|
Tire weight: simple or complex
Comparing the weights of my Michelin Pilot Sport tires (440gr ea) and my Marathon Greenguard (730gr ea), the difference is 290gr ea which, considering the weight of my 29er, rear rack and somewhat loaded panniers and me, doesn't make much difference (~0.5%). That is the simple consideration of the weight difference. However, given that the tires need to be spun up to speed, is there physics involved that is more complex to suggest that the difference in weight is multiplied because it is spinning and not just simply a static difference like adding more water to your water bottle?
|
I can't provide the math or physics to support it, but my personal experience is that extra weight on wheels makes a big difference. It might not be that big a deal if you are riding on flat terrain or putzing along, but you will definitely notice it on the hills or when accelerating hard.
|
I can provide the math and the physics:
For accelerating, if the extra weight is at the edge (like it is with tires), the extra weight counts as a factor of two. But as you point out, that changes a 0.5% effect to a 1% effect and that's what it really is. On hills, the extra weight is only a factor of 1, so adding 1 lbs of tires is the same as eatting that 16 oz steak for lunch (except that the tires won't make you feel bad :D ). So weight isn't a big deal. What is a big deal is tire composition. Changing from a racing tire to a flat prevention tire can add a lot of rolling resistance and that you'll definitely notice. As I just posted in another similar thread, the heavier tires will have more angular momentum and it's possible (but I can't confirm or deny) that you'll feel that when sprinting hard and wobbling the bike back and forth. So it's possible this is what people mean when they say that heavy tires feel "heavier." Cheers, Charles |
What size tires are you running? My Conti GP4S 700x25c's are only 220g each.
|
Michelin Pilot Sport are 700cx32 and Schwalbe Marathon Greenguard are 700cx35. Yes, I know the Michelin are heavier than average roadie tires and the Marathons are even more so but I'm happy with both. Given current commuting distance/yr, it is likely that the Marathons, my primary tire, will need to be replaced at the end of next year.
|
Originally Posted by cplager
(Post 16109912)
I can provide the math and the physics:
For accelerating, if the extra weight is at the edge (like it is with tires), the extra weight counts as a factor of two. But as you point out, that changes a 0.5% effect to a 1% effect and that's what it really is. On hills, the extra weight is only a factor of 1, so adding 1 lbs of tires is the same as eatting that 16 oz steak for lunch (except that the tires won't make you feel bad :D ). So weight isn't a big deal. What is a big deal is tire composition. Changing from a racing tire to a flat prevention tire can add a lot of rolling resistance and that you'll definitely notice. As I just posted in another similar thread, the heavier tires will have more angular momentum and it's possible (but I can't confirm or deny) that you'll feel that when sprinting hard and wobbling the bike back and forth. So it's possible this is what people mean when they say that heavy tires feel "heavier." Cheers, Charles |
There are two ways to approach this: (1) with paper and pencil, (2) with a bike, your legs and you brain (but not a bike computer).
Using paper and pencil the difference comes out very small. With a bike, your legs and your brain, the difference may be large or small, depending on your riding style and terrain. For me, heavier tires make a big difference in the way it feels to ride the bike. I'm not saying I can't get the bike up to speed just as quickly with heavier tires, I'm saying it feels different. I notice this mostly on days when I'm riding briskly and when I'm going up steep hills. If I'm just cruising along, it's not such a big deal. That said, I do agree with cplager that tire composition is a bigger deal. I would add that heavier tires tend to be constructed in such a way as to have higher rolling resistance than their lightweight counterparts. I don't know how the two tires you're considering compare in this regard. |
If your racing between lights on your commuter.....it makes a difference.Once you get up to speed,there isn't a big difference.
|
The natural course for this thread is now to ask which tires are the best compromise between flat protection and weight/rolling resistance.
|
best if the light tire is easy to dismount to fix the inevitable flat .
|
Originally Posted by Booger1
(Post 16110297)
If your racing between lights on your commuter.....it makes a difference.Once you get up to speed,there isn't a big difference.
