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      02-27-2013, 05:36 AM   #8
gedward
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Drives: BMW F10
Join Date: Feb 2013
Location: Egypt

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Quote:
Originally Posted by HighlandPete View Post
BMW could have several reasons for not specifying a 245 section with the 17" rims.

Could be as simple as the tyre just doesn't work as well in that size. They will be striking a ride/handling balance for the given stock sizes and the 225/55 could be the best compromise in a run-flat, to speed rating and load index necessary in a 17" for the F10. Doesn't matter what tyres are available (or not) in alternative sizes, if it doesn't fit the criteria.

I run a 245/45 R18 summer tyre and the 225/55 R17 as winter wheels on my 535i and there isn't really a marked difference in ride quality. I sense the 17" tyre is stiffer in the sidewalls and therefore loses some of the gain you'd expect in a 17" wheel/tyre combination. Some of it could be running in cooler temperatures, but don't think it is the complete picture.

I'm not sure you'll lose too much grip if you opt for the best 225/55 R17 tyre you can source. I'm surprised how well a winter 225 section works on the 535i. BTW, in the 245/50 R17 size, there doesn't appear to be many tyres to choose from here in the UK in run-flat specification. And not to the normal BMW load/speed ratings either. Do you have a better range to choose from if you do depart from BMW sizing?

HighlandPete
Thanks a lot for the advice.
No, there doesn’t appear to be a lot of choices. I haven’t done my homework thoroughly yet but I knew quickly that both Bridgestone and Firestone don’t have the size but Pirelli have it in non-run flat.
I am seriously considering changing to NRFT and buying a slim spare. I figure if I stick to the speed rating and load index I should be OK. I don’t do any hard driving anyway. I mildly checked with the BMW dealer on that but he almost went berserk
As I said earlier, I suffered a lot of tyre damage between balloons and cuts. Four balloons when I was driving Goodyear and three cuts after I switched to Dunlop. All that within 40k km mileage. This is why I need to really get this thing sorted.
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