Crankset replacement for older bike
Hi, I have a 1996 or maybe older Specialized Hardrock that I need a new crankset for. I plan on heading over to the thrift store to see if there are any bikes I can cannabalize parts off of and I'm wondering what I should look for in terms of suitability. Here are the components:
Crankset: Sakae XR100 [this is a triple, square taper (48, 38, 28), it says 'Powerflo Front' (PFF) on the chainring and there is a '170' imprinted on the crankarm.
Front Derailleur: Shimano FD-TY30
Rear Derailleur: Shimano RD-TY30
Shifters: New upgraded Shimano's
Please let me know if I have forgotten anything, thanks. -Ian
First, why do you need a new crankset? Are the chainrings worn/damaged, or do you need a new BB? If the chainrings are worn, you may also need new rear gears (not sure if yours has a freehub or freewheel rear wheel) and a new chain. Worn gears will cause annoying slippage and a worn chain will accelerate the wear of the gears, so spending $10 or so on a new chain is a good idea.
The key thing is to measure the width (side to side) of the cylindrical shell that contains your bottom bracket. Common widths are 73mm and 68mm. Normally, the choice of BB is determined by the choice of cranks; besides the mounting width mentioned previously, you'll need a BB with the correct spindle length (typically something like 113mm) for your cranks, so that the cranks are positioned at the correct distance away from the frame. Check out the recent thread here on the guy building a city bike from an older Specialized mountain bike frame for some useful info (and links to a decent quality but inexpensive new crankset and BB).
The "170" refers to the crankarm length in mm; 175mm is more typical for an adult bike, but if 170mm is working fine for you, don't worry about it.
I need a crankset because the chainrings are bent. The spindle on my BB wiggles a little but I'm hoping that's an easy fix with some new bearings. I have a 'SunRace M42 13-34 7-speed freewheel' which is a unique freewheel that uses a lockring. I'm assuming that the teeth on a freewheel wear by an increase of space between them but mine probably look something like this: http://i236.photobucket.com/albums/f...3/PICT8045.jpg It's been awhile since I've tested how well the gears shift and I'll have to wait to do that because my bike is in pieces right now.
I'll be sure to keep crank arm and frame clearance in mind and I'll also check out that thread. Do you have any advice in terms of derailleur and chainring compatibility?
The derailleurs are Shimano's lowest-end models (I think), but if they work fine, that's great. I'm not sure what you mean about der. and chainring compatibility. I'd be worried about that wobble in your BB, but a new cartridge BB should only cost $10-20. Measure your current chainline distance (see link to Sheldon Brown's chainline info page; it's the distance from the center of your BB shell to the center of the middle crank ring. Whatever replacement crankset/BB combo you get should duplicate that distance.
Here's a crankset that should actually be slightly better quality than what you've got:
Shimano M191 for $24 before shipping; it looks like it requires a 122mm spindle-length BB (verify this before buying a BB)
Assuming your frame has a 68mm BB shell width, here's a Shimano BB for $11 before shipping that will fit the above crankset:
There's nothing unique about that freewheel. You take it off the hub with a park FR1 freewheel remover. If you have reason to want to fiddle with the cogs themselves, you undo the lockring. This is how every freewheel in current production works, from cheap garbage to fancy stuff, though the tools needed can vary. Nobody has made a freewheel that has cogs screw on for years.
Originally Posted by applebuilder
Mondoman, thank you for all the information. I will review everything you said and take it into consideration when selecting a new crankset. As far as the derailleur-chainwheel compatibility, I was under the impression that distances between chainwheels and the number of teeth determined derailleurs you could or could not use. I guess this is not an issue? I'll do some more research.
dscheidt, it was awhile ago but when I researched that particular freewheel the overwhelming consensus was that lockrings were found on freehubs, not freewheels. I am no bike expert so I could have misunderstood something but on many threads both professional and non-professional mechanics repeatedly gave the advice that you should check for a lockring to determine whether you had a freewheel or freehub. Maybe you thought I was using the term 'freewheel' to refer to freewheels and freehubs in general.
dscheidt, after brushing up on the subject I do have to assume you were under the impression I was using the term 'freewheel' in a general sense. I think most mechanics here will agree with me that 'freewheels' are the older systems that thread onto the bike while 'freehub' is used to refer to the newer cassette types. Most people will also tell you that you will not find a lockring on a 'freewheel' because while one is used to secure a 'freehub' to a wheel, 'freewheels' are threaded on so there is no need for one. That is why this particular unit is unique because it uses a lockring to secure the cogs to the racheting body but it is in fact a thread-on freewheel from an older bike. Hope this clears things up for you
Is this a crank with removable chainrings? If so, they can be replaced. Sugino replacement rings are readily available, and should fit your crank. If the spider arms are bent, then you need a new crank, either a replacement right hand crank, or a new crankset. Again Sugino makes one of the best.
DRF aka Thrifty Bill
I think you are on the right track as to finding a donor bike. I rarely if ever buy new parts for older MTBs. I find donors frequently. Better cranksets will have chainrings that are bolted on, not the cheap riveted on rings. Also hit garage sales, I see quite a few MTBs at garage sales. I finished my wife's MTB with a $5 donor from Goodwill: crankset, rear derailleur, wheels, freewheel, etc., all came from that $5 donor.
Originally Posted by applebuilder
Note freewheel. Note lockring.
A freewheel uses threads to attach the freewheel body to the hub, while cassettes use a lockring to attach the cassette body to the freehub body. None of this precludes a freewheel using a lockring to attach the cogs to the outer freewheel body, which yours, and several others, do. And you will also almost always find a lockring attaching the outer freewheel body to the inner freewheel body. If you expect a freewheel to have no lockrings, I don't think you could ever find a freewheel.
Last edited by Nerull; 10-04-10 at 04:05 PM.
thanks for the tips, unfortunaely the chainring is part of the crank arm. Went to a thrift store today but got nothing. There's a Goodwill close to home so I'll have to try that plus the garage sales. If all else fails I'll keep the Sugino cranks in mind.