Tubes crr comparo - latex crushes the competition

Discuss light weight issues concerning road bikes & parts.
RocketRacing
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by RocketRacing

hambini wrote:
Tue Aug 20, 2019 1:56 pm

I'm 72kg so 160lbs

On my TT bike which has a 23 front and 25 rear, I go for the max sidewall pressure. Any less than that and it's power loss I can do without. Are roads in the US really that bad for riding on?
I am in canada. The proper winter and countless annual freeze/thaw cycles makes for crap roads. The good stuff never lasts long. Cracks, patches on patches, etc. I will go higher pressure for select routes and goals (hillclimb up a smooth road).

Yeah, for reference, with that combo and a 20lbs tt bike i would start you at 81/75psi!!!

If your roads are good, i think 110psi or a bit less would be near spot on for your weight.

Here is the silca post (or one of them... he has a series of 5 articles on tires). https://blog.silca.cc/part-4b-rolling-r ... -impedance

Here is the data that has influenced pressure choices back out of the stratosphere for most of our typical “crappy roads”. (Some) pros have known this stuff for some time, but it seems to be in the general public only in the last 3-4 years. A great way to sell high end bike pumps (i have one, and love it). The real inspiration was mastering cobbles at pro speeds, but it was a surprising finding in how much things like fresh pavement or chipseal benefitted from lower pressures.
256B9695-33A0-4510-8E89-E8278E71504D.png
I want to say that this data was for a 75, or maybe 90kg bike and rider combo (i forget) so at 61kg +6kg, i scaled down my pressures accordingly (i run about 70psi for true 25mm wide mounted tires as a baseline).

Another key here is that hitting “perfect” pressure is impossible. But there tends to be less penalty being low, vs too high.

Bikerollingresistance.com kind of brainwashes folks to think higher is faster. And sure it is, on a flat surface like a roller that a wheel is forced into constant contact with. It is kind of like the limits of cfd or laminar airflow to determine aerodynamic efficiency of bikes in the real world. It is not useless, but it has limits, and is not the full picture.

Tires that are too stiff really start to cause a lot of energy loss through vibration, and worst case, springing the bike/rider into the air. But higher pressure has less crr. It really is a “baby bear” scenario, vs maximize/minimize. The trick is that baby bear varies with every road surface, and multiple times a ride.

Heck, the pros choose tire pressures for the roubaix based on prevailing winds (i.e. they optimize tire pressure based on where they expect the winning move to take place in the race). This year they ran higher pressures because the wind did not favor the race being won on the cobbles.

But like aerodynamics, it is largely an exercise in faith. Aside from repeats of the chung method, it is pretty hard to prove. For most of us. Still, the silca data is the best data i have seen, so i am influenced by it. Tom A. also independantly came across the same conclusion. Mountain bike guys knew this for years, but again, i think some were surpsised how much the same theories carried over to “smooth” road.

by Weenie


talltales
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by talltales

So why doesnt any manufacturer make butyl tubes with optimized compound. Alle the good tyres are claimed to be Black chili this 11storm that, ect.

TobinHatesYou
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by TobinHatesYou

talltales wrote:
Wed Aug 21, 2019 7:36 am
So why doesnt any manufacturer make butyl tubes with optimized compound. Alle the good tyres are claimed to be Black chili this 11storm that, ect.

Because latex tubes and tubeless tires exist and "special" butyl tubes would still be slower. Aka this is not a niche that actually exists.

Marin
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by Marin

talltales wrote:
Wed Aug 21, 2019 7:36 am
So why doesnt any manufacturer make butyl tubes with optimized compound. Alle the good tyres are claimed to be Black chili this 11storm that, ect.
They actually do, Conti uses a more elastic butyl compound for their Supersonic inner tubes.

They are extremely stretchy - I ran them in 35mm CX tires - and they have tested very close to latex. I only run tubeless and latex, but I have Supersonics in my Jersey pocket.

RocketRacing
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by RocketRacing

talltales wrote:
Wed Aug 21, 2019 7:36 am
So why doesnt any manufacturer make butyl tubes with optimized compound. Alle the good tyres are claimed to be Black chili this 11storm that, ect.
As above. But also because i suspect it is a non-linear problem. You might get butyl faster, but that may come with new issues.

Also development costs. I suspect much of r&d is going into tubless right now. Tubolito deserves props innovating in an area that has been rather silent.

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pdlpsher1
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by pdlpsher1

Marin wrote: They actually do, Conti uses a more elastic butyl compound for their Supersonic inner tubes.

They are extremely stretchy - I ran them in 35mm CX tires - and they have tested very close to latex. I only run tubeless and latex, but I have Supersonics in my Jersey pocket.
Can you provide a source where you got that Conti uses a diff compound?

