Shock Tuning 101

[BamaTJ]

I get a lot of PM"s and questions about shock tuning, so I wanted to post up some info. I really enjoy messing with shocks to dial them in and have had all types of shocks apart. I am going to make a few subjects on the different types of shocks, how they work and how to work on them.

Air Shocks

How They Work â€" Air shocks are completely self-contained. They come in 2.0 & 2.5” diameters and various lengths. They are extremely lightweight, most come in under 10lbs per shock. They use Nitrogen (N2) to set ride height and Shock Oil to set spring rate. The more N2 you add the more ride height you get, the more Shock Oil you add the stiffer the spring rate and vice versa. Air shocks have a maximum sprung weight they can carry. Most 2.0’s are between 800 and 1,000lbs max, and 2.5” are 1,200 to 1,500lbs max on average. I would not recommend getting anywhere near these max numbers, as performance will be greatly effected. You see air shocks on many comp rigs because they are lightweight, easy to package and they react/cycle very quickly. Air Bumps or N2 Bumps are the exact same concept as air shocks; they are in fact mini versions of them. They come in the same diameters and smaller lengths. The same applies to bumps in terms of adding oil and N2. Also inside the shock you have valve stacks that control how fast or slow the shock cycles/reacts. You have two separate valve stacks, one is for compression (uptravel) and one is for rebound (down travel). You can adjust them separately to truly fine tune your setup. Valve stacks are simply shims in various thicknesses, and most manufacturers use their own system for naming valves. An example of what Fox uses is 20/40. First number is compression, second is rebound. SAW uses .09/.12 and so on. Most shock manufacturers etch the factory valving specs on the lower shock end. If it is not etched, then they used the stock valving from the factory, so you need to call and find out what it is.

How to Service â€" To add N2 (Ride Height), simply remove all the N2 in the shock at full shock extension. Then add your N2 charge. Regulators on N2 bottles are rarely accurate. I found this out at KOH because we put what we thought was 200 psi in our Bumps, turns out it was only 140psi per the Bilstein Tech’s gauge. So if you have air shocks, invest in a good N2 Tank/Regulator and Fill Gauge. To add Oil (Spring Rate), remove all N2 and unbolt the Schrader Valve. Add oil with a syringe and keep track of how much you add. You can do this on the rig at full shock extension or upright in a vice. If you need to remove all oil and start over, pull the shock and cycle it upside down over a catch can. Most use 5wt Shock Oil, but you can stiffen them up some with 7wt oil. I would stay away from 10wt oil.

Opinion â€" Air Shocks are a great bang for the buck and work great on slow speed crawlers. At high speed they will beat you to death, unless you have 2.5’s which seem to work much better due to the increased oil capacity. I had air shocks on my rig when I got it and it crawled great, but riding around perimeter trails was rough. I was about 600lbs of sprung weight in the front and my 2.0’s hated it and required max oil to keep from bottoming out.

Fox 2.0” Shipped Oil Specs (Ask Vendor for MAX Oil Level)
http://www.polyperformance.com/shop/Fox-2.0-Air-Shock-p-102.html

Fox 2.5” Shipped Oil Specs (Ask Vendor for MAX Oil Level)
http://www.polyperformance.com/shop/FOX-2.5-Air-Shocks-p-182.html

Sway-Away Rebuild Guide (Thanks to JRich)
http://www.swayaway.net/joomla/images/InstallInstructions/9920_2and2-5-AIRSHOCK_R-R.pdf

Air Bump Tech on PBB
http://www.pirate4x4.com/forum/showthread.php?t=680275&highlight=fox+travel+air+bumps&page=2

Air Shock Tech from PBB
http://www.pirate4x4.com/forum/showthread.php?t=655045

N2 Fill Gauge
http://www.polyperformance.com/shop/Nitrogen-Fill-Adapter-p-286.html

 

[CheapJ7]

thanks for the links Matt..
Be puttin them to use in a few weeks

 

[BamaTJ]

