Now that I have a good triple rate spring set (dual rate with helper) up in the rear. It’s time to work on the front shock, going with a zero preload set up to match the rear. This set up will be a helper spring with an 11lb/in rate and a single linier rate spring. The goal here is to match the set up of the rear as not to upset the handling due to the effected change on the front of the machine. I have also mentioned a change in valving, driver ride height, and sag %. It seems I am all over the place with things however it was a plan to change the machine from a dune chaser to an all around area machine with doing static changes in ride height, sag% and adjustments in low, high speed compression and rebound. Basically a turn here and there and good to go without changing: Springs, Caster, Camber and Toe. The lovely wife just shacks her head at me and says you just have to mess with it don’t you. Guess I am never satisfied with the how it performs area to area plus I like to wrench on my Pilot when I can. Just like a Quad or UTV this can impact the handling of the machine. Since I tend to bla bla bla I took a different approach with modifications to the machine. In each post I place a picture or two and a statement or two leading further to the goal. So reading or skimming thru each leads to another etc. In this case it was the pictures I took and posted on how the pilot looks sitting from the side. Other picture to look over was the shocks and the springs at different setting and compare to the side view. This leads us to why change the front spring and valving set up to go with the rear other than I used a helper in the rear. The front had a dual rate set up which had a Tender Spring, Main Spring and Cross-Over Spacers. Different from the rear which had a dual rate set up with cross over collars. The difference is the rear can be fine tuned by turning the collars up and down for a given cross over point and the front has to use different length spacers in between the Tender Spring which requires the Spring Stack to be removed from the shock and spacers changed. This was a mistake when I ordered them for Penske years back so that’s my Bad. When new shocks are ordered they will have this ability to fine tune. It’s not more money, so URRRRR. For this set up it’s not good in way of adjustability for different sag %. As I raise and lower the ride height via Static Pre-Load it changes the cross over point on the shock at a different shaft length changing the shocks applied load. So you see it’s not as easy to change the static setting for different areas without upsetting the machines handling. This leads us to the subject at hand and the way the machine sprung weight sets front to rear or there ride heights. I call this the Chassis Ride Height or Attitude. We see this a lot on our modified suspension for our machines and Bull like to comment on it every time “the front looks a little high”. So what is He talking about and what does it affect. We can imagine a horizontal line just a flat line across the page with no angle to it. In my 250R days we called it a flat liner, so we knew it was most likely not set up right and would handle poorly. Still true today with 450’s and UTV’s and or Rides. Now you see the relationship to for mentioned pictures and the way it set from the side. In the old days (1988 TRX 250R and 1989 FL400 Pilot) we could not make as many adjustments to front end in way of Caster, Camber to offset some of these negative effects. They did make different arms one just could not afford them or I could not. So fixing a flat line was done with sag only front to rear or changing that flat line to a straight line with an angle to it and re-valving the front shock on the 250R and nothing on the FL400. I now Bla Bla BLa, This is why the static preload is so important and one of the first things to do to achieve a desired Attitude of the machine. You can also see why the work shock was a vast improvement over stock on the fl400 and front trx250r. They’re not going to tell you that and why it improved its overall handling. Don’t take my word for just look at FL 400’s that have stock and works you will see a difference. Keep in mind the factory setting on geometry has not changed and is set. This is why 250r and 450r front spindles do not work well on a stock machine; it’s all out of wack. Now you have the base line facts and an idea of the Bla Bla Bla. We can move forward to the change of the front spring set up. The front Helper spring is an Eibach HELPER200 its Length: 2.83”, ID: 2”, Rate: 11 lb/inch, Block Height: .43”, Travel, 2.40, Weight: Who cares. This spring will set atop an 8” tall linier rate 240 lb/inch spring with a zero pre load and cross over at Block height. Then I can add static preload to set the front at a desired ride height for a given Attitude for a desired sag% without changing the Camber, Caster and Toe. At 11 lb rate the blocked out poundage will not upset my valving too much based on a single rate. As I add static preload to the block height at 240 lb /inch it will not take much to raise it where I need it and maintain a fixed rate. The added static load will affect the rebound portion (get quicker) so a click or three will fix that. What also need to be taken into account is the leverage ratio of the shock and its placement on the arm. Leverage ratio would be shaft movement in inches compared to wheel movement in inches. Example would be shaft 5” wheel 10” it would be a 2 to 1 ratio. If you look at that example now the spring rate of 240 does not look so harsh or 120 per inch of wheel travel. The real world number will vary with my set up is couple different ways. I have two (2) shock positions on my arms which affect three items, Motion Ratio, Shock Angle and wheel rate. Motion ratio was covered already so let’s look at the Angle of the shock and multiplier that would apply. This not a big deal if by moving the shock angle with a few degrees from what you have. If more than 1 or 2 degree you should factor it in. Simple to do in way of COS (cosine) of angle, open up your calculator on your phone enter shock angle in degrees 10 than hit COS button=.984. In my case I am taking the shock from 30 degrees to 25 degrees or .866 to .906 % efficient. This relates to the rate in a way of an increase in rate of 207 to 217.44 or 10.44 lb inches. Now with a rate on the helper of 11 x 2.4(travel) 26.4-10.44=15.96 lbs of change. That was the easy part, the third thing is the placement of the shock on the arm I moved it in which not only changes the motion ration but the wheels rate or the rate the wheel sees. There’s is a little more involved and may loose ya unless you want to hear about it. So I will skip past however take note as I will use it in another post. Back to Motion ratio, and the impact of the shaft and poundage. At 4-3/4 (4.75) inch shaft and a wheel travel of 12.5 (12” effective) 12/4.75=2.526 which is kind of high I like to stay within 2 to 2.5. The effective spring rate now at 217.44 and a motion ratio of 2.56 were at 96.38 of rate per inch of wheel travel not including the effect of the wheel rate its self. The initial 240 lb/in spring does not look so bad compared to the 96 lb/in calculated. With this I can compare to rear final rate which I will cover later. I can now take the Helper travel of 2.4 and subtract it from the shaft of 4.75 and get a bottom out poundage. I’ll take the shaft length of 4.75-2.4(helper travel) =2.35 inches of shaft times 2.526 (motion ratio) 2.35 x 2.526= 6 inches of wheel travel at zero preload. Darn near 50% which is where the rear is at right now. This allows for adding static pre load for ride height adjustments. If I look at the dual rate number and sag it provides I can easily compute what preload I need and or Block height for the 240 spring to get the correct attitude. For a bottom out poundage for this I would simple take the spring rate of 240 x 2.35=564 not including the bottom out bumper. For this package I would use a progressive rate and add 1100 pound at final by replacing the tall soft bumper with a short stiffer one. Head hurt yet? Good thing I did not add the wheel rate into it. As you can see this would require more compression damping and a more aggressive rebound damping. Since I use a single rate on the front valve stack and a high flow linier piston in the shock it’s an easy fix. For compression I go from .050/.007 (thickness) to a straight .008 with rate plate and for rebound I go from a straight .008 to a .010/.015, I also used a 5 wt at 220. PSI this allows me to control from the adjusters. You may ask why so aggressive on rebound. It is due to the motion ratio of the shock to control the leverage ratio of the arm. The force acting on the arm at the wheel will be higher so I need to add damping. This will help keep the attitude in check when hitting the rough sections and dial in the chassis lift from the rear with the adjusters and the changed valving. Yep back to the line thing and its angle. Now you can see the big picture of the testing I did last couple of months it was not all about the clutches. No I am not done yet, you wish, Fat chance! We should look at the impact on other items due to this change good bad whatever. So when it comes to sag and the attitude we want an attitude that is good for the machines settings, duuuu. First look at what was done. Increased sag; lowered the ride height front to rear which yield a lower center of gravity. I say that is a good thing for corner stability etc. It also allows for the body roll to take set quicker. It allows for more down travel on inside wheels while cornering as not to have great impact on wheel load and straight line surface irregularities or big hole and keep attitude in check not pulling chassis down. Less low speed valving (adjusters) required so ride is not harsh at low vehicle speeds. Most that have a long travel have some sort of bump kit for their steering set up. With a lot of them the steering it harsh or stiff and use a power steering. I have found with a lower ride height the steering tie rod angle is much less and so much easier to turn darn near as good as stock. The down side is a little feedback just like stock I would say there is a trade off there. What I did was take this into account for new Caster Camber and Toe setting along with the attitude setting. Starting in the front I found a good happy medium in the steering and set front ride height. Then I set the attitude from the rear remember the fine tunable cross over and ride height adjusters. Then set camber, then caster then toe. Keep in mind I’m using a 05 TRX 450r front set up. The Camber is ¼” negative, Caster is set at 3 degrees positive, Toe is set at ¼ in. I will not even bring Ackerman into it as you will go “I’m out of here” which I have some adjustment built into the bolt on bump kit. For me I this works well for my Pilot. The rear valving took on new numbers as well. I soften up both compression and rebound as these shock come to stiff from AXIS. The rear adjuster has a ton of room in them. The rebound was just too stiff and was packing and pushing the chassis (kicking) up to much thru the woops. I used a high flow linear 1 degree dish valve (preload on compression) with a .005/.007 straight linier with rate plate for compression. I used a flutter stack .005/.008 - .010/.015 (dual rate) progressive on rebound. This will allow for high rebound shaft speed at low compression shaft speeds and slower rebound shaft speed at high compression shaft speed. With Penske they use a letter system for valving like A, A+ and A-, A is a linier set of one thickness (4- .006). An A- set is two of one (A’s .006) and the next two one smaller (2-.006, 2-.004). An A+ set is is two A’s and the next two larger (2-.006, 2-.008). Then they use a Letter over a Letter for the valving, the first letter being Compression and second Rebound, kind of confusing until you get use to it and wrap your head around it. Fox is much easier. So my new front setting is a B .008 over C .010/E .015. For rebound I could have used a C+ and been close. I left OD out of it to save you the additional pain. Talk about pulling your hair out. TMI?????
Goes to show it’s all about attitude!
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