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Shorter and shorter CS's = too unstable??

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
Hey all...

As these CS lengths keep getting shorter and shorter (more-or-less customers pushing it), do you feel as if you can reach a point where it is just too unstable to want to ride anything other than manuals??

14.75 is the shortest I have yet to see on a production frame, and thats the atomlab trailking. But if you ask me, it seems as if that frame would be very unstable jumping big lines. YES? NO? Am I WAY off the charts as to how you all feel when riding such a short bike?

Next... If the bike has that much shorter of an ass-end, do most of you like to see a longer effective TT, or does it just help to have the wheelbase that much shorter?

Thanks
 

Castle

Turbo Monkey
Jun 10, 2002
1,447
0
VA
yup shorter wheelbase means less stability and more flickability/spinability and vice versa
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
I am well aware thats what that means.. But I'm asking what you all, the riders, have to say about it. Do you want as short of stays that you can possibly get? Or is that just a "fad" I guess...
 

Castle

Turbo Monkey
Jun 10, 2002
1,447
0
VA
personal preference really, I'm enjoying the 15.625" stays on my mob with 26" wheels......

and 13.75-14" is what I like on a 20"

edit: don't you or your father build bikes? Build one up and give it a try and see what you think.... ride what you like... What I/we like doesn't mean you will.... or suit your style
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
I realize it all comes down to personal preference... But after modeling my new frame and seeing how short I can actually make the stays, and how short people are making them, I just wanted to get a bit of an insight on what people 'round these parts were thinkin'.

I asked my father.. But his oldschool-building doesnt like to see anything under 16.5 :twitch:
 

Castle

Turbo Monkey
Jun 10, 2002
1,447
0
VA
gotcha, the 14.75 on the trail king I'd venture to guess is for 24" wheel acceptance
 

Stoked

Turbo Monkey
Nov 28, 2004
1,813
1
LI, NY
the new fallguys have a 14.25 cs. there is a limit to how short a frame can be and your comfort level. i just don't know what that is with a 24" frame. my friend has an arcade 20" (custom solid) with 12.75 cs. that is def past my limit on a bmx. i'm stoked to see how my new fallguy will feel.
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
14.75 Trailking is on 26's. I *COULD* get the stays down to 14.5ish any have plenty of space on the crank/tire clearance... but I dont feel like that would be a smart move. I feel like I would be dreading and it would feel rather un-stable...
 

Castle

Turbo Monkey
Jun 10, 2002
1,447
0
VA
yeah I was thinkin they added the 14.75 so it could accept a 24" wheel (shorter position) comfortably or 26" wheel (longer position)..... like the Dobermans....

I haven't seen a trailking yet with 26's and slammed at 14.75.... anyone got a pic?
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
Its built around twosixes. Mainly because of the BB height...

I think I'm going to shoot for 14.75 and make it adjustable back to 15.75. Then, with my shadow I'll be able to dial it in around where I'm most comfortable...
 

Cru Jones

Turbo Monkey
Sep 2, 2006
3,032
0
Hell Track
IMO, the stays on DJ/Street/Park 26" bikes should be as short as reasonably possible... so right around 14.5ish. That long of stay will still be very stable compared to most bmx bikes (which is what these bikes should ride like). Plus, the bigger wheels, lower BB relative the axle line, and slack HT angles make a two six more stable than a bmx.

The real question should be how high should the BB be. The Trailking has a 13.3" bb which is quite a bit higher than most that are around 12 to 12.5. But, again, I think the higher BB will make it handle more like a bmx bike, which IMO, should be the goal for these types of bikes.

I think companies should keep experimenting with shorter back ends and higher BBs until the bike becomes too unstable, then back it off a tad to achieve perfection. Maybe that's what they did with the Trailking.
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
IMO, the stays on DJ/Street/Park 26" bikes should be as short as reasonably possible... so right around 14.5ish. That long of stay will still be very stable compared to most bmx bikes (which is what these bikes should ride like). Plus, the bigger wheels, lower BB relative the axle line, and slack HT angles make a two six more stable than a bmx.

The real question should be how high should the BB be. The Trailking has a 13.3" bb which is quite a bit higher than most that are around 12 to 12.5. But, again, I think the higher BB will make it handle more like a bmx bike, which IMO, should be the goal for these types of bikes.

