DH bike questions- Mtbr.com
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  1. #1
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    DH bike questions

    What makes a DH race bike different from a free ride bike, or an all mountain bike. Take for example my Reign x1, or an Intense 6.6. Or a Kona Stinky. How does having a higher and shorter stem/bar combo help while going downhill? Why do most bikes have more travel in the frame then in the fork? (or have I been converting MM forks to IN wrong, haha)

    Basically, what makes a DH bike an actual DH bike... not just a FR or AM?

    I know it seems kinda like a newbish question, and one that might have been answered before, but im trying to understand the technical differences. Im not trying to "define" DH like they try to do all the time in the AM forum

    Timm

  2. #2
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    Quote Originally Posted by mtnbkr123
    What makes a DH race bike different from a free ride bike, or an all mountain bike. Take for example my Reign x1, or an Intense 6.6. Or a Kona Stinky. How does having a higher and shorter stem/bar combo help while going downhill? Why do most bikes have more travel in the frame then in the fork? (or have I been converting MM forks to IN wrong, haha)

    Basically, what makes a DH bike an actual DH bike... not just a FR or AM?

    I know it seems kinda like a newbish question, and one that might have been answered before, but im trying to understand the technical differences. Im not trying to "define" DH like they try to do all the time in the AM forum

    Timm
    The main difference between a DH bike and an AM bike is that while the AM bike is designed to ride both up AND down the hill, the DH bike is only designed to go down. Frame geometry and stem length/angle contribute to the ergonomics of the rider and, generally speaking, DH specific bikes have the rider sitting back with the bars a bit higher and wider than an AM bike. DH specific bikes also have a bit more travel than AM bikes; 8-10 inches for DH versus 5-7 inches for AM. Hope that helps!

  3. #3
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    dh 8-10 plush plow slack bike, lower bb, no climb
    fr 6-8 stiff and plush agile steeper for manuvring on skinies and what not, high bb, some climb
    am 4-6 dece stiff steeper yet for trails, mid bb, can climb well

  4. #4
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    To me it's a simple as this; DH bike no front derailleur. FR bike has one.
    "Well I don't drink as much as I ought to."

    ~Jerry Jeff Walker~

  5. #5
    StraightOuttaCompton
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    am bike has 3 rings, fr has two, and dh has one. The newer AM bikes may be carbon or scandium. The fr and dh bikes are aluminum other than the gt fury. The dh/fr bikes have a lower standover and higher bars than an AM bike. DH and FR bikes usually have coil shocks and am bikes have ari shocks to save weight.
    HARDTAIL PRIDE- 09 Kona Five-0

  6. #6
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    SEARCH!!!! dozens if not hundreds of threads dictating the slight differences in geometry, general set-up, and riding characteristics between the three genres of bikes...
    Proud to represent Mojo Wheels.

  7. #7
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    You know, I thought about searching, i really did. Infact, im not a forum newb, just to this one. However, I had no idea what to search for. So I posted. But i did try.

  8. #8
    Petty and weak
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    Quote Originally Posted by Djponee
    am bike has 3 rings, fr has two, and dh has one.
    Sooooo if I take the granny ring off my La Bruja it becomes a DH sled? Wicked, I'm onto it!
    ~ Downride and Freehill, nothing else ~

  9. #9
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    This is a good question and yes it's one that will have been discussed before but for convenience, here are my thoughts on the subject.

    Compared to a freeride bike, a DH bike will probably have (but not exclusively- there will be many examples of exceptions to these rules and some of the measurements will change depending on the size) the following:

    • a lower Bottom Bracket, probably 14" to 14.5". A FR bike will likely have at least 14.5"
    • a much slacker head angle, between 64 and 66 degrees. FR bike will be around 67 degrees
    • be considerably lighter, maybe up to 2lbs
    • be longer in the wheel base, typically DH race bikes are between 45.5” and 46.5” (changes with frame size)
    • slightly longer in the top tube, maybe 22.5” to 24” (again very dependent on the frame size)

    All of these differences, though subtle on paper, will make the bike feel very different on the trail. Ultimately the aim of a DH race bike is to go as fast as possible, making stability at high speeds the key feature. The longer wheel base, slacker head angle and lower bottom bracket are all key in this respect.

    A free ride bike is designed more around pulling tricks, jumps, big drops, riding over ladders and raised platforms etc. The speeds tend to be slower, in some cases very slow, you need to be able to pedal more and therefore need more ground clearance hence the high BB. Manoeuvrability is key, hence the steeper head angle, shorter wheel base.

    Now there are lots of contradictions here – a downhill bike has to be able to jump as you will see in any world cup race. It also has to be manoeuvrable and you need to be able to pedal. The fact that a DH race bike is orientated towards other attributes does not mean it cannot perform others, it just means that the rider will need to compensate more, e.g. more ‘body English’ for tighter turns, ensuring you carry speed through corners rather than scrubbing it off so you don’t need to pedal so much.

    It also works in reverse, i.e. plenty of freeride bikes can be raced. In truth, the material differences will be more apparent only at the margin, that is, a pro-racer will unlikely be competitive on a FR bike versus a DH bike in a world cup event (again, there are exceptions) because they are dealing with such small margins. The more average you are, the less these differences will be noticeable. At the everyday rider level (myself included), the differences are more about marketing than anything material. Thus I want to ride a race bike because that’s what I aspire to and thus I want a bike that is, in my mind, built for racing. In reality, only the messages the marketing team give me that this is a race bike, actually define it as such in my mind.

  10. #10
    I AM I AM
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    Quote Originally Posted by mtnbkr123
    Why do most bikes have more travel in the frame then in the fork? (or have I been converting MM forks to IN wrong, haha)
    Good question - one I was curious about myself as I'm about to build up a DH frame that has 200 odd mm travel in the back but recommends a 180mm fork max
    1" = 2.54cm

    What makes a DH race bike different from a free ride bike, or an all mountain bike. Take for example my Reign x1, or an Intense 6.6. Or a Kona Stinky. How does having a higher and shorter stem/bar combo help while going downhill?
    Geetee has covered your answer really well.
    It also gets complicated when people build up "all round bikes" which can do more than one type of riding reasonably well.

    Short stems change the handling of the bike and also help to get the rider weight furhter back (a requirement for going down really steep hills). But as your stem gets shorter you want to have wider bars (think of doing push ups - your hands are comfortable close together when you're in the up position, but when you're at ground level they need to be further apart for leverage). Having rise in the bars depends on the rider preferance and on the bike geometry - these days people are starting to go towards low ridse handlebars again, I think in the past bikes didn't have as much travel up front so having a higher rise bar also helped get the rider weight back.



    Basically, what makes a DH bike an actual DH bike... not just a FR or AM?
    My simple short answer would be = geometry & weight. Slacker, longer wheelbase, sturdier frame / components and as a result you're probably looking at minimu 20kg weight - AM rigs would be more around the 13kg mark!

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