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-   -   Using MTB or CX rims and tyres on a tandem. (http://www.bikeforums.net/tandem-cycling/930340-using-mtb-cx-rims-tyres-tandem.html)

VeganGraham 01-18-14 08:42 AM

Using MTB or CX rims and tyres on a tandem.
 
We've got a Viking Saratoga MTB tandem with various upgrades and I'm now building up a second tandem on what I believe is an Orbit frame. It looks exactly like this.
The frame is suitable for both 26" and 700c/29" wheels and we want to use it for longer distance rides with the option of some fairly tame off roading, canal tow paths and forestry tracks for example.
Something equivalent to a CX bike with flat bars would be better than a full on MTB.

It's traditional for tandems to use 40 or even 48 spoke wheels, yet downhillers get away with 32 spokes and they look like they put far more strain on the wheels.
So, in the real world, is it a good idea to ride an off road tandem on say, Stan's 700c Alpha 400 or Flow 32h rims with Small Block 8 tyres with a combined rider weight of ~160kg and day luggage only ? Would the 26" version be noticeably stronger ?
We'll be using a Rohloff hub and disc brakes, so we are stuck with 32h on the rear at least anyway and have no need for a braking surface on the rims.

Any other recommendations for a rim & tyre that's reasonably fast on road, yet still reasonably durable off road ?

swc7916 01-18-14 01:28 PM

I have no off-road tandem experience, but since I'm probably the only one on this forum with a Rohloff tandem I will chime in here. Our builder insisted on using the strongest rim he could get, which is a Velocity Chukker in 26". With the Rohloff hub and the Chukker rim, this wheel is HEAVY and we have had zero problems with it. Considering that you have only 32 spokes I would be reluctant to build it with 700c wheels, especially if you plan to go off-road.

mstyer 01-19-14 07:00 AM

When building my tandem, I inquired with Stans about the suitability of their MTB rims for use with a 28c tire. I was told that those rims were not suitable for the higher pressure tires.

Have you considered a 650B rim with a higher volume tire? It will give you a finished wheel diameter similar to a 700x23. http://www.rivbike.com/650B-Tires-s/111.htm

Bezalel 01-19-14 09:08 AM

You will need to be creative getting a Rohloff hub in that frame. The Rohloff is 135mm and that frame is 145mm and being aluminum it can't be respaced to 135mm.

VeganGraham 01-19-14 10:46 AM

I've already thought about that, Bezalel.
The plan is to cut two 5mm shims and get them tig welded to the inside faces of the dropouts.
If I use a Monkeybone, then another 5mm shim between that and the frame will get the caliper and OEM2 axle plate lined up correctly.

I'm pretty much settled on the idea of 26" wheels now. We'll lose a bit of ground clearance, but I reckon it's the strongest option.
We'll probably use a 1.9" or 2.1" tyre, so I don't think Stan's pressure limit will be a problem.

Going back to my original post;
Does anyone know why tandems traditionally had 40 or 48 spokes, while modern down hill bikes have 32.
My guess is that in the old days it wasn't financially viable to make a small run of stronger rims just for tandems, so the only way to strengthen a wheel was to add more spokes.
Nowadays, with cheaper automated production, rims can easily be made in any profile and diameter in small batches, so the easiest way to make a stronger wheel is to make a stronger rim.
Am I anywhere near right ?

Bimmer74 01-19-14 01:55 PM

Quote:

Originally Posted by VeganGraham (Post 16421200)
It's traditional for tandems to use 40 or even 48 spoke wheels, yet downhillers get away with 32 spokes and they look like they put far more strain on the wheels.

Hmmm...

Downhillers have cushy long travel suspensions and low pressure/large volume tires. I doubt you do.

Downhillers also seem to find it perfectly acceptable to regularly have their wheels rebuilt and/or occasionally "taco" a wheel. Do you?

Mike Ayling 01-22-14 04:50 AM

Quote:

Originally Posted by VeganGraham (Post 16421200)
We've got a Viking Saratoga MTB tandem with various upgrades and I'm now building up a second tandem on what I believe is an Orbit frame. It looks exactly like this.
The frame is suitable for both 26" and 700c/29" wheels and we want to use it for longer distance rides with the option of some fairly tame off roading, canal tow paths and forestry tracks for example.
Something equivalent to a CX bike with flat bars would be better than a full on MTB.

It's traditional for tandems to use 40 or even 48 spoke wheels, yet downhillers get away with 32 spokes and they look like they put far more strain on the wheels.
So, in the real world, is it a good idea to ride an off road tandem on say, Stan's 700c Alpha 400 or Flow 32h rims with Small Block 8 tyres with a combined rider weight of ~160kg and day luggage only ? Would the 26" version be noticeably stronger ?
We'll be using a Rohloff hub and disc brakes, so we are stuck with 32h on the rear at least anyway and have no need for a braking surface on the rims.

Any other recommendations for a rim & tyre that's reasonably fast on road, yet still reasonably durable off road ?

WE have a Thorn touring tandem with a 32h Rohloff on the rear and a 32h Shimano LX on the front using Rigida Andrada rims which are heavy but Thorn tandems have done some incredible tours over some terrible road surfaces running these wheels.

For a well built non dished wheel I think that 32 spokes are fine for tandem loads. For a dished rear wheel with a 10 or 11speed cassette 40, 44 or 48 spokes may be a better choice.

Mike


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