Rounded pistons

[JJM844]

Bit of a noob question, but I've read a lot about rounded pistons, how do you go about doing this? And what effect does this have?

[KennyClark]

If you mean tapered pistons then it means the shock rebounds faster than it compresses.
You can get some Ghea tapered pistons from P-dub racing.

[Frecklychimp]

Originally Posted by JJM844

Bit of a noob question, but I've read a lot about rounded pistons, how do you go about doing this? And what effect does this have?

The rounded pistons for TLR 12mm 'big bore' shocks is a team modification done to get an overall faster responding unit which basically copies the older design of coloured Losi pistons used in the past.

here is the method:

Piston mod... these are the tips i got from Andy 'Gnarly Old Dog':

Get an old shock shaft and put it in a dremel (threaded end into the dremel).
Take a piston and press fit it onto the shock shaft - normally the fit is tight enough that you don't need to secure the piston.
Spin up the dremel at about speed 4-6 (my Li-Ion dremel goes upto speed 10)and very lightly, take a piece of 600 grit wet-n-dry to the upper edge of the piston where the side meets the upper face.

What you're trying to achieve is a small radius between the upper face of the piston and the piston side edge. If you look at the old Losi pistons in the old shocks, you'll notice that they have this radius whereas the new pistons in the big bores don't.

Once you've done the top face, stop the dremel and flip the piston and repeat for the other face.

With practice, it takes about 10 mins to do a set of 4 pistons neatly. You don't want to spin up the dremel too fast because you don't want to melt the piston and a 600grit is smooth enough to make a nice surface finish. You can go coarser but the surface finish suffers.

100% recommend this mod, really helps the car react quicker and gives a real advantage keeping wheels planted on bumpy tracks with smoothing out the drive, meaning you can get more power down against opposition.

Tapered pistons are available from a few companies and are worth trying also as a tuning aid... benefit of these is being able to have custom hole sizes/number of holes if buying from companies such as Gurnell RC (recommended)

the rounded edge modified pistons are more subtle than tapers in their rebound reaction but very effective and a cheap modification to do... important note is to be careful sanding near the 'sealing' edge of the piston as it still needs to be maximum sized diameter wise between the new radius 'corners'

Hope this helps

[JJM844]

Thanks for that frecklychimp.