How do I know if a larger cassette will fit?

[Rohloff_Brompton_Rider]

After yesterday's Season of Mists audax, it has become crystal clear I need to lower my gear inches.
My bikes got full Ultegra triple chain set 10 speed . I've already gotten the smallest 30 tooth front ring on (I think I'll need to check) and the biggest Ultegra cassette seems to be 30. Some people had 32 tooth cassettes on. How do I know or do any of you already know...can I fit a 32 tooth cassette?

 

[boydj]

A triple chainset will have a long-cage derailleur, so it should be able to handle another couple of teeth ok.

 

[Spoked Wheels]

A triple chainset will have a long-cage derailleur, so it should be able to handle another couple of teeth ok.

I don't see why a triple chainset would need to have a long cage derailleur. I'd love to know though.

A long cage derailleur (MTB type derailleur if you like) would handle up to 34T cassette.

I managed to find a medium cage Shimano 105 GS derrailleur that works with a 32T cassette.

 

[PpPete]

Even the older Ultegra medium cage rear-mech (rated to 27T max cassette) will handle a 11-32 cassette on a triple if the chain is the right length.
The newer ones (rated to 30T ?) should have no trouble.
Also I guess your front may be 50/39/30? Your set-up will likely cope with more than that too.
I run 53-39-28 on one bike and 50-38-26 on another.
Spa are usually the best place to find odd chain-rings.

I'd not recommend a long-cage mech (designed for MTB) on a road bike. My experience is that the geometry goes a little screwy and it makes it awkward to get the back wheel in and out in case of p********.

 

[fossyant]

Blimey 30 x 32. that will go up walls.

 

[Rohloff_Brompton_Rider]

Even the older Ultegra medium cage rear-mech (rated to 27T max cassette) will handle a 11-32 cassette on a triple if the chain is the right length.
The newer ones (rated to 30T ?) should have no trouble.
Also I guess your front may be 50/39/30? Your set-up will likely cope with more than that too.
I run 53-39-28 on one bike and 50-38-26 on another.
Spa are usually the best place to find odd chain-rings.

I'd not recommend a long-cage mech (designed for MTB) on a road bike. My experience is that the geometry goes a little screwy and it makes it awkward to get the back wheel in and out in case of p********.

Yep mine does have 30t stamped on the cage so I guess 32 would be fine.

Re fossy's post, when I'm fresh yes probably, but as I'm fat and unfit and still recovering from a busted elbow, I'll be glad of the reserve gears when going up the likes of Widdop from Thursden valley.

Fresh and without a busted elbow I'd probably be able to do it on 65" fixed.

 

[boydj]

I don't see why a triple chainset would need to have a long cage derailleur. I'd love to know though.
.........................

"The difference is in chain wrap capacity. The triple rear derailleur with a longer cage is able to handle a wider range of gear combinations. In other words it can take up more slack when you use the granny ring with the smaller cogs and with a chain long enough to handle the big to big combination. You could still use the double rear derailleur if you are careful to not use the smaller cogs with the granny ring."

 

[potsy]

I went for the lower granny ring option on my bike when you and Colin tried to kill me on the Trawden ride, 28t instead of the stock 30, could go 26t to give you even lower gearing

 

[Rohloff_Brompton_Rider]

I went for the lower granny ring option on my bike when you and Colin tried to kill me on the Trawden ride, 28t instead of the stock 30, could go 26t to give you even lower gearing

SOM is the most tired I've ever been on a ride and I've never felt so rough the day after a ride, I think I should have bailed tbh. Lower gears would have been a massive help

 

[clid61]

MTFU pedal harder

 

[PpPete]

Shimano rear mechs designed for road triples are designated as medium-cage or "GS" (not long-cage).
They have sufficient chain-wrap for a wider than usual spread on the front and at the same an 11-32 cassette.

I have very little patience for unhelpful MTFU type comments, not exactly "technical know-how" is it?

 

[potsy]

Shimano rear mechs designed for road triples are designated as medium-cage or "GS" (not long-cage).
They have sufficient chain-wrap for a wider than usual spread on the front and at the same an 11-32 cassette.

I have very little patience for unhelpful MTFU type comments, not exactly "technical know-how" is it?

Can only agree Pete, just because some can climb anything with the standard gearing doeasn't mean everyone can, especially if you are on the 'portly' side.

Without hijacking brompton's thread completely, would you have any idea if a rear mech that came on a compact set up 50/34 and a 12-28 cassette would be able to take a 30t rear sprocket?
It's a 105 presumably short cage.

 

[Nick Stone]

Same as above can you guys help on this one as well
Ultegra compact currently running a 11-25 on back can I go to a 12- 28 or 30?
It says my rear mech is
Shimano Ultegra GRAY NEW 6700A/SS 20 Speed - no idea what that means and will I need a new chain?


Sorry to jump in on thread

 

[slowmotion]

If you look in shimanotechdocs and thrash about a bit, you will find the official Shimano rules about the gear combinations that any rear mech can handle. They are extremely conservative. I'm four teeth over the limit and it works fine with my 105 triple. 28 on the front and 28 teeth on the back. I think that is a 26 inch gear on my bike. Davywalnuts of this parish went up Ditchling Beacon on a 66 inch gear. Massive respect!
No, I have no intention of MTFU.

 

[dellzeqq]

View: http://www.youtube.com/watch?v=Jy-0ZwgeSvc