Tires: How wide is too wide?
#26
Senior Member
Join Date: Aug 2010
Location: Madison, WI
Posts: 11,214
Bikes: 1961 Ideor, 1966 Perfekt 3 Speed AB Hub, 1994 Bridgestone MB-6, 2006 Airnimal Joey, 2009 Thorn Sherpa, 2013 Thorn Nomad MkII, 2015 VO Pass Hunter, 2017 Lynskey Backroad, 2017 Raleigh Gran Prix, 1980s Bianchi Mixte on a trainer. Others are now gone.
Mentioned: 48 Post(s)
Tagged: 0 Thread(s)
Quoted: 3462 Post(s)
Liked 1,468 Times
in
1,145 Posts
If you subtract weight from the bike and attach that same amount of weight to the wheels, so the total bike weight is the same, the bike will not require more work to keep it going. Conservation of momentum.
#27
Senior Member
Join Date: Jul 2008
Location: 25 miles northwest of Boston
Posts: 29,552
Bikes: Bottecchia Sprint, GT Timberline 29r, Marin Muirwoods 29er, Trek FX Alpha 7.0
Mentioned: 112 Post(s)
Tagged: 0 Thread(s)
Quoted: 5224 Post(s)
Liked 3,585 Times
in
2,344 Posts
I once had a 17 mile bike commute. going from home in a somewhat rural suburban area, into the more urban "metrowest" area just outside Boston. almost half of the ride required lots of stops at traffic lights & other intersections. of all the different bikes I used, my fastest time (by 5-8 minutes consistently) was on an old rigid 26er with big fat slicks. bike shop even told me the frame was too small for me. the only thing I could figure, was that it was because I was able to get the bike up to speed quicker, with the smaller diameter wheels, at all the stops. meaning like you wrote, less work to move the bike. the other bikes were typical older 27" road bikes or a roadified 700c hybrid
Last edited by rumrunn6; 07-05-23 at 09:02 AM.
#28
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
What is the reason?
#29
Senior Member
History is against you here. If wheel weight didn’t matter, why not just use steel wheels? They would be much stronger and less prone to the various failures that bicycle wheels experience. Every vehicle from bicycles to trucks have undergone significant weight reduction in the wheels over the last 50 to 80 years. Very few trucks run exclusively steel wheels anymore. Most all of them have aluminum wheels which reduces weight an insignificant amount compared to the weight of an over the road truck…80,000 lb (36,000 kg). An aluminum wheel on a truck is only going to save the truck a few pounds at most but the steel ones are worth replacing due to the weight difference.
Anyway, there are a few reasons why one might consider it important to reduce automotive wheel weight. Though steel rims are still used and are really quite common. Probably half of the cars you see still use steel rims. At least where I live and specifically in the winter.
1) Unsprung weight. While it's relative to the overall weight, less unsprung weight means better working suspension. Considering how big of a challenge good suspension is on cars it's no wonder engineers would want to have less weight to work with.
2) inertial considerations in automotive speeds are pretty different from those in cycling. When you have a wheel and tire system that weighs in the region of 25+kg and you need to accelerate and decelerate it in traffic to speeds of 120+km/h, the weight is actually going to have a small effect on fuel mileage. But if we're being honest, when people choose aluminum rims for their cars, weight isn't typically a consideration. People choose the snazzy looking rims. Steel rims are also still used in trucks in the US. But aluminum rims don't corrode as readily so there's not as much of a risk of air leaks due to mating surface degradation.
So it's not all about weight.
In bicycles aluminum rims are and have always been better. I recently learned that aluminum started to get popular after the second world war and began replacing wood rims without a period of time in between with steel rims having a go as the top dog. Steel has always been the budget option and they're just not as good as aluminum rims so there's no real point in using them. Back in the day the braking surface was worse and had less friction especially in the wet so no real point even to consider them. And these days we have far better extrusion and welding methods for aluminum, and also carbon so steel is really going away fast.
