reduce rake, bend a fork?

Kyle.B.H. said:

Could a skilled frame-builer safely bend a steel fork?

I have a new-old frame that exhibits rather squirrly handling, and upon
close examination, appears to have about 5 to 5.5 cm trail, with about 5
cm rake. My primary steed exhibits about 6.5 to 7 cm trail and I like
it that way. Considering the new-old bike is a loaded touring bike, I'd
like it to have a similarly stable steering geometry. Reducing the rake
from 5cm to 4cm will accomplish this for me.

So, short of buying a new fork (would likely have to go custom, needs to
be 1" threaded), is it possible to safely bend an old fork to reduce rake?

Thanks,

Kyle

I've successfully "un"-bent a steel fork to reduce rake. It turned out
fine, but I wasn't sure it would work and was prepared to scrap the
fork if necessary. I only adjusted the rake by a few millimeters, but
I'd be curious to see how it works if you give your centimeter
adjustment a try.

When you bend the fork, you'll also be dropping the front end of you
bike slightly and bringing it forward. I think that you may have better
luck asking in rec.bicycles.marketplace if someone can sell you a used
touring fork w/ a 1" steerer.

Andres

Quoted message said:

When you bend the fork, you'll also be dropping the front end of you
bike slightly and bringing it forward. I think that you may have better
luck asking in rec.bicycles.marketplace if someone can sell you a used
touring fork w/ a 1" steerer.

Andres

I think I'll be raising the front end sligtly (bending for inward and
down). Which would be a bonus actually, because it would slacken my HT
angle slightly, further increasing trail.

Kyle

Kyle B.H. said:

Could a skilled frame-builer safely bend a
steel fork?

Yes.

Quoted message said:

I have a new-old frame that exhibits rather
squirrly handling, and upon
close examination, appears to have about 5 > to 5.5 cm trail, with

about 5

Quoted message said:

cm rake. My primary steed exhibits about > 6.5 to 7 cm trail and I

like

Quoted message said:

it that way. Considering the new-old bike is > a loaded touring

bike, I'd

Quoted message said:

like it to have a similarly stable steering
geometry. Reducing the rake
from 5cm to 4cm will accomplish this for me.

5 to 5.5 cm of trail is well within the normal range. My primary bike
has less than that. 6.5 to 7 cm of trail seems excessive to me. There
is a point of diminishing returns where steering becomes overly heavy,
and low speed wheel flop becomes an issue.

I'm convinced that other factors besides trail contribute to a stable
feel (head angle, wheelbase, stem length, and even tire width).

My old touring bike with 17-1/2" chainstays, 72 degree angles, 2-1/8"
fork offset, and 27 x 1-1/4" wheels/tires was the most stable ride I
ever had.

Are you measuring or calculating trail? I've tried measuring it with a
straightedge and plumb line, and it's not easy.

Art Harris

Quoted message said:

5 to 5.5 cm of trail is well within the normal range. My primary bike
has less than that. 6.5 to 7 cm of trail seems excessive to me. There
is a point of diminishing returns where steering becomes overly heavy,
and low speed wheel flop becomes an issue.

I'm convinced that other factors besides trail contribute to a stable
feel (head angle, wheelbase, stem length, and even tire width).

My old touring bike with 17-1/2" chainstays, 72 degree angles, 2-1/8"
fork offset, and 27 x 1-1/4" wheels/tires was the most stable ride I
ever had.

Are you measuring or calculating trail? I've tried measuring it with a
straightedge and plumb line, and it's not easy.

Art Harris

I measured it a dozen times (string and plum bob). Then I measured rake
and head angle and calculated trail and they more or less agreed. Head
angle is 72.7 give or take.

One contributing factor could be that its a really big frame - a 63, and
not very beefytubing, so I could be getting lots of flex. But
basically, the bars want to wiggle left/right, and when I take my hands
off the bars, they girate back and forth.

I don't want to get into a trail argument (read those posts), but I
think this will improve things.

Kyle

Kyle asked:

Quoted message said:

Could a skilled frame-builer safely bend a steel fork?

Sure: recumbent builders have been adapting 27-inch and 700c forks to
20/406 wheels for decades by bending them severely. The incidence of
fork failure due to proper bending has been negligible.

--
"Bicycling is a healthy and manly pursuit with much
to recommend it, and, unlike other foolish crazes,
it has not died out." -- The Daily Telegraph (1877)

visit the flea market, eyeball the junk for another fork.
ie-older trek frames sport hefty 700-27" u forks
buy and bennnnnnd.

Quoted message said:

When you bend the fork, you'll also be dropping the front end of you
bike slightly and bringing it forward. I think that you may have better
luck asking in rec.bicycles.marketplace if someone can sell you a used
touring fork w/ a 1" steerer.

I think you are describing the effect of adding rake, which
would indeed lower the front.

If he un-curves the blades, his head angle will be slacker
and the headset will be higher from the ground.

I'm with Andres on 'get the proper fork' which is good advice.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m said:

Kyle asked:

Quoted message said:

Could a skilled frame-builer safely bend a steel fork?