I think companies should keep experimenting with shorter back ends and higher BBs until the bike becomes too unstable, then back it off a tad to achieve perfection. Maybe that's what they did with the Trailking.
Hmm... The BB's 12.5-13 depending on the fork I'm running. So you feel like I should just go for it? maybe make it have 14.5 -> 15.75 so that I can get the axle just where I want...

Cru.. What are you're stays and BB at now?
 

Cru Jones

Turbo Monkey
Sep 2, 2006
3,032
0
Hell Track
My Simple is at 15.5 and 13, but I've always wanted to try shorter and higher. I've never been on a trailking. I would def go for the 14.5 to 15.75. As for the BB, that's up to you. But, I think anything up to at least 13.5 would still be more stable than a bmx.
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
My Simple is at 15.5 and 13, but I've always wanted to try shorter and higher. I've never been on a trailking. I would def go for the 14.5 to 15.75. As for the BB, that's up to you. But, I think anything up to at least 13.5 would still be more stable than a bmx.
Well, as of right now, I'm going to keep the BB at the same height. (a lot less I'll have to modify on the fixture ;) ) I think thats where I'm going to head with the stays...

There is way too much to think about with this build... Being short on money and needing a new fork, stem, bars, chainwheel, front hub, and rim... Well. You get the idea... HA! Hopefully by march 29th I can find a few more bills to get my bike built up how I'd like to see it.
 

Castle

Turbo Monkey
Jun 10, 2002
1,447
0
VA
Cru, how's your tire clearance slammed at 15.5? and what does the simple chainstay yoke look like, cupped? On my mob at 15.625 I can fit a holly roller 2.4 with a nats ass to spare and a 2.2 with room to spare.....
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
Cru, how's your tire clearance slammed at 15.5? and what does the simple chainstay yoke look like, cupped? On my mob at 15.625 I can fit a holly roller 2.4 with a nats ass to spare and a 2.2 with room to spare.....
As modeled... My frame should fit a 3.5" at 14.5" stays...
 

cmc

Turbo Monkey
Nov 17, 2006
2,059
5
austin
IMO, the stays on DJ/Street/Park 26" bikes should be as short as reasonably possible... so right around 14.5ish. That long of stay will still be very stable compared to most bmx bikes (which is what these bikes should ride like). Plus, the bigger wheels, lower BB relative the axle line, and slack HT angles make a two six more stable than a bmx.

The real question should be how high should the BB be. The Trailking has a 13.3" bb which is quite a bit higher than most that are around 12 to 12.5. But, again, I think the higher BB will make it handle more like a bmx bike, which IMO, should be the goal for these types of bikes.

I think companies should keep experimenting with shorter back ends and higher BBs until the bike becomes too unstable, then back it off a tad to achieve perfection. Maybe that's what they did with the Trailking.
i am psyched on everything about the Trailking (super short cs and long front end) EXCEPT the bb height. my current bike is just under 12.5" and i don't think i want it any higher. guess i gotta ride one.
 

Castle

Turbo Monkey
Jun 10, 2002
1,447
0
VA
As modeled... My frame should fit a 3.5" at 14.5" stays...
is that using a cupped stay yoke? bent seat tube? and that still allows clearance for cranks? I'm just wondering more then anything, sounds pretty unique....
 

Sir_Crackien

Turbo Monkey
Feb 7, 2004
2,052
0
alex. va. usa.
yes a bike can have 14.5" chainstays and still have a 2.5" tire. just look at alot of trials bike that are avaliable namely echo.

short chainstay are not going to make a bike more unstable percey but will make it tend to act better on the rear wheel and actually want to be onthe rear wheel. it also has the side effect to make it easier to loop out. the trailking frame does have a long front end for a street/urban bike. this make up for the short chainstays in the stability department. see my thread onteh trailking for more info
 

Castle

Turbo Monkey
Jun 10, 2002
1,447
0
VA
IMO shorter chainstay positions do make a bike less stable.... On a number of diff. bikes I've owned moving the wheel towards the rear of the stays made a significant difference in stability (.243, endless, sovereign, jackal, mob and a number of different 20's) and the same for shortening it def. took away from the stability... Now I do agree that if I could've changed the front-center length as well increasing the wheelbase would've added stability....

