I just picked up a LT ATVR Pilot and though I havnt had a chance to take to the dunes, I did test ride in a dirt field and I noticed the rear suspension is a little stiff. I mainly ride in sand like Little Sahara sand conditions. The Pilots rear spring set up is with 150# mains and 125# tenders. I weigh 175 pounds and like to ride aggressive in trails and cruise the bowls. Im looking for some recomendations on what poundage springs woud be good for me. I know Mark in Ponca City runs 125# as mains and 100# tenders, he says they work good for Little Sahara Oklahoma riding conditions. Summit carries a line of different springs that are 12" X 2-1/2 ID.

I read that post. Pilotman said 100 over 100 was still too stiff?? maybe that was due to he needed revalving. Any reason you went with 95# over 100#, availablility at the time? Ill just have to pick up a pair of 100 lb. and experiment with the 125 and 150 as the main and 100 for tender.

Stixs here is some basic rate info for spring choice. Here is a pic and a pdf of the pic. Hope the info is correct. Some one can link you to a spring calc.

Adnoh where do you find the time to record all the information you have? Very impressed!

Thanks Mudd. I own my own business and I use the time to purge my brain after a stressful day,week or month. Plus I like the what if. The chart was pretty easy based off the info others put on here and link to it using the basic dual rate math. Put it in a spreed sheet copy and past then save as a pdf. It gets better if Stix and others are willing to share some numbers to enter into my spring rate chart. I think other may find it interesting the correlation between the numbers other than "that's what I did". The "what I did" is important as it tells a story of the shock shafts in action based on poundage of the springs rate and settings. He's a tid bit for the head to wrap it's self around. The combined rate in the chart is based off of the main and tender rates. however it tells you nothing more than that.

What if I told you the bottom out poundage for a 150 over 150 is the same as a 95 over 150 if that's all you did was change the tender spring and left the rest alone. The ride would change though, but how? Could be wrong though.

So who want to play. Stix you posed the question so lets do some math and have some fun.

Based of the above at a ratio of 1 to 1 the bottom out poundage is right around 1200 lbs. Now what if I told you I could change the spring rate via the chart with an 100 over a 125 and made around a 2" adjustment and maintained the 1200 lb bottom out poundage. AHHHH softer through the combined /main rate and yet maintain bottom resistance or make an 1.2 adjustment in another area and achieve the same thing and still improve the ride. Is it the ride your looking for, don't know more to play into it.

Disclaimer:
Remember this is based off some Back Yard Hacker math so the information is for discussion only. Heck not a professional in any way.

This is great. I cant wait to see what you guys figure out is the bast set up for the LT pilot. Mine is a little stiff on the top end. All ATVR

, if anyone wants to buy a set of new never used ATV racing top rear arms I have a set I will never put on a pilot that are powder coated silver. If not I will cut them up to use the piece that the ball joint goes in to. Spring rates I have read seem very to extremely high to me, I went with a 100 on the bottom with a 60 on top of a 12 inch fox coilover with 14 true inches of wheel travel and the wheel moves up and down the entire length of the shock with 60 lbs pressure in the resivor with a 230 pound driver. anymore the pilot is to lite to move against the gas pressure alone with a 7/8 shaft never mind the springs. Mine would blow threw the 10 and a half to 11? that ATV lets you have and would blow the top rear pivots rite off the pilot the first big hole I would hit unless I put the shock spacers?? he requires which defeats the purpose of Long travel and would cause trouble elsewhere then. I started out with a 130 with a 80 up top but could not get the wheel to go up more than 6-7 inches on the big hits, then tried a 120 on the bottom which gave me a couple more inches of movement then went 110 with 70 on top which got me close but not all of the shock then tried my present set up which I will stay with after working with nitrogen pressures I am able to use the duel rate set up fox intended. It does not mater how much travel you think you might have or who made it if the shock does not let it move what good is it? My buddies ATV racing pilots were lucky if the wheels moved 3 total inches past ride hight in giant hits and was extremely harsh to ride in, front and back. He bought them that way and paid a fortune, they reacted off even the smallest of rain ruts. Maybe if your jumping the empire state building it would be the set up but for all round riding it hardly moves. Next week we are going to run and experiment with his ATV pilots, will post what we come up with. I think 110 70 will work best on a ATV set up.

