Rigid forks: straight blade or curved??- Mtbr.com

1. ## Rigid forks: straight blade or curved??

Is it me or do all 29er rigid forks have straight blades? Is there an advantage? Would a curved blade be more comfortable? What the dilly-o?

2. Curved blades aren't made long enough to correct for suspension lengths. If you're not using a fork, you could probabl have one custom made. Straight blades are simply available.

3. Originally Posted by ~martini~
Curved blades aren't made long enough to correct for suspension lengths. If you're not using a fork, you could probabl have one custom made. Straight blades are simply available.
All curved blades start off as straight blades. The builder then rakes them over a mandrel. So its not really a question of them being available in bent sizes, but being available in lengths long enough to work when bent.

Between a straight and curved fork made from the same fork blades (and identical geometry), there should be no perceptible difference in ride quality.

Dr.Welby

4. Even in a 90º headtube angle, 0mm rake situation? Logic tells me a bend helps, but if it does so for the above example, then why not in something more realistic? Perhaps not all directions of input are absorbed better, but at least the ones in line with the crown-axle axis? Educate me!

5. ## Me too!

Originally Posted by Cloxxki
Even in a 90º headtube angle, 0mm rake situation? Logic tells me a bend helps, but if it does so for the above example, then why not in something more realistic? Perhaps not all directions of input are absorbed better, but at least the ones in line with the crown-axle axis? Educate me!
i am curious to know more, as well. it does seem logical that a curve would have a more spring-like reaction to input (from bumps and stuff). isn't that why road bikes adopted a curved fork blade back in the day? when everything was made from steel...

6. A curved fork is a longer spring, so all else being equal (material, wall thickness, taper...) it will be softer. But like the good doctor says, it may be such a small difference as to not be perceptible.

7. Originally Posted by bikecop
A curved fork is a longer spring, so all else being equal (material, wall thickness, taper...) it will be softer. But like the good doctor says, it may be such a small difference as to not be perceptible.
Yeah, the curved fork is slightly longer, so it could deflect more. But since the fork is a cantilevered beam, most of the deflection is coming from the bending at the top of the fork near the crown, where the bending moment is greatest. The bending moment near the tips, where the bend, is much smaller.

The key thing is perceptible. FEA or a dial indicator might show a difference. But on the trail I'd bet a 3 psi difference in tire inflation would make a bigger difference than straight versus raked.

Historically forks are raked because it's easier to use 1 crown with no built-in angle and rake the blades to the offset you need, instead of casting different crowns for different offsets. It's also easier to cut the top of a straight tube flat and plug it into the crown, than to have bend and miter a unicrown. These days, MTB fork blades are easy to get pre-bent as unicrown legs, and it's easier to miter them accurately on a milling machine than to rake them on a mandrel. Especially some of the new 29" fork legs - I'd hate to have to bend one of those monsters.

Dr.Welby

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•