7

I want to go bikepacking with my old road bike. The road bike has a standard crankset (53/39, double not triple), and an 11-28 cassette. The groupset is Shimano Ultegra 6500.

Because I want to do some large climbs in the Alps, I would like a lower gear. I considered changing the crankset, but that seems a bit expensive.

I also have two old city bikes that have mountainbike derailleurs that I could remove: One is a Shimano Deore LX 9 speed, the other is a Sram s500 RD 9 speed.

Can I use one of these derailleurs to fit a 12-36 cassette to my bike, or will that exceed the total capacity of the drivetrain with the non-compact chainset?

I mention both the Shimano and the Sram derailleur because I think the Shimano is more likely to work, but in slightly worse condition than the sram - so if the Sram works too, I will try that.

Sram Rear Derailleur enter image description here

10

All nine speed Shimano shifters index with all pre-ten-speed Shimano MTB derailleurs.

All nine speed long cage MTB derailleurs with long (SGS) cages will have total capacity sufficient to run any cassette they can clear with a double in front.

36t large cog cassettes came out late in 9-speed mountain's life. Only a very few Shimano 9 MTB derailleurs are rated to clear a 36t for their largest cog spec. Most do 34 and a few only 32.

The SRAM you have is a 1:1 and has no compatibility with the shifter.

| improve this answer | |
  • FWIW, shimano's ratings are very conservative to ensure that the shifting is as perfect as possible. If you can't get the appropriate clearance using the existing B screw adjustment on that deralluer, Wolftooth makes a derailleur mount extender for just this situation. I have used it and 9 spd Xt derailleurs to run an 13-40t 9 speed cassette. – Fred the Magic Wonder Dog Sep 21 at 15:56
5

Yes, you can use the Shimano 9 speed MTB derailleur with the 9 speed Ultegra 6500 shifters. This is because on older MTB groups up to 9 speed and road groups up to 10 speed Shimano used the same actuation ratio (ratio of length of cable pulled to cage movement).

The total capacity of the derailleur is a measure of how much chain slack it can handle and should be greater or equal to (difference in largest/small sprocket teeth) + (difference in chainring teeth). I.e., the size of the chainrings does not matter, the difference between them does. The 53/39 rings only have 14 teeth difference (compact 52/36 or 50/34 have 16) which give you a little bit more latitude with the cassette size.

| improve this answer | |
  • 1
    There is at least one Shmano 10 speed road group not using the same actuation ratio. Tiagra 4700. – juhist Sep 20 at 12:33
  • 2
    @juhist GRX 10 speed also – Argenti Apparatus Sep 20 at 12:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.