Dave-Co supplied some very good info in his post. As I read though it I payed attention to what adjustments he made and why. One should be cautious when playing with gas pressures. There is is a point where the pressure can be too low and cause cavatation with in the shock body effecting the shock ability to control the shafts motion. I'm not saying you can not adjust it just be care full on the amount. I did go back and read though his build and made note of his spring rate/rates he used on his shock.

He mentioned rate alone will not do it and make a valid point to consider. When one changes rates one should consider and or know the effects upon the setting at which the shock is set. The two most important adjustments I would say when discussing rate/rates would be crossover and preload. In short do not just slap a new spring or set of springs on it at the setting you had with out knowing there effects/change. Since in this discussion were dealing with is poundage lets look at that alone and get into valving etc later.

What should one consider with a spring change. The common answer I have read is softer ride and to quote a few other " stiff as hell". So most change the springs around via flipping them or changing rates and locations main and tender.

Yes, the new rates make a difference in static sag as you go softer in combined rate if you leave the preload adjuster and cross over in the same place. However that does not tell the whole story on what you did. Again I will stress right now I,m only taking into account the spring rate so purge the other out for now

So word of the day static sag, and burn it in combined rate changes static sag.

So what if I flip spring? The combined rate is the same and NO static sag change has accrued. Note here no other adjustments flip only.

If the combined rate is the same then why does is seam to be a softer ride? As mentioned above the two adjustments I fell important with a sprig poundage #1 preload and #2 crossover. Burn these in.

OK, answer the question! (If the combined rate is the same then why does is seam to be a softer ride?) First of all lets look at the springs and there rate to which most ATVR shock come with which is as 125 over 150 or a 150 main and a 125 tender and no matter which one is on top the combined rate is the same. Second, let assume for a minute when you flipped them to 150 over 125 or a 125 main and a 150 tender and left you preload at zero and your crossover at lets say 4". We have to look at how far each spring move under the combined rate before the crossover takes place. What were looking for here is SHAFT TRAVEL at CROSSOVER OVER POUNDAGE or what I call ST at COP. This is where you cross over poundage has changed and the amount of shaft travel has also changed.

That's enough for now gotta go to work.

KEY WORDS:
Main spring rate
Tender spring rate
Combined rate
Preload
Crossover
Static Sag

Had some dinner and time for some more.

Back to the flip (150 over 125) with no other adjustment. The combined spring rate which is about 68 pounds no matter how you stack them. The difference is how far each spring moves at 68 lb rate or 68 pounds per inch. The 150 pound rate spring moves for that one inch of deflection around .4533 of an inch and the 125 pound rate spring moves around.5444 of an inch. keep in mind the shock shaft has moved 1 inch. If we apply the above what if and the cross over is at 4" than the 150 Tender Spring would need to be compressed (deflected) with 600 pounds before it transitions to the main spring.

But how far has the shock shaft moved?

If the cross over is at 600 pounds than we can take the COP ( Cross Over Poundage) and divide it by the combined rate we get shaft travel of 600/68= 8.823 inchces. Lets compare it to the 125 if it was the Tender spring 125x4=500 or COP of 500 and then divide it by 68 and we get 500/68=7.3529 inches of shock shaft travel. Now we need to look what shaft travel is left at what rate for the main spring.

150 (tender) over 125 (main): ST at COP=8.8, 12-8.8= 3.2 inches of shaft travel left before bottom out 3.2 x 125=400
400+600(COP)=1000 BP( Bottom out Poundage)

125 (tender) over 150 (main) ST at COP=7.3, 12-7.3= 4.7 inches of shaft travel left before bottom out 4.7 x 150= 705
705+500(COP)=1205 BP (Bottom out Poundage)

You can see how it's softer, not much, but softer. Now you can change one of the setting or both and get each to bottom out at 1200 or 1000. It's about shaft travel and the rate though out it travel which gives us the feel of softer based on spring rate and the preload and crossover settings.

Time for some T.V. more later on preload and crossover. Hope I did the Back Yard Hacker math right if not some one please let me know.

