Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Reply
 
Thread Tools Search this Thread
Old 04-06-13, 10:54 AM   #1
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,620
Buying a crankset

I need a crankset for my beater bike. It is a low end Trek 820. It is a 7 speed. I don't want to sink a lot of money into it. My question is, will this:

http://www.bikepartsusa.com/bikepart...rank-crank_mtn

Be a good replacement for this:

?

The worn out crank has 28/38/48 chainrings and 175mm cranks. It is riveted together. The problem with the new one is there is no information. I don't know the ring or crank sizes. But as long as they would work it really doesn't matter. I think a 170mm crank would work.

OR

Could someone suggest a crankset that is a little better? The next best one I could find is about $60. I would get that if I had to, but if the $16 one would work I'll go with it.

Thanks in advance.
Attached Images
File Type: jpg IMG_0321 (1024x768) (640x480).jpg (46.1 KB, 35 views)
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.

Last edited by sknhgy; 04-06-13 at 10:57 AM.
sknhgy is offline   Reply With Quote
Old 04-06-13, 11:08 AM   #2
Continuity
Senior Member
 
Join Date: Mar 2013
Location: NW UK
Bikes: 1992 Marin Eldridge Grade, 2007 Kona PHD and 199? Trek 1000 (current build project)
Posts: 418
I think those Pyramid ones are 42/34/28 if it's the on I think it is from this page. If it's the other one, then it's 48/38/28.

A cheap'n'cheerful Shimano Tourney triple like the one below you can get for around $30 US.

Attached Images
File Type: jpg crankset fc-m171 front large.jpg (38.3 KB, 8 views)
Continuity is offline   Reply With Quote
Old 04-06-13, 11:31 AM   #3
Bill Kapaun
Senior Member
 
Bill Kapaun's Avatar
 
Join Date: Feb 2007
Location: Mid Willamette Valley, Orygun
Bikes: 86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
Posts: 9,159
You'll probably have to change the BB too. it seems the newer cranks use shorter spindles than the older ones.

Are you really sure your crank is worn out? Compare the teeth to a new crank before you condemn it. Not all teeth have the same profile. Some are different to assist shifting.
Bill Kapaun is offline   Reply With Quote
Old 04-06-13, 11:37 AM   #4
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 18,087
Quote:
You'll probably have to change the BB too. it seems the newer cranks use shorter spindles than the older ones.
... or at least be aware that when you buy a new crank, with replaceable chainrings, this time,
might as well get the BB,too, length, as recommended be used with that particular Crank-set..
fietsbob is offline   Reply With Quote
Old 04-06-13, 11:41 AM   #5
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,620
Quote:
Originally Posted by Continuity View Post
I think those Pyramid ones are 42/34/28 if it's the on I think it is from this page. If it's the other one, then it's 48/38/28.

A cheap'n'cheerful Shimano Tourney triple like the one below you can get for around $30 US.

Where would I get one of those Shimanos?

I'm pretty sure the middle ring is worn. I just replaced the chain, cassette, and RD, and now the chain jumps badly when I ride the middle ring - which is the one I use 99% of the time.
The bike is about 10 years old and has seen much use.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 04-06-13, 11:46 AM   #6
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 18,087
Distributors To bike Shops will have access them , check with your LBS ..
fietsbob is offline   Reply With Quote
Old 04-06-13, 11:56 AM   #7
Continuity
Senior Member
 
Join Date: Mar 2013
Location: NW UK
Bikes: 1992 Marin Eldridge Grade, 2007 Kona PHD and 199? Trek 1000 (current build project)
Posts: 418
You can get them on Amazon, Ebay quite easily and cheaply, too, but be warned that you're on your own fitting them, and will have to have the tools to do so (which are quite cheap and handy to have around if you own a bike or many).

For interest's sake, it would be good if you could post an image of your chainring(s), esp. the middle one.

