Custom Design/build Forks

[Rusevelt]

I wanna a 26in fork where the fork legs are perfectly straight and zero rake dropouts. other than Curtis and Leeson bikes, where can i have this done? ill only turn to Gary Woodward, and Clive Leeson as a last resort because the last time i mention this idea to them both, they both seemed against the idea and gave some technical bullshit reckoning that it cant be done. reason i want completely straight forks compared to standard raked forks is to improve the neutral balance feel specifically on uneven surfaces and working on some new frontwheel moves.

Edited January 13, 2008 by Rusevelt

[Christophe']

haha . got a slack hesadtube then?think about it

[psycholist]

Forks with no trail and a head tube that's not vertical will just make the tyre flap sideways as soon as you put weight on it (Think of what would happen if the head tube was horizontal to get an exaggerated idea of this effect). The fork offset has to be a certain amount (Depending in the head angle and wheel diameter) in order that the steering feels neutral or pulls towards the straight ahead position (Pulling slightly straight ahead is the usual default).

What you're really looking for is a fork with just the right amount of offset to balance the force trying to turn the wheel due to your weight and the head angle of the bike, with the straightening force created by the fork trail (The more fork trail the further the front of the bike has to lift in order to allow the wheel to turn from the straight ahead position.

Edited January 13, 2008 by psycholist

[Rusevelt]

I disagree. maybe i didnt explain myself constructively enough, so hear it goes . what i really want is zero fork rake offset from the headangle axis to completely neutralize any negative steering feedback when riding skinny-ish balance lines, trackstands on uneven surfaces, backwheel pivotting for sharp direction change with minimum correction hop, and progressive frontwheel moves. a good example of negative steering feedback is if you were to stand over your bike (feet on the floor and not pedals) holding the bars and bike straight, now if you turn the bars in a typical trackstand angle (frontwheel pointing at 2pm clockwise direction) and completely let go of the bike, the gyroscopic gravitational effect will make the bike roll forward slightly, tilt and fall to the left side. which why we must have our left pedal forward when counterbalancing for a trackstanding with the bars turned clockwise. and the same effect via-versa. a zero reake offset will have no negative steering feedback no matter how extreme you turn the bars because the wheel axle line remains in consistent axis with the headtube angle. another example is when you turn your bars clockwise, you have to lean your bike over to the right side to achieve optimum counterbalance. zero offset eliminates this negative effect completely. any finally the point you may about the tyre clearance, well you can always have slightly longer fork legs like the old Pace trials forks. Echo urbans have pretty big tyre clearance.

[Ali C]

I think your making a mountain out of a mole hill. If it was a well known problem then it would have been fixed before surly? I dont think the problem you are explaining isnt somthing that can be fixed by just riding and learning how to deal with it.

On the other hand, when frames were zero bb (or below) someone must have thought that was a problem and decided to raise the bb by a few mm, people might have said he was crazy but it turned out to be a good step forward.

I still think your trying to fix somthing thats not broken, but good luck finding someone to make a fork and I am sure we will all be interested in the outcome.

[Ash-Kennard]

make your own fork?

[psycholist]

What you're describing is what I've just said won't work unless you've got a vertical headtube. The further you turn the front wheel the more the tyre contact patch moves along the tyre, so the fork offset doesn't stay constant with steering angle. this is part of the reason that in balancing a trackstand you can turn the front wheel more or less tightly rather than rocking the bike sideways for small adjustments. My Echo Control with Urban forks I think actually has the behaviour you're looking for I reckon. It's a fantastic trackstander, way less effort than the Pure on a Pashley fork I had before.

[Rusevelt]

I guess you represent the negative majority of those who dont like progressive CHANGE for the BETTER. Im guessing you slated the original Ashton frame for being seatless, and the original koxx vinco for being high bb. just remember the world will always move forward weather we like it, or in your case NOT!

[N.Wood]

So the 2 head honchos at both Curtis and Leeson both gave you the same 'technical bullshit'?

Are you sure you know more than they do? Considering the amount of time they've both been building forks, frames and other parts?

Try a local fabricator but i can assure you the time spent mincing around looking for your forks to be designed and made would be better off spent on a bike learning how to ride.

[psycholist]

I guess you represent the negative majority of those who dont like progressive CHANGE for the BETTER. Im guessing you slated the original Ashton frame for being seatless, and the original koxx vinco for being high bb. just remember the world will always move forward weather we like it, or in your case NOT!

Was this aimed at me? If so I don't think you understand what I'm saying. There's a reason for fork offset, it's necessary to give the bike the stability riders expect from it (Which is very little in the case of most trials bikes, but is a lot more than the inherently unstable arrangement you suggest). Inherently unstable geometry may not in itself be a bad thing, it works to improve maneuverability in fighter jets. The difference is they have lots of computers to maintain stability so the pilot can fly the plane as if it is stable. In a bicycle where there is no control system beyond the rider's input and the geometry choice itself, it will lead to serious weirdness. By all means spend the time and money making a zero offset fork (If I thought it was a good idea I'd try it too), but don't be surprised if the first time you take a hand off the bars while rolling along the bars don't snap sideways and throw you off.