Coilovers

How They Work â€" Coilovers are a different animal and are a big improvement over air shocks for a true dual-purpose setup. They come in the same diameters as air shocks, 2.0, 2.5” and even 3.0". Coilovers are designed to accept coil springs over the shock, hence the name. The body of the shock is threaded which allows you to add the spring adjustment collars and the dual rate stops to the body of the shock. The spring adjustment collar lets you adjust the ride height by simply turning the collar up or down. Turning the collar down the body of the shock increases ride height, turning it up the body decreases height. The dual rate stops allow you to adjust when the springs come into play. The idea behind this is that you add 2 coils to each shock and they both have different rates (Stiffer rate on bottom, softer rate on top). So you can have one rate for high-speed running and another rate for crawling. Best of both worlds and you can tune when the rates come into play based on the travel of the shock. So a coilover handles spring rates and ride height via the coils that ride on the shock. If you want to change rates just throw on different springs. Most shops (like EOR) have a spring return program so you can try out a bunch of springs and find what works best for you. Springs are .5” bigger diameter than the shock diameter. So a 2.0” coilover uses 2.5” diameter springs. Coilovers are either Emulsion or Remote Reservoir shocks. Emulsions are self-contained, remote reservoirs have an external reservoir to increase the oil capacity. More oil = less heat, and I would never recommend anybody buy an emulsion coilover. Also inside the shock you have valve stacks that control how fast or slow the shock cycles/reacts, just like in an air shock. Read the air shock section for info on vavling. Manufacturers include: Bilstein, Fox, SAW, King, Ballistic Fab, Radflo, FOA, etc. Spring Manufactures include: Blue Coil, Eibach, King, QA1, Hypercoil, etc.

How to Service â€" Since coilovers have threaded bodies, they tend to rust and build up dirt easily. Spraying them down with WD-40 every now and them is a good idea. You do not need to adjust the oil or nitrogen pressure inside the shocks. They ship with a factory amount of oil and nitrogen (usually 200psi). You can play with the N2 some if you like. An example would be if your rear end was very light you might want to run 150psi instead of 200psi. To re-valve the shock, pull it off the vehicle and remove the N2 charge. Then mount it upside down in a soft jaw vice and remove the lower rod end (unscrew) and then remove the shaft from the body and pull it off. Most shocks have different ways of retaining the shaft inside the body, but all manufacturers will send you directions on how to disassemble the shocks. Also if you don’t feel comfortable doing this you can send the shocks back to the manufacturer to change valving and rebuild for a small fee.

Opinion â€" Coilovers are a great dual-purpose shock, I would say that 75% of the team at KOH were running some form of coilover. Just like air shocks, the bigger the diameter the better the performance. The downside is that the 2.5 and 3.0 shocks also cost a good bit more. Coilovers are designed to handle more weight, so for bigger rigs they are must. They weigh a good bit more than air shocks because they have two springs per shock, so the weight and the cost adds up quick. They are very easy to adjust, with ride height changes just involving a few turns of the adjustment collars. Several factors can greatly change performance and ride, which can be frustrating at times. Springs, dual rate stops and valving all greatly affect the performance, so bank on some trail and error time initially. I like to setup springs with a heavy lower, and a soft upper. I feel that this gives a nice balance, and truly maximized the dual rate approach. So I have a large gap between my spring rates like 100/350. For a desert truck you do not want as drastic of a difference in rate because you are really just worried about speed and those rates are drastic change from each other. So to get a similar rate (Based on my setup above) for a desert truck, I would run maybe 175/200. All depends on application and feel.

Coilover Re-valving
http://pirate4x4.com/forum/showthread.php?t=539980&page=8

Bilstein 9100 Series Rockcrawler Coilover Rebuild Guide (Petersen's 4 Wheel & Off Road Magazine)
http://www.bilsteinus.com/9100rebuildstory.pdf

Dibble’s Re-valving & Spring Rate Changes
http://www.pirate4x4.com/forum/showthread.php?t=259197&highlight=spring+rates
http://www.pirate4x4.com/forum/showthread.php?t=234112&highlight=coilover

DLux Spring Rates & Shock Valving (Very Good, I learned a lot from him)
http://www.pirate4x4.com/forum/showthread.php?t=507545

 

[BamaTJ]

There are other shock types out there, but I don't know much about them so I am going to refrain from going into detail about something I don't know.

