Fixed gear/track frame geometry

Michael Press said:

I notice that the Cannondale and Fuji track bikes have
74.5 head tube and 73 or 72.5 seat tube angles. Why so
steep head tube angles? Is that preferred for actual
velodrome riding for some reason, perhaps sprinting?

Track racers really don't turn the bars- riding on a
steeply banked velodrome, you basically keep riding in a
straight line all the way around the track. Track bikes
tend to have steep head tubes and seat tubes (75/75 is not
all that unusual in a track bike) and very little fork
offset (sometimes called rake), giving them a fairly large
trail. My track bike is exceptionally easy to ride no-
handed as a result.

The position on a track bike is not really intended for
comfort, as few events last longer than a few minutes- a 50
or 75 lap points race being about as long as track events
get which is under 20 km and will last at most about 20-25
minutes. At least until you get to 6 day events and such,
but it's not likely that any of us will be doing that.

Quoted message said:

Any suggestions on frame size (I ride 57 and 58 cm road
bikes now) - any reason to step down in frame size like
you do on a cyclocross frame?

No. Same as your road bike (I also think that since most
people are riding undersized road bikes, they may as well
use the same size for 'cross).

My advice is to test ride and see what you're the most
comfortable riding. If you're riding this on the road, then
a more road-like seat tube angle will probably help you find
a comfortable position for longer rides.

Tim McNamara said:

Track racers really don't turn the bars- riding on a
steeply banked velodrome, you basically keep riding in a
straight line all the way around the track. Track bikes
tend to have steep head tubes and seat tubes (75/75 is not
all that unusual in a track bike) and very little fork
offset (sometimes called rake), giving them a fairly large
trail. My track bike is exceptionally easy to ride no-
handed as a result.

Is there an (a?) FAQ somewhere that discusses the
definitions of rake, trail, and other such parameters,
and their effects to the user? (And if not, there
should be one!)

--
Benjamin Lewis

A small, but vocal, contingent even argues that tin is
superior, but they are held by most to be the lunatic fringe
of Foil Deflector Beanie science.

Benjamin Lewis <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Is there an (a?) FAQ somewhere that discusses the
definitions of rake, trail, and other such parameters,
and their effects to the user? (And if not, there should
be one!)

"Rake" means different things to bicycle and motorcycle
people. "Trail" is the distance from the intersection of the
steering axis to the center of the contact patch of the
tire. These dimensions and their interactions are the
subject of at least one upper level engineering course:
calpoly.edu~wpattersOpen ↗ and the subject of much
debate. I doubt they can be reduced to a FAQ.

Jeff Wills

Jeff Wills said:

Benjamin Lewis said:

Is there an (a?) FAQ somewhere that discusses the
definitions of rake, trail, and other such parameters,
and their effects to the user? (And if not, there should
be one!)

"Rake" means different things to bicycle and motorcycle
people. "Trail" is the distance from the intersection of
the steering axis to the center of the contact patch of
the tire. These dimensions and their interactions are the
subject of at least one upper level engineering course:
calpoly.edu~wpattersOpen ↗ and the subject of much
debate. I doubt they can be reduced to a FAQ.

I'd be satisfied with a lengthy discourse, too 🙂

Ideally I'd like to learn more about this without leaving my
seat, but if anyone can suggest any good books on the
subject that might be available in the library I'd
appreciate that too.

--
Benjamin Lewis

Although the moon is smaller than the earth, it is
farther away.

--On Sunday, June 06, 2004 12:57 PM -0700 Benjamin Lewis

Quoted message said:

Ideally I'd like to learn more about this without leaving
my seat, but if anyone can suggest any good books on the
subject that might be available in the library I'd
appreciate that too.

Fundamentals of Vehicle Dynamics, by Thomas D. Gillespie

I'm not sure this covers bikes and motorcycles, but its a
good resource anyway. a good engineering library (such as
one at a university) should have a copy.

Mike Mechanical Engineering 2006, Carnegie Mellon University
Remove nospam to reply.

Quoted message said:

--On Sunday, June 06, 2004 12:57 PM -0700 Benjamin Lewis

Quoted message said:

Ideally I'd like to learn more about this without leaving
my seat, but if anyone can suggest any good books on the
subject that might be available in the library I'd
appreciate that too.

Fundamentals of Vehicle Dynamics, by Thomas D. Gillespie

I'm not sure this covers bikes and motorcycles, but its a
good resource anyway. a good engineering library (such as
one at a university) should have a copy.

Thanks. It's not at my university library, but there's a
copy at another nearby university, so I may check it out
if I can't find something more convenient or bicycle
specific. I also see a couple of books in our library with
promising titles.

--
Benjamin Lewis

Although the moon is smaller than the earth, it is
farther away.

