What the point of drilling piston to enlarge holes while
 

you can use lower viscosity oil to achieve same result?

I often see people drilling their piston to enlarge the holes then use higher oil weight...:confused:

what is the reason behind having enlarged pistons hole?

Taken from another forum (but worded better than I would have, lol)

"At slow shaft speed a larger hole thicker fluid will feel exactly the same as the equivalent small hole light oil settup. However, at faster shaft speeds, like encountered from jump landings and sharp edges on the track, the smaller hole pistons will "pack" and become stiffer than the larger holed equivalent. It has to do with fluid dynamics.

It's the equivalent to having a slow speed, and high speed compression adjustment on full size offroad shocks. The number and size of the holes in the piston is a rudimentary way to adjust the two independently in RC shocks"

Also an interesting (if involving) read: http://users.telenet.be/elvo/

To summarise very loosely.
Big holes thick oils work well on bumpy rutted tracks
Small hole thin oils work well on smooth tracks with big jumps.


As always these rules are only a guideline and can often be wrong on specific occasions and sweeping statements should never be taken as gospel but in general this is the effects you would expect from these changes.

Balance is always the key in setup!

I found having a much thicker oil made the car easier to drive but the downside was the pistons needed bigger holes to make it a freer shock so drilled them. It made a huge difference and for high grip less holes and medium grip more holes.