Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More • Hacker News Board

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#121

Post by seadan83 » Thu, May 16, 2024, 5:11 PM UTC

basil-rash wrote: post #101

ActorNightly wrote: post #78

Earlier quoted context omitted.

Same fitness on a more efficient bike = longer distance or higher speed.

To what end?

Travel far, see more.

Sometimes people riding bikes are in a rush (eg: morning meetings and commuting. [And no, drinking is not always a solution, in my situation it's a 30 minute drive or bike ride either way, and driving then costs $30/day and the time to find parking makes it slower. The drive Honda will be usually faster but has to be after 6pm, otherwise it is an hour to get home. This is a 10 mile commute I'm describing, and fir about 6 hours out if the day it's a traffic jam half of the way)

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#122

Post by wiredfool » Thu, May 16, 2024, 5:14 PM UTC

pmontra wrote: post #114

wiredfool wrote: post #82

Earlier quoted context omitted.

I bet if you ran the same tires in 42 and 28, you'd be basically at the same speed, at least on smooth roads.

The 28 wheel feels immediately faster. It's lighter, so it accelerates faster than the 42 one and there are a lot of accelerations from low speed in a ride, especially for slow riders like me. On the other side the 42 wheel should be better at keeping the speed because of the higher mass and inertia. Unfortunately that's wasted each time I use the brakes or I slow down.

Are your 28 and 42 tires the same type (e.g., the Rene Herse standard tires are the same construction across the entire size lineup), or is the 28 a road tire and the 42 a gravel tire?

I've got a road bike and a gravel bike. A while ago, I did the same workout, 12 reps of a local hill, 2.5 hours or so, once on each bike, separated by a week.

The road bike is 8kg and 25mm tires, the gravel is 12kg and 650bx42 or 48 tires. (might have been either, as I switched tires around then). The difference in time was 6 seconds.

The gravel bike doesn't feel as fast. It doesn't reward spinning, and the gearing jumps are just a little big for me (1x11). The road bike beats me up with vibrations, but it feels better climbing and standing. It's got closer gear ratios, so it's just a bit better matching. Now, to be fair, the gravel bike is running far better tires, so there's less resistance there. (and, that's basically why I bought it) But overall, they are basically the same speed, even on a hilly climbing workout.

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#123

Post by seadan83 » Thu, May 16, 2024, 5:17 PM UTC

bluecalm wrote: post #41

ActorNightly wrote: post #23

Earlier quoted context omitted.

> something softer can absorb more of the little bumps (and also perhaps not fatigue the rider as much from a bumpy ride). Not quite. You can air down narrower road tires for this. The difference is that a wider tire (i.e a tire with more volume) is going to be more efficient at lower psi, because of a wider contact patch that ends up spreading the load out more and deflecting the tread less. This effect definitely i…

I feel the same about suspension but maybe it's just very hard to design. It would need to be very light and aero to make it worth it for road bikes which are pretty great on roads as they are. For gravel there is the Lauf suspension thing and the new light/short suspension forks but I am not surprised they are not very popular as a suspension fork means regular expensive maintenance. Why not just slap 2+ inch MTB ti…

You may want to look into dropper seat posts. They have road versions that are relatively stiff.

Suspension weighs like 2 lbs (_very_ heavy) and can fail/needs maintenance, and for small bumps the shock absorber moving around loses a lot of power transfer. Nicer suspensions have lock outs so you can disable the suspension on roads and flip it back on when you're back in the mountains.

Fir road only, I don't think suspension ever would make sense. Fatter tires and a (for road) dropper seat post will likely give you all the suspension you need with little penalty

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#124

Post by seadan83 » Thu, May 16, 2024, 5:25 PM UTC

ActorNightly wrote: post #68

scott_w wrote: post #60

Earlier quoted context omitted.

> a narrower tire is going to usually be better, because you gain the aerodynamic advantage Testing has shown this to not be true. Width is less important than overall shape of the tyre/wheel/bicycle interface when it comes to aerodynamics.

