Weird noise question

[Chill]

I carried out routine maintenance on my GN250 the other day - a bike I've had for three years, 18,000 km on the clock. Checked oil, cleaned, tightened chain etc.
Riding it the next day I noticed a noise which seemed to be coming from around the back wheel - a kind of brushing noise which seemed to occur every revolution of the wheel - the noise came at less regular intervals when I slowed down. It sounds really like the chu-chu of a steam train actually.

I checked, and there was no object brushing the wheel. I thought maybe when I'd tightened the chain I hadn't got the rear wheel in line properly, so I re-did it carefully and the noise has Possibly decreased but is still noticeable.

Any help appreciated.

[vifferman]

Brake pads dragging slightly? It's either that or the tyre rubbing the chainguard.

[xwhatsit]

Brake pads dragging slightly? It's either that or the tyre rubbing the chainguard.

Drum.

You didn't over-tighten the chain?

[fatzx10r]

possibly a tight spot in your chain, once you tighten your chain it could be straining it?

[Chill]

Overtightening might be it - so a slight loosening would fix that - no brake adjusting?

[xwhatsit]

Overtightening might be it - so a slight loosening would fix that - no brake adjusting?

Yep -- no need for brake adjusting -- GN250s have nice sensible drum brake on the rear, so you won't get pads brushing the disc or any other myriad issues with disc brakes. As long as there's still a bit of free play when you press the pedal, then there's no need to adjust (unless too much free play of course).

Is there the correct amount of tension? About 2.5cm of movement would be good; measured at the tightest spot in the chain. If the chain has tight spots, and if you measured play at point where the chain is loose, then it could be tightening up at the tight spots, not good for the gearbox output shaft bearings.

[vifferman]

Drum.

Yeah, I knew that. I just (momentarily) forgot they're called shoes, not pads.

[vifferman]

GN250s have nice sensible drum brake on the rear.

Sensible?
Is fade sensible?
Build-up of dust inside the drum - that must be sensible, right?
How about... having to find someone who'll machine the drum, or buy a whole new wheel when it's worn - that's sensible, right?
Oh - the ineffectiveness - that's sensibly safe, eh? As is the propensity for things to jam, huh?


My first three bikes had drum brakes, as did my first car. I don't miss them at all, nor do I look back with fond remembrance as to how "sensible" they were.

You're such a Luddite, Mr Xerxesdaphat.

... not good for the gearbox output shaft bearings

Nor is it good for the interference it causes with swingarm movement and gearchanges.

[sinfull]

3 yr old gn ! Are they sealed bearings in the back hub ?

[xwhatsit]

Yeah, I knew that. I just (momentarily) forgot they're called shoes, not pads.

Nevertheless, being a drum brake, the shoes won't brush the drum unless the pedal is overtightened. Also, because there's only a few mm difference between brushing and on, there will likely be massive rear wheel drag. Certainly noticeable when lubing your chain. Drums don't really seem to make any noise, either, unless they're wet, so that doesn't sound likely.

/offtopic:
Ineffectiveness? When you're talking about CB250RS front disc brake, a drum brake is infinitely preferable

Drum brakes are particularly sensible on the rear wheel. Low maintenance (no bleeding fluid/seals/shoes last forever), massive power is not needed, feel is much more important (where drums excel).

Maybe things are different on the latest VFRRRRR über-cycle, but on the sort of machines that carry me around, a rear disc is a liability (cf. the RD250LC I've pinched for the moment).

[MSTRS:Me]

Pulling the wheel back to tighten the chain...yep...did you loosen off the adjuster on the drum brake rod to compensate? One of the (many) disadvantages of drum brakes.

[rainman]

My money's on the chain. How long since you changed it?

Rotate the wheel and test the amount of slack in the chain (so, test it at different points). Betcha it's tight in some spots, and looser in others.

Yes=Get a new one. And you should change the sprockets at the same time....

[Taz]

The trick with drum brakes is to hold the brake on when tightening the axle to ensure the brake plate is centralised to the drum.

[CB ARGH]

There are different parts on a chain that are usually tighter than the other. When tightening or loosening a chain, make sure that you turn the wheel and check each part of the chain for tightness/looseness, as one part may be SUPER tight, where as another part may be SUPER LOOSE - If this is the case, get a new chain.... punk