Old 12-11-15, 03:31 AM
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Andy_K 
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The Definitive (But Wildly Inaccurate) Guide to Brake Cable Pull Ratios

Background: I'm a nerd. Shimano likes to take a very narrow view of compatibility between components. Those two things combined led to this post.

It's generally well known that Shimano has been tweaking their brake cable pull over the past few generations of their road components, but the details are very hard to come by. If you search the product specifications on the Shimano website you can find out which trademarks are associated with which components. They have "SLR-EV" (DuraAce 9000/Ultegra 6800/105 5800/Tiagra 4700), "New Super SLR" (7900/6700/5700/4600) and "Super SLR" (7800/6600/5600/4500). At some point there was also plain old "SLR" but I don't know where that cutover took place. Shimano vaguely claims that each of these is incompatible with the others, though much anecdotal evidence suggestions that's not entirely true.

From various sources (mostly discussion posts on this forum and others) I've gathered that the "New Super SLR" levers pulled slightly more cable than the "Super SLR" while the "SLR EV" pulls (roughly?) the same amount of cable as the "New Super SLR" but tweaks the rate at which the pull is changed throughout the cable pull.

All of this is perhaps interesting to extreme bike nerds but mostly not very helpful without some numbers to go with it.

In another thread (http://www.bikeforums.net/bicycle-me...l#post18380942) @andr0id reported as follows:

Originally Posted by andr0id View Post
I just set up my fixed gear bike with Ultegra 6800 brakes (the new SLR-EV) and the Cane Creek V brake levers.

The feel of the brakes is the same as my geared bike with the ST-6800 levers.

I measured the pull of a "full squeeze" on the following levers and found the following:

ST-6800 SLR-EV (5800, 6800, 9000) = 15.5mm
Dura Ace 7402 Brake lever (SLR) = 13mm
Can Creek V Brake lever = 16mm

I originally tried the 7402 levers but was not satisfied with the feel or pull with the 6800 brakes which led me to try the Cane Creeks.
So I took some measurements of my own....

Let me preface by saying that I am absolutely terrible at taking precise measurements. On top of that, I was using linear measurements as an estimate of lever travel that is actually an arc and picking a more or less arbitrary point on the lever at which to measure the travel (though I tried to be consistent from lever to lever). Finally, it's my understanding that the rate of cable pull actually changes throughout a full sweep and for practical reasons I measured different amounts of pull with different levers.

Nevertheless, I think the data I came up with shows a reasonable resemblance to meaningfulness.

It turns out I've got a lot of brake levers in my garage. Half of these weren't actually on bikes, so I just mounted them to a spare set of bars. For each lever I tried to measure how far the part of the lever where I'd usually be applying pressure moves, and then I measured how much cable moved during that pull (measured in various ways, depending on how the lever was mounted). Here's what I came up with:

Lever
  • Lever travel (mm)
  • Cable pulled (mm)
  • Ratio
  • MA
Gevenalle CXV0 (= Tektro RL520/Cane Creek Drop V)
  • 40
  • 24
  • 0.60
  • 1.67
Gevenalle CX2 (= Tektro 200A/Cane Creek SCR-5)
  • 39
  • 15
  • 0.38
  • 2.60
6700-series Ultegra (New Super SLR)
  • 27
  • 12
  • 0.44
  • 2.25
5700-series 105 (New Super SLR)
  • 26
  • 11
  • 0.42
  • 2.36
4600-series Tiagra (New Super SLR)
  • 17
  • 7
  • 0.41
  • 2.43
Non-group R700 (Old Super SLR)
  • 27
  • 10
  • 0.37
  • 2.70
5600-series 105 (Old Super SLR)
  • 28
  • 10
  • 0.36
  • 2.80
6500-series Ultegra (SLR?/Old Super SLR?)
  • 36
  • 11
  • 0.31
  • 3.27
SRAM S500
  • 43
  • 17
  • 0.40
  • 2.53
Avid SpeedDial (flat bar, MTB)
  • 43
  • 32
  • 0.74
  • 1.34
Avid SpeedDial (flat bar, MTB)
  • 43
  • 25
  • 0.58
  • 1.72
The pull on the Avid Speed Dial levers is adjustable, so I measured once at each extreme.

I would guess that my margin of error on these measurements might be as much as plus or minus one millimeter, but I think you can see the trend lines. It looks to me like the cable pull ratio for long pull levers is around 0.6, the pull ratio for the old "Super SLR" levers is about 0.38 and the pull ratio for "New Super SLR" levers is about 0.42.

Prior to the introduction of "New Super SLR" everyone seemed to lump all "short pull" levers together, and so I have always kind of assumed that they all had about the same cable pull ratio. Within my generous margin of error, it looks like the SRAM levers and the short pull Gevenalle levers I measured are around the same pull as the old Shimano "Super SLR" levers, so that seems to be consistent with my expectations. The SRAM levers might actually slot in somewhere between new and old Super SLR, but my measurements weren't precise enough to say for sure.

I don't know where the 6500-series Ultegra levers fit in all of this. Just looking at them I expected them to be in the "Super SLR" camp, but my measurements didn't back that up.

I'd love to see someone who is more skilled as precision measurements than I am repeat this experiment.

EDIT: See post 18 in this thread for what I consider to be more reliable data.
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Last edited by Andy_K; 02-06-17 at 07:09 PM. Reason: Converted table data to list format
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