From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Good  Tires
Date: 1 Dec 1998 01:58:39 GMT

Mark J Boyd writes:

> While I quite agree with Nick about wider tires and even about using
> them on narrow rims - I have 700x32 tires on MA2 rims on my touring
> bike - some (many?) bikes will not have a wide enough space between
> the chainstays to fit wider tires.

Not to mention that the brakes currently offered won't take a larger
tire either thanks to the fashion of "tight" and therefore, more rigid
frames...BS.  If riders would stop riding on spaghetti sized tires in
the image of, "I'm so fast I need all these gimmicks", people who
actually ride bicycles could walk into a store and get a bicycle that
whose frame will accept a reasonable tires, have clearance for a
little snow or dirt on the tire and have enough clearance between seat
tube and rear wheel to not get a finger jammed in there when lifting
the bicycle.  A few years ago, losing a fingernail from "wiping" a
rear tire would have been laughed at.  Today road bicycles are all
that short.

Fork crowns on road bicycles today are an insult to anyone who rides
in anything but swept roads.  The Campagnolo Delta brake epitomized
that syndrome being so close to the tire that the arch of the brake is
scored by road grit picked up in the wet... and this with small tires.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: CHAIN stay length and handling, (sorry, i misspoke before)
Date: 7 Feb 2000 18:22:04 GMT

Craig Kozak writes:

> I was wondering how much difference in the length of CHAIN stays
> would be needed to feel a difference in handling?  For example, with
> all other things the same (e.g. materials and other geometry), would
> a 5 mm CHAIN stay difference really be felt by the rider?

For road bikes in the range that is available, the longer the
chainstays the better the bike handles in all but 10mph turns.  Tandem
riders can vouch for that on fast descents.  The trend toward short
bicycles is not handling related but rather a desire to build lighter
bicycles.  The concept is bolstered by the allusion to "quick"
steering and that the fastest bicycles are the TTT bikes, that
coincidentally depends on the riders being as close together as they
can get.  Hence short bicycles.  That doesn't mean the bicycle is
fast, only that a four man team is fast.

Chainstay length is primarily a comfort effect of sitting directly
over the rear wheel or not.  Secondarily, a short wheelbase makes
weight transfer on braking less advantageous and least of all steering
motions more disruptive to straight line riding.

The only thing wrong with long chainstays is that they are not in
fashion and your peers will sneer at you for being unconventional,
using all sorts of pseudo technical allusions to support their point
of view.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy failure
Date: 15 Jan 2001 21:53:56 GMT

Henrik Muenster writes:

>> I don't think you know what the dimensions of my frame are and what
>> effect that might have on your riding.

> From the photos it seems to be very large, much larger than standard
> frames, and yet you only have a little seat post showing. Don't get
> me wrong. I don't like the very small frames, that some riders use
> these days. I have a 62 cm c-c (63,5 c-t) frame to my 189 cm and
> around 90 cm inseam. My lbs thinks I should ride on a 60 cm c-t
> frame, and I have seen riders on even smaller frames.  I have always
> thought, that the amount of seat post showing should be somewhat
> proportional to the size of the frame.

I don't see the logic in the long seat post or one that is
proportional to frame size.  At the time I chose this frame size, the
seat post was long enough to have full engagement.  I've had the same
Campagnolo seat post for a long time and it doesn't have a lot of
spare length inside the frame although it has about 80-100mm
engagement.  I have a feeling that many riders have a fear of the top
tube and the farther away the better.  Fortunately I started riding
when these folks (old fuddy duddies) were not in charge.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy failure
Date: 17 Jan 2001 21:57:46 GMT

Henrik Muenster writes:

>> I don't see the logic in the long seat post or one that is
>> proportional to frame size.

> But what's the logic in choosing a frame which, as far as I can see,
> is larger than any standard size and putting the seat post almost
> all the way down?

I think you are looking at the bicycle differently than I do.  The
seat post has normal exposure, top the saddle being 190mm above the
centerline of the top tube and the centerline of the bars about 75mm
below the saddle.  Those are the dimensions that interest me.

