Steve Gill

Folks

The standard size tyre on my 535d Sport is 245/40/18s on all 4 corners. Now I read in the brochure it was 245/45/18s, which is why I bought 4 winter tyres of that size

Any comments on whether I should just go ahead and install the winter tyres?

colejl

They'll be just fine... The different isn't worth talking about The slight extra profile will help the ride a little

It may be worth advising your insurance company as they can get a bit picky about this sort of stuff...

realtyman

Your mileage (or is it Km over there?) will run up a little slower too!

Breae60

What??? Isn't 1 mile(km) 1 mile(km) anyway you go. Tires may have larger circimfrence, but if you gotta go a mile(km), it is a mile(km) isn't it?

zippers525

but the odometer wont know that the wheel is covering more distance per spin.

price9195

I think you might have some slight clearance problems in front with that size. I too have the sport package with 245/40 18 in front. I purchased Dunlop M3 snow tires in the 235/45 18 size because the 245/40s were sold out. The front tires just barely graze the forward wheel well plastic shroud when turning sharply. It is not audible from inside the car and is very slight in my case so I decided to run with them. I figured my setup is 2.5-3% larger than stock. Your circumference is slightly larger than mine. I would turn the wheels lock to lock after installing and before driving on the road so you can return them if necessary.
You wouldn't think these small changes would make a difference, but the clearance up front is tight while turning.

By the way, ran my M3s today in 6-8 inches of unplowed snow for 28 miles and made it to work although there were some hair-raising moments.

Steve Gill

Thanks for your advice - on this basis I've decided to return them. I used this website - http://www.net-comber.com/tirecalc.html to calculate the difference and it was 0.96" of a difference in overall diameter - too much. For comparison, your setup was 0.61" difference.

Now I cannot order 18" 245/40s here in the UK - but I can order 18" 225/45 - surely this would be better for the snow as it's a smaller width? The difference between 245/40s and 225/45s is 0.25" - presumably not enough to cause rubbing.

Also, I've just noticed that I can also order 235/40/18s - a difference of -0.32".

Can anyone confirm if it's OK to run 225/45/18s on my M Sport Wheels style 135M? Or, is it better to go for the 235/40/18's as they are closer to the OEM 245/40/18s?

Steve Gill

OK, so I decided to go for Vredestein Wintrac Extremes, 245/40/18Ws from etyres.co.uk. They're getting fitted on Friday, so I'll let you know how it goes. I felt safer choosing the same size as is currently fitted, although Gary from Tirerack kindly confirmed that either the 235/40R18 or the 225/45R18 is within the recommended tire width range for 8" wide wheels.

This website was extremely useful - my wheels are the 135M.

Steve Gill

Just another point - I've installed my Origin b2 (GPS speedtrap device) and it's clear that the car is reporting that it is travelling around 5 to 7% faster than it actually is - in other words, speedo says 50mph, the GPS says 47mph.

I've heard most cars speedo's are like this - so surely if I increase the overall diameter of the wheel and tyre to compensate this should bring the speedo back into line?

stu

Hi SG 535d - do consider costco in the uk for tyres- unbeatable service/value.
PS my snooper S4 gave mph indications within 1 mph of the speedo - strange how it differerd to your experience.