Changing a Cassette to a 32.

[Boon 51]

I bought a new Specialized Allez Comp. (endurace) a month ago and before I purchased it I asked the man in the shop if I could change my cassette from an 11-28 to an 11-32, so when the bike arrived he changed it to a 11-32 on a 105 groupset and all was well until I got home and found the chain made a lot of noise. I took the bike back straight away and he fitted a longer chain which sorted the problem.
Today I went to another shop to have a look at a Trek Madone 2.3 with a 105 groupset and asked if I bought the bike could I change the 11-28 cassette to a 11-32 but he said he wouldn't advise it.
What are the rules for changing to a bigger cassette, wouldn't a 11-32 be OK like it is on my Allez Comp as a Shimano 105 groupset is the same on any bike?

 

[Globalti]

From 30 upwards I think you'd be best advised to fit a long-cage derailleur and a longer chain to cope with the greater range of sizes. With a shorter chain on the big ring, accidentally going to the 32 could actually compress the right hand chainstay and possibly even break it. It will certainly stretch the derailleur cage beyond what is reasonable.

 

[slowmotion]

Shimano Techdocs gives specifications for each type of rear derailler. The rules about tooth numbers can usually be stretched a bit. Here's the 105 5600 derailler document.
http://techdocs.shimano.com/media/t...01/SI-5VN0B-001-ENG_v1_m56577569830683908.pdf

 

[Boon 51]

Thanks for your replies..

I will be visiting the Trek shop tomorrow, so I will ask about the longer chain and the longer cage as I think you are right in what you saying..

 

[Peteaud]

I bought a new Specialized Allez Comp. (endurace) a month ago and before I purchased it I asked the man in the shop if I could change my cassette from an 11-28 to an 11-32, so when the bike arrived he changed it to a 11-32 on a 105 groupset and all was well until I got home and found the chain made a lot of noise. I took the bike back straight away and he fitted a longer chain which sorted the problem.
Today I went to another shop to have a look at a Trek Madone 2.3 with a 105 groupset and asked if I bought the bike could I change the 11-28 cassette to a 11-32 but he said he wouldn't advise it.
What are the rules for changing to a bigger cassette, wouldn't a 11-32 be OK like it is on my Allez Comp as a Shimano 105 groupset is the same on any bike?

It actually depends on the bike frame and hanger. Some bikes will run a 32, some wont.

Personally i have had a Giant defy running tiagra with a 32 although it was so close to the limit i would not advise it, and i only did it to see if it would.

The new 6800 rear mechs are longer and will take a 32, although i dont know if it would work. I thought 10 speed road and MTB rear mechs had a different pull, i maybe wrong, but be careful what you use.

 

[Andrew Br]

I'm running 34/32 on my Dirty Disco.
It has a long cage 10sp Ultegra RD and it works beautifully.
I think that I might even get away with a 34 rear cog.

Peteaud is correct though; it depends on the bike frame and/or hanger.

.

 

[fossyant]

Don't over push the limits without being very careful. If you need a bigger rear cassette, get a longer cage mech to be safe.

 

[Kies]

Would i need a longer cage mech to go from 11-28 to 12-30 on my Defy?

 

[Peteaud]

Would i need a longer cage mech to go from 11-28 to 12-30 on my Defy?

Probably not, my Defy (2010) Tiagra 9 speed runs a 12-30 no issue, 2012 defy 2 came with 10 speed tiagra 12-30 as standard.

 

[RecordAceFromNew]

I bought a new Specialized Allez Comp. (endurace) a month ago and before I purchased it I asked the man in the shop if I could change my cassette from an 11-28 to an 11-32, so when the bike arrived he changed it to a 11-32 on a 105 groupset and all was well until I got home and found the chain made a lot of noise. I took the bike back straight away and he fitted a longer chain which sorted the problem.
Today I went to another shop to have a look at a Trek Madone 2.3 with a 105 groupset and asked if I bought the bike could I change the 11-28 cassette to a 11-32 but he said he wouldn't advise it.
What are the rules for changing to a bigger cassette, wouldn't a 11-32 be OK like it is on my Allez Comp as a Shimano 105 groupset is the same on any bike?

Imho the only real, practical rules are:
1st) chain must be long enough - assuming it was just right with 28T then a pair of links must be added for 32T - if in doubt use a chain length calculator
2nd) no clash i.e. some clearance between top jockey wheel and large cassette sprocket - that clearance can be adjusted by the B screw on the mech
3rd) chain wrap capacity of rear mech adequate - so that chain is not droopy on small front small back
4th) there is no 4th rule - and it appears you are not blessed with trustworthy bike shops...

 

[Boon 51]

One of my other options is a Defy 1 but I will have get the bike from the UK as its not available in Spain..

I will check it out today and will let you know how I get on in the Trek shop.

 

[inkd]

Just out of interest, what about going the other way? As in going from 11-32 down to 11-25? A shorter chain maybe?

 

[Peteaud]

Just out of interest, what about going the other way? As in going from 11-32 down to 11-25? A shorter chain maybe?

shorter chain and adjust B screw.

 

[Boon 51]

Morning all..

Sorry I was out all day, anyway good news.

The Trek bikes I looked at which were the Madone 2.1 and the Madone 2.3 have no problem fitting an 11-32 rear cassette according to the mechanic at the bike shop, which is good news as I didn't have any problems when I had an 11-32 fitted to my Allez Comp. So I dont know what the Giant bike shop was going on about.

PS.. Got some really good prices from the Trek shop in Malaga.

Priced by Evans cycles prices the Madone 2.3 was £1200 ( €1299 in Spain) which at €1.20 exchange rate is €1440, but after discount they offered it to me for €1039 about £850
The Madone 2.1 was €1199 and after discount was offered at €959 about £800 which is £1000 at evanscycles.
The difference for the extra €100 on the 2.3 is Tublees wheels and Shimmano brakes as opposed the standard wheels and Dual Ali brakes what ever they are on the Madone 2.1.
Cheers