to much trail?

My nephew bought a secondhand idworx Double D mtb (still damn expensive). Ofcourse I tried it, great
bike, great handling, massive tires, very light. But when I tried to open my jacket, riding with no
hands on the bar, I lost control. This surprised me since my nephew told me it has enourmes trail (I
looked it up 93mm!!). I can ride all my bikes with no hands, including a very twitchy peugot
racebike. I thought more trail ment easyer control. Is there such a thing as to much trail?

 

Trail is a speed dependent attribute; it kicks in usually in double digits. Slow speeds are more
affected by the gravity centering of most geometries. Too little fork offset for a given head angle
can produce massive trail but little or no gravity centering resulting in wheel flop at slow
speeds. Tom

--
Bruni Bicycles
"Where art meets science"
brunibicycles.com
410.426.3420
gvw <[email protected]> wrote in message
news:[email protected]...
> My nephew bought a secondhand idworx Double D mtb (still damn expensive).
> Ofcourse I tried it, great bike, great handling, massive tires, very
light.
> But when I tried to open my jacket, riding with no hands on the bar, I
> lost control.
> This surprised me since my nephew told me it has enourmes trail (I
> looked it up 93mm!!).
> I can ride all my bikes with no hands, including a very twitchy peugot
> racebike.
> I thought more trail ment easyer control.
> Is there such a thing as to much trail?

 

> My nephew bought a secondhand idworx Double D mtb (still damn expensive). Ofcourse I tried it,
> great bike, great handling, massive tires, very
light.
> But when I tried to open my jacket, riding with no hands on the bar, I lost control. This
> surprised me since my nephew told me it has enourmes trail (I looked it up 93mm!!). I can ride all
> my bikes with no hands, including a very twitchy peugot racebike. I thought more trail ment easyer
> control. Is there such a thing as to much trail?

I might be wrong here...but I believe that trail increases stability primarily at high speeds, while
actually decreasing it at low speeds. Must be some interaction between trail and the rotational
intertia of the front wheel vs. the vertical component of gravity pulling it in the direction of the
lean. I'd be interested to hear some real physics behind this phenomenon.

Kyle

 

gvw <[email protected]> wrote in message news:<[email protected]>...
> My nephew bought a secondhand idworx Double D mtb (still damn expensive). Ofcourse I tried it,
> great bike, great handling, massive tires, very light. But when I tried to open my jacket, riding
> with no hands on the bar, I lost control. This surprised me since my nephew told me it has
> enourmes trail (I looked it up 93mm!!). I can ride all my bikes with no hands, including a very
> twitchy peugot racebike. I thought more trail ment easyer control. Is there such a thing as to
> much trail?

Dear GVW,

Yes.

http://www.movie-poster.info/posters/387594.htm

Carl Fogel

 

gvw <[email protected]> writes:

> My nephew bought a secondhand idworx Double D mtb (still damn expensive). Ofcourse I tried it,
> great bike, great handling, massive tires, very light. But when I tried to open my jacket, riding
> with no hands on the bar, I lost control. This surprised me since my nephew told me it has
> enourmes trail (I looked it up 93mm!!).

Do you mean trail or fork rake (a.k.a. fork offset)? Trail is a geometric quantity that is
determined by head angle, fork rake and wheel diameter.

See http://www.sheldonbrown.com/gloss_tp-z.html and scroll down to "trail" and also read the
other links.

Trail is the distance from a vertical line drawn through the hub to the ground, which is the center
of the "contact patch" between the tire and the ground, and a line drawn through the center of the
head tube to the ground. Normally the vertical line through the center of the axle "trails" the line
drawn through the head tube. Draw this on a piece of paper, and then imagine what happens if you
leave everything the same but increase the fork rake: the trail decreases and hence the stability of
the bike decreases.

If your bike has 93 mm of trail, it will be so stable that it will be hard to ride. If it has 93 mm
of fork rake, then it's quite possible that it has little or no trail and is very unstable. For
certain types of trick riding this can be desirable.

> Is there such a thing as to much trail?

Well, yes. The bike becomes so stable that you can't hardly turn corners. This is often a
consequence of having too much rake on the fork for the given head angle and wheel diameter.

 

Idworx has a website. Took about a minute to find the DD's geometry at:
http://www.bikebasics.de/idworx/nl/Bikes/Double_D/Geometrie/geometrie.html

A 68 degree head angle, and yes - 93mm of trail. Obviously DH-derived Freeride-style geometry; meant
to be stable on downhills, even with the fork compressed. So yes, it will be sluggish just about
everywhere else. Which is why it's unresponsive hands-off.

