Measuring

[darrenhopper]

Morning everybody,

I'm just about to go and have myself a Marino frame & fork made up & I'd quite like to better understand how to measure up the geometries.

For the chainstay length, are the measurements taken from center of the BB to the center of the rear dropout?

BB rise, center of the BB to the horizontal plane? Does that plane pass through the centre of the rear dropout?

I presume the wheelbase is measured axle to axle but how does one account for different fork measurements? Is there a standard length zero rake fork size used for establishing frame geometry?

I should probably mention that I have more than a passing interest in all of this. So far I have built up one chopper (2,100mm wheelbase) & am in the middle of a Downhill rig. So all of this help you are about to give me.... will undoubtedly result in at least one or two trials frames.

Cheers,

Darren

[Revolver]

Morning everybody,

I'm just about to go and have myself a Marino frame & fork made up & I'd quite like to better understand how to measure up the geometries.

For the chainstay length, are the measurements taken from center of the BB to the center of the rear dropout?

BB rise, center of the BB to the horizontal plane? Does that plane pass through the centre of the rear dropout?

I presume the wheelbase is measured axle to axle but how does one account for different fork measurements? Is there a standard length zero rake fork size used for establishing frame geometry?

1) Yes

2) If you measure the wheelbase, say, tie string to either axle, the BB height is from the centre of the bb to that bit of string - in line with the axles.

3) You don't account for the forks... if you look on tarty they use the same set of forks for measuring each frame's geo. Just measure it with whatever forks you've got, it will be fine - the frame you'll be getting will be using the same forks, so if you get the same wheelbase, it will be no different

[darrenhopper]

Alright, cheers man.

Sorry to be asking a heap of numpty questions but I've never given a second thought to the intricacies of any of my bikes.

So when I read that a fork is 400mm tall with a 45mm rake, does that mean that my headset line is effectively drawn from a point 45mm behind the actual front axle position... at 72˚(or whatever)?