Sun DoubleWide Request

Would someone with a unicycle with a 2.3", 2.6", or 3" MB tire (of any type) mounted on a 26" Sun DoubleWide rim be willing to take a few measurements for me? Please contact me by email if you please (see my profile for the email address). The rim is the most important ingredient. It would help if you are between 160 and 180 pounds or can get there by holding weights, and you need to be able to set your tire pressure to certain values.

Actually, if you can get between 160 and 200 pounds it would be fine.

Re: Sun DoubleWide Request

I have a Sun Big Fat Mammoth rim on a 26". Will that work?

I’ll have to go get some helium balloons to get down to 200 though.

Doug

“U-Turn” <U-Turn.cvrlz@timelimit.unicyclist.com> wrote in message
news:U-Turn.cvrlz@timelimit.unicyclist.com
>
> Would someone with a unicycle with a 2.3", 2.6", or 3" MB tire (of any
> type) mounted on a 26" Sun DoubleWide rim be willing to take a few
> measurements for me? Please contact me by email if you please (see my
> profile for the email address). The rim is the most important
> ingredient. It would help if you are between 160 and 180 pounds or can
> get there by holding weights, and you need to be able to set your tire
> pressure to certain values.
>
>
> –
> U-Turn - Definitely not one of the Elite
>
> ~~~~~~~x (ouch)
> ------------------------------------------------------------------------
> U-Turn’s Profile: http://www.unicyclist.com/profile/691
> View this thread: http://www.unicyclist.com/thread/21148
>

Thanks, Doug, but it’s the DoubleWide I’m interested in.

I’m currently using a Kenda 2.6 w/ standard weight tube on a 26" doublewide. I’m a bit light at 135lbs and don’t have an accurate pressure gauge but what is it you’re after?

Cheers, Greg

I’m after data of tire spread (in cm, at the ground with unicycle weighted by rider in those weight limits) versus tire pressure at the following tire pressures (in lbs): 5, 10, 15, 20, 25, 30, 35. In order to get tire pressure precisely enough you’d probably have to use a separate tire gauge obtainable at a bike shop.

Unless you can get your seat weight up to at least 160, Greg, your work would not be of any help to me. You might be able, though, to hold 25 lbs as you sat on the uni…

> I’m after data of tire spread (in cm, at the ground with unicycle weighted by rider in those weight limits)

Measured where? Contact patch? Outside limit of knobbies?

On what surface? Pavement? Grass? Sand?

Cheers, Greg

Measured at the widest point of the contact area, viewed from above, to imaginary curves connecting the outermost points of the knobbies on each side. A nice hard surface such as wood, concrete, asphalt, or the top of my head would be best.

tire data for Uturn:

5 degrees celcius
~5 metres above sea level
Kenda Kolossal 26"x 2.6" (~50% tread)
26" Sun Doublewide
rider weight - 170lbs I bulked up with dive weights :wink:

Measured using 1 1/2" high blocks placed in contact with the tire at the point of contact with the ground. Blocks hit the side lugs of the tire at all pressures. The side lugs did not contact the ground - solid surface - until the pressure was dropped to 15 lbs. The pressure guage I borrowed didn’t read down to 5 lbs so you’re on your own for that one.

35 lbs - 2 23/32"
30 lbs - 2 23/32"
25 lbs - 2 23/32"
20 lbs - 2 25/32"
15 lbs - 2 27/32"
10 lbs - 2 31/32"
5 lbs - ?

Cheers, Greg

Very interesting… So the change was only 1/4". Note also that the overall tire width at its widest point went from 2.7" to almost 3.0". But the footprint changed even more dramatically because above 15 lbs the side lugs lifted off the ground. This would cause the footprint (on hard ground, at least) to pop way down - an inch or more narrower, as pressure increases above 15 lbs. In soft snow, then, for that combination, one would want to run at about 10-12 pounds pressure to ensure that all the lugs were down with pressure, thus producing traction. This correlates nicely with what the icebike website says.

http://www.enteract.com/~icebike/Default.htm

The rim’s outer width is 1.8" (the widest I’ve heard of, including Snow Cat) so the overhang is 0.6" per side, or a total “unsupported” width of 1.2/3.0*100 = 40%. The same calculation for the BFR gives the inverse, or 60%, assuming that the static behavior on hard ground is the same.

Thanks for your help, Greg!!! I’m working on a snow uni and this information will be very helpful. Please let me know if I can return the favor sometime.

If anyone with a 3" tire could take the same data it would be really cool.

Snow uni. Sounds like an interesting project.

What is the main concern? Traction? Floatation? Room for tire chains? or ?

I rode the Kenda tire in snow last season and had no problems (related to the tire anyway). The snow was about 12" deep over hard surfaces. Floatation wasn’t necessary. I was running about 10-12 psi. Traction wasn’t a problem either. I haven’t got the legs to do a uni ‘burn out’. Do others? Didn’t get to ride any steep hills either but there was enough snow that the hills I did ride didn’t pose a problem for braking.

Cheers, Greg

10 cm of snow and still accumulating :smiley: I’m very interested in the snow muni project (SMuni?, SUni?). Keep us posted.