Benjamin Lewis said:

Quoted message said:

Quoted message said:

Is there an (a?) FAQ somewhere that discusses the
definitions of rake, trail, and other such parameters,
and their effects to the user? (And if not, there should
be one!)

Look up "Trail" in my Bicycle Glossary, there's a link to a
good article on this.

Sheldon "sheldonbrown.comglossaryOpen ↗" Brown +----------------------------------------------------------
-----------+
| Check out the Shostakovich 24 Preludes & Fugues for
| Piano, Op. 87. | Sort of like "Das Wohltemperierte
| Klavier" on drugs. Way cool! |
+-----------------------------------------------------------
----------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-
find parts shipped Worldwide captainbike.comcaptainbike.comOpen ↗
sheldonbrown.comsheldonbrown.comOpen ↗

(Phil Brown) said:

Quoted message said:

Quoted message said:

Track racers really don't turn the bars- riding on a
steeply banked velodrome, you basically keep riding in a
straight line all the way around the track.

That's not really true. Yo do have to steer a track bike,
just not much. The trick is to drop your inside elbow as
you enter the turn, giving you a bit of steering. Works on
the road, too.

Having put in thousands of laps on the NSC velodrome in
Blaine MN, I'll beg to differ with you.

Sheldon Brown said:

Benjamin Lewis said:

Quoted message said:

> Is there an (a?) FAQ somewhere that discusses the
> definitions of rake, trail, and other such parameters,
> and their effects to the user? (And if not, there
> should be one!)

Look up "Trail" in my Bicycle Glossary, there's a link to
a good article on this.

Thanks. That's a good start, but it seems a bit simplified.
For example, I imagine if two bicycles have the same trail
but different head tube angles, they will handle
differently. I've also tried out a couple chopper style
bikes that had such extreme head tube angles that there was
a very noticeable drop in the front end whenever the
handlebars were turned.

--
Benjamin Lewis

All what we got here is American made. It's a little bit
cheesy, but it's nicely displayed. -- FZ

In article <[email hidden]>, Michael Press

Quoted message said:

I'm starting to research buying a new bike to indulge my
newfound fixed gear addiction. (My existing fixie is my
'88 Miyata road bike with tri geometry, a way too short
top tube, worn out drivetrain parts and a hack of a fixie
hub - epoxied freewheel. It'll cost enough money to get
the fit and parts right that I'd rather start new). Price
isn't an issue.

I assumed I'd want a frame with similar geometry to my
road bikes,
73/73. I notice that the Cannondale and Fuji track bikes
have 74.5 head tube and 73 or 72.5 seat tube
angles. Why so steep head tube angles? Is that
preferred for actual velodrome riding for some
reason, perhaps sprinting? The top tubes are still
longish, 57cm for the 56 cm Cannondale frame.

Any suggestions on frame size (I ride 57 and 58 cm road
bikes now) - any reason to step down in frame size like
you do on a cyclocross frame?

BTW, my favorite bike is my aluminum Cannondale road bike
with Spinergy Spox wheels - I love the stiff frame, and
the composite spokes dampen the road shock. My ideal new
fixie would be a regular new Cannondale road frame with
Spox wheels with the freehub replaced with the Surly
cassette hub converter, except that the regular road
frames have vertical dropouts. I'd consider the road frame
with the White eccentric hub to solve the dropout problem,
but seems like at that point I might as well get the track
frame. That brings me back to the geometry issue I asked
about above....

Thanks, Michael

Here's a couple of coppers.... I've had several frames
that at one time or another have been built up as fixies.
All fall between 56 to 58 cm in size. One was an older
MTB frame, the others; various road frames. Among the
roadies: a tourer with 45 cm chainstays and several road
frames sporting more or less typical racing head and seat
tube angles.

I loved 'em all for different reasons. Fixie A with the
short wheelbase had sprint bull horn bars and was a delight
in tight city traffic and corners. Fixie B (the tourer) had
drop bars, Brook's saddle, 28c tires with full fenders and
an upright seating posture; it's comfort was unsurpassed on
100+ km rides.... The purpose for which I built the bikes
(riding Doh! ;-) was integral in determining the suitability
of the frame used. It also influenced the choice of
secondary components and their setup; stems, tires,
handlebars... These also dramatically alter the ride
characteristics of bike.

No news there. But it's good to remember that there's a
symbiotic relationship between frame geometry and the
handling characteristics of the bike. So consider the frame
geo but, more importantly, also think over in what capacity
the fixie will be used; commuting, velodrome racing etc,
short recreational rides.... This should be the key factor.

If you intend it for general road use then (apart from
geometry) consider the following

- will the frame build up without toe touch?
- does it allow for a wide range of tires (> 23c)
- Is the fork crown drilled for a front brake
- what's the spacing of the rear DOs etc...

