Fork rake questions(after reading Dans article)

Triathlon Forum
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  1. What are ‘good’ head tube angles and fork rake/trail numbers for a nicely handling Tri bike. Would a 73* head tube angle and 45mm fork rake be bad?

  2. Looking at Treks specs, it has the fork rake and trail, but why do they change with size for the bike? i.e the smaller the bike the more trail

  3. Anybody know what the fork rake is on the Giant TCR composite?

  4. Also, can I measure this on my existing bike? Thanks

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1.? I’ll let a frame designer answer it. Like many dimensions, this is a personal preference, One’s person agile is another’s twitchy.

  1. The smaller the bike, the shorter the wheelbase. The smaller bikes need to overcome toe-clip overlap and faster handling due to this shorter wheelbase. Most makers will increase the size of their bikes at an increment greater than the size of the front-center distance. They do this by steepening head angles and shortening the fork rake on the larger bikes. Geez the more I write the worse the explanation.

  2. small frames get 5.0cm, med get 4.5 cm, large 4.0cm.

  3. yes, Park makes a fork guage/alingment tool that will give you a measurable way to get the centerline of steerer to centerline of hub dimension (rake).

-SD

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You should also cnnsider fork length.Longer blades will slacken the head angle,shorter will steepen it.Not all forks are the same. I too know absolutly nothing about this this subject. Cullen

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The rake on the TCR composite is 43mm.

My bike was designed with a HT angle of 73 with a fork rake of 45. According to the builder, this combo - in addition to the stack height - makes the bike slower steering or less twitchy than a 43mm rake with the same HT angle and stack height.

It is a DL tri bike (road bike front end, 74.5 seat tube angle) and is very stable in the aero bars. I don’t know if this translates to a traditional tri bike or not…

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" What are ‘good’ head tube angles and fork rake/trail numbers for a nicely handling Tri bike. "

The terms “nicely handling” and “tri bike” are oxymorons. Too much weight over the front wheel. Dan theorizes about balancing this out with tri bikes with 71 or 72 head tube angles and rakes of 48/50 degrees as a solution for this. He even wrote an article recently about a one off special like this he had built up and actually rode in a tri. But there must be some reason why this hasn’t caught on. My guess is because this would give you an exceptionally long wheelbase tri bike, which would in theory sorts out the twitchyness but would present other problems. IMO, a tri bike will never handle or climb like a road bike no matter how hard you tri(pun).

73/45 would be fairly normal for a tri bike .

TCR (I think) is 43, but it’s a road geometry, and as a TCR owner, feels it’s is a really good handling bike. Certainly better than my P2K. And I’m sure ONCE wouldn’t disagree. I’d never consider a steep angle for road racing, group rides , climbing or fast curvy decents.

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I stand corrected. The TCR composite does in fact use a 43mm fork. My information was regarding the TCR, but the previous aluminum version, TCR 0.