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[mdosu]

So, I have OEM 18s and I use the square set up of 245/40/18s for my winter tires.


2 years in a row now, I have some sealant related issue with my rear tire. In short they'll lose about 10 psi over the course of 1 to 2 weeks. Every time I take it back to the dealer/shop that mounted them, I argue with them that they didn't seal the TPMS or their cheap stems correctly.

This year, my local BMW guys said that the narrow size causes an issue. In short they say, if the tire is parked on an odd angle or over some item, it could create a small seal problem. Sounds like BS to me. They still agree to "reseal" for me again for free which I take it as, my reasoning is more likely.


what do you think?

[mdosu]

also, after every "re-seal" they perform, the rear tire in question NEVER has a leakage issue for the rest of the winter.

[Giccy]

No clue (sorry, not helpful), but I have the same setup and am very curious if I'll experience the same thing.

Keep us posted if you figure it out!

[pbonsalb]

I run 255/40/18 and 235/40/18 snows on stock 18 x 9.5 and 18 x 8.5 wheels with no issues. I do not think 245/40/18 would be a good size for 9.5 inch wide stock rear wheels. However, kids stretch tires all the time and may have some secret techniques for sealing.

Maybe you could trade someone your two rears for his two fronts. You would have a great snow wheel set and he would have a higher performance street set.

[mdosu]

Originally Posted by Giccy Gic

No clue (sorry, not helpful), but I have the same setup and am very curious if I'll experience the same thing.

Keep us posted if you figure it out!

it might depend on the tire itself. My suggestion is to measure your tire pressure at least once a week under the same conditions (for me, in my garage, before driving) and check for any differences.

Here's a example of a 245/40/18 on OEM, notice the middle section of the sidewall and how it's stretching out to meet the rim

http://www.m3post.com/forums/showpos...16&postcount=2

[Jaypod]

I ran the same set up as you on the OEM 18's with Pirelli Sottozero tires and never had an issue with losing air. (even while sitting in storage)

[bobbyd1961]

i have dunlops m3 winter sports never a leakage problem 245/40/18s all around

[bigjae1976]

If its a slow leak, usually its from the rim bead or valve stem.

I'd just spray some water on the valve stem and see if it bubbles.

If there is no issue, its probably from the rim bead. Sometimes, there is some defect on the rim or tire that makes it more prone to a small leak. Then, sometimes, the bead won't leak unless the tire is rolling or under load.

So the dealer may be correct.

When I used to mount tires many years ago, I'd put some bead sealer under the rim bead and it would be good to go. Not ideal. If you are very anal retentive, you can try a new tire and then try a new rim.

BTW, let me know if you want to swap your rear rims for a set of OEM 18" front wheels. I have a pair of mint front wheels.

[mdosu]

Originally Posted by bigjae1976

If its a slow leak, usually its from the rim bead or valve stem.

I'd just spray some water on the valve stem and see if it bubbles.

If there is no issue, its probably from the rim bead. Sometimes, there is some defect on the rim or tire that makes it more prone to a small leak. Then, sometimes, the bead won't leak unless the tire is rolling or under load.

So the dealer may be correct.

When I used to mount tires many years ago, I'd put some bead sealer under the rim bead and it would be good to go. Not ideal. If you are very anal retentive, you can try a new tire and then try a new rim.

BTW, let me know if you want to swap your rear rims for a set of OEM 18" front wheels. I have a pair of mint front wheels.

thanks for the comments. the rim bead idea was indeed what the dealer said and he said the 245 tire is the culprit. It's just very hard for me to visualize it happening.

Thanks for the offer for your front wheels, as of now, i'm sticking with my current setup, this very well could be my last winter (I'll be moving to warmer climates late this year, hopefully, if not, I don't mind buying 265s for my winters for the rear next year)

[bigjae1976]

Originally Posted by mdosu

thanks for the comments. the rim bead idea was indeed what the dealer said and he said the 245 tire is the culprit. It's just very hard for me to visualize it happening.

Thanks for the offer for your front wheels, as of now, i'm sticking with my current setup, this very well could be my last winter (I'll be moving to warmer climates late this year, hopefully, if not, I don't mind buying 265s for my winters for the rear next year)

Its probably the particular tire...not the fact that it is a 245 wide tire.

[mdosu]

Originally Posted by bigjae1976

Its probably the particular tire...not the fact that it is a 245 wide tire.

great, I'll check it out. 1 of the tires is a different brand. They're all same load/speed/rating stats and tire type (all-Season, M/S tires), but I forgot to check if the problematic one is the odd one out.

But from the top of my head, I'm pretty sure it is the common one though.

[kawchkjf]

have you hit a pothole? could be a slightly out of round rim as well.

[signes]

I am on my 4th winter with the same Nokian Hakkas in 245/40 square and have never had to even top them up with air over the season.Only negative is how stretched the look on the OEM 18 rears.

[Daft]

Originally Posted by Giccy Gic

No clue (sorry, not helpful), but I have the same setup and am very curious if I'll experience the same thing.

Keep us posted if you figure it out!

You'll never have this problem as Canadian spec BMW's have a completely different TPMS as the US spec cars do. Unless of course you bought your car in the USA..

[mdosu]

argh! it's happening again after I got it back on 1/12/12, i checked my pressure today, it lost 5 psi over the course of 1 week, not as bad as earlier.

i hope it's just due to the tire/rim bead issue and not a cracked wheel, but I'll diagnose that this summer when my OEM sized 265/40/18 summer tire goes on. For now, since winter will only last until March 31, I'll just fill my tire up once every 2 weeks. sigh.