New forks: advice on rake

[cavasta]

I'm running a Trek 2.3 (2010 model) and need to replace the damaged carbon fiber forks. The bike is size 56cm, has a 73.5 degree headtube, forks with 40mm rake (offset), 58mm trail and 983mm wheelbase (all data from the Trek catalogue). It's a stable and self-assured ride though perhaps it's a little too stable sometimes. I've seen a lovely pair of Ritchey forks but the the rake is 45mm. I appreciate how this will change the way the bike rides and feels via its impact on the trail (longer rake = shorter trail = livelier handling). My question is will the leap from 40mm rake to 45mm rake provide just a bit too much liveliness? Would I be better going for 43mm or maybe even sticking with safe 40mm?

All the dimensions of all the 56cm Trek bikes in the Madones, 2 series and 1 series (in the 2010 range), are the same (as mine, above). The dimensions change according to the size of the bike frame (for example, 54cm have 73 degree headtube, 45mm rake, 56mm trail and 981mm wheelbase). I guess there's a pretty good reason why they choose these configurations?

I've found this tool quite useful in providing me with the data that a different rake will produce: http://yojimg.net/bike/web_tools/trailcalc.php

So, 45mm rake or 43mm? Any thoughts and advice will be greatly appreciated.

 

[oldbobcat]

Trek's 40mm rake with a 73.5 degree head angle makes for quick point-and-shoot handling that can be fun on smooth roads, but in my opinion it's a handful in puddles, gravel, loose dirt, and cobbles. Extending the rake means shortening the trail, which lets the front wheel wander but also requires less effort for course correction. Extending the trail (while maintaining the head angle) makes the bike quicker to turn in with subtler inputs.

If I were looking to tame the Trek handling a bit (and I believe that would be beneficial) without changing the character that much, I'd lean toward the 43mm rake. If leading the pack on bad road and manky conditions were my goal, I wouldn't hesitate to use the 45.

To see how Trek is handling this, compare the geometry charts of the civilian Domane with the "Classics Edition," the one that Mr. Cancellara wins classics on. Spartacus rides a 58. The civilian version sports a head angle of 72.0 degrees with 48 mm of rake, yielding 60 mm of trail; the race version uses a 72.8 degree head angle with 53 mm of rake to yield 51 mm of trail. 9mm shorter trail and soft fat tires find the path of less resistance and stay upright through the cobbles.

 

[cavasta]

Hey oldbobcat, good reply - very informative. Thanks for that. I must admit that I'm starting to lean towards 43mm. I'm a bit nervous about going from 40mm to 45mm. Forks aren't like clothes, where you can try before you buy! Hence I want to be as informed as I can before letting go of my cash.

The bike's current set up works well enough, though as I mentioned in my OP, it sometimes feels a little tame. I've been checking out the geometries of some of the main bike manufacturers and comparing them with my geometry (56cm top tube and 73.5 deg head tube angle). About two thirds go with 43mm rake, with most of the rest (Trek being the main exception) going with 45mm. Hmm...

 

[oldbobcat]

Most riders don't need a dedicated cobble-crusher. With a 73.5 head angle, the 43 mm fork should be a nice all-arounder.

 

[cavasta]

Cheers oldbobcat