Touring - Those long curved fork

I remember riding a french bike years ago that had a long curved fork.
A rider could watch the fork flex on the bumps as he rode.

How are those forks on Chip N Seal? Are they smooth as a Cadillac?
They look elegant.
Todays fat stiff forks, carbon and other, transmit the chip n seal bumps to one's hands and take much of the fun out of riding.

The only real benefit of the curve is that it modifies the rake to lengthen the wheelbase, which makes the bike a little more stable and smooths out some of the bumps.

Using a straight carbon fork isn't going to cause additional discomfort, if the geometry is the same. Designers pretty much know nowadays to make carbon parts laterally stiff but vertically compliant.

IMO it's a really bad sign if a fork is structurally weak enough that you can actually see it flex.

Ye olde Raleigh Sport had pretty flexy curved fork blades. It was really smooth.

The only real benefit of the curve is that it modifies the rake to lengthen the wheelbase, which makes the bike a little more stable and smooths out some of the bumps.


Incorrect.
*Increasing* rake results in *decreasing* trail, and since trail is what influences stability, it results in a quicker-turning, *less* stable bike.
Ref: http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry#Trail

Also, curving the blades is not necessary to give a fork rake.
Using straight blades with an angle at the crown results int the same geometry.
Example of a straight-blade fork with 44mm rake: http://www.amazon.com/dp/B002K9BFOY/ref=asc_df_B002K9BFOY886953?tag=the004-20&creative=380333&creativeASIN=B002K9BFOY&linkCode=asn

Stiffness and strength are two different properties, so having a flexible fork wouldn't necessarily make it a weak fork.

I usually see wider tires indicated as the cure for chipseal, rather than flexible forks or suspensions. If nothing else, a lot of that vibration is going to be come from the rear anyway.

*Increasing* rake results in *decreasing* trail, and since trail is what influences stability, it results in a quicker-turning, *less* stable bike.
Erm, read it again... I said "modifies," not "increases," and I did not mention trail at all. I pointed out that the curve affects comfort (shock absorption) by lengthening the wheelbase. Responsiveness / turning speed doesn't affect shock absorption.

I can see how a straight steel or aluminum fork may be vertically stiffer and therefore less comfortable than a curved steel/aluminum fork (also depending on the tubing, I suppose). But CF allows for more vertical compliance and absorbs a fair amount of road buzz, so my assumption is that a straight CF fork can be, and usually is, designed to be at least equally as comfortable as a curved steel fork.



Also, curving the blades is not necessary to give a fork rake.
Right, which is why I mentioned that you could have a straight fork with the same geometry specs, thus using straight forks will not necessarily increase the transmission of road buzz.

"But CF allows for more vertical compliance and absorbs a fair amount of road buzz, so my assumption is that a straight CF fork can be, and usually is, designed to be at least equally as comfortable as a curved steel fork."

Though, if one looks at touring weight carbon forks they are pretty heavy, and whether they left in a lot of design space for the vertical compliance is another mater. I get my vertical compliance by using the right tires and the load to smooth out the road.

I have never owned the newer road bikes with carbon forks, but I wonder to what extent there is a real difference in feel that is attributable to compliance. They seem to have a lot of depth to the fork section that would make them stiffer, and I am not convinced bendy, to a suspension degree, would be good for efficiency or handling. Is it possibly just a weight thing where if a fork is going to be moved up a half inch at the speed you are crossing a bump, it hurts less if there is a pound less weight behind it. Like being hit by a lighter bat? With touring bikes, what I think happens on road vibe is that one has front end load weight holding down the front end against larger volume, say 85 psi tires, and the end result is the tires take more of the vibe. But if the tires where really hard it would hurt more to take a certain velocity hit with more weight behind it.

I say ride it and see. I heard a lot of buzz about how buzzy and stiff and uncomfortable aluminum frames were. Then I got one. I love it. I don't notice any problem caused by a stiff aluminum frame.

I admit, I'm old, and when road bikes with straight forks came along I was dubious. But I believe manufacturers know what they're doing (for the most part.) I'm not going to condemn them without riding some.

There was a time when many men in the pro peleton rode Vitus aluminum frames because they were more comfortable.
Comfort depends upon the build.

I`ve never ridden a bike with a carbon frame or fork, but I thought that vibration dampening was supposed to be one of their selling points.


IMO it's a really bad sign if a fork is structurally weak enough that you can actually see it flex.
I hope you`re wrong about that- I can see the fork flex on all my bikes when I hit bumps and I only weigh 140#. On my lightest bike, a Bridgestone RB-T, it moves so much that it really freaked me out until I came to trust it.

Carbon fiber vibrates very well.

I have a carbon fiber bike and a carbon fiber cello. Both vibrate very well.

http://luisandclark.com/

Yo Yo Ma has one he says he loves. A US Navy orchestra uses all carbon fiber cellos. Mine sounds better the more I play it.

I have a carbon fiber bike and a carbon fiber cello. Both vibrate very well.

My principle complaint against carbon fiber on bicycles is just that it`s so untraditional and I personally think it`s ugly. For a cellist, I suppose you REALLY need to be open minded to make that switch.

Curved steel forks can be vertically compliant providing a smooth ride on rough roads while being stiff laterally for precise steering. This is suspension technology that along with wider tires has been proven through decades of use.

I remember riding a french bike years ago that had a long curved fork.
A rider could watch the fork flex on the bumps as he rode.
the fun out of riding.

The reason for the long curved fork was probably to reduce the trail for the slack head tube angle common on these bikes.