what's my BB drop?

[vqdriver]

my geo chart show a BB height, from ground, of 270.
how does that translate to BB drop?

[ChuckK]

.....

[Ken Robb]

Drop is measured from a line between the axles, down.
I think it's considered more accurate because it's not effected by tire size, and can be specified on a bare frame.

down to the centerline of the bottom bracket I think.

[vqdriver]

that's my sticky
i'm trying to compare frames, but one lists my bb drop, the other the bb height.
so when frame makers list bb height, what's the standard axle height they're using?

[AFS]

BB drop would be the outside tire radius (mounted on the wheel) minus the BB height. A typical number would be something like 337mm for the tire radius (700c wheels with 23mm tires), but this number varies depending on what wheel and tire combination is used as a reference.

[vqdriver]

well, for comparison purposes, it really depends on what's considered "standard" since the listed bb height will be based on that. i suppose that standard would be a 23c tire.

[Peter P.]

Measure from you bottom bracket axle center to the ground, in millimeters.

Measure from either axle to the ground, in millimeters.

Subtract the bottom bracket number from the axle number and you get your drop.

The only variable that can muddy things is the tire size you're using. Most racing bikes use a 23mm tire in determining that spec.

For instance, my front axle is 346mm from the floor. My bottom bracket axle is 270mm from the floor. Thus, my drop is 76mm.

[vqdriver]

Thanks
I was at work earlier was just being inpatient.
Got it now.