TPU Inner tubes

[finch]

pre-preg and modern methods when it comes to epoxy baking and preparing the brake surfaces of carbon fibre wheelsets , at least from reputable manufacturers have advanced significantly. the braking surface will withstand heat in excess of 250degC.  Whether that temperature can even be achieved is another matter.
I realise we're talking about the tubes here and not the rims themselves but the braking performance is very close nowadays to what you get with an alloy brake surface. I'm not sure how effective compared to alloy a carbon rim is in dissipating heat , surely not as good at cooling down as metal ? I'm sure there's probably a study somewhere.
In my opinion , and you do get TPU tubes that are sold "For rim brakes" they'll probably be fine in most situations , however personally if I was intending to ride down some prolonged descents in summer heat I'd probably be switching out my tubes for nice thick butyl ones OR just running tubeless.

[LittleWheelsandBig]

I wouldn't use them with carbon  rim braked wheels....

Carbon is a much poorer conductor of heat than aluminium so less heat will get through the rim wall to the tubes, no?

You are correct. In ancient days, wood rims never had a problem with tubulars coming off on steep descents (unlike aluminium rims) because the heat from the brake tracks was not transferred to the glue. On the other hand, brake pads tended to melt/ char because the heat of braking had to be accommodated only by the braking surface of the pads.
https://wheelfanatyk.com/blogs/blog/advice-for-building-wood-rims notes "Wood won’t absorb heat so the energy of braking can attack the brake shoe. But it won’t be able to migrate to the rim cement and soften it." and "Wood consumes brake pads because it won't accept the heat that braking generates. The pad melts at contact and makes a mess of the rim."

[Frank9755]

If the rims were placed between the tube and the heat source, then yes. But it's the carbon rim itself that is getting very hot. It can't dissipate heat through convection, so heat builds up from prolonged braking. It transfer heat to the rim through conduction.
Wood is a good insulator but friction between wooden sticks has been used to start fires through millennia.

Edited: spelling

It looks like you are misunderstanding that the bit that is getting hot is not the entire rim uniformly but the outside / braking surface of the rim. 

The body of the rim will then conduct heat from the hot outside surface to the inside surface, where the tube is.  An aluminium rim will do this job much more efficiently than a carbon one so will heat up the tube a lot faster. 

[Frank9755]

I wouldn't use them with carbon  rim braked wheels....

Carbon is a much poorer conductor of heat than aluminium so less heat will get through the rim wall to the tubes, no?

In ancient days, wood rims never had a problem with tubulars coming off on steep descents (unlike aluminium rims) because the heat from the brake tracks was not transferred to the glue. On the other hand, brake pads tended to melt/ char because the heat of braking had to be accommodated only by the braking surface of the pads.
https://wheelfanatyk.com/blogs/blog/advice-for-building-wood-rims notes "Wood won’t absorb heat so the energy of braking can attack the brake shoe. But it won’t be able to migrate to the rim cement and soften it." and "Wood consumes brake pads because it won't accept the heat that braking generates. The pad melts at contact and makes a mess of the rim."

Fascinating - so the (non-tube related) problems of carbon rims on descents are nothing new!

[Sergeant Pluck]

In ancient days, wood rims...

When I first joined a cycling club in the early 80s, in Northern Ireland, some members were still using wood rimmed wheels.

[LittleWheelsandBig]

Fascinating - so the (non-tube related) problems of carbon rims on descents are nothing new!

Burning up brake pads and wearing out the rim braking surface = yes.
Deforming rim cross sections due to resin softening = not so much, though wood rims tend to warp a bit, mostly depending on moisture content.

[Cudzoziemiec]

Wood rims pose all sorts of questions: grain, species, a huge variety of appearance v a huge variety of qualities – surely a thread in itself!

[LittleWheelsandBig]

Only a limited number of species were ever employed for wood rims, all laminated AFAIK. Beech is common.

[perdido]

If the rims were placed between the tube and the heat source, then yes. But it's the carbon rim itself that is getting very hot. It can't dissipate heat through convection, so heat builds up from prolonged braking. It transfer heat to the rim through conduction.
Wood is a good insulator but friction between wooden sticks has been used to start fires through millennia.

Edited: spelling

It looks like you are misunderstanding that the bit that is getting hot is not the entire rim uniformly but the outside / braking surface of the rim. 

The body of the rim will then conduct heat from the hot outside surface to the inside surface, where the tube is.  An aluminium rim will do this job much more efficiently than a carbon one so will heat up the tube a lot faster.

With all due apologies, I am just trying to explain why manufacturers of both, carbon rims and inner tubes advise against the use of latex tubes and very lightweight tpu disc only tubes and carbon rim brake rims. If you want to proof them wrong, then please do as you wish and come back here to report your findings.
Alloy will cool down quicker due to convection. Carbon rims will heat up and hold the temperature longer allowing all of the rim to become hotter, outer to inner which may cause latex or very thin tpu tubes to fail.

