Cracked alloy

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PH XKR

Original Poster:

1,761 posts

103 months

Friday 13th January 2017
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I meant more sidewall height

donkmeister

8,211 posts

101 months

Saturday 14th January 2017
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catso said:
A friend of mine has a fabrications business and is a particularly good welder. He repairs many alloy wheels, the vast majority of which are BMW..
Mate of mine went through a total of 6 alloy wheels with his 335d, which was bought new from the dealer and cossetted (i.e. never kerbed, nor bumped up and down kerbs, nor taken over speedbumps at any more than a crawl). Not fit for purpose.

a4cabrio

906 posts

160 months

Saturday 14th January 2017
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Nezquick said:
Jarcy said:
I suffered a cracked wheel on my 9 month old BMW. I only found out because I thought I had a slow puncture.
To my lay-man's eyes, the crack was clearly a manufacture fault as it had cracked outwards (as opposed to inwards as you might expect if the wheel had suffered a blow). And of course I know that the car had not been driven over an undue curb or pothole.
However BMW were not interested in paying for the rim, nor was the lease company.
Very common with BMW alloys, especially the larger ones (19" and above). BMW simply will not entertain any claims even though they clearly have an issue with numerous styles of alloy wheel. The 326 style alloy on the E89 Z4 was terrible for cracking.
I had a cracked alloy wheel replaced by BMW 18 months after buying a used car from them, it was a 19" MV4 wheel which was prone to cracking. I'd searched google and found it was a big problem and had printed off quite a bit of stuff to back myself up if BMW didn't want to know but they changed it without question.

If I was the OP I'd approach the dealer you bought it from and see how it goes, the worst they can say is no.

PH XKR

Original Poster:

1,761 posts

103 months

Sunday 15th January 2017
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To get back to the dealer would cost more than the repair. Fortunately very very minor and being repaired as we speak

4rephill

5,041 posts

179 months

Sunday 15th January 2017
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PH XKR said:
.......Fortunately I didn't have run flats nor need them but the sidewalls are ridiculously thin. Next time round I am going to see if I can work out a safe replacement with more sidewall
If you raise the height of the sidewall to a suitable degree by going to a higher profile, how are you going to maintain the same rolling radius?


herewego

8,814 posts

214 months

Sunday 15th January 2017
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Willy Nilly said:
why do we bother with alloy wheels when they are such an expensive pain in the arse?
Thank you for calling wheels wheels.

I'm sure BMW don't make the wheels any more than Jaguar do. They may well use the same supplier.

I'm not a metallurgist but it wouldn't surprise me if welding up the cracks creates other problems since it likely changes the structure of the alloy and leaves residual stresses local to the weld.

PH XKR

Original Poster:

1,761 posts

103 months

Sunday 15th January 2017
quotequote all
4rephill said:
PH XKR said:
.......Fortunately I didn't have run flats nor need them but the sidewalls are ridiculously thin. Next time round I am going to see if I can work out a safe replacement with more sidewall
If you raise the height of the sidewall to a suitable degree by going to a higher profile, how are you going to maintain the same rolling radius?
Well, I'm not, but the ecu can be adjusted to take it into account

Piersman2

6,599 posts

200 months

Sunday 15th January 2017
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PH XKR said:
4rephill said:
PH XKR said:
.......Fortunately I didn't have run flats nor need them but the sidewalls are ridiculously thin. Next time round I am going to see if I can work out a safe replacement with more sidewall
If you raise the height of the sidewall to a suitable degree by going to a higher profile, how are you going to maintain the same rolling radius?
Well, I'm not, but the ecu can be adjusted to take it into account
Not so sure it can unless you want to let someone loose in your ECU programming, I don't expect there's a configurable option to change this.

If you want taller side walls, you'll need smaller diameter wheels. This site ( https://www.wheel-size.com/calc/ ) is great to see the difference in rolling circumference , and what alternative tyre sizes can be used with wheels.

As a note, I accidentally fitted some taller sized tyres to the rear of my Boxster, only a few percent bigger, but it definitely blunts the off the line performance.

PH XKR

Original Poster:

1,761 posts

103 months

Sunday 15th January 2017
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Every ECU since the dawn of wheel size options has had to take it into account. The real truth is I'll just keep the profiles OEM or replace the 20s for 19s or 18s

KevinCamaroSS

11,641 posts

281 months

Monday 16th January 2017
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PH XKR said:
Every ECU since the dawn of wheel size options has had to take it into account. The real truth is I'll just keep the profiles OEM or replace the 20s for 19s or 18s
I would think this is your best bet.

anonymous-user

55 months

Monday 16th January 2017
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herewego said:
Willy Nilly said:
why do we bother with alloy wheels when they are such an expensive pain in the arse?
Thank you for calling wheels wheels.

I'm sure BMW don't make the wheels any more than Jaguar do. They may well use the same supplier.

I'm not a metallurgist but it wouldn't surprise me if welding up the cracks creates other problems since it likely changes the structure of the alloy and leaves residual stresses local to the weld.
You are right on all counts and its not just BMW who have the problem. All of the manufacturers suffer with it on large wheel, ultra low profile tyres.