British-made Shocks For Older Ducatis

Protech have been the go to people for classic car shocks for years, although I don’t think they’ve been doing bike shocks quite as long. I put a pair on my Triumph Speed Twin last year and they’re as good as shocks I’ve tried at twice the price. I’d definitely buy them again.

 

They're a very basic damper. Twin tube design from the 50s with a simple foot valve and a piston with a one way check shim. All the "tuning" is done by drilling small holes in the piston and foot valve. The adjuster is also just a bleed restrictor. They do work quite well but there are a couple of issues. Pro-tech don't Dyno their dampers. They come up with a spec and then they get just built and sold. I've worked on literally hundreds of them, all new. I'd say 10-20% don't work at all and 80% aren't the spec they should be.
The reason for not working is usually the check shim on the piston being crushed because it wasn't centred properly, the piston not being flat and having a poor seal to the shim or the star washer being in the wrong place. The out of spec issue is usually the adjuster. They set them to a fixed condition for a specific spec. Let's say 1 turn out is the desired position and the adjuster gets set at that. Your adjustment range is then available from this initial setting. Unfortunately 1 turn out on one damper doesn't give the same base setting than 1 turn out on the next one. The components are quite crude so without a Dyno you may have 2 dampers that are built the same but give vastly different damping forces. Other problems are crushed capillary tubes, swarf, burs particularly on the small bleed holes (0.25mm -0.7mm, that kind of range) and the oil they use is cheap crap.
We ended up buying them dry and only partially assembled.
That way we made sure they're clean, we drill our own holes that are de-burred. Lube up the shaft seal with special grease to reduce friction (friction on those shaft seals is enormously high anyway), assemble with silkolene damper oil, bleed the damper correctly and ensure the capillary tube isn't crushed/bent and then Dyno the damper to set the adjuster to the correct base setting and adjustment range.
They can be a good damper but you take your chances.
I only briefly looked at their motorcycle offerings and they appear to be over charging. The damper they sell for F2 stock cars, essentially the same design, are £90 each last time I checked.