tomato coupe

Sorry, I thought you said you measured it?

GhostRider62

Sorry if you do not understand.

I was asked how much of my 50 second time improvement was due to the tire size.

The conditions during that day were much worse than my prior PB. I have a 50 second time differential and an increase in power output on a day with worse wind, worse humidity (dry day), lower temperatures, a slight headwind from which to tease out how much of the 50 seconds was due to tire width, how much was properly tucking my camelback hose, and how much of it was the additional power.

If you can give me a tutorial on that? I do not think it is possible. At least, I would have had no way to calculate that time differential even if I was interested in doing so back then.

If a rider has a CdA of 0.250 riding at 25 mph and another has a CdA of 0.150 riding at 30 mph and both lower their CdA by 0.01, the time savings will be dramatically different for each over any distance and not really meaningful in such a forum.

Edit: I suspect the M5 Two Spoke Sail effect on some portions of the course had a massive effect. I PM'd Hambini, I am sure he can divine it for me. I cannot. It is also important to realize estimation of CdA on a pipeline is not the same as being able to say how much of a time improvement one will get on an open road because there are so many variable on the open road compared to a wind tunnel or a windless, carless testing street. The road surface alone is different from those two locations. So, even though a 23 mm tire is measurably better than a 25 mm tire, I cannot see how one can take a time on a course and compare it to a previous time and then say how much of that time improvement is due to one thing like a tire that fits flush to the rim. I have no idea how to do that.

PeteHski

The rougher the road, the less I read into drum tests. For smooth tarmac I would tend to trust the relative differences in rolling resistance from drum tests, but the roads I often ride on are bordering on gravel bike territory. So I can't just slap on a pair of Corsa Speeds and expect to go significantly faster. But if I was racing on pristine tarmac I'm sure they would be fantastic. For me it's far more of a compromise between rolling resistance, puncture protection, grip and ride quality. I know my tyres are not ultimately the fastest rolling, but I don't get flats or crash on slippery descents. I rode a Sportive event last weekend and one of the guys I was riding with spun his back wheel out on a steep slippery climb, snapped a spoke and chewed up his rear mech. I didn't notice what tyres he was on, but they had zero grip at that point. Mine didn't slip at all.

However if I take the drum tests at face value, I could potentially gain about 12 mins over a 5 hour Sportive by switching to GP5000 TLs, which I'm intrigued to try. They would basically double my chances of getting a flat, but otherwise should be all good. I'm just a bit sceptical that they would actually be that much faster. I'm tempted to try a pair out on my local training loops and see.

GhostRider62

How fast can you change a flat?

I rode GP5000 tires over 10,000 miles in 2019 with three flats, which is about my norm. Unfortunately, one was on the 1218 Km Paris Brest Paris but the time it took to change the tube was much, much less than the time I saved over average tires had I run them. I did get one flat that year in cold, wet rain at 4-5 am and I doubt any tire would have survived the chunk of metal that punctured it. No flats this year!! I bet I get two flats tomorrow. Now, this is with tubes. Tubeless is not so fast to fix

A few years ago on my upright bike, I was chasing this stupid KoM on Strava. It was only a like a 3 mile segment. No matter what I could not get it even taking off the GP4000 tires and mounting super expensive Vittoria Speed Tubeless. The Speeds did not get me the KoM. I put a completely different set of tires on and got the KoM. Intrigued, I put the Speed back on a few times and could not get to the KoM time. I put those other tires on and was very close once and 1 second better another time. It took me two years to figure out why. I am sure some people here would have known immediately but I have limited tools at my side.

spilot101

That's exactly what got my thinking ball rolling....

PeteHski

It varies depending on how wet/cold/miserable it is and how much of a ***** the tyres are to get on/off. But I've been running tubeless for so long now (15+ years on mtb, but only 18 months on road, but didn't ride road for about 10 years previous to that) I would be a bit rusty. However I have had very good results plugging mtb tubeless tyres from the outside (which is quicker than changing a tube), but never actually had to do that on a road tyre yet - no flats over 18 months. For sure if GP5000 TLs really are that much faster I could afford one puncture and still possibly be ahead on time. Worth a test for sure, but our roads cause a lot of flats on tyres that are in any way susceptible. GP5000s get very mixed local reviews because of flats, as do Schwalbe Ones. I pass a lot of guys fixing flats on local events, which is also quite telling. It's nice having fairly bombproof tyres that are very unlikely to cause any problems.

