Sprocket Query
03-13-05, 07:15 PM
#1
Raleigh20 PugFixie, Merc
Thread Starter
Sprocket Query
Hi - Recently started running a SRAM Spectro 7 rear hub in my radically remodelled Raleigh Twenty which is running like a dream.
I'm thinking about making her run a bit quicker though - it seems I'm not really using the two lowest ratios on even the steepest hill on my commute and thought it might be good to upgrade either the chainring (currently 52t) to maybe 54-56t (or bigger), or to get a smaller sprocket on the hub; or even perhaps a combination of the two to get a higher top end speed and get more use out of the unused bottom ratios.
Basically - I've never done this before and wondered if anyone had any suggestions. I'm not sure how easy it is to get SRAM/SACHS compatable rear freewheel sprokets for their hub gears (I live in London, UK) nor am I sure of the best way of predicting how big an improvement doing this would be and being sure I don't over-egg the upgrade and make the bike too much of an effort to ride.
So - more teeth on the front, less on the rear or perhaps a mix of the two?
Any advise appreciated in advance.
I'm thinking about making her run a bit quicker though - it seems I'm not really using the two lowest ratios on even the steepest hill on my commute and thought it might be good to upgrade either the chainring (currently 52t) to maybe 54-56t (or bigger), or to get a smaller sprocket on the hub; or even perhaps a combination of the two to get a higher top end speed and get more use out of the unused bottom ratios.
Basically - I've never done this before and wondered if anyone had any suggestions. I'm not sure how easy it is to get SRAM/SACHS compatable rear freewheel sprokets for their hub gears (I live in London, UK) nor am I sure of the best way of predicting how big an improvement doing this would be and being sure I don't over-egg the upgrade and make the bike too much of an effort to ride.
So - more teeth on the front, less on the rear or perhaps a mix of the two?
Any advise appreciated in advance.
03-13-05, 07:52 PM
#2
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If you can keep the chainline straight, changing the chainring, or even the whole crank, is the easiest way to change gearing on a internal gear rear hub. I've seen 110 BCD chainrings up to 56T.
03-13-05, 08:59 PM
#3
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seems to me it would be a lot cheaper and easier to just replace the rear cog. it's most likely based on the three-spline, Sturmey-Archer and (most) coaster-brake cog pattern. it might take a little looking but there's quite a few choices in gearing; Brompton, Birdy, and maybe Moulton in the UK probably would stock such cogs.
03-13-05, 10:57 PM
#4
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Originally Posted by dafydd
seems to me it would be a lot cheaper and easier to just replace the rear cog. it's most likely based on the three-spline, Sturmey-Archer and (most) coaster-brake cog pattern. it might take a little looking but there's quite a few choices in gearing; Brompton, Birdy, and maybe Moulton in the UK probably would stock such cogs.
See our Sturmey-Archer page https://harriscyclery.com/sturmey (SRAM, Sturmey-Archer and Shimano internal hub sprockets are interchangeable.)
Sheldon "Small Is Beautiful" Brown
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+-----------------------------------------------------------+ | Oh, my ways are strange ways and new ways and old ways, | | And deep ways and steep ways and high ways and low, | | I'm at home and at ease on a track that I know not, | | And restless and lost on a road that I know. | | --Henry Lawson | +-----------------------------------------------------------+
03-14-05, 03:25 AM
#5
Raleigh20 PugFixie, Merc
Thread Starter
thankyou people... Very helpful, as is the gear calculator.
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My Raleigh Twenty site | foldr : A flickr pool | #6460, #5632 & #3407 on the fixedgeargallery
My Raleigh Twenty site | foldr : A flickr pool | #6460, #5632 & #3407 on the fixedgeargallery
