mdtenor

My wife and I have been thinking about doing some gravel/dirt road/poor-pavement touring on our Co-Motion Primera next spring. With fenders fitted, I'm not sure I can go much beyond 700x32 tires, although I don't have much experience with narrow-ish gravel touring tires. Most of my time off-road has been on mountain bikes. I sense, based on the few times we've been in gravel on the tandem, that more volume and width will really help with comfort and control.

I was thinking about shopping for a set of dedicated dirt touring wheels in 650b. Does anyone have experience with doing this on a tandem? I've searched and it seems like single tourers occasionally do this. Looking at the fork and chainstays, it seems like I would gain several millimeters of side clearance and room to have a higher-volume tire, both of which seem like good things. (By the way, we have dual disks, so no concerns with wheel swapping.)

Are there any downsides to this approach? Would a 26" wheelset be better, or would it change geometry and handling significantly? What tires do you all like for hardpack and/or gravel...I imagine we won't be seeing too much mud, although I guess it's not out of the question.

Sorry for all the questions, but this is an area where I have literally no experience, just an idea. Looking forward to success stories, cautionary tales, or any advice about choosing a wheelset. Ideally, I'd like to find a fairly affordable wheelset, as they won't be our primary wheels, but durability and flexibility are key concerns.

Again, thanks in advance...

Andrew

Chris_W

I wouldn't start looking into new wheels until you've tried putting the largest tires that will fit with your current setup and going out and riding some unpaved roads. They'll probably perform better than you expect unless you start getting aggressive with the braking or steering.

We have a Co-Motion Speedster and I wanted to equip it with 35-38mm tires and fenders for some touring in New Zealand, but soon found that the steel fork (a V-brake version by Co-Motion) wouldn't fit anything more than about a 32mm tyre with the fender, with the height being more of a problem than the width. Given that Co-Motion market this as a touring tandem, I was surprised by the lack of clearance. We have now upgraded the fork to a Co-Motion carbon disc fork, and that actually has several mm's more clearance than the steel V-brake fork because the crown/steering column doesn't stick down as far even though the axle-to-crown length is the same. I have no experience with their steel disc fork.

Anyway, we did some long, rough dirt roads while touring in New Zealand and had no problems with traction with a 32mm on the front and a 37mm on the rear (over 500 km on unpaved roads of various qualities out of 2500 km total). The rough gravel did do a pretty fast job of making many, many small gashes in the 700x37 Schwalbe Marathon that we had on the rear (fortunately nothing got thru to the tube, but the tire's green protective underlayer was showing thru many of the small cuts), so halfway thru the tour we found a bike shop who taught us the difference between the standard Marathon model and the Marathon Plus, which is way tougher, and so we used one of those for the rest of the tour and it shrugged off everything that we threw at it and was still looking fine at the end.

The only puncture issues that we had were from an inadequate rim strip (made by BBB), that gave us a few headaches until we figured out what the problem was, bodged a repair with the electrical tape that we were carrying with us, and then finally found a shop with a sturdy replacement. We never had any pinch flats IIRC, despite a total weight (riders, bike, and gear) of well over 200 kg (450 lbs).

Carbonfiberboy 

I've thought of doing something similar. What rims were you running? Tire pressures?

mdtenor

So, the height of larger volume tires looks to be more of a problem than the width, as Chris W suggested. Especially problematic because of the fenders. While they are installed as high as possible, they still reduce clearance somewhat. That's why I was thinking of 650b's; more for volume than side-to-side clearance. Also, while I'm sure our Spinergys are durable, I'm not sure I'm super comfortable taking them on rough-road touring (We're a 350lb team...plus water and gear).

B. Carfree

We do a bit of touring on gravel/dirt roads and lots of joy riding on gravel logging roads (a local delicacy). However, our tandem is built for 26" wheels. We've been super happy with the tires from Compass, but since they are much more interested in the market for 650B, they only have one tire type for 26" and it only comes in two widths, 1.5" (37 mm) and 1.75" (44 mm). On dry gravel, it doesn't make much difference which width we roll in terms of stability and steering. However, there is a noticeable difference in comfort, particularly for the stoker (me), when we go to the 44 mm width. Since our gravel is infused with our coastal red clay, when it gets wet (about three-fourths of the year) it's a bit slick and the wider width makes for a better ride (more stable equals faster).

