[ZUMBI]

Hi all You monkeys!
We are thinking of designing a short travel DH/ all mountain frame. What would You expect from a frame like that?The frame will use a redesigned FPS suspension system from our F-44.Thanks for Your help!
cheers!
Pawel

 

[Jase76]

Well I would expect it to have a minimum of 10 inches of travel!

 

[pelo]

66° HA with 6" fork, 5"-5.5" rear travel, iscg, 12-135mm spacing, full length seattube, long and low, short chainstays, light.

 

[ZUMBI]

66° HA with 6" fork, 5"-5.5" rear travel, iscg, 12-135mm spacing, full length seattube, long and low, short chainstays, light.

do You think 67degree headtube is to steep? Im thinking about 150-170mm travel with a 6" fork. The full lenght seatube is a good point.

 

[pelo]

Some forks have adjustable travel, so I was thinking you would like it on the slack side with a full 6"-6,3" setting, when pointing the bike downhill. I think 6" is a bit too much in the rear for an am-bike. Makes it soak up to much of the terrain, in my opinion. It´s better with a little less travel in the rear for snappier handling, but with an agressive geometry for stability?

 

[FCLinder]

6'x6" is were I think its at for an All Mt bike. 67d HT angel, 44" wheel base, 71d Seat Tube, and a low stand over. You guys have a great design to work off. Good luck.

 

[Tootrikky]

A low and slack 6" bike with a seat tube steep enough to get proper leg extension for Super d's. 150 rear end and BB so I can swap out wheels and cranks with my DH rig.

 

[Sandro]

do You think 67degree headtube is to steep? Im thinking about 150-170mm travel with a 6" fork. The full lenght seatube is a good point.

I think a 66 degreee head angle would be perfect. I ride a ReignX, which i think is a perfect example of this kind of bike, and the only thing i would change for downhilling would be a little slacker head angle.
Good luck with your bike!

 

[rockwool]

66° HA with 6" fork, 5"-5.5" rear travel, iscg, 12-135mm spacing, full length seattube, long and low, short chainstays, light.

I second all this. 6" rear is too sluggish for a mini DH. The're many fine 7" DH bikes that would be too close to the feel of a 6incher. 160-170ish fork. Let people lower their forks if they want to climb, 67 HA is too steep for DH. Maxle rear is a nice detail. SHORT CS!!

 

[sbabuser]

Originally Posted by pelo
66° HA with 6" fork, 5"-5.5" rear travel, iscg, 12-135mm spacing, full length seattube, long and low, short chainstays, light.

Take all that above, give it a shock option that'll make it ~4" of travel, and it'd be a decent 4x bike, as well...

 

[RD3]

66° ha
6-8" single crown up front
7" rear via air
135 x 12mm thru axle rear
73mm bb shell
13.4" bb height
16.7" chainstays
keep it light

 

[rockwool]

Take all that above, give it a shock option that'll make it ~4" of travel, and it'd be a decent 4x bike, as well...

That would be great!

 

[Fulton]

i tell you what. if it would make coffee for me in the morning, you'd have a winner.

 

[ZUMBI]

thanks for all the answers!
What about the optimal leverage ratios (start, middle, end)?
thanks

 

[Tootrikky]

thanks for all the answers!
What about the optimal leverage ratios (start, middle, end)?
thanks

Don't follow fads, build around a leverage ratio that Fox and Marzhocci air shocks stock tunes are optimized for.

I have a 4.2" travel SX which I find way lacking in travel for a mini dh. I have found 5-6" is a much better compromise between light and flickable/forgiving.
I took the stock 5th element off and put a fox AVA shock on it, but due to the super low leverage ratio (2" stroke) the rear feels way overdamped, and hence why I suggest an average leverage ratio or you'll end up needing a custom tune on the oem shock.

 

[dirtdigger]

well hears my short travel dh bike that i made out of 4130
HA 66.5
wheel base 1165
cs 445
150 x 12 rear hub
6" x 6" travel
i dont think short chain stays are that great unless you are ridin steep stuff all the time

 

[rockwool]

Short CS is what has made Specialized bikes so fun to ride.. They balance that out with a tad longer TT though (Demo 7 felt supa).

 

[Fulton]

16.75" stays, 1.5 headtube, 66 degree headangle, 6" travel with a 2.5" stroke shock, 13.75" bb, long top tubes, iscg tabs, 12mm x 135 thru axle rear.

