1984 Stumpjumper wants to be 1x11 but doesn't know how

I have a 1984 Stumpjumper Sport which I'd like to convert to 1x11. I am a bike maintenance neophyte and I'm trying to get my arms around what is involved.

The bike currently has the stock 3x5 setup: 46/36/26t in front and 13-30t out back. This setup gives me a high gear ratio of 46/13=3.54 and a low of 26/30=0.87. A 1x11 with a 36 tooth chainring and 10-42t cassette gives a high gear ratio of 36/10=3.6 and a low of 36/42=0.86. So it looks like the range I'd get is about the same as what I have. Am I understanding the gearing properly?

I believe I will need new wheels (with freehub rather than freewheel), shifter, narrow-wide chainring, chain, rear clutch derailleur, and 10 or 11 cog cassette. Will I need new cranks? Bottom bracket?

I'm hoping to source some of the parts from eBay or craigslist. For example, there are lots of wheelsets online. Are wheelsets interchangeable, or do I need to take certain things into account for compatibility with the rest of the drivetrain? In general, what do I need to be aware of when looking for parts given that I have an older bike? What would be the methodical way to approach this?

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Looks like you are on the right track. You should be able to remove all but the midlle ring and just change the chain wheel bolts or use spacer to account for the missing outer ring.

One difficulty is that i believe rear axle is longer for the later cassettes, it is about 5 mm so rear drop outs need to reset.

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Thats 5 mm each side.

The rear stays will be 130mm. So 2.5mm each side, not 5mm otherwise you'll end up 140mm width!

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Can i ask why? if it's going to give you a similar range to what it already has why got to all that bother.
Just ride it and enjoy a lovely old bike

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Loose a bit of weight by drooping 2 front ring, front mech, lh shifter and cable ... but cassette will be heavier plus chain'll wear faster.

I was totally against 1x11 but i did buy bike, 29er, and you know what, it works perfectly well.

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I can understand it on a newish bike but on a lovely old '84 Stumpy???

Agreed, nothing to be gained by dragging it into the future as a retromod

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Gruff":3mfat4yx said:

Can i ask why? if it's going to give you a similar range to what it already has why got to all that bother.
Just ride it and enjoy a lovely old bike

Click to expand...

Indeed it is a lovely bike, but in the last 30 years we've made improvements to how we do things. They don't sell 3x5's with friction shifters anymore for good reason.

The 1x setup has no redundant gears, index shifting, no possibility of cross chaining, is simpler to operate with a single shifter, and has less hardware to maintain. In exchange for these advantages, I give up no range of gearing. I am not doing it to save a few grams or to adopt the latest fashion, but rather to increase my enjoyment of riding my bike. I think 1x is a good idea. And worst case, I can always change it back. Bikes are fun to tinker with as well as ride.

Bringing this wonderful old frame into the present seems like a good thing to me. Now to figure out how to do it... :shock:

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02gf74":2f4tzflz said:

One difficulty is that i believe rear axle is longer for the later cassettes, it is about 5 mm so rear drop outs need to reset.

Click to expand...

I just measured the rear spacing. It is 126mm. I found a web page (http://bikes.aberrance.com/stumpjumper/ ... jumper.htm) about a 1982 Stumpjumper which has 126mm spacing so that lines up.

How much will the rear spacing need to be increased? Is it feasible?