Sure: recumbent builders have been adapting 27-inch and 700c forks to
20/406 wheels for decades by bending them severely. The incidence of
fork failure due to proper bending has been negligible.

Examples? I assume that the forks were also cut down, and the dropout
reattached to the shorter legs?

--
Tom Sherman - Earth

Kyle.B.H. said:

Could a skilled frame-builer safely bend a steel fork?

Quoted message said:

I have a new-old frame that exhibits rather squirrly handling, and upon
close examination, appears to have about 5 to 5.5 cm trail, with about 5
cm rake. My primary steed exhibits about 6.5 to 7 cm trail and I like
it that way. Considering the new-old bike is a loaded touring bike, I'd
like it to have a similarly stable steering geometry. Reducing the rake
from 5cm to 4cm will accomplish this for me.

While this is possible, it depends upon the type of tubing. Some
tubing (like reynolds 753) just won't bend - it will break instead.
In other cases (reynolds 531) the framebuilder once upon a time was
the one to create the rake to begin with.

What if it doesn't work ?? There are other things that could lead to
squirrely handling, such as : (a) Insufficiently tight headset (b)
quite "vertical" (specialized turbo-type with a raised center strip)
tires with excessive wheel-flop, (c) insufficiently heavy combination
of fork, bars, & stem, or even (d) Poor combination of weighting and
tire inflation front/rear (e.g. a super-upright position with no load
and no traction on an overinflated front wheel.)

I have 2 forks from similar bikes that differ by greater than 4 oz.
The heavier fork gives a more stable ride.

Before bending the fork, I'd do experiments with headset tightening
and extra mass on the steering column and tire inflation.

- Don Gillies
San Diego, CA

Quoted message said:

Quoted message said:

Quoted message said:

Could a skilled frame-builer safely bend a steel fork?

Sure: recumbent builders have been adapting 27-inch and 700c
forks to 20/406 wheels for decades by bending them severely.
The incidence of fork failure due to proper bending has
been negligible.

Examples?

http://www.recycledrecumbent.com/pictures%204.htm

Quoted message said:

I assume that the forks were also cut down, and the dropout
reattached to the shorter legs?

You know what happens when you assume...

--
"Bicycling is a healthy and manly pursuit with much
to recommend it, and, unlike other foolish crazes,
it has not died out." -- The Daily Telegraph (1877)

LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m said:

Quoted message said:

Quoted message said:

> Could a skilled frame-builer safely bend a steel fork?

Sure: recumbent builders have been adapting 27-inch and 700c
forks to 20/406 wheels for decades by bending them severely.
The incidence of fork failure due to proper bending has
been negligible.

Examples?

http://www.recycledrecumbent.com/pictures%204.htm

Quoted message said:

I assume that the forks were also cut down, and the dropout
reattached to the shorter legs?

You know what happens when you assume...

I know of cases where the legs on AMP suspension forks have been
shortened for use with smaller wheels.

--
Tom Sherman - Earth

Donald Gillies said:

Kyle.B.H. said:

Could a skilled frame-builer safely bend a steel fork?

Quoted message said:

I have a new-old frame that exhibits rather squirrly handling, and upon
close examination, appears to have about 5 to 5.5 cm trail, with about 5
cm rake. My primary steed exhibits about 6.5 to 7 cm trail and I like
it that way. Considering the new-old bike is a loaded touring bike, I'd
like it to have a similarly stable steering geometry. Reducing the rake

Quoted message said:

from 5cm to 4cm will accomplish this for me.

While this is possible, it depends upon the type of tubing. Some
tubing (like reynolds 753) just won't bend - it will break instead.
In other cases (reynolds 531) the framebuilder once upon a time was
the one to create the rake to begin with.

I have no idea, its a mystery frame.

Quoted message said:

What if it doesn't work ?? There are other things that could lead to
squirrely handling, such as : (a) Insufficiently tight headset (b)
quite "vertical" (specialized turbo-type with a raised center strip)
tires with excessive wheel-flop, (c) insufficiently heavy combination
of fork, bars, & stem, or even (d) Poor combination of weighting and
tire inflation front/rear (e.g. a super-upright position with no load
and no traction on an overinflated front wheel.)

Like I mentioned earlier, its a very tall frame. I have a fairly
upright position - 9cm stem, 45 degree back, bars equal to saddle - but
nothing severe. 32mm Pasela's. I do notice that when I do a front-end
check (i.e. hold the front brake and rock the bars fore and back to
check for heaset looseness) I get a LOT of flex. Its hard to tell if its
just the fat tires or undersized fork blades or perhaps the 10+ inch
steerer tube, but it really moves a lot. This could definitely contribute.

I'll probably just learn to ride it - it'll make me a better bike handler.

Donald Gillies said:

Kyle.B.H. said:

Could a skilled frame-builer safely bend a steel fork?

Quoted message said:

I have a new-old frame that exhibits rather squirrly handling, and upon
close examination, appears to have about 5 to 5.5 cm trail, with about 5
cm rake. My primary steed exhibits about 6.5 to 7 cm trail and I like
it that way. Considering the new-old bike is a loaded touring bike, I'd
like it to have a similarly stable steering geometry. Reducing the rake

Quoted message said:

from 5cm to 4cm will accomplish this for me.

