700c lightweight wheel, advice needed

Unicycles and Equipment
1

I have in mind a super lightweight 700c set up.

My present 700c is a standard Nimbus 1 with a 700c x 28 tyre.

Roger has very helpfully pointed me towards a narrow race hub with 24 holes. However, I have so far been unable to find a 700c rim with 24 holes. the standards seem to be 28, 32 or 36.

Unicycle hubs come with 36 holes or the one narrow one with 24.

The rim recommended by my local Freewheel bike shop is a Mavic Open Pro. This is a “clincher” rim, which will take tyres as narrow as I like. It comes in 36 hole but not 24 hole form.

Intuitively, I feel that reducing the spoke count to 24 and having a narrower hub would make a 700c wheel somewhat weaker than ideal for a unicycle - especially as nearly every ride has some element of light cross county. However, this is theory, rather than experience talking.

My gut feeling is that any slight saving in weight (12 spokes) will not be worth the loss of strength, even if I can find a 24 hole 700c rim at a sensible price.

Only a very few of you will have ridden super skinny unicycle wheels (it is an acquired taste!) but no doubt some of you ride bicycles too.

Can anyone advise me on this, or suggest suitable rims?

Thanks

Mike

2

I experimented with this last year. Originally my unicycle had a 700 x 45c tire. Using the same hub and spokes I installed a narrower Mavic 700c rim and used a 700 x 28c clincher tire and inflated it to 100 psi. The decrease in rolling resistance was amazing but any advantage I gained in a decreased rolling resistance I lost due to the significantly smaller diameter of the narrower tire.

One day while out on a ride I was about 10 miles from home on a pretty busy stretch of road. Suddenly my tire blew out. The load BANG of the exploding tube and the nasty upd so close to moving traffic is something I won’t forget all too soon. I’m not sure if it was the explosion of the tube or the force of the rim suddenly smacking the ground but my rim had “taco’d” big time! It bent so bad the wheel would no longer turn. Fortunately I had my cell phone in my pack and was able to call for a ride. I decided to switch back to the original rim but this time I installed a 700 x 35c kevlar reinforced tire which worked pretty well. I’ve recently built a 36’er so I’m no longer riding the 28".

3

I would NOT go with a 24 spoke rim. As you stated, it would be considerably weaker and it would be carrying your full weight, unlike a bicycle, where the weight is supported by 2 wheels. I don’t believe the slight weight savings would be worth sacrificing the strength of the wheelset.

4

Well, there is a lot I don’t know and haven’t done. There’s too little time and money to work on all these areas. Since the same is true for you, though, you might consider for this particular project:

[Z] Use as deep a rim as possible (not wide, but deep). This helps carry the lateral and radial stresses that the spokes are not. I see from the catalog that the DT Swiss RR1.2 is quite deeply dished, is pretty narrow, and has a large number of different drillings (20, 24, 28, 32), comes in black or silver, and runs approx USD$80.

[Y]It might be easier, cheaper, faster, and probably just better if, given Z, instead of reducing the number of spokes you reduced the diameter of the spokes. So go for 15 gauge or the lighter triple-butted (14/16/15).

[X]Go for lightweight tubes.

[W]Don’t expect brakes to work because of rub on hill climbs, though it’s possible. But you don’t believe in brakes, if I remember correctly.

[V]Save rotational weight also by changing your footwear, and if the case applies to you, reducing the weight of your legs (which mostly go up and down, but you get the idea).

I haven’t tried this, so this is just the approach I’d take if I were trying to do this for myself for the first time.

Of course, this would not be a setup for rough or cambered ground.

One neat thing is that while training, you can put on a Kevlar tire to reduce punctures (heavy) but then you can trade off to a lighter, more fragile tire when you really want to be lighter under more sanitary road conditions.

5

I use a 700c x 28mm tyre at the moment, although I don’t run it at quite such a high pressure. There are no “practical” advantages to the skinny lightweight set up. I have no doubt that a 29er with a fat juicy tyre would be faster over a journey. But we don’t do this for practicality, do we?:slight_smile:

As it happens, I had a high speed blow out on my first ever ride on my 28, with the standard tyre and tube - but that was because the tube had been put in twisted at the factory.

6

The main reason for reducing spoke count on a bike wheel is to reduce drag, not weight. With the speed a unicycle goes I would reckon it’s better staying with more spokes (certainly as the single wheel has to take all the weight). As I mentioned before, there’s a pair of narrow 700c rims in my attic going spare - you’re welcome to grab one while you’re down here for the muni weekend (or before if you’re around). They’re 36-hole Rigida rims, slightly narrower than Open Pros - I used to run 20mm tyres on them. Nothing flash, but they’re straight, eyeletted and free. You’ve inspired me to try to build something out of the other one - I’m collecting parts now.

Rob

7

Err, isn’t a clincher rim just the normal sort? ie, not for tubular tyres that are just glued to the rim or somthing like that. It’s the width of the rim that’s important, not it being a clincher rim.

What’s the advantage of a narrower hub? I could uderstand not using a silly-wide coker hub, but I can’t say I’ve ever noticed the hub width on my unicycles (all standard hubs) slowing me down. Is it a case of ‘more niche than thou’?

8

Correct. The Open Pro rim Mike mentioned is pretty much the standard good-quality road rim these days - it’ll take tyres from about 20mm up to 28mm, is nice and strong, and quite light.

I presume he’s just going for minimum Q, which theoretically should make for slightly more efficient pedalling.

Rob

9

I wasn’t particularly after a narrow hub. I wasn’t after fewer spokes for its own sake.

The point was I wanted a lightweight wheel. It was suggested that the best lightweight rims would tend to be designed for fewer spokes. The only unicycle hub made for fewer spokes happens to be a narrow one. Hence the question.

I certainly wouldn’t choose narrow for its own sake. I can see no advantages to narrow, and several disadvantages.