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  1. #1
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    bike weight, rider weight and speed: whats the real deal?

    Ok, OBVIOUSLY the lighter the bike (or any vehicle, for that matter), the easier to accelerate, and the less power it requires to maintain velocity.

    Also, the lighter the rider (and assuming equal power capacity) the quicker acceleration and higher top speed capacity.

    But we are "clydes." How much does bike weight matter in relation to body weight? I, for instance, weigh 300#, with tree trunks for legs. How much difference woul I really notice between a 30lb bike vs. a 22lb bike?

    I know that rotational mass, specifically rims and tires, is the ideal place to cut weight, but are the extra couple of pounds of frame and components all that improtant, especially with people our size?

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    Great Question, I've been wondering the same thing.

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    Not exactly...

    Yes lighter means less effort to get up to speed and to get up hills, but once you are at speed (on the flats) weight has virtually no effect... think of a freight train - once it gets moving (very sluggish and requires obscene amount of power) it will roll on its own for a long long way until you hit the brakes or come to a hill.

    Same goes for rotating weight - more weight means more effort to start up, but has virtually no effect on cruising speed on the flats.

    I wonder for medium-big folks such as yourself (I am a puny 260 lbs) how much extra drag will come from overstressed bearings and flattened out tires - my guess would be not too much, because I do fast group rides on my road bike with a bunch of 'people' under 200 lbs (and a few of those under 160 lbs) and I can keep up easily until we hit a long hill.

    If you are riding a road or hybrid bike, make sure that you have slightly wider tires (many people run 23mm wide tires, clydes should probably have 28 or 32 for the road), and that they are pumped up to their maximum pressure (hopefully 85 lbs or more, over 100psi is best),
    and that when you are slecting new wheels or a new bike that you make sure the hubs are good quality, and that you maintain them diligently with fresh grease and new bearings when necessary.

    To answer your question, most people won't notice too much difference between a 22 lb bike and a 30 lb bike, if the only difference between the bikes is the weight. Often, however, the bikes with higher quality tires and bearings tend to be the lighter ones, and this could mean more of a difference than overall bike weight. However, if you are planning some long mountain rides with thousands of feet of climbing, you will likely appreciate a bike that is 8 lbs lighter.

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    Quote Originally Posted by LarDasse74 View Post
    Not exactly...

    Yes lighter means less effort to get up to speed and to get up hills, but once you are at speed (on the flats) weight has virtually no effect... think of a freight train - once it gets moving (very sluggish and requires obscene amount of power) it will roll on its own for a long long way until you hit the brakes or come to a hill.

    Same goes for rotating weight - more weight means more effort to start up, but has virtually no effect on cruising speed on the flats.

    I wonder for medium-big folks such as yourself (I am a puny 260 lbs) how much extra drag will come from overstressed bearings and flattened out tires - my guess would be not too much, because I do fast group rides on my road bike with a bunch of 'people' under 200 lbs (and a few of those under 160 lbs) and I can keep up easily until we hit a long hill.

    If you are riding a road or hybrid bike, make sure that you have slightly wider tires (many people run 23mm wide tires, clydes should probably have 28 or 32 for the road), and that they are pumped up to their maximum pressure (hopefully 85 lbs or more, over 100psi is best),
    and that when you are slecting new wheels or a new bike that you make sure the hubs are good quality, and that you maintain them diligently with fresh grease and new bearings when necessary.

    To answer your question, most people won't notice too much difference between a 22 lb bike and a 30 lb bike, if the only difference between the bikes is the weight. Often, however, the bikes with higher quality tires and bearings tend to be the lighter ones, and this could mean more of a difference than overall bike weight. However, if you are planning some long mountain rides with thousands of feet of climbing, you will likely appreciate a bike that is 8 lbs lighter.

    Good post!

    I do, however, disagree on one point. Weight DOES matter for maintaining velocity, as weight increases friction.

    Fr = μN

    Force of friction is equal to the coefficient of friction multiplied by the force pushing the two bodies together. In this case the force is gravity, the force of gravity being F=ma, with a=9.8m/s as a constant, so the mass is what dictates the amount of force.

    With that said, that is going to be a bigger issue with rider weight than bike weight, imo.

  5. #5
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    Quote Originally Posted by ochizon View Post
    Good post!

    I do, however, disagree on one point. Weight DOES matter for maintaining velocity, as weight increases friction.

