Nightshade

I've kicked around questions about internal geared hubs for
awhile now trying to figure out which is better.....for me.

What I'd like to do is convert a quality used bike from a
derailer system to a internal hub system or convert an old
3 speed to a newer 5,7,8,14 speed hub for two reasons.....

1.) COST of a new bike that would just be used as a utility
bike.

2.) try as I might I just can't get used to a derailer.

I'm considering used simply because my dollar will buy a
better quality bike (better frame, wheels,etc.) than if I
bought new for the money I've got to spend.

What my question here is can a internal hub be used with
a multi-ring front chain rings? Will the chain line up ok
in order to shift the front chain rings to get a 7speed to
work as a 14 (or 21) speed hub? I know that this will work
if you only use one chain ring and let the others just ride
along but could the other chain rings work this way???

Has this idea ever been tried before??

Spider

Since the different size chainrings would require different lengths in the chain, you would need some sort of chain tensioner to take up the slack when going to the smaller rings. I'm not sure how well this would work. If money is a concern, the 14 speed internal hub is probably way out of your price range. How many gears do you really need? I would just go with the Nexus 8 hub and one chainring that best suits your riding conditions.

DieselDan

An 8-speed Shimano Nexus rear hub, with a 34 tooth chainring, will work well for you. Just watch your rear dropout spacing, as an internal gear hub only uses 120mm spacing.

MichaelW

Use any chainring that gives you appropriate gearing but too small and you may over-torque the gearing.
Look for an old but good road frame with horizontal dropouts. The Shimano 8spd is a good option.

Nightshade

Yes, Thank you. I forgot about the need for a tensioner. I
think that Harris cylce sell a simple tensioner. Also I
know a Rolhoff 14 cost WAY more than I've got to invest but
I threw it in there as a example of internal hubs.

bbaker22

Internal gear hub spacing varies from hub to hub. My SRAM S7 hub is spaced at 130mm. The nexus
7 speed is either 127 or 130, depending on the brake type. If anyone has a source for the 8 speed
nexus (especially the premium version) in the US, I'd be interested in hearing about it.

I run one chainring up front, but see no reason that multiples couldn't be used with a tensioner (or a
derailleur acting as a tensioner).

baker

seely

Unless the tensioner magically develops the ability to move side to side, it won't work. The chainline will be off and the chain will come right off the tensioner. Remeber, tensioners hold chains in a STRAIGHT line.

Jonny B

Paul's Components do a chain tug that allows you to do this (or use a derailer with the spring taken out), but I'm not sure if it's such a good idea with a hub gear. Having said that Bromptons have hub gears and tensioners, but it's definately not possible if you have a coaster brake in there.

Dahon.Steve

Forget the chain tensioner because you're making it more difficult than it should. I would search Ebay (Sturmey Archer & frame). It's best to find a frame that was already made for Sturmey Archer because you'll find it very hard to convert a bike with verticle dropouts. In most cases, the frame will have to be stretched or the dropouts widened or extentions used to make up the difference. This can be a very time consuming and expensive project.

The other day, I found new frames on Ebay by searching "Shimano Nexus" that were designed for this hub. Look for Van Dessel frames on Ebay. These were designed for use with the Nexus 7

bbaker22

The chain isn't going to "come right off" a tensioner like the Paul Melvin anymore than the chain will "come right off" a rear derailleur. Even a tensioner such as the new Surly Singleator should have no problems retaining the chain with the chainline setup between the two front rings.

baker

seely

It won't work... I've used several different kinds of rear tensioners, and they don't work like a derailleur does. If the chainline isn't perfect you will experience skipping and chain drop. Why do you think singlespeeders go through such pains to get their chainlines perfect... if you post on any singlespeed forum about chain drop, first question invariably is, how is your chainline? Rear derailleurs allow for some movement side to side, and the lenght of the cage takes up some of the "play" (for lack of a better word... im tired) in the chainline. With a single pulley I would say its unreliable at best.

bbaker22

I'm quite familiar w/ singlespeed and fixed gear bikes and associated chainline issues. I currently have a fixed/free cross bike, two single speed mtn bikes, and an internally geared mtn bike.

The Paul Melvin is like a derailleur without the side to side movement capability. Two pulleys. It has worked for me on singlespeed and a 2 speed bike with two front chainrings. Same chainline setup as using 2 front chainrings with an internal hub.

Here is a direct quote from Paul's website:

"One of the coolest things about the Melvin is that it allows two front chain rings to be used (of course this is no longer a single speed, sob, but can be very handy for loaded commuting) Because we use two pulleys, two chain rings with a maximum difference of twenty teeth can be used up front. With a little practice, a deft finger and a delicate heel make a fine front derailleur."

Brad