Executive Summary: Yes you can.

Should you do it? Read on....

Background: Prior to 1999, Polaris Xtra-10 suspensions could be tuned for either slow speeds and small bumps, or higher speeds and bigger bumps, but not both. Well, not very well, anyway. The skid uses torsion springs, which are strictly straight rate springs. So, you pick your rate and make your compromise. A softer spring gets you a softer ride but bottoms too easily. A firmer spring works better at speed, but rides harshly when you're just cruising. Help is available from tunable shocks, suspension mount settings, and coupling adjustments, but those darn torsion springs are still a compromise.

Enter the Polaris Position Sensitive shock, used on the 1999 XC and XLT Special lines. By now, you've probably read about its bypass valve design, and seen the ads with the cutaway illustrations. The PPS is designed to overcome the compromises of earlier Xtra-10s. It allows the 99 XC to run the stiffer spring needed for big hits, and it provides appropriate damping for big hits with the stiff spring. However, on small hits, the shock is intentionally flabby, leaving most of the bump handling job to the spring. With little shock dampening in the "ride zone", the spring/shock combo is no longer too stiff, it's just right. And 99 XC riders will live happily ever after.

So, you want to put a PPS on your pre-99 Xtra-10? So did I. I bought a used 1998 XC 700, a sled that is notorious for riding like a lumber wagon at low speeds. Before picking it up from the dealer, I had him install a PPS. It bolted right in; things looked great! However, I kept reading and hearing "It can't be done", "Things will break", etc. I decided to really dig into it, to compare my skid to the 99, and further, to see if other Xtra-10 versions could be fitted with the PPS.

The first thing I did was pull my skid frame out of the sled for intense scrutiny. I cycled the suspension and found the PPS could hit as it slid underneath the front arm. However, I later realized it was not a valid test. I allowed too much movement by not having the torque arms mounted as in an installed situation. After I spaced the arms properly, there were no clearance problems. Hooray for our side!

Next, measuring tools in hand, I went out to my friendly local dealer, Bob Lissy at Lissy's Polaris in Wilmington, Illinois. With Bob's permission and tolerance, I sized up the skids. After making several sketches that included each and every mounting and component dimension that affects the PPS installation and functioning, I am confident in saying the following. The PPS can be mounted in 1998 XCs, as well as other 1997, 1998, and 1999 Xtra-10 short tracks. I did not have access to any long track or 1996 versions. However, others are reporting that 1996 short tracks are not a problem.

Here are some of the noteworthy items I found. The 98 XC has a skid version different from other 98s. Other 98s were apparently similar to 97 skids. These two versions also appear to be in use in 1999. The two skids differ as follows. The XC skid has three mounting hole locations for the lower rear scissors to the slide rail, whereas the "regular" skid has just one scissors mounting hole. The one hole on the regular skid is located where the front hole is on the XC version. The stock mounting on the XC skid is in the center hole, making it somewhat stiffer in initial spring rate.

Also the two skids differ in the FRSS and RRSS block positions offered. The XC offers more choices. The remainder of the basic geometry is unchanged between the two versions. To test the PPS clearance in the regular style scissors mounting, I moved my scissors to the front hole, and cycled the suspension again. No clearance problems whatsoever. In fact, the tightest clearance occurs with the XC scissors set in the rear hole, and the FRSS set at low-low. It may look like the shock is hitting the arm in the photo, but there is still about 3/16" clearance. And that's as close as it gets, using a scissors and FRSS combo that is not normally used, and is not even available on the non-XC skids.

Some people have reported having to use washers to space the shock relay rods (thin rods that are just under the shock body) farther apart than stock, to clear the shock body. On the 98 XC, this was not an issue. On my 97 XCF, the rods do measure slightly closer together. Adding a washer on each relay rod attachment would not be any trouble. The 99s do not have washers and have the same shock rods as the earlier models. Manufacturing variances may explain why some suspensions will need to have washers installed. Just check your suspension in this area for clearance when installing the PPS.

