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  1. #1
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    Bike weight question

    I currently have a 2018 Trek Fuel EX8 size XXL and it weighs 34 pounds. I am looking to upgrade in the near future and have a question for you knowledgeable people in reference to bike weight. I live in an area which requires a bit of climbing, some technical, to get to the descent. I know less weight will make it somewhat easier to climb but what about the weight of the bike when descending. Theoretically, if my same bike weighed 28 pounds, would it be as stable descending as the 34 pound bike? My thought was the heavier bike would be more stable in the rough stuff due to the extra weight.

    I hope this is not a stupid question, I was just curious. Thank you for any input you can give me.

  2. #2
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    Most likely that extra weight increases durability, not stability.

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    There is a tread on bike weight, and how affects stability on the ebike forum.

  4. #4
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    Quote Originally Posted by 5-0 View Post
    I currently have a 2018 Trek Fuel EX8 size XXL and it weighs 34 pounds. I am looking to upgrade in the near future and have a question for you knowledgeable people in reference to bike weight. I live in an area which requires a bit of climbing, some technical, to get to the descent. I know less weight will make it somewhat easier to climb but what about the weight of the bike when descending. Theoretically, if my same bike weighed 28 pounds, would it be as stable descending as the 34 pound bike? My thought was the heavier bike would be more stable in the rough stuff due to the extra weight.

    I hope this is not a stupid question, I was just curious. Thank you for any input you can give me.
    Itís actually a very good question, but unfortunately itís kind of hard to answer. My simple response is ďit depends.Ē

    I think the law of diminishing returns applies to going lighter and lighter with a bike you intent to rally pretty hard on the downs. Going from 34 pounds to 28 pounds is a pretty significant difference.

    The first thing youíll notice is that the amount of ďmanhandlingĒ you normally do will be way too much on the lighter bike, and it will seem kinda unstable and out of control at first. Youíll get more air on jumps (which may be a bad thing if you normally hit them just right), and you may enter corners faster than youíre accustomed to. This is very bad if the new brakes arenít up to par.

    I think 28 pounds is pretty damned light for something Iíd want to descend aggressively on, but Iím 190 pounds. If itís a strong frame with enough carbon and high end non-structural parts to get the weight there, itís probably as light as Iíd go. If itís that light because of the wheels and frame, at my weight Iíd worry a bit.

    I can tell you one thing, my enduro bike handles amazingly well on gnarly terrain, but itís older and heavy (~36 pounds), and itís too heavy to be competitive in enduro races, because the flatter sections suck away my speed and energy way too much. 34 pounds is still a bit heavy as well, I think. For me, the magic weight seems to be around 30-32 pounds.

    I bought a Kona Honzo this year thatís a hardtail with pretty modern, aggressive geometry, and Iíve beaten many of my old DH prs from the other bike, and have gotten some Strava KOMs on it. It probably weighs around 30 pounds with Maxxis Minion front/Aggressor rear. If only my other bike was that light...

  5. #5
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    Geo can make for stability going down more so than weight, imo.

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    Yeah, having more sprung mass will increase stability. That doesn't mean more mass is a good thing. It would be better if you could get the same level of stability through better geo and suspension than adding mass. Adding mass means it takes more energy to climb, turn, and jump.

  7. #7
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    Lighter is better to a point. Also you are on an XXL, which is heavier than say a medium to begin with.

  8. #8
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    Quote Originally Posted by eb1888 View Post
    Geo can make for stability going down more so than weight, imo.
    This is one ingredient and the major player, bike fit to rider... After this we can look at riding style and skill.
    Get fAt, Stay fAt, Ride fAt
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    Quote Originally Posted by 5-0 View Post
    if my same bike weighed 28 pounds, would it be as stable descending as the 34 pound bike? .

    .
    More stable.

    The suspension will be able to work easier/better, but not much.

    I live at the top of a steep downhill section that is rocky and loose gravel river rock, when bombing it you can easily get to 40-50mph. [bottom of stagecoach in auburn]

    im 200lbs and my bike 27 ish, the quality of forks makes a good difference more then weight of the bike.

    I think your bike had the performance series which is a great front shock, but the factory ups how stable you feel when moving out. 34 grip2 cartridge may fit, it does on the factory and that would really up your game.