ORI Struts (AKA Cloud O' Titties)
These are pretty new, and Kelly can chime in with more detail. All I know is that they are similar to an Air Shock, except they have two seperate N2 chambers, one above and below the piston. They have a much larger diamter and you can tune a lot with just adjusting pressures in the chambers. You can also add oil, but it is rarely needed. They have a built in valving bumpstop, which is basically a very stiff valving stack at the very bottom of compression that acts as a bumpstop. Becaue of this it is very hard to bottom an ORI out, but it is possible. They have cooling fins in the body of the shock to dissepate heat, and the company is constantly revising and improving the design based on real world feedback. They are pricey, but the sell is that you can eliminate bumps and sway bars, so it turns out costing you less. Kelly is the man on these, he sells them for a good price and has 1st hand knowledge with them.

Bypass Shocks
I cannot pretend I know much about these other than they are used in desert racing and lots of cars are going to them for KOH. I know they have a bypass tube and they are very easy to adjust because you don't have to remove the shock, just change the bypass on the rig. Woodlee has them on his rig, maybe he can chime in. I know EOR Jimmy has a pair at the shop also. Again, these are kinda over my head so I really cannot add much other than they are cool and expensive!!!

 

[BamaTJ]

Real World Coilover Setup Example

My Rig

Corner Weights
DF = 1094
PF = 1093
DR = 714
PR = 691
Total = 3592

Sprung Weight
Front = 631
Rear = 325

Front Uptravel = 5"
Front Springs = 100/350

Rear Uptravel = 7"
Rear Springs = 80/250

I like the way mine rides on rough stuff and crawling. The rear was pretty stiff before but I dropped the main spring down from a 350lb. I have setup springs for several rigs include Joe's old rig (wood's buggy) and it always rode good.

 

[CheapJ7]

http://www.swayaway.net/joomla/images/InstallInstructions/9920_2and2-5-AIRSHOCK_R-R.pdf

suggest this be added to the airshock section
Has shipped oil volume and max oil volume for all swayaway shocks
Also includes detailed instructions on rebuilding, revalving, and tuning...

 

[CHASMAN9]

How can I tell what rate springs I am currently running? Are there marks indicating what rate they are anywhere? On our last trip, John G noticed that my rear bumps barely even touched due to the rear setup being very stiff. I have also noticed that my rear suspension is very rigid without alot of travel and so we marked the shafts and measured later. They were only traveling about 1 1/2" confirming there lesser travel. I believe my SwayAway shocks are running 300 psi which I see now is much higher tha nsuggested. This is why I get alot more rigid bump without control and less crawl rate. Any suggestions? G

 

[BamaTJ]

Lots of springs have the rate printed on the coil, look around the springs and see if you find anything, it is usually written in white. If your springs are very stiff, then your shocks are not going to compress very much, so lower the spring rate. You need to get on John's scales to determine your rear weights. N2 pressure will also increase the firmness of the ride a lil bit. On a stiff spring setp, try to run a lower pressure like 150, it will help a little. My rears are 150psi. If they are still too stiff after lighter springs, we can revalve them and mess with the 2nd bleed srew, but it is probably not needed.

 

[CHASMAN9]

Lots of springs have the rate printed on the coil, look around the springs and see if you find anything, it is usually written in white. If your springs are very stiff, then your shocks are not going to compress very much, so lower the spring rate. You need to get on John's scales to determine your rear weights. N2 pressure will also increase the firmness of the ride a lil bit. On a stiff spring setp, try to run a lower pressure like 150, it will help a little. My rears are 150psi. If they are still too stiff after lighter springs, we can revalve them and mess with the 2nd bleed srew, but it is probably not needed.

Thanks Matt, I think Turbo Joe still has his N2 kit. I will see if he will loan it to me and adjust my pressure down to 150-175. I have always felt that the rear is like riding a John Deere down highway 65. I also believe that this why I cannot crawl some rocks due to the fact my suspension is so stiff it will not give and let the tires bite more. It is like trying to drive a 2x4 over a bowling ball, you have to throttle up to get over it. Does this sound odd to you? I want to dial this in better and be able to crawl more than just point and shoot. G


Oh, I believe that my coil overs were painted by Darryl when he did the rear 4 link.

