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short travel dh frame

rosenamedpoop

rosenamedpoop

Turbo Monkey
Feb 27, 2004
1,284
0
just Santa Cruz...
norbar said:
RE: ~65 deg HA

Evil! Mini Dh should be a bike for less hardcore dh trails. That's why it's mini ;) so such head angle is not the best idea. 66-67(maybe 67.5) would be better.
CS. Should be also shorter.
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Well, if you don't want a mini DH bike to have real DH geo, you can go pick up a nice 5" to 6" trail bike from any number of companies. Those bikes are great, but not "mini DH" bikes from my perspective.

There are very few 5" to 6" travel bikes out there with true DH geo. Personally I see a market for these bikes. There are companies beginning to capitalize on the slopestyle tag and making shorter travel slack/low frames, but they need to be "uphill-able" (as Zumbi said).

I want a short travel (5-6") frame with DH geo I can ride up a dang hill with my seat up. I don't care if I can't win an race XC on it, I just don't want to have to walk up to ride down (riding down pinned being the point).
 
norbar

norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
11,369
1,605
Warsaw :/
rosenamedpoop said:
Well, if you don't want a mini DH bike to have real DH geo, you can go pick up a nice 5" to 6" trail bike from any number of companies. Those bikes are great, but not "mini DH" bikes from my perspective.

There are very few 5" to 6" travel bikes out there with true DH geo. Personally I see a market for these bikes. There are companies beginning to capitalize on the slopestyle tag and making shorter travel slack/low frames, but they need to be "uphill-able" (as Zumbi said).

I want a short travel (5-6") frame with DH geo I can ride up a dang hill with my seat up. I don't care if I can't win an race XC on it, I just don't want to have to walk up to ride down (riding down pinned being the point).
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I'm also not thining about a bike like Vp-Free was meant to be (uphills, fr, some dh ) cuz it's gonna be sth strange (like vp-free :P). I just don't think we need sunday geo for such bike.
The fact that there is little number of shorter travel true dh bikes may not mean there is market place for it. For sure racers and people with $$$$ would buy it as their n'th bike but that's a small market. It would be good as it could be your 1st bike. That would have a bigger market. If the bike has to be short travel I would like it to be very agile. Sunday geo won't make it as agile as I would want it to be.
 
pelo

pelo

Monkey
Jun 11, 2007
708
0
With a slacker geo, it´s more like you can lean to turn, instead of steering through turns like with a steeper HA.
A slack geo (sunday geo?) doesn´t mean it can´t be agile. A mini DH can be built much lighter and with less travel it will be agile enough, I think. Also, getting the right proportion of cs, bb and toptube to mach HA, I guess it´s possible to make a really fast but agile and fun mini-dh?
The big market is always a step behind anyway, so somebody has to make the first move. Progression is a good thing.
Steep HA:d 6":ers is pretty useless in my opinion. With all that travel they are sluggish at low speed and kind of unstable becuase of geo at speed. Good geo is better than travel, if it´s supposed to be a mini-dh.
Big market and old fat AM-men will eventually follow, so no worries.:biggrin:
 
norbar

norbar

KESSLER PROBLEM. Just cause
Jun 7, 2007
11,369
1,605
Warsaw :/
Yea I know it's usualy like that but think about it. How many people do you know that don't race(cuz racers are not such a big market) and would like such geo(especialy that rosenamedpoop gave the same cs and bb as dh bikes have in addition to slack so his idea looked for me like "let's make an exact copy of a dh bike but less travel" [no offence to the author of the idea]) .
And about geo hm I was just looking at the bike different than you. It can be made slack but reasonably short(both WB and CS). I think 2stage had such frame and it looked kinda nice.
 
ZUMBI

ZUMBI

Chimp
Mar 22, 2007
67
0
Myslenice, Poland
We are thinking about shortening the CS a bit and making a proportionally longer TT. The angles will be the same as on the F44 but for a 6" fork.If You want a steeper head angle You can always install an on the fly travel adjustable fork and lower it on the uphill.Lots of people want to have a bike which will get them on top of a downhill track and then enjoy the descent.This is what this design is about.
 
rosenamedpoop

rosenamedpoop

Turbo Monkey
Feb 27, 2004
1,284
0
just Santa Cruz...
norbar said:
I'm also not thining about a bike like Vp-Free was meant to be (uphills, fr, some dh ) cuz it's gonna be sth strange (like vp-free :P). I just don't think we need sunday geo for such bike.
The fact that there is little number of shorter travel true dh bikes may not mean there is market place for it. For sure racers and people with $$$$ would buy it as their n'th bike but that's a small market. It would be good as it could be your 1st bike. That would have a bigger market. If the bike has to be short travel I would like it to be very agile. Sunday geo won't make it as agile as I would want it to be.
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In my eyes, the VPfree is a complete disaster of a bike. Too steep, bb is way too tall, too heavy, and too much travel. Not a mini-DH bike.

As far as a short travel bike with DH geo being an "n'th" bike, I would ride it daily and dust of my big bike once in a while.

Again, if what you want is a 5" to 6" bike with steeper angles, there are already more of those than you can shake a stick at. I wouldn't want them because I don't like the geo.
 
rosenamedpoop

rosenamedpoop

Turbo Monkey
Feb 27, 2004
1,284
0
just Santa Cruz...
ZUMBI said:
We are thinking about shortening the CS a bit and making a proportionally longer TT. The angles will be the same as on the F44 but for a 6" fork.If You want a steeper head angle You can always install an on the fly travel adjustable fork and lower it on the uphill.Lots of people want to have a bike which will get them on top of a downhill track and then enjoy the descent.This is what this design is about.
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Money Zumbi!

