[elbman]

There are a number of threads regarding switching to non-rft tires; looking to do the same but going from a 245/50/18 to either a 235/55/18 or 255/50/18 on the 308 wheels. Anyone have any issues with either of theses sizes, or alternate recommendations?

[iride4u]

I can not comment on the sizes as my wheels are staggered in size. The not run flats will be more compliant. Not Lexus soft but softer then the stock rft's.

[brissim]

Didn't do it with 18" wheels, but for 17" wheels have gone from 245/55/17 runflats to 235/60/17 non-RFTs. This is a 12.5mm (or 1/2") increase in OEM overall tyre diameter and have done over 30,000 km (18,000 miles) without issues.

Looking at your proposed tyre sizes, the 235/55/18 is a 13.5mm increase and the 255/50/18 is a 10mm increase over the OEM 245/50/18 tyre diameter. So I would suggest based on my experience you should have no issues with either of these tyre sizes. Just be aware as a result of the small increase (~2%) in tyre diameter, your speedo will read about 2% low. Not a big issue.

Tony

[ReturnZero]

I've thought about this too, but what will you do if you get a flat?

[UKMS]

Originally Posted by ReturnZero

I've thought about this too, but what will you do if you get a flat?

I changed to non RFT for winter on my 5 series, I just purchased a BMW inflation kit to use in the event of a flat.

MS

[stumblingtrout]

Originally Posted by ukstevens

I changed to non RFT for winter on my 5 series, I just purchased a BMW inflation kit to use in the event of a flat.

MS

What setup did you use and how did you find the ride?

I bought a set of Alutec 17" rims and got some Conti Wintercontact TS830P's all round.

Great grip. Bit of a wallowy ride though...

[elbman]

Originally Posted by ReturnZero

I've thought about this too, but what will you do if you get a flat?

If not in the sidewall. Patch and inflate. I haven't had a flat in years though, and that includes the E90 335 that I switched a long time ago.

There are a lot more discussions on tire sizes, with specific brands and models on that side to research. Most likely due to less clearance in the wheel well. So I was more interested in anything that had already been shown to not fit without rubbing or another issue.

[UKMS]

Originally Posted by stumblingtrout

What setup did you use and how did you find the ride?

I bought a set of Alutec 17" rims and got some Conti Wintercontact TS830P's all round.

Great grip. Bit of a wallowy ride though...

I just changed the tyres over on to my existing 18" Alloys. I actually preferred the ride on the non RFT.

MS

[elbman]

Is there a working compact spare like there was for my E90?

I've found some showing for earlier years, <2011, but nothing showing 2012+.

[mspringer]

You might be able to put one together yourself for less money but one can be bought here:

http://www.bimmerzone.com/category/B...pare_Tire.html

[brissim]

Originally Posted by mspringer

You might be able to put one together yourself for less money but one can be bought here:

http://www.bimmerzone.com/category/B...pare_Tire.html

Someone had earlier provided this link in another thread. The aspect which concerns me about this X3 F25 spacesaver this they admit it is 0.5" smaller overall diameter than OEM tyres. Not sure what impact this would have (even just in the short-term) on the mechanics of the X3. I know it would not be tolerated on the old E83 X3, but I understand the X-Drive on the F25 is a bit more tolerant. However, its something I would not like to find out.

Tony

[mspringer]

Originally Posted by brissim

Someone had earlier provided this link in another thread. The aspect which concerns me about this X3 F25 spacesaver this they admit it is 0.5" smaller overall diameter than OEM tyres. Not sure what impact this would have (even just in the short-term) on the mechanics of the X3. I know it would not be tolerated on the old E83 X3, but I understand the X-Drive on the F25 is a bit more tolerant. However, its something I would not like to find out.

Tony

While I don't have technical information on the allowable variations, the difference between the space saver and stock tire is the same as that between a brand new tire and one worn to the legal limit. To be sure you might want to call BMW or email Mike Miller, tech guru for Roundel, at techtalk@roundel.org .