WhyFi

Got it - so you're moving goalposts wherein subjective, real world observation need to be quantified but stuff quantified in a lab setting don't count. ******g excelling work, man.

aclinjury

i'm replying to say i'm done with you! It's obvious to me you don't understand science rigor, even though you pretend to talk science. Comical. Out!

WhyFi

Don't tease us.

aclinjury

So no real world evidence from you, either? Got it man, it's ok, I don't expect most folks to understand real science. Hey let's stick to broscience, okay!

WhyFi

Let's look at the the OP for context...

Funny. I'm not seeing any requests for observation if and only if it's backed by robust data.

guadzilla

Thanks! I am sticking to 24mm Turbo Cottons on my CLX64s, but was thinking of putting GP5ks on the CL50s, which are my daily riding wheels. They are 30mm OD, so i am hoping the 28mms will fit them well enough.

That said, they arent my favorite tires either, and you now have my interest with this talk of the new Corsas. Are these the new tubeless versions that were announced recently? I gave my last pair of Corsas to my wife a couple of months ago - I have a pair of Wolfpack tires that are next in queue, but if the new tubeless Corsas have the same ride feel as the older ones, may jump on a pair as well.

genejockey 

The only real science that ANYONE has presented here has to do with rolling resistance. Everything else, including everything you've posted, is either subjective, or so loaded with uncontrolled variables as to be impossible to analyze. And yes, I do understand "real science" because it's what I've done for a living - and a pretty good one - for the last 4 decades.

base2 

I, for one, have found this thread particularly entertaining.
Thanks Bike Forums!

motivated_reasoning_olympics_2x by Richard Mozzarella, on Flickr

rubiksoval

There it is.

August West

I run GP5000 32c on 21.5mm wheels they ended up at about 32.75mm after they stretched out. So, much closer to stated width than the GP4000s II where a 28c on the same wheels ended up at almost 32mm.

ZHVelo

Do you mean scientific rigor?

JS41989

This is still going?

aclinjury

Veloflex new Corsa come regular clincher and tubeless clincher. I just got the regular clincher ones. But my buddy got the tubeless version. I haven't time to try out neither version yet so I can't really say much about how they ride. But but what I can say for fact is that based on weight and "feeling in my hands", the regular clincher is lighter (by ~30g) and more supple than their tubeless version, and this is to be expected. But if you think about it, their tubeless version being 30g lighter is actually very impressive, my only question is how will they wear for a tubeless tire (because generally, if I were to go tubeless, I wouldn't want it to be tooooo light due to fasting wearing AND possibly not sealing as well).

aclinjury

ok boys, i'm done arguing back and forth. I think i've stated my point clear by now.

This is for the OP (if he's still reading this thread!).

OP, by now you've heard "less rolling resistance = free speed". Well, no it's not free speed. What you're looking at is paying for more then DOUBLE the price for a set of tires, for 1 second of speed in a kilo based on a controlled test. Real world just riding around, hard to say if you'll get that 1 second or if at all.
But the price you pay is a real one, guaranteed to happen. Ultimately, less rolling resistance, in this case, is not free. There's a $$$ cost.

Free speed only is free if you pay for another set of tires at the same price and get to go faster. That's when it's truely free speed.

WhyFi

Are you sure that it wasn't a glute injury? 'Cause you don't seem to know your ass from your knee.

Bah Humbug

I thought you meant because he was butt-hurt.

guadzilla

For me, my thought process is the opposite - if i can run a lighter tire (like the Veloflex Corsa or most specifically, the Vittoria Corsa Speeds) tubeless and get better sealing in the event of small flats, that would be fantastic. I'd love to be able to use Corsa Speeds as my race tires.

