M450 Steer Tire BlowOut

[dentmac]

Hi,
It is exactly the same axle in both vehicles.
The recall was called as it was found the tie rods were manufactured with a lesser steel then the specs. This was learned when Bluebird tried to upgrade the axle to 18,000GAWR. The tierod had to be upgraded to pass the 17,000 rating. The tie rod is actually rated to 18,000. but the rest of the axle and components could not be up rated to more then 17,000 even with the reduced testing criteria used.
It was later realized that the tie rod was a safety issue to the 16,000 GAWR transit buses so a new recall for them was posted.
So the only official recall remedy was to replace tierods, change tires (same size and rating), alignment and add placards. Reducing weight had no methods listed but included using different weighing criteria and reducing tag load.


Ross,

As you know, this same Meritor IFS is also fitted to the M380. Although I have no data to confirm, I haven’t heard of this problem happening on the M380. I think that some parts of the Meritor IFS were beefed up on the units fitted to the M450. We also know that BB recalled the M450 and made modifications to lower the weight load on the IFS and front tires.

So the questions that should be asked are: Why is this happening on the M450 and not on the M380? How close are the steer axle/tire weight loads comparing the M450 with the M380? What (if any) are the differences in the Meritor IFS fitted to the M380 versus the M450? Are the alignment specifications the same? Is the wheel cut the same? Is the suspension the same? Is there some modification to the suspension on a M450 that allows too much weight transfer/load on a single steer tire around a curve?

If we can document the differences between the two applications, we may be able to better define the cause.

Chuck
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