Will my rear mech take a larger cassette?

[Hip Priest]

I've currently got an 8-speed 11-26 on the rear. I was thinking of replacing it with a 13-28 for a forthcoming hilly sportive, but is it a simple matter of swapping cassettes or will I need a different rear mech? Thanks in advance.

 

[Peteaud]

Most will take 28t no problem, although its not the mech that entirely dictates it.

You may need to add a link or 2 to the chain tho.

 

[Hip Priest]

[QUOTE 2474131, member: 30090"]Afaik most mechs will take a 28. Google is your answer, what mech do you run?[/quote]


I'm almost certain it's a Shimano 2300.

My bike is a 2010 Carrera Virtuoso, and it's hard finding the spec for it online now!

 

[Hip Priest]

[QUOTE 2474162, member: 30090"]Nope you can't. Google the model number and look at the install sheet....largest sprocket is 26t.[/quote]


Not the answer I wanted to hear, but thanks for preventing me from wasting my cash! I might have to try Plan B (lose weight, train harder)...

 

[Peteaud]

As above Shimano tech says 26T

http://www.shimano.com/media/techdo...01/SI-5XA0A-001-ENG_v1_m56577569830673817.pdf

So it will probably fit as most shimano tech is useless.

The only way you will know is try try it.

Regarding the shimano docs, most list rear mechs as 28T max.

Go look at some bike specs, some have 30 or even 32 fitted as standard.

(look at the spesh roubaix with sora (28t Max) with a 32 rear from the factory).

My own Giant Defy with Tiagra 9 speed has a 30T on (shimano say 28T max)

You might need to adjust the B screw, but this depends on the hanger.

 

[youngoldbloke]

[QUOTE 2474162, member: 30090"]Nope you can't. Google the model number and look at the install sheet....largest sprocket is 26t.[/quote]
Yes I did that, Tiagra* in my case, tech doc says 27T. Fitted 30T cassette, no problems. Didn't have to adjust the B screw either. The only way to find out IME is to try it.
* older version

 

[Hip Priest]

Thanks for that spoke sheet.

Funnily enough it says the total capacity of the smaller socket is 12, but I'm almost certain my cassette is 11-26.

 

[Peteaud]

Thanks for that spoke sheet.

Funnily enough it says the total capacity of the smaller socket is 12, but I'm almost certain my cassette is 11-26.

Most of the Shimano stuff is a guide.

2012 Giant Defy 2 from the Factory with a 12/30 on Tiagra that shimano say has a 28T MAX.

The length of the hanger is critical as some will / some wont.

Cheesney Hawks of this parish also has an impossible set up according to Shimano) (I think)

The only real way is to try.

 

[RecordAceFromNew]

It is not true that the only way is to try.

For each additional tooth the radius of a bicycle sprocket (whether front or back) increases by 2mm (2.021mm if you want to be precise... ). So if the top jockey wheel is definitely over 4mm away from the 26T sprocket when you are in that gear now, then it will definitely be fine.

Even if it is not, try adjust the B screw until it is. If you can do that, then it will also be fine.

With a 2T increase, if your chain is as short as can be in terms of length currently, then you will need to add a pair of links (since you can't add just one because adjacent links are not the same, otherwise one will do, because every 4T increase in total from front and back requires an additional pair of links - a pretty accurate rule). However there is a good chance you don't need a longer chain because the current chain is probably not at the length limit. If I were you I would check with a chain length calculator.

 

[Hip Priest]

Really helpful that. I'll have a butcher's tomorrow. Cheers.

 

[swee'pea99]

I ran a 32 on a 'no more than 28' mech. It chattered a bit, but it worked.