[Wimbo]

Does anyone know (and can explain) the impact of relatively small bike weight changes on the overall ride experience? For example, if my bike with pedals weighs 19.8 pounds, and I make a change to it that drops the weight to 18 pounds, what is the measurable difference to the ride experience? Is it the same as if I lost 1.8 pounds of body weight, or is there some sort of impact to another consideration other than total rider + bike weight (center of gravity, rotational friction, etc). If I weight 200 pounds, then the total rider + bike weight in the example above would be 219.8 pounds vs 218 pounds.

I ask because it seems that there is a lot of fretting about a half pound (approx 227g) weight difference in bikes/components. I think I'm just too stupid or too inexperienced to understand the "true" benefit of shaving off bike weight.

Thanks. Sorry if this is a stupid question.

 

[spade2you]

Not much when you're talking a lot of overall weight.

 

[Hooben]

Real differences are felt with a rider that is in great shape and in a race situation. The lighter bike willl gain a second or two on another rider, all other things being equal. With club cyclists, it's just bragging rights.

 

[laffeaux]

Ride quality? No. No change.

Speed? A small amount. The weight weenie guys can give you real numbers, but a pound is worth a few seconds on a really long steep climb. To pro riders that win or lose races by a few 1/10s of a second it's worth the savings. If you're trying to keep up with a buddy on a climb it makes very very little difference.

 

[InfiniteLoop]

I just went from 20 to 15. Major difference in climbing and accelerating. On 25 - 40 mile rides I've gained about 0.4 mph average. For this old guy it's the diff between getting dropped and staying with the group till the finish.

 

[AndrwSwitch]

It depends where the weight is. If you're drastically changing the attitude of the bicycle (like diving in and out of corners, or swinging the frame in a sprint or out-of-the-saddle climb) you'll feel the weight difference if it's up high. Things higher on the frame acquire more momentum, so it takes more force to stop them at the end of each swing, or when you've already leaned as much into your turn as you want to or righted the bike. I think that changes in weight at the rim make a similar difference, because the wheels act as gyroscopes. Changes in weight near the hubs or bottom bracket, or spread throughout the frame, will be almost imperceptible. So (IMHO, of course) it's really not worth stressing about the drivetrain, handlebars, stem, hubs, etc. I'll buy it that going to a much light saddle or seat post might make a little more difference, but it would have to be a lot lighter - like 200g, at least.

I think I can feel the difference between having my seat wedge and not having it on my mountain bike. It contains two MTB tubes, so it's probably about a pound. I can't feel the difference on my road bike, with two smaller tubes and a lot less exposed seat post over the frame. Without glancing down at my water bottles, there's no way I could tell whether or not I have them.

My heavy-ass lock on my commuter changes the handling quite a lot when it's on the rear rack, but that's more weight than you're talking about, and in about the worst possible place.

 

[padawan716]

You feel the difference but it doesn't make you faster.

 

[Argentius]

This is not because of the bike weight change, fwiw.

Here's a calculator that looks decent, though I have not checked the formulae:

http://www.noping.net/english/

For a 175 lb rider, on a 20 lb bike, to go 18mph on level ground, requires 146 watts.

If I reduce the bike weight by 5 lbs, the calculator says this requires 145 watts. If I keep it at 146 watts and change the weight to calculate for speed, the difference does not register at one significant digit.

Even up a 5% grade, at 200 watts, the change is 0.2 mph -- and, of course, much of that difference would be wiped out on the descent.

I just went from 20 to 15. Major difference in climbing and accelerating. On 25 - 40 mile rides I've gained about 0.4 mph average. For this old guy it's the diff between getting dropped and staying with the group till the finish.

 

[PdxMark]

Even up a 5% grade, at 200 watts, the change is 0.2 mph -- and, of course, much of that difference would be wiped out on the descent.

Agreed. The combined weight of rider and bike are what determine the effort required for all "accelerations," which includes increasing speed from stops or slower paces and going uphill. For a 180 pound rider and a 20 pound bike that total weight is 200 pounds. A 1 pound difference is 0.5%, which correlates to the decrease in speed for a fixed amount of effort or the required increase in effort for a given speed. For recreational riders this is negligble. For racers, in which race time differences are often well below 0.5%, it's a big deal.

