Cracks in factory wheels...

[jon dee 500]

Recently I chanced upon a website that had an article about a class action against BMW regarding allegedly faulty factory wheels fitted to Z4 models. That caught my attention and I did a bit of digging to see how common or widespread this might be... and it seems that it is a known thing with certain BMW factory wheels on certain models of cars and SUV's. Surprised me as I always thought that factory wheels would be stronger and safer than aftermarket wheels from unknown manufacturers. 

What doesn't surprise me is that the problems with BMW wheels seem to be more common with wide, 19 inch and larger wheels, fitted with 35 or 30 series tyres. This is a combination that is well known for damaging rims and tyres. I am using 18" wheels by choice, as I have read enough about bent rims on other forums to persuade me against going to 19" wheels It may be that cast wheels are more prone to cracking and not as strong as forged wheels, but since all the BMW factory wheels appear to be cast, those are the wheels I am asking about.  

So, a couple of questions... (a) Is it necessary to inspect my wheels regularly for cracking ? and... (b) How many people have had, or know of others who have had problems with cracked rims ? Specifically I am interested in cases where there was no heavy impact on the wheel (e.g. deep pothole, kerb etc) and the tyre itself was not damaged. Hit me !!!

Cheers...

[Gaz 1060]

After the earthquakes here in Christchurch had plenty of cracked rims on x5s running 20s but wasnt just a bmw thing, all brands suffered here 

[Cammsport 390]

Cracks would result in a slow leak and would very rarely be a catastrophic failure, am I right? 

[jon dee 500]

1 hour ago, Cammsport said:

Cracks would result in a slow leak and would very rarely be a catastrophic failure, am I right? 

From what I have read that would seem to be the correct. In a lot of cases small cracks are only picked up when the wheel is off the car and the tyre is removed for a puncture repair or replacement. That provides an opportunity to inspect the bead seating area for hairline cracks that would cause a slow leak. Larger cracks are usually the result of an obvious impact that deforms the rim, damages the tyre, and may even break pieces out of the rim.

Picture of a crack in a 19" type 296 wheel from a Z4. This type of crack is often found on the inside lip and therefore very difficult to spot while the wheel is on the car. The likely cause is fatigue cracking due to deflection of the inner rim as there is little support from the spokes. Low profile runflat tyres are suspected of contributing to this type of cracking because of their stiffer sidewalls. Hairline cracks should not be ignored as they will continue to propagate with use. Small hairline cracks may be repairable but larger open cracks will usually be considered not repairable... depends on who you ask and what repair facilities they have.

Cheers...

[Haggisman 35]

The UK Z4 forum I’m a member of report many cases of not only cracked wheels but broken springs. In fact, they have a broken spring club within the forum with many owners using suplex, eibach or similar replacements. Some of the roads in the UK leave a lot to be desired, potholes etc. re wheels, mainly the 19” ones on the newer model Z’s are the ones that are cracking

[jon dee 500]

Yes... the 296 wheels fitted to the Z4 were the subject of a successful class action in the USA whereby BMW agreed to replace or reimburse owners who had wheels fail during the warranty period. It doesn't take much searching on the internet to find that there are many forum threads detailing the problems that countless BMW owners have had with cracked wheels. It is not just the Z4... without digging deep I found that 6-series, 3-series and 1-series forums have all reported problems... primarily with 19" wheels, but also to a lesser extent with 20" and 18" wheels.

Now before we all change to 16" wheels and 60-series tyres to alleviate anxiety and paranoia, it has to be said that in the normal course of events many wheels and tyres will be damaged from hitting potholes, kerbs and objects lying in the roadway. Some drivers will then complain that the wheel "cracked" when it should not have, and maybe that would have been true in the days of smaller wheels and taller tyres. But now that the fashion is for wide, tall wheels and short tyre sidewalls, the inevitable result is a wheel/tyre combination that is more easily damaged by seemingly minor impacts.  The use of runflats will be a factor as well.

As can be expected, BMW will try and defend itself from spurious claims of "defective wheels" by turning down claims where there is evidence of mechanical damage. However, when there are thousands of owners all reporting the same type of failure within the warranty period, and there is no evidence of contributing mechanical damage, it is reasonable to infer that there is a wheel design or construction flaw to blame. Not all owners have problems, and not all wheel designs have problems. And neither is cracking of 19" and larger wheels confined to BMW... almost all vehicle manufacturers have the same problem to some extent.

I think that any time a tyre on your vehicle starts loosing air and the cause is not obvious, the wheel should be checked for cracking. And when getting new tyres fitted the tyre shop should be asked to carefully check each wheel for hairline cracks, especially on the inner edge of the wheel. That should keep you safe. 

Cheers...

[jon dee 500]

That's not a crack... THIS is a CRACK !!!

Understood to be from a 328xi on runflats. I'm lead to believe that when something like this happens, runflats may actually hold the wheel together for long enough to get the vehicle off the road to safety. But I sure wouldn't want to be the one testing the truth of that conjecture at 100kph

Cheers...