So why not use steel rims in cycling? Steel has never been a serious contender. And it probably won't be.
Just to be clear, I’m not talking about the aerodynamic effects of the tire itself. I’m talking about the force needed to move the bicycle through the air and the impact that having heavier tires and wheels has on the work done. Heavier tires are harder to keep rolling because of the work needed to move them. Work in physics is defined as force acting over a distance. Force is related to mass. For more mass more force needs to be applied over a given distance. Less mass means less force needs to be applied over that same distance. Going back to that automotive example, alloy wheels are used because they require less work and, therefore, less fuel. If the small weight difference has such an impact on a heavy, highly powered vehicle, think of how much impact it has on a lighter, far less powerful vehicle. We are talking hundreds of horsepower (car) vs a fraction of a single horsepower for a bicycle.
It really was interesting to learn that wheel weight isn't really focused on much at all in F1 and that's the highest automotive racing category out there. The biggest effect it has on automotive racing applications is suspension functionality. But that's kinda how it should be in cycling too. I'm considering on building a set of carbon fatbike wheels not to make the bike lighter but to make the front suspension work better.
Far too much is made of rolling resistance. Yes, it is important but not as important as rotating mass and/or the work needed to move the bicycle. Small differences in rolling resistance might win a bicycle race but we aren’t talking racing here.
#30
Newbie
Join Date: Mar 2012
Posts: 10
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked 0 Times
in
0 Posts
My last tour was mostly on road, but I used 38c because of the "mostly", sometimes there were unsealed and rough tracks I found myself on and/or had to take. I found that thickness quite comfortable on the road for me, but then speed wasn't an issue for me, and capable enough on the unsealed roads + tracks. The biggest hindrance to my progress was constantly stopping to take photos, but that was the point of the tour for me. I believe there's no real hard or correct answer, it's more an approximation of a compromise of competing factors and priorities, and it will probably take some tries and a few units of currency to work it out, depending on how accurate you want the answer to be.
#31
Senior Member
Join Date: Aug 2010
Location: Madison, WI
Posts: 11,214
Bikes: 1961 Ideor, 1966 Perfekt 3 Speed AB Hub, 1994 Bridgestone MB-6, 2006 Airnimal Joey, 2009 Thorn Sherpa, 2013 Thorn Nomad MkII, 2015 VO Pass Hunter, 2017 Lynskey Backroad, 2017 Raleigh Gran Prix, 1980s Bianchi Mixte on a trainer. Others are now gone.
Mentioned: 48 Post(s)
Tagged: 0 Thread(s)
Quoted: 3462 Post(s)
Liked 1,468 Times
in
1,145 Posts
OK, let's put this question slightly more simply: On my unloaded touring bike, I am 1/3 slower going up my local hill with my 55mm Rene Herse slick tires than I am with my 38mm Rene Herse slightly more supple tires. Everything else is identical. I am going far too slow for aerodynamics to be significant.
What is the reason?
What is the reason?
Climbing a steep hill, the vast majority of your energy output is countering gravity, lifting you and your bike up higher above the center of the earth. Friction in negligible in comparison.
A scientist would say it is time to redo the experiment and be more careful to make sure independent variables do not screw up the data.
Back to the topic of heavy vs light wheels, it takes more energy to start spinning a heavy wheel than a light wheel, but once spinning, only air and bearing friction will slow it down. Put it on pavement with weight on it and tire friction will also slow it down.
