Single 2.5" coil over ... Front suspension video

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FasterNU

Mega Member
Jun 28, 2006
6,439
86
48
42
San Diego
#1
What do you guys think?? Not sure if I should make any changes..

Here is a video of the front suspension while going down the road next to Evan Hughes Hwy from Plaster City to the plaster plant. This is going East.

It's pretty damn rough going that direction right now. Lots of square edged holes from them big tire big HP trucks!

I thought I was blowing through my travel and smacking bump stops worse than what this video shows.

http://youtu.be/toUZ-XRR1ak

[video=youtube_share;toUZ-XRR1ak]http://youtu.be/toUZ-XRR1ak[/video]

Here is the current valving.

 

crazyracer

Tres Cuatro Tacos
Sep 27, 2006
2,557
22
38
30
Pacific Beach, CA
#2
Can't tell from videos that close. Full truck videos are necessary so people can see the obstacle size and pitching motion of your truck. What is the ratio of wheel travel to shock travel? That'll help.

Initial thoughts assuming your ratio is ~2:1: Front rebound is too light and nitrogen pressure is too high. We need much more information though.
 
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FasterNU

Mega Member
Jun 28, 2006
6,439
86
48
42
San Diego
#3
OK, I try to get outside video next time... I have some jump videos, and tuff truck.. but I don't think that tells you much. I need to get someone to drive next to me and film on that road.

I think it's right about 18 inches wheel travel on 14" shock for the front. So around 1.25-1.3 to 1.

I have the pressure high to help combat cavitation. I actually started with full 12 stack up front for rebound .... but now as you can see above, it's mostly 10's .... and it's handling better.

I think I have it working pretty good now... but always down for some more opinions and ideas. Where I think I could improve is it seems to blow through the travel up front on hard/fast hits... and smack the bumps real good.

I need to redo them again soon... so this is good time to make any changes.
 

crazyracer

Tres Cuatro Tacos
Sep 27, 2006
2,557
22
38
30
Pacific Beach, CA
#9
No, it's not. With a 20 stack on compression it might need more than 270 to keep it from cavitating. If it starts cooking the oil real quick, go up to 300PSI......
To clarify for other readers:
The act of cavitation does not add more energy into the fluid. The temperature ramps up quickly when you have stiff valving because you're able to drive faster and hit bumps harder. In addition, if caviation is occurring, it lowers the effective viscosity of our oil by introducing air bubbles.That is the main reason cavitation should be mitigated. The quick heating phenomena associated with cavitation is due to the poor conduction of the air bubbles which makes it more difficult for the heat to escape the shock.

But yea I was wrong about the pressure being too high. Cavitation is bad. Bubbles are for baths :D
 

partybarge_pilot

Uno mas Cervesa!
May 14, 2004
9,343
230
63
Easton, KS
#10
To clarify for other readers:
The act of cavitation does not add more energy into the fluid. The temperature ramps up quickly when you have stiff valving because you're able to drive faster and hit bumps harder. In addition, if caviation is occurring, it lowers the effective viscosity of our oil by introducing air bubbles.That is the main reason cavitation should be mitigated. The quick heating phenomena associated with cavitation is due to the poor conduction of the air bubbles which makes it more difficult for the heat to escape the shock.

But yea I was wrong about the pressure being too high. Cavitation is bad. Bubbles are for baths :D

Well, you have a few things kind of correct.......

Cavitation from the piston pushing the IFP and lowering the pressure under the piston is the real problem. As the pressure lowers the boiling point of the oil goes down. Boiling oil is where the bubbles come from. Boiling will also break down the oil very rapidly. Going with a higher static pressure will help keep the pressure on the bottom side of the piston higher to fight off boiling. this is why BP's have the resi out the bottom, to keep constant pressure under the piston to eliminate low pressure boiling. Ohlins worked around this on Pluggers prototype shocks by porting the shaft under the piston and running the oil out through the hollow shaft essentially making them bottom resi. There is no getting around this with a regular top resi CO. Just crank the pressure up and hope for the best......... Or add a BP...........
 
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