I have pumped up a standard butyl tube to the size of a cucumber outside of the tire to find a slow leak. Me think the Supersonics feel stretchy simply due to the fact that it’s half of the thickness of a standard tube. I have a Supersonic tube and the material looks identical to standard butyl.


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Marin
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by Marin

pdlpsher1 wrote:
Thu Aug 22, 2019 3:26 am


Can you provide a source where you got that Conti uses a diff compound?
It was a trade show interview with a Conti guy, don't remember where I read it.

bm0p700f
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by bm0p700f

Alexandrumarian wrote:
Sun Aug 18, 2019 8:28 pm
Well stuff can happen either way. These past couple months I was all hyped up about the crazy low rr of the 5000tl, started saving money for some fancy wheels etc. Then I go on a ride with a buddy on 5000tl and we go over at speed over a series of potholes. They were pretty nasty because I felt the shocks even in my ankles despite being on a super light / comfy everything carbon thing. 20 meters further my buddy pulls over with a dead rear wheel. Found a couple 2mm gashes, wouldn't seal no matter what. No scratch on my tubulars. Could have been the other way around and I admit that being thorn and glass shard proof takes care of 97% of all flat posibilities. Still, clinchers with latex are not that bad. I've dragged brakes on them in the mountains without problem and even found a fold pinched by the bead and used like that for over 1y. And overall I got less flats on latex than on butyl, but maybe that's just a statistical accident.
2mm cut can be plugged if they dont seal. that what I did with a IRC roadlite (very worn so no surprise it punctured) and it was fine for the remaining 300km.
GP5000TL tyres are not that fragile. they just wear out quickly. They cut an puncture for sure but that why plugs where invented. why some people cant get them to work is beyond me. I do every time. Maybe its the maxalami plugs I use.

Latex tubes are fine mostly but I had a number of unexplained punctures with them (vittoria tubes) and eventually gave up on them and went tubeless. the slowest tyre is one that flats. On Wednesday when I punctured in PBP I was tired was on my way in a couple of minutes. I did not even pump up the tyre as there was more than enough air still left (the sealant was trying to seal it but strugglinging). I was using a worn IRC roadlite front and the maxxis Padrone rear. Not sure I want a faster tyre for that kind of ride. The roadlite tyre went from fairly worn to fully worn over the ride. That a front tyre but there were lots of fast decent with tight corners for tyre wear. a new set of Conti GP5000TL could have been quite worn by the end. I am also not sure how much time they would have saved or conti GP5000 tyres would latex tubes over the tyres I used.
Last edited by bm0p700f on Fri Aug 23, 2019 10:26 pm, edited 1 time in total.

bm0p700f
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by bm0p700f

hambini wrote:
Mon Aug 19, 2019 9:49 pm
Am I the only one who regularly pumps the tyres up to the rated sidewall pressure? ie my Conti's get the full 8.5 bar, I can't imagine riding with 6 bar, it will feel like riding through treacle.
yes you are Ignore the max pressure ratings and the recomned pressures. I use what feels right. for you if 8.5 bar feels right then its right for you. I dont know what 8.5 bar is I am a psi luditte. I need a calcuator to work that one out. 14.7x8.5 is too much or my head. now wheres that wine.

RocketRacing
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by RocketRacing

Just under 120psi

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pdlpsher1
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by pdlpsher1

Since I already have the Vittoria 17-24mm tube I decided to give latex another try. The tube seems too small for my 28mm tires so I don’t plan to use it after some Silca’s I ordered get here. I think the newer Vittorias are more reliable because they are thicker and heavier. It also explains why they seem to hold air better as reported by others. My 17-24mm tube weighs 66g which is too thin for latex. I think with latex the less stretch the better, because they don’t stretch uniformly like butyl, despite that latex stretches easier than butyl. I don’t think a thicker latex will lose the rolling resistance advantage.


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JerryLook
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by JerryLook

I use the 19-24mm tubes in 27mm measured tires. I bet they would be fine in your 28mm too.
Some MTB’ers carry a road latex tube for use as a spare.
2010 Orbea Opal 54cm
5.97kg

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pdlpsher1
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by pdlpsher1

From my prior experience with latex a stretch of tube will stretch too thin and rip when stressed. So a thicker tube that’s sized correctly to the tire is key.


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pdlpsher1
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by pdlpsher1

Been testing latex with good results. I’ve set multiple downhill PRs. I’m using the Silca 24-30mm tubes with alloy stem. They weigh 85g so on the heavier side but the extra weight will help with longevity. I also plan to replace the tubes after any signs of stretching. My last foray with latex was a long time ago. Narrow rims with cotton rim strips. The tube would blow up after pumping up. Now I have Boras with no rim strips. I hope they will be more durable.


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