Nexus 3-speed coaster: spring?

[ParkRNDL]

I robbed a Nexus 3-speed coaster off a girls' Trek cruiser and set it up on my old Hornet. I really like it: it shifts smooth, it's quiet, it works great... and the brakes are like no other coaster I've ever ridden.

Usually on coaster brakes, there's a few degrees of backpedal, then the shoes contact the hub shell, and then there's no further discernible backwards movement--it's just how hard you lean on the pedal till you lock it up. With this Nexus, though, there's the few degrees back, then the shoes make contact, and then there's another couple degrees of travel that you can use to modulate how hard you're braking. It feels like the brake pedal in a car, where there's a certain amount of pedal travel that gets increasingly harder between the point that the brake lights come on and a full panic stop. On the bike, it's all done in an inch or less of rotation at the pedal, but you can definitely sense movement and feel that you're applying the brakes harder.

How do they do that? Is the brake arm on a Nexus hub attached through a spring?

 

[horsefarmer]

A friend let me take his Bianchi for a test hop and believe it had the same set up. I think it is a separate band brake. Sure works wonderful!

 

[MattiThundrrr]

Modulate? A coaster?! This is very interesting. Can anyone confirm or deny wether this is true of all the Nexus hubs?

 

[Klunkruiser]

My lightly used Nexus-4 works like that. But the Nexus-3 that I have has seen far more use and pressure seems lighter and is quicker to lock up.

 

[us56456712]

It works just as good with a 28 to 30 tooth chainwheel, almost no back pedal until the brakes catch.

 

[ParkRNDL]

Yeah, I wondered how gearing affected all this.

The Trek donor bike was geared 32/18, which was REALLY low. I like low gearing, but that's too low for me. The brake feel, however, was amazing with that gearing.

When I put that wheel on the Hornet with a 46t front sprocket, I noticed the brakes lost a good bit of their sensitivity. I decided that 46/18 was geared too high overall, so I changed the rear cog to a 20t. Now the gearing is more in the range where I like it, and as a side benefit the brakes feel more like they did on the Trek.

It never would have occurred to me, but I guess logically it makes sense. When you are geared higher, you move the pedals a shorter distance to go farther. It follows, then, that when you move the pedals backwards a short distance the brakes take up faster and with less "feel".

 

[clamdigger]

I think that you would savor the wide range brake modulation, and brute strength of the Bendix Automatic Red Band 2 speed kickback. I run one on my Roadster , 18 T cog , 26" wheel w/big tire. The chainwheel is around 44 or 46 T .

 

[ParkRNDL]

I think that you would savor the wide range brake modulation, and brute strength of the Bendix Automatic Red Band 2 speed kickback. I run one on my Roadster , 18 T cog , 26" wheel w/big tire. The chainwheel is around 44 or 46 T .

I actually have a Bendix 2-speed on this bike. I DO love it. At the moment I am working up the courage to rebuild the 2-speed as a winter project, as it squeals really bad on braking.

 

[Starnger]

I can confirm that. I run Nexus 3 on many of my bikes, and Nexus 8 with coaster on few more of them. Modulation of the brakes is quite good, good enough in fact to allow me to comfortably use it as the only brake on some of my bikes.
There is in fact a spring going over the braking pads on Nexus (3, 7 or 8 gears, all coaster mechanisms are similar on them), i have disassembled and repaired those hubs many times, but i did not study the mechanics of those hubs close enough to be sure, that this spring is actually responsible for the described effect. It could be as well some other element.

 

[horsefarmer]

I have not taken mine apart, but found a couple pics showing mechanism.

actuator...