Dreaded Trail Question: How Much is not Enough?

In my opinion, it would make a difference, but how noticeable is hard
to say. What you don't say is how long the top tube is of the new
frame and that will factor into this as a change to the "front length"
of the bike. This is measured from a centerline of the BB axle to the
center of the headtube at the intersection of the top tube. If the new
frame is either less or more than the old one and to accomodate that
difference you go with a different length stem to adust for that, then
that difference will factor into the handling as well.

Generally speaking, from my own experiences, I find a longer stem to
make the bike more "twitchy" due to having more weight out front.

These can be subtle things that are sometimes hard to notice, but
nonetheless, there is a difference.

Greg

adiladub said:

in absolute terms, is 51.6mm of trail sufficient to produce a responsive but adequately stable ride for general, all-around cycling or is it getting into twitchy, unstable territory?

The best thing is to test ride the bike before buying. Sounds like the
new bike might be an eBay or mail order deal.

In any case, 51.6 mm of trail shouldn't be a problem. That's more than
2 inches which used to be the nominal value for trail.

My favorite bike (a 22 year old Italian frame with Columbus SL tubing)
has a 74.5 degree head angle and 45 mm of offset. That works out to
just 46 mm of trail. It's a 63 cm frame and it handles great.

There's more to handling than trail, but I don't think you'll have a
problem if all the other parameters are in the "normal" range.

Art Harris

Art Harris said:

My favorite bike (a 22 year old Italian frame with Columbus SL tubing)
has a 74.5 degree head angle and 45 mm of offset. That works out to
just 46 mm of trail. It's a 63 cm frame and it handles great.

There's more to handling than trail, but I don't think you'll have a
problem if all the other parameters are in the "normal" range.

I agree. Once upon a time I built a bike around a 27" wheel frame, a
24" "lightweight" fork, and 26" (ETRTO 559) wheels with slick tires.
The top tube sloped down about 7 or 8 degrees, which meant a 80 degree
head angle. That yielded a trail figure of less than half an inch.

Despite this, the bike was rideable- no hands, even. It'd shimmy above
about 25 mph, but it was a dandy around-town bike. The only real
problem was scraping pedals in mild corners- the bottom bracket was
somewhere south of 10".

The bike was stolen eventually. I wonder if the thief was able to ride
it away.

Jeff

In article <[email hidden]>,

adiladub said:

Well, after a lot of reading, I think I finally understand the whole "trail" concept and its effect on bike handling. Now I've got a question regarding how it applies in the real world.

My current bike is 58cm with 73.5 head tube angle and a fork with 43mm rake which, according to Anvil Bikes' trail calculator, produces 54.7 mm of trail. I'm looking at a bike with a 74 head tube angle and 43mm fork rake which produces 51.6 mm of trail.

What is the wheel radius? For a 350 mm radius I calculate
58 mm trail. For 340 mm radius: 56 mm trail.

Quoted message said:

I understand that, in theory, the handling of the new bike will be "quicker" and "less stable" because of the lower trail. My question, though, is will I experience a noticeable difference in real world riding? I'm not a "princess and the pea" kind of guy so I'm wondering if I could really feel the effect of a .5 degree change in HTA. Can 3mm of trail really make a tremendous difference in the way the bike handles? Just in case it is important, the wheelbase of the new bike is .4 cm longer than the current bike. Would this moderate any change in trail?

Second, in absolute terms, is 51.6mm of trail sufficient to produce a responsive but adequately stable ride for general, all-around cycling or is it getting into twitchy, unstable territory?

The shorter the fork offset the longer the trail. Smaller
fork offset typically means more sensitive steering.
Greater head tube angle typically means more sensitive
steering. So the relationship between trail and steering
sensitivity is a bit complicated. Better variables to
assess steering behavior are fork offset, and head tube
angle. Some recumbent bicycles are built with the trail
the negative of upright bicycle trail.

R: wheel radius
beta: head tube angle
B: fork offset
N: trail

R * cos beta - B
N = -------------------
sin beta

Please learn to post articles with your text lines shorter
than 80 characters.

--
Michael Press

In article
<[email hidden]>,

Greg said:

In my opinion, it would make a difference, but how noticeable is hard
to say. What you don't say is how long the top tube is of the new
frame and that will factor into this as a change to the "front length"
of the bike. This is measured from a centerline of the BB axle to the
center of the headtube at the intersection of the top tube. If the new
frame is either less or more than the old one and to accomodate that
difference you go with a different length stem to adust for that, then
that difference will factor into the handling as well.

Generally speaking, from my own experiences, I find a longer stem to
make the bike more "twitchy" due to having more weight out front.

These can be subtle things that are sometimes hard to notice, but
nonetheless, there is a difference.

