High Speed Wobble

Hey all,

Ever heard a hissing sound about the same time as your uni starts to wobble at 15mph?

Is there a record for the fastest UPD from 15mph?

Fortunately, I got stopped without testing the unibike’s forward dismount properties.

Greg, you got a name for this stunt?

No 25k time today, since the unibike pulled this stunt at the 20k point.

I hope you all had a better day, with a lot less walking!

Slapping the cat. That’s what makes that hissing noise.

Re: High Speed Wobble

How vexing. You must have been quite disappointed. I know I would have been.:frowning:

No disappointment at all. I was just happy as hell to be able to dismount in one piece. I was supposed to be in Florida fishing anyway, but had to return a day early because of that work thing. I got some good exercise anyway. Half pedalling - half walking.

This makes the third tube in a year (the other two were less exciting since I had a front wheel on board) that has separated from the valve. Ya know, that expensive/high tech/extra thin/all steel/valve core locking/requires an adapter or special tire pump type of valve. I think I’ll drill the rim and go back to the $3.95 special with a large rubber valve stem that lasts for years.

Sounds like the tire might be rotating on the rim, thus pulling on the tube. Try: (1) powdering the tube and the inside of tire to minimize the pull the tire can place on the tube, or (2) change the tire to one that fits tighter on the rim, or (3) gluing one side of the tire to the rim, or (4) all three.

In addition, be very careful upon installation to avoid tweaking the valve stem.

Something else to try – use a higher tire pressure to lower flex (which aids tire creep) and to increase the pressure against the rim walls.

Also, be sure not to over-tighten the little Presta locking nut that sits on the spoke side of the rim wall. Just barely finger-tight is sufficient. Otherwise the nut can pull the valve up into the rim where it will experience unwanted forces.

Finally, be sure the valve hole is nicely bevelled and smooth. This is supposed to be done by the wheel-builder but is often neglected.

Thanks for the help U-turn,

I’ve eliminated all of the above causes. The tire is not moving. Every time, I’ve stopped before it was completely flat, and the valve was still straight and loose. I have run without valve nuts for years, so if the tire slips a little, it becomes obvious before the valve moves enough to get damaged. The same was recommended when I changed to these new tubes. The tire bead was glued on one side - recommended after the last flat. Pressure was 60psi. Tire fits tight. Valve hole had a nice bevel when I got it. Next?

It appears that the rubber around the valve is breaking its seal due to expansion under the high pressure.

Maybe these tubes weren’t designed to support 200lbs? The weight is normally expected to be divided between two tires. I wonder about the life expectancy of these tubes on a road b*ke with a 400lb rider.

I might try one more if they give it to me (and offer to pay my dental bills if I’m not so lucky next time).

unibiker

maybe your problem is heat from riding the brakes :thinking:

Maybe you should have gone fishing in Florida? I’ve been doing a far bit of fishing for snapper, snook, and reds lately. :slight_smile:

Jeff,

Have you got any bigger photos of your unibike and especially you riding your unibike? It seems really interesting. Are you using a freewheel hub and using brakes?

Thanks,
Andrew Carter

Good idea, Jag. The other idea I had was to use a larger (wider) tire for more air volume. And one more - is there a thornproof available with Presta valve? I can’t remember.

www.airfreetires.com

>Is there a record for the fastest UPD from 15mph?

is it possible to go faster once u r travelling at 15 mph?
:wink:

Andrew,

You arrived after the unibiker pics came out. I am sure other new members are also curious. Jeff put some pics out there. Here is the link

http://www.unicyclist.com/gallery/albun01

If that doesn’t get you in, go to the gallery and do a search on unibike or unibike pics, that will get you to some other pics that you can enlarge.

Jagur,

I’m not riding the brakes enough to get the rim hot. Especially during the TT rides, I keep it forward of the balance point most of the time so I don’t waste speed and energy. As an indication of the small amount of brake drag, I’m still using the original brake pads which are over 15 years old. Yeah, the unibike is old, and heavy. That 25k might be a little faster with an aluminum frame.

NSX,

I hear fishing is better than unicycling for neck healing! The crew caught a lot of fish without me, near Sarasota.

Andrew,

Yes, I’m using a freewheel and brakes. The link that Teachndad provided (thanks Rod) should help if you haven’t been there. You can zoom in twice for a quite large view, however I’ve had the same ‘small picture’ comment often, by those not familiar with the zoom process. That’s why I added the instruction to the title. I’ll probably get some more pictures while I’m on vacation anyway. Judging by the weather reports, the unibike (and myself) will likely appear a little frosty!

U-turn,

Don’t want the volume. The steering is better with high pressure. So are the 25k times. But I’ll check that link for the tubeless tire.

Gild,

Not if I’m sliding on my teeth! Namaste! (I hope that means something good)

After looking at the pics, it looks like you couldnt ride the brakes enough to heat the rim because it’s not running rim brakes? or doesnt the disk work?

Re: High Speed Wobble

“GILD” <GILD.daimm@timelimit.unicyclist.com> wrote in message
news:GILD.daimm@timelimit.unicyclist.com
>
>
> is it possible to go faster once u r travelling at 15 mph?
> :wink:
>

Mmmm, let’s see, a forward speed of 15 mph combined with a downward (UPD)
speed accelerated by the pull of gravity, wouldn’t the resulting velocity
at a angled down vector be a little faster than 15 mph? : -D

Doug

Max,

The disc was a recent add-on, operated by a shift lever, for slowing the descent on steep downhills. A rim brake was standard equipment. I added a second rim brake years ago when my distance became limited by a loss of brake control due to hand fatigue (the same problem I had on the downhills before adding the disc). A close-up of the gallery photos should show all three.