Enviado desde mi SM-A536B mediante Tapatalk

[Frank9755]

Not quite! Aluminium braking surfaces will cool down quicker by conduction, while carbon braking surfaces will stay hotter. The hotter surface will lose more heat via convection, as the difference to the air temp is greater, but it will still stay hotter because of poor conduction.

I thought your point about what manufacturers say was interesting so I googled it, but found most results said the opposite. For example schwalbe say 'Extremely heat resistant - certified for rim brakes'
https://www.schwalbetires.com/blog/news/innovation/aerothan/

They tested it against various tubes including their own Extralight butyl ones, and found their tpu one performed best for heat resistance from repeated braking. They also say a heat-related failure would be a slow puncture rather than a blow out:

'The dynamic test winner is the Aerothan Tube; and this is the only tube that can withstand a sequence of seven emergency brake applications. All Aerothan tubes are approved for use with rim brakes.
Good to know: Aerothan tubes do not suddenly burst. Any air loss oxxurs slowly as a worst case, while the bicycle normally remains easy to control.'

Other sources said similar. I also googled the heart resistance of butyl vs tpu and got similar figures, with different sources saying 85-110 degrees for both materials.

Based on all of that I would now be more comfortable using tpu tubes than butyl in carbon rims in the Alps. However I would still have some concerns about braking surface overheating, and would be riding tubeless anyway - but with a tpu tube as my back up.

[perdido]

As somebody stated above, tpu tubes rated for rim brakes should be fine with carbon rims. TPU tubes rated for disc only, the extremely light tubes, may be an issue on long descents due to rim heat build up.  YMMV.ĺ

https://www.tubolito.com/product/s-tubo-road-700c/

[Dickyelsdon]

As somebody stated above, tpu tubes rated for rim brakes should be fine with carbon rims. TPU tubes rated for disc only, the extremely light tubes, may be an issue on long descents due to rim heat build up.  YMMV.ĺ

https://www.tubolito.com/product/s-tubo-road-700c/

I wonder how stable those tubes are if the wheel is left in the heat of the sun. You sometimes hear of exploding tyres when someone has left a bike out in direct mid day sun, and regularly hear of tyres popping when left in the boot of a car on a sunny day.

[Hot Flatus]

Carbon rim-brake wheels are a really bad idea on several counts. The actual braking is poor, even more so in the wet. Expensive rims get trashed, and you've the problem of overheating on long descents.

Disc rims are brilliant on all counts.

[finch]

The actual braking isn’t poor at all nowadays

[Hot Flatus]

Better braking= more heat though.

Surely by now carbon rim braked wheels are becoming niche?

[toontra]

First ride with TPU tubes yesterday.  Really nice ride feel even at quite high pressures.

As Finch says braking on modern carbon rims with the right blocks is pretty good - indistinguishable from alloy rims in the dry at least.

[finch]

Better braking= more heat though.

Surely by now carbon rim braked wheels are becoming niche?

I don’t know if I’d consider them niche quite yet. Lots of very well priced options out there, and I imagine lots of people with perfectly serviceable non disc compatible frames. I’d suggest that anyone buying a new bike now would likely be looking at discs just because that’s the standard.
 There’s probably a lot of people who want to eke out as many years as possible out of existing older bikes.
 I have one of each( rim brake bike with carbon wheels and disc brake bike) and like Toontra says the braking in the dry is indistinguishable from rim brakes on an alloy rim and in in many cases considerably better than cable actuated discs.
  For me personally my summer bike never intentionally gets wet , and is as pristine as a 2012 frame can be so although my next summer bike would be disc for obvious reasons, I hope that’s several years away yet. I mean how long does a carbon brake track last ? 20000km ? Double that ?

[toontra]

.. and I imagine lots of people with perfectly serviceable non disc compatible frames.

Indeed.  I'm not in the market for a new frame as mine is as good as you'll get for £3k these days - just no disc mounts.  Then a like-for-like disc wheelset would be another £1.5k.

As with Finch, this is my "best" bike so doesn't get ridden in shitty weather or on gravel.

So carbon rim brakes it is.

[Hot Flatus]

.. and I imagine lots of people with perfectly serviceable non disc compatible frames.

Indeed.  I'm not in the market for a new frame as mine is as good as you'll get for £3k these days - just no disc mounts.  Then a like-for-like disc wheelset would be another £1.5k.

As with Finch, this is my "best" bike so doesn't get ridden in shitty weather or on gravel.

So carbon rim brakes it is.

I've still got a few rim braked bikes that I intend to keep for the rest of my riding life...but I do wonder what the options will be for high quality lightweight wheels etc in a decade (I mean top spec factory wheels etc like Campag Shamals etc) I see them disappearing.