How about quoting from the article you refer to?

--
Michael Press

Dans le message de
news:[email hidden],
Michael Press <[email hidden]> a réfléchi, et puis a déclaré :

Quoted message said:

In article
<[email hidden]>,

Greg said:

In my opinion, it would make a difference, but how noticeable is hard
to say. What you don't say is how long the top tube is of the new
frame and that will factor into this as a change to the "front
length" of the bike. This is measured from a centerline of the BB
axle to the center of the headtube at the intersection of the top
tube. If the new frame is either less or more than the old one and
to accomodate that difference you go with a different length stem to
adust for that, then that difference will factor into the handling
as well.

Generally speaking, from my own experiences, I find a longer stem to
make the bike more "twitchy" due to having more weight out front.

These can be subtle things that are sometimes hard to notice, but
nonetheless, there is a difference.

How about quoting from the article you refer to?

What are your writing about ?

Michael Press said:

How about quoting from the article you refer to?

--
Michael Press

In re-reading my own post, I don't see that I made reference to any
article.

I'm not sure that I am clear on exactly what it is that you are
wanting.

Greg

Michael Press said:

What is the wheel radius? For a 350 mm radius I calculate
58 mm trail. For 340 mm radius: 56 mm trail.

A typical 23 mm tire is more like 334 mm radius. For 74 degrees and 43
mm offset, I calculate 51.2 mm of trail.

Art Harris

Michael Press said:

What is the wheel radius? For a 350 mm radius I calculate
58 mm trail. For 340 mm radius: 56 mm trail.

I'm using the spreadsheet at anvilbikes.com. Its formula uses
a radius of 334 mm which, when you plug in 74 HTA, 43mm
rake and 25mm tire, gives a trail of 51.6.

Quoted message said:

Please learn to post articles with your text lines shorter
than 80 characters.

Sorry about that, I'm away from my computer and not using my
usual newsreader.

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adiladub said:

My current bike is 58cm with 73.5 head tube angle and a fork with
43mm rake which, according to Anvil Bikes' trail calculator, produces
54.7 mm of trail. I'm looking at a bike with a 74 head tube angle and
43mm fork rake which produces 51.6 mm of trail.

If you put a fork with 45 mm offset on your current bike, you'll get a
reasonable approximation of the feel of the new bike. Your trail will
drop by almost 2 mm and your wheelbase will increase by almost 2 mm.

Quoted message said:

I understand that, in theory, the handling of the new bike will be
"quicker" and "less stable" because of the lower trail. My question,
though, is will I experience a noticeable difference in real world
riding? I'm not a "princess and the pea" kind of guy so I'm wondering
if I could really feel the effect of a .5 degree change in HTA.

Quoted message said:

Just in case it is important, the wheelbase of the new bike
is .4 cm longer than the current bike. Would this moderate any change
in trail?

I haven't made such small changes in a bike, so my opinion is based on
experience with much larger changed in geometery. My opinion is probably
worth less than you paid for it. Here goes anyway...

I doubt you'd even notice if someone changed your trail and wheelbase in
the way you describe during a double-blind test. Maybe if the trail
*and* wheelbase were reduced (or vice versa) you'd notice a slight
change. Even changing one without changing the other may be hard to
notice. But changing one to twitchier and the other to more stable? I
really don't think you'll notice.

Quoted message said:

Can
3mm of trail really make a tremendous difference in the way the bike
handles?

I suppose it can, if the trail went from 10 mm to 7 mm. But I don't
think you'll be able to tell the difference between 55 and 52 mm,
especially with the accompanying change in wheelbase.

--
Dave
dvt at psu dot edu

feel 3mm ? probbbabbly. i went from a male fork to a female double top
tube frame fork from raleigh '83 and the woman's plus 1/8" stablized
the touring load handling.
recently, installed a 700c conti tt in front with a 27" pasela
panaracer at rear - waiting for the correct parts on the 700c rear -
and find there's a sensation of moving the steering axis toward the
seat and defining that axis as a sensory phenomena: the front wheel
doesn't feel like its leading the bike now, there's a sensation of the
bike turning around a point back on the top tube down to the BB!!
this is not uncomfortable at touring speeds
that front steering sensation press has - is press overweight?

that's greg not press
are the anvil calculators mathmatically reliable?
the anvil work is fascinating and thanks for bringing it up.
i copy frame spec for comparison - appalachin to gunnar whichreminds me
to find the BLT Gordon spec's
and am told via local horn that the story is a comparison of head tube
intersection angles?
gentlemen start your hobarts!!

In article
<[email hidden]>,

Art Harris said:

Michael Press said:

What is the wheel radius? For a 350 mm radius I calculate
58 mm trail. For 340 mm radius: 56 mm trail.