Damit Rich

My head hurts...
Good Info thou - thanks

I just want to know if I drop a 600 lbs LT Pilot from 12 ft to ground
what spring combo and n20 psi will keep it just short of bottoming out...

IMO - anything over that height is just asking for trouble...

DR

Sorry for the headache FL670. I will have to do some major math on that one which may be over my ability to calculate correctly. With that being said IF and I mean IF we bring valving into play which I would like to keep out of this topic for now until we can wrap our head around spring rates and there adjustments I see no difference between the drop and hitting a two foot square edge bump at 50 mph. I pretty sure it's a force,mass, acceleration and velocity question. Talk about a headache. Either way I would not want to be in the seat with a cheap set of shock on my machine. I'll throw a what if myself out there. If we take the ATVR lt pilot with 68 pound combined rate I would be it would do just fine "IMPORTANT INFO NOW" I say 68lb rate because of the 125 over 150. We can stiffen it up to its max for coil bind at BP and then valve the hell out of it. This bring shaft VELOCITY into the equation not just shaft travel. Most likely you will blow the seals out the shock if over valved. If your shock is over valved and you under spring it. The increased load can over heat or over stress the shock and say good by to the seals or lose it's ability to control shaft velocity. This is another reason to watch you pressure. With the high velocity the valving will so soft on you and blow through the rest of the stroke then relying on the spring alone and "ouch my back". Ok not just the spring alone It also has a bump stop on the shaft which adsorbs energy as well and can be used in the BP. The bump stop is there to soften the BP. The bump stops come in different rates as well.So I say drop it and watch what happens. Now go out and hit a jump at sky it 12' and land flat straight down that's another issue and I say better you than me. I will see if I can come up with an answer though.

Now lets look at preload just what is it and how can we us it for adjustments. What we need to look at first is the spring/springs and there rates. The spring as you hold it in your hand has a free length or it length at a relaxed state. In the case of the ATVR set up in the example. lets use a 12" spring or better yet two 12" springs one tender and one main for a combined rate. Each spring held in you hand measures twelve inches or 24" total. We are going to call this a SPRING STACK. The stack consist of two 12" spring and a spring spacer. The spring spacer does two things it joins the the spring together to form a stack and also acts as the cross over. In the case of the AXIS shock which has a threaded crossover collar to form the cross over point to the main spring in this dual rate spring stack. I mention this because of the thickness of the spacer between the two spring which must be included in you spring stacks free length. If memory serves and if not I will use 1/4" or .250 for the thickness. Our spring stack now measures 12+12+.250=24.250 inches. This is our Spring Stack Free Length. There is no load on this stack at this time or no forces acting upon it. When we install this stack on our shock the shock is in our hand fully extended then our threaded preload ring are rundown until they touch the top of the spring stack. This is Zero Preload. Why is this, well the spring stack still measures 24.250 inches with the shock fully extended. Now let's look at some preload just so we now how to calculate it. First time for a what if. What if my stack does not measure 24.250 after I ran down the preload rings and the main spring is not sitting flush or even sitting down on the springs perch at the base of the shock. This may tell you you crossover is touching,the spring separator is hitting the crossover collar and will need to moved up. Now that this is confirmed and you made an adjustment and please start your adjustment of that cross over collar for this shock at 1/3 of its Tender springs length. This should give you some distance between you spring spacer and the cross over collar on the shock body.

If we take the above mentioned combined rate or 68 pounds per inch for the 125/150 spring stack it's pretty easy to find the preload poundage. Based on the 68 pound per inch if you change you spring stack from 24.250 to 23.250 you have changed the spring stack free length by one inch or 68 pounds thus adding 68 pound of preload poundage. You will also see the distance from the spring spacer to the cross over collar get shorter as well. Take note of this as it comes into play later.

You can also see why I say just changing the springs with no other adjustment can play a big part in how the shock works based on the rate of the spring. An example of this is going to a 100 over 100 or a combined rate of 50 pounds per inch. If you leave your spring stack at 23.250 you only have 50 pounds of preload. What this will do is change many aspects of the shock from the static sag to the crossover poundage to bottom out poundage.

Well more later need to go to work.

Time some more on preload.

