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25mm to 28mm road tire

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25mm to 28mm road tire

Old 07-08-19, 09:26 AM
  #26  
JohnJ80
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Originally Posted by sirjag View Post
Thank you Sir. So i need to experiment with different pressure and go with what feels the best while not breaking the edge seal of the tire (too low pressure).

JAG
I think so - it's a bit of a trial and error. In the podcast I referenced, Poertner suggest that filling the tire up past where you think it should be and then dropping 5psi until the higher frequency road buzz goes away will be the fastest but it won't feel that way because we're conditioned to think the higher frequency feeling is faster when it's not. His point was to do that over a known route and evaluate.

Originally Posted by Sy Reene View Post
Not sure I understand how Enve, as a performance-based marketer, derives their charts though. Eg. looking at an SES 3.4 chart.. 25mm tire, 150lb rider, inflation of 60psi. Ok, but how do you reconcile this with eg. data from BicycleRollingResistance, which will show better performance at higher PSIs than 60. Scroll about halfway down: Conti 5kTL
I believe it has to do with surface. Poertner, while at Zipp, has done it both ways. His experience with actual wheels on actual courses with WorldTour riders is what I believe he relies on.

With respect to the Enve charts, I don't know where they get them either but I've been using them and they seem to work well for me in terms of both perceived rolling resistance/power output and comfort. Basically, I think they do a better job accounting for rim width in the pressure calculation than others.

The relatively recent focus on inflation, tire size, rim width etc... is fairly new. I got into it when I had a bike that was just horrible to ride in terms of ride compliance when I mounted it with 23 or 25mm tires inflated to 100psi. I changed forks, seat posts, etc... but still hated the bike. When I went to 30mm tubeless tires an started experimenting with inflation I was pretty shocked to see my average speeds stay the same as on my 16lb road bike and yet the ride was just super plush at a pressure of about 75psi. I've subsequently lowered that to around 65 with equal speed and better comfort. This, on a route that I have ridden more than 800 times over many years on several bikes all with archived data. So I was pretty sure what I was seeing and feeling was true and that the speed data was consistent with what I was experiencing on the bike.

I don't know if that works for everyone, but that's what's worked well for me and it is a definitely an improvement in both speed and comfort.

It's also worthy to note, that I took Poertner's guidance on pump gauge accuracy. I picked one pump (happened to be Silca) and used that as my standard. I then compared my 3 pumps (different brands) and the variance was all over the place when I compared them to the actual pressure in the tire and the Silca gauge. 10psi is a significant difference and eliminating that variance was important.

J.
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Old 07-08-19, 10:05 AM
  #27  
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Originally Posted by Sy Reene View Post
Not sure I understand how Enve, as a performance-based marketer, derives their charts though. Eg. looking at an SES 3.4 chart.. 25mm tire, 150lb rider, inflation of 60psi. Ok, but how do you reconcile this with eg. data from BicycleRollingResistance, which will show better performance at higher PSIs than 60. Scroll about halfway down: Conti 5kTL
BicycleRollingResistance holds the tire rigidly against a drum, the data isn't accounting for the tire's behavior as suspension. Pumping a tire stiffer will always make it deform less against a rolling surface, but in the real world, you tend to get better performance if the tire is deforming around irregularities rather than transmitting deflections to the bike and rider. Comfort is speed; the energy spent making you uncomfortable when tires are pumped too stiff is energy being stolen from your forward momentum. The lighter the rider, and the rougher the surface, the squishier the tires need to be pumped to do their job properly.
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Old 07-08-19, 12:28 PM
  #28  
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Originally Posted by Sy Reene View Post
Not sure I understand how Enve, as a performance-based marketer, derives their charts though. Eg. looking at an SES 3.4 chart.. 25mm tire, 150lb rider, inflation of 60psi. Ok, but how do you reconcile this with eg. data from BicycleRollingResistance, which will show better performance at higher PSIs than 60. Scroll about halfway down: Conti 5kTL
High pressures aren't a great idea on hookless rims. There's more to this than the one thing the BRR guy measures on his test jig.
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Old 07-08-19, 04:55 PM
  #29  
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Originally Posted by HTupolev View Post
BicycleRollingResistance holds the tire rigidly against a drum, the data isn't accounting for the tire's behavior as suspension. Pumping a tire stiffer will always make it deform less against a rolling surface, but in the real world, you tend to get better performance if the tire is deforming around irregularities rather than transmitting deflections to the bike and rider. Comfort is speed; the energy spent making you uncomfortable when tires are pumped too stiff is energy being stolen from your forward momentum. The lighter the rider, and the rougher the surface, the squishier the tires need to be pumped to do their job properly.
fwiw, I think the BRR test puts 95 lbs of weight on the tire, ie. it's not fixed. And the drum has some sorta texture.. no idea what kinda road the drum's texture might emulate though.

Originally Posted by ThermionicScott View Post
High pressures aren't a great idea on hookless rims. There's more to this than the one thing the BRR guy measures on his test jig.
Not sure this isn't another way of saying that if you want to have performance gains thru higher pressure (meaning above 60psi), a hookless rim isn't a good idea.
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Old 07-08-19, 05:14 PM
  #30  
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Originally Posted by Sy Reene View Post
Not sure this isn't another way of saying that if you want to have performance gains thru higher pressure (meaning above 60psi), a hookless rim isn't a good idea.
If I'm tracking all of your negations correctly, we agree on that. Hooked rims are harder to make in carbon, so companies are selling hookless rims and coming up with ex post facto justifications for them. Apparently it didn't take long to forget why hooks were a good idea.
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Old 07-08-19, 05:53 PM
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Originally Posted by Sy Reene View Post
fwiw, I think the BRR test puts 95 lbs of weight on the tire, ie. it's not fixed.
They use a 42.5kg load when setting the wheel in place, but I don't think it's a floating weight during the test. Even if it is, it's obvious from the measured data that it's not picking up suspension effects, since the resistance doesn't start increasing at high pressure (whereas it clearly does in on-road crr measurements).

BRR isn't trying to quantify suspension effects, as they vary by bike and rider and road. BRR is just trying to compare hysteresis between tires.

And the drum has some sorta texture.. no idea what kinda road the drum's texture might emulate though.
The texture will increase the crr by increasing the amount of deformation in the tread, but it doesn't seem to be doing anything else.
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