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05-03-2013, 04:37 PM | #1 |
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questions re winter tires setup
Ok, so I finally switched back to my summers and noticed that both my rear winter tires (BMW's suggested winter pkg of Pirelli Sottozeros/style 290 wheels) are bald; the fronts are still good. Since all 4 winter tires and wheels are the same specs, I assume that I just need to buy 2 new tire replacements and do the tire fitting/rebalance on those 2 wheels. I plan on doing the following, pls advise if it makes sense or if there is a better way. If I left anything out, pls let me know. Thx!
1. since the rear tires wear faster than the fronts, I will put the new tires on the rear come next winter; 2. when the rears get worn again but are still newer than the fronts, just leave them as-is; if the rears are worn out more than the fronts, then do a swap (objective to ensure that the newer tires are placed in the rears); 3. if I need to do a swap, it is best to do a front to back swap (i.e. front right w/ rear right), not criss-cross (e.g. front right swap w/ rear left). I also noticed that both my bald rear tires are concave(?) in that the middle part is noticeably sunk in: what does that mean? |
05-03-2013, 10:21 PM | #3 |
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You're thoughts on tire placement are sound. If you're tires are unidirectional then of course you must rotate only front to back.
That wear issue you describe is def an inflation problem.
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05-04-2013, 07:30 AM | #4 |
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Hey Tranquility, how come all 4 tires are the same spec? Aren't your tires 225's in the front and 245's in the rear? (can't recall the exact sizes now, but you get my drift hopefully).
Dave
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05-04-2013, 09:03 AM | #5 |
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It's because he's talking about his winter set. Lots of people who get dedicated winters get a square set.
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05-05-2013, 10:16 PM | #6 |
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Yup, all 4 are the same so that means not unidirectional: in that case, what is the best tire swap method, front to rear or criss-cross as I've stated in my OP?
Here is a pic of the weird 'concave' shape, not sure why as I always have PSI@36/42 (F/R). As noted, my rears are deadly bald now lol: |
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05-05-2013, 10:48 PM | #7 | |
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You haven't been driving entirely on railroad tracks, have you? |
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05-05-2013, 11:09 PM | #8 | |
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No, haven't been driving on rr tracks lol. Also, not sure if relevant, but my winter rears worn out at 31K kms/19K miles. |
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05-05-2013, 11:09 PM | #9 |
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Wow that is weird - I wonder if that concavity has anything to do with those PSI things. I understand that BMW recently submitted a patent for an ATPS (Automated Tire Pressure System). It will soon do away with the need to use and understand tire pressure. Kinda of like the DCT is going to do away with the MT.
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05-05-2013, 11:23 PM | #10 | |
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Anyway, is having this concave thing a symptom of under or over inflation? This is the first time I've noticed it and it's my 3rd winter use for this set. |
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05-06-2013, 12:50 AM | #13 | |
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I'm the only driver, unless some aliens are using my Z as a joyride during the wee hours. I never have DSC off and don't drive that aggressively. |
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05-06-2013, 04:29 AM | #14 |
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05-06-2013, 08:09 AM | #15 | |
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However, the wear pattern in the pic, with the center more down more than the edge is consistent with overinflation. Since you are using the OE recommended setup, perhaps you could go to a BMW center and get them to confirm the diagnosis of overinflation and write a letter to the manufacturer explaining that their recommendation resulted in premature tire wear |
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05-06-2013, 09:02 AM | #16 |
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Wonder if you had a warm winter and your tires became over inflated due to ambient temperature?
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05-06-2013, 09:46 AM | #17 |
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Definitely the tire looks overinflated. Maybe you checked the tire pressure in very cold weather conditions but mostly used them in high temperatures?
Additionally, BMW appears to suggest too high tire pressures as this will result in low roll resistance, high mpg and low CO2/km (as reuiqred by US and EU authorities)... Best regards Mick |
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05-06-2013, 02:38 PM | #18 | |||
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LOL, no, I'm fit and trim.
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I guess 31K kms/19K miles is too soon for bald rear winter tires? What would have been a better lifespan for these? Quote:
Quote:
Another thought is I put off switching back to summers for a few weeks and have been driving in warmer temps...not sure if that would speed up the wear on the tires? Still, it's a little extreme to find the rears completely bald. |
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05-06-2013, 03:51 PM | #19 |
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Although warm weather isn't ideal for winter tires, a couple of warmer than usual days won't hurt them like that. We have winter tires on all of our cars - except the Z4 - and none look like the one in your pic.
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05-06-2013, 03:52 PM | #20 |
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Actually, why don't you stop at a tire store and just ask them for their opinion?
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05-06-2013, 05:57 PM | #21 |
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The door sticker tire pressure recommendations only apply to run flats. If you change to another tire like Michelin PSS or whatever you are on your own when it comes to tire pressure. That doesn't mean you can't use the door sticker as a start point but it only a place to start. You either have to get a tire temp sensor and use it or you adjust the pressure relative to how the tire is wearing until you get reasonably even wear across the tire. In general manufacture recommendations are high for the reasons stated in the post above.
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05-06-2013, 06:04 PM | #22 | |
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Ok, so the consensus appears to try for lower PSI. If the tire was conVEX, does that mean it would be under-inflated? I always check pressure/pump tires when the tires are at rest for a long time...not sure as a poster stated above that I may have set the 'correct' pressure during such time, but when I actually drive out it is to a warmer environment, so that causes the over-inflating? |
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