Tire chat (nerds only)

Regarding contis: Durability on the rear was not great, I had some kryptotals enduro spec, after 2 months the thread on them was surprisingly good, but the sidewalls were covered in weird cuts and the side knobs were splitting from the woven material underneath. My guess is whatever they used to bond the rubber to the layer underneath wasn't sticky enough or was getting damaged from small impacts.

Front tyre still working great after 4-5 months.

Thats basically what we do - constantly working on mathematical models, lab testing, on-trail data collection and finally in the hands of other riders. And there needs to be correlation between all those steps before it can be widely used or sold. I almost entirely use feedback from multiple riders of all sorts to make the ultimate decisions on how things are set up. I test things myself obviously but blind, unbiased feedback is far more useful in the long term! And like @jonkranked said they just need to be able to say if was better, worse or the same because if there is a genuine improvement they will definitely notice it. 

There always seems to be an assumption that lab testing is a substitute for real world use - it isn't, but we constantly refine the tests or interpretations so that they can give us information that matches what people report on the trail. Most of the time its driven by complaints people raise about a product or situation, so I'll try and figure out how I can measure or replicate that and begin to find a solution. It always goes back and forth between those things, and not a one way "this is what works in the lab so it must be right!!" kind of attitude, although I know some people like to act that way

Yeah, I think the components you listed are noticeable, but things like crank stiffness, wheel stiffness, handlebar compliance, and possibly even telling the difference between a carbon or aluminum frame just don't provide enough feedback for riders to reliably tell the difference. 

But, I like this thread because tires are a very noticeable bike component. I definitely feel like I can notice the difference in just 3 PSIs in my front tire. 

Freeze testing started!  (I didn't freeze a new Conti, just getting other numbers for comparisons. 

Here are my non-scientific results!

Frozen Tire Durometer Test

Details: Used IRC Tanken treated with hot laps tire treatment(Applied months ago)

Used durometer hardness tester Type “A”

Temperatures taken with infrared digital thermometer

Tire Temp: 58f in garage

Durometer rating: 56-61

Put tire in sun for 1 hour;

Tire Temp: 110f in sun

Durometer rating: 55-58

Put tire in freezer for 5hours;

Tire Temp: 13f

Durometer rating: 65

Tire after frozen but at room temp;

Tire Temp: 68f (room temp indoors)

Durometer rating: 58-60

In Garage after frozen

Tire Temp: 59f

Durometer rating: 58-60

Other ratings for comparison (Temp 58f-60f)

Used Tacki Chan: 45-50(with hot laps treatment)

Used Conti: 45-50 (with hot laps treatment)

New Conti: 55 (stiff rubber but has a sticky fresh feeling, all other used tires feel “dry”)

Used Motocross Dunlop MX34: 65-70

Used cushcore: 33-35 (tested 2 different ones)

CONCLUSION:

It is plausible that a frozen tire changes it's density.  The tire does return close to it's original hardness after frozen, but the tire is overall more consistency hard. I tested different knobs before frozen and the difference was bigger.  After freezing they were consistently all 58-60 top and side knobs.  What does this mean?  Don't ride when your tires are frozen, but if it's above 50f, they will pretty much be the same.

So I wonder if there’s a certain brands rubber that is less affected in cold temps than others? Was your used Tacky Chan a soft or super soft compound? I just bought a set of Tacky’s in SuperTrail casing with super soft front and soft rear to try out. I normally will dry seat them and leave them inflated to around 40-45psi overnight just to allow them to stretch. Not sure if that helps but it’s what I do. The next morning I came out to my shop and the back tire had blown off the rim overnight. Very disappointed because it definitely doesn’t stay seated now. I feel like that definitely should be happening with tires that cost $100 apiece

yes, definitely possible that different rubbers could be changed by freezing differently. But I think once they are in the sun they will go back to soft. I’ll try today.

SuperSoft DH tacky Chan.  I agree that the tire shouldn’t blow off the rim sitting there, but I also don’t think you need to leave them at 45psi.

You specify a rim width preference, but that's not terribly useful without knowing the tire width and rider weight as well. 

I feel that an important part of tire/rim/pressure discussion is rider weight.  The entire system has to work together.  I've always preferred wider tires and I won't even buy a bike that won't take a 2.6" tire and that also affects what rim width I prefer.  I think a 35 internal is absolutely great for maxxis 2.6 tires.  It's a combo that works really well.  I recently got an argtotal/kryptotal set, and while I haven't mounted them up yet, they look like they might be really square on my rims.  In the late 90s when 20-25mm rims were all you could commonly get I decided to try some Hutchinson Pythons instead of my usual Continentals.  The Pythons were a relatively high volume tire and they did not work on narrow rims at all(unless you ran a super-high pressure) while a continental of the same listed width worked pretty well.  By the early-mid 2000s, I was having trouble with the continentals folding over too much and moved away from them until I just happened to try a wider rim, and then they worked for me again. 

