Trailing arm bushings, 2 Q's Options

[Mueller]

Ummmm.... Roller as in needle? Don't do that.... You will be sorry if you do that. Do the Elephant racing bearings. Your car will be that much nicer.

I have yet to have one return on the bearings due to abnormal wear...will they wear, yes, all things that turn will eventually wear....and yes, roller bearings are the happiest when spun in a continous manner (they are not one-directional unless you have the clutch type)


The bronze bushings will also wear down and will need periodic checking/greasing as well. There is no one perfect solution, if it moves, it will need checking/replacing sometime in the future.

Being that the needle bearings have more parts per assembly, yes, there is a much greater chance of something failing, if a something goes wrong with a bronze bushing, more than likely all that will happen is the clearances between the bushing and the sleeve gets bigger and you'll have some looseness in the suspension.

[PRS914-6]

Regarding the needle bearings and one direction.....Think about a u-joint on a car! Under a heavy load and go back and forth all day. In fact, if you don't have your drive shaft at a slight angle the u-joints won't last due to lack of movement.

Needles are probably overkill for the application but I certainly don't see anything wrong with it, just another way to address the problem.

With that said I used the Elephant setup. Simple, compliant and easy.

[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

[Bartlett 914]

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

That was a great writeup! Thanks for sharing

[burton73]

At was at the same place as you when picking bearing or bushing for my 914-6, I asked Eric, I bought from Eric. I was willing to spent for the very best for my driving. Eric picked Elephant setup for the rear and front. Look at this from Elephant explaining the Tech Topic of Needle Bearing Suspension. They are all big bucks.

Regards 914 Bros,
Bob Burton

http://www.elephantracing.com/techtopic/rollerbearings.htm
(IMG:style_emoticons/default/driving.gif)

[PeeGreen 914]

lol... thanks Bob. I was just told to look at the write up that Elephant had on there site as to why they aren't very good, and then I see you posted the link. How convenient. As to what I was saying about it being unidirectional I was wrong. He said that it was because they don't rotate fully causing an usual wear. I knew it had something to do with rotation.

[roadster fan]

Thanks for the link to elephant and the explanation on needle bearing wear. I had heard about this issue, but as the saying goes, a picture is worth a thousand words.

With quality components I suppose the life span of the needle/roller setup could be exceptional and I suspect that is what the Mueller setup brings to the table. It looks like the design and execution are top notch and if maintained properly would be great

Jim

[Katmanken]

I would also think that race cars would wear worse than street cars.

Why? Drive a race car and it is stiffened up to corner well and to reduce body roll- both of which would reduce trailing arm travel.

On a "softer" street car, the rollers will be able to roll farther as the trailing arm moves up and down more.

In any bearing designed to work with grease, if you don't lube it, it will accelerate the wear. Delrin needs no lube and the rulon nylons have telflon mixed in them.

Ken

[Brando]

On a side note... Roller bearings would be awesome on a soft and very lifted rallye car (IMG:style_emoticons/default/smile.gif)

[Aaron Cox]

what is the diameter of each roller in the roller bearing?

im guessing that a few inches of suspension travel are enough for each roller to complete a full revolution around the shaft.... thus no 'flat' or 'worn' spots....


just a hunch

[neo914-6]

Who has actually measured a brinneling issue in our application? A company that promotes an alternative bushing? (IMG:style_emoticons/default/idea.gif) Tarret, Shrine Racing, and others sold alot of needle bearing kits for 914's without problems. Smart Racing sells a WEVO needle bearing for 911's spring plates.

The only downside I see is that needle bearings are relatively expensive and need more maintenance than the alternatives. Chose your bushing types to your budget and comfort level. I chose mine for a modern ride... (IMG:style_emoticons/default/smile.gif)