I did up a spreadsheet and colored in the similar values for easier visualization of similar gain ratios. The comments at the bottom are just what I think the various ratios would be suited for. The chart also demonstrates the jump in wheel sizes between 29 and 36. I wonder if that gap will ever get filled?
I used nominal values for the wheel sizes and a gearing ratio of 1.5 for the geared numbers but it should be good enough to give people a good idea of what kind of gain ratio they have in various setups.
The other factor that needs to be included is the total weight of the rider and the unicycle. I believe this could affect the TGR dramitally but can be included in the calculation.
This is super. I was doing exactly the same thing the other day to figure out what crank length I should put my my ungeared 36 to get some practice for when I get my high-geared machine together. Good to know there’s a term for it, it’ll make talking about speedy machines much easier.
Of course weight does matter, but if you want to compare how would you feel on the various unis, then the weight is more or less constant.
If you want to compare various persons, then TGR, anyway, does not take into account the personal preferences eg in crank size, so it will not be a full comparison. Then also the raider height matters especially for bigger wheels. I think it is better to keep the parameter simple.
Unfortunately I don’t think that will help much. You can fit cranks which will give a similar level of torque, but the difference in length means you use very different parts of your leg muscles with a geared uni. Getting good at spinning tiny cranks is a specific skill, but guni riding is another kettle of fish. I definitely can’t go up hills in high gear on my g36/150mm which I can do with my ungeared/100mm.
The best practice/training to prepare your legs for guni riding is a bike. That will have more similar length cranks, and you can push harder in higher gears on them than on any short-cranked ungeared uni.
The coloured chart is great. Thanks Eric - it’s an easy way of browsing TGRs.
The general public supposedly associates unicyclists with clowns, whereas I have always associated unicyclists with nerds. this fantastic post amongst several others this week alone has vindicated my thinking. Wow. I love it!
What? Oh, you’re new here. Yup, it’s a nerd-o-rama! I especially like when people bring in physics equations that tell you something, but usually not in relation to the realities of the situation under discussion…
I think riding a GUni in high gear has more in common with riding a bike in terms of leg load than it has with single speed uni regardless of crank length.
I have a 26" Nimbus with square tapered 152mm cranks.
I noticed in my garage I have a beat up punk/runt bike like this one with 92mm cranks.
If I succeed in putting the 92mm cranks on my nimbus my TGR will change:
152mm TGR = 2.17
92mm TGR = 3.59
That would give me a TGR similar to a Coker with 130’s.
TGR is the “speed potential”. So I should have the potential to go as fast as this Coker.
I’m excited about trying this. Will it be a no brainer to just ride and be fast. Or is there some lack of technique that will keep my “potential” from becoming realized?
Gain ratio ( I am not a fan on the term TGR since most of us don’t have gears) is only one factor on how fast you will go.
When riding a 29 with 102s I can get top speeds about the same as my top speeds with a 36 and 127s (30-35km/h) but I feel like I have more control with the 36 and am able to keep a higher average speed with the larger wheel and longer cranks but similar gain ratio.
I crashed pretty hard a few years ago using 102mm cranks and no-loner feel comfortable on anything shorter than 114s. Probably just a mental block and I will have to put some short cranks on a 20 to get over it.
You can continue to use the term TGR and secretly think Total Gain Ratio.
I use “gear” also as reference to the “gear” resulting from the crank being shorter than the wheel radius. People on this forum have called this “gear” for years. Looking at it that way, every unicyclist rides geared
A 26" with 92 mm cranks is still a reasonable unicycle. You will need quite a bit of training to acquire the technique of spinning really fast (meaning it is not a no-brainer), but then I think you would be almost as fast as with the same amount of training on a Coker with the same TGR.
(BTW, how did you calculate 130? My calculator gives 92 * (36/26) = 127 mm.)
Yup, lots of nerds here! I’m not a math nerd at all, but there sure all nerds of all types here. I might be a nerd with religion and philosophy and just knowing lots of random stuff. Math is definately not my forte.
Thanks for posting that Sasquatch! Just thinking about this the other day! Glad i checked out what this thread was about.
I didn’t calculate 130, I just moved over in the chart and estimated.
When I went to take the cranks off the runt bike, my 6 y.o. daughter put up a stink. Despite the rear tire being worn and pretty much busted, she still rides it sometime; earlier that day in fact.
And I don’t know if I could remove the cog off the one side and ever get it back on again. So I’ll have to investigate it further when my 6 y.o. isn’t around.
Unless there is clearance issues with your frame (unlikely) you could just ride with the chainring on there.
Repurposing is where it is at, you might have to send the kid to Grandmas place while you have your fun though.
If I were to buy cranks to make a fast 26 I think it would be in the 100-115 range. 92 might be a bit extreme (but when that’s what you got, that’s what you got)
