View Single Post
Old 06-24-20, 09:45 PM
  #14  
taras0000
Lapped 3x
 
taras0000's Avatar
 
Join Date: Dec 2004
Location: 43.2330941,-79.8022037,17
Posts: 1,723
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 325 Post(s)
Liked 22 Times in 19 Posts
Originally Posted by carleton View Post
Yeah, that Gippieme wheel is nice. Similar to the old Campy Shamal and Atlanta 96 wheels.
The Shamal was just a rebranded Gippieme 416. Gippieme was Campagnolo's aluminum rim supplier for ages.

Originally Posted by carleton View Post
The wide trend has definitely come to the track and I'm not convinced that it's faster. I think it's more marketing and "keeping up with the Jones'" because they have to. Customers are convinced that it's faster and won't buy non-wide wheels or tires.
I totally agree with this. For outdoor tracks, there may be some data to support going wider, especially if you need a wider tire because of the track surface. On an outdoor track, depending on how sheltered it is, you may be dealing with crosswinds, and therefore greater yaw angles where wider combos have some benefit in keeping a more laminar flow around the rim.

Originally Posted by carleton View Post
Here is the Shamal:



Darren Hill vs Jen Fiedler:

I can't find a pic of the Campy Pista wheels from the era. Those were the ones that the top riders in the world used at the time , either as a match set or bladed 16 spoke front and disc rear. It's still a very fast wheel. Aerodynamics haven't changed.
Again, this wheel was supplied by Gippieme. I knew a guy who had a set and they were almost identical to the old Shamal wheel save for newer hubs and spokes. In case anyone was interested, they also supplied wheels for Miche.

Originally Posted by chas58 View Post
I've been curious on this as well. The only difference I've noticed is wider wheels making a better aerodynamic match to the tire (well, wider than 17c or 15c).

The rolling resistance benefit of wider tires is that a skinny tire has a long narrow contact patch, which increases sidewall deflection. I'm usually on a 166mm track, so my weight is probably effectively doubled at speed. I do notice a noticeable sidewall deflection on some tires on the track (typically not for the skinny guys). I can't see my rear tire on the track (like I can on the road), but I'm thinking rolling resistance has a lot to do with minimizing tire drop. If you are over 200lbs, you are going to need a lot of air in that tire in a 2g turn.
I've never seen a tire less than 18mm in the flesh, or even heard of them outside of older World Cup equipment available to top riders on a made to order basis.

The reason for running really high pressures on skinny tires is to minimize ANY tire deformation. To minimize rolling resistance at the tire, you need to eliminate as much tire deformation as possible (not just sidewall, but contact patch as well), and minimize your contact patch. This only works to a certain point, because there still needs to be a certain amount of suppleness and grip. This is why many competition tubulars are rated to >200psi and had super thin silk casings with a high thread count and soft rubber compounds. On a smooth surface, this is the ideal set-up no matter the weight of the rider, because it also minimizes tire deflection in the banking. The only reason to go to a wider tire is if the surface requires it. This could be due to surface roughness, to maintain control, or a lack of traction, requiring more rubber in contact with the surface. Going lower in pressure on a larger tire does allow for less extreme tire deformation, but now you've increased your contact patch, which increases rolling resistance.

About 18-20 years ago is when the idea of going wider really started to set in. Better testing brought about some new info for top riders at the time. We learned that going a little bigger actually dropped rolling resistance on the road, so we started to see more 23mm tires. Then Vittoria started to make "open tubulars" from the carcasses of their best glue up tires, and those were even faster than the larger tubs. Top TDF road pros were using clinchers for TTs because they exhibited a lower rolling resistance to the tubulars available at the time (due to the way a clincher sets up on a rim vs a tubular, allowing less sidewall deformation) which went against the mantra of tubulars being better rolling than clinchers. They still used tubs for road races because the tires rode more comfortably over the long haul than clinchers, and they were lighter, and still reigned supreme in that usage until tubeless came along.

You can set up your own rolling resistance "experiment" at home if you have a relatively accurate power meter and you can hold a constant speed on rollers. I did this about 18 years ago when things were just starting to get "shaken up" with tires on the road scene. I trained on a very poor track most of the time, and also on the road. I also ended up competing on many different types of tracks and surfaces, which ended up "necessitating" different wheel set ups. I had training clinchers that were 25mm wide (max 135psi), a front tri-spoke that had a 19mm tub (220 psi), a rear disc with a 20mm tub (220 psi), Zipp 404 tubs with 22mm F+R (220 psi), and a racing clincher set that was on 40mm rims and had 22mm Conti Supersonics (145psi), as well as a gaggle of other wheels that saw occasional use, but the aforementioned wheels are what I had tested. I had my bike set up with an SRM at the time, and ended up riding each set of wheels (with the max pressure) on my rollers at 40km/h to see what the wattage output was like. The reason I used rollers is because they accentuate rolling resistance more than a flat surface does (three short contact patches with way more deformation, vs two long contact patches with less extreme deformation). The big take away from that test was higher psi was better than lower, and smaller tire was better than wider, unless the psi was similar, then wider was better (I did run my 22mm tubs down at 150psi to compare to the Supersonics, then at 135 psi to compare to my training clinchers). You need quite a big jump in PSI to make up for a smaller contact patch. I don't remember the exact wattage savings, but they were noticeable, and if I can recall correctly, I needed about 165/170 psi in the 22mm tubs to be similar to the 25mm clinchers. Ideally, to do the test properly I would have had to drive the rear wheel with an electric motor for constant output while I sat on the bike, but that wasn't going to be an option for me at the time.

If you're a nerd like me about these things, I believe Alex Simmons of Australia has done testing like this as well, except on an actual wooden track with better equipment than I had. This is a quote of his lifted from the CyclingNews Forum. It doesn't validate my testing, but it gives you some more info to follow down the rabbit hole if you choose to keep going.

"Andy Coggan has a really neat chart showing real world (i.e. road) Crr vs Al's roller test numbers for a range of tyres with a range of Crr values. It's a really nice linear correlation:

Training and Racing With a Power Meter Journal: Crr - roller vs. field test results, part 2

and part I of that item:
Training and Racing With a Power Meter Journal: Crr - roller vs. field test results

You will see that testing on the rollers to assess relative Crr translates well to relative Crr on the road."
taras0000 is offline  
Likes For taras0000: