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7800 DT shifters & Force?

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7800 DT shifters & Force?

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Old 06-20-10, 05:01 PM
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robertkat
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7800 DT shifters & Force?

Can anyone comment on the compatibility of Shimano 7800 down tube shifters and SRAM Force derailleurs? It's my understanding that they should work no problems, as I'm told they have the same cable pull. I'm assuming the 7800 bar ends would be the same, yes?
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Old 06-20-10, 05:21 PM
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Down tube shifters works with what ever u put in there specially if you use them in friction mode as it should be, like a man!!!

If you put them in index mode who knows, all the down tube shifters i have used have been always in friction mode. Friction mode is the way to go, no compatibility issues, no problems with brands, no problems period, or you shift right or you dont know how to shift ...

Always have thought that indexing with down tube shifters is a heresy hehehe....

Bar ends no clue. probably they will work fine, shimano and sram are compatible, doubt you will have problems.
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Old 06-20-10, 05:28 PM
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SRAM shifters pull the cable a certain amount for each click, and that amount is different from what Shimano shifters pull. Since the cassette spacing is the same as Shimano's, the derailleurs need to compensate for the different cable pull, so the derailleurs land in the right place. So you have to pair SRAM derailleurs with shifters. But you can use a SRAM cassette with Shimano shifters/derailleurs (and vice-versa I imagine).

So yes there are compatible.
On rear mech the only thing it have to do is to move on par with the cable pull (1:1, 1mm of cable pull=1mm of side movement)
The real compatibility is the indexed shifter with the cassette: shimano spacing cassette with shimano indexed shifters. Sram shifters with sram cassette (non shimano compatible)

So if you have shimano cassette and shimano shifter than it is compatible regardless the RD*.

*most RD's thankfully operate under the same standard which is 1:1 movement.

Yet there are a few oddballs like DA7400 that have different cable pull, campagnolo also have different standards.

Last edited by Asi; 06-20-10 at 05:36 PM.
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Old 06-20-10, 05:40 PM
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ASi, the OP is talking about downshifters, not brifters.
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Old 06-20-10, 05:42 PM
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indexed downshifers - same problem. In friction mode is no problem regarless the RD, cassette, or other things/
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Old 06-20-10, 09:25 PM
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SRAM uses 1:1 cable pull ratio and shimano uses 2:1 (or pretty close to it)

that means shimano has to wind up twice as much cable to shift one gear.
I'm going to take a guess that using an sram RD will make it very very sensitive to input.
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Old 06-21-10, 10:12 AM
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I am using some in index mode with campy components.
Check with J-Tek engineering for compatibility

http://jtekengineering.com/shiftmate_straight.htm
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Old 06-21-10, 02:57 PM
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Most of the above answers are wrong. SRAM 10 road shifters pull 3mm of cable for every shift to move the RD 3.95mm. That is NOT 1:1, it's 1.32:1.

Shimano 10 shifters pull an average of 2.3mm per shift, but the pulls are not uniform, like SRAM. The RD moves the same 3.95mm per shift and that is NOT 2:1, it's 1.72:1.

Campy 10 shifters pull and average of 2.83mm per shift and the pulls are also not uniform. The RD move 4.15mm per shift.

The bottom line, is you can't mix any of the shifters and RDs.
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Old 06-21-10, 05:36 PM
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Hmm. Ya, I had a feeling it wouldn't be perfect. So then is it safe to assume that the 7800 down shifters or bar ends would be correctly compatible with the new 6700 derailleurs?
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Old 06-21-10, 08:23 PM
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DaveSSS,
Actually the SRAM Force moves 3mm for 3mm cable pull so that is a 1:1 ratio.

RobertKat, are you talking Shimano 7800 and Shimano 6700 RD? Then yes those should be compatible.

Again though. A J-Tek shiftmate would allow you to use the Shimano 7800 DT index and the SRAM Force RD. Click on the link I posted and follow it.
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Old 06-21-10, 08:45 PM
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^^^ Just looked at the Shiftmate. I knew about the other parts but had never seen the inline part you linked to. Many thanks. Just looking at options for shifting on a future build. I want to use Force but I'm looking at shifting options other than the brifters, should I decide not to use them or want something else in the future. 6700 is also being considered, is why I asked about it. I would use the 7800 down/bar end shifters as it looks like the 7900 does not have the optional friction mode on the rear. Thanks guys, this really helps.
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Old 06-22-10, 06:54 AM
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Originally Posted by canopus View Post
DaveSSS,
Actually the SRAM Force moves 3mm for 3mm cable pull so that is a 1:1 ratio.
I've got no clue what you're trying to say. What moves 3mm, other than the shift cable?

SRAM 10 has the same cog spacing as Shimano and that is 3.95mm. The RD must move 3.95mm for each cog shift, just like Shimano. SRAM 10 road shifters all use a uniform 3mm cable pull from the shifter to do it.

Even with a shiftmate to help correct the average cable pull from a mismatched shifter and RD, the results will not be great, since a SRAM shifter has uniform pulls and none of the other brands of RDs require a uniform pull. As an example, a shiftmate could change the SRAM cable pull from 3mm to 2.83, matching Campy's average, but it would still pull too much cable on each of the first 5 shifts, then too little on all of the rest. The same would be true with a Shimano RD.

Last edited by DaveSSS; 06-22-10 at 09:45 AM.
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