#32
Senior Member
check me on this. apologies for the short story
I once had a 17 mile bike commute. going from home in a somewhat rural suburban area, into the more urban "metrowest" area just outside Boston. almost half of the ride required lots of stops at traffic lights & other intersections. of all the different bikes I used, my fastest time (by 5-8 minutes consistently) was on an old rigid 26er with big fat slicks. bike shop even told me the frame was too small for me. the only thing I could figure, was that it was because I was able to get the bike up to speed quicker, at all the stops. meaning like you wrote, less work to move the bike. the other bikes were typical older 27" road bikes or a roadified 700c hybrid
I once had a 17 mile bike commute. going from home in a somewhat rural suburban area, into the more urban "metrowest" area just outside Boston. almost half of the ride required lots of stops at traffic lights & other intersections. of all the different bikes I used, my fastest time (by 5-8 minutes consistently) was on an old rigid 26er with big fat slicks. bike shop even told me the frame was too small for me. the only thing I could figure, was that it was because I was able to get the bike up to speed quicker, at all the stops. meaning like you wrote, less work to move the bike. the other bikes were typical older 27" road bikes or a roadified 700c hybrid
other personal reactions Ive had from changing tires on same bike go from over 30 years ago taking off some treaded 32mm on my light tourer and putting on some much lighter 28 slicks--I still remember clearly the fun feel of riding on them initially, and how the bike felt so much more alive.
Recently I changed out my fatbike tires, very light 4in ones (some of the lightest fatbike tires) that for two tires are about 2180g, to some much knobbier older fatbike tires I bought used for looser snow conditions that both tires are about 3000g, so 800g heavier or almost two pounds more of rotating weight.
Not only is this clearly noticeable lifting the bike, but as a lot of my fatbiking involves short, steep climbs on curvy trails, I really really noticed how the bike is harder to accelerate up these short punchy ups and downs. So speed is absolutely not a factor, but rotating weight and overall weight of bike is clearly noticeable compared to the lighter tires (that also happen to have more flexible sidewalls)
just a couple of my observations 30 years apart.
for touring, well, for touring on mostly regular reasonable roads, with a medium load (we are talking panniers here, so 25-40lbs) I also find that a 40mm ish is a good compromise. Ive toured a lot on fatter, but was carrying more stuff and also was expecting to be on much rougher roads etc in far off countries, so really liked the 45-50mm ish width and cush, but these also were tires that roll quite well, ie not heavy thick things--the main factor here.
Likes For djb:
#33
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
#34
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,369
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6222 Post(s)
Liked 4,222 Times
in
2,368 Posts
Everyone keeps acting like these are only small forces to consider. Tire hysteresis is probably trivial especially if the tire is inflated so that the tire is stiffer. However, aerodynamic drag is the greatest opposing force we experience. High school and college physics tell us to neglect aerodynamic forces for demonstration purposes because it makes the math so much easier but in the real world we can’t…nor should we…neglect them.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
#35
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
Some numbers:
My 38mm Barlow Pass EL tires (x2): 700 g
My 55mm Antelope HIll Endurance Plus tires (x2) : 1140 g
Mass difference: 440 g
Mass of bike plus rider plus kit: 104326 g
Fractional difference: 0.004
For reference, the difference between a full and empty half liter water bottle: 500 g.
It isn't the tire mass.
My 38mm Barlow Pass EL tires (x2): 700 g
My 55mm Antelope HIll Endurance Plus tires (x2) : 1140 g
Mass difference: 440 g
Mass of bike plus rider plus kit: 104326 g
Fractional difference: 0.004
For reference, the difference between a full and empty half liter water bottle: 500 g.
It isn't the tire mass.
#36
Senior Member
Join Date: Aug 2010
Location: Madison, WI
Posts: 11,214
Bikes: 1961 Ideor, 1966 Perfekt 3 Speed AB Hub, 1994 Bridgestone MB-6, 2006 Airnimal Joey, 2009 Thorn Sherpa, 2013 Thorn Nomad MkII, 2015 VO Pass Hunter, 2017 Lynskey Backroad, 2017 Raleigh Gran Prix, 1980s Bianchi Mixte on a trainer. Others are now gone.
