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Twitchy steering fix?



 
 
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  #1  
Old June 26th 08, 10:25 PM posted to rec.bicycles.tech
al sharff
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Posts: 7
Default Twitchy steering fix?



--
I bought an Independent Fabrication steel Crown Jewel used - it's a
stock frame (non custom) with an IF steel fork - straight blades.

It has very "twitchy" steering when I'm in a descending tight corner.
I tend to oversteer in those situations. The bike feels like it pulls
into the turn to a point where I'm about to loose control.

To compare I have a Trek 5200 (new in 2000, 60cm frame) that I use the
same wheels on and has almost the same fit. The only major difference
I can find with my tape measure is the IF has 42cm handlebars while the
Trek has 44cm. I never notice my cornering problem when I'm on the
Trek.

Anyone have opinions on how I can "smooth out" (or slow down, or make
it less responsive) the high speed cornering on the IF bike? Will
different forks make a difference - any advise on what to go to? Any
other changes that make make a difference in handling?

Thanks,

Al Sharff

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  #2  
Old June 26th 08, 10:49 PM posted to rec.bicycles.tech
Tom Kunich
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Posts: 6,456
Default Twitchy steering fix?

"al sharff" wrote in message
...

I bought an Independent Fabrication steel Crown Jewel used - it's a
stock frame (non custom) with an IF steel fork - straight blades.

It has very "twitchy" steering when I'm in a descending tight corner.
I tend to oversteer in those situations. The bike feels like it pulls
into the turn to a point where I'm about to loose control.


This is probably caused by too much "trail" in the steering. This is easy to
fix by replacing the fork. The trouble is finding which fork has the correct
trail for your frame. This requires pretty much a good frame designer to
know.

  #3  
Old June 26th 08, 11:03 PM posted to rec.bicycles.tech
landotter
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Posts: 6,336
Default Twitchy steering fix?

On Jun 26, 4:25*pm, "al sharff" wrote:
--
I bought an Independent Fabrication steel Crown Jewel used - it's a
stock frame (non custom) with an IF steel fork - straight blades.

It has very "twitchy" steering when I'm in a descending tight corner.
I tend to oversteer in those situations. *The bike feels like it pulls
into the turn to a point where I'm about to loose control.

To compare I have a Trek 5200 (new in 2000, 60cm frame) that I use the
same wheels on and has almost the same fit. *The only major difference
I can find with my tape measure is the IF has 42cm handlebars while the
Trek has 44cm. *I never notice my cornering problem when I'm on the
Trek.

Anyone have opinions on how I can "smooth out" (or slow down, or make
it less responsive) the high speed cornering on the IF bike? *Will
different forks make a difference - any advise on what to go to? *Any
other changes that make make a difference in handling?


Track bikes have less trail usually and are inherently less stable
because they're meant to be ridden differently than road bikes. Not a
whole lot you can do other than swap out for wider handlebars so that
more input means less response. There might be a way to fit a fork in
there to give you some more trail, but that's bigger bux, and the
clearances are already tight.


If you're really uncomfortable with the handling of a track bike on
the road--sell it and buy a single speed bike with road geometry like
a Salsa Casserole, Redline 925, Kona Paddy Wagon, etc, instead of
making bunging up this bike. I've ridden a bike with a fork I hated
for a couple years--a crazy short trail old Tange crit fork, and the
twitchy handling can drive one nuts. Better to offload it to someone
that enjoys it.
  #4  
Old June 27th 08, 12:44 AM posted to rec.bicycles.tech
[email protected]
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Posts: 2,322
Default Twitchy steering fix?

On Jun 26, 4:25*pm, "al sharff" wrote:
--
I bought an Independent Fabrication steel Crown Jewel used - it's a
stock frame (non custom) with an IF steel fork - straight blades.

It has very "twitchy" steering when I'm in a descending tight corner.
I tend to oversteer in those situations. *The bike feels like it pulls
into the turn to a point where I'm about to loose control.

