Re: [CR]Front Center Dimentions/Epic Ride with JB


Date: Sun, 8 Jun 2003 16:31:43 -0700 (PDT)
From: David Feldman <feldmanbike@yahoo.com>
Subject: Re: [CR]Front Center Dimentions/Epic Ride with JB
To: rocklube@adnc.com, classicrendezvous@bikelist.org
In-Reply-To: <3EE3B1BE.4764@adnc.com>


What? You mean you'd tolerate clip overlap to avoid the minor annoyance of a bicycle that steers like a
Harley hog? ;)
David Feldman
Vancouver, WA


--- Brian Baylis wrote:


> Dear friends,
>
> To preface this piece let it be known that I ride
> about a 50cm c-t frame
> most of the time. I have owned LOTS of classic bikes
> my size and built
> over 30 for myself over the years. One thing I know.
> I know what I like
> and I know what works for me. I have conducted many
> experiments for the
> purposes of learning more and understanding what I
> experience. To be
> perfectly honest, I normally chuckle during many of
> these discussions
> where people are citing formulas and scienticic
> theories to explain or
> justify why a bike works or doesn't work. I have
> learned what I know
> from PERSONAL EXPERIENCE which means much more to me
> than every "system"
> and "philosophy" or "formula" I've ever encountered.
> Every one of the
> systems has exceptions to the "rules" that only
> experience can properly
> translate into a perfectly fit and useful bike
> frame. Small frames are
> particulary effected by these variations. Building a
> frame starting from
> a dimention (front center) that isn't directly
> related to the rider and
> intended use of the bike is backwards in my opinion.
> Wheelbase, bottom
> head angle, trail and other "resulting" dimentions
> should not be used as
> the standards; especially if the framebuilder
> actually knows how to
> design a frame that fits and performs to
> specifications, or better yet,
> beyond the expectations of the owner. That is my
> goal.
>
> As far as I can tell, building to a front center is
> solely for the
> purpose of "creating" toe clip clearance. I can
> think of no other reason
> to start there. If someone else knows more about
> what else might be the
> purpose of starting with a front center standard,
> I'd be interested to
> hear it. I understand about "setback", but the
> bottom line is it still
> comes out as being a specific seat angle. Why not
> just determine the
> proper seat angle and be done with it. I have
> noticed that most of the
> builders who work to a front center tend to be
> building
> "semi-production" type frames as opposed to "true
> custom" frames by my
> deffinition. Also they tend to work from something
> other than a full
> scale drawing. What they may not know is that the
> drawing has numerous
> uses that tell the sensitive builder subtle things
> that the "OUIJA
> BOARD" systems cannot account for. Doesn't matter
> particularly unless
> one is really going completely custom from the
> ground up. To explain
> further would take a lot of time, but trust me this
> is true.
>
> In order for a small frame to reach the front center
> dimention it is
> common to do several things. Increase seat angle,
> decrease head angle,
> add fork rake, and sometimes lengthen top tube and
> or raise BB height a
> bit. On a small frame I believe I cannot feel the
> difference between a
> BB height of 10 1/4" as opposed to 10 3/8", so I
> don't get too up tight
> about a slightly higher BB on a small frame. All of
> the other
> compromises DO have an adverse effect on how the
> bike fits or steeres to
> some degree or another. The steering suffers the
> most. For me this is
> unacceptable. I cannot stand the feel of bikes built
> that way for
> myself. It drives me nuts and really detracts from
> the pleasure of my
> cycling experiences. Perhaps others like that feel,
> but I can't imagine
> why. It is unneccessary and annoying in addition to
> being unstable by my
> deffinition (for those who like to redefine common
> terms they will call
> it the opposite of what it is).
>
> Having over 30 years experinece with toe clip
> overlap I have to
> enlighten those who insist on eliminating it. For
> starters, as a true
> custom framebuilder one must discuss these matters
> at length with the
> customer. If the customer insists on compromises to
> accomplish
> clearance, I pass on them. I know they will find
> someone who will
> accomodate them. If it's an issue then 650c wheels
> are the perfect
> solution; if they can't go that route and trust my
> experience with these
> bikes, they're obviously in the wrong place. I don't
> try to accomodate
> that, I don't need to. The customer will suffer and
> most likely never
> know otherwise, so why worry. There are plenty of
> people who do come
> here for exactly the reason that I know what I'm
> doing and why.
>
> The only time one even has to consider overlap is
> while making VERY
> sharp turns at under about 5mph. Exactly how much
> riding does one do
> like that? A little attention if starting up from a
> stop (like maybe
> make the bike go straight instead of sideways) and
> there is nothing to
> think about. Cycling is a potentially dangerous
> activity. One should be
> competent to ride a bike. It is a sophisticated
> piece of sports
> equiptment at this level anyway. Something as simple
> as that should not
> rob the bike of it's potential to perform to
> accomodate such a non-issue
> in my opinion. If you can't handle toe overlap of a
> reasonable amount
> you've got no chance against road hazards, cars,
> potholes, other
> Jabonies who can't handle a bike, and hundreds of
> other things. Does any
> of this make sense? It does to me. My personal
> experience has shown me
> that relatively speaking it is foolish to design a
> bike to meet a front
> center dimention. Just my opinion.
>
> So what happens if you go the other route? Well, you
> start with the
> rider and the intended use for the bike. I'm not
> even going to try to
> explain how I go about determining what to build.
> It's all in my head
> and comes from experience. There is no formula.
> Every bike and every
> rider is different. Plugging numbers into a computer
> program never did
> it for me. You use that if you don't know how to
> think and reason for
> yourself and apply EVERYTHING you've ever learned
> about building frames
> in every single bike. Sorry if that offends the
> technical types. It's
> nothing personal, it's just the way I operate.
> Applied knowledge,
> period. No book forthcomming, for obvious reasons. I
> cannot pass what I
> know on. I will die with it, sorry.
>
> I begin with the seat angle. Once I have established
> that I determine
> the top tube length/stem length combination. The
> actual frame size can
> vary a lot more than most people are willing to
> accept from my
> experience. Frame size has to do partially with
> position on the bike
> relative to several other factors in the design. As
> a custom builder, I
> don't just build racing style bikes. Bikes for
> different purposes can be
> different sizes for the same rider, but I find most
> people are too rigid
> in their belief of what "frame size" they take. The
> rest of the frame
> design isn't related to the ride as much, but have
> to do with weight
> distribution, fit, steering qualities, how the bike
> handles the gearing,
> etc., etc.. It's not rocket science really, but
> knowledge and common
> sense are very important. Otherwise you have to rely
> on formulas and
> whatnot. (There's that word again, what the hell is
> "whatnot" anyway?) I
> determine each of these dimentions based on the
> conditions the bike will
> === message truncated ===