torger

Here's my new gravel wheel build for our 2018-2019 Cannondale Tandem Road 2. I've also built a pair of aero wheels (seen in a different thread), but these will be these will be the main wheel as we ride quite a lot of gravel. The Cannondale Tandem was designed before gravel was a thing so tire clearance is okay but not great, you get in about 35-36mm rubber on a 700c wheel. So I decided to size down to 650B. Still it's quite tight, I'd say you shouldn't go past about 45mm (Pirelli's new Cinturato 650Bx45mm comes into mind) in the back wheel. It's hard to know where the limit is without testing so I got Vittoria Terreno Dry 650Bx47 as seen in the picture. With that clearance is 1.5mm in the smallest place in the rear. As the frame is slightly asymmetric by dishing the rear wheel 1mm to the right I can get 2.5mm on either side, which I think I'll do and see how it goes. I think tight clearance in the back is not too dangerous. In the front clearance is not a problem. If it turns out to be too tight in practical use, I'll swap out the tires and try the Pirellis.

I dismantled the stock wheels and built these new wheels around the same DT Swiss 540 hubs, with the same 36 spoke lacing. The rims are Ryde's heavy duty Andra 321. I wanted a bit "racier look" though (the Andra 321 is a touring rim with no decal except for model name sticker which I removed) so I made custom decals cut from reflective vinyl in a cutting machine.

Spokes are standard round ones from Pillar, 9 of them in gold color. As the huge 200mm disk is rather visible I chose a bling one from Reverse Components. And I hope a valve cap is okay for gravel, so I put a gold one there :-).


650B tandem gravel wheel

Badidea

That is super cool. Will you post pictures of the complete bike?

torger

I will! There's only one wheel in the photo as the back wheel was not ready when I took the photo, but now it is. So I'll put together the bike during this week hopefully. The bike itself is in a different location for winter storage (still a few weeks until season starts here in northern Sweden), so it takes some moving around .

torger

Wheels on the tandem

torger

I had to make little hack as the tires at 48mm actual width on the 21c rim is a bit too much for this frame. By setting the rim 1mm to the right I got 2.5mm on both sides on the slighly asymmetric chainstays, which I think will be enough for dry conditions.


Hack: rim is 1mm off center to maximize the small tire clearance between the slightly asymmetric chainstays

due ruote 

FWIW, we managed to put 700c x 37mm Supple Vitesse tires on our 2014 Cannondale. The fork crown is the tightest spot. I have no idea whether/how much clearances vary between model years.

lichtgrau

That's a really nice wheel, I like the yellow/golden/black play of colors. We use the same Andra 321 with (also) 36 spokes (but) in the 26"-version. They are built around a Hope hub in front and the Rohloff in the rear. My trust in this setup was constantly rising during our first year of use and up to now -after 6000 km- it remains on a high level. Both wheels are still running true without any corrections. I always liked the plain/simple look of those rims. But your decals are nice too. With a closer look at the spokes in your pic it seems as if there's a bend at the yellow spoke near the valve: Probably just an optical illusion?

...and the bike itself: Nice thing. Like that frame. Happy start of season. Here (in Germany) we kind of skipped the winter. And these crazy times with the virus give us more time to ride than ever. With a good distance to everyone else, of course.
Have always a good ride @ stay healthy...

torger

I hope so! I'll check the wheel. I'm a beginner wheel builder so we'll see how these will hold up. I plan to inspect them now and then.

mtseymour

Nice wheels! How do you like the Reverse 200mm Disc Rotors? Are they comparable to the Shimano XT Ice-Tech rotors?

Leisesturm

As I understand it, 40mm is plenty for gravel. 2.5mm clearance is absolutely courting disaster. I can easily see being stuck, miles from home, by a broken spoke that warps the rim by much more than that. This all looks like a new bike to me. One designed for bigger rubber.

torger

I haven't had opportunity to test this rig yet, still a few weeks of winter left here. It's mechanical brakes (Avid BB7) on this bike which I think is the "weak spot" in the brake system. I've changed the brake housing from the cheap stock items to Yokozuna Reaction, that made a big difference. So I think the braking is adequate, but still not as good as hydraulic. I doubt I'll be able to notice any difference from the disc rotor. The old ones where Avid which I'm re-using on the aero wheelset. We ride in quite flat terrain usually too, so there really isn't that much braking. As long as the rotor stays true I'll be satisfied I think, for that I don't really know if the alloy carrier is a plus or a minus. I got it for the looks

torger

I run 35-37mm on my single gravel bike, and I've noticed that for the tandem I prefer to have wider rubber to get the corresponding feel. I think it's due to the bike being heavier and less nimble. Before this we rode 35mm gravel tires on the 700c wheels as that was (about) the widest we could fit, and I felt it was a bit too narrow when getting onto the rougher stuff. We haven't tried this yet though, the 47mm tires may indeed turn out to be a bit overkill (my riding partner will like the comfort it will bring though), so maybe we'll step down to 45 or 42. Can't get too narrow as the diameter goes down making pedal strikes likelier.

Indeed 2.5mm is not optimal, and I wouldn't recommend it to long adventurous tours when things must not go wrong. However we don't ride in that style, so getting stuck somewhere wouldn't mean disaster. I haven't really tested how untrue the wheel gets with a broken spoke, but it is a 36 spoke wheel so I *think* you can get away with one broken spoke and a bit of field adjustment with a spoke key (which is a part of the repair kit).

lichtgrau

…that’s what I’m always thinking about when I see tandems with relatively thin tires without any extra rear suspension. My stoker didn’t like the feeling at all: Me… riding over a bump… not commenting on what I’m doing... a direct stroke in the back and no chance to react. After installing the Thudbuster for her she made no further comments on that… For us it solved this problem better than my 47mm tires did... (I know, those things are ridiculous to install if you are a weight weenie or a design victim: In that case [at least for me] design follows function. Plus - the stoker has to be happy ;-)