New BBs can be had starting at around $10 or so for a basic square taper one, like a Shimano UN-26 - you have to ensure that you get the correct spindle length.

If y
Continuity is offline   Reply With Quote
Old 04-06-13, 03:07 PM   #8
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,620
Quote:
Originally Posted by Continuity View Post
You can get them on Amazon, Ebay quite easily and cheaply, too, but be warned that you're on your own fitting them, and will have to have the tools to do so (which are quite cheap and handy to have around if you own a bike or many).

For interest's sake, it would be good if you could post an image of your chainring(s), esp. the middle one.

New BBs can be had starting at around $10 or so for a basic square taper one, like a Shimano UN-26 - you have to ensure that you get the correct spindle length.

If y
My op has a pic.
I just want a crank to replace the worn original one. That is all. Thanks.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 04-06-13, 03:45 PM   #9
Continuity
Senior Member
 
Join Date: Mar 2013
Location: NW UK
Bikes: 1992 Marin Eldridge Grade, 2007 Kona PHD and 199? Trek 1000 (current build project)
Posts: 418
Quote:
Originally Posted by sknhgy View Post
My op has a pic. I just want a crank to replace the worn original one....
I meant a close-up of the teeth to see if they were so worn as to actually need replacing.
Continuity is offline   Reply With Quote
Old 04-06-13, 04:57 PM   #10
phulin
Senior Member
 
Join Date: Nov 2012
Location: Boston, MA
Bikes:
Posts: 108
Quote:
Originally Posted by sknhgy View Post
My op has a pic.
I just want a crank to replace the worn original one. That is all. Thanks.
The problem is that the BB and crankset need to "match" in terms of spindle length (at least to some degree). Otherwise, your crank may bottom out against the frame before it is tightened onto the square taper. If it's wrong to a smaller degree, your chainline will just be weird - forcing you to favor certain gear combinations over others.
phulin is offline   Reply With Quote
Old 04-06-13, 05:05 PM   #11
clasher 
Senior Member
 
clasher's Avatar
 
Join Date: May 2009
Location: Kitchener, ON
Bikes:
Posts: 1,858
Shimano alivio starts at 24 according to the website, and a new BB shouldn't be more than 20. I think that listing shows what length spindle to get too so you can measure your current one to see if it'll work or not... if it spins smooth I'd just leave it alone. Based only on that picture and the skipping you're experiencing it's almost certain that your rings are worn.
clasher is offline   Reply With Quote
Old 04-06-13, 11:54 PM   #12
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,620
I should be able to do this. I can measure the chainline and I have the tools to pull the cranks and to take out the bb. I dont do this everyday so I need to ask questions and look things up. If I take every little thing to the lbs I'll go broke.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 04-07-13, 12:54 AM   #13
pierce
S'Cruzer
 
pierce's Avatar
 
Join Date: Jun 2010
Location: 122W 37N
Bikes: too many
Posts: 2,294
I do prefer the UN55 BBs over the UN26s, they are smoother, and the metal lock ring always feels better when I torque it on (and it comes off cleanly without cracking). they are probably $5 or $10 more than the UN26's.

the tourney cranks are pretty heavy and kind of clunky, the alivio is a decent notch better. you gotta spend a chunk more to get anything much nicer (deore or whatever around $100).
pierce is offline   Reply With Quote
Old 04-07-13, 06:38 AM   #14
Continuity
Senior Member
 
Join Date: Mar 2013
Location: NW UK
Bikes: 1992 Marin Eldridge Grade, 2007 Kona PHD and 199? Trek 1000 (current build project)
Posts: 418
I've got a UN26 that I was thinking of using if it's the right length for some nice vintage White Industries cranks to put on my old Marin to replace the UN72(?) that's been on there since I got the bike in 1992 (!).

I've got a metal lockring to put in place of the plastic one on the UN26 - is that what you've had experience of cracking on them?

