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Rebound while rebuilding shocks?

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Rebound while rebuilding shocks?

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Old 06-30-2019, 01:08 AM
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Default Rebound while rebuilding shocks?

Hi,
First time rebuilding my T4 shocks since I got my car at the start of the year. The oil I poured out was black in colour, not clear like new oil. How often should shocks be rebuilt? And how does shock rebound affect handling? When I push the piston in, some of the shocks bounce out a few mm, and some don't bounce back at all. What is the best rebound for a beginner?
thanks
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Old 06-30-2019, 02:55 AM
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Originally Posted by DanSriratana View Post
Hi,
First time rebuilding my T4 shocks since I got my car at the start of the year. The oil I poured out was black in colour, not clear like new oil. How often should shocks be rebuilt? And how does shock rebound affect handling? When I push the piston in, some of the shocks bounce out a few mm, and some don't bounce back at all. What is the best rebound for a beginner?
thanks
Rebound should be 0 for consistent results. Oil and spring should do the work, not the air in the cap. There are several methods to achieve 0 rebound. Drilling shock caps is one of them. But it's not legal in all racing series.

I rebuild my shocks, if they are leaking on shaft. Leaking means shocks are sucking air in it and losing oil of course.

Black oil in shocks can be two causes: 1. Grease of the shock shafts/sealing in the oil, which is pretty normal, if your shock grease is black. 2. Rubber/silicone seals are disintegrating, which means they should be exchanged to new ones.
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Old 06-30-2019, 04:41 AM
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To eliminate rebound, move piston 3/4 compressed once you've filled with new oil, then screw on cap to seal. Might take a few tries but should work. If shock is fully extended, you get rebound.

On a side note, a little rebound is ok. It won't overpower the spring.
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Old 06-30-2019, 07:49 PM
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I think you want enough rebound to keep the diaphragm from collapsing during a full stroke. The transition from compression to rebound in the stroke should remain crisp and hysteresis (or lag) free. If the diaphragm collapses it takes time to recover if at all. There was a study done that i read on here that was a shock dyno and found that a small sponge in the diaphragm actually helped significantly to minimize an inconsistent reversal of the diaphragm.
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Old 06-30-2019, 08:21 PM
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Surprised this has not been posted yet

Building the new Xray ULP shocks with Zero Rebound
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Old 07-01-2019, 12:10 PM
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Originally Posted by DanSriratana View Post
Hi,
First time rebuilding my T4 shocks since I got my car at the start of the year. The oil I poured out was black in colour, not clear like new oil. How often should shocks be rebuilt? And how does shock rebound affect handling? When I push the piston in, some of the shocks bounce out a few mm, and some don't bounce back at all. What is the best rebound for a beginner?
thanks
Shocks only need to be rebiult every few months, depending on the conditions you race in. EG if you do a really wet or dusty race, you would probably benifit from rebuilding the shocks entirely. Do regularly check that the shocks are free from bubbles, you can do this by listening closely for a squeaking sound as you move the shock up and down.

It's important to have the same amount of rebound on all of your shocks. Sometimes it is better to have shocks with a bit of rebound; it keeps the oil slightly pressurized and prevents cavitation (bubbles) on bumpy sections of track, which may improve the damper perfomace. You can check the rebound between 2 shocks by taking the springs off, extending the damper shafts and pushing the 2 shocks together end-on. They should compress at exactly the same rate. If one doesn't compress as quickly as the other, bleed a tiny bit of oil out of it and repeat the test. (It's tricky to do this without getting air into the shocks!)
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Old 07-03-2019, 05:08 AM
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Originally Posted by DanSriratana View Post
Hi,
First time rebuilding my T4 shocks since I got my car at the start of the year. The oil I poured out was black in colour, not clear like new oil. How often should shocks be rebuilt? And how does shock rebound affect handling? When I push the piston in, some of the shocks bounce out a few mm, and some don't bounce back at all. What is the best rebound for a beginner?
thanks
If you ask Alexander Hagberg, he will tell you to rebuild your shocks before every race, and I do the same. Aside from your oil being black, I've never experienced this as I rebuild my shocks often (oil, bladders and o-rings)...

Shock Rebound: You will get more consistency with zero rebound. Basically by having rebound, the piston/oil isn't helping restrain the spring which will give the car a bouncy feel. Most of your top pro drivers run at zero rebound and will aide in a more consistent shock package at all 4 corners. If the shock shaft is pushing out by a mm, this is still considered a dead shock (zero rebound).
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Old 07-04-2019, 09:23 PM
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Good stuff on damping.

http://www.kaztechnologies.com/wp-co...m-Kasprzak.pdf
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