 

[BamaTJ]

I want to dial this in better and be able to crawl more than just point and shoot. G

I know where you can get some red labels... Might be worth asking Darryl what the rates were. I think him and Bryan use stiff rates and always set them up the same, or close to it. Lower rates and less nitrogen can only help.

 

[CHASMAN9]

I know where you can get some red labels... Might be worth asking Darryl what the rates were. I think him and Bryan use stiff rates and always set them up the same, or close to it. Lower rates and less nitrogen can only help.

Red Labels you say...?

Darryl wouldn't remember what he put on. I believe that he put on used stuff and painted them up anyway. I will try the N2 and see how that works. G

 

[John Galbreath Jr.]

I would suggest taking almost all the N2 out of the bumps, adjust the coilovers, the add N2 back to the bumps. My coils have the number written with an electric pen type engraver on the end of the coil. I have to take them apart to read it.

 

[BamaTJ]

I would suggest taking almost all the N2 out of the bumps, adjust the coilovers, the add N2 back to the bumps. My coils have the number written with an electric pen type engraver on the end of the coil. I have to take them apart to read it.

John has a good point, if the bumps have too much N2 that will make it rough and not allow the rear to cycle also. I would try 200PSI in the bumps and probably 150 in the shocks. I have an N2 setup if you want me to bring it. I would suggest a quality fill gauge cause my regulator is innacurate. Poly P sells a nice one: http://www.polyperformance.com/shop/Nitrogen-Fill-Adapter-p-286.html

 

[BamaTJ]

I updated the original posts to includes JRich's link and another link I found on how to rebuild Bilstein Digressive Shocks..

 

[CheapJ7]

I updated the original posts to includes JRich's link and another link I found on how to rebuild Bilstein Digressive Shocks..

 

[Travis]

I would try 200PSI in the bumps and probably 150 in the shocks.

I have found that 200 in the bumps is way too much for my rig, more like about 80-100 works well. The shocks I keep at 200 psi. With the bumps at 80-100, I still can't bottom them out unless I hit a sizeable(4-5 ft in the air) jump.

 

[BamaTJ]

I have found that 200 in the bumps is way too much for my rig, more like about 80-100 works well. The shocks I keep at 200 psi. With the bumps at 80-100, I still can't bottom them out unless I hit a sizeable(4-5 ft in the air) jump.

Just wait till you get to the hammers, you will change your mind. I had 100 in mine when I went out there and when we upped to 200 it was like night and day...

 

[CHASMAN9]

I would suggest taking almost all the N2 out of the bumps, adjust the coilovers, the add N2 back to the bumps. My coils have the number written with an electric pen type engraver on the end of the coil. I have to take them apart to read it.

John G you were behind me in TN, what did you see my suspension was doing? Were the coilovers and shocks working properly and the bumps slowing things to a halt? I still feel like my suspension is very stiff even when I am riding on the street or a 1 trail. It is probably a combination of both being too high of pressure. I would still like to find out what my C/O rates are as well. MattO, I will take you up on the N2 kit and will see you tonight at the meeting. I know this is the reason that when I approach a rock I cannot just roll up to it and drive over it. The suspension is not flexing enough due to no absorption of the shocks. I have got to make some changes and dial it in. NO KOH for me, just more competitive on the local trails hopefully. Thanks for all the input, G

 

[John Galbreath Jr.]

John G you were behind me in TN, what did you see my suspension was doing? Were the coilovers and shocks working properly and the bumps slowing things to a halt?

I did not notice anything out of the odrinary until I pointed it out that you had not rubbed the mud off the bumps in a while. This was after you were beating on that ledge. Should have fully compressed (or close).

 

[CHASMAN9]

I did not notice anything out of the odrinary until I pointed it out that you had not rubbed the mud off the bumps in a while. This was after you were beating on that ledge. Should have fully compressed (or close).

So if they were not meeting the bumps, that should indicate that the shocks have to much ooomph.




Gonna get me a driill out and fix er now.