Indy Project Sled - XTRA-10 Installation

XTRA-10 Rear Suspension

Nov. 01, 2005 By ORC STAFF

XTRA-10 Rear Suspension

Cost: $1000 (US)
Risks: Minor risk of mis-drilling the mounting holes
Benefits: Immensely improved ride
Tools Required: Drill, 9/16" sockets/wrenches, measuring tape
Parts Required: New suspension, bolts or rivets for relocating the suspension mount plates
Mechanical Skill Required: Average "shade-tree" mechanical skills
By itself, installing an XTRA-10 in an older Indy is really easy. Essentially you drop the old suspension out, measure carefully for the new mouting holes, relocate the suspension mount plates, drill the new holes and bolt in the XTRA-10. Ride height is just slightly higher than the stock '90 Dial-A-Just suspension, but after 10 minutes on the sled, that becomes a non-issue, especially after you hit that first big bump on the trail.  
Drilling the mount holes is the only critical part and it is absolutely essential that you get the measurements right! Too far back or forward and you can't get the track tension right. Too far down in the tunnel and you *will* increase ride height and adversely affect cornering. Too high in the tunnel and you won't have clearance for studs and/or the track will hit the tunnel on every big bump. But the most critical measurement is center-to-center distance between the front and rear arm mount points. Do not just measure the distance between the arms as the suspension sits on the floor out of the sled! The suspension has to be compressed slightly to install it in the sled and the arms move closer together when that happens. 

In my sled with the chaincase rolled, the measurements are as follows: 

Front Arm Mounting Hole:
Back from steering hoop: 5 3/4 inches
Down from top of tunnel: 4 1/2 inches
Rear Arm Mounting Hole:
Back from front hole: 23 1/2 inches
Down from top of tunnel: 4 1/2 inches
As you can see from the following pictures, the tunnel begins to look a little like a block of swiss cheese.  
One very nice trick is to have a piece of stainless steel fabricated to cover the outside of the tunnel where the new holes have been drilled. I have seen this done, it looks good and works well and will be one of the things I do to my sled before the snow flies. 

Where to Find an XTRA-10 Suspension  

You can buy take-out short-track XTRA-10 suspensions at some western dealers, from people who have installed M-10s and not traded in their old suspensions, at sled salvage yards, etc. I was lucky enough to find one from an Ultra SP that had Fox shocks already installed. I paid a premium price, but dollar for dollar, you won't do anything to an older Indy that will result in such a dramatic improvement. You can argue that the thousand dollars you spend on the XTRA-10 would make a nice down payment on a new sled and I cannot refute that. As I've said before, this kind of project is not about having the best sled you can have for the least amount of money - it's about the pride of owning something unique and of having done the job yourself. The side benefit of learning about every nut, bolt and rivet in your snowmobile is nothing to dismiss lightly either. 

Pros and Cons  

The only downside to installing an XTRA-10 is that it weighs more than the older Polaris suspensions. The '90 SKS suspension I removed is lighter than the short-track '96 Ultra XTRA-10. But unless one of your stated goals is weight reduction, it's not worth a second thought. And even if you do want to reduce weight, the ride improvement is worth twice that much weight. The good part is that, as we'll see in a minute, there's a companion mod that will just about offset the suspension weight.

1996 Ultra XTRA-10 64 pounds
1990 Indy 500 SKS Dial-Adjust 57 pounds
There are those who say the XTRA-10 is not as good as the new Cat suspension in the big bumps. That is entirely possible, but I can say this for sure - the '96 XTRA-10 is an order of magnitude better than the '96 Fas-Track suspension that I had in my '96 ZRT 6. I have no doubt that the new coupled rear suspension from Cat are better than the '96 and the '97 and newer Cats are outstanding sleds, there's a chance I may still end up with a new Cat this year, depending on what prices do this fall. Be that as it may, the Indy is a fun sled to ride and it handles the bumps really well. 

Alternatives.  

There aren't a lot of alternatives, although there are more than there used to be. Obviously, the number one aftermarket suspension is the M-10 from FAST. There are a lot of good reasons to go that route and if you have the money, there's no question that it works much better than the stock suspensions on older Indys.

Personally though, I prefer the XTRA-10 to the M-10. As stated over and over in other places in Snowmobile Online, your mileage may (probably will) vary. The other alternatives are things like the Trail Tamer, which increase the travel at the rear arm. I have never tried a Trail Tamer but I have been told by those who have that the ride improvement is not dramatic. 

Another option to improcve the ride is to buy a set of good rebuildable gas shocks and have them revalved to match your weight and riding style. When revalved by a good shop like Carl's Cycles, the difference a set of gas shocks can make to a sled's ride and handling is nothing short of dramatic. In my opinion, most sleds with rebuildable gas shocks have a lot of ride and handling capability left "on the table", so to speak and it takes a knowledgable and experienced tuner to take advantage of that. 

All that said, in my opinion, to make an older Indy ride like a new sled in the bumps, installing an XTRA-10 is the way to go. 

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