K2 / Proflex Riders Group
General => Tech Forum => Topic started by: fyrstormer on February 22, 2016, 02:40:29 pm
-
I bought some new bike parts today -- a Shimano Nexus 8-speed internal-gear hub, and two sets of front and rear roller-brakes. (apparently spare parts are hard to come by, and roller-brakes are engineered so all of the friction surfaces wear out at about the same time, so people generally just replace the entire brake assembly after years of use.) I'll get a front hub once I know what kind of interface the front roller-brake uses, and I'll get a shifter once I know whether or not the 8-speed hub kit I bought came with a shifter. (the listing was unclear.)
Why did I get comfort-bike parts? Well, I don't ride as hard as I used to, I already have two kick-ass mountain bikes, and I'll probably never buy a road bike because I just can't ride a bike with no suspension or off-road capability at all, so the experiment will be installing these parts on a mountain-bike frame. I'm thinking maybe a Santa Cruz Superlight, but I'll have to play it by ear once I see how the rear hub and rear roller-brake will mount to the frame. (the front roller brake has a disc-mount adaptor, which makes things much easier.) I've wanted to try this experiment for about 18 years now, ever since I first started shopping for upgrades for my Pro-Flex, and now seems like as good a time as any to start actually getting the parts I need. (specifically, getting the drivetrain and braking parts while I can still get a matching set -- the manufacturing world has a way of discontinuing pretty much every product I like, and I've been letting this idea simmer on the back burner for almost two decades, so it's time to make a move while I still can.)
Yes, it will be heavy. Oh well. My Pro-Flex weighs 30 pounds, so it's not like I won't know how to handle it.
-
Yes . parts are hard to find .
i'm looking for parts myself.
Nexus inter 7 sg 7c21 along with shifter .
need for pars and rebuild a set i have .
looking to build a cruiser myself
-
Yes . parts are hard to find .
i'm looking for parts myself.
Nexus inter 7 sg 7c21 along with shifter .
need for pars and rebuild a set i have .
looking to build a cruiser myself
Nexus 8-speed hubs are available on eBay for about $180. Some kits include shifters, brake levers, and a rear roller brake. My project is more complicated because I want to put a roller brake on the front, too, and Shimano seems to have discontinued roller-brake-compatible front hubs. I found some on a Dutch website called InternetBikes, but they only ship to Europe, so I got the help of someone here to buy a couple and ship them to me in the US.
Of course, if you're content to use a disc brake on the front, that isn't a problem, because Nexus 8-speed rear hubs are still widely available -- and if you want a disc brake on the rear too, you can get the Alfine 8-speed rear hub, which is compatible with Shimano Centerlock discs (or a 6-bolt adapter).
-
I use Alfine 8 with mixed results. First 2 hubs broke within 6 months each, 3rd hub seems to be better built and is slightly different - I think they made some changes ie. gears work the right way (thumb push ->1st gear, finger pull ->8th gear, originals were like rapid rise action) and it seems a little more durable.
Great when working! I like the lack of maintenance.
-
What kind of riding were you doing when you broke the Alfine 8 hubs? (they have the same internals as the Nexus 8 hubs, btw.)
-
The rear hub arrived today. It looks like it uses the Rapid-Rise shift pattern, where the cable is tightened to upshift. I suppose it doesn't really matter on a hub that can be shifted regardless of wheel rotation or drivetrain load, but it will take a little getting-used-to as far as tuning the shifter to work just-right.
-
General mountain biking - nothing particularly hardcore though as I run rigid.
-
Ah. Well, I guess we'll see how mine holds up over time. Once I drop the coin to actually build a bike for it, that is.
I was thinking about maybe converting my Pro-Flex to use this system, since I've got the Christini to handle off-road riding tough enough to benefit from AWD...but then the Pro-Flex wouldn't really be usable as a mountain bike anymore, since these hubs are really intended for road/path/singletrack use. Also, the Pro-Flex is pretty much perfectly dialed-in now, and I don't think I want to shake that up.
-
Put together the hub, brake, sprocket, and shifter today, just to test-fit everything and see if I need to buy any additional small parts. Man, that is one solid hunk of metal. Feels sturdy.
-
Hope it works out for you.
Just be gentle on the shifts, don't power through them like a derailleur, just slacken off slightly.
-
I don't power through shifts on my derailleur bikes either, so there shouldn't be much of a change in my riding habits.
In other news: UGH, the front roller brake I ordered has apparently been discontinued for EIGHT FREAKING YEARS, and the disc-caliper-tab adaptor it requires is basically impossible to find. None of the brakes I ordered came with one. So I have three front roller brakes and no way to mount them. Thanks, Shimano, for leaving information about a discontinued product on your website without any notification that it's discontinued.
-
It was just this comment that made me point out the reduced pressure when shifting, "I suppose it doesn't really matter on a hub that can be shifted regardless of wheel rotation or drivetrain load".
No luck on ebay for the parts you need?
-
I think I found a place in Germany that can sell me the parts I need. I'll have to wait until I open the box to confirm it actually contains what I need.
-
The brake parts showed up from Germany today. Just what I needed. Now I'm just waiting on a retaining nut and the roller-brake/internal-gear-hub assemblies will be complete.
Sadly they will then be promptly stuffed in a box until I have the money and space to build another bike. I've been busy blowing every spare cent on RC car stuff for the past couple years, so it will be a while before this project gets off the ground. At least I've got the parts that will be hard/impossible to find later on, though.
-
The core drivetrain components are complete.
(http://i5.photobucket.com/albums/y186/deusexaethera/bikes/DSC00417.jpg)
Special thanks to Colin for helping me get my hands on some parts that I couldn't have shipped directly to me in the US.
-
Wow that looks a cool piece kit!
Chris
-
Starting to look good, gonna be an interesting build.
-
God knows when I'll have the time, money, and space to actually build anything with these parts, but at least I have them now -- and spares. Oh man do I have spares. I've got another four of these brakes sitting in a pile, because that's what it took to get a complete set of mounting hardware. But as inexpensive as they were, it was worth it, because this particular version of the roller brake can mount to disc-brake tabs, which blows wide-open the possibilities for which frames I can use. Depending on how parts line up, I might be able to use the front brake on the rear hub too, which would let me take advantage of the disc-brake-mount approach on both wheels. I know front and rear disc-brake mounts are positioned slightly differently, but there's some adjustability in the mounting hardware for the roller brakes, so it might actually work.
All I gotta do now is convince myself to stop buying RC cars, move to another state, get settled down, and finish this build before having kids. God knows I won't have time for anything else after that.
-
Love the cooling(?) fins on the rear hub, glad I could play a small part in realising your aspirations!
Off to Cuba on Wednesday, I doubt I'll see any PRO~FLEX's there, just heavy Chinese clunkers!
Col.
-
Yep, both of the roller brakes have cooling fins on the wheel-facing side. Thanks again for your help getting the hubs.