STI compatability

rich164h

Hi,
I've got an early '90s Dawes Horizon which is fitted with a Shimano Exage groupset including down tube shifters. Whilst I don't have a particular problem with down tube shifters, I need to change the brake levers anyway as there's some damage to them so I was wondering if it would be possible to swap them out for more modern STI shifters and therefore do away with the downtube shifters. I appreciate that the number of gear selections won't match but i was hoping that this could be constrained by the deraileur limit screws (is that realistic?), but I wasn't at all sure if the pull ratios for either the derailleurs or the cantilever brakes would be the same.

Can anyone advise on whether using STIs would be possible without changing out other parts of the drive train?

Thanks

Rich

ride_whenever

how many gears do you have???

drlodge

If its a 6 or 7 gear bike (126mm OLN), and you can get a 7 speed cassette to fit, then the 8 speed Shimano 2300 shifters will work.

rich164h

7 speed, although I can't remember if it's 126mm or 130mm OLD. I think it might be 130mm as the replacement wheel that I got a couple of years ago have 105 hubs and the spa cycles website states those as being 130 - although that's at odds with the Sheldon brown site. One things for sure though, I've had no problems with the wheels not fitting!

That doesn't matter anyway does it? I wasn't planning changing the cassette, just replacing the current brake levers with newer STI shifters and thereby removing the down tube shifters. Maybe I've just misunderstood what you mean?

drlodge

What's important is the spacing between the sprockets e.g. Shimano 7 speed is 5mm, 8 speed is 4.8mm - close enough to mean you can use an 8 speed STI shifter on a 7 speed cassette.

If you have 130mm OLN and you can change the cassette to 9 or 10 speed then that opens up many more options, since you can use the more modern 9 or 10 speed STI shifters.

getprg

You might want to start here first

http://www.bikeradar.com/forums/viewtopic.php?f=40004&t=12827591

If you've read Sheldon Brown you will already know that rear mechs aren't indexed - the levers are. In theory therefore shimano mtb mechs will work with shimano sti levers - but not 10 speeds due it seems to the pull ratio.

To be on the safe side stick with 9 (or fewer) speed sti levers - Sora, old Tiagra etc.

rich164h

drlodge wrote:

What's important is the spacing between the sprockets e.g. Shimano 7 speed is 5mm, 8 speed is 4.8mm - close enough to mean you can use an 8 speed STI shifter on a 7 speed cassette.

If you have 130mm OLN and you can change the cassette to 9 or 10 speed then that opens up many more options, since you can use the more modern 9 or 10 speed STI shifters.

ok, gotcha! thank you , that makes sense.

rich164h

getprg wrote:

You might want to start here first

http://www.bikeradar.com/forums/viewtopic.php?f=40004&t=12827591

If you've read Sheldon Brown you will already know that rear mechs aren't indexed - the levers are. In theory therefore shimano mtb mechs will work with shimano sti levers - but not 10 speeds due it seems to the pull ratio.

To be on the safe side stick with 9 (or fewer) speed sti levers - Sora, old Tiagra etc.

Thanks I'll take a look at that link.

I'm not sure what you mean about the rear mechs not being indexed though and it all being down to the shifter. Well, clearly that's true to a point but I do still need to make sure that the pull ratio on the rear derailleur matches the pull provided by the shifter otherwise it will move too much/little with every click, and it's this compatibility that I'm not sure about between, say modern 2300/sora shifters and the old exage RD. 20 or so years is a long time for Shimano to not have made changes in this sort of thing.