To compare I have a Trek 5200 (new in 2000, 60cm frame) that I use the
same wheels on and has almost the same fit. *The only major difference
I can find with my tape measure is the IF has 42cm handlebars while the
Trek has 44cm. *I never notice my cornering problem when I'm on the
Trek.

Anyone have opinions on how I can "smooth out" (or slow down, or make
it less responsive) the high speed cornering on the IF bike? *Will
different forks make a difference - any advise on what to go to? *Any
other changes that make make a difference in handling?


Talk to IF. I didn't see a geometry table for the CJ. Steep head
angles (common in track bikes) need less fork rake (offset) to have
the same trail as a (commonly, usually, often, etc.) slacker-angled
road frame.

(Is it plugged in dept): Is the headset on the IF in good shape and
adjusted correctly?

Grabbed a table:

http://www.bianchiusa.com/07_pista_concept.html#

28mm rake on 74-75deg head tube angle. Hmmm... 1.1", about what the
builder of my track bike said he built for that bike, with
"about" (or, "at least") 75deg head tube angle.

If you find a real (oval blades, straight brake bolt hole g) road
fork with 28mm rake, let me know, would you?

Although I haven't had any problems with the old "Cinelli" (and maybe
it is a Cinelli) road fork that's in the bike for FG road use, which
is probably a 43-45mm offset, I'd like to have something closer or the
same as the original fork, as that bike handled great on the track and
was not "twitchy", nor did it tighten line in corners unless I wanted
it to.

Please. "Responsive". Typical of the track bikes I've ridden (not
many, true enough, but I went through the rental fleet at Alkek),
rides straight just fine, turns quickly when asked. Not "twitchy".
Doesn't tighten line unless you want. Steep head tube angle, short
rake. --D-y
  #5  
Old June 27th 08, 03:11 AM posted to rec.bicycles.tech
David L. Johnson
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Posts: 1,048
Default Twitchy steering fix?

landotter wrote:

It has very "twitchy" steering when I'm in a descending tight corner.
I tend to oversteer in those situations.


Well, don't do that...

The bike feels like it pulls
into the turn to a point where I'm about to loose control.

To compare I have a Trek 5200 (new in 2000, 60cm frame) that I use the
same wheels on and has almost the same fit. The only major difference
I can find with my tape measure is the IF has 42cm handlebars while the
Trek has 44cm. I never notice my cornering problem when I'm on the
Trek.

Anyone have opinions on how I can "smooth out" (or slow down, or make
it less responsive) the high speed cornering on the IF bike?


I think that you will become accustomed to the way the IF bike handles.
Think about what you are asking. Why would you want a bike which is
_less_ responsive? Ride it for a while, and see if you become more
comfortable with it.

Track bikes have less trail usually and are inherently less stable
because they're meant to be ridden differently than road bikes.


BS. Track bikes have shorter fork rake, thus more trail, than road
bikes. But they also do not handle badly just because they are track
bikes. My track bike has always been the best-handling bike I ever
owned. I can ride it for long periods no hands, and it is as responsive
as any bike can be.

But this nonsense of track bikes being ridden "differently" than road
bikes. How different? Why would you want poorer handling with a track
bike? You wouldn't.

Not a
whole lot you can do other than swap out for wider handlebars so that
more input means less response.


Let's see. The difference between 42cm bars and 44cm bars is less than
5%. Not very impressive. Get the bars that fit your body.

--

David L. Johnson

Anyone who is capable of getting themselves made President should on
no account be allowed to do the job.
-- Douglas Adams
  #6  
Old June 27th 08, 03:29 AM posted to rec.bicycles.tech
landotter
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Posts: 6,336
Default Twitchy steering fix?

On Jun 26, 9:11*pm, "David L. Johnson"
wrote:
landotter wrote:
It has very "twitchy" steering when I'm in a descending tight corner.
I tend to oversteer in those situations. *


Well, don't do that...