Mentioned: 48 Post(s)
Tagged: 0 Thread(s)
Quoted: 3462 Post(s)
Liked 1,468 Times
in
1,145 Posts
Some numbers:
My 38mm Barlow Pass EL tires (x2): 700 g
My 55mm Antelope HIll Endurance Plus tires (x2) : 1140 g
Mass difference: 440 g
Mass of bike plus rider plus kit: 104326 g
Fractional difference: 0.004
For reference, the difference between a full and empty half liter water bottle: 500 g.
It isn't the tire mass.
My 38mm Barlow Pass EL tires (x2): 700 g
My 55mm Antelope HIll Endurance Plus tires (x2) : 1140 g
Mass difference: 440 g
Mass of bike plus rider plus kit: 104326 g
Fractional difference: 0.004
For reference, the difference between a full and empty half liter water bottle: 500 g.
It isn't the tire mass.
#37
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,369
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6222 Post(s)
Liked 4,222 Times
in
2,368 Posts
I'll preface this by stating that far more competent people than me have figured this stuff out, so I'm really just parroting the fairly obvious conclusions. For example peterhski stated that in formula 1 racing the rotational weight of wheels and tires is considered but it's really only a very minor consideration. There was talk of orders of magnitude less important than other stuff. I don't have time to go look it up, but it's all there in the general discussion forum.
Anyway, there are a few reasons why one might consider it important to reduce automotive wheel weight.
1) Unsprung weight. While it's relative to the overall weight, less unsprung weight means better working suspension. Considering how big of a challenge good suspension is on cars it's no wonder engineers would want to have less weight to work with.
2) inertial considerations in automotive speeds are pretty different from those in cycling. When you have a wheel and tire system that weighs in the region of 25+kg and you need to accelerate and decelerate it in traffic to speeds of 120+km/h, the weight is actually going to have a small effect on fuel mileage. But if we're being honest, when people choose aluminum rims for their cars, weight isn't typically a consideration. People choose the snazzy looking rims. Steel rims are also still used in trucks in the US. But aluminum rims don't corrode as readily so there's not as much of a risk of air leaks due to mating surface degradation.
In a 90 kg bicycle/rider system, the difference between the tires Polar OBark is using is only 360g but that is 0.4% of the total weight of the bicycle/rider system. And, let’s not forget that a motor vehicle has massive amounts of power available that a bicycle’s power plant does not.
So it's not all about weight.
In bicycles aluminum rims are and have always been better. I recently learned that aluminum started to get popular after the second world war and began replacing wood rims without a period of time in between with steel rims having a go as the top dog. Steel has always been the budget option and they're just not as good as aluminum rims so there's no real point in using them. Back in the day the braking surface was worse and had less friction especially in the wet so no real point even to consider them. And these days we have far better extrusion and welding methods for aluminum, and also carbon so steel is really going away fast.
So why not use steel rims in cycling? Steel has never been a serious contender. And it probably won't be.
So why not use steel rims in cycling? Steel has never been a serious contender. And it probably won't be.
Even with my limited knowledge of physics I know that the mass of an object is related most of all to accelerations (and decelerations, but aren't those kinda the same thing?). But once you get a heavier object going, it is going to travel farther than the lighter object, all other factors being equal. That's kinda how ballistics work (not an expert, even though I am a trained artillery section leader). So on a flat stretch of road heavier wheels or tires are not going to have any practical effect on how much energy it takes you to keep them going. On a hill the added weight is going to require more energy, but you need to compare that against the system weight. In accelerations it gets interesting. With my weight, an added kilogram in tires is going to require something in the region of 1 to 2 watts more to get to 25kph than if that same kilogram was on the frame. But once I'm up to speed it takes exactly zero watts more to maintain that speed, because once an object starts moving it keeps moving unless acted upon by an external force. And in this case the external forces acting would be wind resistance, rolling resistance and bearing friction.
