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Lighter bikes, and the illusion of speed...(17 posts)
|Lighter bikes, and the illusion of speed...||rwbadley|
May 23, 2002 9:36 PM
|We know that riding the bike with a weight of 17 lbs. will (all else being equal) give us a speed advantage over riding the bike that weighs 21 lbs.
I have been playing with an online program that tells me, on my favorite 8 mile grade of 5-7% I can improve my time to the top by a significant amount by shedding 4 lbs. (let's assume it is off the bike)
A knowledgeable gentleman told me after many old school studies, they determined that seven pounds (off the bike) translated to a gain of 1 mph average speed over distance.
I would like to hear some cold, hard anecdotes (!) about the group rides or races that you suddenly were able to kick a-- on with the purchase of your new, lighter (by 3-5 lbs) steed.
King of the hill?
World class sprints?
I am interested in how the loss of weight off the bike effected your position in the pack.
Or did it?
If your riding buddy just got the seventeen pounder, and you're still on the sled, but you noticed a difference in your ability to keep up(or drop him/her), I'd like to hear about that too!
|re: Lighter bikes, and the illusion of speed...||Carbon fiber fanatik|
May 24, 2002 1:58 AM
|Here is a "believe it or not" Mr. Ripley fact for you. I'm faster on my "boat anchor" than I was on my 17 pounder. I am not a pro, or an aeronautical engineer, but I found this out, staying aero to the wind is worth a whole lot more than a few measly pounds, when dealing with avg. speed over distance.|
May 24, 2002 3:21 AM
|drag is far more critical than weight when it comes to speed.
Except for heavy-grade climbing, lightness offers a de minimus of return.
|Isn't the average TT bike about 24 lbs???||Quack|
May 24, 2002 5:23 AM
|From my old records, my aluminum 23 lb. Schwinn was about 1 mph faster than my Carbon Trek on everything that didn't involve climbing. Would I rather race on the Schwinn, no way. I used to get dropped like a bad habit when the sprint began because I just couldn't get things moving. By combining the 5 lbs. the Trek saved me with the 15 lbs. that my ass saved me, I now only see a couple of rear wheels in the sprints instead of all of them.|
May 24, 2002 5:26 AM
|No way to generalize a speed gain from weight loss without knowing the terrain, total weight, power the rider makes (and probably a few other things). I assume you checked http://www.analyticcycling.com ? Those calculations assume certain conditions, which may or may not be true. Nonetheless, lighter weight will be faster up hill (and slower down), *all else equal*. That last part is important, but probably rarely true.
Aero matters more most of the time, and over all.
For descending, especially with lots of turns, I find that good handling and confidence matters more than weight or aeroness. This allows you to go fast and keep your speed up through the corners better. My C40 is much better at this than my Bianchi EV2.
It seems everyone tends to draw the magic line of what's reasonable for bike weight right around where theirs weighs. Anyone notice this?
|Is that true? Lighter is slower down hill?||Sintesi|
May 24, 2002 5:37 AM
|I thought everything falls at the same rate? Would two pounds off make a bike slower on the descent? Just curious, I made a point of staying out of physics class back in highschool. : )
May 24, 2002 5:41 AM
|We had a huge debate about this about a year ago.
Lighter is slower down a hill (again, all else equal). Yes. Why? Some people say "less weight," other point out that it is actually "less weight (mass) per unit of drag." Same thing up a hill, where it's "more power per unit mass" (power to weight ratio).
In a vacuum all things fall at the same rate. We don't bike in vacuums.
Analytic Cycling confirms this.
|Okay thanks. Let us never speak of this again. : ) nm||Sintesi|
May 24, 2002 6:14 AM
|F=MA Mass only matters when accelerating. When on an incline||tz|
May 24, 2002 5:38 AM
|[up or down] you are also accelerating. Except that besides you doing your pedaling, gravity is also pushing you down the slope - you have to counter that deceleration by applying more force to pedals. Every extra pound on you+bike increases the force with which gravity pulls you down, making climbs more difficult.
When the road is flat - your mass only affects the coefficient of friction between various bike parts, tires and asphalt [insignificantly]. Therefore, air resistance is your main enemy. This is the cause of our dislike for headwind, and our use of the "aero" equipment.
Also, never completely ignore the psychological factor. The great feel of you new, shiny road bike, fear of being labeled a "poser", or desire to keep up with experienced riders can make you go faster.
May 24, 2002 6:26 AM
|Of seven pounds on bike/1 mph over 'distance' came from studies by Schwinn and Co. This distance was defined as many miles with climbing, descents etc... I am believing this is part of the reason Schwinn built their bikes to be somewhat heavy, stiff and solid, as they discovered that frame rigidity had much to do with confidence and the ability to "go fast"
This applies to their performance bikes as well. The racing Paramounts, in their day, were not known for always being the lightest. They were in many cases built with heavier tubing than their euro counterparts.
This was not because Schwinn could not afford expensive lightweight tubing. Schwinn discovered that when the rider trusted his mount he was able to concentrate on the job at hand. This is also why they developed the frame geometry to a gnats a--. The handling character would allow the bike to dissappear underneath so we could get back to going fast.
I ride with groups a fair bit, and try to gather info on 'how I feel about the bike'
Most people that have sunk a large sum into a bike will 'Like It'.
