Topic: Swing arm roller bearings

[mrblasty]

I've got a k3 cb 750 and was wondering if they are available for my bike?

[mick750F]

  I've seen them on ebay...kinda pricey if I remember right. I just replaced my stock  "whatever the hell they used" bushings with bronze. They're an upgrade but only cost $20-25. The originals were some kind of composite. I had to break them apart to get them out. Can't see how Honda expected them to last a long time...but maybe they didn't.

Mike

[Terry in Australia]

G'Day Mr B, they appear infrequently on Ebay, but I bought a set and don't think much of them. I had to turn up some stainless sleeves to shim the swingarm shaft as it was a real sloppy fit, and really, the only reason that I persisted was the "novelty" value of having them.

Since installing them I've been commissioned to replace the needle roller bearings on a Suzuki Motocross bike with bronze bushes and I've converted my own GS1000S swingarm to bronze bushes as well, after seeing the damage in these two bikes. Motorcycle needle rollers are not as tough as bushes, are badly effected by water ingress so require a lot more maintenance, and are horribly expensive to replace, because they are mostly "One Off" sizes not available from bearing suppliers.  

My favourite bathroom reading (apart from the tattered mess that was once a pristine Spanish Penthouse magazine) is "Great Bikes of the '70's" and interestingly one of the "update" recommendations for Suzuki's venerable GS750 was to replace the needle roller swingarm bearings with bronze bushes! (I wish I had read that before I went to the expense of buying the needle roller bearing kit!) Cheers, Terry.

[mrblasty]

Thanks guys, now where can I get the bronze bushings? Locally I was quoted 130.00 for the center collar and pivot bushings. seems kinda steep.

[SteveD CB500F]

Original bushes £8.50 from DSS

[Raul CB750K1]

My favourite bathroom reading (apart from the tattered mess that was once a pristine Spanish Penthouse magazine) is "Great Bikes of the '70's" and

Man, that hurts!!!! I thought you will care more for them, at your age you should be able to know when it's time to close the magazine and let nature and blood accumulation do the rest.... HAHAHAHAHAHAHA


Raul


P.S. I will upgrade to bronze as soon as the need arise. I was before one of those who "well, as I'm on it, let's do it". Now I'm more of "if it works, don't fix it".

[bryanj]

I dont know what the composite is either but from experience the pin wears more than the bushes!! problem with both needle roller swing arm AND taper roller headstock bearings is that both are designed as contiuously rolling bearings not 10 degree either side of a static position so they "notch" the shaft/races

[Terry in Australia]

Bryan, I regard you as one of the more technically astute contributors to this worthy tombe, so don't think that I'm questioning your profound wisdom for one moment, but could you explain to me the advantages of ball over roller bearings, in relation to their relative uses in headstocks and swingarms?

If tapered rollers are more suited to wheel bearings, (continuous rolling) then why are our Honda wheel bearings of the "ball" variety? To go a step further, all the bicycles I've owned have rolled along on "ball and races", which your post suggests would be better in headstocks, and perhaps swingarms?

It's been my experience that the swingarm sleeves wear due more to no grease/water ingress, I really can't see how a bronze, plastic or even mild steel bush will wear slower against a hardened steel sleeve? Most of the ones that I've seen are badly rust pitted, like the top 8 inches of early CB750K forks, where the factory decided to save 10 cents on hard chrome per unit? I used to "chuck" the pitted sleeves, but now I machine them on the lathe and turn up oversize bronze bushes to compensate. Cheers, Terry.    

[Bodi]

Tapered roller bearings are excellent for things with high radial and axial loads. Ball bearings - at least the single row complete type we see in our wheels - are good for radial loads but poor at axial loads. Cars create large axial forces when cornering so ball bearings are not good for car wheels. Bikes lean into corners and the wheels present almost pure radial load on the bearings, so ball bearings are fine. Roller bearings will have more friction than ball bearings. They also cost more and are more complicated to install properly. There's no reason to use tapered roller bearings on a motorcycle wheel except in exceptional cases.
The steering stem has a special type of ball bearing, the races are inclined to accept axial loads and radial loads. Tapered roller bearings would be an OK choice too - despite somewhat higher friction - and their axial load rating is much higher than the ball ones. Honda probably used the ball bearings for cost reasons but the ball type are entirely suitable for the load presented. Only after years of service or abuse - there is a recommended repack interval much shorter than 30 years - will the stem bearings cause trouble.
Plain bearings (bushings) are well suited to the swingarm.. If the materials are chosen properly and the bearing is kept lubricated wear will be negligible. Straight roller bearings - for a similar tolerance - will have less friction than a plain bearing but will be more susceptible to dirt and water damage because there's always a space between rollers.

[bryanj]

Terry, didnt mean to say dont use them just dont expect them to be a cure all and last longer than the original parts. People seem to have the idea that if they fit taper roller head races they will never have another problem WRONG all i was trying to say is that both rollers and tapers will notch up with the loadings we apply to them. Taper wheel bearings on a car nearly always fail because of Brinelling ( not sure of spelling) when the hardening on the rollers/races gives up, i have actually seen taper headstock bearings shatter with an impact load!--NOT VERY OFTEN and usually a "cheap" bearing As to roller swing arm you yourself hit it on the head when you said it wasnt easy to keep water out, a bush will always smear the grease whilst a roller has to roll to spread it and the movement just aint enough BUT whilst they are in good order there is less friction and usually a tighter tolerance so less play