Tandem Wheelbuilding Advice Needed

[Martin109]

I'm thinking about upgrading the wheels on Bertie the tandem, mainly to provide STI-controlled 8-speed shifting, but at the same time to give it some lighter, tougher wheels.

I've already got myself some Velocity Dyad rims, 40H for the front, and 48H for the rear.   The hubs will be Shimano Tandem XT front and back (hoping the prices don't go up too much before I can afford to buy them!).

My question is about cross pattern.  Should I be thinking about lacing the front 3-cross and the rear 4-cross, or front 4-cross and rear 5-cross?  I can't seem to find an exploded view diagram of the Shimano hubs on the net, or any specific dimensions, but they're described as 'large flange'.

I have a certain amount of wheel-building experience, and have just finished rebuilding a front, but my experience is confined to standard 36-spoke 3-cross, design, and mostly front wheel or fixed rear, so less experience with dishing and the demands of a geared tandem rear.

As a starting point, I would be thinking of Sapim or DT double-butted spokes, but is there collective wisdom on how best to build the rear?  I'll be starting with the front anyway, but wanted to include both in planning.

[Ian H]

I'd do both 4x. I think it's DT who do triple butted spokes that are 13 gauge at the bend. That means a tighter fit in the flange and a stronger wheel.

[blackburnrod]

Good spokes and 4x front and back.DT spokes are best and need to be 13 guage at the hub end.They are not cheap but will be cheaper in the long run.

[LittleWheelsandBig]

DT Alpine 3 spokes are 14/15/13 gauge.

[Martin109]

That seems pretty conclusive and unanimous!

[Martin109]

Wow!   That's £73.92 for 88 spokes at SLS Cycles, before any postage & packing!  Anyone do them cheaper?

[Martin109]

Answered my own question!  £66 for 88 at J D Cycles, and more modest P & P charges.

[Butterfly]

JD are fab, it's a fact.

[aidan.f]

Try Spa Cycles for your spokes Sapin - haven't brought any for a while but the quoted prices seem high

[damerell]

The hubs will be Shimano Tandem XT front and back (hoping the prices don't go up too much before I can afford to buy them!).

Are you set on that? I found correctly adjusting cup and cone bearings when a drum brake is going to sit on top of them to be somewhere West of nightmarishly hard, and eventually gave up and bought a White Industries rear. Currently they're $250, which - well, it was cheaper before the pound collapsed.

[Martin109]

Are you set on that? I found correctly adjusting cup and cone bearings when a drum brake is going to sit on top of them to be somewhere West of nightmarishly hard, and eventually gave up and bought a White Industries rear. Currently they're $250, which - well, it was cheaper before the pound collapsed.

Probably a bit beyond my budget!

[Martin109]

Looking at the SpoCalc calculations for the rear wheel, I'm struck by how close the left and right spoke lengths are.  For a 4-cross build with 48 spokes, the lengths quoted are 283.6mm (left) & 283.1mm (right), which is only 0.5mm difference!

An Excel file with the rear wheel data is shown here.

What are the factors that determine that small difference?  Should I just round down and get 48 spokes at 283.0mm?

[Chris N]

What are the factors that determine that small difference?  Should I just round down and get 48 spokes at 283.0mm?

Less asymmetrical flanges.  Normally, the drive side flange is much closer to the centre line of the wheel, but with a 145mm OLN the flanges can be more evenly spaced, so you get a stronger wheel.  I'd use the same length spokes both sides.  282mm, probably.

[Martin109]

Thanks, Chris.

What prompts you to round down so much?

[Chris N]

Spokes are easier to get in even lengths.

[Martin109]

Judging from the J D Cycles range, I'll have to go for 284mm!

[Zipperhead]

What are the factors that determine that small difference?  Should I just round down and get 48 spokes at 283.0mm?

When I rebuilt my back wheel I used the same length on both sides. It also conveniently means that I can carry a couple of spares which can be used on either side if I break one (the flanges are large enough to allow spoke replacement with the gears in place)

[thing1]

When I rebuilt my back wheel I used the same length on both sides. It also conveniently means that I can carry a couple of spares which can be used on either side if I break one (the flanges are large enough to allow spoke replacement with the gears in place)

Nice.
Our touring tandem isn't so fortunate with spoke/flange arrangement, but I just got a few Kevlar emergency spokes. (Got them for half the SJS price by ordering direct from the USA).
Not had reason to use them yet but I've only heard good things about them.

[Martin109]

Answered my own question!  £66 for 88 at J D Cycles, and more modest P & P charges.

Well, I've now acquired all the bits and built the wheels!  I can recommend both J D Cycles, and Rose Versand in Germany:

40 DT Alpine III spokes & nipples for front wheel from J D Cycles (incl. £1.60 P&P) - £31.60
50 DT Alpine III spokes & 40 nipples for rear wheel from Rose Versand (incl. P&P) - £28.29

That price from Rose Versand is really good, I think, especially when compared with £73.92 (excl. P&P) from SJS for 88 spokes.

And I was able to get the exact length I wanted - 290mm for the front, and 283mm for the rear.  Following Spartacus's suggestion, I got 2 extra rear spokes as spares.

The Shimano tandem hubs are lovely, as are the Velocity rims.

Thanks for everyone's tips and suggestions!

[Tewdric]

Good luck with the build - If you would like to make use of the Park TS2 / WAG4 / TM1 kit in the SICRUT BWNCWR here you're more than welcome. 

[Martin109]

Thanks, T.

They are now built, in terms of laced, but not trued and tensioned.  I think I'm going to entrust that bit to the wheelbuilder at Argos in Bristol, as it would be difficult for me to deal with the 145mm OLN rear, the critical nature of required wheel strength and the trickiness of the DT Alpine III spokes.

They look smashing!