Building a true, 700c road uni

Haha, I approve of the name! :smiley:
Although if you’re really making a pure road uni, the Marathon Racer looks better. And if you want versatility, 2" wide Big Apple or various Marathons are really good, not sure you’d want to narrower if you are looking for a do-it-all tire.

Missoula, right! The big apple is heavier than I want to go, so the Mrathon Racer 700 x 38 (1.5") should be a good width for climbing long stretches of steep roads. And climbing would be my main objective with this lightweight setup for my 29er.

Yeah, for a climber that’s still riedable for general road use, I think the 24 rim and 38 M Racer is probably a good bet. I’m eager to hear how this turns out - might have to build a second wheel for my 29er. :slight_smile:

I will probably go with that combo, unless I can find a wider rim made for a rim brake. Speaking of that, my maggies obviously won’t reach a rim so narrow as the 24mm, so I’m planning on going with a good quality V-brake, using these adapters.

I think I found a 35mm wide 700c rim with 36H and made for rim brakes. Please correct me if I’m mistaken. Otherwise, this looks like the way to go for my particular setup.

http://www.amazon.com/Weinmann-Hole-Black-Machined-Side/dp/B0013G8OFI/ref=pd_sim_sbs_sg_3

You might look at the reviews on MTBR - doesn’t sound very strong. . . .

Also, there’s some interesting info on the Schwalbe web site about rim vs tire width.

Thanks for the links. Yeah that weinman, although listed as 700 x 35, is actually 23mm wide when you look at the specs! And "35’ can’t refer to the profile, since it’s very low and square. I think it may be referring to the recommended tire width max, as it corresponds to that on the chart.

And I looked at a similar table showing the rim/tire fitting parameters. That table mentioned that it is only a guide, and that many people run wider tires than the table’s recommendations. But it looks like the 24.5mm rim will easily accommodate a 38mm tire with no problem.

I think it probably is 35mm wide; the profile pics I’ve seen appear to be for smaller sizes. The manufacturer’s website lists multiple sizes.

But you’re still probably better off with a higher quality yet narrower rim.

Why not skip the brake and get a P35 in Teak finish? SEXY! I mean, the uni is for going up, not down, right? Isn’t a brake just extra weight?

Haha, awesome! Well, a brake will be needed for the long ride back down. And even riding my 24 with 110’s back down required a ton of backpressure on the steepest, 15-19% grade sections, so a 29er would be even harder to control going down, especially after all the climbing!

And speaking of that, I know there’s been many discussions about “rotational weight”, and its effects on climbing, etc. I’ve been reading a few b*ke forums and found one thread that caught my interest. Not sure if this would translate to unicycles, but I would assume that physics would apply the same way:

Here are just two posts I found very informative:

[I]As an engineer, I can tell you the hype about weight is HIGHLY overrated.

There are two factors concerning weight:[/I] [I]

  1. Lifting it while climbing.[/I] [I]

  2. Accelerating it.[/I] [I]

For just cruising down the road, weight it almost irrelevant. Aero drag is the primary force you have to overcome, followed by a significantly lower frictional force due to rolling resistance of tires, bearings, etc.[/I] [I]

As far as rotating vs. non-rotating mass, rotating mass is only a factor (above non-rotating mass) during acceleration (and deceleration). So, it’s really only significant for those who need sprint performance (racers). As far as climbing is concerned, lifting an extra pound on the wheels is no different from lifting an extra pound on the frame.[/I][I]

So, if you really want to improve your performance, don’t eat that second taco and loss 10 lbs off the engine. The performance gain will be 10 times that of new wheels and will cost you nothing.[/I]


And:
[I]

When riding uphill at a constant speed, the work you are doing to lift the weight of the system (bike and rider) is mgh, where m is the mass, g is the gravitational acceleration, and h is the height through which you lift it. When I say acceleration with respect to the bike, I mean you are going from a slower to faster speed, i.e. you are increasing your velocity.

