Trailing arm bushings, 2 Q's Options

[toon1]

I pulled the trailing arms today and the bushings look ok.

HOw can I check them to see if they are still usable?

Will the stock bushings survive powder coating?

[Katmanken]

Roller bearings are unidirectional and will rotate in both directions equally well.

That being said, the trailing arms normally operate in a limited angular travel (10-15 degrees?) when driving sedately on smooth roads, and experience more angular travel for bumps, potholes, and spirited driving.

So, for the majority of the time, the small diameter rollers are going back and forth over a small section of the race and you might get localized wear. Another point to consider is the small surface contact area of a roller on a shaft. This will result in high stress loads (Pounds/Area) at the contact points.

Hmmm, brinneling (back and forth partial rotation and fretting) of the bearings is another thing to design around. Had a professor in college who worked at GM and talked about a brinneling issue with automotive wheel bearings. They traced it to shipping cars on trains and the constant click clack of going over rail joints which caused the cars to move back and forth slightly and to brinnel the wheelbearings. The frequency of the click clack was related to the speed of the train and the failure as well as the large diameter balls in the wheel bearings. Large diameter balls meant the ball couldn't rotate fully but only over a small area of the surface and caused brinneling. Smaller balls was part of the fix.

Hopefully, the Chinese haven't got into the bearing business as the FAG and Fafner and Torrington companies used to be extremely fanatical in making quality products. With bearings, it's all about correct matrials, ultra rigerous manufacturing processes and tolerances, smooooth surface finishes, and material processes (heat treating). An oops in any one of those areas results in early wear and failure, and from my personal experience the Chinese would ship it anyway -until busted and then deny.

The short of it? Main bearings are long for lower stresses (good), roller diameters are small to maximize rotation of the rollers during movement (good for brinneling issues), and racing would consistently maximize loads and accelerate wear. Seems a lot of teams are using them. That statement about directional bearings is BS. And yes, I've designed products with both the one way and the universal rollers. Also did a lot of linear bearing work and plastic bearings with certain specialty nylons (Rulons) and plain old delrins work really good and last forever. Plastics are prolly great for the trailing arms- ask Racer Chris about his process.

Ken