Shocks Sticking?

[h0m3sy]

I recently had a problem with one of my front shocks when on landing off a jump with my SX3. It didn't seem to compress on landing causing the front wishbone on that side to break. It was as if it had just locked up? Has anyone else noticed or suffered the same problem? If so, how did you remedy it?

[mattybucks]

It could be either a bent shaft or the shock body.

Does the wishbone move freely when you take the shock off?

[V-Rossi]

Check the following things:

- Tightness of the nut on the inner hingepin. This sometimes tightens itself, causing binding of the wishbone.
- Shock shafts: these are, on the front, sensitive to heavy or frontal crashes.
- Cartridge: maybe your o-rings snapped and cause a lot of bind in the shock movement.

[h0m3sy]

The car is brand new, wishbones all move freely, I was told to remove the nut as it can, as you said tighten itself, causing some binding. Just came across this from the Belgian GP this year involving Derek McCloskey from Ireland "A manufacturing error known as cold-shock was evident when a front wishbone on Derek’s CAT broke without warning. Phil Booth from Schumacher explained that this effect was extremely rare but was known of." Seems there is a problem with this.

[mattybucks]

Take the shock off, and the spring off, does the piston move smoothly in both directions?

[h0m3sy]

Piston moves freely in both directions, really smooth. I'm baffled as to why this happened. I know it's an easy fix, just replacing a wishbone, but I don't want the same thing happenening again. Everything looks and feels as it should be. Read on RC tech forum that some guy suggests inverting the pistons to avoid this problem of "Cold Shock".

[ASKay]

Originally Posted by h0m3sy

The car is brand new, wishbones all move freely, I was told to remove the nut as it can, as you said tighten itself, causing some binding. Just came across this from the Belgian GP this year involving Derek McCloskey from Ireland "A manufacturing error known as cold-shock was evident when a front wishbone on Derek’s CAT broke without warning. Phil Booth from Schumacher explained that this effect was extremely rare but was known of." Seems there is a problem with this.

I have designed for plastics and do not know the term 'cold shock' unless it is an RC term or an Americanism I am assuming they mean a brittle failure due to cold temperatures (i.e. cold morning), the technical terms if so is referred to as being at the brittle end of the ductile-brittle transition temperature. This is likely to be even more sensitive for materials with a high carbon content, such as wishbones.... some high carbon plastics are brittle at 60 - 70 degrees C, but also are very stiff....

Unlikely to be a manufacturing error, however if material was not packed suitably in the cavity of the tool or there was a weakness (plastic not fused) on a weld line within the moulding then this could cause a failure and would be a manufacturing error.

[bigred5765]

make sure you havent overtightend the nut at the top of the shock, this pinches and restrics the movement,