The bike feels like it pulls
into the turn to a point where I'm about to loose control.


To compare I have a Trek 5200 (new in 2000, 60cm frame) that I use the
same wheels on and has almost the same fit. *The only major difference
I can find with my tape measure is the IF has 42cm handlebars while the
Trek has 44cm. *I never notice my cornering problem when I'm on the
Trek.


Anyone have opinions on how I can "smooth out" (or slow down, or make
it less responsive) the high speed cornering on the IF bike? *


I think that you will become accustomed to the way the IF bike handles.
* Think about what you are asking. *Why would you want a bike which is
_less_ responsive? *Ride it for a while, and see if you become more
comfortable with it.

Track bikes have less trail usually and are inherently less stable
because they're meant to be ridden differently than road bikes.


BS. *Track bikes have shorter fork rake, thus more trail, than road
bikes. *But they also do not handle badly just because they are track
bikes. *My track bike has always been the best-handling bike I ever
owned. *I can ride it for long periods no hands, and it is as responsive
as any bike can be.

But this nonsense of track bikes being ridden "differently" than road
bikes. *How different? *Why would you want poorer handling with a track
bike? *You wouldn't.


Track bikes have less trail because of the steeper head angle, thus
needing less rake or offset to dial in the trail.I've had a bike with
very quick handling from a really curvy fork with tons of rake--which
isn't poor handling--but it can feel "nervous" to someone that's not
used to it. It's supposedly good for when you're doing a lot of
standing and muscling around and want very little caster effect, and
just want point and squirt. My setup was said to be more "crit" from a
guy that was more expert than I am--but still in the same idea of
close quarters riding of laps on a circuit, but with a bike that has
gears and brakes.

At any rate, my current fixed gear is set up as classic as a road bike
can get with 72.5 angles, etc--and it's a different creature
altogether. It feels slower, but a lot more secure due to the longer
trail. On long sweeps you can really just pick a line instead of
feeling like you're being sucked down like with a shorter trail bike
that demands to be steered.
  #7  
Old June 27th 08, 03:30 AM posted to rec.bicycles.tech
jim beam
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Posts: 5,758
Default Twitchy steering fix?

al sharff wrote:

I bought an Independent Fabrication steel Crown Jewel used - it's a
stock frame (non custom) with an IF steel fork - straight blades.

It has very "twitchy" steering when I'm in a descending tight corner.
I tend to oversteer in those situations. The bike feels like it pulls
into the turn to a point where I'm about to loose control.

To compare I have a Trek 5200 (new in 2000, 60cm frame) that I use the
same wheels on and has almost the same fit. The only major difference
I can find with my tape measure is the IF has 42cm handlebars while the
Trek has 44cm. I never notice my cornering problem when I'm on the
Trek.

Anyone have opinions on how I can "smooth out" (or slow down, or make
it less responsive) the high speed cornering on the IF bike? Will
different forks make a difference - any advise on what to go to? Any
other changes that make make a difference in handling?


you can try monkeying about with different forks, but given that the
frame appears to be standard diameter steel tube, i wouldn't hold out
much hope. i'd stick the trek personally. or get a big tube aluminum
frame. big diameter tubes are very torsionally stiff and pretty much
eliminate this kind of problem. modern thin wall steel tube, especially
in standard diameters, is not very stiff.
  #8  
Old June 27th 08, 03:57 PM posted to rec.bicycles.tech
[email protected]
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Posts: 2,322
Default Twitchy steering fix?

On Jun 26, 9:11*pm, "David L. Johnson"
wrote:
(Someone opined):
Track bikes have less trail usually and are inherently less stable
because they're meant to be ridden differently than road bikes.


(DLJ replied):
BS.


Well said! Continuing:

*Track bikes have shorter fork rake, thus more trail, than road
bikes. *But they also do not handle badly just because they are track
bikes. *My track bike has always been the best-handling bike I ever
owned. *I can ride it for long periods no hands, and it is as responsive
as any bike can be.