Since the base formula is pretty straight forward we need to look at what the preload effects. The preload poundage as discussed above compresses the spring stack from 24.250 to 23.250 and in this case 1” for 68 pounds which is the combined rate or the dual rate spring set up. We also know the crossover was set at 4” with the spring stack at 24.250 which is it’s free length with ¼” or .250 spring spacer and two 12 inch springs.
Two of the effect which have taken place is the cross over collar distance from the spring spacer has changed and the force acting on the spring stack went from 0 to 68 pounds.

What effects does this have on the shock?

Since we’re looking at poundage and shaft travel let’s look at those. First let’s look at the effect on the crossover point (poundage). As discussed before each spring moves a certain amount for the combined rate of the two springs so I’ll skip the math and go for the answerer. The Main Spring (150) has been compressed.454545 of an inch and the Tender Spring (125) has been compressed.545455 of an inch for a total of 1 inch. Since the crossover poundage is based on the movement of the Tender Spring and the cross over point which is now closer than before at zero preload we must find the new crossover poundage.
Before the preload change we were at Zero so we took the 4 inch setting and times it by the Tender (125) and came up with 500 pounds.

After the change we take the .454545 of the Main Spring length change and subtract it from the .545455 of the Tender Spring length change, which is 0.09091 on an inch then we subtract it from the 4 inch we had at zero and come up with 3.90909 inches then we times by the Tender Spring rate of 125 and come up with 488.63625 and then we must add the preload poundage which is the force the shock must first over come before shaft travel can begin. When we add the 68.18 to the 488.63625 we come up with 556.81625 of COP or Cross over poundage.

Now for the flip with the 150 over the 125 we can do the same math which I will save you from since I have a cheat sheet or spread sheet to help me. Even with the 68.18 pound per inch combined spring rate remaining the same the new COP is 681.8182. What a huge difference in poundage just from a flip and one inch of preload.

Next will look at the Shaft Travel for both examples and then bring the Static Sag into it.

OK I get it, Your reading all this from a book. If not you should be writing one.

Either that, or he has a pornographic memory

I thought we all had porongraphic memory

One of the things I forgot to ad I had to take down both compression valving and rebound valving to darn near nothing, I think I have 10 compression and 15 rebound on the fox valving chart, and I did some work on the piston also to let it flow better. Packing in the rear was really bad at first with only a lite 24-11-10 ATV tire to control on rebound LOL and the pilot being so lite that just charging the shocks to foxes recommended 200 PSI would raise the rear ride height by several inches on a coil over shock! combined with to much valving would keep the shock from working the way you would want it. With 60psi the ride height stays where I put it, anymore it would start lifting the rear which the shock is not designed to do that, only air shocks are made to do that. the shock still does what it should do. I would never run 60psi on a heavy machine but on this feather lite machine works fine. I can charge large desert woop sections out at Barstow where they hold off road races, miles and miles of them and the shock never fades or changes the way it works. Shock oil is very important also, all fox shocks, including bypass racing shocks and air shocks come from Fox with piss poor oil in them, the blue oil, I cannot for the life of me understand why they put that crap in there shocks when they sell the red high temp no fade no foam oil that all racers that know anything change there oil to. I changed all my front and rear Pilot shocks to the red oil which gives the shock consistency, does not change the ride after a couple of miles like the blue oil does, once the blue oil gets warm or hot it foams up and changes the way the shock works leaving a hard way to tune. On my race cars I run 1 shock per wheel, a 14in fox 2.5 4 tube bypass shock in the rear and a 2 inch shock up front, with the red oil at say a Mint 400 which is one of the roughest races there is the car feels the same at the start middle and end of race, I know some have there own choice for oil but the simple fact is foxes red oil does not go away and is cheap to buy. I have many friends that run Bilstien or sway away and King shocks, but run foxes red oil in them!

Dave-Co, more good info on your shock set up. Hope you do not mind been taken notes. You say you alter the valve its self. Open it up by chance for better flow rate around the crimp. Man I can not wait to see the video and put in my top ten.

halorising, thanks for the kind words as most you read is based off what I read and do. I had to learn some where. I just to explain it in a way others can understand. Most every set up articles I read does not say how other than follow the guide lines with out the math. I just took what i learned and put in a speed sheet to make it easy on my self. I hated to stixs get some spring and bolt them up and have it worse or better then it was without understanding why.