> I'm asking out of curiosity and not trying to split hairs. Most
> people buy factory build frames, and they wouldn't be able to choose
> a frame fit like yours.  Even if you have the frame custom built, it
> might be necessary to order the tubes extra long.  What are the
> advantages of choosing a frame so large, that the seat post is all
> the way down?  Being able to keep the handlebar high?

Well now that you ask, I got into this because my Italian frames were
too short in the chainstays and I was raising the front wheel while
climbing seated in the Alps.  I also found myself bending over farther
than I wanted on the standard frames.  Besides that, I had too much
chainwheel drag when climbing hard so I designed a frame with long
chainstays 445mm and a laterally reinforced seat-tube-BB junction.
While I was at it, I also used a 32mm dia down tube and a 28.6mm dia
top tube to reduce frame flex and shimmy.  This achieved the desired
improvements over my previous smaller standard production frames.  One
of these was made by Tom Ritchey and the one I ride now by Peter
Johnson.  They met my expectations.

>> At the time I chose this frame size, the seat post was long enough
>> to have full engagement.  I've had the same Campagnolo seat post
>> for a long time and it doesn't have a lot of spare length inside
>> the frame although it has about 80-100mm engagement.

> Sorry, but I don't understand. Maybe my English isn't good enough.
> What is "full engagement"? Is that when the seat post is all the way
> down? Are you saying, that you have a short seat post, which can't
> come up very much?

There are folks who think 30mm of seat post engagement in the frame is
enough.  I don't, just as I don't believe in radial spoking on
conventional hubs.  Such marginal designs have a high probability of
failure, especially on my bicycle where things tend to break more than
what seems to be the norm.  I ride a lot and descend fast on rough
pavement, which is probably more stressful for a frame than dirt roads
are with soft fat tires.

>> I have a feeling that many riders have a fear of the top tube and the
>> farther away the better.  Fortunately I started riding when these
>> (folks old fuddy duddies) were not in charge.

> I agree with you, that a lot of people choose too small frames, and
> my frame is also larger than most would choose.  I just think, that
> you have gone far in the other direction.  Since I respect your
> knowledge about bicycles deeply, and I have learnt a lot from your
> posting here and from The Bicycle Wheel, I wanted to hear your
> opinion about frame sizing.  Perhaps I could learn something new.

Since I was a youth I've heard the fear of smashing into the bar stem
on collision, causing serious injury to the groin.  I also know of
many collisions, including my own, in which the rider went over the
front, never coming close to such an injury because the bicycle
launches the rider up and over.  Just the same, the specter looms
ominously for many theoretical bicyclists as do many other old wive's
tales.  I am amazed how often I hear people make jokes of smashing the
testes on mens bicycles and even more appalled at the round of
laughter this evokes, even from bicyclists.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jobst.brandt@stanfordalumni.org
Subject: Re: Chain Stay Length
Newsgroups: rec.bicycles.tech
Message-ID: <3jTG9.52361$Ik.1440749@typhoon.sonic.net>
Date: Tue, 03 Dec 2002 00:56:31 GMT

Jennifer Donleavy writes:

> So my questions are -- how did you arrive at the feature of having
> long chainstays on your bicycle?  Does it improve comfort or fit?
> How about the rest of the design of your bicycle?  How did you
> arrive at its various dimensions?  Did you make controlled
> measurements that I can try too?  Is there some tradition of
> rational frame design that can be tapped into for my future custom
> bicycle?

I specified pedal clearance for my crank length (240mm - crank
length), the drop of BB center below wheel centers.  I gave the top
tube length that I have arrived upon by years of riding conventional
Italian (Cinelli) frames with what I find a useful stem length.  The
chainstays are as long as one can make from chainstay tubes available
at the time and the rest is up to the frame builder.  This has been
Tom Ritchey and Peter Johnson, two experts in my area, each of whom,
built a frame for me in the last 20 or more years.  They last a long
time... until I wreck one.  The Ritchey died in a cross drain on a
fire road that was too deep to jump out of.  Shortly after a temporary
repair to the wrinkled downtube I was hit by a car in front of my
house totaling the frame.

Jobst Brandt  <jobst.brandt@stanfordalumni.org>  Palo Alto CA