Fork rake - how much does 2mm matter?

JonEdwards

Putting my bike away after a ride on Saturday, and noticed a crack in one of the bolt holes in the stem. Popped the stem off and noticed another crack running down the front of my full carbon steerer. Both parts are 10+ years old and have been well used, so I'm not too devastated, and I'm glad to have spotted the damage before my face said hello to the tarmac. (I have a nasty habit of jumping the speed bumps on the way down the hill to my house at 30+ mph which might not have helped matters!)

My forks appear to be 43mm rake (at least that's what's stamped on the inside of the dropout). A mate has offered me a cheap set of Condor badged Deda Nero forks which he thinks are 45mm rake.

So how much does the 2mm matter? I'm guessing it'll make the bike a little more stable in a straight line (more castor?), but slightly more inclined to "flop" once it's pulled off centre - but by a noticeable amount...??

Thanks!

Erasmus

Jon, I don't think 2mm will make a massive difference, but someone will correct me if I'm wrong. However, the relationship between rake and trail is the other way around. For a fixed fork angle, increasing the rake will reduce the trail, making the handling sharper, and less likely to 'flop'. I know this sounds wrong,but there are plenty of diagrams on the internet which demonstrate this better than I can explain. Hope this helps, John

sungod

as above, increasing rake reduces trail, 2mm will make the bike a smidge faster to corner and a bit less stable, but in practical terms i doubt it'll matter, the result will still be within normal range for a road bike

this explains it...

http://calfeedesign.com/tech-papers/geo ... -handling/

bear in mind forks are not all the same length, so check that too (it'll only be a few mm difference at most)

to be certain, you could measure the current set up and calculate what the trail would be with the new fork

maddog 2

what sungod said. Bit less stable but hardly anything in it. I doubt you'll even notice.