Strange feeling from my rear wheel

[Mark Turner]

Hi

I have recently bought a road bike, Cannondale Synapse Sora 2011. It is a great bike and I am really enjoying it but have noticed a strange quirk.

When I cycle fast downhill and hit speeds in excess of 40 mph I get a pulling/ wobbling sensation from the rear wheel on each down stroke from my right pedal.

Is this normal or should I have the rear wheel checked out for balance. I've only done 250 miles on it so far and it looks like its true.

Any advice appreciated.

Cheers

Mark

[cycle cat]

It's difficult to tell from just a description.
What sort of wheel is it?
Get it checked out by your local wheel builder.
Wheels can go all wobbly for a number of reasons.
Check the hub for play or damage to the bearings.
Check the axle isn't bent or broken.
Check the spokes are all tight, the spoke flanges are not cracked and the rim is straight.
A bent rim can sometimes do this at speed.

Speed magnifies any wobbles or problems. You can't always see them by eye.
Is the wheel tight in the frame and properly centred?
Something is either loose or bent!
Get it fixed before you have an accident.

[Snowflake]

If it helps............probably not.......

I've spent some time behind Mark (in the nicest possible way), and the rear wheel of the bike is completely true. If this was a car\motorbike it would be a wheel balancing thing, a wobble at speed 'x'

Given its a pedal iron, surely wheel balancing isn't an issue...

Ta

S

[cycle cat]

How can you tell if a wheel is perfectly true just by riding behind someone?
Wheel builders use jigs to check.

[JohnW]

Have you had your right knee checked recently?

[Snowflake]

How can you tell if a wheel is perfectly true just by riding behind someone?
Wheel builders use jigs to check.

Because its shape changes.....or am I missing something?

S

[thirdcrank]

I don't really understand what you are describing.

If it was something broken, I'd expect it to be most obvious riding uphill. Even a slight distortion of a wheel or tyre would come up through the back of the bike, even at slow speed on a smooth surface. Have you tried putting the bike up on a workstand, or even getting somebody else to lift it up while you pedal it by hand? The crank / back wheel relationship made me think of how a freewheel "wobbles" when freewheeling at speed. On a workstand, that can be enough to make the chainset wobble as well, but if this happens when you are pedalling, that wobble is irrelevant. (I'm not even sure if it happens with a freehub anyway.)

I think that if you had mentioned in sensation from the R crank without mentioning the back wheel - which could be a red herring anyway, I'd have been suggesting a loose crank, but that would be much more obvious uphill.

[mig]

what gear are you pedalling to be still making a significant contribution from the pedals at 40mph+ downhill? 53 or 54/11?

my first feeling would be that it's a worn chain placed under duress with the load involved as it's on the right hand side.

[Edwards]

Try lifting the rear wheel of the floor. Then give the top of the rim a good push pull and check for any movement at the axle.
If the cassette moves in relation to the hub and spokes then the hub is damaged, if there is movement by the frame then the hub bearings need adjusting.

[Mark Turner]

Thanks for the posts.

I'm going to put it down to my pedalling action as it stops when I stop pedalling. I really think I'm trying to get as much power on as possible and am being to vigorous on the down stroke rather than trying to get a smooth action going.

I'll post again if anything goes astray or I discover it's something else.

Cheers

Mark