GhostRider62

I rode Schwalbe Pro Ones tubeless, they were awful. Slow, wore terribly, and lots of flats where the casing was damaged.

It sounds like you are in the land of small flints on the road. Might be best to stay with what works. It is like goatheads in western usa. They make small holes but the sealant is effective and tubeless is the way to go there. But maybe not on your roads. No idea.

GhostRider62

I used to do rolldown testing of tires on a shallow hill that then has a long flat runout. I would start at the exact same spot on a windless day and then just glide (max speed is only 10 mph) until I stopped. I have never had a tire roll further on that venue than the Vittoria Speed tires.

RChung

So, I've done this but it's kind of a pain in the butt to do. Basically, you substitute one drag parameter then you go back to the original data and using the new parameter but the original power and mass and air density and road gradient, to calculate a new speed. Then you convert that to a new distance at that new speed. Then you go on to the next second and calculate a new speed given that you've moved a new distance (so the road gradient may be different). Lather, rinse, repeat until you've covered the total distance. The difference in time is that due to the updated drag parameter. I don't really recommend that anyone do this. I only did this to convince myself I could.

But the easier way is to ballpark it, and just use the rule of thumb that a difference in CdA of .01 m^2 is roughly equivalent to a difference in Crr of .001 which is roughly equivalent to 1 sec/km at TT speeds. There are obviously approximations involved but that generally gets you close to the tedious exact calculation.

RChung

Yeah, some of his ideas are intriguing--what's hard is figuring out the magnitude of the effects he's proposed.

Here's Josh Poertner's take on Hambini's wind tunnel protocol (Damon Rinard's take in that same thread was much shorter; my comments were sort of in-between): https://forum.slowtwitch.com/forum/?...79847#p6779847

PeteHski

Yeah, I've seen far too many bad reviews of the Pro Ones to consider trying them. I just wonder sometimes if I've swung a bit too far toward puncture protection over speed. It's a no-brainer for training rides when I really don't care about speeds, but for race events I might try something a bit "quicker". I think the Pirelli P Zero Race TLR could be a good option as they seem quite well balanced between speed, grip and protection. I don't think these existed in tubeless form when I was last looking for tyres.

GhostRider62

I had read all those threads on ST and other forum. Some parts of his explanations do not add up for sure although some do, or at least to me. I do not doubt that he could have access to the wind tunnel but the testing cycle time of 26 minutes makes a question. 20 wheels is what 9 hours of testing. Can a rider do that over some weekends? Why not. It would also seem the testing methodology would make the results less sensitive to small movement of the rider.

I came to the belief that fast smooth riders in most race conditions ride sufficient fast that the yaw angle is lower than the separation angle. However, there are conditions and speeds for which his turbulent transient air thesis would apply.

I went back to 8 months of data in GC and it shows I spent something like 150 hours at speeds 28-60 mph on my recumbent on public roads with traffic. I was a little surprised. I was usually TT on flats at 32-35 mph. Much of my searching was to try to tame small, swirling winds, it is remarkable what you notice and then learn to predict. I would get blown all over the place. If a large vehicle passing my 200 pound carcass moves me a foot, what effect does this have on Crr and CdA. I never felt these effects at 20-25 mph on an upright. At least Hambini was offering something that partially explained what I was dealing with. When Elite and Pro racers are doing those kind of speeds in a TT, the roads are closed and I would guess the A2 results to predict very well.

I also went back a few years to a note, I had then estimated the 25 mm tire cost me 15 watts at 30+ mph (not 20 watts). IIRC, I had the total reduction in CdA for both the drinking hose and the tire. I calculated what the misplaced hose would cost in CdA and subtracted it from the total to estimate the tire. I did write all this in a notebook but for me only, not a scientific endeavor.

The testing that I want to repeat is comparing my Flo60 carbon to the M5 Two Spoke wheel on my 10 mile TT course in a crosswind. As I mentioned I did ABBA tests. 10 miles up and 10 miles back with one wheel. Swap to the other and repeat twice. Then, swap back to the original wheel. I did the test trying to hold a modest speed of 21 mph. Analyse results. The results that I saw did suggest that the Flo detaches and perhaps the M5 Two Spoke does have a large sail effect (more than a rear disc wheel). I was really scratching my head back then. How could two different wheels test so close on my half pipe be so different on real roads with pretty strong winds at pretty modest speeds. At some angles, it felt I was barely pedaling with the M5 wheel vs the FLO60. The watt meter could have been wrong, too. I was never satisfied with my understanding of my observation; however, Hambini was the only one who offered a glimmer of understanding despite all the flaws of his communication.

