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Friday, September 22, 2017

Wheel failures and "Silent Recall"

I have been seeing a number of posts on an RV Forum about cracked and leaking cast aluminum wheels on one brand of RV trailer. Some owners are reporting more than one failure.
There appears to have been a manufacturing defect in the casting process which results in stress/fatigue cracks that eventually may lead to air leaking from the tires.

Some folks are "lucky"(?) and are discovering the leak before there is a tire failure or the wheel fails and damages the RV. Others have reported damage.

It appears that the wheel provider is aware of the problem, as many are reporting that replacement wheels are being provided and the cost of dismount and mount of tires is being paid for with no argument from the supplier.

I have advised the readers of that forum of a few important things:

1. They should be filing complaints with NHTSA as IMO multiple failures of this type should be investigated with the potential for a federally mandated recall and free replacement.

2. If the wheel supplier is quickly replacing these failed wheels, it appears they are fully aware of the problem and should have reported it to NHTSA per federal regulation.

3. I am concerned that tires on these wheels may be suffering internal structural damage from being run under-inflated. This damage may result in tire failure at some later date. It is entirely possible that owners may not connect the loss of air due to the wheel problem with the tire failures.

4. If the supplier is aware of the problem but has not initiated a recall or made public the facts but are simply replacing the wheels if or when someone reports the failure, this is what is known as a "silent recall," which is operating against federal regulations.


Thursday, September 14, 2017

Can I change from 275 to 295 size tires?

Read this post on an RV forum:

"I need 6 new tires for '04 Dutch Star 38' on a Spartan chassis. Michelin tire models and sizing has me totally confused. Current Michelin size is 275/80R22.5. Dealers claim this Michelin size is interchangeable to 295/75R22.5 from brands that don't offer the original size. They tell me there will be no ill effects on the drive line or instrumentation."

I was concerned with this possibly incorrect information. In this case the two sizes have the same load capacities so that was not my concern.

Some folks replied to the original question by suggesting he use THIS or similar web sites to learn about tire sizes. I did have a little problem of using such a "tire size" site as the information is aimed at car application and does not include special information regarding dual tire application. Also the resulting numbers may or may not match published industry standards.

I pointed out my concern about the Minimum Dual Spacing which is a published dimension in industry standards and has been covered previously in this blog.

Some folks reported that they have changes tire sizes and had no problems and implying that any change might be OK.

I provided this graphic to help people understand what this dimension is.

As you can see the wheel offset and even wheel thickness can have an affect on this spacing. I also pointed out this example.  275's have a MDS of 12.24 and 295's have a MDS of 13.19.
Let's assume that with your wheels and with the 275's you have a physical 1.00" clearance down at the bulge in the sidewall near the road. So if you don't change wheels and put wider 295's on the new clearance will be   1.00 - ( 13.19 - 12.24) or  1.00-0.95  or a final clearance of 0.05"which is clearly too small.

I hope that those considering changing tire size consider not only the load capacity, which is very important but also the dimensions.