Same here. Track bike, one road bike, a Roberts Crit/TT bike, IMS
74deg head tube, 1" of rake. Maybe 1.25, I believe it was 1" though.

Maybe A. Muzi will remember those as I think he was USA importer?

My favorite road bike, ever. Rode straight straight straight, turned
"now".

But this nonsense of track bikes being ridden "differently" than road
bikes. *How different? *Why would you want poorer handling with a track
bike? *You wouldn't.


250m, or shorter track (constant cornering), steep banking (over 40deg
for some tracks), people turning uptrack and down, no brakes. And
having to stay within fairly narrow lanes, etc. etc. Tight packs, no
freewheeling "saves", the pedals go around when the rear wheel does.

No, not the place for a "twitchy" bike.

Can we please put that one in the grave where it belongs?

I think it's pretty funny that if "everyone" could ride that Roberts,
IMHO road steering geometry fashion would change overnight.

Let's see. *The difference between 42cm bars and 44cm bars is less than
5%. *Not very impressive. *Get the bars that fit your body.


I have a twitchy road bike (steep head angle, too much rake); putting
44's (c-c) made it even more wobbly. I'd say by at least 5% g and
wouldn't that be 10% if you count both sides (wobble implying left and
right)? --D-y
  #9  
Old June 27th 08, 05:20 PM posted to rec.bicycles.tech
landotter
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Posts: 6,336
Default Twitchy steering fix?

On Jun 27, 9:57*am, " wrote:
On Jun 26, 9:11*pm, "David L. Johnson"
wrote:
(Someone opined):

Track bikes have less trail usually and are inherently less stable
because they're meant to be ridden differently than road bikes.


(DLJ replied):

BS.


Well said! Continuing:

*Track bikes have shorter fork rake, thus more trail, than road
bikes. *But they also do not handle badly just because they are track
bikes. *My track bike has always been the best-handling bike I ever
owned. *I can ride it for long periods no hands, and it is as responsive
as any bike can be.


Same here. Track bike, one road bike, a Roberts Crit/TT bike, IMS
74deg head tube, 1" of rake. Maybe 1.25, I believe it was 1" though.

Maybe A. Muzi will remember those as I think he was USA importer?

My favorite road bike, ever. Rode straight straight straight, turned
"now".

But this nonsense of track bikes being ridden "differently" than road
bikes. *How different? *Why would you want poorer handling with a track
bike? *You wouldn't.


250m, or shorter track (constant cornering), steep banking (over 40deg
for some tracks), people turning uptrack and down, no brakes. And
having to stay within fairly narrow lanes, etc. etc. Tight packs, no
freewheeling "saves", the pedals go around when the rear wheel does.

No, not the place for a "twitchy" bike.

Can we please put that one in the grave where it belongs?


Shorter trail, less caster. It's basic bike frame design. Perhaps you
can't feel the effects and dismiss it--don't get a big head about it.

  #10  
Old June 27th 08, 05:49 PM posted to rec.bicycles.tech
[email protected]
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Posts: 2,322
Default Twitchy steering fix?

On Jun 27, 11:20*am, landotter wrote:

Shorter trail, less caster. It's basic bike frame design. Perhaps you
can't feel the effects and dismiss it--don't get a big head about it.


Where does "shorter trail" come from?

If you look in here (scroll down to charts):

http://www.johnforester.com/Articles/BicycleEng/Kvale%20Geometry.pdf

you'll see a "track geometry" such as 75deg, 30mm rake, having the
same or more trail as a "road" geometry of 73-73.5deg, 40-45mm rake
(the lower range available in road forks, "average" head angle for
road frames).

Wondering at your rhetoric dept:

Caster?

"Princess and the Pea", reversed?

"Big head"?

My Goodness! Sounds like someone is losing an argument here. Tsk tsk!
--D-y
 




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