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swapping cranks to 52-36, need new BB ?

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swapping cranks to 52-36, need new BB ?

Old 02-12-14, 01:48 PM
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swapping cranks to 52-36, need new BB ?

I am running ergomo cranks 53/39 in a Lemond with regular english BB. I think they are square taper cranks, bcd 135 so can't put on smaller chainrings.

Signed up for a charity ride with a lot of long climbs, and after looking over the route and gearing charts, decided I should switch to 52-36 chainrings, which means finding cranks with 110 spacing.

My budget is tiny, so looking for the least expensive option. Checked ebay and most of the cranks I saw are sold with a matching BB. Is it wise to swap BB when getting new cranks, or could I just keep the BB and put new cranks on?

If it is recommended to get cranks and BB together, which sizes fit my english frame?

Could I just buy a new drive side crank in 110, or is it a no-no to mismatch right and left cranks?

thanks!
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Old 02-12-14, 01:56 PM
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BB spindle length is determined by the crankset so, unless you get a new crankset that requires the same spindle length as your current, you will need to swap the BB. Mismatched left and right are fine as long as you get the same crank arm lengths (and don't mind the aesthetics). Your bike will take a standard 68mm, English-threaded BB.
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Old 02-12-14, 02:17 PM
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English is the BB thread standard for fitting in the frame.


crank designs vary the low profile design comes in to meet and allow a shorter spindle


a crank where the arm is straight and square to the BB spindle,

the spindle is longer to come out to where the crank arm is.


I cannot critique what I cannot see i front of me ..

advantage : Brick and Mortar bike shop.. they can see what you cannot describe.

Realistically a 50 34 crank will be easier to find, a common OEM Spec these days so the cost is lower.

52-36 may be a cost of also buying 2 separate chainrings + the packaged 50-34 crank ..

often the crankarms separately will be more than the boxed chainset.
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Old 02-12-14, 02:24 PM
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Also a full crankset will probably be as cheap as the drive side crank arm, spider and rings. Individual sides is not how this stuff usually sold. You will have trouble finding a good deal on just one crank arm..
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Old 02-12-14, 02:31 PM
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if i wanted lower gears and i had already maxed (minimumed? ) out my tooth count for my BCD, i would look at the rear cogs/cassette and see if it offered an opportunity.
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Old 02-12-14, 03:18 PM
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Also, going from a 39 chain ring to a 36 chain rind is about the same as going from a 25T large cog to a 27T cog. So hueyhoolihan's advice might be a simpler option depending on what cassette/freewheel and RD combo you have.
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Old 02-12-14, 06:36 PM
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Originally Posted by CACycling
Also, going from a 39 chain ring to a 36 chain rind is about the same as going from a 25T large cog to a 27T cog. So hueyhoolihan's advice might be a simpler option depending on what cassette/freewheel and RD combo you have.
I have a RD7800 which runs 27t nicely and can be coaxed to run a 28. I would need a new RD to go bigger in the back, and would lose the tighter cassette spacing.
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Old 02-12-14, 08:44 PM
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Curious as to why you are looking at going to 52/36 instead of 50/34? It's the smaller ring that is going to assist with climbing, and while going from 39 to 36 is going to help some, 39 to 34 would be a lot more significant and really make an impact. Of course, I'm a Clydesdale......never met a hill I didn't hate, and there are lots of hills on my riding routes . You may be slim.......and just need a "little" assistance. But as someone else mentioned, 50/34 is a lot more popular and may be easier to find used at a bargain price.
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