If you want to try this (And definitely do, I think my understanding of the steering geometry of bicycles is pretty good, but an important part of being able to learn, argue and reason is being able to admit you're wrong (This would be why I have no respect for blind adherents to religion, as it works in exactly the opposite way to reasoned argument in that it gives you a set of beliefs that are inviolate, even when logical extensions from them are obviously ridiculous)). Best thing to do is buy some cheap steel forks and bend them manually until there's no offset (Do not kink the fork tube doing this though, they'll fail on their first test ride if this happens) - if you haven't the equipment to bend them handy, try a panel beater or your local bike shop. Try it and if you like it, get some custom made to the same geometry (And start selling).

And by the way, I really wanted an Ashton when they came out first, it made perfect sense to ditch the saddle on a trials bike, but didn't have the money. Raising the BB on trials bikes as well as shortening the chainstays is the main way I wanted to change my bike since approximately 1998... There are reasons which make sense to me behind these changes.

[AdamR28]

reason i want completely straight forks compared to standard raked forks is to improve the neutral balance feel

I think having zero offset might actually give the opposite effect you're trying to achieve... Turn your forks around and have a quick ride - obviously this would give ~-45mm offset but it would give you an idea of how the handling would change.

[Rusevelt]

Was this aimed at me? If so I don't think you understand what I'm saying. There's a reason for fork offset, it's necessary to give the bike the stability riders expect from it (Which is very little in the case of most trials bikes, but is a lot more than the inherently unstable arrangement you suggest). Inherently unstable geometry may not in itself be a bad thing, it works to improve maneuverability in fighter jets. The difference is they have lots of computers to maintain stability so the pilot can fly the plane as if it is stable. In a bicycle where there is no control system beyond the rider's input and the geometry choice itself, it will lead to serious weirdness. By all means spend the time and money making a zero offset fork (If I thought it was a good idea I'd try it too), but don't be surprised if the first time you take a hand off the bars while rolling along the bars don't snap sideways and throw you off.

If you want to try this (And definitely do, I think my understanding of the steering geometry of bicycles is pretty good, but an important part of being able to learn, argue and reason is being able to admit you're wrong (This would be why I have no respect for blind adherents to religion, as it works in exactly the opposite way to reasoned argument in that it gives you a set of beliefs that are inviolate, even when logical extensions from them are obviously ridiculous)). Best thing to do is buy some cheap steel forks and bend them manually until there's no offset (Do not kink the fork tube doing this though, they'll fail on their first test ride if this happens) - if you haven't the equipment to bend them handy, try a panel beater or your local bike shop. Try it and if you like it, get some custom made to the same geometry (And start selling).

And by the way, I really wanted an Ashton when they came out first, it made perfect sense to ditch the saddle on a trials bike, but didn't have the money. Raising the BB on trials bikes as well as shortening the chainstays is the main way I wanted to change my bike since approximately 1998... There are reasons which make sense to me behind these changes.

Nah, sorry dude, those comments were directly aimed at Ali.C. cant explain how my comments came directly under yours. by the way your comments maybe correct but unnessary....lets face people why is everyone making a big fuss because i wanna try some different. i only what straight forks and virtually everyone wants to give me the third degree!

[Rusevelt]

I think having zero offset might actually give the opposite effect you're trying to achieve... Turn your forks around and have a quick ride - obviously this would give ~-45mm offset but it would give you an idea of how the handling would change.

yeah i tried that which is what gave me the idea in the first place about enquring custom straight forks. when you turn the bars 180 degrees, the headangle becomes slacker (though feels way quicker) because of the offset in the forks. im not interested in the behaviour of the forks in that manor, im interested in how in the forks behave with simular geometry feel to bmx flatland forks which is what started this whole can of worms in the first place.

[Ali C]

I guess you represent the negative majority of those who dont like progressive CHANGE for the BETTER. Im guessing you slated the original Ashton frame for being seatless, and the original koxx vinco for being high bb. just remember the world will always move forward weather we like it, or in your case NOT!

eh, how did I deserve that? I wished you good luck in finding a zero rake fork and I want to know how it will feel. Although I am preeeeeety sure I wont be wanting one

[sidehop]

^^ I am with Ali, 1 he didnt deserve that...

and 2. Do what you want but i think you wont be very happy with the outcome

[Simpson]

Weld some shitty suspension forks? they have 0 rake right? i dunno.... bet it would feel gash though

[Tom_]

Weld some shitty suspension forks? they have 0 rake right? i dunno.... bet it would feel gash though

the crowns are like made forward so the legs are pushed forward sorta, so they have rake. I think, if that makes any sense atall.

[psycholist]

Bending some cheap forks is the best way to prototype this idea. You'll get a second hand cheap steel fork for less than a tenner in most shops. If you like it worry about building something that's actually up to trials use then. It will also allow you to try different fork offset levels as there is an optimum for a given headtube angle, stability requirement and wheel diameter. Could you try flatland forks in a mod?

[CurtisRider]

Could you try flatland forks in a mod?

bmx forks are considerably shorter than mod forks, mod forks are quite close to stock length

i would personally make my own forks, it's not overly hard to do if you have an ounce of skill, admittedly they wont last like professionally made jobbies if you are inexperienced but at least they will last long enough for you to get a good idea of what you are looking for. Personally i don't think you will get the desired effect (not in such a positive way anyway), but its always good to see somebody trying i guess