I like your idea of going with a smaller diameter wheel to allow for a wider tire. From the stoker's saddle, the wider the better. My captain also prefers going as wide as possible since it requires less effort on her part to control things. We've also found that wider tires are faster for us on the road, or at least they allow us to coast further and faster than skinny tires on the same descent. Better comfort, better speed, better stability. The only downside is increased weight, but you are beating that down by going with a smaller diameter wheel.

I do wonder just how much the geometry will change on your bike if you go to 650B or 26" since the wider tires are usually also taller. I suppose you may lose a bit of trail, but there's quite a range of trail lengths that people ride with so maybe you'll be okay there.

Chris_W

We don't own any "go fast", light, fancy tandem wheels, only touring/all-purpose models (tandem wheels are not a good place to look for weight savings IMO). The rear rim was a Mavic A719 40-hole model, the front was a 36-hole (due to using a dynamo hub) A319 IIRC (possibly an A719). When those wear out, I'll replace them with DT Swiss TK540 rims because I've found those to be easier to build, have a great braking surface, and have been super-solid when riding them on other touring bikes, so I now prefer them to Mavics. The tandem originally came with 40-hole Velocity Dyads, which were not so good, especially because they developed bulges in the brake track and so caused pulsating braking. After replacing the front with the exact same model (which was not easy to obtain in Europe), and then experiencing the exact same problem after a few months, I've vowed not to touch that brand again. (BTW, I'm an experienced wheelbuilder who's built more than 200 wheels personally and professionally).

Tyre pressures would have started at 80 psi on the 37mm rear and 90 psi on the 32mm front, although they were probably lower on some days because I don't remember topping them off more than once per week.

waynesulak

Good to have PSI figures on wider tires. What was you total load weight and what tires do you use at those pressures?

Carbonfiberboy 

Thanks so much. I've known others with problems with Dyads, though I've had very good experiences with their Deep-V rims. Some wider rims are not good with wide tires at high pressures which are necessary for heavily loaded tandems. Marathons and the Pluses are one of the few tires which are rated for the necessary pressures. Those DT Swiss rims are only 50g heavier than the Kinlins I'm running for sport rims. DT Swiss has kindly published a very useful chart of acceptable tire pressures for various of their rim widths and the tires which can be mounted on them. It's very much worth a look for tandem riders:
https://www.dtswiss.com/Resources/Tec...sure_Dimension

waynesulak

Thanks for the link Carbonfiberboy that is a very useful chart. We have been very happy with 40mm (labeled 38) Grand Bois tires on Velocity A23 rims. We do tour so total load weight for us is about 330 lbs.

There are some advantages to 650B tires which may or may not be worth it:

- 650B rims are about 40mm smaller in diameter than 700C. As a result our 40mm tires fit easier in a tire bag (or S&S case) than 33mm 700C tires.
- Less toe overlap
- The handling seems a little better at high speeds to me
- The rims, spokes and tires all weigh less
- Slightly stronger wheel due to the 40mm small diameter rim

If you currently have one set of wheels, it may be worth it to have a spare set regardless of the size. Choosing a spare set of 700C would allow use of same tires.

Chris_W

I mentioned in my previous post that total weight was over 200 kg on that tour: 140kg for two riders (with shoes and clothes), 20kg for the tandem (with all accessories mounted), and up to 40kg for the luggage (including the 13 bags themselves plus food and water - we had over 5 litres capacity in 7 bottles). I also mentioned above that the tires were Schwalbe, Marathon and Marathon Plus, but next time I would only use the Marathon Plus.

We also had a 28mm-wide, lightweight Marathon Supreme spare tire rolled up and stored under the Captain's bottom bracket. We used it when we were searching for the cause for our repeated rear flats, but when it didn't solve the problem we concluded that the rim strip was the culprit - an almost new, but not-so-sturdy model by BBB. I've since read of other tourers having problems with BBB rim strips and will never use those again.