Shaving shock pistons

[Elmo]

I bought a set of cheap threaded body aluminum shocks from ebay and they came with slotted pistons instead of pistons with holes which left them severely under-damped. They come with some oil in them but to get them to have any pack at all i had to replace it with 7,000w diff oil. The diameter of the shock body is identical to Traxxas ultra shocks so i want to use the two hole pistons that i have in my parts box. The only issue i run into is that the area between the e-clips is too small for the thickness of the pistons. Is there an easy way to shave the piston down to a thinner size? I can't really hold onto them very well with my fat gorilla fingers so i'm not really sure how to go about trimming them down. Do you have any suggestions on what i can use to hold the pistons while i trim them down? Thanks in advance!

[BigSki]

My first thought is to tape a piece of 320 grit sandpaper to a flat surface, place the piston face down on the sand paper and push the piston around, making figure '8's to evenly sand down the surface. You're basically making a crude lapping block with the sand paper. Keep an even pressure on the piston and keep making the figure 8 shape.

[Elmo]

I appreciate it! I guess i had gotten stuck on thinking about moving the sandpaper around the piston and not the other way around.

[Crawling Calvin]

Originally Posted by BigSki

My first thought is to tape a piece of 320 grit sandpaper to a flat surface, place the piston face down on the sand paper and push the piston around, making figure '8's to evenly sand down the surface. You're basically making a crude lapping block with the sand paper. Keep an even pressure on the piston and keep making the figure 8 shape.

I second that, but also add in some soapy water, it helps stuff sand better albeit more messy! Just make sure you get rid of all the grit off the pistons so it doesn't scour the bores

[Elmo]

I am hoping that by just sanding the face slightly that it would create a ridge on the bore surface. I will pick up some 320 wet or dry paper the next time i'm out and give it a shot. I have hundreds of spare pistons laying around and these shocks definitely need some work, but for the price i can't complain about having to do a little modifying. If i can make them work with the traxxas pistons i will be ordering a bunch more sets to use on other projects too. Luckily i still have my precision drill bits that i used to use to bore the holes in the pistons back in my racing days so i can clean those out if they get clogged during the sanding process.

[Elmo]

I used some 320 wet on a piece of glass and sanded the pistons and they came out good. I checked them often with a caliper so that i didn't remove too much material. After reinstalling the pistons and filling the shock with 45wt, i compared it to the other shocks that i had done that are filled with 7k diff fluid and they felt similar. From here on out if i buy any more of these shocks (this order was for 8pr.) i will just use diff oil and whatever spring is suitable for the application. The performance advantage of switching to a Traxxas piston wasn't really worth the amount of time this took to complete. The slotted pistons combined with the diff oil will fit my needs and i'm pretty happy with how they perform.