Even if you keep pedaling, it’s almost impossible to maintain a “steady speed”. I’ve ridden the Seney Stretch in Michigan. It’s 25 miles of dead arrow straight road that starts at 740 feet and ends at 790 feet. It is about as flat and straight as you can get just about anywhere in the world. No corners and it rises 0.0045” per foot of travel. That’s roughly the thickness of a sheet of paper per foot of travel. Theoretical physics says that I should have been able to just push off at Seney and coasted to Shingleton. I truly wish that were true. I pedaled the entire distance. You can see the speed trace below. My speed went up and down constantly and any amount of coasting was met with an instant decrease in speed. The reason? Punching through 12,000 cubic feet (340,000 liters) per minute.
Physics works and I use it all the time. But we are done a disservice in our education of physics when we don’t at some point take into account those factors that we ignore.
It really was interesting to learn that wheel weight isn't really focused on much at all in F1 and that's the highest automotive racing category out there. The biggest effect it has on automotive racing applications is suspension functionality. But that's kinda how it should be in cycling too. I'm considering on building a set of carbon fatbike wheels not to make the bike lighter but to make the front suspension work better.
Well, it would turn out that rolling resistance is far more important than weight but also not as important than aerodynamics. But if we exclude aerodynamics since this is the touring forum and a four pannier bike is a sail, rolling resistance wins. So it's actually smarter to get the slightly heavier wider tire and be comfortable (and faster) than using a narrower tire in order to save weight. Then again the narrower tire can have a lower rolling resistance for the conditions, so it does get complicated. Thus, it's better to just choose width according to conditions and rolling resistance. Weight of the tire really isn't that important.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
#38
Senior Member
Join Date: Oct 2015
Location: San Diego, California
Posts: 4,077
Bikes: Velo Orange Piolet
Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 2228 Post(s)
Liked 2,011 Times
in
972 Posts
Here are the numbers from bicyclerollingresistance.com for Rene Herse gravel tires that are available to me:
It looks like the closest matches to the tires in question (55mm heaviest vs. 38mm lightest) are the 44mm heaviest and the 44mm lightest - 28w resistance for the 44 heaviest and 16.3w for the 44 lightest (@extra low pressure) - difference ~12w. I can see the RR difference between 55mm heaviest and 38mm lightest being around 25w.
So if you're putting out 75w the elapsed time difference could be around 33%. If you're putting out 150w I don't know how to make sense of these numbers.
It looks like the closest matches to the tires in question (55mm heaviest vs. 38mm lightest) are the 44mm heaviest and the 44mm lightest - 28w resistance for the 44 heaviest and 16.3w for the 44 lightest (@extra low pressure) - difference ~12w. I can see the RR difference between 55mm heaviest and 38mm lightest being around 25w.
So if you're putting out 75w the elapsed time difference could be around 33%. If you're putting out 150w I don't know how to make sense of these numbers.
#39
Senior Member
People in cycling especially are obsessed with weight because it does matter. Wheel weight doesn't. Or rather wheel weight matters as much as any other weight. Then there are the old misguided myths that make wheel weight the enemy no. 1 of cycling. But making you wheels lighter is pretty much the same as making the frame or rider lighter. If you can take weight off components, the pros do. If you can take weight off wheels the pros do. The frame? Same. But none of those is really more important than the other.
Also the pros are beginning to favor aero over weight even on climbing stages. Aero is king and compared to that everything else is almost inconsequential.
You're misunderstanding the physics of all this. Mainly you seem to think that cycling is a constant acceleration. It's typically not though. There's some accelerations, some decelerations and a lot of maintaining speed. However even when accelerating wheel weight has such a tiny effect compared to static weight that it's a nonissue.
An example. If I take my regular touring load I need around 113 watts to get from zero to 20kph in twenty seconds. That's without any resistances so just the pure energy required to accelerate to that speed. If I add 1kg to each wheel at the outer rim I suddenly need a whopping 116 watts so 3W more. What an incredible difference.
