Please diagnose these problems (video)

muran

Can someone please help find what's causing these issues?

1) Bike bbouncing up and down when pedalled at speed

2) Rumbling noise from rear when freewheeling.

Notice the rumbling is quitened when the crank is turned in the pedalling direction when freewheeling but the noise becomes a lot louder as I turn the crank against the pedalling direction when freewheeling.

I should add that the rear hub bearings have been checked and are fine.

VIDEO HERE

Thanks.

386ka

Maybe the freehub needs to be regreased or cleaned. Also, every bike will start to bounce up and down like it did with yours. I think no wheel is perfectly balanced. Still, check if the wheel is true.

muran

Thanks for your feedback, it's encouraging to know they all bounce but this seems really severe. Can easily feel it through the frame when upside down and pedalling (and see it). Seems worse with new tyre also for some reason.

If it's a freehub problem which it may well be, I'm puzzled as to why turning the crank would alter the noise?

386ka

If turning in the pedaling direction, you are engaging the freehub pawls, so it makes no noise. If you aren't pedaling, or pedaling backwards, the pawls slide off the splines and create noise.

As I said above, my bike also does that when put in a stand, but I don't see it as a problem. IMO I think that it is a rim+tyre balancing issue, they can never be balanced perfectly, and under high speed there is bobing, something like an excenter would do. The wheels are planted on the ground and your weight doesn't allow it to become a noticeable problem. You don't use the bike upside down, don't you?

muran

Ok, makes sense - so the freehub needs an overhaul you reckon? I tried to look at all that when the wheel was off for the bearings to be checked and greased but couldn't really see where to go with it.

I haven't been out on the bike since fitting the tyres so I don't know how it performs on the road yet. If the vibration doesn't really show I'm happy to live with it but I would really like to get rid of the noise.

Thanks for your help - as you can maybe tell I am kinda' new to this! :-)

Greer_

muran wrote:

1) Bike bbouncing up and down when pedalled at speed

2) Rumbling noise from rear when freewheeling.

Notice the rumbling is quitened when the crank is turned in the pedalling direction when freewheeling but the noise becomes a lot louder as I turn the crank against the pedalling direction when freewheeling.

1) that's just what happens with the force/speed. Its not transferring the force onto anything i.e. the ground, so it wobbles

2) Agree with above ^

386ka

muran wrote:

Ok, makes sense - so the freehub needs an overhaul you reckon? I tried to look at all that when the wheel was off for the bearings to be checked and greased but couldn't really see where to go with it.

I haven't been out on the bike since fitting the tyres so I don't know how it performs on the road yet. If the vibration doesn't really show I'm happy to live with it but I would really like to get rid of the noise.

Thanks for your help - as you can maybe tell I am kinda' new to this! :-)

Are you sure it is not a normal sound of a freehub? Some are quiet, some are quite noisy.

The freehub has nothing to do with the bearings overhaul you did, as you can guess.

delcol

you say you installed new tyres so first off make sure they a seated properly..

i had a simlar issue with my old hardtail the missus uses it to commute on and was complaining about it bobing up and down. very simlay to your rear wheel in that video...
it ended being out of true i think it's refared t as radial true.. pretty easy fix.

see
park tools

Ghostt

delcol wrote:

you say you installed new tyres so first off make sure they a seated properly..
very simlay to your rear wheel in that video...
it ended being out of true i think it's refared t as radial true.. pretty easy fix.

This. (Although I'm not sure what's happened to Delcol's typing ability!)

Also worth double checking the rear wheel is seated in the dropouts properly.

And a bike shouldn't 'bounce up and down' by itself if everything is set up properly. Most do though because of untrue wheels/badly seated tyres, which if minor aren't really a problem.

The Spiderman

The up and down may be partly due to the wheel being out of vertical true:ie the wheel is slightly out of round.
Having said that it isn`t uncommon and won`t necessarily be a problem when the bike is ridden,but a bit of tweaking of the spokes,working on opposite sides of the wheel may help.

If its a Shimano freehub they aren`t really serviceable.You might be able to clean it up and stick some oil in it but if it is failing it is normally a case of replacement.New freehub is around £20.

bikaholic

Remove the pie plate to make sure that it's not the cause of the rumbling sound.

muran

Once again, some very helpful replies. I think for now I will ride the bike as is and try and ignore these problems as it doesn't seem to affect ride quality (I am not noticing any adverse effects).

Just to pick up on a couple of points:

The tyres are definitely seated correctly, I have fitted and refitted and even swapped the inner tubes over, thinking that puncture repairs could be causing the problem - no change.

The wheel I am pretty sure is seated in the dropouts correctly although this does seem to be almost a two stage fit and requires a little force to locate properly. Pretty sure it's right though.

The freehub is a bit noisy when spinning freely 3 without the cassette attached and the cassette itself when attached seems to have a little play in it, maybe this is a contributing factor - not sure whether to the noise or the wobble though ... or both!

I guess the wheel may be out of true as some have suggested, although I'm not about to start getting handy with a spoke spanner given the little bike knowledge I have and I really don't want the cost of taking it to a specialist who may or may not find lots of other things wrong also that I would rather not know about!

Thanks all for all your input!

The Spiderman

My LBS only charges a tenner for a wheel true.