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The Nexus front brake on my commuter has gone soft, and I can't figure out if it's just the cable has slipped and moved the bite point (there's a really strong return spring so you can't really feel a defined bite point like disk or rim brakes), the shoes have worn, or something else. My first thought actually was that the cable outer had split, but I've checked it and the actuator lever moves proportionally to the lever so it's not that and the cable doesn't look like it's slipped.
It's not squealing so it's not a lack of grease on the shoes or overheating.
Like most shimano stuff it's a £17 sealed unit that's replaced as a whole, so unless someone says it's ............... then I'm loath to take it apart and end up without a commuter because some fiddly spring or clip has pinged off to the other end of the workshop.
Is it not one of the ones you can grease with Nexus roller brake grease?
What happens if you take up slack in the cable?
It's almost certainly needing new grease.
There's bugger all to wear out unless you've been running it dry.
The grease facilitates the easy movement of the rollers into a jamming position and then lubricates the contact surfaces so they don't wear out - that's my understanding of it.
Here's one I disassembled and rebuilt (there's a few more pics of it in that album).
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I wouldn't bother trying that again. I took it apart because I thought something was worn out, but it just needed a clean and new grease. Also getting it back together needs more limbs than an octopus. 🙂
Shame they can't make them a bit lighter.
I thought they squealed if the grease was running dry?
Its just gone from barely any movement to the bite point to pulling to the bar with little effect. My only other thought other than some catastrophic* hidden internal failure is the cable was installed incorrectly wedged on the edge of a ferrule/cable stop and has just jumped into the correct place.
*a shoes fallen out or the 'power modulator'/clutch in the hub is just slipping. Dont know if the hub has the latter.
I remember stories of the Shimano sponsored DH team running roller brakes in the late 90s just before Shimano brought out their first set of disc brakes.
I have nothing useful to add though, sorry.
thisisnotaspoon
...or the ‘power modulator’/clutch in the hub is just slipping. Dont know if the hub has the latter.
I haven't seen one in the hub (but my knowledge isn't current), and they used to be available inline on front brake cables. I think their purpose was as an anti-lock device to limit the amount of force you could transmit through the cable.
I've never used a ‘power modulator’, and would ditch it if it was on my bike, but that's a personal decision.
I’ve never used a ‘power modulator’, and would ditch it if it was on my bike, but that’s a personal decision.
I agree, and that's what I thought, they had something similar for V-brakes. But the diagrams for some versions of the nexus hub seem to show the entire brake mount is able to rotate within the hub if the brake locks up. Whole thing seems daft, if I'm braking hard enough to lock up, I probably want to brake hard, and unlike ABS it doesnt allow for wet roads, leaves etc so it won't work when you need it anyway!
The brake is aimed at the non-enthusiast commuter market, and there is the persistent belief in that segment that any use of the front brake will catapult you over the bars.
Which is a shame because with some more development it could be made much lighter and be a brake that lasted the life of the bike. But the industry and Shimano does prefer to sell consumable parts for your bike.
Edit: The power modulator is built into the front hub.
I should know this, I have one. And the reason I never built it into a wheel was because I didn't want the modulation (ie soggy brake feel). I might pull it apart now you've re-awakened my interest. 🙂
Figured out what was happening, the cable was indeed slipping/creeping through the bolt, but because it had pulled through the lull length of the adjusters over the course of 500 miles (almost an inch) it just looked like the usual grubby slightly frayed cable rather than obviously slipped.
I should know this, I have one. And the reason I never built it into a wheel was because I didn’t want the modulation (ie soggy brake feel). I might pull it apart now you’ve re-awakened my interest. 🙂
I'd be interested to try it mounted to a conventional hub and see if it makes a difference.
The whole brake is only on a par really with wet rim brakes. which given the upright riding position and narrow range of gears is fine as you would struggle to top 15mph even downhill. You don't have the problem of a car stopping suddenly in front of you, because a car is never in front of you, it's either behind, overtaking, or miles ahead!
Might mark the heatsink and hub with a sharpie and see if it actually does 'modulate' under hard braking.
I agree, and that’s what I thought, they had something similar for V-brakes.
They did, when I swapped the HoD cantis for V-brakes it came with one. Made the front brake really spongy, so was soon ditched. Built into the noodle IIRC.
There’s more than you could ever want to know about roller brakes on the CTC Cycling UK forum.
thisisnotaspoon
The whole brake is only on a par really with wet rim brakes.
It should be much better than that. Maybe you need a better cable outer.
EDIT: unless it's one of the tiny ones.