Tandem Cycling - Scraping noise under load
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04-09-08, 09:22 AM
Here's one for the peanut gallery. Over the winter I put new wheels on the Sleek Black Beauty - our 2000-ish Arriva Stowaway. The original EDCO rear hub had failed after about 5000 miles and I ended up with Santana OEM Shimano 48 spoke hubs with Dyad rims and reused the original 8 sp. casette. We have an Arai drum and I had to also buy a new brake shoe mounting plate because the EDCO axle was 12mm diameter and the Shimano is 10.
Everything works well until we stand on the pedals and then we get a scraping noise that sounds suspicously like the plate is rubbing against the drum. I've pulled everything apart but can find no telltale scrap marks around the perimeter of the plate and there appears to be about a mm of clearance all around. Has anyone ever run into this? I could be all wet and am looking in the wrong place for the noise. When pedalling with even moderately high pedal pressure the bike is silent.
04-09-08, 10:33 AM
Can you test the disc brake theory by riding without the caliper or the rotor to confirm that you do not get the noise without the rim-caliper interface? Of course don't try this on a big downhill :).
04-09-08, 10:37 AM
Why would going into a stance affect the way the brakes are setup? If it is grinding, then the bike should seem noticeably slower. I am no expert on disc brakes at all, but it just seems from the design that it would be hard to affect the caliper just from standing.
04-09-08, 10:58 AM
Why would going into a stance affect the way the brakes are setup? .
The first reply inadvertently took you down a dirt road. An Arai drum is, in fact, a mechanical drum brake, not a disc brake. The drum threads onto the hub body and the backing plate with its reaction arm, actuating mechanism, and shoes is bolted to the hub's rear axle. The drum and backing plate are concentric units that work in the same manner as a drum brake on an automobile, truck, motorcycle, etc... Therefore, the drum and backing plate can, in fact, experience interference issues if the hub body and axle or any of their concentric parts falls out of concentric alignment.
To the OP, what you're describing sounds like what may be a little bit of axle / bearing deflection under high-torque if it is, in fact, coming from the Arai drum. If you're not positive that the drum brake is the source, then something along the lines of what masiman suggets (i.e., removal of the rotor), such as removing the backing plate for a test ride, would allow you to isolate the brake to confirm the noise is not coming from some other part of the rear wheel.
If it is the brake, while I'm not exactly sure what may be rubbing, rest assured that it will reveal itself before too long vis-a-vis some paint removal on the inside of the drum or backing plate, or perhaps around the perimeter. Unfortunately, while I've fiddled around with the Arai drums, I've never had one on our own tandems so I'm at a loss to suggest anything beyond waiting until such time as you're able to determine where the interference is occuring. That is, unless this is a common occurance that someone else on the list has experienced and who will be able to offer some direct and responsive advise.
As always, one of your regional / local Santana dealers (e.g., Rich at gtgtandems.com) may be able to offer some advise.
04-09-08, 11:58 AM
Ya, sorry I skimmed the OP and saw "scraping on plate", and so on. The rest is history :). My apologies for not focusing on what you clearly stated and traversing my own path.
On the bright side, the idea of removing the potential source from the equation is still relevant :)!
I hope you find a problem with an inexpensive fix.
04-09-08, 12:54 PM
Thanks folks. Good idea on removing the shoe mounting plate and taking it for a spin up a hill
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