Then everyone in the peloton for races like Paris Roubaix would be on 38c gravel tires. The reason they run 28c is because while it sucks for cobblestone, there sre flatter sections where the aero advantage is worth it. Per 10mm tire width increase, you are getting 10 watts more aero drag at 25 mph.

Elite riders and teams are very conservative. They shift to new tech after it has been proven over decades.

Consider that from a programming perspective, imagine using no tech newer than 2004.

The transition to 28s took a long time itself

> Per 10mm tire width increase, you are getting 10 watts more aero drag at 25 mph.

Interseting, where can I read more about this? I don't think this conclusion lines up with either the article, or the research from rene herse. Travel surfaced also matters quite a it, I could see that maybe being true in an idealized setting.

There is more to it. Tire needs to be in contact with ground to transfer power. A skinny high PSI tire will spend a lot of time bouncing. Just one example of how other real world factors can be more significant.

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#125

Post by bennyelv » Thu, May 16, 2024, 6:45 PM UTC

seadan83 wrote: post #115

bennyelv wrote: post #53

Earlier quoted context omitted.

Unfortunately you cannot discount the “sponsor effect” here. Wheel manufacturers have been pushing wider rims because it helps them sell another set of wheels to everyone. In the days of rim brakes a wheel had a finite life (the length of time it took to wear down the braking surface). Then shimano and the frame builders pushed everyone to disc brakes, so the wheels now last for ever. What do you know, 2 years later…

As for evidence, here you go: https://www.renehersecycles.com/why-wider-tires-are-not-slow... The aero drag of wider tire is not a lot. It is more the wider tires are not slower. Wider tires allow: more air volume in tire, lower PSI. In turn those help ride quality.

The aero drag is the elephant in the room here. By this study’s measurements there wasn’t much difference, but what was the width of the rim they used with the narrow tyre?

A narrow tyre on a wide rim is a wide tyre. They don’t explain or address this issue. I suspect they would have used a wide rim with all the tyres, which is notionally a sensible thing to do, but in reality it’s completely flawed.

What are the results if you used a narrower rim with the narrower tyre so that the frontal area was actually reduced as much as it could have been?

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#126

Post by bennyelv » Thu, May 16, 2024, 6:56 PM UTC

seadan83 wrote: post #117

bennyelv wrote: post #107

Earlier quoted context omitted.

I don't share your optimism about the strength of the scientific method in pro-cycling :) It's not too long ago (admittedly in the pre-disc brake era) that climbers would have their bike built up to sub 6.8kg and then add weight to it to bring it up to the limit rather than use deeper wheels. If you look at TT equipment all team members use the same helmet regardless of the fact that helmet performance varies massive…

> Why is nobody wearing a TT Helmet and visor on a normal road stage? (1) weight is not always worth it, notably when there are lots of climbs (2) riding with others, need to be able to turn your head. Further, you can't get as super low when in a big group. It also doesn't help as much because the group dynamic is more important than crouching extra low and/or helmet drag (3) out of the saddle sprints.

Definitely not every road stage, but on a flat stage if your aim was to break away and stay away you should absolutely do surely?

Nobody ever has…

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#127

Post by seadan83 » Thu, May 16, 2024, 7:17 PM UTC

bennyelv wrote: post #126

seadan83 wrote: post #117

Earlier quoted context omitted.

> Why is nobody wearing a TT Helmet and visor on a normal road stage? (1) weight is not always worth it, notably when there are lots of climbs (2) riding with others, need to be able to turn your head. Further, you can't get as super low when in a big group. It also doesn't help as much because the group dynamic is more important than crouching extra low and/or helmet drag (3) out of the saddle sprints.

Definitely not every road stage, but on a flat stage if your aim was to break away and stay away you should absolutely do surely? Nobody ever has…

To break away requires you to put out 30% more power than the person behind you, and then also means you need to put out 30% more power than the rest of the field. That is a good recipe to go out hard, overcook, and then get passed up by the entire peloton.

The 30% - Drafting is good for a 30% power increase. When in the middle if a peloton, even more. The breakaway plan can make sense, but not by fooling around in a TT helmet in the middle of a peloton for a few hours first.

