Putting bigger rings on mountain crank
#1
Senior Member
Thread Starter
Putting bigger rings on mountain crank
I have a mountain bike I want to use for more commuting. What issues will I have with putting bigger rings on it? Will I have to change out the front derailleur? What else do I need to consider?
Any input is appreciated.
Any input is appreciated.
#2
Call me The Breeze
You might need a new derailleur, but probably you'll just need to move it up a bit. Your main concern is going to be chainring to chainstay clearance. 48T is usually a pretty good big ring on a commuter mtb.
#3
Senior Member
First, does your crank have bolted on chainrings? Second, do you have any particular reason for wanting to stick with the same crankarms?
I ask those questions because chainrings are generally not very cheap. To replace all three chainrings, or even just the two largest rings, on a medium to low end crank will probably cost you as much as buying a whole new crank. If the bike is low end, you can get VERY cheap 48/38/28 cranksets which are great for commuting (in my opinion of course).
This is nothing special but it'll get the job done:
https://www.universalcycles.com/shopp...&category=2637
This is about as cheap as it gets:
https://www.niagaracycle.com/product_...oducts_id=6611
Here's something nicer with slightly smaller rings:
https://www.speedgoat.com/product.asp...=32&brand=1004
Do note that you may need a new bottom bracket depending on which crankset you go with. The above are all square taper so if you have a different interface and don't want to swap, you'll need to find something else. Your current front derailler should have no trouble with a 48 tooth big ring. If you wanted to go with a 50 or 52, then you might want to consider a road front derailler though that brings it's own set a of issues, and for that reason I'd recommend sticking with a 48. A 48/11 combo is bigger than a 52/12 (common road bike top gear) anyway.
I ask those questions because chainrings are generally not very cheap. To replace all three chainrings, or even just the two largest rings, on a medium to low end crank will probably cost you as much as buying a whole new crank. If the bike is low end, you can get VERY cheap 48/38/28 cranksets which are great for commuting (in my opinion of course).
This is nothing special but it'll get the job done:
https://www.universalcycles.com/shopp...&category=2637
This is about as cheap as it gets:
https://www.niagaracycle.com/product_...oducts_id=6611
Here's something nicer with slightly smaller rings:
https://www.speedgoat.com/product.asp...=32&brand=1004
Do note that you may need a new bottom bracket depending on which crankset you go with. The above are all square taper so if you have a different interface and don't want to swap, you'll need to find something else. Your current front derailler should have no trouble with a 48 tooth big ring. If you wanted to go with a 50 or 52, then you might want to consider a road front derailler though that brings it's own set a of issues, and for that reason I'd recommend sticking with a 48. A 48/11 combo is bigger than a 52/12 (common road bike top gear) anyway.
#4
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Sheldon Brown has a nice gear calculator that'll give you top speeds at various ratios and cadences, check it out.
If you haven't got a commute that's out of the ordinary you'd probably benefit more from going to a road cassette than messing about with your rings.
#5
Thrifty Bill
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+1 Change the cassette, cheaper option.