 

[dirtdigger]

16.75" stays, 1.5 headtube, 66 degree headangle, 6" travel with a 2.5" stroke shock, 13.75" bb, long top tubes, iscg tabs, 12mm x 135 thru axle rear.

how long will the wheel base be?46"?
maybe go with a 13.25"bb

i think chain stays should be in relation to the wheel base IMO
have ridden a demo 8 and didn't like the short chain stays,the front was to far in front of me, all my weight was on the back wheel, hard to get frunt end around sharp turns blahh blahh.
yip short chain stays are gay

 

[Tootrikky]

Short stays are good for slalom and 4x not for going fast imo. I would rather be over the BB, then over the rear axle aka sx.

the old DH standard of 12x135 would rule......then I would have three different rear axle standards in my stable of bikes that I can barely afford. Most importantly the little bit of weight it will save me over a 150 hub would impress everyone on an RM "look how light my pristine my ultra trendy mini dh bike is thread", because I am not really gonna ride it much anyway, and I won't need a spare rear wheel just a nice light pretty one for RM pictures and digital scale photos.

 

[boone]

I actually like this cat of bike a lot!
Would be great to see a 67 HA w/6" fork; 66 or 66.5 with a bigger fork. Low standover, shorter ST than normal AM bikes. Effective SA around 72. 73mm BB shell with 12X135 rear maxle. One thing a bike like this should have (I think) is an adjustable chainstay system, much like the Knolly system. I think that makes this bike even more adjustable. Optional 1.5 HT.
Rear travel: I don't think that 6" in the rear is too much for an AM bike. There are many bikes that have 6" of travel that are intended for AM and they ride pretty well.
I would suggest 6" in the rear, fairly linear to start increasing progressively towards the end. Makes it soft over the small bumps but able to take a good hit without relying too heavily on the shock to control bottom. I am no brainiac on this but, it might be hard to have a setup that feels nice for DH rippin AND aM climbing and trail riding. One of the two categories is gonna suffer a bit.

 

[xy9ine]

16.75" stays, 1.5 headtube, 66 degree headangle, 6" travel with a 2.5" stroke shock, 13.75" bb, long top tubes, iscg tabs, 12mm x 135 thru axle rear.

that sounds about right. apart from a bit more travel (~7"), my pdc is in that ballpark (16.75" cs, 65-66ha, 13.25bb, longer tt, etc). the long tt / stubby rear is a fun, snappy configuration. surprisingly stable in the knarl, and a wicked cornerer. short cs's can be pretty damn effective.

 

[Tootrikky]

that sounds about right. apart from a bit more travel (~7"), my pdc is in that ballpark (16.75" cs, 65-66ha, 13.25bb, longer tt, etc). the long tt / stubby rear is a fun, snappy configuration. surprisingly stable in the knarl, and a wicked cornerer. short cs's can be pretty damn effective.

W/ a high pivot yes they are essential.

 

[Fulton]

and I'm serious about the coffee thing.

 

[FactoryCostcoDH]

You guys should seriously consider being one of the first to design a truly race-oriented mini DH bike (not just your average all mountain bike like everyone else has made). Almost like a mini F-44 with a 2:1 ratio, 5.5 inches of travel 13.25" BB height, no more than a 66 degree HA with a 6" fork, and a semi-rearward axle path. Oh and adjustable rear travel would be a nice addition as well (for 4x or DJ). I would kill for a bike like that.

 

[FactoryCostcoDH]

And like others have mentioned above, try to keep the travel around 5-6" or else it almost defeats the purpose. Just make it nice and progressive

 

[jeremyb]

i tell you what. if it would make coffee for me in the morning, you'd have a winner.

How many inches in the rear?

 

[ZUMBI]

Just like factorycostodh wrote we dont want to make another standard AM frame but something more on the DH side which would be "uphillable" just to get You to the dh track. Lots of people dont live close to ski lifts but they have dh tracks.Why should You have to walk with your heavy dh sled up when you could slowly get to the top riding.I think a bike like this would also be good for avalanche races.
I think a 1:3 start and 1:2.5 end ratio would be nice with a linear progression rate up the travel.I think I would shorten CS just a bit and lower the BB to 13.5 or even 13.25 with 6" travel.Get the top TT a bit longer.The frame will need a front der mount. Two chainrings with a chain guide. We plan to build a prototype early spring.Thanks for all the ideas

 

[norbar]

You should think about stiffnes of the bike as probably some people will want air shocks on that kind of bike. The rest of the numbers are great.
Seems that you've got sth to do during the winter

 

[rockwool]

Just like factorycostodh wrote we dont want to make another standard AM frame but something more on the DH side which would be "uphillable" just to get You to the dh track. Lots of people dont live close to ski lifts but they have dh tracks.Why should You have to walk with your heavy dh sled up when you could slowly get to the top riding.I think a bike like this would also be good for avalanche races.
I think a 1:3 start and 1:2.5 end ratio would be nice with a linear progression rate up the travel.I think I would shorten CS just a bit and lower the BB to 13.5 or even 13.25 with 6" travel.Get the top TT a bit longer.The frame will need a front der mount. Two chainrings with a chain guide. We plan to build a prototype early spring.Thanks for all the ideas

Maybe give it a the higher BB in 6" mode and to be able to swap to a shorter shock for 5ish inches? ...and adjustable CS for the sake of world peace.

