SOHC.co.uk Forums > CB500/550
Not understanding 500 front suspension 🤔
K2-K6:
Apologies Ted as I now think I didn't understand the status of components in original question, in that the spacers fitted are Honda's original equipment. I read that the other way now, is that correct ?
If so, then agree that fitting with just the springs is correct to assess what it's like.
To expand verification, preload is used to set "sag" if the spring rate is correct to carry the mass of vehicle and rider. Sag being how much the vehicle sits down into it's suspension expressed usually as % of total travel and with 20% being fairly normal.
This can be checked simply by sitting on the bike static and measuring how much it sits below maximum extension, often done with an O-ring pre fitted to one stanchion to let you see where it was after dismounting to have a look.
Purpose of sag is that any suspension sitting right at maximum extension in normal use has no capacity to cope with any quick extension due to road surface deformity. Usually set that way, the fork will "thunk" on minor road irregularities as it hits the top out provision and subsequently drive you nuts :) you want to try and avoid thunking definitely ;D
Progressive wound springs will work exactly the same either way up. Pedantic assessment will have them fitted with tightening coils at the top as best positioned with any extra weight then being on the sprung mass rather than adding to unsprung mass of the wheel assembly. In reality, although correct, it's highly unlikely anyone will be able to feel any difference as those grams have such a tiny additional contribution to wheel, brake, fork sliders etc.
The oil you use will control how quickly they respond to input. They seem to favour 5 viscosity or even 2.5 to let them move nicely on a road bike such that the fork can easily move in response to road riding (as opposed to someone that may want a more restricted control for higher pace applications) the 2.5 viscosity gives very good compliance for smooth ride in day to day riding. I like Motul fork oil as it gives that choice along with very good friction reduction to enhance that response by reducing stiction.
taysidedragon:
Ted, instead of jumping straight in and using helicoils on the fork legs, it's worth trying a medium strength Loctite on the mudguard screws. Just nip them up lightly and let the Loctite take up any 'play' in the threads.
It'll hold them fine, unless the thread is virtually bare.
McCabe-Thiele (Ted):
Not sure what would happen with Locktite on the threads if I had to undo them in the future. One thread has a very short Helicoil in it already. The second thread is worn at the top but better part way down I've cleaned it out with a tap so the lower part of the thread should hold. I was going to leave it like that but it's a load of work if the mudguard shakes loose - I thought fix it once fix it right.
The spacers fitted are definitely not original.
taysidedragon:
Use a medium strength threadlock, they are designed to be dismantled when necessary. No problem coming apart on a little screw like that.
McCabe-Thiele (Ted):
--- Quote from: K2-K6 on January 06, 2023, 11:15:04 AM ---
Purpose of sag is that any suspension sitting right at maximum extension in normal use has no capacity to cope with any quick extension due to road surface deformity. Usually set that way, the fork will "thunk" on minor road irregularities as it hits the top out provision and subsequently drive you nuts :) you want to try and avoid thunking definitely ;D
Progressive wound springs will work exactly the same either way up. Pedantic assessment will have them fitted with tightening coils at the top as best positioned with any extra weight then being on the sprung mass rather than adding to unsprung mass of the wheel assembly. In reality, although correct, it's highly unlikely anyone will be able to feel any difference as those grams have such a tiny additional contribution to wheel, brake, fork sliders etc.
--- End quote ---
Interestingly there was an odd clunk on the front suspension when I rode the bike before strip down - it felt like a metal on metal clunk as if the suspension was bottoming out - it was after hard braking - it was not a good sound - it sounded like just one side but hard to be sure.
So from what you are saying about un-sprung weight the tighter coils should strictly be at the top.
As you can see in the earlier photo the coils were well distorted even at rest due to the high pre-load .
Might it be worthwhile fitting a smaller spacers in the light of your comments about avoiding thunking or have I misunderstood you?
Fitting 10 mm spacers would be quite easy as would 5mm or none.
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