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Someone has just given me a free mountain bike (No obvious branding on it, but its got a 21-speed Shimano gear system and a shock absorber between the front and back of the bike in the middle of the chassis). It's been sitting in a shed, un-touched for about 2-3 years.

It's clearly in need of a service (lubricating, replacing the brake cables as their ends are frayed). But is there anything in particular that I should look for which would indicate that it's not worth repairing and that I should give it to someone else for parts?

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BTW, frayed ends on the brake cables isn't really a problem. It just means that someone failed to install the little cable end crimp-on things when they installed the cables. Messy, but it does not indicate a problem with the cables themselves. – Daniel R Hicks Apr 10 '12 at 1:22
I think the answer would depend mostly if you are a mechanically oriented person or not. Taking the case of this bike as an exercise to learn about bikes is surely worth the challenge, but might not worth the trouble otherwise. – heltonbiker Apr 10 '12 at 1:31
Forgetting to say thank you? – zenbike Apr 10 '12 at 5:07
up vote 10 down vote accepted

It's probably worth riding, if you don't have another bike.

First, of course, simply wipe off the dust (or hose it down and wipe dry). Then examine for bad rust. If it's an inexpensive bike that was stored where it wasn't completely dry there's apt to be some rust spots here and there, which is OK. But gobs of rust around the bearings is a bad sign. If the chain is badly rusted that's not fatal, but not a great sign.

Air up the tires. (Once you decide you'll be a bike rider you'll want to get a bike pump of the full-sized "floor" variety.) Then pick up the bike and spin each tire -- they should spin freely, with no gritty feel in the bearings. Note that the brakes may drag, but that's not a serious problem.

Pick up the rear wheel (or hang the whole thing from ropes or some such) and then turn the pedals with your hand. The chain will likely clatter quite a bit, but by adjusting the shifters (and maybe "helping" the chain with your hand a bit) you should be able to get squarely onto gears front and rear and then turn the crank at a fair pace. There may still be clatter, but you shouldn't feel a gritty feeling in the bearings of the crank. (Note that if the chain is badly rusted with "frozen links" you won't be able to get beyond this point.)

Next, try the brakes. If the bike has been exposed to the weather the brake cables are apt to be badly rusted, but that not a big ticket item. But for a test ride you want at least one working brake.

If you get this far, try to adjust the seat to about your height (this may require an Allen wrench of the appropriate metric size, or a regular adjustable wrench for a bolt head). (Keep in mind that if anything on the bike is rusted it's apt to be the seat height adjustment, though.)

But if you can get the seat semi-adjusted, get on the bike and try riding a short distance. If you're brave you can try the shifters, but you're more feeling for a grinding feeling anywhere, in the pedals, wheels, or steering. And somewhere along the way examine the condition of the tires, looking in particular for cracks in the sidewalls.

At this point you may have no problems at all with the bike, in which case you can just ride it, though you should probably take it to a shop to be tuned up within a few weeks (or buy a good book on the topic and do it yourself).

Or you may have found something (rusted brake cables, bad shifting, rotten tires, etc) that isn't "fatal" but demands more immediate service. Almost certainly worth paying a shop to fix.

Or you may have found crunchy bearings, severe overall rust, or some other problem that makes the bike at best a "fixer upper". Only spend money on this one if you've got a "thing" for "lonely" machines.

One thing to note: If you decide, for whatever reason, that the bike is not for you, ask around for an organization that "recycles" them. In our area Christmas Anonymous and the Kiwanis Club will take bikes in any condition to be rehabbed for kids and needy adults. Bikes that are in too bad of shape to be rehabbed are stripped for spare parts and the rest is recycled.

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Wow, that's a very comprehensive checklist - thanks! This is going to be a great help. – Mark Henderson Apr 10 '12 at 1:45
+1 for the recycling tip. – Jahaziel Apr 10 '12 at 17:48
The only thing I would really add to this list is check the wheels for a serious 'wobble' and/or rubbing against the brakes unevenly. You can true a wheel most of the time, but if you don't have the tools and know how it can cost a bit of cash. – Benzo Apr 13 '12 at 20:14
A freebie bike is a good place to learn how to true wheels. – Daniel R Hicks Apr 14 '12 at 9:42

Depends on what you want to use it for and how much you like working on bikes yourself.

No obvious branding may or may not be a problem - you might have a POS made with cheap, heavy steel and knock-off components, or a perfectly good name-brand bike with good components. If you're not sure of the difference, you should ask a bike shop or someone who knows bikes.

In my experience, a good quality bike is pretty robust: my two bikes are 20 and 25 years old and are going strong and have never needed more than minimal maintenance. I've got a couple other bikes that are the same age that I'll get around to fixing up some day and I don't expect any problems with them.

OTOH, a cheap POS bike is often a pain to maintain - there are usually lots of rusty "stainless" fasteners, everything's sloppier, etc. If the bike's in decent shape, it could still be ok, but long-term use is more of a problem.

Either way, the things to look at are:

First - frame damage: are there dents, rust or buckled tubes? If the bike has had a head-on collision, you may see a frame buckle near the head tube. Is the derailleur straight or is it or the hanger bent?

Next, is the bike is in good riding condition? Is the drivetrain is smooth, do the gears shift crisply, is the braking smooth and effective? Look at the cogs and chainrings for worn (pointed) teeth, look at the braking surface on the rims: do they look worn?

If the bike is mostly ok, lube it up and change the cables (or get a shop to do it), but if it is just a cheap "department store" bike, I wouldn't plan on doing much more than that. If it's a decent bike with good components and it's working well now, I'd expect it to give you many years of good service.

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Check the most expensive parts first.Inspect the frame for cracks at all the weld points.Check the shock,sit on the bike and bounce on the seat.Does the shock compress and then rebound smoothly?Does the swing arm pivot smoothly with out binding?Squeeze the front brake and compress the fork.Again does it compress smoothly and rebound evenly?Unless it is a highend bike any of these repairs could cost more than the bike is worth.If you feel you can do it safely take it for a short slowspeed ride.Note any issues with shifting,stopping,wheels being true and spinning freely.A handful of inexpensive issues can cost as much as a single large repair.

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The thing I would try to avoid with a 'free' bike would be getting too involved with it, depending on the starting quality. I can only speak for myself, but given a project I tend to go overboard with ordering parts, upgrading broken/missing components, and otherwise sinking a lot of money into something that wasn't worth it in the first place, like a Next / Walmart bike.

I'd assess realistically what you want to do with it and how much you're actually going to ride it, etc. Tune up issues and the things most people have mentioned here are cheap fixes and in general worth doing if you're going to ride it at all. I'd stop before it gets to replacing forks / wheels / drivetrain, etc.

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