I also noticed that the UN26 seems to use cartridge bearings pressed into the ends of the metal shell, as opposed to the more 'all in one' look of other UNs I've seen.
Continuity is offline   Reply With Quote
Old 04-07-13, 06:53 AM   #15
BentLink
Senior Member
 
BentLink's Avatar
 
Join Date: Jan 2010
Location: Pennsyl-tuckey
Bikes: '86 Cannondale SR400, '86 Pugeot PX10, '92 Bianchi Axis, '95 Bianchi Campione d'Italia, '00 Fondriest X-Status, '08 Specialized Roubaix, '13 Cannondale CAADX
Posts: 684
How about just changing the worn middle ring?
You can find some at Niagara for example.
BentLink is offline   Reply With Quote
Old 04-07-13, 07:02 AM   #16
Continuity
Senior Member
 
Join Date: Mar 2013
Location: NW UK
Bikes: 1992 Marin Eldridge Grade, 2007 Kona PHD and 199? Trek 1000 (current build project)
Posts: 418
Quote:
Originally Posted by BentLink View Post
How about just changing the worn middle ring?
You can find some at Niagara for example.
Afraid not -

Quote:
Originally Posted by sknhgy View Post

The worn out crank has 28/38/48 chainrings and 175mm cranks. It is riveted together.
Continuity is offline   Reply With Quote
Old 04-07-13, 08:47 AM   #17
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,620
Will I notice much difference if I switch from a 175mm to 170mm crankarms?
Will there be much difference if I go with 22/32/42 teeth as opposed to the original 28/38/48?
I'm thinking this would be a good idea because I run skinny tires and the pedals are very close to the ground with the 175's.

Thanks everyone.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.

Last edited by sknhgy; 04-07-13 at 08:57 AM.
sknhgy is offline   Reply With Quote
Old 04-07-13, 08:48 AM   #18
Continuity
Senior Member
 
Join Date: Mar 2013
Location: NW UK
Bikes: 1992 Marin Eldridge Grade, 2007 Kona PHD and 199? Trek 1000 (current build project)
Posts: 418
It would help prevent pedal strike a *tiny* amount (5mm ), and lower your pedalling torque by an equally tiny amount - how tall are you?
Continuity is offline   Reply With Quote
Old 04-07-13, 08:59 AM   #19
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,620
Quote:
Originally Posted by Continuity View Post
It would help prevent pedal strike a *tiny* amount (5mm ), and lower your pedalling torque by an equally tiny amount - how tall are you?
I'm short and stocky and I put out a lot of torque.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 04-07-13, 09:11 AM   #20
Bill Kapaun
Senior Member
 
Bill Kapaun's Avatar
 
Join Date: Feb 2007
Location: Mid Willamette Valley, Orygun
Bikes: 86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
Posts: 9,159
IF you're short, you may be able to spin a lower gear faster, ending up with a higher speed overall.
I have a bad knee and going shorter made a remarkable difference for me. Don't forget to raise the seat 5mm.

I'd replace with the same tooth counts to avoid any FDER issues.
Bill Kapaun is offline   Reply With Quote
Old 04-07-13, 09:31 AM   #21
pierce
S'Cruzer
 
pierce's Avatar
 
Join Date: Jun 2010
Location: 122W 37N
Bikes: too many
Posts: 2,294
note that on a bicycle you don't WANT to 'put out a lot of torque', rather you want to spin faster in a lower gear. mashing hard on the pedals is a sure way to trash the bike *and* your knees in the long run.
pierce is offline   Reply With Quote
Old 04-07-13, 09:48 AM   #22
Continuity
Senior Member
 
Join Date: Mar 2013
Location: NW UK
Bikes: 1992 Marin Eldridge Grade, 2007 Kona PHD and 199? Trek 1000 (current build project)
Posts: 418
You may benefit from installing even shorter crankarms, maybe 165mm if you can find them, and learning to spin faster.
Continuity is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 06:31 AM.