Long Travel BS Thread

Bingo! Video is key so we can see how the truck is acting and what it needs

 

Messing around with different A-Arm designs for a potential buggy.
Would I see a performance difference If I went with one design over the other?
The F in the screenshot marks the front of the vehicle.

 

Thanks for the help. Ordered mcm fab long travel kit today

 

this has a lot of good info

 

Awesome, thank you.

 

I ordered one also a week ago.

 

There is so much wrong info here. The tubes have nothing to do with speeds, assuming you're talking about shaft speeds. High and low speed all has to do with the internals, like shims free bleeds and the piston. Tubes just bypass (hence the name)he fluid around the piston. Adjusting them only controls how much you allow to flow around in that given zone.

 

Here is some good info for you guys that can be very helpful if it doesn't make your head spin to much! I didn't write it FYI

There are 3 stages in a speed sensitive damper. Bleed, Valving, and Orifice or low speed, midspeed, hispeed. All are distinctly different and can be seen on a dyno chart. A shock "works" via pressure differentials.
Low speed bleed wholes for the most part are saturated or no longer offering"bleed" above the 4-7 IPS range.
Midspeed is your valve stacks. The range most often used. 8-50+IPS
Highspeed is your piston or orifice design. Most vendors today offer 1 piston and tout "high flow" which is most often NOT a good thing. Bilstein and Fox have reduced flow pistons. King may but doesn’t advertise them. I recommend machining the pistons to accept metering jets.
Custom tailoring pistons is the true way to tune a vehicle. Most people do not have the means or talent to do so, so the next best thing is to play with final shim diameter and fulcrum heights so the piston is not flowing to its potential and you can get an exponential rise in damping force.

I work with OEM shock suppliers as part of my job as a shock engineer and I have a "limited "selection of pistons to work with for their units. That "limited" selection of pistons is 72 different pistons and there are several more I do not get to use. Im talking about a multi billion dollar company making millions of units a year so everything is "engineered" not just a one size fits all beucase at the end of the day Ford, GM, Dodge, etc...dont accept a one size fits all ride.

Im my personal experience working on hundreds of offroad units in multiple applications...one should NEVER need a .020 shim thickness. If needed, either spring rate is off or piston is ill designed for the application. I have so many shocks come to me with a doube stack of .020 shims and when I am done tuning the cars in the field htey will have nothing bigger than a .012 thick shiim combo in them, the car will be more compliant reducing driver fatigue and will be able to take square edge hits and g outs better than it did with the monster .020 stack.

I see a lot of people ask what the set up is for their rig or a starting point on this site and several others. I give the same answer as I do when I get emails or phone calls asking. Start with what you got and tear apart and tune in the field from there and run the car back to back to back until its where you want it.

Shocks are a very simple device...create a pressure differential and appply it to the annular area of the piston and wala...you have a damping force.

A lot of people refer to the "compression retainer" as a "rate plate"...I never understood that. Its a washer to retain the shims from over extending which would be a compression retainer. The first washer in the stack wether a shim or a washer is a "fulcrum washer" as thats the first thing the shims fulcrum over.


Thats about as basic of valving theory I can give.

Shaft speed is important but if a shock runs in the 40-100ips range for 99% of a race but hits 200ips a couple times it would be stupid to tune for the 200ips hit. Thehigh shaft speed blips on the data are also instantaneous...its not like the shock is stroking 200ips for 16" of stroke.

Dirtbike fork speeds are much different than the majority of offroad race cars.

Cavitation is vacuum induced. If your piston moves the column of oil/floating piston but nothing is displacing the fluid under the piston(oil is not traveling through piston) negative pressure is present and the fluid boils. Simple physics. Your radiator is under pressure for a reason…so it boils at a higher temp.

Put a vacuum system over a glass of oil...see how quickly it boils with relatively little negative pressure. Cook soup in the mountains and it takes much longer because there is less atmospheric pressure making the water boil at a lesser value.


Rebound discussion in here has some bad info. On a leaf spring pick up light rebound is a good thing but most often times the reason leaf sprung vehicles use very light rebound is because the spring sleeves are not the correct length or are mild steel and crush if torqued to spec or were installed at droop causing the bushings to not work how they are supposed to work. My prerunner that is leaf sprung in the rear runs a stack of 15s with bypass closed off and works exceptionally well with a modified F53 pack. Instantaneous shaft speeds on rebound are mathematically calculatable with spring rate and unsprung weights being known. Compression is a variable since speed and inputs are always variable. OEM’s like GM usually never test over 50IPS on rebound because the shock will not see that much on rebound. Too much rebound means too much rebound force which means the car will pack up. I see in this thread mentioning packing up and that they need more rebound...they need faster rebound, less rebound damping force etc. Its simple nomenclature. More rebound and faster rebound are NOT the same, they are the opposite. More or less refers to shims or force, faster or slower refers to speed.


Somebody said to put the pistons in upside down...it’s not a bad idea for compression tuning if the rebound can afford the increased flow. If you buy a sway away it may come this way from the factory on accident…I have torn some factory sponsored sway away shocks down to find out parts where in upside down on some but not on others.

One other thing with shock valving...ALWAYS torque the nut to the SAME torque value with a good calibrated torque wrench (Snap On). I use 25-30 ft-lbs regardless on shock brand or size unless a dirt bike shock which goes 8ft-lbs and is staked in place. Overtorquing the nut will change the way the shock works. I have worked on so many shocks that had the nut overtorqued from the factory it amazes me.

Shocks are easy...don’t over think them, don’t complicate them, just play with them until they work how you want. Most times it will not be any off the shelf stack.

Good Luck! I move a lot of parts to guys who rebuild shocks for income or for fun and I hear ALL scenarios, questions and I always do my best not to give any bad or wrong advice to avoid it being spread like wildfire like I see so much of these days.

KISS is the best principle with anything…especially race cars.
Considering all the pistons in our industry flow too much for 99.9% of the applications they are used for...the compression retainer should never need changing or tuning, it should be a constant. Ive never worked on a shock that the shims did NOT hit the compression retainer. Any shocks I tune I use a heat treated chromoly compression retainer as high shaft speeds will plastically deform 1018 unless .25 tall which is ridiculous. When the comp retainer bends, youre screwed for the rest of the race with a failed damper.

If you are running a fulcrum washer of .020 or larger and full pyramid stack more than .040 tall the volumetric cone is greater than the volume the piston will flow most often regardless if the comp retainer is the size of the biggest shim or inexistent.

Controlling shim openings for damping force reasons is done with shim stack heights and fulcrum diameters.

 

I understand most of that, what does IPS mean? is that a rate of movement?

 

Inches per second

 

do you know who wrote this or where did you get it from?

 

It was taken from a thread on dr but I believe it was written by the guy who runs shock seals.

 

Pretty sure that was a post from Kepler on DR.

 

I agree with everything but his valving. Unless you run a low flow piston its pretty hard to keep away from .020 stacks on a heavy truck.

It was

 

I didn't think Half Lap would be understood here.

 

Thanks

^

 

It wasn't half lap that said that.
Here is the link to the thread if anyone wants to do some reading. The first few pages are good but then turns into how would you valve my truck thread.
http://www.dezertrangers.com/vb/shock-tuning-valving/138790.htm
It was the guy from shock seals

 

Isnt that where Kepler worked for a while?