Mystery Whirring - drum brake?

[dstke]

My wife and I have had our Co-Motion Speedster with Arai drum brake for two years and love it however after warming up for a few miles and when beginning a climb, i.e., putting more torque and pressure on the pedals, we start getting a strange whirring sound from the back hub.

We've taken it into the bike shop several times but they've never been able to duplicate the sound. We're not sure if the sound is coming from the hub, cluster, or drum brake.

We don't get the sound when we're cruising along in the flats and mostly it occurs only when climbing and putting more pressure on the pedals. The sound is definitely not coming from the pedals or the crank, either one of us can create the sound with the other pedaling lightly. The sound is not continuous but occurs at the same place in the pedal cycle - usually where the most pressure/torque is applied.

My wife says it sounds like creaky bedsprings :)

Any ideas?

[bikeriderdave]

I was once involved in the diagnosis of such a sound. In that case, it turned out to be the rear hub. It's likely that the shop is unable to find the noise because they are simply putting your bike up on a repair stand or riding it once or twice around the parking lot. Can you stop at the shop after getting the noise to start and drag a mechanic out as a guest-stoker? If not... Since you suspect the drum brake, why don't you remove the brake and take a ride long enough to reveal whether the sound is gone? If it's still there, borrow any wheel that will fit your bike and duplicate the ride. When the sound goes away, you will have narrowed the range of possible causes and be better able to decide what to adjust, lube, or replace.

Good luck,

Dave

[dstke]

Dave,

Thanks for the suggestions. I tried removing the outer plate on the drum brake on our ride yesterday but I didn't have a spacer to place on the axle to make up for the missing cover - I'll try and find something this week. I, too, am suspicious that the problem may be in the hub and not the drum brake. The shop we take it to actually has taken it out on extended rides and tried to crank it into making the noise but to no avail, I rode with the shop guy for 30 minutes once and still couldn't get it started - part of the mystery I guess.

/Doug

[TandemGeek]

What brand / model hub are you using?

Has the shop checked the axle to make sure it's not bent?

[dstke]

It's a DT Hugi hub, not sure what model. According to the Co-Motion website, they use DT Hugi Symmetric 36h, 40h or 48h. When we first took the bike in last year they overhauled the hub but I don't know the degree or details of what that entailed.

[TandemGeek]

It's a DT Hugi hub, not sure what model.

As you can imagine, given the trouble your LBS has had pinning down the problem, doing so via morse-code is likely to be equally fruitless. Therefore, because it's a Co-Motion and the OEM hub let me suggest that you give the folks at Co-Motion a call to see if they may have encountered the same symptoms with other customers and if they know the root cause.

I have a few ideas but Co-Motion would be in a better position to offer a solution that would be more likely to solve the problem on the first try vs. the three or four things I'd suggest as a way of isolating the problem.


http://www.co-motion.com/graphics/tolfree.gif

[dstke]

I talked to Co-Motion last Fall and they hadn't heard of any other reports of similar problems. They suggested that it might have something to do with the alignment of the drum brake and cover plate. Working with my LBS we tried adding a small spacer to the drum brake but it didn't make a difference. I've been reviewing info on the Hugi website, plus I emailed them, and I'm thinking that it might be best to try another hub overhaul.

[TandemGeek]

I've been reviewing info on the Hugi website, plus I emailed them, and I'm thinking that it might be best to try another hub overhaul.

Have you ridden the bike without the drum to see if that eliminates the problem...?? or was that what you were trying to do with the LBS when you struck out on the correct spacer to allow for the removal of the disc?

That would be the first, most obvious and easiest step relative to isolating the noise.

[Xanti Andia]

I would not discard the pedals as a source of the noise either, and switching pedals around is easy enough.

[Michel Gagnon]

You can test the drum brake fairly easily. Remove the cable, attach it safely somewhere and push back the activating arm, so the pads will clear the drum even more than they do when the cable is attached.
If yours is a problem with the drum brake, the noise should be over... or at least much more subdued.

[la2sei]

i was wondering if it might be from the saddle clamp or seat post if it's a creaking noise. since it seems to happen in time with your pedaling motion.

[Michel Gagnon]

Oh! I missed that part of the problem. Brooks saddles (if you have them) are good creakers.

Once, I also had a "drivetrain" noise, which I was able to identify as a handlebar noise. And I thought it was linked to the headset, until I realised that one brake lever was a bit too tight and creaked.

[dstke]

Thanks everyone for your suggestions. Given how long we've had the problem we eliminated shoes, pedals, cranks, and seats from the equation.

I sent an email to Hugi DT Hubs tech support and received an email on how to clean and re-grease the rachets in the hub, which I did. We went for a 60 mile ride on Saturday with about 3500 ft of climbing and didn't hear the sound so we're hoping that fixed it.

Thanks again for all your input.

/Doug