Fat tire and body twist

This weekend, I put a 24x2.6 Duro downhill tire on my Schwinn, and took it out
for a ride. With my previous tire, a 24x2.125 Specialized bmx knobby, I felt
pretty competent on the mostly-flat singletrack where I ride. But the whole time
on the new tire I had a nasty case of body twist–I felt like I had to twist
around to the right almost all the time. Part of the problem was that my rim was
slightly out of true, and the big tire seemed to amplify that problem somewhat
more than was noticeable with the previous tire. It felt like the seat was
sitting a couple of inches to the right of the uni’s center line or something,
and so I had to lean/twist to compensate. I think there are three possibilities
here–either the out-of-true rim was messing me up (I’ve since trued it), the
big tire is just different and I have to get used to it, or I’m barking. Any
other “I switched to a really fat tire and …” stories to share? BTW, that tire
made some pretty rocky sections seem about like pavement–amazing.

Peter Kittle Department of English CSU, Chico Chico CA 95929-0830 ph:
530/898-5305 fax: 530/898-4450 email: pkittle@csuchico.edu www:
http://www.csuchico.edu/~pkittle

RE: Fat tire and body twist

> Any other “I switched to a really fat tire and …” stories to share? BTW,
> that tire made some pretty rocky sections seem about like pavement–amazing.

Try letting some air out. The fatter the tire, the less air you need.
John Hooten had this problem when he went to the 2.6" Gazzaloddi, and it
fixed him up.

I have found there are some knobby tires that are fine on pavement, but don’t do
much on the dirt. There are others that are great in the dirt, but terrible on
pavement (always pulling or twisting). Brett Bymaster tried lots of tires that
had too much “corner” on them. We unicyclists don’t need so much tread on the
edges of the tire, because we don’t corner like bikes. Most seem to prefer a
rounder section tire.

So try messing with the air pressure and see what happens. If you’re used to
riding on “regular” unicycle tires, you may be surprised at how little pressure
you need on the fatter ones.

Notice I’m not giving out numbers. These are factors of rider weight, riding
style, and terrain, so you’re on your own…

John Foss, the Uni-Cyclone http://www.unicycling.com

“Oh dear! I think I broke something.” - Kris Holm, talking not about his body
parts, but about the edge of a bar-b-que grill he had just been riding on

RE: Fat tire and body twist

> > Any other “I switched to a really fat tire and …” stories to share? BTW,
> > that tire made some pretty rocky sections seem about like pavement–amazing.
>
> Try letting some air out. The fatter the tire, the less air you need.
> John Hooten had this problem when he went to the 2.6" Gazzaloddi, and it
> fixed him up.
>
Yeah, I tried that midway through the ride–from about 32 psi to start with to
probably 20-22. This made the tire feel incredibly good and smooth, but at the
same time really increased the body twist.

> I have found there are some knobby tires that are fine on pavement, but don’t
> do much on the dirt. There are others that are great in the dirt, but terrible
> on pavement (always pulling or twisting). Brett Bymaster tried lots of tires
> that had too much “corner” on them. We unicyclists don’t need so much tread on
> the edges of the tire, because we don’t corner like bikes. Most seem to prefer
> a rounder section tire.
>
The tire is pretty round in profile. But it’s a cheapie, and I noticed that even
though I’ve got my rim pretty much true, and the tire is seated well in the rim,
the tire itself isn’t perfectly round or true–it has a couple of high spots,
and some places where it inexplicably bulges left or right. I guess I got what I
paid for–I’m guessing that quality control in the higher end DH tires is
probably a lot more stringent.

Peter

RE: Fat tire and body twist

> Yeah, I tried that midway through the ride–from about 32 psi to start with to
> probably 20-22. This made the tire feel incredibly good and smooth, but at the
> same time really increased the body twist.

Woah, that’s pretty low. Maybe try putting some more in?

> guess I got what I paid for–I’m guessing that quality control in the higher
> end DH tires is probably a lot more stringent.

When we were riding in Santa Cruz the other weekend, Kris Holm recommended a
tire called the Intense, by Vtech (or the other way around). He didn’t know how
much they cost, because I think one of the perks of doing what he does is
getting free stuff. But he liked it better than the Gazzo, saying it had much
stronger sidewalls allowing hopping up steeper things. I hope John Drummond can
get some of those and we can try them out!

John Foss, the Uni-Cyclone http://www.unicycling.com

“Oh dear! I think I broke something.” - Kris Holm, talking not about his body
parts, but about the edge of a bar-b-que grill he had just been riding on

Re: Fat tire and body twist

Are you perhaps pedaling harder with one foot than the other? I know that I
sometimes have a tendency to pedal harder with my right foot than with my left.
I also have a tendency to use my right foot more for control (back-pedal
pressure, etc.). When this happens I end up having a case of body twist to keep
going straight. When I notice myself doing this I concentrate on pedaling
evenly with the same even pressure with both feet and I end up straightening
myself out.

I’m not sure if the body twist problem happens more with fat tires or not. I
test-rode a Telford with the 2.6" Gazzaloddi at the Muni Weekend and didn’t have
any problems at all with body twist. I just remember having a lot of fun with
that fat tire and wishing I had one.

john_childs

>From: “Kittle, Peter” <pkittle@csuchico.edu> This weekend, I put a 24x2.6 Duro
>downhill tire on my Schwinn, and took it out for a ride. With my previous tire,
>a 24x2.125 Specialized bmx knobby, I felt pretty competent on the mostly-flat
>singletrack where I ride. But the whole time on the new tire I had a nasty case
>of body twist–I felt like I had to twist around to the right almost all the
>time. Part of the problem was that my rim was slightly out of true, and the big
>tire seemed to amplify that problem somewhat more than was noticeable with the
>previous tire. It felt like the seat was sitting a couple of inches to the
>right of the uni’s center line or something, and so I had to lean/twist to
>compensate. I think there are three possibilities here–either the out-of-true
>rim was messing me up (I’ve since trued it), the big tire is just different and
>I have to get used to it, or I’m barking. Any other "I switched to a really fat
>tire and …" stories to share? BTW, that tire made some pretty rocky sections
>seem about like pavement–amazing.
>-----------------------------------------------------------
>Peter Kittle Department of English CSU, Chico Chico CA 95929-0830 ph:
>530/898-5305 fax: 530/898-4450 email: pkittle@csuchico.edu www:
>http://www.csuchico.edu/~pkittle
>-----------------------------------------------------------
>
>


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Re: Fat tire and body twist

Peter,

    I ran the Gazzo 3.0 for a while and experienced a slight pull too.
    After inspecting the tread I noticed it was not symmetrical about a
    center line running around the perimeter of the tire. It appears those
    tires are molded from a mold that breaks in the middle. The center knob
    cativies spanning the mold junction appeared to be twisted slightly
    causing the front of the center knobs to contact the ground out of
    square. Also knobs working towards the side walls didn't run on a line
    perpendicular to the center line either. Like a fan blade, reversing
    the tire on the rim won't change anything. I'm speculating this
    non-symmetrical tread pattern would cause the tire to twist just a bit.
    On a two wheeler this small twisting torque would go unnoticed. Whether
    this is a sloppy molding job or deliberate I can't say. If your 2.6 is
    made the same way, letter air out may not help much because the side
    knobs will pull. If a unicycle had a compensation adjustment that
    allowed one side of the axle to be moved slighlty forward of backward a
    constant pull could be trimmed out. Presently I don't think this
    adjustment is available on any unicycles. For now it's best to
    experiment with different tires/pressures to find the one you like.
    None will provide perfect performance in all situations I'm afraid.
    Good luck.

“The Muniac”