I do find some interesting variation tho'. One guy that has bikes supplied (not sponsored)'Hated' his ride because at 17 lbs it was too heavy. I had to chuckle because for him ( as for myself, and maybe most of us) I deemed the bike to definitely not be the limiting factor.
Another, on a lightweight felt it was a "nasty noodle" no confidence, no support no fun.
These were notable exceptions to the usual love it replies.
I am NOT saying the only "best bike" would be the behemoth. I do think 'sometimes' especially by the rec. and less than higher level racers, bike weight may be worshipped a bit more than needed. Especially when we know that wind resistance, confidence, and other factors can effect us more than the bike weight.
All that being said, and I agree with all previous posts,
Where is the story of instant speed I was hoping to find?????
May 24, 2002 6:33 AM
|At the 508 race last year, I rode a C40 with aerobars most of the route. It weight 17 something as ridden. I also had a "climbing bike," a Bianchi EV2 with every lightweight gizmo and trick in the book used, except for some superlow XTR gearing (which was still pretty light, with SRP bolts used). It weighed in the 13's.
Yes, I could instantly tell a difference climbing on the EV2. Accelleration and climbing were significantly faster. How much? I can't quantify. There was no doubt about it, though.
May 24, 2002 7:31 AM
|it seems to me the only people that get irritated talking about bike weight are the ones riding the boat anchors, probably because they can't afford anything else. Do I feel having the lightest bike will win me a race? not a chance. Is there an advantage of having a lighter bike, there is where I live, nothing but mountains. I do agree that aero is more important in most cases, but does this mean you dont care if your bike weighs 30 lbs. if it is Aero? If you agree that a 20 lb bike would perform better than a 30 lb bike, then why wouldn't a 17 lb bike perform better than a 20 lb bike? I think if you got the money, and want a light bike, more power to ya.|
May 24, 2002 8:08 AM
|S-U-B, See previous post on 'the generalization' as to why a 17 lb bike >may not< perform as well as a 20 lb bike.
Doug, Thanks for an answer. This is more the type of response I was hoping to get, as it confirms that for a person riding one bike there must be a 'best medium point' between lightness and ride character. The reason you might not ride the 13 lb bike over the course of the whole race is that it would be a handicap to do so, due to various design parameters. The same design that makes this bike such a good climber.
Any person with an extended background in our avocation 'knows' certain things about the sport.
I am aware of the science aspect of the sport.
I have a number of bikes, with the lightest being a chunky 18 lbs. I was hoping to draw out some interesting stories from the group!
|Speed (average) vs. acceleration||Tig|
May 24, 2002 9:10 AM
|I totally agree with the others on aerodynamics being a greater factor in speed, and weight being a factor while climbing. On a flat road group ride or race, aerodynamics doesn't mean much (except in a breakaway), but lighter weight wheels sure do if the pace constantly changes with attacks and sprints. Accelerating rotational mass is so much easier with a nice light wheel than a disk wheel or something else heavy. I know this is all quite fundamental for most, but I am mentioning it for newer riders who are interested.
All the lightweight goodies you can afford means nothing if they aren't durable. At 135 pounds, I can get away with some really lightweight rims and low spokes, but still try to keep it on the conservative side. Not having a big bike budget makes that easy!
|Speed (average) vs. acceleration||S-U-B|
May 24, 2002 11:46 AM
|rwbadly - I do agree at times a slightly heavier bike may actually be better than a lighter bike. I also agree that there is a point where the light weight actually takes away from it's performance rather than adding to it, due to lack of efficiency etc... I have a 16.5 lb KG 381 and an 18.5 lb GT ZR 2.0, I have no interest racing the KG in crits, The GT is great for that, but anything with hills, the KG is my choice. When it comes to the flats, i would go with either. It also makes no sense if your 30 lbs over weight,to worry about what your bike weighs. I think alot of the interest in weight is due to just having the latest and greatest, which I think is a part of this sport. If having a 14 lb bike makes you ride harder and farther, it's more than worth it.|
|Going the other way ...||Humma Hah|
May 24, 2002 4:37 PM
|... The bike I usually ride weighs around 41 pounds, as usually equipped for a long ride. I also generally ride with a backpack containing half a gallon of water and an assortment of tools and spares for working on that antique, typically about 10 pounds. That puts me about ... 33 pounds over a "typical" roadbike, which should work out to a 4 5/7 mph disadvantage.
And that's probably about right. I'll do 14-15 mph average on a long ride on relatively easy terrain with few stops. Some of that is lack of gearing, some is the fat tires, and a big part of it is semi-upright riding position. Adding 5 mph would put me up around 20 mph, then get rid of the extra drag and I'd probably be eaking into the lower end of roadrace speeds.
|Ah, the epiphany I was hoping for...||rwbadley|
May 24, 2002 8:39 PM
|I also have spent time on an assortment of rigs. The Bianchi commuting I do all up is in the area of 34+ with the extra.... If I am averaging 15-16mph with the apparent effort similar to a normal 18 or so mph on the lighter bike. It does in fact work out!! It makes sense to look in the direction of 'most differential'
By the way, we would find less wind resistance to effect our effort at 14 mph as well so it would be less factor than at the 18-20 or so.
Thanks Humma Hah for the eye opener