Needs more rake

Them randonneur folks like their fork with a lot of rake (offset from steering axis). Check out this new fork destined for a custom bike. 70mm of rake. Typical carbon road forks have 43mm rake. 70mm rake fork.jpg



4 Comments

Yeah but people who ride typical carbon road forks don’t ride the sort of distances randonneurs ride! They also don’t need to keep supplies handy in a front bag. That said 70mm seems like a lot.

70mm is a lot.

the rake has more to do with fatter tires and handlebar bags and not so much the distance.  sure, P-B-P is long, but RAAM is longer.  even if 43-45mm rake carbon forks aren’t in the majority for the former, they certainly are for the latter.

bombing downhill at 40+ on the bike above with skinny tires and no weight up front wouldn’t be very relaxing.

The weird thing is, long rake actually reduces your trail, which leads to twitchier steering…which is not very randonneur. My guess is that the bike that fork will end up on has a very slack head angle (70-72 degrees?), so that the rake contributes to a longer wheelbase rather than changing the steering geometry drastically.

That is, unless, as Mark V suggests, it’s for carrying a heavy load on the front end, and the very low trail is to reduce wheel flop. I can’t imagine a porteur bike handling very nicely unless it’s loaded, which is kind of the opposite of what one might expect out of a bike…

yes, i don’t know the head angle off the top of my head, but the bike is specifically designed for a size-able handlebar bag.  i don’t think head angle is steeper than 73 anyways. 

it’s worth mentioning that a component of trail is the radius of the front wheel, thus replacing a skinny tire with a bigger one (assuming that there’s clearance for it) will change the trail somewhat, specifically it would increase trail and make the bike more stable at high speeds but a bit floppier at low speeds.

track bikes have very short rake (25-35mm) to balance out their 74.5 deg+ head angles.  often times, their trail numbers are not that remarkable.  it is probably more valid to say that a track bike’s nimbleness comes primarily from the short wheelbase.

in the mtb world, many frame and fork designers have come to the conclusion that 29-er forks require more rake to balance trail for the larger wheels vs 26-in.  the net effect is to make the newer 29-ers more agile instead of being big sloppy dumptrucks on tight trails

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