Rider weight has a lot to do with what pressure you can run, which has a lot to do with what rim width works for you. 

Here's a good question for the tire nerds:

I am not a good test rider. I can't easily tell the difference between 25 and 29 psi, for instance. But even I noticed last month, when I rode a shuttle ride at a high elevation, that my tires were hard. It was cold and the elevation was as much as 7,500 feet higher than where I was when I set my psi. I did not measure at the top; just rode it in hard mode and it got better as I descended. 

How much does external atmospheric pressure affect the psi measurement in a typical MTB tire? It would make sense to me that there is some difference, but it shouldn't be a ton, right? 
The tire is flexible, so it would change shape and size. A lot of internal psi would make the tire slightly larger and vice-versa with lower pressure. A lot of atmospheric pressure would tend to decrease the tire size, but that would increase the internal psi. It melts my brain just thinking about it. 

What you measure is the relative pressure, i.e. the pressure that is above the atmospheric pressure. The absolute pressure is the relative value + atmospheric pressure.

I'm more of a metric kinda guy, but if you set your tyres to 1,5 bar, the absolute pressure will be ~2,5 bar. The normal atmospheric pressure is 1013 mbar at sea level. At 2000 meters altitude it's ~0,8 bar. Thus going from sea level to 2000 m high will give you a change of 0,2 bar. This is easily 10 % more.

All of this is at a set temperature, raising the temperature will raise the pressure even more (and vice versa).

QED, I set my pressure to 1,4 bar at ~1100 m altitude in the (cold) morning and measured 1,6 bar at ~1900 in the warm afternoon.

TL;DR: yes, altitude matters. A lot. So does temperature. But the shape/size won't change that much as the tyre is fairly stiff. The biggest effect will be on the squished shape in the contact patch.

So, I believe the tire in question, which has a tread compound that never recovers from freezing temperature, is either the ADVAN A048 or ADVAN A055. These are both Yokohama tires, and nothing in the marketing blurb mentions this, probably because it's a clear product detriment, and marketers try to stick to benefits.

Yokohama does not make mountain bike tires, as everybody here is well aware of. But back when I was in the industry, about eight years ago, the talk about town was that the industry was at parity, meaning that there was no technology one company had that the others did not, so I would imagine that principles that held for Yokohama, most likely apply to mountain bike tire manufacturers.

Interesting, but we would need know the rubber they used and find out what mtb tires that is used in.

Absolutely, I skimmed the copy, but it didn't give up much information. Sometimes, it'll list a specific additive, like orange/citrus/almond oil, but the recipe itself is a very tightly held trade secret.

Unless I'm misunderstanding you, I feel like the math to find the correct pressure shouldn't be additive. What we should be looking for is the delta of internal pressure minus barometric pressure. This makes sense to me because what we want to know is the total pressure pushing outward on a tire so it keeps its shape, and barometric pressure cancels out this force, so in my head, it should be subtracted. 

I should be sleeping right now, but I keep thinking about how automobile/motorcycle racing tires (1) utilize tire warmers before a race and (2) their tires heat up over the course of a race.

I tried to google bicycle tire warmers, and it doesn't appear to be a product that exists. Also, I wonder if bike tires can transfer enough energy to warm them up. We're expecting a ton of rain for the next week where I live, but the next time I go riding, I want to bring my infrared temp gauge and see if my tires warm up relative to the environment over the course of a ride.

Back in my good ol' days of tire marketing, I remember that low pressure would result in carcass overheating and early failure, and this was also true for taller tread features, and these are both things synonymous with mountain bike tires, so maybe the meager energy input of a human can warm up a tire to an ideal temperature, or at least a less non-ideal temperature.

I sincerely doubt any measurable heating occurs in mtb or bicycle tyres in general. At least compared to what is seen in motorsports, cars and the like. An underinflated tyre warms up due to deformations going through the tyre by rotating it over the ground.

As for correct math, I never mentioned any math to determine the correct pressure. Only that the pressure measured in the tyre is relative to the atmospheric pressure. Which depends on the altitude (a bit on weather and temperature, but altitude much more). And the internal, absolute pressure is dependant on temperature of the tyre and the air in it. 

So the relative, effective pressure in the tyre will change depending on temperature and altitude. The absolute pressure in the tyre will not change with altitude, but will change with temperature.

The only case of math to determine the pressure would be to measure it at the start of a race at 3000m high or more with the finish at below 1000 m because it will drop by 0,2 bar over the course of the race (not including the rise in pressure because of warmer ambient temperatures). But if you set it in the valley and ride it as is, it's all good. The pressure will be higher at the top and you just deal with it. 