I do agree that the shorter stays make the bike act better while on the rear wheel and easier to get the front end up/loop out....

hurry up and get that thing built! both of you!

edit: like cru said almost anything with big wheels after riding a 20" for a while feels pretty stable...
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
22,253
1,951
In my pants
One thing to keep in mind is the relationship between BB height and chainstay. Lower the BB and it becomes harder to get the front end up.

So a shorter chainstay should go hand in hand with a low BB.

Cru's ideal ride of a short chainstay PLUS a high BB will give you a manualing machine........but in my opinion make it less stable to jump.

The BB on my dj bike is just over 11". But even there I don't have any problem really getting over the rear and I feel WAY more stable jumping it and pressing hard tight berms being more between the wheels rather than above the axles. So in my case I could see an even shorter chainstay because my BB is low and I want to keep it there.
 

sittingduck

Turbo Monkey
Jun 22, 2007
1,962
0
Oregon
At 14.5 and with a decent sized tire (2.3 Krad) your tire would be about half an inch from the BB shell. I'm pretty sure that clearance becomes a pretty tricky issue going that short.
 

sittingduck

Turbo Monkey
Jun 22, 2007
1,962
0
Oregon
The BB on my dj bike is just over 11". But even there I don't have any problem really getting over the rear and I feel WAY more stable jumping it and pressing hard tight berms being more between the wheels rather than above the axles. So in my case I could see an even shorter chainstay because my BB is low and I want to keep it there.
Damn, I thought my BB was low at 11-5/8! How long are your crank arms?
 

SDG

Chimp
May 24, 2007
76
0
Hey, this is my frends Trailking and we have slammed the chainstay down to 14,5" by grinding the gussets a bit. As you can see it's with 26" and he runs Maxxis - Holyroller 26"x2.2. The tire clearence is very minimal, like 3 a 4mm.

For the storie about being unstable it's not true, this bike is very stable on the big dirts and with speed. I Think the unstableness is more a combination of chainstay and wheelbase, the shorter the wheelbase, the more unstable the bike gets with speed. The headtube angle is allso a big influence for the stable feel of a bike.

 

sealclubber

Monkey
Nov 21, 2007
544
0
damn i want/need a trailking frame. looks like over twice the distance from the back of the front wheel to where the pedal would be when level, as compared to my p1
 

Castle

Turbo Monkey
Jun 10, 2002
1,447
0
VA
. As you can see it's with 26" and he runs Maxxis - Holyroller 26"x2.2. The tire clearence is very minimal, like 3 a 4mm.

For the storie about being unstable it's not true, this bike is very stable on the big dirts and with speed. I Think the unstableness is more a combination of chainstay and wheelbase, the shorter the wheelbase, the more unstable the bike gets with speed. The headtube angle is allso a big influence for the stable feel of a bike.
I agree with that, as you can read above, I said if I could've lengthened the wheelbase/front to center it would've made it more stable, but just moving the wheel forward and back in stays does change the stability of the bike greatly....

and like woo and cru mentioned the b.b. heigth plays a huge factor too...

fork looks kinda tall and head angle pretty slack like you said for sure...

that's a pretty decent build.... cool bike...

edit: while your removing material, you could take some material off the drops to clean em up some....
 

BikeSATORI

Monkey
Apr 13, 2007
723
0
one world...
Hey SDG, it's interesting how that Trailking had to be ground on in order to slam the wheel with 26's... What exactly did you have to grind?


It seems pretty interesting how DH riders are all stressin' over high bb's and trying to get theirs all low like below 13, and here we are, all stressin' and trying to get ours up beyond that, hahaha...

I'd really like to try one of those TrailKings one of these days with the 13.3" bb height, sounds hoppy poppy. I bet you step off of that thing and go to get on anything else and it will feel like a sloth.


And Sir Crackien, most of the Trials bikes you speak of have no seattubes to worry about, and all cnc'ed junctions, therefore making tire clearance and chainstay length a somewhat simpler thing to deal with.... Not to mention, I'd assume most of them probably can't run a sprocket larger than 30t without hitting the wide yoke...
 

