Replacing rear wheel with 7 speed gear hub
July 4, 2019 3:01 AM Subscribe
I am driving a 30 year old Triumph bike that is in OK shape, but the ball bearings of the rear wheel are shot, and the whole gear hub is not repairable, says my mechanic. Replacing everything would cost about 200€ plus the price for installation.
That far exceeds the bikes worth, and I would like do do it cheaper and myself, but I have very limited knowlege about bike repair.
I'm thinking to replace the 7 speed gear hub wheel with this:
28 Inch Rear Wheel Rmx Alloy Double Wall Rim with Eyelets with Shimano 3 Speed Gear Hub
and install that:
Revo Shift Shimano Nexus SL-3 S35 für 3-Gang Nabe, mit Zug und Clickbox
At first glance this doesn't seem complicated at all, just switch the complete wheel and install the new shift system, which would cost about 90€. Is it as simple as that, or what do I have to consider?
I'm thinking to replace the 7 speed gear hub wheel with this:
28 Inch Rear Wheel Rmx Alloy Double Wall Rim with Eyelets with Shimano 3 Speed Gear Hub
and install that:
Revo Shift Shimano Nexus SL-3 S35 für 3-Gang Nabe, mit Zug und Clickbox
At first glance this doesn't seem complicated at all, just switch the complete wheel and install the new shift system, which would cost about 90€. Is it as simple as that, or what do I have to consider?
One thing you should check before you begin: are the dropouts of your bicycle frame horizontal? On a bicycle equipped with a rear derailleur, the derailleur regulates the chain tension; after you remove it, the only way to regulate the chain tension is to move the wheel slightly forward or backward, or to install a separate chain tensioner. A chain that is too tight will not go all the way around the gears; a chain that is too loose will tend to jump off the gears when you hit a bump. So, if your frame has vertical dropouts (which don't allow you to move the wheel backward or forward), you will need a tensioner. This article on fixed gear conversions covers this idea -- you can ignore the big warning about not using a chain tensioner, because you aren't converting to a fixed gear hub.
Provided that your frame is compatible (including the OLD that deadwax mentioned -- this is also important) I think this should be pretty doable. The shifting system for the internally geared hub is quite simple, although getting the shift points of the hub to line up with the indexing (the "clicks") of the grip shifter may require some patience, and is also the part you are most likely have to adjust again down the road.
posted by egregious theorem at 6:36 AM on July 4, 2019
Provided that your frame is compatible (including the OLD that deadwax mentioned -- this is also important) I think this should be pretty doable. The shifting system for the internally geared hub is quite simple, although getting the shift points of the hub to line up with the indexing (the "clicks") of the grip shifter may require some patience, and is also the part you are most likely have to adjust again down the road.
posted by egregious theorem at 6:36 AM on July 4, 2019
I did this a few years ago, and it was relatively easy. I added cable stops from Origin8 to my frame for cable routing. I connected a short length of brake cable housing between the rear derailleur cable stop and the internal hub, because brake housing is more flexible than shifter cable housing and works well for short runs. Fixing rear wheel flats can be a pain because you can’t just unloop the chain; on my 8-speed Nexus hub this involves detaching a greasy ring that’s hard to do without a bicycle stand.
posted by migurski at 10:24 AM on July 4, 2019
posted by migurski at 10:24 AM on July 4, 2019
Here's Sheldon Brown on frame spread so you can figure out if this is the right hub. If it's close, you (meaning a trained and confident mechanic) can probably properly bend the frame to fit. Call around if that looks like it's the case.
posted by rhizome at 1:21 PM on July 4, 2019
posted by rhizome at 1:21 PM on July 4, 2019
And if mechanics are leery of spreading a 30 year old frame, find a bike coop. They do that sort of thing all the time.
Your plan is sound. As long as the wheel fits in the dropouts, the shifter pulls the right amount of cable, and you have a way to tension the chain, you're good.
If cable stops aren't looking like they will work, try just doing full length housing. It's simpler and you can zip tie or wire it to the frame anywhere you like.
posted by Acari at 2:08 PM on July 4, 2019 [1 favorite]
Your plan is sound. As long as the wheel fits in the dropouts, the shifter pulls the right amount of cable, and you have a way to tension the chain, you're good.
