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What is the difference between curved and straight forks? nm(12 posts)

What is the difference between curved and straight forks? nmMikeQ
Dec 18, 2002 7:15 AM
nm
re: What is the difference between curved and straight forks? nmflyweight
Dec 18, 2002 8:09 AM
It's purely a fashion thing. Any supposed advantage such as being stiffer/more responsive/etc. has as much to do with the material of the fork as it does whether the blades are straight or curved.
Shape. But seriously folksEager Beagle
Dec 18, 2002 9:08 AM
Generally, on the same frame, straights tend to produce a steeper angle (wheel closer to pedals), and hence faster steering - better for crits etc, over the longer, more stable curved forks, better for stability.

Obviously, you have to check the fork/steerer tube angle to be sure.
Not trueflyweight
Dec 18, 2002 9:41 AM
Blade shape has nothing to do with the angle. The angle is set by the rake. Rake on a straight blade fork can be (and usually is) exactly the same as a curved fork. Only difference is that with a straight blade fork the rake is built into the crown and on a curved blade fork it's in the blades.
So not trueOffRoadTourer
Dec 18, 2002 5:20 PM
A curved blade made of the same material should be a little more compliant than its straight blade counterpart. The curve should allow it to flex a little more over bumps. A straight blade fork will provide a stiffer but harsher ride. In reality its a miniscule difference.

And just to back up Flyweight, the rake of a fork is not determined by the shape of the fork blade, it is simply a relationship between crown and axle position, the fork could have a huge curve but still position the axle further back than a straight blade if you made it that way. So you most certainly cannot say that straight blades have different steering to curved blades.
So not trueatpjunkie
Dec 18, 2002 6:53 PM
curved blades look more retro, straight more techno. Personally I'm a curved man even if the slight bump absorption is in my head. IMHO they just look better. Those straight Wound Ups look anemic to me.
No difference in compliance because of shape alone (nm)Look381i
Dec 19, 2002 6:32 AM
No difference in compliance because of shape alone?atpjunkie
Dec 19, 2002 2:01 PM
call me silly but physics seems to dictate that a bent rod will flex more than a straight one. try the bent nail theory. two identical nails one straight one with a slight bend. which if you hit square on the head with a hammer will have a greater chance of bending? call it conventional wisdom but force is less displaced when traveling a straight line vs a curve. It is this curves abitlity to spread loads that makes the dome so strong and the arch so popular amongst architects. From my own personal early MTB experience (race and product tester) pre-suspension, MTB makers in 1981-1982 started experimenting with straight BMX style forks. Granted these forks are very rigid by tubular shape as well, but in this era mfr's had many catastrophic frame breaks (at the head tube) where both joints (including lugged frames) Downtube and Top Tube failed and bikes split in two. this lead to the reversion to curved forks.
Perhaps at extreme forces, but not at forces generated by . . .Look381i
Dec 19, 2002 3:12 PM
cycling. Don't forget that a straight fork is also "bent" -- at the steering tube intersection to create rake.

"Comfort" associated with curved forks might be caused by longer wheelbase or other factors in a different frame.

Others in past years have published test data demonstrating fact that straight forks are no more or less compliant than curved ones. I can't seem to lay my mouse on the site(s) at the moment.

Anecdotal point: I went from curved chromed steel to straight carbon with a bike upgrade. Carbon gave more comfort, probably from absorbing road buzz, equivalent lateral stiffness. No noticeable vertical compliance with either. This proves nothing, though.
Perhaps at extreme forces, but not at forces generated by . . .atpjunkie
Dec 19, 2002 8:25 PM
I've seen the articles as well. it just seems to go against basic physics. True, Straight forks are bent but a quick bend at the crown is not going to have the same flex as a long cantilever bend of an entire fork leg. Straight forks tubes are still 'straight', getting all their 'rake' at the crown not spread over the bottom half to third of a curved bladed fork. The comfort issue in ppg 2 would be negated by the equal rake created by the 'bend' in a straight fork. Both would have equal wheelbases and equal rakes. I run carbon on my road bikes but as a Clydesdale have refrained from using on a cross bike. Like I stated earlier, even if the effect is psychosomatic I like curved better, it's the retrogrouch in me. I'd love to find the articles as well. Any bike engineers out there? Framebuilders? I'm not trying to argue and I'm claiming no advanced degrees in physics or engineering. It's just basic science that a curve distributes loads better.
Perhaps at extreme forces, ps . . .atpjunkie
Dec 19, 2002 8:34 PM
I would consider a force strong enough to cause a lugged steel MTB to split at the headtube (and the messy, ugly, gory crash that followed) extreme. yes, it happened to me. had to hike 7 miles caked in Mud and Blood with a newly converted 'travel' bike. The mfr (I rode on a devo/demo squad) informed us (as they recalled the forks) that they transmitted too much shock and vibration to the headtube. As I stated these were thick BMX Style straight tubed cro mo forks but the following raked forks were far smoother. At the time (1982) it almost felt like suspension.
I didn'tEager Beagle
Dec 19, 2002 1:38 AM
say there was a necessary nexus between shape and angle - the shape bit was a joke - geddit?

Have a look at angles and shape though. If you look at the steeper angled (raked) forks - a lot of them are straight bladed for the obvious reason that it placed the axle further back. Obviously in the middle ground of rake, you can find both.

Dunno about where you are, but round here, there are a lot more straight forks in crits than Audax events for exactly that reason.