

[md23]

ghibbett said:

cslwannabe said:

I'd go with 225/45/17 front and rear as the difference in rolling radius is negligible (0.75mm) (thats what I used on my E46 330Ci, despite it being a sport model with wider rears as std (18s)? Plus means you can swap the fronts and rears next time.

Same as I have on my 330i Sport. Personally think they're better than the Summers too....

This thought had crossed my mind but wasn't sure if / how much the rear wheels were wider than fronts (if at all) and hence if it would work.

Thanks for the responses though.

m

Edited by md23 on Tuesday 7th December 15:34

[cslwannabe]

The 'summer' setup on my 330 was 225/40/18 (F) and 255/35/18 (R). My winter setup was 225/45/17 F & R which was the same as the standard 'summer' setup for a 330SE (ie the non Sport variant). Have to agree it was significantly more comfortable with the 17s fitted complete with winter tyres than the setup on 18s. Also 225 section rears should provide more than enough grip in the dry, not forgetting that narrower is better when cutting through snow, slush and standing water.

[md23]

OK, so width of wheels not an issue (same front and rear?). I would check but I haven't got the car handy. I sort of assumed that rears would be wider wheels than the front? On my CSL the wheels were 8.5J front and 9.5J rear with standard sizes for tyres 235/35/19 (f) and 265/30/19 (r) so assumed something similar on the M Sport?

Does this make sense?

Cheers

m

[cslwannabe]

I didn't fully appreciate that your spare set of wheels is also staggered (ie rears wider than the fronts). Personally I'd consider running 4 'fronts', although this would entail getting the summer tyres removed from your current front wheels (and then refitted again in the spring) or just go with the standard widths, but with winter rubber.

I know narrower is better with winter tyres however last winter EVO fitted standard width winter tyres to their long term test XFR (285 section rears!) and seemed very happy with it. We've gone with standard width winter tyres on our XF (245 section front and rear) and its been ok so far (touch wood!)...

[md23]

Yeah, suppose I could go fronts all round but a bit of a PITA swapping etc. Was hoping simply to create a "winter set" using the old wheels... What do you reckon to 245/45 on the rear wheel (standard being 255/40)? Will this work or am I just being daft? Would prefer to go narrower anyway but don't want to buy and find they don't fit!

[md23]

Right, someone reassure me that this makes sense! Wheels are 8J front and 8.5J rears. As mentioned above the summer tyre fitments are 225/45/17 and 255/40/17.

Would 225/50/17 and 245/45/17 work?

Thanks

m

[Zod]

md23 said:

Right, someone reassure me that this makes sense! Wheels are 8J front and 8.5J rears. As mentioned above the summer tyre fitments are 225/45/17 and 255/40/17.

Would 225/50/17 and 245/45/17 work?

Thanks

m

bigger diameter all round, so the speedo will be out.

[md23]

Zod said:

md23 said:

Right, someone reassure me that this makes sense! Wheels are 8J front and 8.5J rears. As mentioned above the summer tyre fitments are 225/45/17 and 255/40/17.

Would 225/50/17 and 245/45/17 work?

Thanks

m

bigger diameter all round, so the speedo will be out.

Yeah I know thi but I was more interested in whether the tyres would fit. As a matter of interest, how much would it be out by? Saw reference above to 0.75mm rolling radius difference (on 245's all round?) so can't be huge. If I had the time, I'd work it out but rather hoped someone knew!

Thanks

m

[cslwannabe]

Why the non standard sizes - is it because of winter tyre availability? Personally I'd go for the standard sizes or 4 'fronts' as I said previously - here are the difference in overall 'height' based on the sizes you mention:

Fronts
225/45 = tyre 'height' of 101.25 mm (225*0.45), overall diameter = 202.5mm + wheel diameter

225/50 = tyre 'height' of 112.5 mm (225*0.5), overall diameter = 225mm + wheel diameter, so quite a difference

Rears
255/40 = tyre 'height' of 102mm (255*0.5), overall diameter = 204mm + wheel diameter

245/45 = tyre 'height' of 110.25 mm (245*0.45), overall diameter = 220.5mm + wheel diameter, so again quite a difference

[md23]

Yeah, simply availability... Might have a rethink.

I can get a winter tyre set from BMW but again availability is an issue...

Thanks for the answers though!

m

Edited by md23 on Thursday 9th December 12:21

[soda]

md23 said:

Right, someone reassure me that this makes sense! Wheels are 8J front and 8.5J rears. As mentioned above the summer tyre fitments are 225/45/17 and 255/40/17.

Would 225/50/17 and 245/45/17 work?

Thanks

m

225/45/17 will be fine to fit all round on those wheels, I know the rear wheels are slightly wider but it will only be a small stretch and well within the manufacturers tolerances. Only downside will be less protection on the wheel should you kerb it.

[cslwannabe]

What did you replace the CSL with by the way (I remember you from cslregister!)? Still keep looking at them (and 996 GT3s - maybe next year!)...

[md23]

LOL. Tuscan s... Now also gone (to finance a business venture). Running around in a 130i (bought at the same time as the Tuscan) for the moment!

[md23]

soda said:

md23 said:

Right, someone reassure me that this makes sense! Wheels are 8J front and 8.5J rears. As mentioned above the summer tyre fitments are 225/45/17 and 255/40/17.

Would 225/50/17 and 245/45/17 work?

Thanks

m

225/45/17 will be fine to fit all round on those wheels, I know the rear wheels are slightly wider but it will only be a small stretch and well within the manufacturers tolerances. Only downside will be less protection on the wheel should you kerb it.

Not fussed about kerbing - the spare set, shall we say have been well used as a parking guide! Considered refurbing but haven't got round to it...

Re rolling circumferences, I calculate that the difference is only about 3% so speedo should only be out by 3% (or is it more complex than that?). Thoughts?

[soda]

md23 said:

soda said:

md23 said:

Right, someone reassure me that this makes sense! Wheels are 8J front and 8.5J rears. As mentioned above the summer tyre fitments are 225/45/17 and 255/40/17.

Would 225/50/17 and 245/45/17 work?

Thanks

m

225/45/17 will be fine to fit all round on those wheels, I know the rear wheels are slightly wider but it will only be a small stretch and well within the manufacturers tolerances. Only downside will be less protection on the wheel should you kerb it.

Not fussed about kerbing - the spare set, shall we say have been well used as a parking guide! Considered refurbing but haven't got round to it...

Re rolling circumferences, I calculate that the difference is only about 3% so speedo should only be out by 3% (or is it more complex than that?). Thoughts?

Changing to 225/50 and 245/45 will not just affect the speedo. Gearing will also be altered, it raises the possibility of fouling on the inside of the arches and as the tyres are larger it will raise the ride height by at least 10/15mm. Hence the popular suggestion of fitting 225/45 all round

Edited for speeling

Edited by soda on Thursday 9th December 21:20

[Mave]

I guess one thing to watch out for is whether you want the electronic driver aid gubbins to work. If you get the front / rear rolling diameters too far different I'd expect the traction control / DCS to go U/S.