speed difference between 29" and 24" uni?

I know there have been many threads disscussing 24" vs 29" unis, but i couldnt find anything that explicitly said what the difference in speed between a 24" and 29". And how much harder is steep, gnarly, rocky muni on one or the other…lets say a 24" with 165mm cranks and a 29" with 137mm cranks… which will be faster and which will be more fun for technical muni?

thanks

All else being equal, a 29er will be 20% faster than a 24" unicycle.

But all else is rarely equal.

There are no good 29er tires for serious MUni. A 29er with 137mm cranks would not be feasible to ride at all on steep, gnarly, rocky MUni, but you would certainly hit the ground at a higher rate of speed. A 24" with a real MUni tire can handle gnarly MUni, but is extremely slow relative to almost any other unicycle.

The tire makes a huge difference. A 24" set up with a road tire and short cranks can be almost as fast as a 29er, although more tiring to ride. A 24" with a MUni tire will be slow no matter what cranks you put on it.

The simplistic answer is a 29 is 29/24 as fast as a 24.

29/24 = 1.2, so it is 1.2 times as fast, or 20% faster.

That assumes identical cranks, identical tyre sections, identical skill and confidence, and a smooth surface.

Over distance, the bigger wheel will cruise faster, because it will tend to smooth out the effects of minor bumps and changes in the surface of the ground. There is no substitute for a big wheel if you want to go far and fast - and I have done 20 miles on a 20", 24 miles on a 24", and so on. In theory, 1 mile per inch of wheel diameter should be the same effort on any size of uni, but in practice, the bigger wheels go further and faster more easily.

But on very difficult terrain, there comes a point where the “roll over” of the bigger wheel is more than offset by the greater manoeuvreability and control of the smaller wheel. This is especially true on steep sections. Assuming identical cranks, the 29 will be 20% harder to ride up or down a hill, for example.

Then there’s tyre selection. The tyre profile makes more difference than many other factors when it comes to ease of riding. An inappropriate tyre can make your ride more difficult and less fun. There are some very good off road tyres available for 24" and 26" wheels. The selection is more limited for a 28/29.

Awesome, thank you both. Those are the kinds of answers I was looking for.

Recently rode snowdon with two guys on 24", one on a 26" and one on a 29", all running approximately equal cranks. Apparently the technical sections were much easier on the 26" (which is running a gazz and is nearly as big as a 29") and the 29", and certainly faster. However, even with the exiwolf on the 29" it pinch flated when matt hit a slate edge, and is so thin and formless that it fell off the rim when i removed the tube, two guys had to hold the tyre in place on the rim while i inflated the inner tube to hold it in place. So once a decent 29" tyre is released i think it will own, until then maybe the 26" with an enormous tyre would be better.

I’ve ridden 100% 29er for the last few months, and I think there’s very little interesting riding on which a 29er is faster.

Assuming by rocky gnarly muni, you mean riding it in a downhill direction, a 24 or 26 will usually be faster because of the wussy tyres on 29ers. In an uphill direction, 29ers are rubbish to hop, 26 or 24 will be better there.

On singletrack a 29 is quite fast, but not that much faster than a 26, remember it’s only approx 3% faster than a Gazz 26, as the 26"x2.6" and 26"x3" gazz tyres are bigger than 26 inches, more like 28 inches.

I hate to say this, but a big thing that can speed you up on downhills is a brake.

Also, there’s always a bit of relativity here. Personally, when I say gnarly rocky muni, I mean stuff that mountain bikers would describe as being gnarly or ‘really jolly tricky old chap’ for our UK listeners. I wouldn’t ride that on a 29 with short cranks. There’d be no point, it’d be faster on a 26 or a 29 with 150mm cranks, on the short cranked unicycle you’d cane yourself at every little bump. Even a lot of XC routes in rocky areas I’d much much rather have a 26 than a 29*, and I’d hardly ever ride a 29 with short cranks off road. But then I’ve ridden some things described as gnarly that in reality were pretty smooth and easy

29ers are quite nice on really smooth groomed trails though. I just came back from a 50km night ride including 15km of trail riding on a local built trail, which is 100% smooth, like a singletrack crossed with a bmx track, berms on every corner. That was nice on the 29er, cos you could ride up the berms nicely.

The local trails here have a bunch of what are basically staircases made out of wooden steps on them. Every time I get to them on my 29er, it’s totally hold on and pray time, I’m always wishing for the lovely 26 that’s at home in Nottingham.

Joe

*Having said that, I think we shocked some of the people who came along on the last xc ride I went on in the UK, thinking about it, that Ladybower ride is probably somewhat more technical than Snowdon in parts, but still an xc ride for sure.