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#128

Post by seadan83 » Thu, May 16, 2024, 7:42 PM UTC

bennyelv wrote: post #125

seadan83 wrote: post #115

Earlier quoted context omitted.

As for evidence, here you go: https://www.renehersecycles.com/why-wider-tires-are-not-slow... The aero drag of wider tire is not a lot. It is more the wider tires are not slower. Wider tires allow: more air volume in tire, lower PSI. In turn those help ride quality.

The aero drag is the elephant in the room here. By this study’s measurements there wasn’t much difference, but what was the width of the rim they used with the narrow tyre? A narrow tyre on a wide rim is a wide tyre. They don’t explain or address this issue. I suspect they would have used a wide rim with all the tyres, which is notionally a sensible thing to do, but in reality it’s completely flawed. What are the res…

Rene herse has been doing those tests since 2006 "back when go-fast tires were 23mm." They covered a lot of variety and their conclusion is the aerial drag is tiny and real world conditions are more important than the idealized condition of tests on a steel drum.

The tests in the reference were done with a 21mm inner rim width. I believe that is neither super wide nor narrow. Arguably a good test bed rim to isolate the difference in tire.

Though, wide rim equates to a wide tire I do not think is true (at least, unsupported). The deep dish rims are only aero if the width is close to that of the tire. Reducing the ratio of tire width to rim width is aero! If anything, a wider deep rim on a skinny tire is increasing are dynamics. The aero dynamics of a wheel is not just a function of the tire alone. A deeper dish of more equal width to the tire helps that teardrop shape you want for aerodynamics.

My knowledge of tire/rim ratio comes from conversations primarily. References for that ratio being important are not hard to come by, eg: https://silca.cc/blogs/silca/part-5-tire-pressure-and-aerody...

The reference does go into some more detail why wide rim is desirable to reduce drag. I won't paraphrase further here other than to conclude a wider rim would actually be favorable for the skinny tire.Regardless, a middle of the road rim width was used in that data sample.

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#129

Post by tpm » Thu, May 16, 2024, 7:42 PM UTC

seadan83 wrote: post #118

tpm wrote: post #113

Earlier quoted context omitted.

> Why is nobody wearing a TT Helmet and visor on a normal road stage? Because it doesn't work as much alone as in combination with specific aero body position. But you can't be in that position in a normal road stage because the aero handlebar extensions are forbidden in mass start stages. Also there are less aero benefits to be had when you ride in the peloton behind other riders.

You don't need aero bars to have you arms forward and narrow. It's not particularly safe, but doable for a while. The aero bar question (whether to have them or not) comes down to how long you will spend drafting and climbing. It's a more interesting decisions in Olympics and triathlons than most road bike racing (the latter it makes no sense because people are drafting as much as possible).

Arms forward and narrow, forearms on handlebar is a banned position of course :)

https://www.cyclingweekly.com/news/racing/uci-publishes-imag...

Re: Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

#130

Post by bluecalm » Thu, May 16, 2024, 10:16 PM UTC

seadan83 wrote: post #120

bluecalm wrote: post #36

Earlier quoted context omitted.

Gravel bikes are going to transform in coming years as now they are neither very comfortable nor fast. It turns out that wider MTB tires are both faster (when it comes to rolling resistance) and way more comfortable and safer than gravel tires even on tarmac, let alone any kind of terrain. The reason is that soft casing is way more important than knobs when it comes to rolling resistance and MTB tires can be made sof…

Salsa cut-throat is a gravel bike, fits 2 inch tires. Personally, I find having drops to be more comfortable because you can change hand position. Look to tour divide bikes for gravel bikes optimized for comfort and fatter tires. I don't understand your prediction for an imminent transformation.

My prediction is that gravel bikes will have wider forks and people will put MTB tires in them instead of 40mm "gravel" tires they do today. It will be faster, more comfortable and safer. Drop bars are great, they will stay. You don't need an MTB bar for your typical light off-road terrain.