7 speed cassette compatibility

Michael Falk

I've read quite a bit of information at SheldonBrown but I'll seek an opinion here.

My old Cannondale road bike, that I rarely ride & is bit high geared for me, I'm thinking of putting on one of my spare 7sp atb cassettes (13-28 or 13-30) instead of its current 13-23. I have a good old XT rear dérailleur to replace the current short arm Shimano 600 dérailleur. I'll keep using 52-39 chainrings. I have downtube index/friction shifters.

Will there be any problems doing this (especially cassette compatibility)? Are the short chainstays likely to produce any problem with this wider range gearing?

Thanks, Michael

Weejie54

Can't see any problems. You will no doubt have to replace the chain.

satanas

Either 28 or 30T will most likely be fine with a road rear mech. Provided the chain you use isn't too short and has a similar amount of wear as the cassette all should be well, but don't expect a new chain to work with an old cassette or vice versa.

Weejie54

Either 28 or 30T will most likely be fine with a road rear mech

It's getting an XT mech, though.

Michael Falk

Thanks for the replies.

I'm not sure what you mean Weejie54 related to "It's getting an XT mech, though"; I have an old one that was still running well.

I realise mixing old & new parts can result in a rough drivetrain. I may have to change the chainrings too, especially the far greater used 39 tooth one.

It seems like I won't have a problem at all with the dérailleur, I won't use larger than a 30 tooth cog. I have the old XT dérailleur anyway, so I might use it. I can't really see any disadvantage about using it, just a slight weight increase.
I'll see how it goes.

Monty Dog

You should be able to get away with the 13-28 and your existing short-arm mech. The 30 sprocket may foul the top jockey wheel and so need for MTB mech. Your bike frame geometry has no bearing on the functioning of the drivetrain.

Weejie54

I'm not sure what you mean Weejie54 related to "It's getting an XT mech, though"; I have an old one that was still running well.

Well, you said in your post:

I have a good old XT rear derailleur to replace the current short arm Shimano 600 derailleur.

Which implied that you were going to fit an XT mech. If you intend to do that, the capacity of a road derailleur is irrelevant. In my book, XT is MTB stuff. If you do fit an XT mech, you will need enough chain to wrap it and your largest rear sprocket can be a wee bit bigger than 30t, so no problems in achieving what you intend.