Seatpost Binder Bolt Length Question
 

I am restoring an old frame and I need to buy a new seatpost binder bolt,
It is a keyed binder bolt. The bolts listed online are listed with lengths
such as 19mm, 22mm, 25mm, 27mm, etc.

What does this length mean? Is it the width between the flanges when
completely tightened?

How do I measure to determine the proper length bolt?

Thanks.

Arvadaman, Measure the outside to outside distance of the seatpost binder, add about 5 mm for the width of a nut and that should be pretty close.

Brad

Bolts are always measured from under the head to the end, so for a Plain bolt that takes a nut you have to add length for the nut.

Allen key binder bolts are measured the same way, the distance under the heads when fully tightened. When buying these you want to deduce a few millimeters to ensure they don't bottom out before the seat is tight.

As Bradtx said, either wat you're comparing to the width of the clamps ears.