Change cassette from 11-25 to 11-28?

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Change cassette from 11-25 to 11-28?

Postby bikingbert » Sat Sep 22, 2012 8:39 am

I'm planning to buy a second-hand quality sporty road bike. Most have gearsets geared at 50/34 and 11/25. So the lowest ratio is 34/25 which is a bit high for where I live (lots of hills). Bike would probably have Shimano 105 or Campag Veloce, but maybe Ultegra. (I'd consider a triple, but they are rare)
Can I replace the cassette with say 11/28 or 13/29?? Is there a problem that the chain will be too short? Any other tips?
Thanks!
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Re: Change cassette from 11-25 to 11-28?

Postby cycleruk » Sat Sep 22, 2012 9:23 am

I fitted a 13-29 to a Centaur 50/34 set up with no problems.
I also have a 12-28 on an old Ultegra double.
Both set ups work fine but check the chain length as you may have to add links.
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Re: Change cassette from 11-25 to 11-28?

Postby Brucey » Sat Sep 22, 2012 10:07 am

the largest sprocket you can fit varies with the rear mech model. The manufacturer's specification will either mention the hanger length or assume that it is short. In addition they seem to be a little conservative anyway.

The net result of this is that you can usually go 1T larger and sometimes 2 or 3T larger than the spec (on a slightly longer hanger, say). Each 2mm of hanger length (or 'B' screw adjustment) is 'worth' an extra tooth on the largest sprocket size.

A 'safe' chain length is usually to fit the chain so that it is the correct length to run round the large-large gear combination plus two links.

If you exceed the total mech capacity then the chain may run slack in the small-small combinations. This is often OK if you know about it; those gears may well be duplicated on the big ring anyway, so you don't necessarily need to use them.

cheers
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Re: Change cassette from 11-25 to 11-28?

Postby Ayesha » Sat Sep 22, 2012 2:55 pm

Personally, I'd go with the 34 to 25.
Ride up some hills and wait for my legs to get stronger.

I'd spend the £25 that the cassette would have cost on some nice fillet steak and preserved my bragging rights.
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Re: Change cassette from 11-25 to 11-28?

Postby scarrabri » Sat Sep 22, 2012 9:24 pm

Hi i have just had the Gears fitted to my Raleigh Banana bike because it was too difficult to peddle ,i am new to Road cycling so i am not sure what i have but it is a dream ride,Brian.
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