 

[Argentius]

Accelerations

You're telling me.

I rode a little local race on my 27-lb commuter. There was a semi-paved little climb. Other guys rode their 15-lb race bikes. I got killed going with the attacks.

Agreed. The combined weight of rider and bike are what determine the effort required for all "accelerations," which includes increasing speed from stops or slower paces and going uphill. For a 180 pound rider and a 20 pound bike that total weight is 200 pounds. A 1 pound difference is 0.5%, which correlates to the decrease in speed for a fixed amount of effort or the required increase in effort for a given speed. For recreational riders this is negligble. For racers, in which race time differences are often well below 0.5%, it's a big deal.

 

[ptfmb71]

I would say for the normal Joe Schmo anything under 5lbs does not make any bit of a difference on normal rides. I think it's moslty mental

 

[Cableguy]

much of that difference would be wiped out on the descent

Well, weight matters most when going up the steep stuff, where drafting is a lot less useful as you're going sub 15 mph. On the descent, you can draft like there's no tomorrow - if you're behind someone going down, pedaling is often not even necessary. And if you get to the top 0.2 to 0.5mph faster becase your bike is 5 pounds lighter, you have a greater chance of having that group to go down with. This is why in the TDF if you're not one of the best climbers in the group you simply can't win. So if you're riding competitively those 5 pounds are significant for the climbs.

That said, those 5 pounds will do hardly anything at all for you on relatively flat ground (sub 2%) and if you're not seriously into the competitive side of the sport (i.e. racing or logging times), you won't notice any difference save for the placebo effect on the first 2 or 3 rides when you try harder to prove to yourself shelling out a crap load of money was worth it

 

[InfiniteLoop]

This is not because of the bike weight change, fwiw...

It could certainly be a psychological boost, or smoother drivetrain, or maybe even a change in position. However... There are 2 courses that I ride twice each week and have pretty good performance data for. I've now done each 6 or 7 times with my new bike. On average I'm 0.4 mph faster with no significant change in heart rate than previous rides.

 

[PdxMark]

It could certainly be a psychological boost, or smoother drivetrain, or maybe even a change in position. However... There are 2 courses that I ride twice each week and have pretty good performance data for. I've now done each 6 or 7 times with my new bike. On average I'm 0.4 mph faster with no significant change in heart rate than previous rides.

Is there a change in body position? Components? I think there are factors that can affect speed but aren't weight-based. Components, allowing easier, more frequent shifting can get you into the most efficient gear more easily. Increased aerodynamics of wheels can matter. Body position can affect your aerodynamics, even including handlebar width, and can also affect your power output on the bike.

 

[Richard]

Road goes up. Weight matters. But let's keep it in perspective. It's the bicycle plus the rider.

On the flats, "aero" is more important. Pro cyclists will be seen on a deeper dish, heavier wheelset on the flat stages.

As I tell my customers, if you can afford an 18lb bike, you're "golden." That's where the "bang for the buck" is. Lighter than that, it's "more dollars spent for fewer grams lost."

The stongest climber in my club is the guy (I hate him) who rides a mid-'80's steel Schwinn converted to an SS with 52x15 gearing. Go figure!!

 

[Kerry Irons]

Physics vs. perceptions

It could certainly be a psychological boost, or smoother drivetrain, or maybe even a change in position. However... There are 2 courses that I ride twice each week and have pretty good performance data for. I've now done each 6 or 7 times with my new bike. On average I'm 0.4 mph faster with no significant change in heart rate than previous rides.

As others have already noted, the physics of your situation does not allow your claim. That kind of weight savings (weight only, no other change) simply will not give you that kind of speed increase. You can prove this to yourself by getting something like lead shot and filling one of your water bottles so your bike weight is back to 20 lbs. You will not slow down by that 0.4 mph. We can fairly presume that the drop in bike weight from 20 to 15 lb. involved a totally new bike, new wheels, new tires, etc. PERHAPS when you combine all that stuff you could get 0.4 mph, but even that is a stretch unless you had a change in body position that really improved your aerodynamics..