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


Go Back   > >

Recreational Cyclocross and Gravelbiking This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-07-07, 05:20 PM   #1
ekimyel
Senior Member
Thread Starter
 
ekimyel's Avatar
 
Join Date: Mar 2006
Location: Western PA
Bikes:
Posts: 383
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
? about changing chainrings

I just ordered a Motobecan Fantom Cross Pro. It comes with a TruVativ GXP External Outboard crank with 48-38 chainrings. I would like to make it a compact 50-34. Can I just change the chainrings? It comes with a Shimano Ultegra 6600 front deraileur. Will I need to get a compact deraileur? I'm using this bike as my bad weather road bike more or less. Will use it on some rails to trails, and possibly a little bit of single track. I live in an extremely hilly area, and I have a compact on my road bike. I'd like to have the same gearing on this bike, but don't really want to buy an new compact crank unless I have to. Thanks for any advice....
ekimyel is offline   Reply With Quote
Old 07-09-07, 01:02 PM   #2
cachehiker
Soma Lover
 
Join Date: Dec 2004
Location: Logan, UT
Bikes: one bike for every day of the week
Posts: 765
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The 50-34 chainrings have a different bolt circle diameter than the 48-38 crankarms. IMHO, I think a mid-cage mountain rear derailleur and an 11-32 cassette would be cheaper and work better than a new crankset and bottom bracket. Shifting across span of 31 total teeth (50-34+27-12) with a road double rear derailleur generally works but it can be temperamental. The Shimano CYA maximum is only 29 teeth. I don't know how well a standard 20-speed front derailleur works with a compact crank but my 18-speed setup works just fine.
cachehiker is offline   Reply With Quote
Old 07-09-07, 01:21 PM   #3
ekimyel
Senior Member
Thread Starter
 
ekimyel's Avatar
 
Join Date: Mar 2006
Location: Western PA
Bikes:
Posts: 383
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Good suggestion, except I want to be able to swap these wheels over onto my road bike in case I have a problem with the wheels on that bike. Ahh, maybe I don't, I guess if i have a problem that bad, i can just swap the cassettes.

What derailleur \ cassette do you recommend? I don't have much experience at all with mountain bike components. Thanks for your help...
ekimyel is offline   Reply With Quote
Old 07-09-07, 01:29 PM   #4
bitterken
Senior Member
 
Join Date: Apr 2005
Location: MD
Bikes:
Posts: 773
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Aren't mountain derailleur's 9sp and the current Ultegra's 10sp?

Road cranks are 130BCD or 110BCD. 130 is the standard and 110 is the compact. 130 can go as small as 38T. So it depends on what BCD your cranks are. I suspect your stock cranks are 130, so unless you swap them out for a 110, you won't be able to install a 34T. Seems like an expensive upgrade. I find a 38T chainring and a 27T cog to be plenty of gearing. If I can't get up that hill, then I should be running.

As for a compact FD. I think it's mostly marketing. The only place I can think of where it would help is if you're running a small big ring (say 42/44) and the derailleur cage is too long to clear the chain stay while being low enough on the seat tube to be just a penny's width above the big ring.
bitterken is offline   Reply With Quote
Old 07-11-07, 01:00 PM   #5
cachehiker
Soma Lover
 
Join Date: Dec 2004
Location: Logan, UT
Bikes: one bike for every day of the week
Posts: 765
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by bitterken
Aren't mountain derailleur's 9sp and the current Ultegra's 10sp?
http://store.interlocracing.com/10elcas.html

They don't shift as well as the high-end Shimano cassettes but I'm happy with their 9-speed 11-28 cassette. It shifts about as well as a Shimano HG50 or HG70. I'd be inclined to believe that if you're careful to stay within the Shimano CYA 33-tooth limit (48-38+32-11=31 teeth) that a 9-speed mid-cage mountain derailleur would shift it just fine.
cachehiker 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 01:53 AM.