    Fr = μN

    Force of friction is equal to the coefficient of friction multiplied by the force pushing the two bodies together. In this case the force is gravity, the force of gravity being F=ma, with a=9.8m/s as a constant, so the mass is what dictates the amount of force.

    With that said, that is going to be a bigger issue with rider weight than bike weight, imo.
    I disagree... the friction you are calculating is the friction between the tire and the road keeping the tire from sliding... not keeping the tire from rolling. I agree extra weight will make it harder to drag the tire, but not to roll it. If that equation was correct then a 200 lb person would have to work twice as hard as a 100 lb person to keep a bike moving (neglecting air resistance), but this is not the case.

  6. #6
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    Quote Originally Posted by LarDasse74 View Post
    ...If you are riding a road or hybrid bike, make sure that you have slightly wider tires (many people run 23mm wide tires, clydes should probably have 28 or 32 for the road), and that they are pumped up to their maximum pressure (hopefully 85 lbs or more, over 100psi is best)...
    With all due respect, I'd be VERY cautious about this particular advice. Rims are manufactured with an expectation of a specific range of tire sizes. What you're advocating may exceed all safety parameters. A 32mm wide tire may be far beyond the rim's design. Having exceeded the design, you then advocate maximum tire pressure (exerting even more pressure on the already overstressed rim). And since this is the Clyde forum, we then put a heavier than normal rider on the combination of too wide a tire and too high a pressure.

    The results can be disastrous. I speak from experience. I had a Mavic rim fail on me from the exact combination of factors mentioned above. Fortunately, I wasn't badly injured or killed, but I still have neurological damage from that incident.

    Cyclocross racers can get away with wide tires on road rims because their tire pressures are less and the riders weigh less. Clydes (and particularly those running high tire pressures) should beware. Check with the rim manufacturer about the appropriate range of tire sizes for the specific rim. If the proposed tire width is within the manufacturer's specs, then maximum-rated pressure (listed on the tire sidewall) is probably OK.

  7. #7
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    Quote Originally Posted by LarDasse74 View Post
    I disagree... the friction you are calculating is the friction between the tire and the road keeping the tire from sliding... not keeping the tire from rolling. I agree extra weight will make it harder to drag the tire, but not to roll it. If that equation was correct then a 200 lb person would have to work twice as hard as a 100 lb person to keep a bike moving (neglecting air resistance), but this is not the case.
    This is correct if you think about it not at the point that the tire meets the road, since you want this to be 'sticky', but rather at the hub, where the rotation is effected through the bearings. In this case, the direction of force is down, the force is gravity, and the COF would be whatever that is for the steel bearings and grease-I don't know this off hand

    This is the dichotomy of the wheel! you want to maximize the effect of the coefficient of static friction at the perimeter, where the 'rubber meets the road', and minimize the effect of the coefficient of sliding friction at the hub.

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    Very good point. THank you.

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    Quote Originally Posted by 77midget View Post
    This is correct if you think about it not at the point that the tire meets the road, since you want this to be 'sticky', but rather at the hub, where the rotation is effected through the bearings. In this case, the direction of force is down, the force is gravity, and the COF would be whatever that is for the steel bearings and grease-I don't know this off hand

    This is the dichotomy of the wheel! you want to maximize the effect of the coefficient of static friction at the perimeter, where the 'rubber meets the road', and minimize the effect of the coefficient of sliding friction at the hub.
    Actually, the friction in rolling element bearings like in bicycle wheels does not work on the same F = uN equation - it has to do with the type of lubrication, the size of the balls, the number of balls, the hardness of the materials, etc... The balls are still rolling inside the hub, just like the wheel. The friction in a rolling element bearing will increase with greater rider weight, just not anywhere near a linear "2 X weight = 2 X friction" relationship. If the force on the bearing (from heavy rider/bike combo or from poor assembly or materials) is beyond the capacity of the bearing then the bearing will have a lot more friction while it is getting chewed into oblivion.

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    Frankly, I don't think many need to worry about actual bike weight. More important is the quality of the bearings and associated races in moving parts. High quality hubs and bottom bracket will make a noticeable difference. An even bigger difference will be gained by loosing body weight and improving the engine.

    In other words, replacing wheels to get good hubs will help. But not as much as improving yourself.

