Light DH bikes faster than heavy DH bikes?- Mtbr.com
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  1. #1
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    Light DH bikes faster than heavy DH bikes?

    Just curious for anybody who has a V10 carbon or equivalent DH bike in terms of weight. I was looking at the new SC V10 carbon and it is very light at around 36-37 lbs. It seems like the bike being that light will be very agile and flickable but would the stability get compromised by the lightness? When it gets rough and technical seems like the light DH bike will get jocked around a lot. I don't have a light DH bike so I don't know.

    Are the lighter bikes faster than heavier bikes?

  2. #2
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    Light bikes are more intended for a float-over-trail riding style whereas heavy bikes are more inclined for the plow-over-**** method. If you're at the level where you're floating over stuff then stability isn't compromised and is totally in your control.....
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    Like he said... If you ride smooth and float over stuff easily then a lighter bike will be suited well for you. If you ride less smooth and generally plow through things then a heavier bike (ie-heavier and more durable parts) is what might suit you better. Weight doesn't necesarily dictate stability whereas wheelbase, geometry, and center of gravity have a bit more of an effect.
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  4. #4
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    Ceteris Paribus, a lighter DH bike is always better (well, at least at today's weights, I dunno how I'd feel about a 10lb bike even if it was indestructible)

  5. #5
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    Quote Originally Posted by Gemini2k05
    Ceteris Paribus, a lighter DH bike is always better (well, at least at today's weights, I dunno how I'd feel about a 10lb bike even if it was indestructible)
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    Quote Originally Posted by Calles
    Economics major?
    good call

  7. #7
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    light bikes are great until you break them or parts. then you need heavier stuff. go as light as you can reasonably afford.

  8. #8
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    i would think it depends on the riders skills & strength
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  9. #9
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    My V10 is currently 37lbs and is faster than when it was 42lbs. I don't notice any negative traits and wish it was 2-4lbs lighter.
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  10. #10
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    Heavy DH bikes deflect less.
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  11. #11
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    Quote Originally Posted by blumarvel
    Heavy DH bikes deflect less.
    Agread...

    Your only as fast as the first broken part on the bike...So if it holds then you finish if it doesnt then you DNF. So style/weight go hand in hand and the lighter the bike the more possability for a DNF.
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  12. #12
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    Quote Originally Posted by blumarvel
    Heavy DH bikes deflect less.
    A lighter bike can be "caught" and brought back on line quicker. When my dirtbike deflects I have to let off and put a lot of effort into catching it. I barely notice when my DH bike deflects.
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  13. #13
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    Quote Originally Posted by blumarvel
    Heavy DH bikes deflect less.

    Disagree.

    I think suspension set up, handlebar width, frame, wheel and fork stiffness and geometry will have a much more realistic effect on deflection. Especially considering how much a person weighs relative to the bike.

    I don't think it's how light bikes are literally but how light they ride. I have a Banshee Scythe right now that weighs about 38lbs and I have friend who has an old glory that's pushing mid 40's. His bike was easier to "float". My lighter bike actually likes to plow more and holds a straight line better.

    5 pounds on a bike will make a huge difference but I don't think that's what makes a bike "skitterish".
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  14. #14
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    How much does your dirt bike weigh vs. a heavy DH bicycle?
    PoisonDogFart

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    Quote Originally Posted by Quarashi
    Disagree.

    I think suspension set up, handlebar width, frame, wheel and fork stiffness and geometry will have a much more realistic effect on deflection. Especially considering how much a person weighs relative to the bike.

    I don't think it's how light bikes are literally but how light they ride. I have a Banshee Scythe right now that weighs about 38lbs and I have friend who has an old glory that's pushing mid 40's. His bike was easier to "float". My lighter bike actually likes to plow more and holds a straight line better.

    5 pounds on a bike will make a huge difference but I don't think that's what makes a bike "skitterish".
    "For every action there's an equal and opposite reaction" But yes, I agree that suspension plays a huge factor. That only makes sense.
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  16. #16
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    Quote Originally Posted by blumarvel
    How much does your dirt bike weigh vs. a heavy DH bicycle?
    More. The point is that while extra weight resists deflecting, it also makes it harder to correct a deflection.

    On a heavier bike it's also harder to make a quick, last moment adjustment to dodge a rock so you'll get more impacts/deflection.

    If everyone had a chance to ride a 36lb DH bike that didn't have durability issues questions like this wouldn't be asked.
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  17. #17
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    agree with most allready said
    But its not how it reacts to terrain that is an effect...............

    A heavier bike has more potential energy when taken to the same spot up a hill, (basic physics, it took more energy to get the bike up there...it has more enrgy to release on the way down)

    A heavier bike CAN be an advantage as it less prone to slow down as it has more inertia, BUT is harder to accelerate if you let it slow down

    I tried a light bike 2 seasons ago (intense), it flexed so bad i never got to trust what it would do in the gnar (im only about 170 lbs, cant comment on my flowiness of lack of it)
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  18. #18
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    The whole industry is moving toward lighter DH bikes. So, there must be something to the lighter bikes that some of the pros are wanting. I don't have a full DH bike yet. I have a SS and 6.6. They weigh about 1.5 lbs apart. The SS is more stable at fast speeds through rough technical sections and the 6.6 is just more flickable and a better jumper, but gets deflected more in the rough technical.

    I would like to see chart of the top 20 DH pros and weights of their bikes.