GhostRider62

Back in the old days, everyone had their tubular race wheels. Now wheels are so durable and bulletproof that is is common just to ride the same high performance wheels all the time. I used to do Criteriums on Sunday about 40 miles from my house. If I drove there in a car, I would use my tubular race wheels. If I road to the race, I would use my training wheel with 28 or 32 mm Avocet tires that had no puncture protection. I usually did well with the clinchers. Not so often with the tubulars. I guess the 40 mile warm up was the reason, not the tires.

I have many sets of wheels. When I used to do rolldown tests, I would always test against my control wheelset (Vittoria Speeds). There was a lot of difference on a day to day basis in an absolute sense, but the relative difference to the control wheelset was always useful data. Ever put a new tire on and it feels slow? I got two bad tires over the years. I used to go thru tires in 4-8 weeks riding a lot, so, I would check new tires after mounting them. Mostly it was operator error, but twice it was messed up casing.

You could always buy a used set of wheels just for training and put the fast tires on your Sportive wheels?

WhyFi

If the P Zero Race TLR didn't exist the last time that you were looking at tubeless tires, then the current gen Pro One (Evo Addix) probably didn't, either. The original Pro One, which is undoubtedly what you've read reviews on, had a reputation for being pretty delicate and not very long-wearing. The Pro One Evo Addix is a very good tire (FWIW, I have some of those Pirelli sitting on a shelf, waiting to be ridden, but my Michelin Power Road TLRs just don't look like they're going to wear down and make way for the Pirelli any time soon; the Michelin should be on your list, too, if they're not already).

PeteHski

Yes, those were both on my shortlist. Going off the bcr tests, the Pirelli looks to have slightly better puncture resistance, but fractionally slower. As my race events are 100+ miles on rough roads I always tend to favour puncture protection. But having now raced my Cinturatos on 2 Sportive events I'm starting to think they are a bit slow, but great as a reliable training tyre.

PeteHski

As I only tend to do on average 1 event per month over the summer, it's not a big deal to swap tyres. But I'm probably going to buy another bike for next season and then I will have a training bike / 2 wheel sets. The wheels I have at the moment are the stock carbon Giant SLR1s that came on my Defy Pro. They are a bit narrow by current standards (17 mm internal), but otherwise really good for daily use. To throw a spanner in the works, the bike I'm thinking of buying (Specialized Roubaix Pro) currently comes with rims that are not tubeless compatible, so I might have to give that some thought as I really don't want to go back to tubed tyres. I might end up with a custom build instead.

WhyFi

The durability/puncture resistance of the Power Roads doesn't concern me at all. I've taken one cut (~4-5mm) to the Michelin that needed to be plugged with a bacon strip, but they've been reliable otherwise in the ~1500 miles of often rough and debris strewn roads that I've ridden them on. Based on the rear tire wear indicator, it's not yet halfway through its life span.

PeteHski

I'm sure there's not a huge amount between them in reality, but still the Pirelli scored significantly higher on puncture protection (57 vs 41) for a couple of Watts loss in power. I just hate flats!

WhyFi

Oh, I do too, which is why I'm on tubeless in the first place. It's just that I haven't seen much of a real-world difference in flats with most of the performance-oriented tires that I've tried. I've never had to address more than one flat per tire lifetime (typically between 2000-3000 miles each, for a rear tire, never had a front tire puncture that didn't seal), but most have had no flats at all.

Racing Dan

Possibly they wouldn't be any faster at all, depending if you are riding alone or in a bunch that you cant control the speed. However a flat instantly gets you dropped.

PeteHski

Exactly! In my last event I rode in a really strong group for three quarters of the race. A flat would have cost me a lot of time in that situation. Far more time than if I had a flat while riding solo.

PeteHski

That is pretty encouraging. But I'm still aiming for zero flats! I'm currently at about 10,000 km so far, on my second set of tubeless road tyres. I'm about ready to step up the performance level a little and see how it goes!