BikeRider22

Dear Experts,

I'm in the process of upgrading an old road bike's cluster
from Shimano 8 speed to 9 speed.

So far, I have 9 speed
- front cranks
- rear cluster

What I'm wondering is which
downtube shifters can I use.

I have a set of Shimano SL-7900 downtube shifters.

q1:
If I get a 9 speed Shimano rear derailleur (say Altus),
will the SL-7900 downtube shifters work with with 7900 DT shifters?

...

Now, I also have a 10 speed rear derailleur (105)

q2:

Could I use the 10 speed downtube shifters and 105 rear derailleur
with the 9 speed cassette?

Thanks a lot!

zacster

If you want to mix and match you should set those shifters to friction. Indexing will never work properly unless you get lucky and find that one specific Shimano product that magically has the proper spacing/cable pull/der ratio.

70sSanO

For index downtube shifters, you need SL-7700 if you are using a 9 speed cassette. The left (FD) shifter is friction so basically any FD can be used.

Any SIS mtb RD up to 9 speed and any SIS road RD up to 10 speed can be used, except Tiagra 4700. These are all the original SIS actuation ratio of 1.7mm of lateral movement to 1mm of cable pull.

The shifter determines how much cable is pulled. You need to match the shifter to the number of speeds because the spacing between the cassette cogs changes based on the number of speeds. You can’t just buy 10 speed shifters and only use 9 shifts. The shifters will not pull enough cable to index properly.

John

Hondo6

As 70sSanO stated, you have to match shifters, cassette, and RD pull ratio. However, in "Shimano-land", a 9-speed RD has the same pull ratio as a 10-speed road RD. The two RDs should be interchangeable so long as other parameters (lateral movement capacity, chain wrap, min/max cog sizes, etc . . . ) are what you need.

However, you also have to match shifter and cassette cog spacing. Thus, for 9-speed rear cassettes you'll need 9-speed shifters; 10-speed has different cog spacing, so 10-speed shifters won't work well (if at all) even if you lock out high or low using limit screws.

You indicated you have a 105 10-speed RD. The SL-7900 is 10-speed. You could go a pure 10-speed system using those 2 and a 10-speed cassette. 10-speed cassettes are 1mm shorter than 8- or 9-speed due to narrower cogs and cog spacing, so you'd need a 1mm spacer behind it if you go that route. Only problem might be the front chainrings - 10-speed chains are narrower than even 9-speed.

I've heard that older (7/8 speed) chainrings work with later drivetrains having more gears; I can't remember the specifics. Haven't tried that myself - yet.

BTinNYC

What Hondo6 said.

You've got the hard-to-aquire 7900 dt shifters, so why not go 10 speed. I have no problem with a mixed older 8 speed crankset with 10 speed rear.
Shimano 105 10 speed FD, GS RD, and brifters with Ultegra 7400 crankset and an 11-36 cassette...for that nearby bit of 19% grade.

BikeRider22

Found this PDF from Shimano

2010-2011
Shimano products compatibility information
https://productinfo.shimano.com/down...ibility_en.pdf

The SL-7900 downtube shifters are not listed at all

BikeRider22

Also found:

Shimano 2009-2010
Products Line-up Chart
PDF

https://productinfo.shimano.com/down...E-UP_CHART.pdf

Which does mention the SL-7900 downtube shifters,
But not compatibility

BikeRider22

Also found:

Shimano 2012-2013
Products Line-up Chart
PDF

https://productinfo.shimano.com/down..._public_en.pdf

Which also does mention the SL-7900 downtube shifters,
But not compatibility

BikeRider22

Also found this by Sheldon Brown

https://www.sheldonbrown.com/dura-ace.html

https://www.sheldonbrown.com/dura-ace.html#alternate

icemilkcoffee 

Did you see this document on the Shimano site?
https://si.shimano.com/en/pdfs/ev/SL...-7900-2872.pdf
It clearly says the SL7900 is for 10 speed.

himespau 

Which 8 speed do you have? If memory serves (and I'm probably remembering incorrectly) 8 speed Dura Ace rear derailleurs had the same pull ratio as 9 speed rear derailleurs (which would mean you wouldn't need to buy a new RD, and you don't need a new FD unless you're going from 2x to 3x or standard to compact cranksets) but other 8 speed did not.

alcjphil

You have a set of 7900 downtube shifters. You have a 10 speed compatible rear derailleur. Ditch the 9 speed cassette. Buy a 10 speed chain(which you will need anyway even with 9 speed) and cassette. Assemble. All will be good

70sSanO

I’ve used alternate cable routing when I switch out a 7401 RD for an M910 RD and the shifters were 7401 7 speed.

In a nutshell changing the attach point alters the distance to the RD pivot point; closer moves it more and further away moves it less.

I call it a 10% rule. It was originally a DA 7400 work around. Because the RD actuation difference between standard 1.7 and DA 1.9 was roughly 10% using the “alternate” routing moved the RD laterally about 10% more.