    I'm down 28 pounds now, from 205 (no longer a clyde, course, I'm only 5'7"). I'm on the same bike and components. I'm really noticing a difference from my fitness level and improved strength and endurance. The engine has improved a lot.
    -------

    Some sort of pithy irrelevant one-liner should go here.

  11. #11
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    Quote Originally Posted by LarDasse74 View Post
    I disagree... the friction you are calculating is the friction between the tire and the road keeping the tire from sliding... not keeping the tire from rolling. I agree extra weight will make it harder to drag the tire, but not to roll it. If that equation was correct then a 200 lb person would have to work twice as hard as a 100 lb person to keep a bike moving (neglecting air resistance), but this is not the case.

    You are correct. I am not too knowledgeable about physics.

    it still seems that a heavy load requires more work to maintain velocity. I mean, I know my pickup truck gets better mileage with an empty bed than with a heavy load on long trips.

    Am I missing something?

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    Quote Originally Posted by ochizon View Post
    You are correct. I am not too knowledgeable about physics.

    it still seems that a heavy load requires more work to maintain velocity. I mean, I know my pickup truck gets better mileage with an empty bed than with a heavy load on long trips.

    Am I missing something?
    Simple Newtonian physics...

    For each action, there is an equal and opposite reaction. Meaning if you are heavier it will require more force to get you going than if you were lighter. Likewise...

    An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Meaning it requires more "unbalanced force" to stop a heavier object than a lighter object. In a vacuum with no friction or other forces it would require more force to stop a 300lb moving object than a 150lb moving object. A heavier object has more inertia than a lighter object.

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    Ohh Physics! I can just see myself on my way home this afternoon doing calculations as I climb up a 8% grade for 1.5 miles in 87 deg heat.

    Yup that's what I'll be thinking about.
    Another great day in paradise

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    wikipedia has some interesting words on bike weight on performance:

    http://en.wikipedia.org/wiki/Bicycle...eight_vs_power

    "For instance, lowering a bike's weight by 1 lb, a major effort considering they may weigh less than 15 lb to start with, will have the same effect over a 40 km time trial as removing a protrusion into the air the size of a pencil."

    given that us clydes "protrude into the air" far more than a pencil, I'm saying bike weight doesn't have that much effect.

  15. #15
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    wow, great link!

    So getting my fat ass out of the wind is like cutting 10 bikes worth of weight!

    Would a hybrid with a drop bar look wierd? hahaha

  16. #16
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    FWIW: I currently ride a 17-lb road bike. My old beast tips the scales at probably 20+ lbs or more. When I took my lighter one into the shop for some work on it, I rode the older, heavier one. I noticed the difference in weight instantly. Felt like I was riding through sand all the time...just very sluggish.

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    Actually, a hybrid with drop bars is called "a touring bike"

    If you can find a touring bike that is comfortable for you, they are the best of all worlds (maybe not gnarly offroading, but just about everything else).

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    Quote Originally Posted by mkadam68 View Post
    FWIW: I currently ride a 17-lb road bike. My old beast tips the scales at probably 20+ lbs or more. When I took my lighter one into the shop for some work on it, I rode the older, heavier one. I noticed the difference in weight instantly. Felt like I was riding through sand all the time...just very sluggish.
    How much of that is the weight of the bike vs. the wheels/components?
    -------

    Some sort of pithy irrelevant one-liner should go here.

  19. #19
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    Quote Originally Posted by JoelS View Post
    How much of that is the weight of the bike vs. the wheels/components?
    And are all other things equal on the bikes, or is you 17lb bike a shiny new high quality bike and the 20 lb bike is older and lower quality (and possibly needing new tires, bearings, etc)?

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    Light bikes are nice. For me, I'm not going to worry about shopping for a bike that is ten pounds lighter when I can spend my energy making me sixty pounds lighter. I think that will do far more to increase my speed and make my rides feel easier. I'll just keep riding my 29# touring bike and smiling. I will comment on the point made about quality components. Even though my steel touring bike is pretty heavy, it has fairly nice components and it feels noticably easier to ride than some other bikes of similar weight with lots of wear or slightly less desirable parts.

  21. #21
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    "clydes should probably have 28 or 32 for the road), and that they are pumped up to their maximum pressure (hopefully 85 lbs or more, over 100psi is best)"


    I would definitely disagree with this. I started riding at 315+ and have always ridden 23 cm tires. I have never had any issues with them and usually run them at their near max of 120+ (depending on the tire). I can't imagine why I would need a wider tire for road use.