You love the feel of your Cannondale. Start from a
simmilar frame and keep in mind the type of riding
proposed for the fixie.

luke

Benjamin Lewis said:

Quoted message said:

--On Sunday, June 06, 2004 12:57 PM -0700 Benjamin Lewis

Quoted message said:

Ideally I'd like to learn more about this without
leaving my seat, but if anyone can suggest any good
books on the subject that might be available in the
library I'd appreciate that too.

Fundamentals of Vehicle Dynamics, by Thomas D. Gillespie

I'm not sure this covers bikes and motorcycles, but its a
good resource anyway. a good engineering library (such as
one at a university) should have a copy.

Thanks. It's not at my university library, but there's a
copy at another nearby university, so I may check it out
if I can't find something more convenient or bicycle
specific. I also see a couple of books in our library with
promising titles.

Bicycling Science by Whitt and Wilson, which has been
recently revised with a new edition by Jim Papadopolous
(former r.b.t contributor) and David Wilson. I'd look for
the new version, the old version is quite out of date and
according to some of the engineers in this newsgroup had
some serious errors. Haven't seen the new version yet. There
is a pretty comprehensive discussion of steering geometry in
the old version which seems fairly accurate.

(Phil Brown) said:

Quoted message said:

Having put in thousands of laps on the NSC velodrome in
Blaine MN, I'll beg to differ with you.

My track teacher/coach, Rick Denman at the Olympic
Velodrome in Carson, now sadly gone, tought me that trick
and I can tell you it works.

I know the trick you mean, it's just that a steeply banked
track is practically a straight line all the way around; the
steering required is very very minimal compared to cornering
on a flat surface. Indeed on a steep track like Blaine, you
have to lean the bike away from the track surface to avoid
hitting the uptrack pedal.

David L. Johnson said:

I was riding with a guy today, and he was talking about my
bike, and said that, well, with that geometry you
certainly can't ride no-hands. So, I did, just to show
him. That bike, even with the steeper angles, has always
handled like a dream.

heh, my track bike is also in the 74-75 degree range, can
easily be ridden no-handed and handles pretty well. it's
comfortable on long rides and altho i've never ridden a
century i've done dozens of metrics on it.

people worry too much. or quite possibly i'm a mutant.

Quoted message said:

Track bikes also have high bottom brackets, for an obvious
reason. That way they are less likely to drag a pedal on
the banking when riding slowly, or to do so on the road
cornering fast.

since i do most of my utility riding on a track bike, i've
gotten my reference for how much angle i can pedal through
from that bike which has led me to clip while pedaling
through turns on the other bike a few times. oops.

Quoted message said:

Some people want a slightly smaller track frame than road
frame, but this I think goes back to the days when road
frames tended to be bigger than they are today. Mine is
exactly the same size (seat and toptube) as my road bike.
I like the consistency. I also have the same seat and
bars, and same crank length, on both.

same frame size, same seat, similiar bars and smaller crank
length (165 v.
175) for me. the smaller length feels different but not so
much. not a big deal.
--
david reuteler [email hidden]

Tim McNamara said:

Bicycling Science by Whitt and Wilson, which has been
recently revised with a new edition by Jim Papadopolous
(former r.b.t contributor) and David Wilson. I'd look for
the new version, the old version is quite out of date and
according to some of the engineers in this newsgroup had
some serious errors. Haven't seen the new version yet.
There is a pretty comprehensive discussion of steering
geometry in the old version which seems fairly accurate.

Thanks. We have the old (2nd) edition in our library, so
I'll have a look at that first.

--
Benjamin Lewis

Basic Definitions of Science: If it's green or wiggles, it's
biology. If it stinks, it's chemistry. If it doesn't work,
it's physics.

David Reuteler said:

David L. Johnson said:

I was riding with a guy today, and he was talking about
my bike, and said that, well, with that geometry you
certainly can't ride no-hands. So, I did, just to show
him. That bike, even with the steeper angles, has always
handled like a dream.

heh, my track bike is also in the 74-75 degree range, can
easily be ridden no-handed and handles pretty well. it's
comfortable on long rides and altho i've never ridden a
century i've done dozens of metrics on it.

I just did a fairly hilly metric century on my track bike,
inspired by this thread, actually. (David will recognize the
roads- Gateway Trail to Oakdale, to Lake Elmo, through Afton
up to the park entrance, then 70th to Military Road and back
through downtown St. Paul along the Point Douglas Road path
to Shepard Road). I cheat a bit, though, and use an old
Bendix coaster brake hub (probably 50 years old) that I
built up into a wheel. Surprisingly smooth hub. Beautiful
day for a ride!

Quoted message said:

people worry too much. or quite possibly i'm a mutant.