We can exclude aerodynamic drag and other resistances since in this example they simply aren't relevant. And if you're gonna state something about micro accelerations, well, 3W on a big one. Less with micro, and the increased rotational inertia of a heavier wheel balances those out anyway.
If a kilogram per wheel has a whopping 3W difference, rolling resistance difference between tires can easily be 20+W per tire. So I'll stick to focusing on rolling resistance instead of weight.
Also the pros are beginning to favor aero over weight even on climbing stages. Aero is king and compared to that everything else is almost inconsequential.
You're misunderstanding the physics of all this. Mainly you seem to think that cycling is a constant acceleration. It's typically not though. There's some accelerations, some decelerations and a lot of maintaining speed. However even when accelerating wheel weight has such a tiny effect compared to static weight that it's a nonissue.
An example. If I take my regular touring load I need around 113 watts to get from zero to 20kph in twenty seconds. That's without any resistances so just the pure energy required to accelerate to that speed. If I add 1kg to each wheel at the outer rim I suddenly need a whopping 116 watts so 3W more. What an incredible difference.
We can exclude aerodynamic drag and other resistances since in this example they simply aren't relevant. And if you're gonna state something about micro accelerations, well, 3W on a big one. Less with micro, and the increased rotational inertia of a heavier wheel balances those out anyway.
If a kilogram per wheel has a whopping 3W difference, rolling resistance difference between tires can easily be 20+W per tire. So I'll stick to focusing on rolling resistance instead of weight.
Likes For elcruxio:
#40
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
One other thing I have noticed, in the past, is that comparing RH EL Stellacooms to EL Barlows (both 38mm, 30 g difference per tire, same compound, so pretty much a fair comparison of treaded vs slick), I am reproducibly 10%-20% slower on a 10 mile ride that involves about 1500 ft of climbing (10% to 20% grade in some spots). I think that is a fair approximation of the penalty that I pay purely from treads vs. slicks. It also suggests that rolling resistance might become a much more significant factor as a function of the grade of the path.
#41
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
(This is a testable hypothesis, but is one that would require some effort and about $200. The test would be to get the same tire width and formulation as the Antelope Hill, put them on 650b wheels, or even 26" wheels. )
#42
Senior Member
Just as in bicycles, wheel weight has certainly gone through a reduction and, if something were to come along that would significantly reduce wheel weight in racing, they would glom on to it in a heart beat.
My guess is that the OP knows he's on wider, thicker sidewall, heavier tires. He feels the extra rotational inertia in the steering and thinks he's going slower and working harder so he does go slower. It's mostly just mental with maybe a bit of extra rolling resistance and weight that's slowing him down.
What would be a good way to test this? Thinking out loud here:
- Outfit the bike with a power meter.
- Climb the same bit of road and try to stay on the same line, maybe add a chalk line to follow as closely as possible.
- Make sure the weight of the bike is equalized when swapping between the tires.
- Get a rolling start so you cross the start line at X watts that you hold for the whole climb.
- Try to do it on a day with minimal wind and heat fluctuations.
- Make the climb long enough that a small difference might be seen but not too long to fatigue the rider too much.
- Do the test lots of times.
- Is it better to do a bunch of laps with one set of tires then a bunch of laps with the other set or swap tires between each lap?
- Get some buddies to do it with you to keep you honest and to compare between riders.
#43
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
I don't want to spend the money to do the experiment, but the control would be to put 55mm Rene Herse tires on 650b wheels and to see what the behavior is. My prediction is that they would behave similar to the 38mm 700C tires, because the outside diameters (and thus trail) will be similar to what I have on now.
As for expectation bias, I had originally assumed no penalty with the 700C 55mm tires, so was not expecting such a pronounced effect.
#44
Senior Member
If you look at modern XC race bikes, they've moved to slacker head angles, shorter offset forks, and larger tires. Races are won and lost on the climbs. And yet their bikes have more trail than what they used to ride.
