Downhill pumptrack question- Mtbr.com
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  1. #1
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    Downhill pumptrack question

    The next trail I'm going to build is going to be something like a downhill pumptrack (machine built). I want to incorporate lots of rollers (both big and small) and berms into a trail that will be over a mile long. There are a few flat sections but most of the trail was flagged at a 6-8% grade.

    I was wondering if someone else has built a downhill trail with lots of rollers/pumps before. What was the % grade of the trail and what was the spacing in between the rollers? I'm sure there's a lot of variables but I'd like to get a general idea of how to space my rollers.

  2. #2
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    Suggest you start searching for “flow trails” which, to me, sound like exactly what you’re trying to do.

  3. #3
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    Watch this video and tell me if it's what you have in mind. Keep in mind, I didn't ride this to go fast on, I rode it get video that would let people SEE the trail. So yeah, I'm holding back a lot. Just pay attention to the shapes

    https://www.youtube.com/watch?v=XBSmNaCfpks&t=1s

  4. #4
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    The average flow trail might have some rollers thrown in here and there but there's usually not very many. I want to have a lot of rollers so you can actually pump through them to generate speed.

    Cotharyus, it's hard to see the shape of the rollers from the video but I was thinking something similar to the trail in this video (starting at 2:25)

    https://www.youtube.com/watch?v=-LDkBrkwwxw

  5. #5
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    Hm, ok. Check out Springboard (Trailforks | Strava) at Alsea Falls. It's all rollers and berms. Some of them you can boost for air, a few that you can clear as doubles if you're fast enough.

    P.S. don't read too much into the uphill shown on Trailforks... it's only got one climb at the 0.85mi point and it's about 50ft of elevation gain. The digital elevation model on there is a bit wonky. Strava seems accurate.

  6. #6
    always licking the glass
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    Downhill pumptrack question

    Sounds like a dual slalom. There’s plenty of flow trails to look at for suggestions.
    Last edited by stripes; 02-13-2020 at 12:11 AM.
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  7. #7
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    The Endor Flow Trail at Tamarancho in Marin is sort of like that. The design intent is that you don't need to either pedal or brake going downhill.... though I'm not sure how many can do it w/o braking!

    Video with bad lighting but shows a pumpy ride the whole trail:
    https://www.youtube.com/watch?v=QFeoHXDyeU8

    Better video, though it doesn't show the whole trail:
    https://www.youtube.com/watch?v=LMZXkzguwc8

    A few sections of the Soquel Demo Flow Trail are also like this.

  8. #8
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    Much longer than what ever seems right when on foot standing there with a shovel or hoe in your hand...at least thats my experience.

    Ride something you think is awesome, then take a measuring tape, or take pictures with your bike in for scale. " That one was cool, looks like 5 bike lengths". Then go from there.

    Edited to add this.
    If its downhill only and you work the rollers/jumps the speed will get out of control. You might want need to hook it slightly uphill every once in a while.

  9. #9
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    The The Endor Flow Trail looks pretty fun and more along the lines of what I want to build. Giving a little extra spacing will probably be a good idea since a trail will always ride faster after it's had a winter to harden. I'd rather not use the trial and error method since shifting/rebuilding rollers after the fact will be a lot of work.

    Sounds like my best bet will be to measure the spacing on any existing rollers and add in progressively more space if there are sections where you can pump and gain speed.

  10. #10
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    You might want to check out lower Flow State Trail at Raging River here in WA. The grade is probably in the 5 -10% range. The trail is more of a jump-less flow trail but it does have some pump-able rollers. Its other main feature are big sweeping turns.

  11. #11
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    If you really want pumptrack features, you have to lower the grade to 3-6%. Anything more will be wayyyy too fast. A typical flow trail is 5-8%. Just remember to keep the grade consistent and manage the speed with grade reversal as needed.
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  12. #12
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    Hi, indiemtbkr, I have been researching this exact topic because I am planning to build something very similar: a downhill pumptrack trail, or "flow trail but for dj bikes and bmx bikes".

    which brings me to what I think is an important consideration: what kind of bikes will ride the trail? suspension bikes or hard tails? what kind of tires? and how smooth is the surface?
    In my case, I plan to make the surface low-friction (like a proper pump track), and to ride it on bmx or dj bikes which have tires with low rolling resistance and hard tail frames, where every bit of energy from your legs gets pushed into the ground, requiring less grade to give more momentum.


    I have done some homework and will share what I have learned with you:
    * https://forums.mtbr.com/trail-buildi...ow-943688.html. This was an interesting thread. numbers seem to be between 5-8%, but seem to assume trail bikes and more rolling resistance.I found this quite surprising TBH. The local hill at my house has 200m elevation change over 5km, so that's 4%, If i just roll down I pick up too much speed quickly and need to brake, and that's on a rough surface with a trail bike.
    * I dug through the UCI bmx track guidelines. (65 or so page pdf document). While it is not written for this exact question, it contains some helpful pointers. I learned that a proper UCI bmx track has an 8m high starting hill, a minimum length of roughly 350m, and a drop (level difference between bottom of start hill and finish line) of no more than 2 meters. Thus, the most extreme overall grade would be 10m over 350m means 2.85% grade, down to 8m over more than 400m so < 2%.
    Needless to say, bmx racers rip through the course at high speeds. Also interesting, the document mentions that the first straight is the fastest one, though I'm not sure what lesson we can draw from that.
    * a normal pumptrack has by definition 0% overall grade, but yet strong riders can fly through them at high speed, but that gets tiring quickly


    I suspect that at least for DJ bikes/bmx, the ideal grade is somewhere around 2% depending on how much energy you want to put into pumping. I too, am looking for more guidance on this.

    A question I'm personally still struggling with, is how can one compensate for a too steep grade. Certain features lend itself well to speeding up (rollers), while others - I *think* - lend itself to slowing down, I'm not sure which ones exactly... step downs (jumps with landings lower than the takeoff)? drop offs? high (near vertical) jumps?
    This is a topic I personally find fascinating and would like to dig a bit more into, because I have a grade around 4% and I suspect it's too steep. I have also read a comment somewhere along the lines of "nothing soaks up speed more than a berm that's too wide". Is there anything written on the topic of how different features effect (increase vs decrease) speed? I couldn't find it.

    Not sure if this was helpful, but anyway...

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