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XTR v-brake levers with BB7's?

12K views 44 replies 20 participants last post by  Huusoku 
#1 ·
Would I be able to use my old XTR v-brake levers with BB7's? Just about to order up the BB7's, and the levers are cheap (FR-5's are $11), but would rather use the XTR if I can.

Also, another quick question - For my Monocog, I wouldn't need to go any bigger than 160mm rotors, right? I'm only at 160lbs and XC is all I do (bike is rigid).

Thanks for the help.
 
#4 ·
XTRs use Shimano's Servo Wave, which is sort of similar yet at the same time opposite of Avid's Speed Dial. I'm not sure exactly how this plays out in real use, but let me describe the differences:

Avid Speed Dial (not found on those $11 FR5 levers, by the way) allows you to increase the amount of cable pulled as you squeeze the lever to the bar. In the "weak" position, they pull around 20mm of cable, which is typical of many V brake levers. In the "strong" position, they pull about 27mm of cable.

Looking at this as a leverage problem, Strong and Weak seem to be reversed. The Weak position pulls less cable but provides more leverage, right? But operating the BB7 brakes isn't really a burdensome problem in need of a higher lever solution, so in fact the position with more cable pull provides more stopping power.

Shimano Servo Wave, on the other hand, continually adjusts the amount of cable pull as you squeeze the lever towards the handlebar. It starts out at high pull setting -- equivalent to Speed Dial's Strong position -- but gradually transitions into the Weak setting as the lever nears the bar.

The idea behind Servo Wave was that you could space your V brake pads a little further off the rim to allow for mud clearance or wheel out-of-true issues; that spacing would be eaten up quickly by the initial high-pull lever squeeze, but transition into a low-pull / high leverage position as the brakes were being applied.

Will the XTRs work with BB7s? Like mtnbiker72 said, yes, as will any V-brake lever.

What effect this has on the BB7 compared to Avid's very useful Speed Dial adjustment, I don't know. I'd like to try a pair of Servo Wave levers to see for myself. My guess is they're giving a little something up when you're braking the hardest, though there are a couple of variables in there that I'm not quite sure about (namely, the actual amount of lever travel used, and the total amount of cable pull of the lever).
 
#9 ·
I, too, had Servo Waves (XTs) and liked 'em just fine, but used them with V brakes not BB7s.

In this case the OP already has the XTRs, so naturally that's what he ought to install.

Just pointing out the differences between the two methodologies, and thinking out loud about it. I really should get my hands on a set to satisfy my curiosity.
 
#10 ·
That was an interesting bit of mechanical knowledge. I never knew what that Servo Wave thing actually meant. Seems like those levers could be a nice balance to the on/off feel some people complain about with BB7s.

To the OP.....I used a set of LX levers for quite a while with BB7s. Worked quite well back then.
 
#12 ·
Team Fubar Rider said:
The Servo-Wave function on XTR levers is adjustable, so you can crank the dial down and lock it out if you don't want to use it on the BB7's. When I used BB7's with XTR levers, I had a tiny bit of movement on the Servo-Wave. I don't think there was any mechanical advantage or disadvantage, I just liked the feel at the lever.
Good point, I had XT levers with V-brakes many years ago. It was adjustable via "blocks" which I removed as I preferred no servowave.

With the XTR, it's nice that you just dial the adjustment, something that would be interesting to play with.
 
#13 ·
mtnbiker72 said:
Good point, I had XT levers with V-brakes many years ago. It was adjustable via "blocks" which I removed as I preferred no servowave.

With the XTR, it's nice that you just dial the adjustment, something that would be interesting to play with.
Oh, that's right. I do remember those blocks. ('96 XTs)

Dials now? Pretty fancy. I'll have to take a peek. Do they do the same as the blocks, limit how far down the carrier travels in its channel?
 
#14 ·
Had to go look at my SD7 levers and XT/XTR levers after reading this thread, initially thinking they're almost identical in construction, but they're a bit different. The XTR is similar to the XT in that without a pitch block and/or the pitch adjusting screw (three pitch blocks on the XT, one pitch block plus adjustable screw on the XTR) adjusted clockwise, the pivoted piece the cable attaches to is unsupported at the bottom, whereas that piece on the SD7 is supported from the bottom and held firmly in position no matter where you adjust the speed dial. It seems the Servo Wave effect is from allowing that piece to slide up in it's slot as the lever is pulled. Wish I had better terminology...sounds so much better the way Speedub is describing it.
 
#17 ·
Speedub.Nate said:
Avid Speed Dial (not found on those $11 FR5 levers, by the way) allows you to increase the amount of cable pulled as you squeeze the lever to the bar. In the "weak" position, they pull around 20mm of cable, which is typical of many V brake levers. In the "strong" position, they pull about 27mm of cable.
Hmm, I just woke up, but this seems backwards. If you turn the Speed Dial knob all the way clockwise, so that cable hanger is as far from the lever pivot as possible...wouldn't that be the "weakest" setting?