Again, tire composition/pressure can make a much bigger difference. |
Originally Posted by fietsbob
(Post 16110501)
best if the light tire is easy to dismount to fix the inevitable flat .
One person's weight to be overcome in accelerating can be another person's weight to sustain momentum once you get going. |
Originally Posted by fietsbob
(Post 16110501)
best if the light tire is easy to dismount to fix the inevitable flat .
Flats happen, they are best dealt with when everything works as sweet as it could. Just in case you're in a dead spot for a cell signal. |
I run 700x38 tires on Lola, and have added tire liners to them. I have noticed a difference in weight, but it is worth it for the extra piece of mind I am provided.
|
Originally Posted by cplager
(Post 16109912)
I can provide the math and the physics:
For accelerating, if the extra weight is at the edge (like it is with tires), the extra weight counts as a factor of two. But as you point out, that changes a 0.5% effect to a 1% effect and that's what it really is. On hills, the extra weight is only a factor of 1, so adding 1 lbs of tires is the same as eatting that 16 oz steak for lunch (except that the tires won't make you feel bad :D ). So weight isn't a big deal. What is a big deal is tire composition. Changing from a racing tire to a flat prevention tire can add a lot of rolling resistance and that you'll definitely notice. As I just posted in another similar thread, the heavier tires will have more angular momentum and it's possible (but I can't confirm or deny) that you'll feel that when sprinting hard and wobbling the bike back and forth. So it's possible this is what people mean when they say that heavy tires feel "heavier." Cheers, Charles I know it doesn't really matter for most of us, since, like you said, a slightly heavier tire only has about a 1% impact. Out of curiosity though, what do you mean about the added weight only having a factor of 1 on the hills? I guess you are talking about downhill and the fact that the extra energy needed for motion in the linear direction is eliminated by gravity, yet the extra rotational work still remains a factor? Is the extra work due to rotation the same no matter what the slope? Also, I wonder if there are some points in a ride when the extra weight actually increases speed or decreases power dissipation, perhaps because of gravity, or maybe even on the flats due to momentum (linear or angular)? |
Originally Posted by turky lurkey
(Post 16116867)
I know it doesn't really matter for most of us, since, like you said, a slightly heavier tire only has about a 1% impact. Out of curiosity though, what do you mean about the added weight only having a factor of 1 on the hills? I guess you are talking about downhill and the fact that the extra energy needed for motion in the linear direction is eliminated by gravity, yet the extra rotational work still remains a factor? Is the extra work due to rotation the same no matter what the slope? Also, I wonder if there are some points in a ride when the extra weight actually increases speed or decreases power dissipation, perhaps because of gravity, or maybe even on the flats due to momentum (linear or angular)?
When climbing hills, people are not generally accelerating, but trying to go a (relatively) constant speed, so you just need to worry about the energy needed to lift the rider, bike, and tires up the hill. And for that calculation, the 100 g of the tires is just as important as 100 g of twinkies you just ate at the last rest stop (o.k. they don't taste as good, but)... If you are accelerating up a hill, then you the factor will be somewhere between 1 and 2 depending on the size of the hill and how fast you are accelerating. Another way of deciding that it isn't the heaviness of the tires that matter: If it were because the tires were heavy, then once you were at speed, you'd find that when you stopped pedaling, you'd roll faster and farther because of all of the energy stored in the rotation of the tires. While measurable, this effect isn't noticeable. On almost all of the tires that people are complaining about them being heavy, the roll-out distance will be shorter because of the increased rolling resistance. |
Cplager, thanks for the reply this is an interesting topic.
I just recently put some rhino dillo tire liners in my 1.5" slick mtb tires. When I read reviews about them many people complain about the weight, some also say they affect the feel/performance/rolling resistance (I suppose the latter argument might have some validity) so far though (after one commute) any perceived difference is minor if not entirely made up in my head. Well there is one big difference, I didn't have to patch a tube yesterday. |
Originally Posted by cplager
(Post 16116913)
If you are moving at a constant speed, then whatever rotational energy your wheels have they will keep. So you won't need to provide any extra energy to keep them moving at that speed.
