ofajen

Likely not in my case. My bikes live in the unheated garage, the doors are often open and bikes are fairly close to outside temps. But the point is well taken, I can check that by taking my good pressure gauge and checking at the midpoint of a ride.

Otto

Trakhak

RChung anticipated and fully addreseed that argument at the end of his post:

"Statistical analysis can be your friend, if you know what you're doing. Then, to validate the analysis we make predictions based on what we learned, and run another experiment. If the prediction is borne out, that's good. If it's not, that's even better, because it means we learned something new."

What do you propose as an alternative to statistical analysis?

cyclezen

Good Questions !
1. I don;t really think (IMO) that GP4Ks are 'thin' (Don;t have nor looked at GP5K) , consider them std, as my current Rubino Pros... just because a casing is higher thread count, doesn't make them 'thinner'- they might be a bit more supple, but not like tubulars. I consider thin a good cotton tubular, which has almost no coating on the sidewall casing...
2. most recent measure on the Rubino Pros on my HED Kermesse was 25.3 ish (small, visual scale caliper).
Even so, I tried changes in some of these parameters to see what kind of variance they indicated in psi. Most produced no more than a 1.5-2 lb psi variance, +- 2%...

It was just a fun experiment to use/try both. Might have made me re-consider what I'm currently riding - but then EVERYTHING makes me 'reconsider' everything I have as settings... LOL!
Like saddle setback, height, stem stack/length... LOL ! even cleat rotation... although experience has shown/warned/slapped in in the knees to NOT screw with my current rotation tooo much! LOL! been a lifelong affliction... LOL!
My 'come away' is that either calculators are a good starting point to considering everything in your own setup - makes one realize what all comes into play....
Then trying and deciding on your own, with your own 'results' will help one confirm what they settle on.
We all have routes we ride more regularly, which might have a broad profile for our riding type. Somewhat equalized conditions, done with multiple iterations, will get us to some weighted balance/consideration for 'speed' vs' comfort'.
Having both is proving helpful to me because I've recently gotten back into frequent mtb riding, and some 'updating' on my bikes... so, been using the ZIPP calc to 'find' a good inflation range for the 'new' wheels and tires/conditions/riding style (as in 'more cautious'... LOL)
Ride On
Yuri

Sy Reene

Yeah, on #1, I don't know what constitutes 'thin'. It does change value on Zipp's calculator by a significant amount though, adding 7-8 psi I think over standard.
On Silca's calculator meanwhile, a 26mm measured tire returns 5psi less than a 25mm tire for your scenario. So, both of these input changes cumulatively would bring them inline with one another.

KerryIrons

Actually no. BQ does side by side comparisons of tires with the same casing, rubber compounds, and tread patterns with the only variables being width and pressure. If you actually studied the literature instead of posting your biases, you might learn something. Good job changing your post when you were shown to be spouting rather than providing data or logic.

RChung

I haven't. I ride when it gets cold but I'm not eager to do much testing when it's cold (there's some standing around recording stuff and making notes) so the range of temperatures I've tested in are generally from around 10C (50F) up to maybe 25C (80F). My general rule of thumb is that each increase in temp of 1C decreases Crr by a bit more than 1% of its baseline value, and in the range of 10C to 25C it appears relatively linear.

I know Josh has done some testing on roads at Paris-Roubaix just before the race, so he's tested in cold weather -- but he gets paid for it. I don't, so I prefer to test when it's a little more comfortable.

ofajen

As you probably know (but I didn’t) elastomers are characterized by the TR-10 test for low temperature service, like for seals. The sample is stretched and frozen and then brought up to the temperature where it starts to regain elasticity and contracts by 10%. Looks like -40 (F or C!) is a typical TR-10 for butyl rubber. So between that point and 10 C it is going to have probably a curve of elasticity but whether things start to fall apart below 10 or much colder I don’t know.

Also, I hear you about standing around in the cold. I didn’t buy new Rat Trap Pass tires when I wore the first set out, partly because they are so hard to take on and off and I didn’t want to deal with them if I got a flat at freezing temp. My rear tire on the RockHopper is a Speed King that comes off and goes on without using levers or even much hand strength.

Thanks for sharing your work and insights.

Otto

AJW2W11E

..

Calsun

In terms of bike speed 99% of the effort is to overcome air drag and not rolling resistance. Rolling resistance is also constant but air drag increases geometrically with speed. There is 4 times as much air drag at 20 mph as at 10 mph and then if there is a head or cross wind (two thirds the vector force of a head wind) that adds to the air drag as any rider can attest.

asgelle

It would really be better if instead of making things up, you sat quietly and learned from the people who know what they're talking about, e.g., https://www.sheldonbrown.com/rinard/aero/formulas.html .

ofajen

Here’s the figure that shows the components of drag in relation to total drag as a function of speed.





Otto

Sy Reene

That does it, I'm hunting online tomorrow for some 21mm tires.