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I have an old Stumpjumper from 1984. It has the original 3x5 drivetrain with friction shifting. I'm intrigued by the idea of converting to a 1x11 drivetrain, but I don't know what factors to consider regarding the feasibility of doing this. At least on paper, it looks ok since doing something like 36T x 10-42T would give me about the same range of gears I currently have. Is it even possible to do 1x11 on an old bike like this? How do I determine this?

Update: I should have pointed out that my frame has 126mm rear spacing. It is steel, so it can accommodate a standard 130mm road hub or be cold set to take a standard 135mm MTB hub.

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I did half of this - my late 80s 3x5 speed freewheel with nuts got upgraded to a 3x7 freehub with quick release, because the wheel was available. Turned out the freehub was actually 8 speed, so I could have gone as high as 3x8.

However its already hard to get the wheel into the frame - I don't think you'll fit a wheel and an 11 speed cassette in there.

Also the QR has to be checked after every ride. I've had the back wheel rotate slightly in the dropouts and it rubs on the chainstay, which means it moves at the power stroke. I did not cold-set the frame, so the dropouts are not parallel | | they are now slightly \ / which allows a little movement and eventually the QR comes loose enough to move. Depending on conditions this might be 10 to 100 km of riding to back off loose.

The rear thumb shifter will need to change, that's a given. I got away with using the same rear deraileuer mechanism and wire, but had to change the lever to a 7 speed indexed one.

You'll also need to change the chain. 5 speed chains are quite thick and may bind up in a 6/7/8 cassette.

Mine cost $50 for a cassette, $3 for some spacers, $40 for the thumb shifter, and another $40 for the new 6/7/8 speed chain. That was probably too much, but the freehub and chain needed doing anyway.

Summary this is probably not worth doing unless you get the replacement parts really cheap (ie free or almost free.)

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  • If the freehub was 8 speed, doesn't that mean you could have gone up to 10? I'm pretty sure 8, 9, and 10 use the same freehub size. – BSO rider Jan 1 '16 at 18:14
  • I didn't realise soon enough that the freehub was wide enough for 8 speed, plus the 7 speed cassette and the 7 speed indexed shifter were a lot cheaper than 8 speed ones. I also didn't need to change the front mech or chainrings, whereas 8-10 speed may have forced it. – Criggie Jan 1 '16 at 23:02
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I think those old bikes are 120mm spacing on the rear hub. To get 11 speeds back there you'll need to get 135mm spacing. You might be able to cold set that frame (bend the stays) but you risk cracking something so it's better to have a pro help with that.

If I'm wrong and it's already 135mm go for it.

EDIT - and yeah I would totally do it; sounds super-rad. Worst case scenario you don't like it - just move the 1x11 bits to something else.

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    Looks like it - "My biggest quandary right now is the rear wheel. It needs to be tough, and this frame presents an additional challenge in that it has super narrow 120mm rear spacing." from BikeForums I don't think spreading 15mm is particularly sensible, you're likely to stuff something up, if only by getting it a bit uneven. MTBR forums have a thread with lots of photos – Móż Dec 31 '15 at 5:38
  • My rear spacing is 126mm so each side would have to move 4.5mm to get to 135mm for an MTB freehub. Road spacing is 130mm which is only 2mm on each side. Could I use a road hub if MTB spacing is too much? – sam Dec 31 '15 at 15:19
  • You could use a road hub. But keep in mind that it's designed for lighter duty. – jqning Dec 31 '15 at 15:30

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