zeppinger

Hi all,

I'm a year round cyclist here in Michigan and just ran across a nexus 7 speed internally geared hub with a coast break laced into a nice 26 inch Weinmann hub. This would make an ideal setup for a year round commuter bike. My current commuter is a 1990s Specialized Hardrock that I am pretty happy with but wanted to hear ideas on other kinds of frames I might consider using. The thing I like the least about the current bike is the dumb Ubrake under the chainstays which could just be removed since the new hub has a coaster. Would I have any other problems building this hub into my current bike? I do not have the control mechanism for the hub so would have to buy one. Any recommendations? The model number on the hub is SG-7c21 if that helps anyone. Thanks in advance!

-Zep

wolfchild

You need a frame with horizontal drop-outs so you can slide the wheel back or forward to adjust chain tension. I don't think a hub with coaster brake will work on a bike with vertical drop-outs.

zeppinger

I was planning to use an old Surly Singlator to tension the chain. I know this will slightly decrease the efficiency of the already somewhat inefficient hub but dont mind all that much. Will the vertical drop outs be a problem for the hub brake? If so, why?

wolfchild

Chain tensioner won't work with coaster brake, just like it wouldn't work with FG drivetrain. That's why you can't use vertical dropouts if you want to run a coaster brake hub. You need a frame with horizontal drop outs, or sliding drop outs or rear track ends.

AlmostTrick

Just try it, you may get lucky. A half chainlink and/or trying different chainring/rear cog configurations may get you there. Here's a coaster brake I made work in a frame with vertical drop outs. Chain tension is perfect.

wolfchild

That set up is temporary and will only work for a few short rides before the chain stretches and becomes loose....What happens when the chain stretches and becomes too loose after few hundered miles and need to be re-tensioned ??...It very dangerous to ride with loose chain when the drivetrain is used as a primary brake.

zeppinger

I agree. I would rather have something more permanent. Can anyone recommend some frames that I might be able to find easily on the used market or frames that I can buy cheaply new? I used to have a 70s Raleigh Sports that was a great, if slow, bike. If I could find another one of them I think it might work pretty well.

AlmostTrick

You know wolf, I always wondered about that, and you may be right. I've only put a few hundred miles on that bike, certainly less than 1000.

But even with those dropouts there is still some room to move the axle forward and back... they're not completely vertical. It would be easy enough to just monitor chain tension over the months and see.

wolfchild

Chain tension is perfect ??..But for how long and how many miles ??...Magic gear ratio is not as magic as some people make it to be. If magic gear were so great then there would be no need for FG bikes to use rear track ends or horizontal drop outs. Why not just get a proper frame and do the job right ??.

fietsbob

Missing relevant data. rear dropout spread Vs the width of the hub you want to fit. I dont see it if you dont write it.

then theres the whole chainline measurement and crank choice or modification.

zeppinger

Since it seems like we have established that the current frame would be less than ideal to use with this hub, do you still want me to measure the width of the hub? Are all nexus hubs pretty standard? What kinds of frames should I look for to build this hub into? Thanks!

fietsbob

me? Meh.

just nobody posts that stuff in the 1st place like it doesn't matter.

you got the hub? if not look it up on Shimanos product Tech downloads

Hub overlock nut spacng within say 5mm minus , maybe 3 mm Plus for the frame


the Drum brakes being cable operated you can use a chain tensioner and a Vertical dropout frame .

coaster brakes .. a frame like you'd pick for Fixie conversions ... since the pedal back pressure is what stops the forward Momentum


My foul est weather Bike has a 7 speed freewheel drum brake rear hub, and a Drum brake front hub, on an old MTB Bike.
now in it's 20th year like that..

zeppinger

I think its 167mm but I am not sure. Here is the manual online but I am honestly not sure what I am looking for...

:-/

Thanks in advance! file:///Users/EddieAir/Downloads/EV-SG-7C20-1266E.pdf

fietsbob

167 sounds lie the whole axle including the parts past the outside of the frame the Nuts thread down onto.

Velorbis.com hosts an overhaul How to and hub parts breakdown on Pg 10 & 11. PDF

https://www.google.com/search?q=Nexus+7+speed+coaster+brake+hub&oq=Nexus+7+speed+coaster+brake+hub&aqs=chrome.0.57&sourceid =chrome&ie=UTF-8

google used "Nexus 7 speed coaster brake hub"

I-Like-To-Bike

This frame works great with a Nexus 7 speed internally geared hub with a coaster brake.

hueyhoolihan

in the late '90's i ran a Nexus 7 (coaster brake) on a bike with vertical dropouts and 130mm OLD. i filed the dropouts about 1/16-1/8" to accommodate chain tension. it was not a problem. chain stretch was not an issue either. a 1/8" Sram Pc-1 chain, which may be an option, chain-wise, is a monster and takes many more miles to wear than one of those gurly 3/32" 10-11 speed chains.

IME, people run their chains way to tight, they can sag quite a bit and still not derail if the chain-line is good and they develop the good single speed habit of soft-pedaling over rough terrain. this, IME, becomes a natural tendency after a while.

i'm not sure, but it looks like that bike might have short horizontal dropouts. in which case you are golden.

BTW, i sold my Nexus 7 at a bike swap in San Francisco in '98, without the shifter. it worked well while i had it.

cobrabyte

Fuzzy dice? How twee of you.

wolfchild

Surly Cross Check.

AlmostTrick

I recant my "you may be right".

After going back and inspecting the set up on my Raleigh Wyoming coaster brake, (it's been several years since I built it up) there is more than enough adjustability in the semi vertical drop out to compensate for a normal amount of chain stretch.

I post this not for the OP, who has decided a new frame is what he wants or needs, but for those readers who may not want to buy a new frame when the one they have may work just fine.

It seems at least one expert backs up my assertion:

Sheldon on Singlespeed Bicycle Conversions

wolfchild

Of course, anything can be "improvised and made to fit", but it doesn't mean that it's an ideal long term solution. I would still argue that the best thing to do is to use a proper frame. Do it right the first time.

kickstart

Not all "vertical" dropouts are alike, a 7 speed coaster works fine in my old Ross MTB..........and the Schwinn phantom I stole the wheel from that came as OE on that bike.

zeppinger

If I am going to try to find and build a new bike for this hub I want it to have similar ride characteristics as my Rockhopper. Something that can do just about everything well. 26 inch wheels so I can use my fat studded winter tires in the cold but also 1.5 slicks in the summer. No suspension. Are there any frames with the horizontal drop outs that are made of aluminum? That would help prevent rust in the winter with salted roads.

zeppinger

Thats a sweet bike ILTB but unfortunately, not quite my style.

DiegoFrogs

There were a lot of good 26" wheeled mountain bikes in the 1980's, most of which have horizontal dropouts.

After I changed the rear tire on my 7-speed IGH (SG 7C-21) coaster-braked horizontal dropout city bike which reportedly had a new chain, and rode it about 1,500 miles over the last 10 months, it needs... no adjustment.

With a BMX chain and one of those new-fangled half links, you should be able to position the axle with 1/16" increments in the dropouts. And you have a good front brake. And you can even leave on your excellent rear brake until you either decide that you want to remove it, or whatever.

To be honest, I wish my bike didn't have the coaster brake and instead had studs for cantilevers or V-brakes as in the front. But that's the style here in Scandinavia.

zeppinger

What dont you like about the coaster brake? I havent had a bike with one in years but I hear they are good in the winter because they dont freeze solid and are good even when wet.