I want to change my 7 speed freewheel sprocket. It is 13-24 and is it ok to use a 14-28 or to stick to the same size as the original.
I am new to this but am newly obsessed with bikes and my house is full of them.
You will "probably" be O.K. with the 14-28.
The limiting factor is the clearance between the top jockey wheel of the dérailleur and the largest sprocket. Shimano road dérailleurs are only supposed to allow a maximum sprocket size of 27 teeth.
I currently run a Sora long cage mech' on a 13-28 but it is at the very limit.
MTB dérailleurs will clear anything up to 34/36 teeth.
The "B" screw on the dérailleur is there to allow adjustment of the jockey wheel clearance.
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Note that you will reduce your top gear ratio by about 7%, that is, you will travel c20" less in top gear for every rev of the pedals, this means you will be pedaling faster going downhill.
You will also reduce the bottom gear ratio by roughly the same and will find it easier going uphill.
Hiya thanks for the replies... most helpful!