REAR DROPS INSPECTION & REPAIR

The rear drops are the attachment points for the rear wheel.  It will not be possible to inspect the rear drops properly in the field.  The rear wheel must be removed to check this part of a frame sets structural and geometric integrity.

With the rear wheel removed, begin by measuring the distance between the inside faces of the drops.  This measurement should be either 120mm or 125mm.  Any deviation from these two numbers is cause for concern. Any deviation from these measurements means one of two things.  Improper assembly at the time of manufacture or damage during the course of the bicycle's life.  And neither need be considered to be a big deal, necessarily.

Why the two possible measurements?  Simply put, there are different rear wheel hub widths which are often determined by how many cogs are included on the freewheel.  A five speed rear hub might be narrower that a six speed hub set, but this is not always the case.  Just be aware that the two measurements are possible and you want the measured value of each to be as close to the specified numbers as possible.  And don't be too surprised if you don't get the 120mm or 125mm measurements.  More often than not, stays get spread a wee bit, exceeding the specified values.  This is relatively easy to repair.  Be also aware of the fact that newer bicycles might have wider drop spaces.  But the spaces are usually in 5mm increments.  That said, a nineties something rear drop space might be 130mm.

Keep in mind that the drops themselves might be twisted or misaligned with one another and it would be wise to measure in more than one place.  Take your time and be as precise as you possibly can.  Take the time to observe and measure the jaws of each drop.  Often times the jaws can be spread a bit and need to be returned to their original shape.  In all the drops I have encountered only one set of forged drops have arrived with spread jaws.  Several pressed steel drop jaws, however, have warranted a bit of attention.

Are the drop-outs parallel to one another?  This can be checked with careful measuring but not all that accurately.  Special tools are required to properly determine if the drops relationship is sound.  For the average person, it would be too expensive to purchase a set of drop tools and it would be best to take the suspect frame to a bike shop for further inspection. 

I was lucky enough to purchase a set of Campagnolo drop tools, for a very good price, quite some time ago.  These are excellent precision tools that clamp into the rear drops, allowing for angular and offset inspections.  These great old tools can also be used to align the drops.  Care must be taken, when using these tools.  Properly used, they are remarkably effective.  Additionally, without such a tool, it would be very difficult to determine if the drops were in proper alignment with each other.

The information offered by the Drop Alignment Tools is immediate.  The drops are either parallel and in alignment or they are not.  Using the alignment tools and applying very small movements, pry or bend the drops back into place, checking alignment after each attempt to bend, or set the position of the drops.  Eventually this effort will produce a set of rear drops that are pretty much parallel to and on center with, each other.

Before each attempt to alter (bend) the drop relationship, loosen each clamp and ensure that it is fully butted up against the end of the drop.  Do this every time before you attempt to bend!

Once the drops are parallel to one another, it is time to turn attention to the frame set itself.  This is where the magical art of "Stringing a Frame" enters the situation.  Magical?  Hardly!

NEXT - STRINGING THE FRAME SET