I ride 29er with 190mm cranks and I can ride anywhere the other Munis ride. Hard to say about speed, I used to ride a 26/175, but never have ridden a 24 with a 3" tire. The 29er is faster than the 26. All this needs to be qualified by saying I’m old and not in the best shape, and I have long enough legs to handle the 190 cranks.
I do agree that we need better tires for the 29er, my friend who builds 29er bikes keeps telling me they should be coming out with real downhill quality 29er tires, but he has said that for a couple of years. I tried the Weirwolf and had it come off the rim twice. I just rode all weekend at Moab on an Exiwolf (with 26" downhill tube) and never got close to a pinch flat, and I’m 15 stone (210lbs).

Using a 26" Dh tube is a good idea, I’ll suggest it to Matt. The tube he has in there has to really expand to fit, when inflating it had to get to a fair pressure before it would contact wiht the inside of the tyre.

A jogger overtook me today. (I’m sure he started sprinting just to catch up and pass me. I caught up with him eventually of course.)
Never let joggers overtake us! :o

I’m wondering about speeds on a 29. I have an AX-29 with 152mm cranks and Exiwolf tire. Riding by myself I tend to go fairly slow… sometimes toooo slow. Daydreaming about this or that and just taking in the sights. Riding with another cyclist seems to help me with speed. As does competing with those joggers :D. Off road of course slows me down.

Fast for me is about 9mph. A police trailer clocked me at 10 a couple of days ago but only for a short time. Once I get a computer I’ll have a better idea and can work on speed more.

Those of you with a 29 please post some of your top speeds (flat smooth terrain) and mention your tire and crank size.

I am not exactly sure what the distance is but to get to campus from my apartment is but to drive it takes me 12min,
to bike takes me 14min,
my 27X1 1/4" (28 1/4" diameter) with 102mm cranks it takes 15 min.
26X3" Gazz (28 1/2" diameter) with 170mm cranks takes me 24 min
Trials with 127mm cranks takes me 30 min.
walking takes me about 45 min.

I know it is not exactly what was asked but I think the difference between the 27 and 26" wheels show that speed on the flat has more to do with tires and cranks than wheel diameter.

ERIC

This is the 3rd or 4th thread about 29ers in the last few months and nothing has much changed, nor can it till a true DH tire is available (reliable sources tell me within a few months). Existing 29 tires are all one-ply and worse than useless for “gnarly, rocky muni.” I couldn’t keep them on the rim, and blew shite out on drops as paltry as 18 inches. Running a thick, 26 DH tube helps, but not greatly.

As is (till the DH tire arrives) a 29er is basically a great freeride option. Semi-advance Muni is possible but feels like you’re using the wrong tool for the job. But once the tire is out a whole new world might open up . . . I hope so since that’s why I bought the 29 in the first instance.

JL

The question was what is the DIFFERENCE in speed, not the RATIO of the speeds. How can you continue to mislead our young like this. The DIFFERENCE in speed is S24*5/24 where S24 is the speed of the 24" unicycle.

That’s my experience in a nutshell. Two blowouts, one that left me walking many miles; the other (mid-Downieville) where I was lucky enough to stretch in a 26" tube. My newer KH rim is great, but the tire just can’t compare to what you can get on a 26" or especially 24" rim. My Kenda Klaw also hates riding on slanted surfaces. It definitely makes the riding more challenging; kind of like the old days when we were on 24 x 1.75 tires. Like he said, it feels like the wrong tool for the job, at least on rocky, challenging trails. It’s much, much better on smoother trails, but if that’s what I’m on I’m going to prefer my Coker.

Plus the last time I took my 29" on a trail (Salmon Falls one week ago) I got nasty poison oak on my arm. Stupid plants… :angry:

okay, mine is more of a 28er…i have a 700c rim with a 28c tire on it. with 125mm cranks, i’ve hit 15.2 mph with the cyclecomputer on it. i’ve since took the computer off, but it certainly felt the other day like i hit a little faster than that.

for comparison, on my 24x3" with 170mm cranks, i’ve hit 14 mph.

thanks for all the replies, i actually ended up getting the KH 29" i made another thread about it…

Today i had the chance to take it up and do some mildly technical riding, I thought it was AMAZING going downhill but had a little trouble making it up some particularly technical sections of rock beds/rock stairs.

Going down was the most fun i have ever had on a trail before.
I dont know if any of you have tried the Kenda Nevegal tire, but i had no problems with it. My only trouble was the wheel slipping out from under me a little bit when i took corners at high speeds.
Other than that im quite certain that i will be able to clear technical uphill sections with more practice.

I don’t mean to accuse you of lying, but with 170mm cranks on a 24", I’m having a hard time believing that you hit 14 mph.

…could it be he means kmph? That would make more sense.

nope nope…definitely 14 mph…cyclocomputer said so.

and it doesn’t bother me if you don’t believe me…but that’s how it was.

Those things aren’t always perfectly accurate. That could be possible though.
I have a hard time hitting 9mph on my 20" with 145mm cranks.

so what is avrg. speed for a 29? say with 125mm cranks?