    I have seen this thinking posted elsewhere on this forum and am puzzled as to why people think Clydes have to roll on bikes built like tanks. I now weigh 240 and my legs are bigger than ever - even when I used to do powerlifting. So believe me when I say that I can put a hurtin' on a bike.

    As far as the speed/weight question goes, I think the only place that weight matters for Clydes is in hill climbing. Descending is awesome, flats don't matter, and the weight can even be a benefit when there are rollers. The only place I have gotten slower since riding (been on the same bike since I started 3 years ago - it weighs 19) is on the descents because I don't have as much weight pulling me down the hills. But saving a few pounds on the bike doesn't mean near as much as getting rid of the pounds around my waist!

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    We seem to be mostly forgetting the number one cause of bikes (and riders) not going faster - wind resistance.

    Drop bars, presenting less of a profile to the wind through weight loss - both will improve speed and efficiency, especially at higher bicycle speeds.

    It is not a linear relationship.

  23. #23
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    Quote Originally Posted by ochizon View Post
    Ok, OBVIOUSLY the lighter the bike (or any vehicle, for that matter), the easier to accelerate, and the less power it requires to maintain velocity.

    Also, the lighter the rider (and assuming equal power capacity) the quicker acceleration and higher top speed capacity.

    But we are "clydes." How much does bike weight matter in relation to body weight? I, for instance, weigh 300#, with tree trunks for legs. How much difference woul I really notice between a 30lb bike vs. a 22lb bike?

    I know that rotational mass, specifically rims and tires, is the ideal place to cut weight, but are the extra couple of pounds of frame and components all that improtant, especially with people our size?
    The biggest difference between a 30lb bike and a 22lb bike, is going to be the weight of your wallet, which will be considerably lighter with the 22lb bike.

    On flat ground, it's not going to make any difference, once your moving, going up hill, gravity doesn't differentiate between bike weight and "engine" weight. If your racing, then weight can mean a huge difference, providing all other factors are the same, especially when races are won and lost by .01 seconds. However if your not racing, then spending $1000 on a crank that is 3g lighter then a $100 crank, is darn right silly, no matter whether your 150lbs or 300lbs. When over 90% of the weight is in the engine, that is the obvious place to start cutting excess weight, it's also the cheapest.

    You also do realise that rotational mass is only an issue during the earliest phase of acceleration, and that it becomes much less important as speed increases.

    There are other factors though, rolling resistance, which can often be solved by wider or higher pressure tires (or both), wind resistance is also a major factor, it's the sail effect, the smaller your profile to the wind, the less wind resistance your going to see. Another factor, although a smaller one, is drive train efficiency, a stiff, dirty old chain, and hubs that haven't seen grease in years, is going to hurt efficiency more then an extra 1lb of bike weight, even rotational mass.

    Probably the biggest factor though is engine efficiency, how efficient is the engine in turning fuel into pedal motion, that is typically accomplished with a lot of miles, and a lot of training, which is a lot of hard work, but being able to kick the butt of a rider that is 50lbs lighter and 15 years younger, going up the side of heart attack ridge is priceless.

  24. #24
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    I have a 17 lb road bike and I have a 27 lb touring bike. I am significantly faster on the road bike than I am on the touring bike. I accelerate faster, I climb faster, and it is easier to maintain my speed on the flats. The only place that I have found the touring bike to be faster is on long and steep descents (this may be due to the additional weight but the touring bike has a longer wheel base as well as longer chain stays.)

    If it's speed I want, I take the 17 lb bicycle every time. If It's comfort, versatility, and carrying loads... the touring bike gets the call.

  25. #25
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    Quote Originally Posted by InTheRain View Post
    I have a 17 lb road bike and I have a 27 lb touring bike. I am significantly faster on the road bike than I am on the touring bike. I accelerate faster, I climb faster, and it is easier to maintain my speed on the flats. The only place that I have found the touring bike to be faster is on long and steep descents (this may be due to the additional weight but the touring bike has a longer wheel base as well as longer chain stays.)

    If it's speed I want, I take the 17 lb bicycle every time. If It's comfort, versatility, and carrying loads... the touring bike gets the call.
    Yes, but ITR, I think we're bucking conventional Clyde wisdom here...


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