Doing this is tricky. You would need to find a shock fork that had a)a Bontrager-style crown, so the legs could be removed, shortened, and then replaced, and b) the shock-absorbing mechanism in only the lower portion of the fork legs, so that the top of the legs could be sawed off.
Not many forks meet these two criteria, to the best of my knowledge.
I have an old Answer ProForx BMX shock-absorbing fork on the front of one of my P-38 bikes. It has been shortened from the original 20" size to fit my little 16" front wheel. It works well, and was available on the cheap a number of years ago. I had to create an adapter plate out of chrome moly for the fork in order to mount my Magura rim brake. It is substantially heavier than the Lightning shock fork, but since I ride the flats, I don't worry about this. So far, no complaints. I think I took it apart, cleaned, and greased it a few years ago. Very low maintenance.
These forks can also be used with the 20" ISO 406 wheel without any sawing off of legs. But you will still need to find a way to mount a brake, and replace the stock steerer tube with something long enough to fit the P-38.
I have heard of people taking old AMP forks and modifying them for use with little front wheels. The AMP fork does not have a good reputation for reliability, however. So this might be more trouble than it is worth.
Someone with a used Lightning shock fork might be persuaded to part with it.
Suspension for a person of modest means - or technical ability - is a fatter tire at a somewhat lower than maximum inflation. I would try this first, before hassling with another fork. Might just do the trick.
adapting mtb shock fork to smaller front wheel
Doing this is tricky. You would need to find a shock fork that had a)a Bontrager-style crown, so the legs could be removed, shortened, and then replaced, and b) the shock-absorbing mechanism in only the lower portion of the fork legs, so that the top of the legs could be sawed off.
Not many forks meet these two criteria, to the best of my knowledge.
I have an old Answer ProForx BMX shock-absorbing fork on the front of one of my P-38 bikes. It has been shortened from the original 20" size to fit my little 16" front wheel. It works well, and was available on the cheap a number of years ago. I had to create an adapter plate out of chrome moly for the fork in order to mount my Magura rim brake. It is substantially heavier than the Lightning shock fork, but since I ride the flats, I don't worry about this. So far, no complaints. I think I took it apart, cleaned, and greased it a few years ago. Very low maintenance.
These forks can also be used with the 20" ISO 406 wheel without any sawing off of legs. But you will still need to find a way to mount a brake, and replace the stock steerer tube with something long enough to fit the P-38.
I have heard of people taking old AMP forks and modifying them for use with little front wheels. The AMP fork does not have a good reputation for reliability, however. So this might be more trouble than it is worth.
Someone with a used Lightning shock fork might be persuaded to part with it.
Suspension for a person of modest means - or technical ability - is a fatter tire at a somewhat lower than maximum inflation. I would try this first, before hassling with another fork. Might just do the trick.
Safe riding,
Joel Dickman