sleepystarz

I've thought the same thing as well... but again... it is probably a much bigger benefit to have the INCREASED PUNCTURE RESISTANCE and BETTER HANDLING of the tubular ~~ both of which are critical for a race. Is it worth it to trade off the supposedly better rolling resistance of a clincher for the benefits of the tubular? Must be. My reasoning if I had to choose would be that it's better to lose some seconds on rolling resistance vs. losing many minutes on a flat tire or crash. Also, for us mortals a crash just means we need to recover. For a pro it can mean the end of his career. Cycling as a hobby or amateur is very different from pros as far as importance of a crash.

I've heard a lot of talk about rotational weight and whether it matters or not. I'm not a scientist and couldn't really say either way, but maybe the pros have found this to be something beneficial where you are basically accelerating a tiny bit through each pedal stroke as you travel through the stronger part of your stroke. Again, I'm just expressing my opinion, please don't take me as trying to state fact It's just my thoughts. I can understand that this slight accelerating effect through each pedal stroke is probably more pronounced when climbing vs. on the flats. Anyway, rotational weight is probably the last reason a pro will choose the tubular compared to the other reasons stated.

chzman

most people go on and on about how the pros are paid to ride certain equipment. while this is mostly true, wheel type (and therefore tire type) is usually the eception where the pros will either request a certain tubular or they will pay out of their own pocket to ride, eh, lets say Lightweights...

so while i agree with terry a little, i'll believe the actions of top pros first... and ride tubs

Voodoo76

Racing mostly Crits, on rough courses, you will find the following;

1) Tubulars do not pinch flat, especially at lower pressures that give a more supple tire.
2) Tubulars feel like they spend much more time on the ground. I think this is a combination of Tire casing construction and rim construction. The typical box section Tubie rim is more forgiving radially than the sections required for a clincher. The flexibility that Tubulars offer in terms of rim section design is often overlooked in the comparison.

On the feel issue clinchers have come a long way in the last 15 years with increased thread count ect.This started with the Specialized Turbo, the first clincher that was even given a passing look by road racers. The first clincher I actually raced on was the orignal Michelin Pro and I did have durability issues vs say a Vittoria CX.

brianallan

Guys, this is a very interested thread, and I've enjoyed reading most of it (which is my disclaimer for repeating what might have been said).

I'd like everyone to consider the use of a weighted rear wheel in breaking the hour record in regards to the debate over weight as a significant factor.

I also came accross this photo in searching for the article, which I find to be beautiful.


ok so here's the velonews snippit. In the printed version the rider and coach talked about using a weighted rear disc wheel because of it's affects on momentum. The bike he broke the record on weighed 21lbs.

https://www.velonews.com/race/int/articles/8554.0.html

2Rodies

/\/\/\ I agree with the premise that a heavier wheel, once moving, may actually be easier to keep moving. That is why I stated that for constant tempo riding the difference between a lightweight wheel and a heavy wheel would be negligible. It's the penalty you pay for accelerating that heavier wheel over and over that makes the difference.

Grasschopper

Under those conditions I can see the use of the heavier wheel but that is not what we see in rear world road cycling. For the hour record we are talking about a perfect surface , nearly flat, no wind.

Going back to the original post, the cyclist in question has a zipp disc and 404 front wheel in the tubular form...his plan is to sell those, buy the clincher version of both and gain a significant time advantage on a 40 km TT. The difference in the 404 front is >200g just for the wheel then add the increase in weight of the tire tube combo you are talking about half a pound just in the front. Zipp isn't saying what the weight of their new clincher rear is so I can't compare there. I simply can't believe that the person in question is really going to be any faster.

Voodoo76

Sprinting on the Track this is very noticable. You would tend to see the "Top End" guys riding a Disc in back and the "Acceleration Guys" on a traditional wheel. Made the mistake one time of tactically shortening a sprint w disc on back and one extra tooth in front (my flying 200 setup), what a huge difference in acceleration (i got smoked). The line has been blured a bit as Disc's get lighter. But in that controlled environment on the Track weight has a huge impact.

I think on the road its more about durability and feel and less about any real performance advantage.

zzzwillzzz

actually you can but only for emergency purposes. many years ago i ran out of tubes and patches on my clinchers on a 100 mile ride and did the last 30 on a sew-up. it will work, but you will go really,really slow on anything resembling a corner.

why don't you guys run the numbers on analyticcycling.com? you'll see that wheel weight isn't as important as you make it out to be except in the extreme climbing cases.

clinchers have better rr than tubulars (i agree- don't call them tubies, thats right up there with brifters) but i don't think it's 1-2 minutes in a 40k a few seconds maybe.

so i have the most slippery bike with the lightest most aero wheels and tires with the lowest rr and then i get mt @ss kicked by days in a tt- now what? there's nothing left to buy-

Voodoo76

Excuses, rationalizations.

sleepystarz

BrianAllen ~ very interesting, thanks for posting. Goes right along with 2rodies logic posted below you. Of course on roads with hills, bumps, various turns, less than perfect conditions etc. the weight starts to play a different role and the energy expelled from numerous accelerations can start to benefit from less weight on the wheels. It starts to become a compromise between momentum/aerodynamics for the "constant tempo riding" as rodies put it VS. changing conditions requiring acceleration and change of speed. It becomes a fine balance and that's why we see guys using boras or even heavy as hell cosmics for TTs while using light wheels with less aerodynamics for climbs and slower speeds. Of course aerodynamics always plays a role which increases with importance as the speeds increase.