If cable stops aren't looking like they will work, try just doing full length housing. It's simpler and you can zip tie or wire it to the frame anywhere you like.
posted by Acari at 2:08 PM on July 4, 2019 [1 favorite]
Ah, I assumed by 7 speed gear hub you meant internal gears, not derailleur gears. A 30 year old 7 speed bike in that case will have an OLD of somewhere between 126mm and 135mm, probably. As opposed to the 120mm on the wheel you want to put in. You may also have some fun getting the chain to run in a straight line (called chain line) and need to muck around with your cranks/chainring(s).
Doing all that from no knowledge would be a very big call.
But if what you have is 7 derailleur gears on the back a €200 repair cost is insanely high - go somewhere else. Or perhaps go to a bike coop if you can, a second hand wheel should be maybe an eighth of that.
posted by deadwax at 2:28 PM on July 4, 2019 [1 favorite]
Doing all that from no knowledge would be a very big call.
But if what you have is 7 derailleur gears on the back a €200 repair cost is insanely high - go somewhere else. Or perhaps go to a bike coop if you can, a second hand wheel should be maybe an eighth of that.
posted by deadwax at 2:28 PM on July 4, 2019 [1 favorite]
I think this is possible, but personally I would shop around and see if you can find a different mechanic more interested in the job, or the aforementioned bike co-op, or even a friend who's a good wrench with bicycles to help. Only because you could, if you do something poorly, either end up stranded with a broken bike or (less likely but still possible) have a catastrophic failure. (This isn't too much of a problem if you aren't actually relacing the wheel, and it's more an issue with front-wheel stuff anyway, but if you aren't comfortable working on bikes I'd at least want someone experienced to look over your work.)
A bike shop that caters to "fixie" riders might be more interested in taking on the project and more familiar with dereilleur conversions in general, than your average local shop.
posted by Kadin2048 at 3:23 PM on July 4, 2019
A bike shop that caters to "fixie" riders might be more interested in taking on the project and more familiar with dereilleur conversions in general, than your average local shop.
posted by Kadin2048 at 3:23 PM on July 4, 2019
As mentioned above, the width of the existing wheel (the space between the frame dropouts) is the big key. All 7-speed road systems I've ever seen use 126 mm dropout spacing. YMMV. If your new wheel also uses 126 mm spacing (which basically means: 6- or 7-speed only or a wheel designed to replace that*), you're 75% of the way there. Beyond that, it's making sure you have a way to mount the shifter, derailleur, and appropriate pulling bits.
(* it is possible to adapt many narrower wheels, like that 120 mm you linked, to a slightly wider frame like your probably-126 mm, by using spacers. For traditional threaded axles and derailleurs, it's generally easy. For internal-gear hubs like you've listed, sometimes you can only add spacers on one side: in those cases you have to re-dish the wheel so it isn't off-center in the frame.)
posted by introp at 8:06 PM on July 5, 2019
(* it is possible to adapt many narrower wheels, like that 120 mm you linked, to a slightly wider frame like your probably-126 mm, by using spacers. For traditional threaded axles and derailleurs, it's generally easy. For internal-gear hubs like you've listed, sometimes you can only add spacers on one side: in those cases you have to re-dish the wheel so it isn't off-center in the frame.)
posted by introp at 8:06 PM on July 5, 2019
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Apart from that, you are potentially generally correct, it may be as simple as you think.
Things you need to make sure of:
-Is the between the frame bit (the OLD) of the old axle the same length as that on the new wheel. The new wheel appears to be 120mm, you can measure on the existing one.
-Is the method of pulling the cable to change gear on the new wheel compatible with the cable routing on your frame? Or are you going to need a cable stop where you don't have one?
-Setting up and adjusting gears can be finicky, do you have someone to turn to for help, or are you mechanically quite proficient?
-Terminating the cable will require at least a tool to cut it, consider extra expenses like this if you will need to buy tools. (A small secret: you do not require a bike specific tool to cut cables and housing, just get cutters for wire rope from your local hardware store, often for less money.)
posted by deadwax at 4:29 AM on July 4, 2019