    I guess a lot depends on the course. Some just more straight flat out bomb courses a heavier bike may be better and the tighter twisty courses a lighter bike may be the ticket. I would like to see someone racing a tank of bike like 50lbs.

  19. #19
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    Quote Originally Posted by aliikane
    The whole industry is moving toward lighter DH bikes. So, there must be something to the lighter bikes that some of the pros are wanting. I don't have a full DH bike yet. I have a SS and 6.6. They weigh about 1.5 lbs apart. The SS is more stable at fast speeds through rough technical sections and the 6.6 is just more flickable and a better jumper, but gets deflected more in the rough technical.

    I would like to see chart of the top 20 DH pros and weights of their bikes.

    I guess a lot depends on the course. Some just more straight flat out bomb courses a heavier bike may be better and the tighter twisty courses a lighter bike may be the ticket. I would like to see someone racing a tank of bike like 50lbs.
    There was a video a few months back showing weights of pros bikes.....worth a look.

  20. #20
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    Quote Originally Posted by CrustyOne
    agree with most allready said
    But its not how it reacts to terrain that is an effect...............

    A heavier bike has more potential energy when taken to the same spot up a hill, (basic physics, it took more energy to get the bike up there...it has more enrgy to release on the way down)

    A heavier bike CAN be an advantage as it less prone to slow down as it has more inertia, BUT is harder to accelerate if you let it slow down

    I tried a light bike 2 seasons ago (intense), it flexed so bad i never got to trust what it would do in the gnar (im only about 170 lbs, cant comment on my flowiness of lack of it)
    There is too much going on to toss it up to basic physics. At the end of the day it's the quality of the parts that make a bike carry through the rough well. Technology these days is quite amazing in that you actually can make a 36 pound DH bike without compromising strength and stiffness.

    Practically speaking from experience, the biggest factors in reducing defflection are:

    A stiff fork ( I love 20mm thru axles long time! ) - Most important IMO.

    Slack head angle

    Rear ward axle path

    Wide bars

    Stiff frame


    If you feel like a lighter frame is making the frame deflect then you can compensate by reducing the spring rate or changing the damping.

    I think an often used example for light bikes and being skitterish is the Session. I'm 90% sure that it's mostly the leverage curve that makes that bike so "bouncy". My Scythe has it's pivot in a almost the exact same spot and it feels polar opposite to the Trek.
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  21. #21
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    Quote Originally Posted by aliikane
    I would like to see a chart of the top 20 DH pros and the weights of their bikes.
    The mentioned video showed them all being 37-39lbs. However, top pros are limited in parts selection due to sponsorship. They don't have the freedom to buy the lightest, strong parts. Look at every top WC bike and there's a couple parts I'd swap to something lighter but equally performing.
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  22. #22
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    Hmm, not convinced, maybe they just possibly dont want a sub 37lb downhill bike, I know from personal experience that it wouldnt suit me

    One other thing I notice a lot is people on here often quote a bike weight that is pure BS.
    Like its some sort of competition to say your bike is < Xlbs

    Ho hum, think ill go ride my 40lb tank down a hill
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  23. #23
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    lighter bike faster accelaration, easier to move around just seems quiker...heavier bikes feel sluggish

    My opinion...you can build a 38 pound dh bike and it still hold up to a pounding
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  24. #24
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    A heavier dh bike will be faster if you drop both out of an airplane Higher terminal velocity.

  25. #25
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    Quote Originally Posted by Pwshadow
    A heavier dh bike will be faster if you drop both out of an airplane Higher terminal velocity.
    if we use two identicle bikes but one has a solid frame. cant discount drag.

  26. #26
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    Quote Originally Posted by b-kul
    if we use two identicle bikes but one has a solid frame. cant discount drag.
    Of course. In this senario a sleak aero-dynamic frame like a santa cruz v10 would definitely beat a demo 8. that bulky rear end would just cause too much drag.

  27. #27
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    Quote Originally Posted by Lelandjt
    The mentioned video showed them all being 37-39lbs. However, top pros are limited in parts selection due to sponsorship. They don't have the freedom to buy the lightest, strong parts. Look at every top WC bike and there's a couple parts I'd swap to something lighter but equally performing.
    I think most of those guys could go for a part or two off of their regular sponsors offerings if they really wanted to. I mean look at all the guys running blacked out Minions or High Rollers.

  28. #28
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    Quote Originally Posted by CrustyOne
    One other thing I notice a lot is people on here often quote a bike weight that is pure BS.
    True. A bet a lot of it is spreadsheet weight.

    I recently weighed my decently built 7x7 bike that I would think to about 36-37lbs. Turned out to 40. No idea why it's so heavy. I shouldn't have weighed it. It would have still weighed 36lbs if I didn't put on that scale.
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  29. #29
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    Quote Originally Posted by Pwshadow
    Of course. In this senario a sleak aero-dynamic frame like a santa cruz v10 would definitely beat a demo 8. that bulky rear end would just cause too much drag.
    if you drop anything out of an airplane at its cruising altitude drag plays a very signifigent role. physics 101 dude.

  30. #30
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    Quote Originally Posted by jcook1989
    I think most of those guys could go for a part or two off of their regular sponsors offerings if they really wanted to. I mean look at all the guys running blacked out Minions or High Rollers.
    They can get away with that cuz tires aren't as obvious. A Shimano sponsored rider can't get away with running Formula The Ones, even though they'd drop 1/2 a pound from his bike.
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  31. #31
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    Oh good grief
    DON'T TELL ME I'M STILL ON THAT FECKIN' ISLAND! ....

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