When climbing hills, people are not generally accelerating, but trying to go a (relatively) constant speed, so you just need to worry about the energy needed to lift the rider, bike, and tires up the hill. And for that calculation, the 100 g of the tires is just as important as 100 g of twinkies you just ate at the last rest stop (o.k. they don't taste as good, but)... If you are accelerating up a hill, then you the factor will be somewhere between 1 and 2 depending on the size of the hill and how fast you are accelerating. Another way of deciding that it isn't the heaviness of the tires that matter: If it were because the tires were heavy, then once you were at speed, you'd find that when you stopped pedaling, you'd roll faster and farther because of all of the energy stored in the rotation of the tires. While measurable, this effect isn't noticeable. On almost all of the tires that people are complaining about them being heavy, the roll-out distance will be shorter because of the increased rolling resistance. Maybe I'm understanding this all wrong, but any time you need to apply enough force to the pedals to make the wheel spin faster (regardless of road speed, which may be dropping, as on a hill) , a heavier tire will require more force than a lighter one. It's tempting to think it's inconsequential, that amount of extra force, but depending on how much effort you put into, and appreciation you have of, going faster and/or with less effort, the more it matters, as it does the greater the weight differential becomes. An extra 100gm per tire over a 210gm lightweight for a 5mi cruise across town matters not, but NOBODY is hammering out a hilly 70 mile ride at high average speeds on 1900gm worth of tires. That ain't happenin'. |
Originally Posted by chaadster
(Post 16120788)
I'm not crispy on the physics, but I don't understand how hill climbing cannot be anything but a series of accelerations, when between each stroke, you not only have rolling resistance slowing you, but also gravity working to pull you back downhill?
That being said, your acceleration when climbing a hill (particularly if you are spinning instead of mashing) is going to be very small, so that the effect of the wheel weight when climbing will be much closer to a factor of 1 (meaning that the weight of the wheel is as important as weight anywhere else on the bike/rider). As far as whether or not it is inconsequential, even with a factor of two, 200g of extra wheel weight is as bad as 400g of extra weight on your bike (which is just under 1 lbs). In my case, I ought to lose about 15 lbs myself, so I'm not going to do anything extreme to lose 1lbs of my bike. Added:
Originally Posted by chaadster
(Post 16120788)
Maybe I'm understanding this all wrong, but any time you need to apply enough force to the pedals to make the wheel spin faster (regardless of road speed, which may be dropping, as on a hill) , a heavier tire will require more force than a lighter one.
A couple important points here: 1) When accelerating a bicycle, you need to not only accelerate the wheels (both linear and rotational sense), but also accelerate the bicycle and the rider. If you compare the mass of the wheels to that of the bike and the rider, you'll see that the wheels are are very small part of a bigger picture. So, yes, it takes more force to accelerate a heavy tire than a light tire, but not (relatively speaking) a lot more force to accelerate a rider, bike, and a "heavy" tire compared to the same rider, the same bike, and a "light" tire. 2) When you are moving at a constant speed, you only need to provide enough power to overcome the frictional forces against you. It will take less energy to keep a heavy but low rolling resistance tire moving than a light but high rolling resistance tire. |
Originally Posted by cplager
(Post 16116913)
If you are moving at a constant speed, then whatever rotational energy your wheels have they will keep. So you won't need to provide any extra energy to keep them moving at that speed.
