Suspension Creak

[GDeen]

Brian - thanks for the excellent explanation for the newbie still trying to learn his way around these things.

[Jon Wehrenberg]

I have a straight axle so bushings are not a typical service item, but I question why it appears they have a short life.

I drive and have driven cars and my buses for years and a lot of miles and have never replaced any rubber or urethane bushings in the suspension, sway bars, or any other undercarriage components. I understand rubber or similar materials age, get brittle and crack, but something seems to suggest to me at the young age and low miles reported for these replacements if something else is not at play here.

Are the parts clearly lined up when reassembled? Is there any indication of forces or stresses in a direction that would compromise the life of the bushings? Are any of the buses exceeding the axle weight limitations? Given the presumed service life of these coaches, if bushings are a routine maintenance item I would think the Prevost maintenance schedule would spell out when they would be replaced. Otherwise it seems something may not be right.

[BrianE]

Couldn't agree with you more Jon. The sad fact is that the front end suspension bushings seem to have a very short life indeed. The IFS buses get noisy and "clunky" when these bushings get worn. There are small urethane bushings associated with the front and rear sway bars that seem to be especially prone to short life. They are easy to replace and in my case component alignment was very good. Haven't a clue why this happens.

[dale farley]

I replaced all those orange bushings in my front and rear sway bars when I first got the bus (70K miles). A couple of them were completely worn out. The good thing, is that it was an easy and quick fix, and all the parts cost about $50 total. I think Jim Keller said that a Prevost tech told him that these orange bushing need to be replaced about every 60K miles.

[GDeen]

Many of my sway bar bushings were completely gone when I had Prevost put the bus on the lifts in January. The remaining ones were badly worn. Good news is that replacing them tightened up the ride considerably, and eliminated the groaning I was hearing on dips. Will keep an eye on them.

[Jon Wehrenberg]

I have a sway bar and there are no indications of wear or the need to replace. About 230,000 miles and 14 years old. Since a sway bar just resists lean and is common to IFS and straight axle coaches, is there something in the rolling motion of IFS suspensions that put unusual forces on the sway bar bushings?

I cannot imagine entertainer coaches getting bushings replaced at the miles suggested here.

[JIM KELLER]

Dog bone bushings is what the Prevost Tech called them when installed at 60,000 miles in my Bus. At 100,000 miles we are starting to get the same type noise again.

[truk4u]

Brian,

Orange bushings, noisy front end...... I don't have any of them there hickeys on the Green Machine!

[BrianE]

Male bus owners as viewed by some female bus owners. Older is less complicated, less independent, has fewer moving parts and is usually more reliable. They do creak occasionally however, which can be temporarily corrected with proper lubricants.

[Jon Wehrenberg]

It would be too easy to just throw stones at the IFS, but while more complex, I don't think an IFS front end should require maintenance at the short intervals reported here. If Jim Keller is averaging 50,000 miles for bushing replacement it suggest commercial and entertainer operators are pulling their coaches out of service every 6 months or so to replace bushings. If that is the case Prevost won't be serving that marketplace very long.

Remember these are the folks that may run their oil changes to 20,000 or 30,000 mile intervals so it seems absurd to consider bushing replacement at intervals just a little longer than oil filter change intervals. Something smells very fishy.

Remember IFS owners, our cars have had front ends that use the same technology for many years. Those front ends use A frames with rubber bushings, sway bars, and they can go decades and hundreds of thousands of miles with zero maintenance on the bushings. I think something is wrong if a commercial vehicle designed to have a service life 5 or 10 times that of the average car can have such a design defect.