#45
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
If you look at modern XC race bikes, they've moved to slacker head angles, shorter offset forks, and larger tires. Races are won and lost on the climbs. And yet their bikes have more trail than what they used to ride.
Last edited by Polaris OBark; 07-06-23 at 12:25 PM. Reason: added link
#46
Cyclist
Join Date: Jun 2010
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 39 Post(s)
Likes: 0
Liked 16 Times
in
15 Posts
That seems like a significant difference. Was it a smooth course or more varied terrain?
I know my commute can easily vary by 20% or so, with a varietion of as much as 30% at the outside. Weather and temperature definitely affect the time, but my mood is probably even more of a factor.
I know my commute can easily vary by 20% or so, with a varietion of as much as 30% at the outside. Weather and temperature definitely affect the time, but my mood is probably even more of a factor.
#47
Senior Member
Regardless of what I do and don't understand, I've never heard of someone trying to argue that a difference in trail, let alone a small difference, has a huge affect on uphill speed. Like I said earlier, I'm doubtful it does, but it is an interesting theory. The idea does have some merit. If you're weaving a lot more with one tire compared to the other you're essentially riding a longer distance and possibly slowing down too while using energy keeping your balance. But how much further did you go on the two attempts? The old fashioned magnetic wheel sensors could help you calculate it.
#48
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
That seems like a significant difference. Was it a smooth course or more varied terrain?
I know my commute can easily vary by 20% or so, with a varietion of as much as 30% at the outside. Weather and temperature definitely affect the time, but my mood is probably even more of a factor.
I know my commute can easily vary by 20% or so, with a varietion of as much as 30% at the outside. Weather and temperature definitely affect the time, but my mood is probably even more of a factor.
#49
ignominious poltroon
Thread Starter
Join Date: Jan 2022
Posts: 4,051
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2244 Post(s)
Liked 3,445 Times
in
1,804 Posts
Regardless of what I do and don't understand, I've never heard of someone trying to argue that a difference in trail, let alone a small difference, has a huge affect on uphill speed. Like I said earlier, I'm doubtful it does, but it is an interesting theory. The idea does have some merit. If you're weaving a lot more with one tire compared to the other you're essentially riding a longer distance and possibly slowing down too while using energy keeping your balance. But how much further did you go on the two attempts? The old fashioned magnetic wheel sensors could help you calculate it.
(Those same wider tires, and their treaded version (Fleecer Ridge), worked fine on my kid's XC mountain bike. His bike team had to do a lot of on-road riding during training, and we got them because they have good rolling resistance.)
#50
Senior Member
I kind of feel like you didn't go through the whole thread, which is fine, but this is the only explanation I am left with after eliminating others (eg, differences in weight of the tires, differences in rolling resistance, which according to Jan/Rene Herse, are minimal, etc.). It was only when someone else suggested it and I thought about it for awhile that I realized it was actually a plausible hypothesis with a great deal of explanatory power. It is also a testable hypothesis, and at the price of a whole lot of work (including borrowing wheels from a different bike) and $200 on yet more tires, I could indeed test the hypothesis under reasonably controlled conditions, but the explanation is of secondary importance. The main thing is that this touring bike climbs reproducibly better on steep hills with the only change being the two sets of tires; they behave approximately the same on flats and downhills (at least according to my accumulated Garmin/Strava data).
(Those same wider tires, and their treaded version (Fleecer Ridge), worked fine on my kid's XC mountain bike. His bike team had to do a lot of on-road riding during training, and we got them because they have good rolling resistance.)
(Those same wider tires, and their treaded version (Fleecer Ridge), worked fine on my kid's XC mountain bike. His bike team had to do a lot of on-road riding during training, and we got them because they have good rolling resistance.)
I just think if it was a big deal, you'd see racers making efforts to reduce trail to improve their climbing prowess. When in fact trail has increased in racing, both on and off road over the years. But maybe they climb too fast for it to matter?
It's not clear, did you have your son try the 38s and 55s on his bike with similar results to you?