"Tim McNamara" <[email protected]> wrote in message news:[email protected]...
> gvw <[email protected]> writes:
>
> > My nephew bought a secondhand idworx Double D mtb (still damn expensive). Ofcourse I tried it,
> > great bike, great handling, massive tires, very light. But when I tried to open my jacket,
> > riding with no hands on the bar, I lost control. This surprised me since my nephew told me it
> > has enourmes trail (I looked it up 93mm!!).
>
> Do you mean trail or fork rake (a.k.a. fork offset)? Trail is a geometric quantity that is
> determined by head angle, fork rake and wheel diameter.
>
> See http://www.sheldonbrown.com/gloss_tp-z.html and scroll down to "trail" and also read the
> other links.
>
> Trail is the distance from a vertical line drawn through the hub to the ground, which is the
> center of the "contact patch" between the tire and the ground, and a line drawn through the center
> of the head tube to the ground. Normally the vertical line through the center of the axle "trails"
> the line drawn through the head tube. Draw this on a piece of paper, and then imagine what happens
> if you leave everything the same but increase the fork rake: the trail decreases and hence the
> stability of the bike decreases.
>
> If your bike has 93 mm of trail, it will be so stable that it will be hard to ride. If it has 93
> mm of fork rake, then it's quite possible that it has little or no trail and is very unstable. For
> certain types of trick riding this can be desirable.
>
> > Is there such a thing as to much trail?
>
> Well, yes. The bike becomes so stable that you can't hardly turn corners. This is often a
> consequence of having too much rake on the fork for the given head angle and wheel diameter.

 

"Steve Blankenship" <[email protected]> writes:

> Idworx has a website. Took about a minute to find the DD's geometry at:
> http://www.bikebasics.de/idworx/nl/Bikes/Double_D/Geometrie/geometrie.html
>
> A 68 degree head angle, and yes - 93mm of trail. Obviously DH-derived Freeride-style geometry;
> meant to be stable on downhills, even with the fork compressed. So yes, it will be sluggish just
> about everywhere else. Which is why it's unresponsive hands-off.

Well, that explains it. When riding no-handed, the bike will be very unresponsive to tilt and will
be hard to controll that way. 93 mm trail! Yikes!

 

>>My nephew bought a secondhand idworx Double D mtb (still damn expensive). Ofcourse I tried it,
>>great bike, great handling, massive tires, very
> light.
>>But when I tried to open my jacket, riding with no hands on the bar, I lost control. This
>>surprised me since my nephew told me it has enourmes trail (I looked it up 93mm!!). I can ride all
>>my bikes with no hands, including a very twitchy peugot racebike. I thought more trail ment easyer
>>control. Is there such a thing as to much trail?

Kyle.B.H wrote:
> I might be wrong here...but I believe that trail increases stability primarily at high speeds,
> while actually decreasing it at low speeds. Must be some interaction between trail and the
> rotational intertia of the front wheel vs. the vertical component of gravity pulling it in the
> direction of the lean. I'd be interested to hear some real physics behind this phenomenon.

I can't elucidate from the theoretical side but when I draw a bike, I don't minimize or maximize
trail. I adjust head angle, clearance and rake such that trail is 50mm*. I know a few other dabbling
bicycle builders who also use 50mm* as a rough rule of thumb.

That's just one of those constants you remember- like 59cm front center to keep toes off tires, 65mm
between the water bottle bosses so cages fit and a threaded fork column ought to be head tube plus
42mm (room for a 4041 headset)

(*700C wheels - I have never built a 26", 650C or 24" bike totally from scratch)

--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

 

Tim McNamara <[email protected]> wrote in message news:<[email protected]
Blue.local>... <snip>
>
> > Is there such a thing as to much trail?
>
> Well, yes. The bike becomes so stable that you can't hardly turn corners. This is often a
> consequence of having too much rake on the fork for the given head angle and wheel diameter.

Umm... Tim- don't you mean "too little rake" in that last sentence? It contradicts the rest of
your post.

FWIW, I wish terminology were standardized between the bicycle and the motorcycle world. For
motorcycles, "rake" is the angle the steering bearings are tilted from vertical- for instance, a
2004 Ducati Monster has a rake of 24 degrees, which is the same as a bicycle's 66 degree "head
angle". In the same fashion, a motorcycle fork's "offset" is the same dimension as a bicycle
fork's "rake".

Here's some interesting experiments in rake and trail:
http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

Jeff

 

[email protected] (Jeff Wills) writes:

> Tim McNamara <[email protected]> wrote in message news:<[email protected]
> Blue.local>... <snip>
>>
>> > Is there such a thing as to much trail?
>>
>> Well, yes. The bike becomes so stable that you can't hardly turn corners. This is often a
>> consequence of having too much rake on the fork for the given head angle and wheel diameter.
>
> Umm... Tim- don't you mean "too little rake" in that last sentence? It contradicts the rest of
> your post.

Yes, thanks, I mis-typed that and didn't catch it in proof-reading. Too much rake (or offset if you
prefer) results in too little trail; not enough rake results in too much trail.

> FWIW, I wish terminology were standardized between the bicycle and the motorcycle world.

I'm not a motorcyclist, so I don't care. ;-)

 

gvw <[email protected]> wrote:
> This surprised me since my nephew told me it has enourmes trail (I looked it up 93mm!!). I can
> ride all my bikes with no hands, including a very twitchy peugot racebike. I thought more trail
> ment easyer control. Is there such a thing as to much trail?

Yes, and you can get a lot of wheel flop too especially with slack head angles. I have an MTB fork
with two steerers, one of which has about 15mm less rake than the other. The bike was significantly
more floppy and difficult to ride no-hands with the low-rake (high trail) fork setup.

 

Bruni wrote:
> Trail is a speed dependent attribute; it kicks in usually in double digits. Slow speeds are more
> affected by the gravity centering of most geometries. Too little fork offset for a given head
> angle can produce massive trail but little or no gravity centering resulting in wheel flop at slow
> speeds. Tom

You mean double digits in mph or km/h? Either way, this explains why it's much easier to ride no
hands above this "trail threshhold".

&roo