Bicycle Mechanics - Repair crank on cheap bike
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12-12-01, 11:44 AM
Took my Nishiki Sport(spent the least money on my hybrid, of my 4 bikes.) Took to my favorite bike shop. They told me crank is a 'unified,' crank; can't change out chain rings. Shimano 100 GS. Crank is aluminum and teeth are worn. Need to change chain. Bike costs about $450 new in about 1994. Crank costs over $100. Is it worth the repair.? Do I have to pay that much for a new crank.? Any suggestions?
I believe the GS 100 is no longer made; An "Alivio" FC-MC20 triple 22/32/42 shouldn't cost more than $50.00.
A "Sora" FC3303 triple Road crank 30/42/52 shouldn't be over $70.00.
These are Shimano cranks. Don't forget to add labor to these prices.
Whether it is worth the repair depends on how much you like this bike. Is it your favorite, or does it sit around most of the time? You have to make that decision.
12-12-01, 01:08 PM
Check out eBay for some deals. You can get "new" or barely used premium cranks for about $50-75. I would suggest getting a new bottom brackett as well (due to the age of your bike). If you're replacing the cranks, it would be safe to bet you need a whole new drivetrain as well. (cranks, cassette, chain), this can get expensive all at once, but will probably be the case! Cranks @ $50, bottom brackett @$25, new chain @ $18, new cassette @ $30. adds up to about $123.00 seems like a lot, but cheap considering how much maintenance on a car would cost.
To keep things simple, get some new cranks with the same size (#) chainrings. A 42/32/22 is pretty standard, but there are many variations, so count yours and buy the same!
Of course, you'll have to do the work yourself or pay someone to do it for you. Maybe a cycling friend would do it for a 6-pack and teach you at the same time!
Also, you'll need a couple of special tools to do this including a crank puller, bottom brackett tool and a chain breaker! This is where the friend with tools comes in handy!
Yeah, I know you're not made of money. Me either! I just buy tools as I need them, and learned as I went. Pretty soon, I had a full set of tools and a lot of friends needing help with their repairs. Read, ......a lot of free beer, and good times that go along with the sharing of those beers!
Good luck and if you go the "do it yerself" route let us know and we'll help out any way we can!
12-12-01, 02:10 PM
By "unified" does that mean the chainrings are riveted on? But the crank arms are removable? I recently got a lightly used Shimano 48-38-28 crankset on ebay for $25. As long as the bb has square taper spindle you don't need to replace it unless it is shot. Definitely overhaul it now since you have to remove the crank arms anyway. I addition to the crank puller and crank bolt wrench (I got both in one from I believe Nashbar for either $12 or $15. Lifu brand. Works great.), you will need a bb hook spanner to remove the bb lockring. Spend a few bucks to get the Park with three "teeth" to engage the notches.
I assume the bike has 7 or fewer cogs in back. As long as that is the case, you don't really need to change anything but the crank.
Come to think of it, I have a similar crank, 170 mm, 48-38-28, low end Suntour if I remember correctly, that I took off my hybrid after just a few hundred miles. You can have it if you want it. Just send me an email where to send it. But you'll have to get your own tools and book on how to change it. :D
that's one of the problems with cheap bikes. You could drill the rivets out, get new rings, and hammer new rivets in,but that's about all you can do with that kind of crank.
I am pretty sure you need a new bottom bracket as well, because most cheapo cranksets used a different taper size, with a fixing nut instead of a fixing bolt on the end. You will not be able to secure a modern crank onto a spindle of this type. Fortunately, your BB shell is British-ISO standard, so parts should be readily available. I have picked up three nice cranksets on eBay, including an almost-new Campy Veloce for $35.
I think it is worth spending $100 fixing up the bike -- look at the junk you get for less than $300 when buying new!
12-14-01, 03:10 AM
You can use the same BB spindle if the crank arms have the same offset or "Q" factor, the tapers are probably the same and can be easily checked to make sure. No worrys if the crank you get uses a bolt vs a nut to hold it on the spindle, I've switched hundreds of spindles going from nut to bolt type or vice versa. Very often a different length spindle is required when replacing crankarms.
Ride good crank
12-14-01, 08:34 AM
Thanks Rainman, John, et al. Stopped at LBS. The mechanic had the 'Alivio' in stock. The chainring's teeth are worn. So Changing chain is not recommended. Would change cassette and chainrings for under $100.
Guess, I am happy. Mechanic did not mention problem with bottom bracket. Had not yet the benefit of all your responses. Will repair the bike in Jan. after shop is less busy.
I am definitely a roadie. Been riding my hybrid for last two days. Is a very solid bike overall. Good for ocassional off road triip. has rack and trunk bag and grocery pannier on it, so also good for my wife. So will repair it. About $100, worth it for a $400 plus bike. Thanks all.
12-14-01, 01:03 PM
Since the crank was Shimano only 7 yrs old I kind of figured it was a standard square taper crank. $400 was not a "cheap" bike in 1994, and Nishiki is a decent brand. Have you ever overhauled the bottom bracket? If not, it is long overdue. Overhaul (clean or replace and repack bearings with grease) is recommended every 3,000-4,000 for a road bike ridden only in clean, dry conditions, more often the dirtier the riding. Even if you haven't ridden the bike that many miles, grease breaks down after a few years. Bearings are cheap ($3.00 or so for the 20 usually required) so it's a good idea to go ahead and replace at each overhaul. Might as well get the shop to do it while you have it in for the crank. They probably don't charge much. Actually, replacing the bb with a cartridge bearing Shimano UN52 or UN72 might not cost much more than the overhaul. They are very inexpensive, about $20, and you just replace when they begin to act up.
And while we're on the subject, hub and headset bearings need the same type of overhaul on a regular basis.
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