When climbing hills, people are not generally accelerating, but trying to go a (relatively) constant speed, so you just need to worry about the energy needed to lift the rider, bike, and tires up the hill. And for that calculation, the 100 g of the tires is just as important as 100 g of twinkies you just ate at the last rest stop (o.k. they don't taste as good, but)... If you are accelerating up a hill, then you the factor will be somewhere between 1 and 2 depending on the size of the hill and how fast you are accelerating. Another way of deciding that it isn't the heaviness of the tires that matter: If it were because the tires were heavy, then once you were at speed, you'd find that when you stopped pedaling, you'd roll faster and farther because of all of the energy stored in the rotation of the tires. While measurable, this effect isn't noticeable. On almost all of the tires that people are complaining about them being heavy, the roll-out distance will be shorter because of the increased rolling resistance. Content in here describes acceleration and gravity succinctly: http://en.wikipedia.org/wiki/Equivalence_principle "...So in Newtonian physics, a person at rest on the surface of a (non-rotating) massive object is in an inertial frame of reference. These considerations suggest the following corollary to the equivalence principle, which Einstein formulated precisely in 1911: Whenever an observer detects the local presence of a force that acts on all objects in direct proportion to the inertial mass of each object, that observer is in an accelerated frame of reference." When changing 'gravity' acceleration happens. If for simplification, one can remove aerodynamics and friction/rolling resistence, then simply, the pedal stroke you provide to travel uphill provides the change of force. When that mass no longer accelerates from the pedal stroke, you stop and reach equilibrium. This is also true on a plane where the force of gravity remains perfectly constant, you would travel at a constant speed, if it were not for friction (road/machine/aero). Basically a satellite which farts... If you were to move that satellite further away from earth's gravity, you'd have to accelerate it. Same as climbing a hill... As one rides along on a flat road, you are constantly accelerating, because you need to overcome, friction (road/machine/aero). WHich is why MASS (weight in gravitational field) is important. Momentum is quickly eaten up by the friction forces, so the best approach is to minimize MASS, and reduce friction however possible, so that the amount of force you need to create the needed acceleration is minimized. Tire/tube/wheel weight/mass matters a lot, all the time, as does the butterfat we're all draggin along... The human condition is to screw with the Tire/tube/wheel weight/mass more than the other stuff... but anything we do is all good. EDIT: If we were on Barzoom it would all be easier... and that third slice of pizza wouldn;t matter as much. Or riding those Marathon truck tahrs... |
Originally Posted by cyclezen
(Post 16121203)
you use clearly defined terms very loosely, to match you preception, which, of course, is seen through inherent poor vision.
(A whole bunch of gobbledygook removed) I'm not sure what your educational background is, but it's pretty clearly not physics or engineering. Figure out whatever else you might be good at and stick to that. |
We could try a thought experiment in which we ride a bike with heavy tires up a hill. Or we could actually ride a bike with heavy tires up a hill. I've done the latter, and you can feel the weight.
|
Originally Posted by Andy_K
(Post 16121303)
We could try a thought experiment in which we ride a bike with heavy tires up a hill. Or we could actually ride a bike with heavy tires up a hill. I've done the latter, and you can feel the weight.
I've done both, too. And I haven't noticed heavy tires, but I have noticed larger rolling resistance is quite noticeable on hills. If you want to do an experiment, that's fine. Just make sure you're measuring what you think you're measuring (i.e., difference in tire weights and not differences in tire composition/pressure). |
The heavy tires I'm thinking of were 700x50 Schwalbe Marathon Supremes. They're not exactly Ultremos, but they roll pretty well. What were the heavy tires with low rolling resistance that you used?
http://youtu.be/idOyb3kMseI |
Originally Posted by cplager
(Post 16120983)
Nobody rides at a constant speed. There are variations. So, yes, your acceleration is never 0.
That being said, your acceleration when climbing a hill (particularly if you are spinning instead of mashing) is going to be very small, so that the effect of the wheel weight when climbing will be much closer to a factor of 1 (meaning that the weight of the wheel is as important as weight anywhere else on the bike/rider). As far as whether or not it is inconsequential, even with a factor of two, 200g of extra wheel weight is as bad as 400g of extra weight on your bike (which is just under 1 lbs). In my case, I ought to lose about 15 lbs myself, so I'm not going to do anything extreme to lose 1lbs of my bike. Added: A couple important points here: 1) When accelerating a bicycle, you need to not only accelerate the wheels (both linear and rotational sense), but also accelerate the bicycle and the rider. If you compare the mass of the wheels to that of the bike and the rider, you'll see that the wheels are are very small part of a bigger picture. So, yes, it takes more force to accelerate a heavy tire than a light tire, but not (relatively speaking) a lot more force to accelerate a rider, bike, and a "heavy" tire compared to the same rider, the same bike, and a "light" tire. 2) When you are moving at a constant speed, you only need to provide enough power to overcome the frictional forces against you. It will take less energy to keep a heavy but low rolling resistance tire moving than a light but high rolling resistance tire. You also seem to be certain that riders cannot notice, or feel, the weight difference between light and heavy tires, but I don't understand that position, either. If you accept, as you said above, that heavier tires do require more energy to acclerate than lighter ones, why would a rider not be able to sense that difference? We can feel the difference in power it takes to smash a grape under foot, and probably even a tender raspberry, so the idea that we can't feel how much resistance we're facing through the pedals doesn't smack true. I don't know how much force it takes to smash a grape compared to the force it would take to accelerate a 950gm tire versus a 210gm tire (same wheel/gear), so maybe you could address that. Lastly, if you maintain that tire weight doesn't matter, how do you account for the widespread believe that it does, and the pursuit of lightest possible weights in all matters related to energy efficiency in vehicle development, whether bicycles, human powered vehicles, cars, and motorcycles? |
Originally Posted by cplager;16120983...
