Dirt Jumper Bikes

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1/3/2018 8:35 PM

I've been riding dirt jumpers at the Lumberyard in Portland. Renting their bikes. Ready for my own....need some input.

65 years young, 160#, 5' 8"

Thanks

Tim

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Germany 1975 250 CZ Centerport, laydown shocks, mikuni with reed valve, Marzocchi forks with me as the motopilot

1/3/2018 9:49 PM

bmx or mtb?

I ride a Deity Cryptkeeper (26") and love it. I run a fork set to 70mm travel so its shorter in front and a little steeper head angle.

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1/3/2018 9:51 PM

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1/4/2018 8:49 AM

Demo the bikes at the Lumberyard, see what you like, and buy it at the end of the year from them. If I where you, I would get a 26". If you like loud and rigid bikes, get an aluminum frame, if you want something quieter and more forgiving, get steel.

Here's what I have but it's old school and you can't find them anymore...
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1/4/2018 9:35 AM

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1/4/2018 11:06 AM

I just picked up a used Morpheus dirt jumper and i am having a blast on it.. right now mostly the skate park but as soon as our jump park thaws out ill be there.. So light and responsive its almost scary
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1/4/2018 7:25 PM

Thanks for the information. A 26" and steel is what I'll go with.

So the fork length is used to change the head angle. What is a good angle to shoot for?

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Germany 1975 250 CZ Centerport, laydown shocks, mikuni with reed valve, Marzocchi forks with me as the motopilot

1/4/2018 8:10 PM

No advice to give you but props for staying active.

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"Sorry Goose, but it's time to buzz the tower."

1/5/2018 8:16 AM

Tim507 wrote:

Thanks for the information. A 26" and steel is what I'll go with.

So the fork length is used to change the head angle. What is a good angle to shoot for?

Head angle is a preference - in a way. Steeper head angles give you quicker handling but may be less stable and predictable. A steeper head angle (front tire is closer to the center of the bike) is good for hard surfaces like skate parks and good dirt jumps. A slacker head angle (front tire is further from the center of the bike) is better for more downhill type stuff like dual slalom and bigger, less groomed, dirt jumps. You can also play with stem lengths. I think a good starting point for stem length is 50mm. A longer stem feels wrong on a dirt jumper. A lot of people are going with super short stems now and I think that's to get your weight on the back tire. Maybe Rosebud or Seth has info on the shorter stems since I have not tried anything shorter than 50mm. Handlebars are another adjustment you can make and there are huge variations on what people think works best.

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1/5/2018 11:05 AM

Most dirtjump bikes have very short almost zero rise stems..
Just getting used to Dj's myself i quickly notices how much steeper the head angle is on the Dj from my Dh and Enduro bikes, almost like a bmx bike.. when jumping this little thing i learned not to try to muscle it like a Dh or reg mtn bike, i just kinda let it go and keep your weight centered over the cranks, and it seems to know where to go. I also put a pair of Renthal fat bars from my DH bike and they are pretty wide and made the bike much comfy and more predictable or less sketchy. Putting a bigger tire like a 2.4" might helps with control and landings.

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1/5/2018 12:36 PM

Ya, I find the shorter fork/steeper head angle just helps it feel better on steep jumps and more like a bmx bike. Most frame websites will give you a head angle with a certain fork height (or a 100mm travel fork for example).

https://www.deitycomponents.com/cryptkeeper_frame.html

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1/5/2018 1:40 PM

I run a P3 specialized. Like it better than the octane I built up earlier.

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