Since 10 speed cog spacing is 3.95mm and 9 speed is 4.35mm, using the alternate routing with a 10 speed shifter moves the RD an internet extra 10% so in theory it should work. Likewise, in theory, you could just slap an 8 speed DA 7402 RD, with a 1.9 actuation, use 10 speed shifters, and use a 9 speed cassette and no alternate routing.

In reality, I have found that you may have to tinker with the alternate routing a bit to get the best shifting. I’m guessing there is less margin of fudge or slop in the routing with closer cog spacing.

It is not something I would ever consider using unless I already had the components and didn’t want to buy the correct ones.

In my case I already had the 7 speed DA shifters (spring loaded left) and just wanted to use a RD with the capacity for a wider range freewheel.

John

BikeRider22

Also found the:

Jtek ShiftMate Bicycle Shifting Adaptor
https://www.sheldonbrown.com/harris/shiftmate.html


Jtek Shiftmate
https://www.peterwhitecycles.com/Shiftmate.php

Which is supposed to allow different SIS shifters to work with different cassettes.
Including Shimano with Campagnolo, or vice versa

Company website here:
Shiftmate 2 for mating different speed shifters to different speed drivetrains.
This model is for mating different speed shifters to different speed drivetrains.

70sSanO

So you are willing to spend $75 just so you can run your SL-7900 downtube shifters with a 9 speed cassette.

Others have suggested going to a 10 speed cassette and using either the Altus or your 105 RD.

You could use the 105 and a 10 speed cassette probably save $25 while adding an extra gear.

Or get a 10 speed cassette and an Altus RD for the price of a Shiftmate.

John

csport

... or get proper 9 speed downtube shifters if you want 9 speed.
Your 105 10 speed RD will work with 9 speed.

70sSanO already said this in post #3.

zacster

I didn't read it closely enough to realize he had 10sp shifters and 10sp rear derailleur. The solution is simple then. Put a 10sp cassette on the rear. The only issue is that earlier hubs can only take 9 of 10 cogs, in which case you leave one off along with its spacer. Use a 10sp chain with it. Don't mess with alternate routing methods or Shiftmates.

If the OP were to buy anything he should just get a 10sp cassette of his choosing. Ultegra is about $75 at Universal Cycle, 105 around $50. You can shop around and get cheaper too I'd imagine. I believe MTB cassettes are compatible too. MTB Dynasys 10sp shifters and derailleurs are NOT compatible though and basically only work with each other.

All the Ultegra cassettes go up one tooth 11 through 15 and then 2 after that. So 11-12-13-14-15-17-19... Drop the 14 and you won't even notice the gap. All of the cassettes have different groupings of cogs though, you may be able to drop the largest or smallest, or maybe not. I vaguely recall I dropped the smallest cog on an HG62, or was it the largest? I don't remember. I bought a 10sp hub ultimately and put it back. It worked just fine as 9 of 10 but I wanted a matching hub to the front dynamo hub.

alcjphil

The OP currently has 8 speeds. A 10 speed cassette will fit the hub without modification.

70sSanO

This did trigger the OP’s freehub body. If it is a pre-c body, like a UG/HG, then it is an issue for an 11t regardless of the number of speeds.

John

zacster

Was it the original 7sp hubs that wouldn't fit? My hub was a 7sp LX mtb type hub and 10sp would not fit. I ran 9 of 10 though without problem.

BikeRider22

@csport

Thanks for the helpful response to the questions.

Do you know if these 9 speed shifters are indexed/SIS?

microSHIFT Down Tube Shifter Set, 9-Speed, Double/Triple, Shimano Compatible, Silver
https://www.modernbike.com/microshif...patible-silver

I have a number of friction shifters, but I want to upgrade to SIS if I can

Sunrace also has 9 speed shifters.
https://www.sjscycles.co.uk/gear-shi...-pair/?geoc=US

But, like so many websites, the SIS detail is not mentioned.
Sigh.

BikeRider22

To be clear,


I have 9 speed:
front chainwheels
rear cluster

And I'll be going with 9 speeds.
Period.

Hopefully, with SIS/indexed shifters

In fact the 9 speed rear cluster is custom
gearing from MICHE. It cost a lot more in shipping
to import from Europe.


So No, I'm NOT looking for work arounds, or to
to buy yet another drivetrain, or components.

Thanks to everyone who wrote on how I might accomplish my goals

70sSanO

If you have everything, set it up and try the alternate cable routing. My point of not going that direction only applies if you don't have the components.

Use your 105 RD and see how it works. Worst case you are out a shift cable.

This is pretty simple, you get it to work or you don't.

John

himespau 

The microshift downtube shifters are indexed right shifter and friction left. Sunrace should be as well.

70sSanO

However, Dura Ace shift levers are light years better. Shimano's spring loaded light action left shift levers are so nice since they wind up and counteract the FD return spring. I have an Ultegra SL-6401 lever that is so balanced to the FD that I don't even need any friction applied. I can loosen the attach bolt and the lever doesn't move.

John