When you accelerate (speed up), you must put energy into two things beyond that needed for a constant speed for the given conditions (whether you are riding up and hill or on the level). First, you must accelerate the mass–good 'ol F=ma. That includes the mass of the bike, wheels and rider. This is called rectilliner acceleration or increasing the kinetic energy (linear momentum). Second, you must also provide for the rotational acceleration of the wheels–this is above the energy required just to accelerate the wheels in the direction of travel. This is called angular acceleration or increasing the angular momentum of the wheels.

For example, if you pick up a rock and throw it, while it’s flying through the air it has kinetic energy–to slow it requires a force (drag or gravity). If you tie a string onto it and whirl it around in a circle, it has angular momentum and it takes energy to either speed up or slow down the rotation. Of course, when you let go of the string, the rotation energy is then converted into kinetic energy as the rock flies off in the straight path.

You can think of it this way: the wheels are kinda a double whammy cause you gotta both accelerate them forward, as well as “spin them up.” But unless you’re racing . . .

Climbing is simply lifting all the mass up through the earth’s gravitational field. The more mass or the higher or faster you lift it, the more work is required.

[/I]

I had a 27x1 1/4 (630x32) wheel for a while before I got my 36er. It was incredibly nimble, to the point where I actually added weight to slow it down. It was both good for cruising with very little effort and great for learning precision in wheel movement snaking between rocks, down erosion channels and cutting through slush.

I say go for it, and don’t be afraid to use it for rides other than hill climbs.

Wow, I wasn’t really aware of such a tire size! Almost sounds like a better size option to the 29er, at least for hill climbing! What tire/rim combo did you use, and do you know if they are they still available?

I’m afraid that size is now almost totally obsolete. It was what I had on my first “racing” bike, and very common in the UK at the time (25 years ago), but almost completely replaced by 700c now. You’ll probably find some tyres, but only in a standard 1 1/4 (30mm) section, which is a bit narrower than I think you want, and tyre supply isn’t about to get better. Not worth the hassle for an extra 8mm rim diameter.

That would explain it, lol. So after lots of searching and looking at various rim/tire combos, I think I’ll be going with the Velocity Dyad and the marathon supreme racer, 700c x 38. The rim is a lightweight 480g, and the tire is 435g.

Looks like that rim is 32 hole - what hub?

I’ll be getting the 36H, which you can select from the drop down menu. It’s available from 32 to 48h. I’ll use the existing hub on my 29er. The rim has all kinds of flat spots anyway, from lots of drops and hard tech MUni. Haven’t used it much at all since I got my G26er, so at least this new setup can breathe some new life into it. :slight_smile: I’ve been thinking of places where I can do miles and miles of road climbing in the 6-15% range, and the super long stretch leaving Las Vegas came to mind! That would be fun!

I think you’ve selected a great rim and tire combination. I’m mainly an urban rider. I use a 28" x 2.0" Schwalbe Marathon Dureme tire on a Velocity Blunt rim. I find that the tire is rolls smooth and fast on asphalt but has tread that is versatile enough for light-off road (i.e. loose dirt, gravel) use as well.
It has a max PSI of 60 but I keep it at around 50-55 PSI.

Julius

I meant to add that although this is a 28" x 2.0" tire, it fits on a 700c rim. The tire is essentially a 29er.

Terry, why not rebuild your G26 with a mid width rim like the P35, then you’d have a strong rim and it would be wide enough for a 3" tire and narrow enough for a 2" tire.

It just seems kinda silly to build a road 29 that be very fast.

I’m working on a 29 XC Guni, I’ll probably run the P35 and a Knard on an Oracle 29 frame once the crown height is adjusted for clearance.

I’m not building the 29er for speed; I’ll be using it solely as a road climber.

This is my current 29er setup for road climbing, until I build the new, ultra light wheel. This setup uses the standard kh 47mm freeride rim, a continental race king 2.2 folding tire, (half the weight of the wtb stout!), drilled out qu-ax 170mm cranks, for those 18% grade stretches, and HT AE01 super thin and very light pedals. (Btw, the cranks are listed as “lightweight” on UDC, but actually weigh 2 1/2 times their advertised weight per pair, hence why I drilled the holes!)

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