While this is possible, it depends upon the type of tubing. Some
tubing (like reynolds 753) just won't bend - it will break instead.
In other cases (reynolds 531) the framebuilder once upon a time was
the one to create the rake to begin with.

I have no idea, its a mystery frame.

Quoted message said:

What if it doesn't work ?? There are other things that could lead to
squirrely handling, such as : (a) Insufficiently tight headset (b)
quite "vertical" (specialized turbo-type with a raised center strip)
tires with excessive wheel-flop, (c) insufficiently heavy combination
of fork, bars, & stem, or even (d) Poor combination of weighting and
tire inflation front/rear (e.g. a super-upright position with no load
and no traction on an overinflated front wheel.)

Like I mentioned earlier, its a very tall frame. I have a fairly
upright position - 9cm stem, 45 degree back, bars equal to saddle - but
nothing severe. 32mm Pasela's. I do notice that when I do a front-end
check (i.e. hold the front brake and rock the bars fore and back to
check for heaset looseness) I get a LOT of flex. Its hard to tell if its
just the fat tires or undersized fork blades or perhaps the 10+ inch
steerer tube, but it really moves a lot. This could definitely contribute.

I'll probably just learn to ride it - it'll make me a better bike handler.

Kyle.B.H. said:

Could a skilled frame-builer safely bend a steel fork?

I have a new-old frame that exhibits rather squirrly handling, and upon
close examination, appears to have about 5 to 5.5 cm trail, with about 5
cm rake. My primary steed exhibits about 6.5 to 7 cm trail and I like
it that way. Considering the new-old bike is a loaded touring bike, I'd
like it to have a similarly stable steering geometry. Reducing the rake
from 5cm to 4cm will accomplish this for me.

So, short of buying a new fork (would likely have to go custom, needs to
be 1" threaded), is it possible to safely bend an old fork to reduce rake?

Sure. Support the fork at the crown and dropouts and whack the back of the
blades with a soft mallet until you acheive the rake you need.

--

John ([email hidden])

Kyle.B.H. said:

Could a skilled frame-builer safely bend a steel fork?

I have a new-old frame that exhibits rather squirrly handling, and upon
close examination, appears to have about 5 to 5.5 cm trail, with about 5
cm rake. My primary steed exhibits about 6.5 to 7 cm trail and I like
it that way. Considering the new-old bike is a loaded touring bike, I'd
like it to have a similarly stable steering geometry. Reducing the rake
from 5cm to 4cm will accomplish this for me.

So, short of buying a new fork (would likely have to go custom, needs to
be 1" threaded), is it possible to safely bend an old fork to reduce rake?

Sure. Support the fork at the crown and dropouts and whack the back of the
blades with a soft mallet until you acheive the rake you need.

--

John ([email hidden])

Tom Sherman said:

LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m said:

Quoted message said:

>> Could a skilled frame-builer safely bend a steel fork?
>
> Sure: recumbent builders have been adapting 27-inch and 700c
> forks to 20/406 wheels for decades by bending them severely.
> The incidence of fork failure due to proper bending has
> been negligible.

Examples?

As far as I can recall, the Easy Racer "homebuilder" plans recommend
adding to the rake of a 27"/700C fork in order to make it compatible
with the shallow head angle and small wheel of that particular design.
The fork is simply bent for greater rake and an additional bridge added
for a brake mount. No other modification is needed.

Nowadays, I'd guess that it's easier and cheaper to simply buy an Easy
Racer fork. They're pretty supportive of the homebuilder community.

FWIW: Easy Racer was having some failures of its unicrown-style fork.
This was on forks used on high-mileage bikes with high-pressure
451-size tires and bodysocks, so the forks were being subjected to long
periods of high speed, high-stress riding. I believe the issue is
addressed on the Easy Racer website.

Jeff

Tom Sherman said:

LioNiNoiL_a t_Y a h 0 0_d 0 t_c 0 m said:

Quoted message said:

>> Could a skilled frame-builer safely bend a steel fork?
>
> Sure: recumbent builders have been adapting 27-inch and 700c
> forks to 20/406 wheels for decades by bending them severely.
> The incidence of fork failure due to proper bending has
> been negligible.

Examples?

As far as I can recall, the Easy Racer "homebuilder" plans recommend
adding to the rake of a 27"/700C fork in order to make it compatible
with the shallow head angle and small wheel of that particular design.
The fork is simply bent for greater rake and an additional bridge added
for a brake mount. No other modification is needed.

Nowadays, I'd guess that it's easier and cheaper to simply buy an Easy
Racer fork. They're pretty supportive of the homebuilder community.

FWIW: Easy Racer was having some failures of its unicrown-style fork.
This was on forks used on high-mileage bikes with high-pressure
451-size tires and bodysocks, so the forks were being subjected to long
periods of high speed, high-stress riding. I believe the issue is
addressed on the Easy Racer website.

Jeff