Under inflated run flats

Under inflated run flats

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CSK423

Original Poster:

761 posts

206 months

Saturday 22nd October 2016
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I've just swapped my wheels out for winters (yes probably too early but the car will be parked up for the next few weeks due to work) and noticed that the 3 original tyres (1 was swapped 6 months ago due to a puncture) that have came off the car have worn severely on the inside shoulders to the point where some slight cord is showing at 2 or 3 points round the tyre. The worst tyres are the rears.

It looks as if they are under inflated but are running 33psi rear 31psi front which is what the car came with from new. Also the wear is not even round the inside of the tyre it almost bulges slightly if that make sense. All rims are round inside and out and I haven't had any wobbles.

I've done just over 26.5k miles and the rears are just over 2 mm the front just over 3mm. I'm quiet happy with how long they've lasted I'm just wondering why they've give up the ghost on the inside shoulders and why it's so uneven almost as if in parts the runflat has collapsed.

Anyone came across this before ?

Fore Left

1,411 posts

181 months

Saturday 22nd October 2016
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What car and what are the pressures on the plate on the door post?

CSK423

Original Poster:

761 posts

206 months

Saturday 22nd October 2016
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2015 640d GC. pressures are 2.2 and 2.4 bar on the door which is around 32psi and 34psi for the 20" wheels.

CSK423

Original Poster:

761 posts

206 months

Saturday 22nd October 2016
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Collectingbrass

2,198 posts

194 months

Saturday 22nd October 2016
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Either the suspension geometery is all to cock or something is rubbing - if they are all like that then I'd say suspension, unless you have the wrong size tyres on? What was the cause of the puncture, was it that corner wearing earlier than the rest?

Frances The Mute

1,816 posts

240 months

Saturday 22nd October 2016
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It's pretty common for runflats to have shoulder wear - particularly on BMWs.

Power steering sensitivity is the main culprit for the front and the usual neg camber settings take care of the rear.

Ninja59

3,691 posts

111 months

Sunday 23rd October 2016
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Your pressures are to low for a start 20's on the 640 should be 35 front 38 rear.

Inside tyre wear is common you can dial out some of the factory camber on the rear to reduce the wear, front you cannot alter. The camber is the problem here but bmw like it to make it more sporty.

Elysium

13,755 posts

186 months

Sunday 23rd October 2016
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That's not down to the factory camber and it is unusual for BMW runflats

Your pressures might be a little low, but not so much as to have caused that.

I think you need to get the alignment / geometry checked.

CSK423

Original Poster:

761 posts

206 months

Sunday 23rd October 2016
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Ninja59 said:
Your pressures are to low for a start 20's on the 640 should be 35 front 38 rear.

Inside tyre wear is common you can dial out some of the factory camber on the rear to reduce the wear, front you cannot alter. The camber is the problem here but bmw like it to make it more sporty.
I picked up on this aswell but this is for a loaded car, 95% of the time it's me on my own however the 2.2 (32) and 2.4(34) I listed above is for a car with 3 people (or whatever the symbol is) on the door pillar.


I think I'll flick my local dealer an email with the pics and gather their thoughts......which will be a £100 wheel alignment no doubt !

Thanks for the responses.

Ninja59

3,691 posts

111 months

Sunday 23rd October 2016
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Hmm mine is usually on my own as well, my door pillar shows 35 and 38 for 20's., under inflation will contribute to reduced life, how much is questionable.

In regards to factory camber a lot of F10/11 (the 5GT seems to have an even more exaggerated issue with inner tyre wear) owners have suffered the same problem and it is "within BMW tolerance for alignment" which has quite an aggressive degree of negative camber on the rear from factory. There is a fair amount of information out there about the inner tyre edge wear, I would not be surprised if they come back and say it is within tolerance after KDS.

Mine has been for a KDS recently and had some of the negative camber towards the most positive in tolerance requirements (which is still negative) on the rear, the turn in is not as great as it used to be, but it does lower inner edge wear (my MX5 runs a fair bit of rear camber to improve turn in, but it does produce wear similar in format to BMW's...). I managed to get mine for free under warranty (and redone twice after noticing a cockup), I had sadly knocked the front passenger at about 10mph and it was causing some feathering on that tyre because the toe was out and had to much toe in (a slightly positive value).

Regarding the front how much wear is on the inside?

If you are paying a KDS will be between 250-300.



Edited by Ninja59 on Sunday 23 October 15:41