Yet Another Cycling Forum
General Category => The Knowledge => Topic started by: quixoticgeek on 13 September, 2017, 03:05:42 pm
-
Just bought a Shimano FHM756 rear hub. It arrived in the post today. Taking it out the box, rotation feels somewhat rough. For what should be a brand new hub, this surprises me. Is this an instant return the hub job, or should I try to adjust the loading on the bearings first?
J
-
That depends on what “somewhat rough” means. Even my Shimano 105 hubs with Borazon-polished bearing surfaces were not perfectly smooth in the manner of viscous drag. There was perceptible variation in drag when twiddling the axle between finger and thumb. (They were still the smoothest hubs I’ve ever taken out of a box.)
Many hubs become smoother with a little use, thereafter remaining smooth until the bearing surfaces fatigue and become pitted.
In my experience, all Shimano hubs come with excessive preload that exacerbates any roughness. If you reduce it, be careful not to mar the cones and lock-nuts lest you do want to return the hub.
-
Probably just not adjusted properly. It's not very unusual to get hubs supplied like that, sadly. It's good to always fine tune cup-and-cone bearings before first use anyway.
-
Probably just not adjusted properly. It's not very unusual to get hubs supplied like that, sadly. It's good to always fine tune cup-and-cone bearings before first use anyway.
Cool, thought so.
J
-
Shimano hubs are often supplied with bearings that are a bit tight. However there is stuff-all point in adjusting the bearings 'perfectly' for a hub in a box. The reasons for this are severalfold
1) the bearing adjustment will change when the wheel is built (the spoke loadings deform the hubshell)
2) the correct adjustment is a little free play that just disappears as the QR is tightened; unless you can tighten the QR this much in the wheelbuilding fixture, the free play in 'a perfectly adjusted hub' will prevent you from truing the wheel perfectly.
3) the hub bearings do 'bed in' slightly over time, and will probably benefit from readjustment after a period of time anyway.
So yes, you should readjust the hub, but probably a waste of time before the wheel is built and correctly tensioned.
cheers
-
The two Deore hubs I got recently were far too tight out of the box. Quality control is weak at the cheaper end.
-
Some arrive so tight that I'd worry about damage if spun at all like that. It's not pleasant anyway. Loosen straight away and fine tune after the wheel is built.
-
I've had new shimano hubs that lacked any grease on one side...
-
I've had new shimano hubs that lacked any grease on one side...
probably best if you treat them all as if they have no grease in; there is very rarely very much of it and the stuff they use is not at all proof against the British weather....
cheers