Weight? What is the big deal?

PB Forum :: Downhill
Weight? What is the big deal?
Author Message
flag oceen246
Posted: Jan 3, 2011 at 22:30 Quote
Reactions from trying tubeless are shocking. true story.

Unsecure image, only https images allowed: http://imagemacros.files.wordpress.com/2009/12/omg_it_spins.jpg?w=600&h=450
flag trobudden
Posted: Jan 4, 2011 at 15:33 Quote
just look at every sport or motorsport in history for your answer, from hockey sticks to formula one, less weight = advantage

the same applies to DH racing, but you never want to compromise wieght for strength due to the danger of a failure.
flag thereisnospoon
Posted: Jan 4, 2011 at 21:39 Quote
I absolutely agree that weight savings can make a noticeable difference, no doubt. but the vast majority of riders don't need a 35lb DH race bike to have fun noodling around at their local bike park. yet people on PB keep emphasizing that it's the only way to enjoy biking.

IMO, I think this obsession with saving weight in DH has become more about bike whoring the newest piece of expensive bling (ie hoping and praying for an extra fave or two), or keeping up with the neighbors/other PB posters, than it is about improving race times by a second or three, improving bike skills, or having more fun while riding.

it's getting to be a bit much, IMHO.
flag Nobble
Posted: Jan 4, 2011 at 22:05 Quote
my bike is also my race bike. But does that mean I shouldnt make it light because I ride on it everyday?

No, it dosent. THis thread lost all sense of reason long ago.
flag z-man
O+ FL
Posted: Jan 4, 2011 at 22:35 Quote
Nobble wrote:
my bike is also my race bike. But does that mean I shouldnt make it light because I ride on it everyday?

No, it dosent. THis thread lost all sense of reason long ago.
oh yes indeed
flag thereisnospoon
Posted: Jan 5, 2011 at 11:50 Quote
Nobble wrote:
my bike is also my race bike. But does that mean I shouldnt make it light because I ride on it everyday?

No, it dosent. THis thread lost all sense of reason long ago.

you missed my point entirely.
if you want to own a race bike, power to you. if you want to make it lighter to get faster and/or have more fun, power to you.
LOL, hell I have one too, and have even upgraded to lighter parts when something breaks....and I don't even "race"...Two-Face

my argument: the recent "blood lust" for weight savings has similarly lost all sense of reason. people on this forum seem to be dropping big money on lightweight gear more due to peer pressure, and need for acceptance, than to get faster or to have more fun riding Facepalm

I'm all about weight savings benefits (depending on cost I suppose), but this social bullshit pisses me off.

comprende now?
flag dh-pete
Posted: Jan 5, 2011 at 12:36 Quote
Quit hatin', ride your bike!

Me and my 31.5 pound bike are going to haul ass tomorrow and Imma get stoked. With my tires being 38g lighter each since cutting.

*Trollface*
flag z-man
O+ FL
Posted: Jan 5, 2011 at 20:09 Quote
dh-pete wrote:
Quit hatin', ride your bike!

Me and my 31.5 pound bike are going to haul ass tomorrow and Imma get stoked. With my tires being 38g lighter each since cutting.

*Trollface*

thats the attitude!!!
flag goonrider
Posted: Jan 5, 2011 at 20:13 Quote
cutting all the tread off your rear tire makes you faster..
flag thereisnospoon
Posted: Jan 5, 2011 at 20:17 Quote
dh-pete wrote:
Quit hatin', ride your bike!

Me and my 31.5 pound bike are going to haul ass tomorrow and Imma get stoked. With my tires being 38g lighter each since cutting.

*Trollface*

31.5lbs? pssht, based on that weight number alone, your bike must not be very good. impossible to have fun on being so heavy.
I suggest removing the grips. or replacing the shock with a solid piece of titanium. be sure to write "straitline" on the Ti bar with an expensive marker.
ZOMG faaaassssst!!!

Razz
jk of course. haha
flag z-man
O+ FL
Posted: Jan 5, 2011 at 20:17 Quote
corsair712 wrote:
cutting all the tread off your rear tire makes you faster..

in certain cases yes, that is true. Running a front tire in the rear also seems to help with rolling resistance and corners better. Just doesnt stop as well, but who cares, you dont need to go as slow on corners, they rail!
flag oceen246
Posted: Jan 6, 2011 at 15:51 Quote
z-man wrote:
corsair712 wrote:
cutting all the tread off your rear tire makes you faster..

in certain cases yes, that is true. Running a front tire in the rear also seems to help with rolling resistance and corners better. Just doesnt stop as well, but who cares, you dont need to go as slow on corners, they rail!

