He said it had less pack. He was referring to the 1.7.

If the 1.7's have more steering, then that is not for me. Like I said on the 4.1 thread, I am going to remove the 1/2 oz I have up front and see if that calms it down and removes the nosing down coming off the jumps. I dislike staying on the gas in the air.

I've tried to explain this before.

PACK = high speed damping.

LOW speed damping affects traction WAY more than pack.

This is the whole reason for tapered pistons and other things that isolate low speed damping from pack. This is why avid makes the 2+2 pistons for big bores 1/10 and GHEA makes the +20 pack control pistons for 1/8 scale.

THAT, is common knowledge.

I stand by my test results. The 1.7s have slower damping when you use the shock oils specified compared to the 1.6s. 1.7 hole with 35 oil is thicker low speed and thinner high speed (pack) than 1.6 piston with 27.5 oil. I can make a video that proves this if there is any doubt.

Wayne

Wayne



Pack is not
High speed damping or what you think & call it ...


pack = the initial resistance to movement of the shock shaft...

Sorry, that's wrong. Pack is high speed damping, plain and simple. It's when the the shock moves very quickly and the shock oil packs up against the piston. It's fluid dynamics.

pack
 

It is wrong to call it high speed damping. Imagine two identical trucks sitting next to each other on a work bench. One has small hole pistons with a light shock oil, the other with large hole pistons with a heavy shock oil. The dampening of the two feel the same when pushed up and down by hand, but when dropped from a couple feet above the table, the one with the large holes bottoms out and slaps the table harder than the one with the small holes. The small hole piston has more ‘Pack’ and is more velocity-sensitive.

Or you could make it really simple... If you're track is bumpy and not a lot of big jumps... Try 1.7's you'll like em!!!

Btw cav on aka tires, round one at crcrc=hurting!

Plus 1

:nod:

Dude, that's exactly what I said. How am I wrong?

What are you talking about? Of course small hole pistons have more pack. What I was talking about was the low speed damping, when you push down by hand. The 27.5 with 1.6 is lighter when "just pushed down" (ie, low speed damping) than the 35 with 1.7 pistons, but the 1.6 piston/27.5 has more pack (high speed damping).

Go back and re-read what has been said, you agreed with me, not disagreed.

Not intending to call you out ..
Trying my best to help ....:)


listen to Pamork

That's what avid calls it. They whole point of them releasing the 2+2 pistons was to separate high speed and low speed damping. This is not the speed of the car, this is the speed of the damping.

http://www.avidrc.com/product/5/acce...cessories.html

I didn't make up these terms. They've been around RC and full size car racing since the dawn of oil filled shock absorbers.

Razathorn: Not saying you are off on this or not, but I am not seeing an explanation of high speed damping equaling "pack" directly on the avid quote or a breakdown like you mentioned here (or similar).

Again, not seeing that exact analogy from what you linked. Do you have something giving a better breakdown of the position you are taking possibly?

Hideeho
I got to agree with razathon on this. But to be more clear, pack is hydrolock. Hydrolock can occur in rc pistons for 2 reasons. 1st is when the shaft entering the shock body displaces more oil than there is room for (rebound). 2nd is when the piston tries to move through the oil in the shock faster than the oil can pass through the holes in the piston (pack). The speed the piston starts to "pack" is affected by the thickness of the oil, diameter of the holes, number of holes, length of the holes, & shape of the holes. All in all "pack" typically happens at a higher piston speed, so refering to it as high speed damping, while not 100% accurate, is a better term than most. I kind of get the feeling everyone is arguing the same point, just using different terms.

The tuning of piston pack can best be illustrated by how various companies use it in the way their pistons work.

The Avid & CSI pistons use several smaller holes & several larger holes to allow less damping at slow speeds so the shock as a whole can react to bumps faster. At higher piston speeds the smaller holes will hydrolock (pack) & only the larger holes will pass oil, thus increasing the damping effect of the piston & creating a progressive feel.

Rcshox has a new piston (ufo) that does something similar to this but in a different way. The ufo is a thick piston that has longer holes (the oil has to pass through the piston for a longer distance). The theory on this one is that the oil will not flow through a long hole as fast as through a short hole, so as the piston speed goes up the damping effect goes up.

Rcshox & MIP seperate the damping characteristics of compression & rebound by using a moving disc to open & close specific holes. This allows more damping as the piston compresses & less as the piston rebounds.

Fioroni does the same as those but accomplishes it by increasing the friction on the side wall on compression & decreasing it on rebound, not by changing the flow characteristics of the piston.

What would be interesting would be to combine the CSI/Avid or ufo concept with the Rcshox/mip cooncept.

waflet: nice explanation!

You guys don't know me well enough (yet?) but maybe I can help explain:

HSC - high speed compression is where a force is moving the piston through the oil at a high velocity. Landing off a big jump is typically where you'll notice it, or if you hit something like a washboard or pothole going fast on the straightaway. RC car dampers do not have an independent adjustment for this but, for example, high end bicycle dampers do and it's usually a separate system than LSC. The "High Speed" in "high speed compression" doesn't refer to the speed of the car, rather the speed of the pistion moving through the oil. We try to adjust for this by changing the size of the holes in the piston and the oil combo.

LSC - this is when the piston is moving through the oil at a lower velocity - like when you hit the brakes and the rear of the car lifts up in the back or when you hit a g-out section at a lower speed or a more gradual radius.

"Packing up" is where your piston hole diameter is too small for the damper fluid to move through the holes quickly enough and your damper "locks up" on compression or simply doesn't allow for the suspension to do it's job. An example could be where you launch a jump way too far, your car lands, the chassis doesn't slap yet your car bounces. This can also happen with your **rebound** where your suspension cannot recover quickly enough from several suspension hits in a row (stutter bumps, etc) and the chassis starts dragging and/or the back bounces around because the suspension "packed up" and is stuck low in the travel.

Again, RC dampers don't usually have rebound damping adjustment, just different weight oils and piston hole sizes to play with so we have to make a compromize between compression and rebound.

Some companies, MIP is one example, have been trying to come up with a way to change rebound damping because it's really a super important part of suspension setup.

What Wild Cherry was referring to is often called "stiction" or stick-tion. That's the higher force required to get the shaft moving through the o-rings and pistons initially. The word comes from "static" and "friction" mashed together. The higher the stiction, the less "plush" your suspension will feel when you move it up and down on your pit table.

Hope that makes sense to you.