Tandem Avalanche envy mtb - 52blade conversion

[albertbiker]

Hi, looking to convert our Avalanche tandem envy 29inch currently with 42, 32, 24 setup to road bike blades - 52, etc. 170mm crank.

 

Two cycle shops in cape town told me they cannot assist after trying to source parts.

 

Problems encountered so far:

Chainrings cannot be replaced individually , need to replace entire crank on the one side of tandem.

Found a replacement with 170mm but the actual square hole through crank sits square with crank, not positioned as newer cranks.(corner of square hole in line with the crank) if this one is fitted the crank on the other side (32tooth crank) will sit at incorrect angle with other side.

 

So next step is to replace that side of the crank as well, but no one can find stock.

 

Two years ago there was a forum regarding this exact conversion.

Anybody with knowledge on this?

 

Apologies, my use of words for cycling parts are probably incorrect but hope it makes sense.

 

Thanks

[albertbiker]

Two reference photos

[V18]

This is probably a terrible idea... But put a dh casette on. Ratios will be close to what you want but chances of slippage under tandem torque and premature wear is going to be cray cray.

[droo]

You're either gong to need a tandem crankset ($$$, and rare in SA) or a square taper road triple  crankset, or two diamond taper cranksets so you can use the second one for the timing chain.

 

I'd suggest a wanted ad in the classifieds for one of the first two, there is definitely one in someone's garage somewhere collecting dust.

 

Or chat to Nils at Woodstock Cycles, he may have something.

[100Tours]

I have spent a lot of time re-configuring tandems - here's my experience FWIW and I'm very happy to try to help off line too if that's useful. Tandems have no standards.

 

1. Don't assume that you should match crank lengths for this. We ride a 172.5mm crank up front and a 165mm at the rear because the crank length different helps us match our cadence (shorter cranks allow a higher cadence with shorter legs).

2. Consider using a double (also consider elliptical for the inner ring) chainring rather than a triple for this change - there are many more 2x chainring choices available. Our road tandem is set up with a 34/52 chainring (elliptical) in front and an 11/36 in the rear - this violates all of Shimano's specs, but it works fine after some derailleur modifications. 700km this week without issues. [using double rings would also allow you to run the timing chain on the right]

3. You may find that the chain line is out if you replace your tandem triple with a 'normal' 2x crankset. We have a 2x chainring on the tandem taken off a single bike, and we have had to space the front chainring 5mm off centre to get things in line (so far so good with this though).

4. you're not limited to a square taper BB - if you replace the BB itself then any appropriately threaded BB should do, and a new BB is cheap.

 

 

 

Hi, looking to convert our Avalanche tandem envy 29inch currently with 42, 32, 24 setup to road bike blades - 52, etc. 170mm crank.

 

Two cycle shops in cape town told me they cannot assist after trying to source parts.

 

Problems encountered so far:

Chainrings cannot be replaced individually , need to replace entire crank on the one side of tandem.

Found a replacement with 170mm but the actual square hole through crank sits square with crank, not positioned as newer cranks.(corner of square hole in line with the crank) if this one is fitted the crank on the other side (32tooth crank) will sit at incorrect angle with other side.

 

So next step is to replace that side of the crank as well, but no one can find stock.