Nick R, what can I say I do remember most of what I read and see. I'll leave the visuals to yourself. Plus your funny as Heck.

Here is my last post for this and next week as of a heavy schedule. Keep all the info coming on the shocks and set ups.

Hope everyone’s with me so far and has an understanding of the Back Yard Hacker Ramblings.
Now seeing some of the numbers and how I got the numbers and how they relate to the spring stack that set’s over the shock we can move on to the shock. We have to keep in mind the spring/spring stack and the shock are to different items when we talk about a Coil-Over-Shock. Together they form what we commonly call the shock when actually there two different components and that is why so far I have for the most part keep the shock out of this discussion while discussing springs and there rates.
Sticking with the ATVR racing set up using a Penske (axis) shock. The shock and spring assembly is a coil over shock. You should have it now if not, it’s a coil spring or coil springs placed OVER a shock. Just imagine for a minute how your car or truck handles when the shock goes away or even if you have struts. How many of us have been driving down the road and watched the car in front of us bounce or the tire bounce uncontrollably. We usually laugh don’t we, and get as far as we can from them because we know it’s just a matter of time before something happens. The spring is doing its job even if the shock is shot. The spring is still carrying the weight of the car and moving up and down under the forces acting upon it. The shock has lost its ability to control the motion (velocity) of those forces. The spring is allowed to move uncontrollably through the shocks shaft travel or the suspensions available travel. When this happens the only control is the jounce bumper or bottom out bumper which mentioned prior has its own rate and they do come in different rates to soften or control those forces.
I think I will step back here for a minute and clarify a couple of definitions.
Spring Rate is how much weight it takes to compress the spring one inch expressed in pounds.
Spring Load is how much weight it takes to compress a spring to a given height, expressed in pounds
This brings us to Shaft Travel and Static Sag (ride height) and how the spring rate and preload (load on the spring/springs) effects/changes the two.
Shaft Travel, well that’s pretty simple how far the shaft of the shock moves form full extended and fully compressed or a portion of the total available.
Static Sag is the difference between the height of a given point on the frame with the Coil Over Shock fully extended with the tires still touching the ground and then height of the same point as the pilot sets still (not in motion) with the driver in it. Also keep in mind the type of tire and its pressure as the weight of the machine may change the number. Please remember in this example were using a 1 to 1 ratio and a 12” shaft. So if we jack up the pilot and measure 24” and then lower and get in and bounce it a couple of time and then measure 22 inches the static sag would be 2 inches. For the shock setting mentioned above or a rate of 68.18 pounds (rate=pounds per inch) and the 1” of preload would give us 68.18 times 2=136.36 + (preload poundage) 68.18 = 204.54 of Static Sag poundage. Next we look at Motion Ratio which is the difference between the amount the wheel moves vertical and the amount the shock shaft moves. Since the Motion ratio is at 1 to 1 the Shaft Travel has moved 2 inches that leave 10 inches of shaft travel left to use during bump (compression of the shock).What’s important to note here is the Static sag poundage. This is the amount of spring poundage required to support the pilot with you in it.
Now let’s look at the pilot specs so to the manual we go. Page 1-3 under general information, specifications, dimensions we find that the pilot dry weight is around 600 pounds averaged between the years and not included in this is the added weight of the ATVR parts so we will use 600 pound for this example. We also read that the weight distribution front to rear is 195 to 405 (changed a little to make it easier to figure) so our balance would be somewhere around 30/70. If we add 200 pounds of body weight to the specs then were at 800 pounds and 70% of that would be 560 pounds on the rear of the pilot. If we divide that by two that would 280 pounds per wheel and we can see that’s pretty close to the 204.54 above. Couple of reasons the numbers do not match like the balance number based on the center of gravity, sprung and unsprung weight and few others play a part in the number. We should also consider that the shock is not at a 1 to 1 motion ratio even if it straight up and down.
Getting a little off track so I’ll move along for now. Back to the Static sag poundage of 204.54 two inches of static sag or a sag percentage of 16.66666%. If we take out the preload poundage the new Static sag can be refigured simply by taking the static sag poundage and the shaft travel and the combined spring rate. If we remove 68.18 pounds of load in the way of preload and pre being before we put the weight of the pilot on the coil over shock and we set it back down with the load of 204.54 pounds at a rate of 68.18 we can divide the 68.18 into the 204.54 and get 3 which is you new static sag and a new percentage can be calculated by 3 divided by 12 = 25%. Then we take 3 which is shaft travel at static sag and subtract it form the 12 of total shaft and we get 9 inches of up shaft travel absorb bump and 3 inch of down travel when a hole is encountered and the force of the stored energy in the spring caused it to rebound to a fully extended state.
Now armed with the numbers you can calculate the cross over poundage and bottom out poundage for the shock and make necessary adjustments when changing springs or altering the springs stack.
One note here for one that has a set and they have what we call take set. This is when the spring load has settled. This is where the spring free length has settled over time and the spring may now measure 11.5 or so. Why I note this if you set up your shock at zero preload new or even prloead poundage it will change and change the numbers. Zero preload is worse because the spring stack can become loose and may cause shock damage. This should be checked at least twice of year. Different spring MFG has different tolerance % for their springs and one should at least be aware of it.

