32T F Shimano Cassette Sprocket

I have an Ultegra 12-27 9 speed cassette I use for riding particularly hilly routes with a 53/39 up front. I have an event coming up with at least a couple of 25% climbs well into the ride and I would like the comfort of a bail out gear just in case. I have tried a friends wheel with an 11-32 and with a little adjustment and a slightly longer chain my standard Ultegra rear mech will shift it ok.

A website in the UK is advertising single 32T F Shimano Hyperglide sprockets and what I would like to know is whether I could simply drop the 14 tooth sprocket out of my 12-27 and put this sprocket with a spacer on the back to make a 12-32 which would shift just as well as the 12-27.

Also can anyone explain the Shimano lettering system as on the web site all the single sprockets have code letters after the number of teeth. F in the above example and there are many others such as 21T versions with letter codes H, I, L, M and EF, AC, AF. As these singles are relatively cheap I would consider getting several to mix and match ratios for different events if I could be confident that the resulting cluster would shift as smoothly as a prebuilt cassette.

Graham.

You should have no problem dropping out one of the middle cogs and
adding one to the end. I did a similar thing taking a 14-25, removing
the bolts holding the 25 and replacing it with a 34. Shifting works
just fine.

Using cogs from the same series will give you optimum shifting, but I
never bothered to match them and haven't had any problems.

Graham wrote:

I have an Ultegra 12-27 9 speed cassette I use for riding particularly hilly routes with a 53/39 up front. I have an event coming up with at least a couple of 25% climbs well into the ride and I would like the comfort of a bail out gear just in case. I have tried a friends wheel with an 11-32 and with a little adjustment and a slightly longer chain my standard Ultegra rear mech will shift it ok.

A website in the UK is advertising single 32T F Shimano Hyperglide sprockets and what I would like to know is whether I could simply drop the 14 tooth sprocket out of my 12-27 and put this sprocket with a spacer on the back to make a 12-32 which would shift just as well as the 12-27.

Also can anyone explain the Shimano lettering system as on the web site all the single sprockets have code letters after the number of teeth. F in the above example and there are many others such as 21T versions with letter codes H, I, L, M and EF, AC, AF. As these singles are relatively cheap I would consider getting several to mix and match ratios for different events if I could be confident that the resulting cluster would shift as smoothly as a prebuilt cassette.

Most of the information you want is he
http://sheldonbrown.com/k7.html

Unless your mixing and matching follows the letter codes exactly,
shifting is unlikely to be as good. But it's still likely to be
acceptable.

Also keep an eye on the sprocket spacing, especially if you're
replacing multiple sprockets.

John

"Graham" wrote in message news [snip]

Thanks tcg/John.

If replacing a 25 with a 34 shifts OK then tacking a 32 behind a 27 should be OK. I have ordered one and if that does work OK with my set up I will think about ordering a few intermediate sized ones to experiment with.

Also the Sheldon Brown site did prove very useful in both explaining the letter codes and the article on mixing and matching sprockets on Shimano cassettes also added to my confidence to go ahead.


Graham.