    As far as climbing the weight is huge, there is a huge difference on my 22lb HT verses the 27lb FS. I usually can go up a gear lower on the HT and it has a 32t verses the 30t on the FS.

    surprised your bike is so heavy, my riding buddy has a 18 trek fuel L and its also 27.5 lbs

  10. #10
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    Quote Originally Posted by Outhouse View Post

    surprised your bike is so heavy, my riding buddy has a 18 trek fuel L and its also 27.5 lbs

    Surprised your buddies bike is so light, Trek's top of the line Fuel EX 9.9 weighs more than that and it costs $9,000. Their lightest aluminum model is over 30# in sz medium.
    I brake for stinkbugs

  11. #11
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    In the rough, the geometry and the quality of the suspension will make way more difference than weight. If all else is equal, I can't thing of any situation where a heavier bike is more desirable. Fit trumps all.
    Well my days of not taking you seriously are certainly coming to a middle.

  12. #12
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    First off thank you all for your input I greatly appreciate it. I am about to retire and am going to pull the trigger on a bike which will be a little easier on the climb but I don't want to sacrifice stability on the downs. I have a found a bike which has similar travel and geo at the lower weight which is why I posed the question. I also didn't ask about a particular bike because I didn't want to devolve into a which bike I should get. Again, thank you for your input!!

  13. #13
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    Just to throw some more fuel on this fire, rotational weight matters substantially more than static weight IMO. Losing 1lb on the wheels will change the feel more than 5lbs on the bike IMO.
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  14. #14
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    Too many unknowns to formulate a reply: wheel base length, frame geometry, suspension technology, wheel weight--specifically rolling resistance, desired type of tire, gearing...

    If the question is: What is an upgrade to my current bike that will decrease weight and improve performance? My answer would be wheels. Less weight means less rolling resistance = better climbing. At the same time, improved/updated bearing in the new hubs assist with coasting/downhilling.

  15. #15
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    Quote Originally Posted by J.B. Weld View Post
    Surprised your buddies bike is so light, Trek's top of the line Fuel EX 9.9 weighs more than that and it costs $9,000. Their lightest aluminum model is over 30# in sz medium.
    I know he had enve cf rims set up as tubeless, but the rest is stock. weighs identical to my bike. I know his frame is cf as well. I dont know trek models but i know its an 18 and a 9.8. [ my eyes suck, i swear i thought it was same bike as OP, now I read his is an 8 not a 9.8 like my buddy] my bad

  16. #16
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    The exact same bike, but with 5-7 less pounds on it should be more agile in any corners, especially DH corners. Add to that the gyroscopic effect of of heavier wheels vs lighter wheels.

  17. #17
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    Quote Originally Posted by Outhouse View Post
    I know he had enve cf rims set up as tubeless, but the rest is stock. weighs identical to my bike. I know his frame is cf as well. I dont know trek models but i know its an 18 and a 9.8. [ my eyes suck, i swear i thought it was same bike as OP, now I read his is an 8 not a 9.8 like my buddy] my bad



    Well your buddy has a ~$7,000 bike, that's about what it takes to get down to that weight range for that type of bike.

    Still that's pretty good though, trek lists that bike @29# for a sz. med with the stock carbon rims.
    I brake for stinkbugs

  18. #18
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    If you roll a bowling ball down a particular trail, and then roll a golf ball down the same trail, physics says the bowling ball will have more of a straight-line path than the golf ball. The heavier ball will track straighter then the lighter ball, more inertia and less "ping-ponging".

    So there is something to weight in that regard, but in the case of a mountain bike, and only 5-6 pounds difference, I think all the other variables will come into play way before the overall weight does.
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  19. #19
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    Quote Originally Posted by J.B. Weld View Post

    Still that's pretty good though, trek lists that bike @29# for a sz. med with the stock carbon rims.
    For some reason his had alloy rims stock.

  20. #20
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    My '16 FEX 9 (al frame) is 28 with pedals. Gots CF wheels, bar and saddle. Tires are getting kinda worn so it may be lighter now? IDK how much balled up Stan's it has.
    What, me worry?

  21. #21
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    Count me in the 'always prefers the lightest bike that is still reliable and has ideal geo' group.

    There is the issue of unsprung weight as a ratio of total (sprung + unsprung) weight. If your chassis were really light, but your unsprung weight (wheels, etc.) was relatively heavy, the bike will feel less stable. Basically those heavier wheels have an easier time jostling the sprung weight all around.

    A bike would feel the most secure if the wheels/ tires/ brakes/ cassette were featherweight but with a heavier frame.

    But good geo is where it's at.

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