Tyre question

[rogerzilla]

That's a very interesting question.

Most people think tyres are held in place, against air pressure inside, by the strength of the bead. In other words, they imagine that the bead resists expansion as the tyre inflates. Following on this, they then ask questions about the relative strengths of steel and rope (kevlar) beads.

Tyres are not held in place by the bead resisting expansion. The bead is merely there to position the tyre in a groove inside the rim.

The tyre is designed in such a way that it shrinks with inflation and it is thus held onto the rim with a constricting force. You can cut the bead in several places and provided you didn't damage the casing of the tyre itself, you can safely inflate it and ride it. It will not pop off or explode.

It's tubs that shrink with inflation, although this alone isn't enough to stop them rolling off and they still need glue, shellac or double-sided tape for security. It's true that wired-on tyres will generally stay in place if the beads are cut, since the bead is trapped in position under the hook of the rim (I'll ignore archaic non-hook bead rims). A severe kink in the bead can prevent it seating and then it will pop off - common when people try to coil wire bead tyres for posting and mess it up, or with bad batches of Schwalbe Marathons.

 

[Yellow Saddle]

It's tubs that shrink with inflation, although this alone isn't enough to stop them rolling off and they still need glue, shellac or double-sided tape for security. It's true that wired-on tyres will generally stay in place if the beads are cut, since the bead is trapped in position under the hook of the rim (I'll ignore archaic non-hook bead rims). A severe kink in the bead can prevent it seating and then it will pop off - common when people try to coil wire bead tyres for posting and mess it up, or with bad batches of Schwalbe Marathons.

Clinchers also shrink with inflation, but less so than tubs, since approximately 1/4 of the tyre is removed, had it been a tubular.
For the benefit of watchers, tyre shrink longitudinally because the diameter decreases. They don't shrink because the cross-section decreases.

 

[youngoldbloke]

The conti 4 seasons folders are about 45 or so but with Markdown they are 35 , they are for my GF commuter and she gets around a bit so with the winter on its way she needs better tyres than were fitted by trek when she bought it , I may go with these folders ,

Good price - where are you buying them from?

 

[ozboz]

Good price - where are you buying them from?

Cycle republic or Halfords

 

[youngoldbloke]

Thanks - not available to collect from my local Halfords or for delivery.

 

[ozboz]

Thanks - not available to collect from my local Halfords or for delivery.

That’s a bit odd , if you order them they should price match , if not go to Evans they will

 

[Cavalol]

Meant to check for a thread about folding tyres before I bought some, but got sent a link to Planet X who had brand new Vittoria Morsa 29x2.3 for £20 the pair, plus postage...

That's far too good to say no to, so ordered them and finally got round to fitting yesterday. As someone said, fitting for the first time was a bit hard, because of the way they've been folded I think. Say first time, because I nipped one tube and had it to come off again. Anyhow, they seem mega value for money and a very brief (3 mile) test ride on tarmac today in the rain, they seemed to roll very well and I felt confident in them. Have heard their off road (mud gripping) ability is spot on, had Maxxis before this and had struggled to get any replacements in 2.3. The Maxxis were great off road, really shifted the mud without having to stop to clear it off so I'll be happy if these match or better them.

What's previously put me off folders is the thin walls, concerned about getting pinch punctures on rocks etc, plus all the 'big name' folders I'd seen second hand seemed to have the side wall consistency of damp bog roll and they never seemed to last long. Swapping the Maxxis back to front occasionally saw some pretty good life out of them, getting on for 3 years as it went, though the front eventually succumbed and the side wall went coming home from work one day. Luckily, I managed to put an inner tube patch on the inner wall of the tyre and it got me home with a replacement inner tube too.