Fork Rake
 

43 vs 45 rake, can someone explain the difference? As in how the two perform?

THanks

The rake is like a modification of the head-tube angle. The greater the rake, the less the HT angle. It won't act exactly like a HT of a degree measured to the front axle though, because it has more of a curve. This creates a smoother ride, but less 'connected' to the road, or quick in handling or perception.

To put it in a simple term; the greater the rake measurement, the plush the "plush" the bike is.

Thanks, will I feel a diff between a 43 vs 45?

Possible......but unlikely. The 43 will need a bit more care to keep you out of the ditch when you're not paying attention.

Thanks

As I understand it, your head angle figures into it a fair bit...

I think the OP was assuming that the HT angle didn't change, just different forks on the same bike.

But if not, then, yes, HT angle and rake combine to create trail which is the real thing that affects the handling. This paper from Calfee explains it pretty well.

http://www.calfeedesign.com/tech-pap...bike-handling/

Swapping forks may actually alter the head angle by a poofteenth (like fitting a smaller tyre in front), but I was getting at the fact that a certain amount of rake may be right for one bike, but not for another, due to the head angle.

This is backwards. A greater rake decreases trail, the same effect as increasing/steepening the head angle. A lower amount of rake creates a larger trail and therefore more of a caster stabilizing effect. It's easier to ride a bike no hands that has more trail.

http://www.dclxvi.org/chunk/tech/trail/

That's why its difficult to ride a unicycle. No trail, no rake.

I tried to add some trail last time I rode a unicycle and fell backwards.

If you notice any diff at all is that the bike could feel a tiny smidge more stable with the 43. All else being equal you probably won't notice a difference. Your fork tips move more than 2mm fore-aft just riding, hitting bumps, and braking.

It is highly unlikely that other parameters being equal (head tube angle, fork length measured parallel to the steerer from from the bottom of the lower bearing race to the center of the front wheel axle), that you would notice any difference between a 43mm rake and a 45mm rake. On a bike with 700c rims, the 43mm rake fork will give you 2mm more of trail.

http://i32.photobucket.com/albums/d7...mv45mmRake.jpg

FWIW, retired framebuilder Dave Moulton has a couple of great blog articles you might find informative.

"As with any design aspect, more is not necessarily better; for a road bike with a 73 degree head angle the optimum trail seems to be around 2 to 2 ½ inches (50 to 63mm.)", so 56mm - 58mm of trail is pretty optimal.

Trail, fork rake, and a little bit of history

Head Angles and Steering

Swapping forks does not change the head angle, only rake! Unless the fork is shorter or longer in which case the whole geometry of the bike is in the crapper!

http://bikeforums.net/attachment.php...hmentid=213298This seems pretty simple to me.http://bikeforums.net/attachment.php...hmentid=213297
http://www.bikeforums.net/images/misc/pencil.png

There's nothing incredible about the possibility of different forks being slightly different lengths; in fact it's quite likely.

Do a little bit of trigonometry and you'll find that it'll take an awful lot of difference in fork length to make much difference to the head angle though. But, swapping forks may affect it slightly, as I said.

Truth.

A picture may help. Remember that HTA and STA are the angles the head tube and seat tube make with a baseline through the dropout centers, so adding 18% to the length of the fork will move the front of the frame higher, making the HTA and the STA 2° less than they with with the original fork. Putting on a fork that is 118% of the original fork isn't something you'd ordinarily do, but the drawing is exaggerated to demonstrate the effect.

http://i32.photobucket.com/albums/d7...rForkonHTA.jpg