Adnoh.

Adnoh, not bad for a shade tree mechanic.
The spring only approach works well for ride height (preload) and cross over.
For spring rate and damping you need a more dynamic approach.

When setting the ride height (preload) and cross over start by deciding what numbers you want.
Then you can play with the numbers .

For the ‘landing a 12 foot jump’ start by making sure you grew a big pair (and realize you might be hurting them).
This is a combination of how much force the spring will absorb and how much the shock will absorb.
The shock will take roughly 2/3 of the load.
I would recommend you set the spring rate by looking at what other people are running as a starting point.
Make adjustments based on rider weight
Personally I always wanted to run a softer rear spring (add preload to maintain ride height) this will improve launching a jump and it will be easier to drag the rear over any obstacle you can get the front end over.

There have been books written about setting the damping.
Good luck.
We have experts that ride the vehicle over all sorts of stuff.
Then they rank it and ask the shock maker to improve certain areas.
They make adjustments and repeat the process.
They can take 3 days to a week to get a basic setting and we still get things like the Odyssey rear end (first year of the current Big Red was the latest one).

Thanks lee. Advice I will take on the dynamic once we get a spring rate and setting for stixs. He is going to start off with a 100 over 125. This will give us springs of 100,125 and 150 to play with. I found a pic on the net that i worked up to show the numbers we will be getting and using hopefully easy for other to follow. Hope I mocked them up right. Once I get his numbers I will or he can share.

more pics

I am shock stupid and suspension stupid but if someone smarter would take this spring rate calculator download/file.php?id=43722 and tweak its settings a little they can input a 7/8" shaft and the proper rear shock travel on the ATVR LT rear shocks (12" stroke I think????) then calculate the spring rate of the shock without any springs installed then you could adjust the pressure to see the affect on the spring rate of the shock.

I was told long ago they set the nitrogen pressure in shocks to 200 psi to keep the bubbles out of the oil I have no idea what pressure it actually takes for all I know you can get away wiht 150 psi, it would be nice if we knew for sure it would also nice to know the max pressure we could use, WHY, well if a guy can get by with 150 psi for normal riding then was going racing he could bump the nitrogen up for a little more spring rate for the big jumps OR is their enough adjustability with the external springs on the shocks to cover this?

Any more thoughts on these LT spring rates I notice this thread is kinda dead since 09 Mar 2013 YOU HAVE HAD A YEAR NOW adnoh - Dave-Co and other LT Pilot owners no excuses lol

I need to go back over this thread. How do I break loose these 2 nuts on the shock?? I have one of those spanner tools that is supposed to grab that nut but they are really stuck together

First spray some PB Blaster on them let them soak then take a soft punch like aluminum or brass and tap the top nut counter clockwise while having someone hold the bottom one from turning once you get it broke loose you can probably just use the spanner to turn it if you have two spanners then use that over the punch...

I would put never seize on the threads messy shit but keeps them from locking up.