Momentum of a wheel can be beneficial on flat, consistant conditions, but the energy wasted on having to accelerate a heavy wheel in other conditions can really become important.


Now this is something I would love to see tested....but to see it done correctly would probably need a real TT course (no drum rollers) with a very consistent rider testing on multiple days with controlled conditions. Test the clincher one day, test the tubular another day with same amount of rest/preperation, same wheel. Of course, wind and other factors always come into play so to test something like this would be very difficult.

In regards to the OPs post, I honestly don't think it will make much of a change at all in the TT if he sticks to the same wheel profile and opts for better rolling resistance and some more weight of clincher. Now if he switches from something like 50mm to 10mm rim then his results would probably have a bigger change? In the end the tubular will prevail for important races because of the reasons already mentioned in this thread. If he takes those reasons into consideration, and not just the rolling resistance maybe he will give it a second thought.

fmw

I've never seen a track race. How fast do these guys go on the track? Sorry, I don't mean to hijack the thread.

mollusk

This poses an experimental difficulty then. We now have two different wheels with different rims, spokes, and hubs. One is for the clincher tests and one is for the tubular tests. How do we know that they have exactly the same friction in the bearings and aerodynamic drag so that the only measurable difference is the rolling resistance? Perhaps that has been accounted for somehow, but I don't wee it in the test protocols.

You are making assumptions about what "should" be. Your assumptions may be correct, but I don't know for sure. I can make a reasonable argument that on a non-smooth surface the weight of the wheel (including the tire) makes a difference. Imagine for arguments sake that your wheel is rigid so that any imperfections in the road are immediately transferred into a vertical displacement. This will cause a change in the potential energy equal to the mass of the wheel time the elevation change times the acceleration of gravity. As the wheel falls back down some of this potential energy is converted back into kinetic energy (forward motion), but much of it will be given back as vibration in the bike that is eventually damped out (a loss mechanism). Just guessing at some reasonable numbers for roughness of relatively smooth pavement we could have something like a 1 mm "bump" every 1 cm. Travelling at 30 km/hr we then would have a power loss of around 4 watts for a 0.5 kg wheel due to the vibration using these crude estimates. The frequency of these bumps would be about 800 Hz and that seems about the right order of magnitude for road vibration at such speeds. Rougher surfaces would give a higher power loss as the amplitude of the vertical wheel excusion is increased. (The total loss due to the road vibration should be higher still because the frame will also be moved slightly upward with every bump. The wheels, fork, and stays somewhat "suspend" the frame so I don't have a real good feel for how much vertical displacement is transmitted to the frame from the road, but it is clearly not zero especially on my 20-year-old Cannodale.)

Softening the ride (lower pressure) would make the tire "jump" less on the bumps and decrease this loss mechanism, but it would raise the rolling resistance. Using a nominal resistance of 300 "grams" corresponds to a power of around 22 Watts at 30 km/hr. Since these number look to be of similar magnitude there is probably an optimum tire pressure for a given tire on a given surface. I think that a lot of riders instinctively know this.

steve_wmn

Maybe, maybe not. It's entirely possible that the differences in RR found by measuring on a smooth drum would be lost in the noise on a rougher surface. I wish I could find the study that said that higher pressures don't always yield better RR on a real road. Looking at Jobst's data it's clear that the tubulars have flatlined at 130 psi, and probably wouldn't go any lower in RR at a higher psi even on a smooth surface. Clincher RR was still going down at 130 but appears to bottom out at 150 psi on the analyticcycling.com charts of rolling resistance.

sleepystarz

Interesting...for me the cutoff of increasing PSI in exchange for better rolling resistance is 120psi. Given my weight it seems I'll waste more energy fighting irregularities with pressures higher than 120psi to be worth any reduced rolling resistance. I guess you could also say that tire pressures too high can in itself create more "rolling resistance" from the tire not being able to conform to irregularities as well. As mentioned many times before, it's a fine balance between higher pressure while still being able to soak up some bumps.

2Rodies

This isn't necessarily a fair comparaison but I run my tubulars (not tubies don't want to offend anyone ) at 140psi. I run my clincher race wheels at 120psi. The tubulars are much smoother than the clinchers even with 20psi more air. This can't be a direct comparison due to the fact that my tubulars are Vittoria CX's mounted on Reynold Stratus DV's. The clinchers are Vittoria CX's mounted on Campagnolo Neutrons.