Choice is great, but it is dependent on having a viable market. Recently I was looking for lightweight alloy rims and I'm pretty sure the range we had a decade ago is no longer there.

I've got about 8 bikes, but it is interesting to see the ones I tend to choose to ride. The only rim-braked one that gets used is a fixed. It's not highly conscious calculated thought that goes into.the choosing, but I suspect the thought of 100% consistent braking in all weathers comes into it.

Like you I have a really good rim-braked summer bike, a Look 585. But I also have a Supersix di2 disc. It tends to be the latter I use in part because I know that the Shamals on the Look will be unserviceable by the time the rims wear out. I do think there is a difference in braking in the dry however. 

Of course, rim brakes offer cheaper and easier servicing, even if they eventually cause a need to re-rim a wheel.

[toontra]

After a couple of weeks the tubes are still holding pressure as you would expect from butyl.  Difficult to say with certainty but the ride quality feels smoother.  I'm using the same tyres as always (Michelin Pro4 Endurance).  No p*'s yet so can't comment on repairability.

[zigzag]

after a successful trial of tpu tubes i've got a further dozen, for the bikes that may need/use them. i've been also trialling tubeless tyres without sealant (or with a bare minimum, if they didn't hold pressure dry) for the past year, done the pbp qualifiers and other long rides with tyres like that. the reason behind it is, if there's a puncture, there's no mess to deal with when putting the tube in. if a puncture is small, there's still an option to put sealant through the valve, which is quicker vs inner tube.

looking after multiple bikes with tubeless tyres is a bit tedious, having to track and check when the sealant was last added and topped up. so this new approach works quite well for me and tpu tubes are a welcome addition to the system, along with the tyre plugs, sealant, valves/cores, glue, patches and boots.

i'd still be running 50-60ml of sealant for very important rides/races where stopping is best kept to a minimum.

[finch]

I’ve got a bike that has carbon wheels & brake surface along with caliper brakes - to be fair they are the new ultegra brakes which are very very good the stopping power and modulation are both , in terms of what you hear about the performance in this context , astonishing. It’s very easy to lock up both wheels. Obviously this performance is diminished a lot in the wet , which to be fair this being my summer bike hasn’t happened very often.

I have another bike that has cable actuated hydraulic discs , they replaced pure cable discs which were pants ( I’m 90kg ) I’ve tried as many things as my budget will allow , new cables , compressionless housing , new discs and pads of a material specified for the discs. I’ve made sure the pistons are clean and work properly, the brakes are properly aligned and the lever throw is both good and responsive - I am in no position to spend anything more , in fact I’m really struggling at the moment and here’s the thing - the braking is objectively terrible - the bike slows down a little but it just doesn’t stop - there’s no “bite” and a lock up would be impossible - I’m starting to think that it’s actually dangerous and I’m not confident on the bike. There’s absolutely no way that I can meet the ultra prohibitive cost of hydro shifters and calipers so I’m just going to have to retire the bike for the time being - it’s honestly that bad !

My MTB on the other hand has “nutt” hydros which I’ve never heard of before and stops near instantly - but MTB hydros are super cheap compared to the road stuff which is quite the opposite

So going back to some of the stuff that was being discussed earlier - I’m so much more confident with “good” rim brakes over “crap” disc brakes - even on carbon rims - I have no experience of road hydros to compare this to so my ostensible work horse bike is going in the shed not to be used until I can do something about it which is super depressing

Also i remember in the 90s , pros descending on early gen Boras with a carbon brake track and can’t recall anyone suffering because of it or blowing a tube up

[Lightning Phil]

I’ve got a bike that has carbon wheels & brake surface along with caliper brakes - to be fair they are the new ultegra brakes which are very very good the stopping power and modulation are both , in terms of what you hear about the performance in this context , astonishing. It’s very easy to lock up both wheels.

Astonishingly bad modulation, if you are finding it very easy to lock up the wheels.

[toontra]

The wheels I've put the TPU tubes in are carbon rim brake (Progress A-Prime).  They are my first set of fully carbon wheels.  I was put off for years by worries about braking.  All I can say is, with SwissStop Black Prince blocks, braking is as good as any ally-rim wheels I've ever used and better than some.  Can definitely lock up if applied too forcefully (don't ask) but really good modulation.

Done a few longer rides and and really liking the weight/comfort of the TPU tubes.  Carrying a butyl and patches as spares though.

[finch]

I have to say my experience had been the same and MTB aside my experience of discs had been rubbish - that being said I won’t argue that road hydros are awesome as I’m sure they are - I’m just priced well out of them trying to eke out as many years out of my bikes as I can

The TPU tubes combined with my set up have also been great and carrying spares takes up bigger all space - they do get well deformed though so reusing them in a new tyre or wheel would , I imagine , be tricky