Sir_Crackien

Turbo Monkey
Feb 7, 2004
2,052
0
alex. va. usa.
yes and no on that point. yes they all use cnc yokes. have you seen the trailking yoke on my other thread??? its not just plate steel or pipes, it looks like a cast piece to me. also up until like 5 years ago all trials bike had seats (well for the most part) because comp rules required it. also a higher bb helps in the running of retardedly short chainstays. you are right on the sprocket size but that is only because they don't take sprocket bigger than 20t into account because of the way the bike it intended to be ridden. they could probably run a 32t if they tried to take that into account in the design.

not trying to create a battle or anything just giving my insight on the subject because i have owned more than one trials bike in the past.
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
yes and no on that point. yes they all use cnc yokes. have you seen the trailking yoke on my other thread??? its not just plate steel or pipes, it looks like a cast piece to me. also up until like 5 years ago all trials bike had seats (well for the most part) because comp rules required it. also a higher bb helps in the running of retardedly short chainstays. you are right on the sprocket size but that is only because they don't take sprocket bigger than 20t into account because of the way the bike it intended to be ridden. they could probably run a 32t if they tried to take that into account in the design.

not trying to create a battle or anything just giving my insight on the subject because i have owned more than one trials bike in the past.
All is true, yes (as I have been refining my trials bikes design for a month or two - I ride observed moto trials for anyone who knows what that is....) BUT - you also have to account for the fact that you all are running 128mm wide spindles. There are lots of factors that come into play... being as trials bikes are aluminum, it makes the process 100 times easier....
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
22,253
1,951
In my pants
It seems pretty interesting how DH riders are all stressin' over high bb's and trying to get theirs all low like below 13, and here we are, all stressin' and trying to get ours up beyond that, hahaha...
Like hell :D



Low bb = stable bike, regardless of the application.

I sold my evil DOC specifically because the BB was too high.
 

Sir_Crackien

Turbo Monkey
Feb 7, 2004
2,052
0
alex. va. usa.
A Grove just remember that the cog on trials bike are placed in the same location as the small ring in mtn bikes not the middle ring like bmx and pretty much all other bikes.

yes i know that bmx runs a narrower chain line than mtn but its not by much
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
Hey SDG, it's interesting how that Trailking had to be ground on in order to slam the wheel with 26's... What exactly did you have to grind?


It seems pretty interesting how DH riders are all stressin' over high bb's and trying to get theirs all low like below 13, and here we are, all stressin' and trying to get ours up beyond that, hahaha...

I'd really like to try one of those TrailKings one of these days with the 13.3" bb height, sounds hoppy poppy. I bet you step off of that thing and go to get on anything else and it will feel like a sloth.


And Sir Crackien, most of the Trials bikes you speak of have no seattubes to worry about, and all cnc'ed junctions, therefore making tire clearance and chainstay length a somewhat simpler thing to deal with.... Not to mention, I'd assume most of them probably can't run a sprocket larger than 30t without hitting the wide yoke...
I do believe he ground the slot in the stays? bec. they come stock at 14.75"

bulldog - what length frontend do you consider "long"
 

Bulldog

Turbo Monkey
Sep 11, 2001
1,009
0
Wisconsin
I do believe he ground the slot in the stays? bec. they come stock at 14.75"

bulldog - what length frontend do you consider "long"
FYI- Atomlab website specs 14.5-15.5" CS.

I consider "long" to be anything 23"+ as there just aren't more than a handful of frames that offer that length.

For building a frame I'd figure you to know the specs on all the offerings out there! ;)
 

Bulldog

Turbo Monkey
Sep 11, 2001
1,009
0
Wisconsin
Where are you all getting this 14.5 crap from?! it says 14.75 right on their webpage. Lookie > http://atomlab.com/frametrailking.html <

And if you want me to know the specs for all the offerings out there, how am I ever supposed to have time to actually build? I would be on the comp/phone all day everyday
Look at the picture! 14.5"! Granted the TT numbers in the pic don't match the spec list, which doesn't even match the production frames - but it's written right on that page.

And knowing your "competition" is probably the first step in developing a new product!
 

A Grove

Monkey
Nov 20, 2007
497
0
State College, PA
I understand what you;re saying. I can go out and make exactly what everyone else is making, but to sit there and study every other product would take forever and I wouldnt ever accomplish anything on the "product" end of the spectrum.

EDIT:: Thats really...odd whats going on with their webpage.