Some crank & chainring questions



openclassmx

New Member
Jun 5, 2007
13
0
0
52
I have a slightly bent large ring on my Trek 2100. I tried to tweak it back, but while it seems to run OK forwards, if I pedal backwards (or do it on the stand, like to lube the chain) it will derail the chain.

Sooooo, I need to replace it. The bike has a Bontrager crank now, and I was considering upgrading the crank now. How do the Bontrager cranks stack up? Would a 105 crank be a step up in quality? And most important, will I need to buy a new BB to change brands from Bontrager to Shimano?

Should I just buy a new chainring and forget it?

Thanks!
 

mskaufman84

New Member
Jul 6, 2007
15
0
0
Theres a reason that bontrager cranks dont appear on any higher end bikes. They're cheaper and not quite as good. Depending on your bike setup it may make a pretty big difference. If your entire bike is shimano components (like 105) it will shift a lot better. Shimano parts are meant to work well with each other, and when they all come together they form a holy union and everything just works well. If your entire bike is 105 i would definately go ahead and get the entire crank (if you are willing to throw the money into it) As fas as the BB goes, if you are not changing the kind of crank (ie double to triple) then the bottom bracket is going to be fine. Good luck and go easy on those chain rings!

openclassmx said:
I have a slightly bent large ring on my Trek 2100. I tried to tweak it back, but while it seems to run OK forwards, if I pedal backwards (or do it on the stand, like to lube the chain) it will derail the chain.

Sooooo, I need to replace it. The bike has a Bontrager crank now, and I was considering upgrading the crank now. How do the Bontrager cranks stack up? Would a 105 crank be a step up in quality? And most important, will I need to buy a new BB to change brands from Bontrager to Shimano?

Should I just buy a new chainring and forget it?

Thanks!
 

hd reynolds

New Member
Nov 15, 2005
813
0
0
mskaufman84 said:
As fas as the BB goes, if you are not changing the kind of crank (ie double to triple) then the bottom bracket is going to be fine. Good luck and go easy on those chain rings!
New 105 BB is integrated outboard type. Older 105 is Octalink. A bonty cheapo is not integrated BB and proly an isis. If he's chainging to a new crank better get the entire ensemble.
 

openclassmx

New Member
Jun 5, 2007
13
0
0
52
The Octalink one is what I was considering (makes sense that it's older, as it is available for $49.99). If I need a new BB I guess I'll just have to get that too. I definately want to upgrade as I did not hit the chainring on anything, so the only way it could have bent was from torque. I don't want that to happen again.
 

gclark8

Member
Apr 13, 2004
3,522
6
0
73
openclassmx said:
...... I definately want to upgrade as I did not hit the chainring on anything, so the only way it could have bent was from torque. I don't want that to happen again.
Taking off from stationery in a lower gear and climbing at a higher cadence will fix that. ;)
 

openclassmx

New Member
Jun 5, 2007
13
0
0
52
gclark8 said:
Taking off from stationery in a lower gear and climbing at a higher cadence will fix that. ;)
Yeah, yeah, I know. But I'd like a chainring that can handle mashing up a hill, which is the hardest I've ever been on it. I'd also be open to just finding a stronger chainring that will fit my existing crank.
 

artemidorus

New Member
Mar 10, 2004
2,307
0
36
I'd be surprised if you bent that chainring simply through riding. More likely your bike took a knock that you didn't know about.
 

gclark8

Member
Apr 13, 2004
3,522
6
0
73
openclassmx said:
Yeah, yeah, I know. But I'd like a chainring that can handle mashing up a hill, which is the hardest I've ever been on it. I'd also be open to just finding a stronger chainring that will fit my existing crank.
OK, Specialities TA from France,
local agent Greenspeed, Vic,
USA agent Harris Cyclery.