A couple important points here: 1) When accelerating a bicycle, you need to not only accelerate the wheels (both linear and rotational sense), but also accelerate the bicycle and the rider. If you compare the mass of the wheels to that of the bike and the rider, you'll see that the wheels are are very small part of a bigger picture. So, yes, it takes more force to accelerate a heavy tire than a light tire, but not (relatively speaking) a lot more force to accelerate a rider, bike, and a [I "heavy"[/I] tire compared to the same rider, the same bike, and a "light" tire.
2) When you are moving at a constant speed, you only need to provide enough power to overcome the frictional forces against you. It will take less energy to keep a heavy but low rolling resistance tire moving than a light but high rolling resistance tire. But going downhill, say coasting down, there are a couple of things going on. We're accelerating at least at first, and the angular momentum will slow that slightly. Very slightly. Then the angular momentum and extra weight will allow a higher speed I think depending on the grade. At the bottom our heavier tires will hold the speed better, again because of the rotating momentum. So tally it up: uphill steady, slowed by just the extra weight. Downhill, helped by extra weight AND angular momentum. Flat after, helped by angular momentum, slowed a tiny amount by extra weight. Going back uphill and slowing, helped by the angular momentum and held back by weight. I'm not so sure that it wouldn't be advantageous to have a heavier tire on some type of rolling course. |
Originally Posted by chaadster
(Post 16121888)
I'm at a loss to understand how you can hinge your whole argument on this 'constant speed' concept and how it means the rider doesn't have to input energy to maintain that speed, then concede 'constant speed' doesn't really exist and that riding is, in fact, a series of constant accelerations while pedaling, yet maintain the position that tire weight doesn't matter. Can you explain what I'm missing here?
It's only when you are accelerating from a stop that most of your force is NOT counteracting drag and in that case, the importance of the wheel weight gets (almost but a little less than) a factor of two.
Originally Posted by chaadster
(Post 16121888)
You also seem to be certain that riders cannot notice, or feel, the weight difference between light and heavy tires, but I don't understand that position, either. If you accept, as you said above, that heavier tires do require more energy to acclerate than lighter ones, why would a rider not be able to sense that difference? We can feel the difference in power it takes to smash a grape under foot, and probably even a tender raspberry, so the idea that we can't feel how much resistance we're facing through the pedals doesn't smack true. I don't know how much force it takes to smash a grape compared to the force it would take to accelerate a 950gm tire versus a 210gm tire (same wheel/gear), so maybe you could address that.
There is one caveat here: A heavier tire has more angular momentum and this could possibly (as in, I can't confirm that it isn't) be noticeable when riding the bike in a slalom course or when "pumping" the bike very hard side to side when sprinting. Neither of these are activities that most people do very often, but it can happen. So, in this case, it's possible that somebody might be able to "feel" the heavier tires (but it wouldn't really slow you down much).
Originally Posted by chaadster
(Post 16121888)
Lastly, if you maintain that tire weight doesn't matter, how do you account for the widespread believe that it does, and the pursuit of lightest possible weights in all matters related to energy efficiency in vehicle development, whether bicycles, human powered vehicles, cars, and motorcycles?
