Mountain Biking - I popped both of my tubes today! woohoo!

Its actually the first time that Ive ever popped a tube. So Im 3/4 through the trail and Im going pretty fast. Well, theres a turn up ahead but a bush covering whats behind. Unfortunately I didnt see the very sharp rock ahead. Wham! I hit it pretty hard. Hard enough to pinch flat both of my tubes! Luckily the tires arent damaged, from what I can see at least. Looks like a pump and a flat repair kit is a good investment :)

Is there a way to prevent pinch flats? I was considering getting some Maxxis tires that are kevlar beaded. Whatdya think?

prevent pinch flats, tubless tires? JK, higher tire pressure may help.

Pow Pow!!http://www.143gifts.com/images/newborn/baby01-l.jpg

Originally posted by troie
Is there a way to prevent pinch flats? I was considering getting some Maxxis tires that are kevlar beaded. Whatdya think?

Kevlar beads do nothing except make the tire lighter and foldable. Kevlar belts helpt with punctures, not pinch flats.

As Mr. Snax points out, higher pressure is the best defense against pinch flats, right after not hitting rocks. Also not running tires that are too wide for your rims.

RichC

So getting a better tire would be worthless?

Klein, are you serious about the powder?

It's still possible to pinch flat a tubeless tire.. just alot harder. But I've done it. Came down hard from a jump on top of some majorly sharp rocks. Left me stranded about a mile from the trailhead. I was pissed.

Jim, just when you feel you have outsmarted that roadrunner, the boulder lands on you!!

Oh, and more finesse helps with not pinch flatting, even if you dont take a the cleanest line.

Im all finesse baby :D

Originally posted by troie

Klein, are you serious about the powder?

Talcum powder will help the innertube slide around more easily inside the tyre casing and should always be used if possible when installing a new tube. Since you typically air down a mountain bike tyre on the trails, having a generous amount of talcum powder inside helps to keep the tube from bunching up and pinch-flatting.

Jobst Brandt, author of "The Bicycle Wheel," has this to say on the subject of powder in the rec.bicycles FAQ (http://draco.acs.uci.edu/rbfaq/FAQ/index.html):

Subject: 8b.11 Talcum Powder for Tubes and Tires
From: Jobst Brandt <jobst.brandt@stanfordalumni.org>
Date: Tue, 04 Nov 1997 16:54:17 PST

> I've been told since my first bike that I should liberally dust the
> tube in talcum powder before installing it. I've believe that this
> may have reduced the number of flats I've had recently.

Talcum is one of the more durable urban legends. There is no benefit
in putting talcum or substitute powder on a tube or in a tire. The
practice has come to bicycle tires the same way tire treads that are
miniature replicas of automobile treads have... if it's good for cars,
it must be good for bicycles. Trucks (and formerly cars) use talcum
or graphite powder between tire and tube, because without it, the two
can vulcanize from the heat of rolling. This often makes tube removal
destructive, leaving tube fragments stuck in the tire casing.

Bicycles do not generate enough heat to vulcanize tubes, so they can
be removed from the tire without problem. Other than that, talcum has
no effect on punctures other than to release air faster when one
occurs. A tube stuck to the casing will retain air for a considerable
distance after a thorn penetration because the thorn that penetrates
plugs the casing hole leaving the tube hole with no outlet. This is
especially true for snake bites. I have found such flats the day
after when they have gone flat over night. Without powder, a tube
will stick adequately to most clincher tires in about 100 miles.

Corn starch is no better than talcum powder, the only difference being
that it is water soluble, but then who cares. Talcum also cakes up
when wet, although it doesn't dissolve.

A tube cannot move in a tire when inflated, regardless of what powder
is used, because, no translational forces exist, on top of which the
holding force between tube and casing is large. That talcum prevents
damage when mounting a tire is also not the case, because the pinch
occurs when the last part of the bead is being popped onto the rim.
This can cause a pinch with or without a tire iron, and powder will
not protect a tube from lying in the gap if it hasn't been pushed into
the tire adequately.

The reason tubes have talcum powder inside is that in manufacture,
they become hot enough that, otherwise, they could become inseparably
stuck when folded. That is why most butyl tubes have talcum inside.

Thx Rich, very informative :)

First of all, let me say that I have always respected Jobst a lot but a good part of me thinks he has never radically aired down extremely wide offroad tyres before.

I was thinking the same thing Khoun...the thing that gave it away was his mentioning

"Trucks (and formerly cars) use talcum or graphite powder between tire and tube, because without it, the two can vulcanize from the heat of rolling"

I don't know about anyone else but I have had my tube merge with my tire before...let me tell you it sure does suck for the tire when I have to rip the tube out...I don't use talcom powder but that is as good a reason as any (instead of replacing the tire). :)

It seems like the tube only gets stuck to the tyre when running at high pressures though. On mountain bike tyres, pressures rarely go above 40 psi, right? Esp. on very rocky trails. The slicks I run tend to stick themselves to the tubes because I run them around 90-100 psi. I have to rip them off everytime I change the tyres.

I guess talcum would work for the slicks, maybe. :confused:

High-volume tires will increase your pinch-flat resistance because it's more difficult to collapse them all the way to the rim at a given pressure. I'm prone to attacking rockfields at high speed rather than attempting to pick my way through them slowly, and let me tell you... big tires are my friend. With 2.1" tires, I need probably 55psi to be able to wantonly blast my way over rockbeds and not risk a pinch flat. The old Z-Max WCS 2.35" was MY tire, only 600 grams and very difficult to pinch-flat. Too bad they don't make those any more... I've got only one left :(

I'm pretty set on a pair of these for my next pair of off-road tires: http://www.wtb.com/mutanoraptor_24.html Look at the volume-to-weight ratio on that tire! :love: Bigger and lighter than my Z-Max WCS 2.35".

Originally posted by Maelstrom
I was thinking the same thing Khoun...the thing that gave it away was his mentioning

"Trucks (and formerly cars) use talcum or graphite powder between tire and tube, because without it, the two can vulcanize from the heat of rolling"

I don't know about anyone else but I have had my tube merge with my tire before...let me tell you it sure does suck for the tire when I have to rip the tube out...I don't use talcom powder but that is as good a reason as any (instead of replacing the tire). :) Baby powder = good Stuck together tube and tire = bad 'nuff said

mechbgon, whats the cost of that tire?