Why can't both be true? ;-)

Quoted message said:

Quoted message said:

Some people want a slightly smaller track frame than road
frame, but this I think goes back to the days when road
frames tended to be bigger than they are today. Mine is
exactly the same size (seat and toptube) as my road bike.
I like the consistency. I also have the same seat and
bars, and same crank length, on both.

same frame size, same seat, similiar bars and smaller
crank length (165 v. 175) for me. the smaller length feels
different but not so much. not a big deal.

I don't notice that the 165s on the track bike make riding
any more difficult than the 175s I use on the rest of my
bikes. In fact, my knees seem to like them. Despite having
only a 67" gear up all the hills, some of which are
reasonably steep, my legs felt really good this morning.

Tim McNamara said:

I just did a fairly hilly metric century on my track bike,
inspired by this thread, actually. (David will recognize
the roads- Gateway Trail to Oakdale, to Lake Elmo,

...

Quoted message said:

through Afton up to the park entrance,

i know this as the "half way point of trail mix and yogurt
covered raisins." well, it is air conditioned. it is, in
fact, pretty hilly around there. i like biking around there
a lot .. 'specially on the wisconsin side of the saint croix
where it really gets hilly. i spent a fair bit of my
unemployment (time) there and on the gateway trail. sigh, i
miss the trees of minnesota a lot. a veritable endor you
have there.

Quoted message said:

Despite having only a 67" gear up all the hills, some of
which are reasonably steep, my legs felt really good this
morning.

i roped a coworker into an organized metric this weekend
(he raced back in the day so it wasn't too hard). [censored]
start at 8am, tho. aiiyy.. it looks to be fairly flat so
maybe i'll use the track bike -- i'm geared up a bit from
you at 74".

probably i should scout out the route, first? nahh..
--
david reuteler [email hidden]

Benjamin Lewis <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Quoted message said:

--On Sunday, June 06, 2004 12:57 PM -0700 Benjamin Lewis

Quoted message said:

Ideally I'd like to learn more about this without
leaving my seat, but if anyone can suggest any good
books on the subject that might be available in the
library I'd appreciate that too.

Fundamentals of Vehicle Dynamics, by Thomas D. Gillespie

I'm not sure this covers bikes and motorcycles, but its
a good resource anyway. a good engineering library (such
as one at a university) should have a copy.

Thanks. It's not at my university library, but there's a
copy at another nearby university, so I may check it out
if I can't find something more convenient or bicycle
specific. I also see a couple of books in our library with
promising titles.

Its described in Effective Cycling, the classic.

Tom

Thomas Reynolds said:

Benjamin Lewis said:

Quoted message said:

<[email hidden]> wrote:

> Ideally I'd like to learn more about this without
> leaving my seat, but if anyone can suggest any good
> books on the subject that might be available in the
> library I'd appreciate that too.

Fundamentals of Vehicle Dynamics, by Thomas D. Gillespie

I'm not sure this covers bikes and motorcycles, but its
a good resource anyway. a good engineering library (such
as one at a university) should have a copy.

Thanks. It's not at my university library, but there's a
copy at another nearby university, so I may check it out
if I can't find something more convenient or bicycle
specific. I also see a couple of books in our library
with promising titles.

Its described in Effective Cycling, the classic.

Is it? (goes and checks)

Hmm, some if not most of his description is dead wrong (e.g.
"A bicycle with long trail is very sensitive and follows
every lean you make"😉, and at best I find the rest
unhelpful.

I suspect Forester is confused about the effect of fork
offset (rake), and is under the common impression that
increasing rake increases the trail, when in fact the
opposite is true.

The best analysis I've found so far is the paper by David E.
H. Jones, "The Stability of the Bicycle", where he attempts
to build several "unrideable bicycles" (URBs). It's much
more rambling and casual than a typical academic paper, but
I found it somewhat enjoyable to read. I liked his closing
paragraph:

"It seems a lot of tortuous effort to produce in the end a
machine of absolutely no utility whatsoever, but that sets
me firmly in the mainstream of modern technology. At least I
will have no intention of foisting the product onto a long-
suffering public in the name of progress."

A scanned PDF version of the document can be obtained here:

socrates.berkeley.edubicycles.htmlOpen ↗

The book "Bicycling Science" to which Tim McNamara referred
me essentially summarizes Jones' analysis, at least in the
2nd edition.

--
Benjamin Lewis

Hey! I'm only fourteen, sickly 'n' thin Tried all of my life
just to grow me a chin It popped out once, but my dad pushed
it in. -- FZ

Benjamin Lewis said:

The best analysis I've found so far is the paper by David
E. H. Jones, "The Stability of the Bicycle", where he
attempts to build several "unrideable bicycles" (URBs).
It's much more rambling and casual than a typical academic
paper, but I found it somewhat enjoyable to read.

Have you seen the papers linked from:

tam.cornell.edubicycles.htmlOpen ↗

particularly Scott Hand's thesis, and Jim Papadopoulos'
summary of it?

James Thomson