The good thing is that the Veloflex tires are available at a pretty neat discount, so it's relatively low risk to pick up a pair and try out. Will order one as soon as i wear through the current tires on my Venge.

aclinjury

couple of pics,
New veloflex on the right, old one on the right. Both 25mm.
New one, 212g. Old 207g. These are regular clincher. The new tubeless clincher is 21g heavier than the new clincher (not 30g like I said earlier).
The inner side look and feel very much the same,
Here are some obsrvations. The new one is a tad thicker in the middle, where the meat of tire is (probably good for wear). The bead of the new one is slighter tougher (Veloflex said for compatiblity of all carbon rims, no exception like Enve). The tubeless version just feels a tad thicker and heavier.
Veloflex claims that the new clincher has a lower rolling reistance, right. If you just compare the tread pattern alone, you (well, I) notice that the new thread pattern is not as aggressive as the old one (you can feel this by running your fingers up and down the thread), makes me wonder if rolling resistance is mainly due to changing tread pattern, but hopefully this won't compromise the new one's handling? we'll see

guadzilla

Damn, now i am seriously jonesing for a pair to run tubeless.... thanks for the detailed photos!

guadzilla

On a different note, since we are talking CRR, here is an interesting article:
https://blog.silca.cc/part-4b-rollin...-and-impedance

It shows the difference between the theory of drum tests vs actual riding on the road (where what they call "impedance" also starts to play a role). There are a couple of interesting take-aways that I see here:
1) It is better to err on the side of tire pressure being a bit too low vs a bit too high
2) Tires with more supple casings tend to have lower CRR and also more forgiving of over/under pressure

Does that level the playing field in the rear world, for tires like Turbo Cottons, which test 2-3W slower than GP5ks in the drum test but have a much more supple casing?

RChung

You can do both, you know. That's allowed.

RChung

Almost always, the rank ordering of tires on rollers is the same as on the road. Sometimes two tires will swap ranking, but usually that's when the tires are pretty close to begin with. An exception can occur when the impedance break point on one tire comes a little earlier than the other. If you're in the neighborhood of that threshold, you can also observe a ranking swap.

Almost always, if you see a discussion of impedance breakpoint they're talking about real world field testing on roads as opposed to on a roller.

guadzilla

Thanks for that - yeah, that does makes logical sense. Is there a very *approximate* ballpark range in terms of closeness where the rankings can change, in your experience? I wouldnt expect a tire to make up a 7-8W gap, but are we talking fractions of a watt,1-2 watts or some other number? To be clear - i realize this is not going to be a scientific calculation, just a guesstimate borne of experience.

upthywazzoo 

Wouldn't this be dependent on the road surface and sprung weight? As shown in the article linked, rolling resistance/friction increases with surface roughness. If friction is a function of the area of the contact patch, as well as the per-watt flex of the sidewalls, then on a perfectly flat surface, the best tire would be completely stiff. As surface roughness increases, the tire would be spending less and less time in contact with the ground, due to bouncing, leading to a pedaling inefficiency.

For a straight line path then, the ideal (efficiency-wise) tire would then be a combination of the minimum surface area for "good" traction with the minimum amount of deformation necessary to maintain that surface area.

It's conceivable then to me, that the Turbo Cotton tires would outperform the GP5k in certain surface roughness conditions.

RChung

That depends on how careful you're being in testing. If you're being really careful, you can reliably discern a difference in Crr *on the road* of maybe around 5% or maybe a bit less (I prefer to work in Crr rather that watts since watts depends on your speed and total weight). So if you're measuring a tire that has a Crr on the road of around .004, that means you can reliably discern a difference of around .0002, or a bit less.

So, one thing we noticed in addition to the rankings not changing much between roller and road testing: Real roads tend to be a little less perfect than even the kind of diamond plate Jarno uses for his big drum, plus when you pedal you're moving around and leaning the tire this way and that. So Crr measured in field tests tends to be maybe 1.5x higher in absolute terms than what Jarno measures on his drum. That is, the relative rankings and the relative differentials tend to be very close between rollers and road, but the absolute raw Crr values vary by maybe 1.5 (and this will depend on the condition of the pavement).

Here's the practical bottom line: if I absolutely positively need to know--like when I'm working with someone making a record attempt--I'll test CdA and Crr on the surface being raced on. However, for most purposes, I just use the roller tests, multiply by maybe 1.5, and use that. That usually gets me close (but, of course, I check).