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Bike Problems...

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Old 01-01-05, 04:11 AM
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DHMudRunner
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Bike Problems...

Hey Everyone. I have an Iron Horse AT100 from I'm guessing the 80's (if that matters) and I am having a serious problem. When I pedal the bike sometimes it will work fine and other times it will make a grinding noise and then a crack from the crankset between the pedals. Is this a sign of an extreme problem or should I just get everything re-lubed? I bought the bike about a year ago from someone who used it for a mail route and I now use it on downhill runs. I'm not sure if the previous owner did any service on it but I haven't. Is it possible that I may have to replace the whole crankset?
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Old 01-01-05, 06:39 AM
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sounds to me like a new bottom bracket may be needed- you probably dont need to replace the whole crankset. You might have to change the chainwheels if they are worn- check for wear by looking at the teeth on the chainwheels. Some chainwheels do not detach from the cranks and in this case and in the event that they are badly worn you would need to change the whole crankset. You could also check the cassette/freewheel and measure the chain for wear (see http://www.sheldonbrown.com/chains.html for further details). If the bike has been in regular use since the 80s then it seems likely that a whole new drive train (chain, chain wheels and cassette/freewheel) will be needed soon.

If you find that the BB is the problem then you need to overhaul it. If it is a cartridge type then just take the BB out and take it down to the LBS and get a new one. If it is the ball bearing type then try new ball bearings and grease (see http://www.utahmountainbiking.com/fix/bracket.htm). The Sheldon Brown site and Park tools also have some info on BB servicing I think. Good luck.
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Old 01-01-05, 11:43 AM
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While you have the arms off for the BB service, inspect the tapered portion of the arm where it joins to the axle. If when you take the arms off, the bolts are loose, look very closely. If there are any more edges in there than the 4 that are supposed to be, youve found a prime suspect of the noise. The bad news is the arm is pretty well shot if that happens.
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Old 01-01-05, 03:32 PM
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Thanks. Sorry if this seems stupid but all I really do is ride the bikes and do some repairs.. so, what exactly is the bottom bracket?
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Old 01-01-05, 03:40 PM
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the bottom bracket is the bearing shaft that fits inside the frame and on which the crankarm with the pedals are mounted. It usually has square taper projections on which the crank arms are press fitted.

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Old 01-01-05, 03:57 PM
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Ok, Thanks. Hopefully I can get that fixed and use my Iron Horse and I can quit using my Mongoose for downhill and freeride.
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Old 01-01-05, 04:48 PM
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Your question is why most of the time in my shop we just call them crank bearings/spindles or something to that effect. Its not as technical but the customers aren't confused. I think technically the Bottom Bracket is actually supposed to be a frame referrence not actually the part, but convention took over.
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Old 01-01-05, 04:59 PM
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If the bikes that old, it probably has a loose ball bb.
It WAS a repairable system, but if it's been run with worn ball bearings or without lube the races (channels the balls roll in) get pitted.
Then its garbage.

I recently had a cartridge bb installed...$22? and $17 labour.

The cartridge bb require no lube, they are just replaced. 5 year life span probably.
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Old 01-01-05, 05:02 PM
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Probably already been mentioned, but it takes a special tool to remove the bottom bracket. It usually should only set you back about $30-35 for the LBS to fix. Some will be higher some may be less.... All depends on your locale.
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Old 01-01-05, 05:04 PM
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Oh my, $17 in labor for that? Man, thats a killing on thier part.
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Old 01-01-05, 05:32 PM
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Originally Posted by mtbikerinpa
Oh my, $17 in labor for that? Man, thats a killing on thier part.
And you're an "Aviation Mechanic"? Surely you can afford this fee for about 30 mins. of their skill fixing your bike.... Maybe that's what you want to be someday.
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Old 01-01-05, 05:37 PM
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My bikes see a mechanic other than myself about 3 times in thier entire service life.

On a side note, while the Hangar gets a typical labor rate of $60+/hr, the avg wrench such as myself sees far less than that, hardly $13/hr for the first 6-months.
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Old 01-01-05, 06:08 PM
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I think she was implying that $17 is steep for such a repair. I'm pretty sure my LBS charges $20-25/hr for labor, though I'm not 100% on that one.
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Old 01-01-05, 07:51 PM
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Originally Posted by mtbikerinpa
Oh my, $17 in labor for that? Man, thats a killing on thier part.
Taper bb and I don't have a puller. My mech also pulled my rear rear hub inspected the bearings and lubed.

Deal.
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Old 01-02-05, 03:07 AM
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$17 isn't bad for that, then.
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