Now my training wheel are Mavic CXP's with Vittoria Rubino's. The rear hub is a PowerTap Pro hub the front is a Shimamo 105. My rear wheel/tire/tube combo weighs just 100g's less than both of my Stratus/tires combined. Yes this makes a big difference in acceleration and energy used.

juicemouse

I don't fully understand how a "jumping" tire (ie. one that's inflated so hard that it is not able to conform to road imperfections) adds resistance to motion. It doesn't sound like it's related to rolling resistance (which I understand). Is it some other mechanism?

I'd appreciate someone pointing me to some other source if this has been covered before.

DocRay

See a track race at all costs, you will become hooked. Track racing can see speeds of 60km/hr and very fast sprinting.

DocRay

that's not rolling resistence, that's bike control issues. You can't ride fast if you can't control your bike and have a smooth cadence.

Vinokurtov

No disrespect meant, but he who does not ride crits may not be the best source for crit wheel advice

Because most crits end in sprints, you might want to look at the wheelsets used by the top sprinters. If aerodynamics were all powerfull in a high speed sprint, then you would expect to see nothing but low spoke count, deep v wheels. In fact that's not the case at all, Hushvold among others runs relatively high spoke count, low profile wheels, as did Robbie McEwen when he took several of his green jerseys at the TDF.

https://www.cyclingnews.com/tech/2006...e_look_hushovd

And I'm skeptical, given the amount of "rebranding" that occurs in the pro peleton, and the stakes of say, a green jersey (or yellow jersey) at the TDF, that "they just ride what they are told", as some people like to assert. See: Jan Ulrich's Walser TT bike, which has been repainted more than most ocean liners.

Other stuff:

If you believe weight at the furthest point (rim and tire) from the axle is irrelevant, I'd ask you to do this test:

Put two full water bottles (lets say 5 pounds of goop) on your bike and ride your favorite climb. Now take a five pount weight and put it on your spoke nipples. Which do you notice more and which takes more effort to move up that hill?

Heck Terry, I'll take the five pound bottle, you take the five pound nipple, and I'll race you for bikes

The actual weight difference between a deep v clincher and a lightweight, low profile tubular could be as much as 2 pounds, if you weigh the tire and wheels. You're discounting the accelleration vector, and the watts expended for accelleration; this is a straight curve that goes up as you move a weight outward from the axle.

If you charted actual speed of your bike as you pedal, you'd find it's an oscillating graph. Those oscillations would broaden as you steepen the hill, you're constantly accellerating and deccellerating (unless you've got an absolutely perfect pedal stroke). All this equals an increase in watts expended to maintain linear motion.

If you look at a muscle fatigue graph, the higher the wattage, the quicker the muscle fatigues. So if you can minimize watts expended, especially as you extend the effort, you're better off. Less watts=longer sustained effort.

Also, aero drag vs. weight/rolling resistance is an opposite curve, aero becoming significant as speed increases in the amount of wattage expended.

Ultimitely, this whole debate is situational based on the type of course one is riding, and environmental factors such as wind, and whether you might be fast twitch or slow twitch.

Miller2

Not real familiar with the liingo here...can I assume a clincher is a tubeless tire? I didnt know they existed for bikes. I also assume it needs a special wheel?

2Rodies

A clincher is the 'standard' type of tire you would find on most road bikes. They require a tube. A tubular tire is a tire that has a tube sewn in, and are some times called sew ups. They require a special type of wheel and are attached to the wheel by glue.

Grasschopper

Nope you have it backwards. Clinchers are the tires that require tubes, they use a bead (wire or Kevlar) which holds the tire to the rim when the tube inside is expanded. Tubular tires have a round cross section and either have a tube built into them or in the case of Tufo tires don't have a tube. Tubulars are glued or taped (special tape) to the rim which is different from a clincher rimin that it doesn't have a bead for the tire to grab on to.

Clincher rim cross section:


Tubular rim cross section:

Miller2

That clears it up.

2Rodies

Well Lennard Zinn must have been spying on us and decided to chime in:

https://www.velonews.com/tech/report/...es/9662.0.html

Looks like rotational weight matters.

Grasschopper

See there is my point EXACTLY. Even in the crude calculation there was a 1 watt per 10g of rotational weight...just the front Zipp 404 is 212g heavier in the switch from tubular to clincher, the weight is ALL at the outter part of the rim and that doesn't even include the slight increase in tire weight when going from tubular to clincher. Zipp hasn't published the weight of the clincher disc yet but if you look at their other wheels the >200g per wheel number holds up so it is safe to assume that this guy would be not only adding nearly a full puond of weight to the bike but putting at the worst possible place, the largest rotating dia.