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emergency singlespeed conversion - how?


cat-i
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The situation:

So the rear derailleur broke in a remote area of tibet, far from any bike shop. It got caught in the spokes, and was bent badly, so that the top wheel-thingy de-railed the chain before it got to the bottom wheel-thingy.

 

under chants of 'Remove the derailleur and make a singlespeed', some guys removed it and shortened the chain. Test it - chain climbs up to next gear (at back). Ok, lengthen chain again and put it on that cog - no luck, now it wants to climb down to the smaller one.

 

The question:

- Any advice on how to change the bike into singlespeed without a derailleur, and get it to work without the chain wanting to go to a different gear than the selected one? I tried to select what looked like the gear that was in line with the middle blade at front, but obviously it was not in line enough. Is it even possible to make a singlespeed without using a derailleur as tensioner?

- Would it have been possible to bend the derailleur back in some way, and use it as a tensioner?

 

Anyone has done this successfully before? Please send some instructions or pointers?

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Guest Frail4Life

Hello Cat-i

 

First lock the chain in specific gear by setting the Two small screws at the back of Derailler. I do not see a problem bending the Derailler carefully. You can also run the chain Singlespeed without removing the Jockey.

 

The important point is those two setting screws, locking the chain onto one gear.

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I managed to get it right once during the Lost City race.

 

I carefully measured the chain after putting it on the middle chain ring and the middle of the rear cassette. I then removed the wheel and joined the chain. I put the chain back onto the cassette and then had to force the wheel back in to the drop outs to maintain the tension. if it is still too loose remove the wheel again and move it up to the next biggest gear on the cassette and try again. It will only work if you have it fairly tight and running fairly straight.

 

Good luck.

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I managed to get it right once during the Lost City race.

 

I carefully measured the chain after putting it on the middle chain ring and the middle of the rear cassette. I then removed the wheel and joined the chain. I put the chain back onto the cassette and then had to force the wheel back in to the drop outs to maintain the tension. if it is still too loose remove the wheel again and move it up to the next biggest gear on the cassette and try again. It will only work if you have it fairly tight and running fairly straight.

 

Good luck.

 

IanJ is 100% correct. I have done this on numerous occasions, Sani2C the latest one, where my partner rode the last 50km on the last day in single speed after his rear derailleur disintegrated into a handful of parts. We just took the derailleur off and shortened the chain to fit the middle rear cassette gear and the middle chainring and locked out his rear suspension.

 

The chain sometimes jumps up but you then just stop and loosen the wheel and drop the chain down again. The secret here is to have a smooth pedalling technique, not huge bursts of power, just smooth full circle pedalling and it stays on the right gear at the back.

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I have had to do this procedure a few times, but have a problem with my chain scraping against the chainstay of my full sus. bike. I have scraped a serious amount of aluminium of my chainstay before.......

This means that I have to use a lower gear(larger cog on cassette)to get the chain to clear the bottom of my chainstay.The result is a less than perfect chainline.

It's a good idea to work out how many chain links you need to remove, write this number down and put it in your Camelbak or somewhere obvious.

 

Locking out the rear suspension is really crucial to prevent excess chain tension.

You can also use your fingers to move the chain up to a more suitable cog as you pedal slowly (helps to have a mate around then)until it finds a cog that it will stay on with acceptable chain tension.

This way you can have a slightly loose chain to start off with but as you move it up to the next largest cog (or two) the chain tension will increase and the chain will (hopefully) stay there when you pedal off into the sunset (or darkness in my case!)

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If you make the chain to tight. This sometimes happens as between 2 gears (one to tight the other to loose).

If the chain is to tight then you will almost always damage your BB.

We had the situation in the first Nissan race as a rider broke his der and we made it single speed.

The extra tension on the chain caused the BB bearings to fail after a couple of kms. (I think that the bearings aren't designed to handle that much pressure.

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Very interesting posts. Thanks, guys now I'll hopefully be able get myself home if this happens again.

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