Apologies, I must've misread your comment. 

Yeah, it'd probably be a long shot whether the total, repeated deformations will raise the tire pressure, but unexpected results do happen.

Your right, it shouldn't.
Schwalbe warranty will definitely cover you on this one: https://www.schwalbetires.com/warranty/

Well, the other website had a "nerding out" article that definitely felt at least inspired by our conversation here. I understand this isn't exactly a novel topic, but it's still flattering nonetheless. One of the common refrains I saw in the comments multiple times is that "Maxxis rubber hardens a lot in the cold. As does Michelin. While Conti, Schwalbe and Specialized rubber doesn’t change as much." I think this could be a valuable topic to explore. 

Another comment that stuck out to me is that multiple people think that the relationship between hardness and temperature is non-linear, with tires performing reasonably well—and then when they drop below 45°F, they turn into rocks.

I’ve noticed that too- riding is fun and normal down to 45.  

45-30 is tolerable and tires/ suspension work noticeably worse. 
 

below 30f mostly sucks and you’re only out riding for fitness or extreme boredom.  Bike feels pretty bad at this point.

What tire/tread compound have you noticed this on?

Michelin racing line was the worst in cold 

maxxis maxxgrip get worse but not as much as the Michelins. 
 

The weird thing about that article was it blew straight past how much things warm up in use - even when it’s 0° C outside a shock will heat up rapidly and quite easily reach “normal” temperatures for your oil and air spring. Then on hot days the cooling effect of air flow stops them getting crazy hot in most situations so the actual difference in use is pretty small(about 30-40c). Tyres do warm up from use too - not to the same extent though, and it’s only the outer surface so not sure if it’s enough to bring grip back. I think the contact with the cold ground sucks a lot of the heat back out too  

When it’s real cold the fork does not warm up at all. Mag casting wicks a lot of heat quickly.

add that to probably cold hands and a cold front tire and the front of the bike feels terrible 

Just not riding fast enough then haha.
 

Even in cold conditions fork and shocks warm up quite a bit, and in normal conditions on a 4minute run shocks can seriously overheat, off the top of my head, some of the shocks at Val de Sole hit 160c at the finish line.

I think forks wouldn't warm up nearly as much as they are much larger volume, I doubt the front tyre can warmup in cold conditions as there isn't enough energy going into it, compared to the colder air passing directly through over it.

Anecdotally i find it easier to ride fast around freezing, as the ground (generally wet at those temperatures) starts to freeze and harden again providing more grip, whereas around 3-10c its most likely just wet and slippy.

Yeah forks won’t heat up as much, especially the air spring. The damper will warm a fair bit though and is super insulated by the air gap around it.

Im highly skeptical of some of the numbers I’ve heard people throw around that shocks can get to - I haven’t been able to log a WC dh run but I would expect more like 60 degrees C is realistic. If they’re getting beyond 70 or 80 the shocks would completely cook as the rubber seals  inside aren’t intended to run above that. Plus you would be getting literal burns on people if their shock could reach 160!

realistic temps are 30-40c, a pretty hot run might be 50 for most people, and 60 is an extreme case 

I think it makes sense that the pinkbike article skated around the issue of generated heat because 1) the article is filler for the slow news northern hemisphere off season — here’s the same article from Bike Rumor from 2018! https://bikerumor.com/suspension-tech-how-do-temperature-changes-affect-suspension-performance/

2) because the entire mis-use of the gas law in this context gets too complicated to support the article’s contention when Twarm and Tcold aren’t set unchanging at whatever arbitrary ambient air temps the author has chosen to illustrate the change in P. Suddenly you don’t ‘know’ delta T and good luck with that equation you built the article around.

The bike rumor article’s author chose the exact same emphasis on the more trivial part, calculation of air spring pressure (though interestingly the fox guy’s and the cane creek guys statements don’t totally agree), and says precious little definitively about the effect of temp on damping, because _____.

How can anyone know the motivations of another person? I’d guess because damping is complicated and resists being boiled down into the kind of simple rules of thumb cycling media love to trade. I suspect a degree of condescension in all journalists who feel their audience requires dumbing the content down and also won’t know when the journalist gets it wrong. And don’t count out the simplest possibility, that dude simply doesn’t know what he’s talking about.

Should’ve focused more on tires.

FWIW, I rode in the cold a week ago (some snow dusting at the top) and the Michelin Racing Lines fared very much OK. I was scared of what was going to happen considering the comments in this thread, but they gripped very much OK for my standards (these are the tyres that have built up my confidence in slippery conditions with actually having some grip after all). Maxxis MaxxGrip 3Cs have fallen appart in the cold in the past with knobs being torn off all around the tyre (an old tyre, but this did happen over the course of a single or two rides in the cold).