Dominator silentbloc upgrade

My dominator came with the 'Manx' style bronze bushings fitted but I was never happy with it.  Whoever fitted the bushes had made a bit of a hash of it as there was side play and misalignment - I really think the bushes need fitting very slightly undersize and then line reaming to fit. 

After too much faffing about with the bronze bushes, I removed them and and upgraded/downgraded to silentbloc bushes and have never looked back - they worked perfectly from the outset.

A little flex is good . gives a warning if you are going past normal limits, a totally rigid frame  can be unforgiving  and is likely to fracture  if overpowered  and  fitted with very grippy tyres.

And wish I hadn't bothered. It is a solution looking for a question.

Making inner sleeves and the bronze bushes,rebates for oil seals, working out oil supply route, and then after assembling having to get bushes line reamed for what?

 I did it because, as an Engineer it seemed to be more "correct", but what did I achieve? More maintenance chores, another place for oil film to hold dirt and that is about it. I certainly wouldn't know when riding the bike that it had a 'zero play' swinging arm pivot, and I doubt if anyone else would be able to tell either. 

The original system works really well and the silentblocs last forever - people have powder coated the swinging arm with them in and they sre still ok afterwards. Without any maintenance the handling is still top rate with them so I have to say why bother? If you intend to 'show' the bike, I suggest that you spend your time and money on other bits and bobs that will make a genuine difference to your bike - brakes, electrics etc.

But, it is YOUR bike, so if you want them, go ahead! Like my 650, it will give the rivet counters something to tut tut about!

Regards, George. 

I had my swinging arm stoved by the same people who do Norman White's stuff and they said that the Silentblocs are OK afterwards.  As theirs is the voice of experience I'm happy that they seem fine.

It always seems odd to me, who has had more experience with cars than bikes, that the centre axle isn't free in t he centre bush.  In cars, that sort of bushing normally has the centre free to rotate within the bush.  Very commonly used in suspension bushes.  The Silentblocs are rigid and the axle doesn't rotate - or should it?

I had my swinging arm, (and other things) stove enamelled and when I collected it the silentblocs had completely gone, burned away, the central spacer tube was still there, retained by the outer sleeves of the bushes.

I was as careful as I possibly could be, but but the time that I had got the old outer sleeves out, cleaned the bore up and pressed the new SBs in, the enamel was in a right mess, so if I ever do it again, I will take them out first.

FWIW, in my opinion, the Manx type bushes are unnecessary for road use.

The inner sleeves of the SBs should be gripped by the clamping action of the spindle, and about 30 degrees of rotation available by torsion of the bushes.

The axle should grip the central steel tubes solidly so the only place where rotation takes place is inside the rubber. It should be tightened up with a load on the saddle so the rubber has little or no twist when running on a smooth surface.

No metal to metal movement means nothing to wear out until the rubber goes after many decades in service. Since hardly any of the rubber is exposed to ozone, oil or ultraviolet light, it might last almost forever.

If it does move, it can wear a hole into the frame, and some stiff washers can be needed to stop further frame damage before a weld repair is needed.

Not too long ago, Featherbed Frame Upgrade Specialists such as Unity Equipe,  Dresda Autos & others used to offer basic swinging arm Taper Roller or Bronze Bearing conversion kits. For a few bucks more you could alternatively purchase a box alloy or similar almost ready to fit complete swinging arm. The advantage being two-fold. The replacement swinging arm could take a much wider rear tyre and the engine could be tuned without the worry of the increase in power pulling the wheels out of alignment due to the Silent Blocs getting crushed.