I personally hate the dhr and i run dhf both front and rear. I sometimes ride with a bald rear tire (still have the side nobs) and the bike is screaming fast but is sketchy if i don't lean on turns. I'm currently "eyeing" those Geax tires that look like dhf. The dhf are nice but the side nobs get shredded of after a couple of rides so i can't justify the cost anymore.
flag goonrider
Posted: Jan 6, 2011 at 16:58 Quote
e.g peatys world champs tire..Unsecure image, only https images allowed: http://cdn.mos.bikeradar.com/images/news/2009/12/22/1261478324243-x5ewe0edqtsv-950-75.jpg
flag MooMoo2323
O+
Posted: Jan 9, 2011 at 7:50 Quote
z-man wrote:
Reading this quote here, makes me have some serious doubt on your knowledge on the laws of physics. This and various other things that you have stated have totally invalidated you're argument of weight not being a big deal

bigquotesheavier stone fall faster?

Weight doesn't have an effect on the speed that anything falls. Just resistance and the force of gravity. Its all about resistance to weight ratio. If you crumple up a piece of paper into a tight ball, it will fall at the same speed as a 14lb bowling ball. Weight does however have an effect on momentum, which on a bike, is a hindrance around corners and against the forces on your suspension.

Let me discuss the fallacies in both statements here. This is a matter of mechanical physics and it's clear that BOTH of you do not understand. First, it must be known that there is a difference between static objects and objects in motion. In reference to the "heavier stone falling faster", it just depends on stone's state when the question was asked: was the stone in motion or sitting in place? Your correction of his statement makes no sense. I think what you were trying to say is: objects, regardless of size or mass, fall at the same RATE (this is different than speed), in the absence of air resistance, and assuming the objects start their fall from zero velocity. Then you went on to mention momentum, which implies the "stone" (or our bikes) are in motion. This changes everything!

Everything in DH relates to momentum. It's all about "carrying your speed" (I'm sure you all use that phrase when looking at different lines/corners). When you include momentum into our physics discussion, things behave differently as our "stone" (our bikes) are not falling from zero, but have already had FORCE applied to them. Let us consider these scenarios:

For this example, let's assume 2 bikes of different weights enter a rock garden at the same speed. The equation for momentum is p=mv (p is momentum, m is mass, and v is velocity). Since "v" is the same for both bikes, the bike with the greater mass will have the greater momentum. Now, each bike will hit the same rock. This rock pushes the bikes in the opposite direction they want to travel. The bike with the greater inertia and momentum (the heavier bike) will be LESS AFFECTED than the lighter bike and continue down the hill at a faster speed. This means, the heavier bike can go through the rock garden while keeping a higher speed due to it's greater momentum. So here, the heavy bike wins.

Now, these same 2 bikes are exiting a corner and have to pedal to get back up to speed. We'll need the basic equation: F=ma (f is force, m is mass, and a is acceleration). Based on this relationship, in order for the heavier bike to accelerate at the same rate as the lighter bike, MORE force is required (assuming they exited the corner at the same speed). Even though the heavy bike still has more momentum when leaving the corner, the rider still has to work harder to get the bike to go faster.

Also, please note that my examples above assume the weight differences are in the same spot on the bike. It seems everyone is aware of the benefits of rotational weight savings over static weight savings. And this also assumes the riders are the same weight. The question of the thread was referring to whether or not one would notice a 1-2lbs. weight difference on his bike. So, whether or not the rider is fat has no affect on the answer to the question. Finally, my examples also assume the bikes have the same tires and tire pressure as well as suspension set up.

So, who wins? I'd say it depends on what terrain you're riding and what type of rider you are. Take a look at some of the WC riders out there and see what their bikes weigh. They range from under 35lbs to 42lbs+ (and there's no correlation between lighter bikes and podiums). Each type of bike has it's own advantages and disadvantages, and it's up to the rider to capitalize on which of those he chooses. For the type of rider I am and the trails down here in Southern California, a light bike seems do the trick for me. And yes, I can notice a 1 or 2 pound difference on my bike.

Hope this helped!

 


Copyright © 2000 - 2024. Pinkbike.com. All rights reserved.
dv42 0.031124
Mobile Version of Website