Battle Mountain bicycles are not light bicycles. They are aerodynamic bicycles because if you want to be fast, you need to be aerodynamic. If you are racing a bicycle, then these effects can matter. A 0.5% weight effect may not be noticeable by the rider, but it can make a few seconds difference over 100 miles. If you are a professional racer, then I agree it makes sense to worry about these effects (although, again, rolling resistance is a much bigger issue). Finally, I agree that there is a wide-spread belief in bicycling that wheel weight is important. And, except for racers, it's basically wrong. It's as important as it is, it's very quantifiable, and if weight is an issue, most of us should eat a bit less instead of worrying about the weight of the tires on our bikes. For almost all commuters, having a tire that was heavier, but had lower rolling resistance and better flat protection would almost always be a welcome change. Cheers, Charles |
Originally Posted by cplager
(Post 16122675)
There is one caveat here: A heavier tire has more angular momentum and this could possibly (as in, I can't confirm that it isn't) be noticeable when riding the bike in a slalom course or when "pumping" the bike very hard side to side when sprinting. Neither of these are activities that most people do very often, but it can happen. So, in this case, it's possible that somebody might be able to "feel" the heavier tires (but it wouldn't really slow you down much).
|
Originally Posted by cplager
(Post 16122675)
Maybe this is an easier way of thinking about it: When riding at an almost constant speed, almost all of the force you are putting in is being used to counter-act the rolling resistance/aero drag/flex/transmission losses. Only a little bit of it is being used because you are accelerating. In this case, the importance of the tire weight is a factor of (almost, but slightly bigger than) 1.
It's only when you are accelerating from a stop that most of your force is NOT counteracting drag and in that case, the importance of the wheel weight gets (almost but a little less than) a factor of two. In the original case, we were talking about 200 grams extra. Even with the factor of two, that's 400 grams extra (less than one pound). Let's say you have a 20 lbs bike and are 180 lbs. An extra pound is a 0.5% effect. I don't most people here are sensitive enough to notice that. If you weight 100 lbs and have a 10 lbs bike, we're still talking an effect smaller than 1%. There is one caveat here: A heavier tire has more angular momentum and this could possibly (as in, I can't confirm that it isn't) be noticeable when riding the bike in a slalom course or when "pumping" the bike very hard side to side when sprinting. Neither of these are activities that most people do very often, but it can happen. So, in this case, it's possible that somebody might be able to "feel" the heavier tires (but it wouldn't really slow you down much). Cars are different because in city driving, they are spending a lot of their time speeding up and slowing down. And when they try to reduce the weight, they are trying for much bigger percentages than 0.5%. Battle Mountain bicycles are not light bicycles. They are aerodynamic bicycles because if you want to be fast, you need to be aerodynamic. If you are racing a bicycle, then these effects can matter. A 0.5% weight effect may not be noticeable by the rider, but it can make a few seconds difference over 100 miles. If you are a professional racer, then I agree it makes sense to worry about these effects (although, again, rolling resistance is a much bigger issue). Finally, I agree that there is a wide-spread belief in bicycling that wheel weight is important. And, except for racers, it's basically wrong. It's as important as it is, it's very quantifiable, and if weight is an issue, most of us should eat a bit less instead of worrying about the weight of the tires on our bikes. For almost all commuters, having a tire that was heavier, but had lower rolling resistance and better flat protection would almost always be a welcome change. Cheers, Charles Certainly tire weight doesn't happen in a vacuum, and other factors like tire construction, rubber compound, tread pattern, carcass size, and rolling resistance are all part of the tire performance/human performance interface. Usually, heavier tires face other penalties than just weight. Ultimately, I believe that it behooves any cyclist who thinks about their effort and performance to run as light tires as possible (by which I mean, the lightest tire that meets all their demands, such as desired tread pattern, flat resistance level, price, etc.). |
Only when accelerating does the wheel weight matter
but you will get some of that back on your glide Once you are up to speed-only the rolling resistance matters |
| All times are GMT -6. The time now is 02:31 AM. |
Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.