Author Topic: Freehub not freewheeling continuously  (Read 387 times)

Freehub not freewheeling continuously
« on: February 11, 2019, 10:57:23 am »
I was out for a ride yesterday with some friends who were on their tandem.  When they went to freewheel the cassette would appear to try to turn with the wheel pushing the top run of the chain and causing a tangle.  Not all the time but most of the time.  When the tension in the lower run became high enough, if it wasn't too tangled, the derailleur was able to pull everything back into place.  The wheel bearings in the Shimano hub had recently been serviced.  They had to ride constantly pedalling even to almost a standstill.  No easy feat on a tandem.

I thought too much grease around the pawls, yay or nay?

zigzag

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Re: Freehub not freewheeling continuously
« Reply #1 on: February 11, 2019, 01:51:44 pm »
i suggest that it gets sorted out asap before too much damage has been caused (e.g. mech wrapped and pushed into spokes). most likely it will either be grease in the freehub that got stiff or a freehub seal (if there is one) dragging against the hub shell.

Re: Freehub not freewheeling continuously
« Reply #2 on: February 11, 2019, 03:01:18 pm »
which may go to show that it is pointless doing things to the hub bearings without also giving some thought to the freehub body bearings. 


there are several things which may cause a freehub to go draggy

1) particles inside. If there is no slack at all in the bearings (normally a good thing) the slightest contamination of the lubricant may cause the freehub not to spin properly.

2) grease drag. If a #2 grease is used and it gets into the freehub body the freewheeling action may go very draggy.

3) lack of lubricant/corrosion. If the hub was serviced because it was going bad inside, and nothing was done to the freehub bearings, they won't have been improved in any way.

4) Badly fitted seals; there is usually a seal or shield that is push-fitted in the freehub body. If this comes loose (not uncommon) or is not a tight fit when refitted (NB the pressed steel variety always need to be re-flared before being refitted, IME) then they can rub and this can cause the freewheeling action to go bad, either directly or because there is debris generated.

5) Poor lubrication. Under certain conditions (eg very sticky lube) the pawls can be dragged round with the moving part of the freehub body and this can cause the freehub to go snatchy. I have even seen brand new hubs that did this. In most cases simply oiling the freehub fixes the problem.


So there are several possible mechanisms but one probable  common underlying cause; it is quite likely that insufficient attention was paid to the freehub body itself.

If there are no signs of trouble it is normally sufficient to add oil to the freehub body, work it to make sure that it isn't full of rust or dried grease (look at the oil coming out as you work it, and listen to the mechanism) and then to use enough SFG so that this will over time penetrate the mechanism without causing excessive drag. The result is usually a nice quiet freehub that doesn't go wrong.  However if the freehub is bad it will need to be overahuled or replaced.

cheers

Re: Freehub not freewheeling continuously
« Reply #3 on: February 11, 2019, 03:08:46 pm »
use enough SFG

Sorry Brucey, SFG???

Re: Freehub not freewheeling continuously
« Reply #4 on: February 11, 2019, 05:45:17 pm »
use enough SFG

Sorry Brucey, SFG???

Semi Fluid Grease.   a lubricant that has about the same consistency as tomato ketchup will work OK in a freehub (in fact it will work in the whole rear hub provided it has some kind of seals fitted).

cheers