Are you going to set static BB height lower than the F44 to achieve the same sagged BB height?
 
S

SPDR

Monkey
Apr 21, 2006
180
0
Engerland
Why the longer front end to make up for the shorter CS? Surely the thing that makes a bike feel right is the BB to bar dimensions?

If you're going to make the rear end shorter to make it a bit more nimble, do it but keep all the other contact points the same, just drop them 2" (or whatever the difference in axle to crown length is between 8" dual crown and 6" single crown).
 
ZUMBI

ZUMBI

Chimp
Mar 22, 2007
67
0
Myslenice, Poland
What would You say about a frame that would have a possibility of mounting two different shocks (8.5X2.5 giving 160mm travel or a 7.5X2.0 giving 140mm travel) there would be two sets of lower links.The shorter shock will be mounted to the lower links and the longer shock will be mounted to the swingarm like on the F44.With each frame You will get both sets of lower links.There will also be a possibility of changing geometry (head and seat angle).The leverage ratio will change 1:3 - 1.25 on both shocks.Kind of tricky but it works :D Ill show some drawings soon...
 
S

skinny mike

Turbo Monkey
Jan 24, 2005
6,415
0
ZUMBI said:
What would You say about a frame that would have a possibility of mounting two different shocks (8.5X2.5 giving 160mm travel or a 7.5X2.0 giving 140mm travel) there would be two sets of lower links.The shorter shock will be mounted to the lower links and the longer shock will be mounted to the swingarm like on the F44.With each frame You will get both sets of lower links.There will also be a possibility of changing geometry (head and seat angle).The leverage ratio will change 1:3 - 1.25 on both shocks.Kind of tricky but it works :D Ill show some drawings soon...
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this concept is intriguing.
 
spacemanspiff06

spacemanspiff06

Monkey
May 12, 2005
977
0
roanoke va
pelo said:
66° HA with 6" fork, 5"-5.5" rear travel, iscg, 12-135mm spacing, full length seattube, long and low, short chainstays, light.
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dido, but long CS are a must. my howler is sitting at 17.1 and even with 4 inches of travel is is the most speed-hungry and stable bike i've ridden. oh, and make it a single pivot too. I'll take two to go and a liter a cola.
 
Ian F

Ian F

Turbo Monkey
Sep 8, 2001
1,016
0
Philadelphia area
Things that matter to me... and why I still ride a 10 year old frame:

triple-chain ring capable (preferably E-type)

Dual crown fork (some of us retro-grouches will never feel warm and fuzzy on a single-crown with over 5" of travel)

Adjustable geometry: low/slack for lift riding and a bit taller/steeper for all-around riding.

Full-length seat tube would be nice, although I realize not always possible with some designs. But it's not the end of the world... I just keep two seat/posts for different riding.

Bosses for at least one bottle cage.

When did the guys from Cortina move to Poland? ;)
 
bullcrew

bullcrew

3 Dude Approved
Dec 8, 2004
8,911
2,574
I'm dude playing dude pretending to b another dude
Ian F said:
Things that matter to me... and why I still ride a 10 year old frame:

triple-chain ring capable (preferably E-type)

Dual crown fork (some of us retro-grouches will never feel warm and fuzzy on a single-crown with over 5" of travel)

Adjustable geometry: low/slack for lift riding and a bit taller/steeper for all-around riding.

Full-length seat tube would be nice, although I realize not always possible with some designs. But it's not the end of the world... I just keep two seat/posts for different riding.

Bosses for at least one bottle cage.

When did the guys from Cortina move to Poland? ;)
Click to expand...
Wrong forum this is DH not XC! :D
 
Stray_cat

Stray_cat

Monkey
Nov 13, 2007
460
0
Providence
For leverage ratios it'd be cool if you could tune the F44 suspension to a low/active ratio for the first 2/3 of travel, and then have it ramp up in the last 1/3.

I'll certainly second the idea of short cs too.
 
D

djb

Monkey
Apr 6, 2006
173
0
VanCity
If part of the market you're aiming for is short travel DH, wouldn't it be wise to also make it compatible with a shorter travel DC fork?

Like a 7" Travis, or Boxxer Ride or something along those lines.
 
nickf

nickf

Chimp
Dec 28, 2007
3
0
Seattle
check out the commencal mini dh. it seems to be perfect for what you're looking to build. i even has an adjustable head angle, not that i think that's a very easy thing to personally build. 6 inches of travel, 66 head angle. the frame it being redone for 2009 with a lower shock mount and less gussets and beef. the stock build has a 66 up front.
 
_*sTiTcHeS*_

_*sTiTcHeS*_

Monkey
Apr 24, 2006
386
0
yea the commy is nice.

it sounds like the bike you're going to end up with is a standard bike that every company already puts out.

why does the bike always have to be pedalled up the hill? no one makes a short travle dh bike for real.

most bikes you get with 4-6 inches come with a front deraileur, steep head angle, and long chain stays.

adjustable head angle 65-67
adjustable chain stays 410-420mm
wheelbase 1140-1150mm
bb hight adjustable -1cm-+1cm
seat slamming abilities
iscg05
12x135 maxle or ti thru axle
post rear brake mount
10mm shock bolts
1.5 headtube
built in seat clamp
73mmbb
high single pivot with no linkage for a rearward axle pivot and lightweight
weight without shock 6.5lbs

basically a specialized sx with some demo 8 mixed in type of thing
 
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