 

[TheInedibleHulk]

When you are done with the short travel dh bike, maybe you could build a fully suspended hardtail or a long travel hillclimb bike.

 

[Fulton]

i don't think there is really a set standard on what this "genre" is yet, think about how many frame's intense has, that come relatively close to what your talking about. socom, 2 5.5 frames, 2 6.6 frames, and the uzzi

pick one direction, and go with it. trying to cram everything into one frame will leave you with a bike that probably does alot of stuff pretty good, but nothing great.

 

[rosenamedpoop]

5.5" to 6" travel with a 6" fork.

Full length seat tube with an angle appropriate to climbing.

12mm thru axle rear.

1.5" head tube.

ISCG tabs.

Front der. compatible.

True DH geometry. If ths is to be a real "Mini DH" frame it should have geo to mimick a DH race frame when sagged. So this means that the BB should acheave a sagged height of 10.75" to 11"

Geo as follows:

~65 deg HA
~12.75" BB
~17" to 17.25" CS

 

[norbar]

Maybe give it a the higher BB in 6" mode and to be able to swap to a shorter shock for 5ish inches? ...and adjustable CS for the sake of world peace.

Maybe instead of that an adjustable head angle? It changes much more than cs and when I compared usefullness of both ideas on different bikes adjustable ha seems a better idea.

Geo as follows:

~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.

 

[ZHendo]

as a mini dh bike though, i think the geo should be a little more lively than a full on dh bike. in my opinion, it is very important that the bike have a long-ish top tube and shorter stays. my sx trail is an exponentially better handler than my old yeti asx. the asx had a shorter top tube, higher bb, steeper angles, and much longer stays. the sx feels fantastic because the stays are so short the bike can really be worked through any terrain. just do some testing on the stay length, i'm pretty sure that the general concensus will be that the shorter stays make the bike more fun. it is called a mini DH bike, so it will be riding less technical terrain. it should turn quicker and rail corners. i agree with rosenamedpoop on the low bb, but i think the head angle should be about 66 to 67 degrees with a 160mm travel fork.

 

[ZUMBI]

i don't think there is really a set standard on what this "genre" is yet, think about how many frame's intense has, that come relatively close to what your talking about. socom, 2 5.5 frames, 2 6.6 frames, and the uzzi

pick one direction, and go with it. trying to cram everything into one frame will leave you with a bike that probably does alot of stuff pretty good, but nothing great.

mini dh is the description of this frame design.This will not be a "do it all in one" frame which really means "do it nothing in one". As I wrote earlier it will be an "uphillable" dh bike.
what do You think about the levarage ratio changing from 1:3 - 1.25 in a linear rising rate?

 

[FactoryCostcoDH]

If I could have it my way, I would say 1:3 to 1:2.25 just to achieve a really nice aggressive feel, and not have to worry about bottoming as much with the lesser amount of travel. I also think that a 66 degree HA is a MUST or else it isn't much of a mini DH bike in the first place. People who want a steeper HA for any reason can always put on an adjustable travel fork and put it on a lower setting, while on the other hand people who want a slacker HA would have to put on a longer fork, possibly distorting the geometry of the bike and killing the short travel feel. Low BB and standover are fairly essential as well, but not as much. Although if it is truly to be a "mini DH bike" it should be designed like one.

I still really like the idea of multiple shock mounts for adjustable travel. Let's say 4.0" for one and 6.0" for the other. Hell, with that kind of setup you could go DH, DJ, and 4x all in one ride. How sick would that be?!

 

[FactoryCostcoDH]

Just another idea to throw out there is the possibility of an adjustable seat tube angle

 

[norbar]

mini dh is the description of this frame design.This will not be a "do it all in one" frame which really means "do it nothing in one". As I wrote earlier it will be an "uphillable" dh bike.
what do You think about the levarage ratio changing from 1:3 - 1.25 in a linear rising rate?

1:3 - 1:2.5 is nice as it's not an fr bike made for drops that needs a lot of progression. Imho dh bikes need it less.
And about the idea of mini. It would be good as it would also be an uphillable dh bike that's much usefull for lighter dh tracks (Many event's take place on much easier tracks than WC courses, you should know that living in our country )

 

[ZUMBI]

1:3 - 1:2.5 is nice as it's not an fr bike made for drops that needs a lot of progression. Imho dh bikes need it less.
And about the idea of mini. It would be good as it would also be an uphillable dh bike that's much usefull for lighter dh tracks (Many event's take place on much easier tracks than WC courses, you should know that living in our country )

yep.I know what You mean