One interesting find is that in all measurements pertinent to the PPS fit and function, the 98 XC skid was identical to the 99 XC skid. Yes, identical. But there are differences, you say; you've read about them? Yes, there are. But they don't affect the PPS.

Here are the differences and updates for 1999. According to an inside source, skid frame changes have been made in two areas:

1. More front arm travel, better planing and rolling resistance. A flatter-angled rail is used. The front arm is the same part as last year, but it is mounted in the top mounting hole in the tunnel bracket, which is 3/4" higher than the 98 center-hole mounting. The rail is then lowered back to the right place by using limiter straps that are 1" longer than in 98. The Indy Select shock is the same part for 98 and 99. We will cover spring rates later. None of this affects the PPS.

2. Moved the carrier wheels (up inside the tunnel on the rear arm) away from the edge of the track. Polaris moved the wheels inboard to address track durability issues. This required a different rear torque arm, new square-wire springs, and related spring mounting hardware. However, no geometry changes were made, therefore it's a non-issue regarding the PPS. The 99 XC torsion springs are the same rate as the old round ones on the 98.

Now, should you consider installing a PPS? Why would you not want one? Well, consider some drawbacks.

According to sources, the PPS is not a snocross racing shock. It is tuned for comfortable and aggressive trail riding, which is a neat enough trick in itself. Later on, there will be performance kits to reduce the amount of bypass, which will make it more like a regular Fox. One interesting advantage it has is better heat dissipation due to the aluminum body and large oil capacity. Here's a tip: For best heat dissipation, remove the pretty body graphics wrap.

The PPS is also not a drag racing/holeshot/big transfer shock. It requires tight coupling to work, and tight coupling is not desirable in drag racing, hill climbing, and many performance situations. If you do run a PPS not tightly coupled, you may not like the resulting quirky behavior.

If you do run a PPS, emulate the stock settings:

1. FRSS in high hole, set on medium or high.
2. RRSS in high hole, set on low or medium.
3. Scissors mount in center hole.
4. Torsion springs at medium.

Now let's talk springs and other things you can play with.

Front track shock springs: The 99 XC SPs have a front track spring that is 190 lbs. straight rate along with its Fox shock. The 98 XCs and 99 XCs have a 200 lb. variable rate spring. Running the 190 lb. spring is reported to give a noticeably better ride, but this may be because of the change also to a Fox shock. The 200lb variable is there for the times when you hit that super big bump. The Xtra10 works well if you can lighten up that front track shock spring as much as possible while still avoiding bottoming. If you don't pound bumps at 40+mph then softening it from the 200lb variable will help the ride quality. The dealer has a listing of all the shock springs available, you might want to try and soften yours up if you don't pound the big bumps. The other thought is that you're putting the PPS in the back so to get all the benefits you might well want to put a Fox in the front of the rear suspension as well.

IFS springs: The 98 XC has 75 lb. straight springs. The 99 XC has 100 lb. straight springs, and the 99 SPs have 74/120 variables. It was discovered that 98 riders were cranking up the 75 lb. springs so far to get the right bump handling that they were creating a nose-up attitude. Switching to the 99 100 lb. springs is recommended to cure this situation.

Front torque arm: The arm is the same for 98 and 99, as previously mentioned, as is the Indy Select shock. Should you move your 98 arm up and use the longer 99 straps to let the rail back down? After all, you gain an inch of travel, and the upper holes are available (undrilled) in the mounting bracket. Well, sources say "Don't do it". Apparently, you will create "slight adverse track tension issues". It is not clear why it is an issue for 98s but not 99s, but that's the word.

For those who do decide to move the front arm up, pay attention if you are using a Fox front arm shock. For 99, the Fox shock used on the SPs is 0.1" shorter than the previous versions. You can shorten an older Fox by replacing the bottom cap. While you are at it you can install the multi-step nut that fits both size springs. If you don't shorten your Fox shock, you can bend or crack the torque arm, according to our sources.

Don't let all this trivia obscure the main point. You can install a PPS in your earlier Xtra-10, and if you're a trail rider, you'll probably be glad you did.