Small Wheel Blow-outs

[torquerulesok]

I'd surmise the cause of the blow out was incorrect braking technique.

Last October I cycled across the Snake Pass and Holme Firth in the Peak District on my Brompton (16" wheels) with no problems at all on both (long) downhills stretches. Maxed out at 40mph.

Cadence braking (short, sharp low frequency pulses with front and rear brake simultaneously) worked well. The front rim was hot to the touch at the bottom of the Snake Pass but certainly did not radiate heat that could be felt from inches away.

I was much more bothered by the lack of low gears on the uphill stretches. I'm no longer fit enough to push a 40" gear up a 4 mile long 13% incline

[Mick F]

I'd surmise the cause of the blow out was incorrect braking technique.

Nowt wrong with my technique for going down hills generally.

It wasn't the hill, it was that specific hill. If I could have gone faster, I could have braked correctly.
I couldn't see more than 50yds, and sometimes as low as 10yds, plus it was up to 25% for much of its length.

Knowing what I know now, I'd have gone very slow maybe walking pace .................... or used the main road instead where I could have been whizzing along at 40mph only braking for the corners.

[pwa]

I'd surmise the cause of the blow out was incorrect braking technique.

Last October I cycled across the Snake Pass and Holme Firth in the Peak District on my Brompton (16" wheels) with no problems at all on both (long) downhills stretches. Maxed out at 40mph.

Cadence braking (short, sharp low frequency pulses with front and rear brake simultaneously) worked well. The front rim was hot to the touch at the bottom of the Snake Pass but certainly did not radiate heat that could be felt from inches away.

I was much more bothered by the lack of low gears on the uphill stretches. I'm no longer fit enough to push a 40" gear up a 4 mile long 13% incline

You are dead right to say that letting the speed build up and keeping your hands off the brakes, and confining your braking to short spells of hard braking left as late as possible, is the best way to keep rim temperature down on hills where you can do that. But you cannot do that on all hills. There are hills where because of the steepness and twistiness there are no straights where you can let the bike go. I think MickF's hill would have been like that.

[Mick F]

The issue has gone completely.

How?

I now blame the bendy Tektro R539 brakes that were fitted, as I had to squeeze terribly hard to brake enough. This generated massive heat.
Bendy dual pivots - viewtopic.php?f=5&t=115514

I now have some Shimano BR650 brakes and the difference is astounding.

I was down in SW Cornwall earlier in the week and was up and down horrendously steep and restrictive hills - Helford - Manaccan - Porthallow - Porthoustock - Coverack etc etc etc. At the bottom of one hill, and then another, I stopped hard and felt the front wheel expecting it to be very hot ........................... but it wasn't, it was just nicely warm.

This means that the bendy brakes needed more force to hold back the speed, and the new brakes were more efficient and didn't need constant braking. I could let go, then brake hard. The bendy brakes weren't effective enough and constant braking was required.

[gregoryoftours]

You can get heavy duty 20" inner tubes for bmx. Might be a dog to ride though.

[9494arnold]

Just seen some original Scott Mathhausers on Fleabay item 192680385746 with the disc cooling I had in the back of my mind.

[Brucey]

You can get heavy duty 20" inner tubes for bmx. Might be a dog to ride though.

There is another problem too; the tyres usually fitted to a TSR are either 28-406 or 32-406. It happens that most of the rim-tyre combinations in these sizes seem to be pretty tight, and a big fat BMX tube is just going to hamper the bead from getting in the rim well where it needs to be. In practice this means that getting tubes such as those into that type of wheel is more awkward than it needs to be.

FWIW IME a Schwalbe #6 tube is normally the best fit in a 28mm tyre and the next size up can work OK in a 32mm.

cheers

[recumbentpanda]

Hmm, not sure about the physics of MickF’s explanation for the cooler running of his new brakes. Squeezing force at the rim doesn’t care how you got it there, whether through bendy calipers or stiff ones. Much more likely explanation for the improvement is a more efficient and cooler running block material, imho. All retardation must turn motion into heat through friction, but some materials are better at dissipating that heat than others.