Thoughts on Cracked 296 alloys please

[Busterboo]

You seem to be the only one wanting 'evidence' so instead of demanding it from others why don't you produce some that says run flats DON'T cause cracking, then when you have found such evidence you can tell us all about it.

I don't know if run flats do or don't cause cracking, because I don't know if there's any evidence one way or the other.

 

[Burgy100]

It's not evidence or proof but a start

http://whatconsumer.co.uk/forum/consumer-rights-television-programmes/7790-bbc-watchdog-some-bmw-wheels-all-theyre-cracked-up.html

 

[mr wilks]

No, Rob, I'm just hoping someone will produce some evidence of a relationship between hard tyres and cracked rims.

Not the "It's obvious", or the "Everybody knows", or the "There have been lots of posts about it" type ... or the "It's not rocket science" sort of science, but actual evidence.

A report from a test, for example.

Let's speed things along then mr B
As testing infinite wheel / tyre / pressure / road combinations is never going to happen 5 factors are possible reasons
( please shout up if you don't agree or have others to add )

Tyres not big enough profile ?
Tyres too hard sidewalls ?
Recommended tyre pressures too high ( happens on many other BMW models running less pressure so unlikely )
Alloys inferior construction ( happens with many other BMW OEM alloys made over 10year period so unlikely )
Potholes too big or wrong shape for wheels

 

[Nictrix]

No, Rob, I'm just hoping someone will produce some evidence of a relationship between hard tyres and cracked rims.

Not the "It's obvious", or the "Everybody knows", or the "There have been lots of posts about it" type ... or the "It's not rocket science" sort of science, but actual evidence.

A report from a test, for example.

Let's speed things along then mr B
As testing infinite wheel / tyre / pressure / road combinations is never going to happen 5 factors are possible reasons
( please shout up if you don't agree or have others to add )

Tyres not big enough profile ?
Tyres too hard sidewalls ?
Recommended tyre pressures too high ( happens on many other BMW models running less pressure so unlikely )
Alloys inferior construction ( happens with many other BMW OEM alloys made over 10year period so unlikely )
Potholes too big or wrong shape for wheels

You may have missed the all important driver misuse.
Although everybody who has had a cracked wheel says they have never hit a pothole hard, is this actually true though, not just for the owner but the previous owners.
There wont be many people who will come on here and shout about how they smacked a pothole doing 50 and cracked the wheel. and neither will they tell BMW that if they are trying to get wheels for free.
It can be very difficult to avoid every pothole on the road especially in the dark.

 

[Busterboo]

No, Rob, I'm just hoping someone will produce some evidence of a relationship between hard tyres and cracked rims.

Not the "It's obvious", or the "Everybody knows", or the "There have been lots of posts about it" type ... or the "It's not rocket science" sort of science, but actual evidence.

A report from a test, for example.

Let's speed things along then mr B
As testing infinite wheel / tyre / pressure / road combinations is never going to happen 5 factors are possible reasons
( please shout up if you don't agree or have others to add )

Tyres not big enough profile ?
Tyres too hard sidewalls ?
Recommended tyre pressures too high ( happens on many other BMW models running less pressure so unlikely )
Alloys inferior construction ( happens with many other BMW OEM alloys made over 10year period so unlikely )
Potholes too big or wrong shape for wheels

Sounds like science to me.

And ... I hesitate to say this, because it's so obvious ... it also seems probable, as I'm sure it does to you, that any permutation from this combination of factors is responsible for rim cracks and not only run-flats.

Now, whilst this statement is hardly a revelation, it does raise the question, of course, of why these factors do not seem to do the same consistency of damage to other manufacturers' wheels?

So, for example, in your Porsche days, were cracked wheels a constant topic? I can't remember it being in mine.

 

[Busterboo]

It's not evidence or proof but a start

http://whatconsumer.co.uk/forum/consumer-rights-television-programmes/7790-bbc-watchdog-some-bmw-wheels-all-theyre-cracked-up.html

It's excellent. Thank you very much, indeed.

It also confirms one of my beliefs: "... because the low-profile tyres may have been slightly underinflated."

 

[Smartbear]

Do Porsche use runflat tyres?
Rob

 

[Busterboo]

Do Porsche use runflat tyres?
Rob

A good point, Rob. No.

But they do run their wheels on 36psi front and 44psi rear.

 

[mr wilks]

On both previous Audi A6 Avant & current C Class estate both came with staggered tyre set up & both were running bigger stock profiles than similar Bmw models (225 45 18 & 245 40 18)
My son has had many performance VWs on 18s & 19s again running bigger tyre profiles either 4 x 235 35 or 4 x 225 40
Non of the above have ever been runflats so straight off you have increased chances of not splitting a rim by direct comparison to BMW models on runflats & smaller profiles . . That's how i read the situation but I'm only applying common sense & logic as apposed to scientific research

 

[Marlon]

You may have missed the all important driver misuse.
Although everybody who has had a cracked wheel says they have never hit a pothole hard, is this actually true though, not just for the owner but the previous owners.
There wont be many people who will come on here and shout about how they smacked a pothole doing 50 and cracked the wheel. and neither will they tell BMW that if they are trying to get wheels for free.
It can be very difficult to avoid every pothole on the road especially in the dark.

Makes sense.
We've all done it occasionally, thumped down a pot hole we hadn't seen. Unless you stick to the A roads its a f**king nightmare driving around Preston. I know all the problem roads now and haven't been caught out yet.

 

[Busterboo]

mr wilks and Marlon are right, of course.

In the real world, wheels need protecting with the best reasonable profiles.

And correct pressures.

 

[Z4Rick]

I take a different view. The only real evidence I have seen is that the 296's fail. I think it is enough to know they have a problem with the design/manufacturing of that wheel since it seems to be pretty much a 296 issue. Potholes, small sidewalls, RFT vs. non RFT also play a role, but in the end, its the 296 wheels that occasionally FAIL!

I needed a set of wheels for track and summer driving, so I set about learning all I could about alloys and was blessed to have an old school chum who runs an injection molding business. He uses several different processes for making wheels and simply steered me towards wheels that were NOT gravity fed, but low or high pressure molded wheels for the significant strength gains.

The problem is the 296 is a GREAT looking wheel on the Z, so I found a wheel that looked pretty close rather than clinging to a "BMW OEM only" ethic, and now have higher confidence my wheels are not prone to cracking.

Here's an article on the subject:
https://www.tirerack.com/wheels/tech/techpage.jsp?techid=90

 

[Smartbear]

I take a different view. The only real evidence I have seen is that the 296's fail. I think it is enough to know they have a problem with the design/manufacturing of that wheel since it seems to be pretty much a 296 issue. Potholes, small sidewalls, RFT vs. non RFT also play a role, but in the end, its the 296 wheels that occasionally FAIL!

I needed a set of wheels for track and summer driving, so I set about learning all I could about alloys and was blessed to have an old school chum who runs an injection molding business. He uses several different processes for making wheels and simply steered me towards wheels that were NOT gravity fed, but low or high pressure molded wheels for the significant strength gains.

The problem is the 296 is a GREAT looking wheel on the Z, so I found a wheel that looked pretty close rather than clinging to a "BMW OEM only" ethic, and now have higher confidence my wheels are not prone to cracking.

Here's an article on the subject:
https://www.tirerack.com/wheels/tech/techpage.jsp?techid=90

I would add the 326 wheel to that list as well, seems like its not rare for them to crack on the rear inside rim
Rob

 

[SpiketheBike]

I'm one of those who downsized to 18s. Still running RFTs. Did not want the worry of not having a spare. Ride is, I think, slightly better, but it's totally subjective I guess.