I'm using XTR levers with one set of BBDB's, and Avid SD's with BB7's. The XTR's are set up in such a way that the Servo-wave action never really kicks in. (Pads are as close to the rotor as possible, and cable tension is as tight as possible, without rubbing)

Both levers work great.
 
#19 ·
kramnnim said:
...this seems backwards. If you turn the Speed Dial knob all the way clockwise, so that cable hanger is as far from the lever pivot as possible...wouldn't that be the "weakest" setting?
Yes, your reasoning makes sense and how I initially thought they should work (simple leverage).

But in practice, it worked the opposite way, where reduced mechanical advantage resulted in stronger braking.

Then Avid confirmed it with this little ditty somewhere in their instructions:



So my rationalization is this: the brakes already have so much mechanical advantage (amount of finger movement needed to move the brake pad a scant 2mm or so), that this 33% change in cable pull won't have much of an impact to operability for a rider with an average strength hand.

In theory, the increased cable pull would allow the pads to move 33% further. In reality, they have nowhere to go. Instead, the extra cable pull is allowing us to snug up any slop, stretch or other inefficiencies in the cable, housing & bearings, and increasing the rotor clamping force.
 
#20 ·
i disagree. from sheldon browns site

"Feel" vs. Function

With automobile brakes, a nice "hard" pedal feel is a sign that the brakes are in good condition. A soft, "spongy" feel at the brake pedal is a sign of trouble, perhaps air in the hydraulic lines. This is not the case with bicycle brakes. A hard, crisp feel to the brakes on a bicycle may be a sign that the brakes don't have much mechanical advantage. You squeeze them until the brake shoes hit the rim, then they stop. Brakes with a high mechanical advantage will feel "spongy" by comparison, because the large amount of force they deliver to the brake shoes will squash the shoes against the rim, deforming them temporarily under pressure. You can feel this deformation in your fingers. The brakes with the rock-hard feel may seem nice on the work stand or the showroom floor, but when it comes to making the bike actually stop, the spongy set-up will do the job better, with less finger pressure and greater margin for safety in wet conditions.
 
#21 ·
reptilezs said:
i disagree. from sheldon browns site...
I'm not sure with what or whom you are disagreeing, but I don't think Sheldon't comments you quoted are necessarily applicable to this thread.

However, with respect to Avid BB7s:

- very close-in pad spacing will have a very "hard" feel at the level, and on-off performance that isn't very desirable out on the trail.
- spacing the inboard pad further away will cause the outboard pad to flex the rotor over before full braking can be achieved. This provides better feedback to the rider and is an effective way to control BB7 modulation.
- sloppy housing preparation and cable setup can increase the amount of give, even with the pads set in close. This doesn't do any good for the rider.
- with hydro systems, the modulation is usually non-adjustable and is engineered into the brake
- Sheldon made reference to "rim" and "shoes" in his comments. Maybe not exactly applicable to a discussion of discs, or hydro discs in particular? There's no denying that cable systems have a certain amount of inherent play or give that isn't a factor in hydraulic systems.
 
#22 ·
just pointing out the talk about firmer lever feel and mechanical advantage. yes moving the speed dial further away will give a firmer feel. it also reduces mechanical advantage. what is desirable on trail is subjective. i like as much power as i can get. sheldon's argument is applicable to all cable systems. even hydro systems, as he compares a cars brakes. one should have a firm lever with a hyrdo brake.
 
#23 ·
Right, I agree, but it's all relative.

Even with the Speed Dial all the way out -- yes, you're right, it's firmer than when all the way in -- that's not the end of the story. The bigger factor in firmness still remains the inboard pad adjustment.

Relative in terms of Sheldon's comments with respect to rim brakes vs. cable discs, too. Rim brakes have "acceptable slop" in big rubber pads and rim deflection; cable discs have almost none. The cable stretch and housing compression are common elements. I expect the cable disc setup to feel firmer than a well-adjusted rim brake setup.
 
#24 ·
In reference to the illustration from the Avid .pdf...are you saying that the "softer" position is also weaker?

When I used the levers with rim brakes, the opposite seemed true.

Haven't messed with them now that they're connected to the BB7's, but it doesn't seem like it would change anything.
 
#25 ·
kramnnim said:
In reference to the illustration from the Avid .pdf...are you saying that the "softer" position is also weaker?
That's what they're saying. And I guess following that logic (that less pull = greater mechanical advantage = weaker) follows that you don't want to use road levers with V brakes.
 
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