A typical 23 mm tire is more like 334 mm radius. For 74 degrees and 43
mm offset, I calculate 51.2 mm of trail.

Does not look like the OP gave tire dimensions. On the
bicycle an Avocet slick 622 x 25 measured out to 340 mm.
Larger tires get above 350 mm.

--
Michael Press

Greg said:

Michael Press said:

How about quoting from the article you refer to?

--
Michael Press

In re-reading my own post, I don't see that I made reference to any
article.

I'm not sure that I am clear on exactly what it is that you are
wanting.

They're asking, fairly rudely, for you to quote the article you are replying to.

Ron

In article <[email hidden]>,

RonSonic said:

Greg said:

Michael Press said:

How about quoting from the article you refer to?

--
Michael Press

In re-reading my own post, I don't see that I made reference to any
article.

I'm not sure that I am clear on exactly what it is that you are
wanting.

They're asking, fairly rudely, for you to quote the article you are replying to.

Note that some of my first article was excised without
comment in Greg's reply to it.

--
Michael Press

In article <[email hidden]>,

adiladub said:

Well, after a lot of reading, I think I finally understand the whole
"trail" concept and its effect on bike handling. Now I've got a
question regarding how it applies in the real world.

My current bike is 58cm with 73.5 head tube angle and a fork with
43mm rake which, according to Anvil Bikes' trail calculator, produces
54.7 mm of trail. I'm looking at a bike with a 74 head tube angle and
43mm fork rake which produces 51.6 mm of trail.

The overall radius of the wheel is also something that has to be taken
into account. Frame size makes no difference. Trail will change, all
other things being the same, with different tire sizes. Your bike with
700 x 19s and with 700 x 32 will have a difference in trail and feel.

Quoted message said:

I understand that, in theory, the handling of the new bike will be
"quicker" and "less stable" because of the lower trail.

Not necessarily. There are other factors in stability, such as
wheelbase, weight distribution front/rear, tire width, and tire
pressure. Ever noticed how the handling changes if the front tire gets
a slow leak and gets a little soft? Steering gets slower feeling, until
the tire is mushy enough to really draw your attention to it.

Quoted message said:

My question, though, is will I experience a noticeable difference in
real world riding? I'm not a "princess and the pea" kind of guy so
I'm wondering if I could really feel the effect of a .5 degree change
in HTA. Can 3mm of trail really make a tremendous difference in the
way the bike handles? Just in case it is important, the wheelbase of
the new bike is .4 cm longer than the current bike. Would this
moderate any change in trail?

Second, in absolute terms, is 51.6mm of trail sufficient to produce a
responsive but adequately stable ride for general, all-around cycling
or is it getting into twitchy, unstable territory?

There are bikes with 30 mm of trail that are quite ridable, albeit with
typically wider, lower pressure tires.

Part of the problem in this discussion is the subjectivity involved.
What's "more responsive?" More responsive to what? To leaning the
bike? To turning the bars? To road inputs? How stable is too stable,
and not stable enough? For what purposes?

"Normal" trail seems to be between 50 and 60 mm. Yet many bikes were
made with 73-74 degree head tubes and 50-60 mm fork offset, resulting in
very low trail figures. And yet those bikes were prized for the ability
to ride right down the fog line for hours at night, even though
conventional wisdom suggests that they should have been very unstable.

Michael Press said:

In article <[email hidden]>,

RonSonic said:

Greg said:

Michael Press wrote:
>
> How about quoting from the article you refer to?
>
> --
> Michael Press

In re-reading my own post, I don't see that I made reference to any
article.

I'm not sure that I am clear on exactly what it is that you are
wanting.

They're asking, fairly rudely, for you to quote the article you are replying to.

Note that some of my first article was excised without
comment in Greg's reply to it.

--
Michael Press

Noted.

"Tim McNamara" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Part of the problem in this discussion is the subjectivity involved.
What's "more responsive?" More responsive to what? To leaning the
bike? To turning the bars? To road inputs? How stable is too
stable,
and not stable enough? For what purposes?

"Normal" trail seems to be between 50 and 60 mm. Yet many bikes
were
made with 73-74 degree head tubes and 50-60 mm fork offset,
resulting in
very low trail figures. And yet those bikes were prized for the
ability
to ride right down the fog line for hours at night, even though
conventional wisdom suggests that they should have been very
unstable.

Tim, your first paragraph exactly captures the complications I've
always found. I'm always more concerned about the bike's resistance
to road and wind inputs, and my non-steering motions like downtube
gear shifting and butt scratching. I usually adapt to faster or
slower steering response very quickly, and can no-hand if the frame,
fork, and wheels are aligned with a good headset, so those factors are
not usually problems.

Thanks for framing the question well!

Ken Freeman
Ann Arbor, MI