The
Team Losi XXX-S Rally Conversion Project
by Mark Gollihur (SixAndEightStringer)


Introduction

Because I'm a tinkerer by nature, I decided that it would be a worthwhile project (and not too complicated) to convert a standard Team Losi XXX-S Touring Car to a purpose-specific Rally car; one that would be able to handle small to mid-sized jumps and off-road obstacles. I wanted to do this for one main reason - although my Team Losi Rally Weapon was still an extremely competitive car, creating a rally with the XXX-S would allow me to have a far more condensed parts bin, since I also race two XXX-S touring cars.

The way I saw it, since the Rally Weapon was simply a Street Weapon with some minor modifications (and special rally shocks and springs), it followed that the XXX-S could be effectively modified to rally as well.

So, I took the plunge. I feel that the car, which I've dubbed the "XXX-R", is a complete success. The following details my experiences with the conversion, so that anyone else who wishes to create the XXX-R can refer to this article for guidance and assistance. Perhaps if we get enough interest, we can convince Team Losi to officially release a XXX-R kit (or conversion kit)!

Getting Started

Okay, I started with a basically stock Team Losi XXX-S sedan. I opted for the standard "Stiffizel" model over the graphite for a couple of reasons; one is that it was simply cheaper. Since I didn't know for sure how successful this project would be, I didn't want to shell out the extra $75-90 for the graphite kit in addition to the car's base price. Also, though the graphite is a tad lighter, the Stiffizel generally is a bit stronger and more durable over the long haul. Since the car will be taking its fair share of abuse, I opted to stick with it on those grounds as well.

My first order of business was to give the car a once-over to determine what new parts I would need to complete the transformation. Since I still had my Rally Weapon, I could use it as a reference for ride height and other factors.

Here is a list of the parts that were needed to complete the basic conversion:

  • Rally tires and a set of wheels - Any brand; I chose to start with the HPI Rally Tire - I've used these with success on my Rally Weapon.
  • Rally body - Again, any brand or model - 200mm body is standard for Rally.
  • Rally shocks/springs - Team Losi #A-5091 (sold per pair, complete shock with spring).
  • Heavy Weight Shock Oil - I used 80 weight oil to start, since this is what the Rally Weapon originally came with. I figure I'll use it as a starting point and "tune" from there.
  • Team Associated TC3 Hex Adaptors - #3950 (plastic) #3949 (graphite) - recommended replacements for the stock hexes; these are thicker, and therefore widen the stance of the car.
  • XXX-4 Slipper Clutch Assembly and Tool - (optional - parts listing below).

Many off road vehicles use a slipper clutch; primarily designed to keep hard stresses from snapping the belt, it's also a tuning option for newer off road drivers, as it can help prevent you from spinning the tires under hard acceleration. With the recent release of the Losi XXX-4 4WD buggy - which is based on the design of the XXX-S - conveniently, Losi has made a slipper clutch that is pretty much a direct drop-in for your "XXX-R to be."

Here's the complete parts listing for the optional Slipper Clutch Assembly:

  • A-3264 - Slipper Adjustment Wrench (XXX-4)
  • A-3265 - Slipper Rebuild Kit (XXX-4)
  • A-3266 - Slipper Hub, Plate & Flange (XXX-4)
  • A-3269 - Slipper Drive Pulley (XXX-4)

Diving In: Rear Suspension

I started with the rear suspension, since it looked a little less complex. I took rear bumper off the vehicle, built the shocks, and swapped out for low roll center blocks (optional). I then simply bolted the new shocks on the rear. That was all that was to it! To re-mount the bumper, I needed to shave off the droop screw "wings." I also removed a little material from the protruding screw "bosses" - otherwise, these bits can be an obstruction, not allowing for enough arm/shock travel. If you have a few extra bucks burning a hole in your pocket, you might consider getting the bumper kit for the XXX-4 - though you can only actually use the rear XXX-4 bumper, since the front is a buggy bumper (which lacks the front body mounts, which you'll need to mount a rally body).

Another thing you'll need to do is create some room between the chassis and rear tires; you can do this by putting both hinge pin spacers on the front of the hingepin; this extends the wheelbase, which you'll need to do to keep the larger rally tires from "rubbing" the back corners of the chassis. Also, swapping out the stock hex mounts for the ones from a TC3 will also help - the TC3 hubs are thicker and therefore widen the car's stance by a few millimeters (standard electric rally width is 200mm, so this also helps get your XXX-R closer to class specs). You can make the stance even wider by specifically seeking out wheels that are "+3mm," which means that the wheel centers are offset 3mm (making the car's stance 6mm wider).

As you can see, ride height is plenty sufficient. The sweet replacement aluminum cups and collars are aftermarket pieces by Hammad Ghuman (optional, but recommended.)

Next Up: Front Suspension

Originally, I considered installing a set of lowered roll center hinge blocks in the front; my logic was that this would lower the mounts for the arms, which would, in turn, lower the bottom point of the arms' extension. I was looking for every millimeter of extra "throw" before the arms "bottomed out." However, I realized that the hinge pins were further in on the chassis than I thought - and lowering the roll center actually inhibited throw since the chassis actually blocked the arms before they were fully extended. So I opted instead to set it up with the high roll center, and it works quite well.

Again, doing the conversion was largely an operation of simply swapping out the shocks. One additional thing that I did need to do was shave a little bit off of the bottom corners of the C-hubs; they bottomed out on the cross member of the front arms, limiting travel. I also sanded down the cross member a bit, thereby "evening the load" between them rather than taking all of the necessary material off of just one of the pieces. After sanding these parts down, I coated the "shaved" sections with thin CA to (hopefully) strengthen them.

Now that both the front and rear are set, the ride height should look really good. You will have to shear off the droop screw mounts on both bumpers, and there's a small extension to the chassis lip in the front that you'll need to Dremel off as well; it limits the down travel on the front arms and would put undue stress on the arms/hinge pins.

One other thing that is quite promising is that, even with the ride height raised, the dogbones still are seated well inside the outdrives. This was a nagging issue on the front end of the Rally Weapon; it was necessary to use aluminum or titanium outdrive saver rings (and restrict the front ride height) to prevent the dogbones from popping out, which pretty handily shredded the outdrives - the dogbones simply were too short to handle the additional travel. This isn't a problem with the XXX-R - even with the arms fully extended, the "ball" of the dogbone is fully seated within the differential outdrive. This is very good news!

Giving the XXX-R "The Slip"

Excerpt from Team Losi Manual: Installing the Slipper Clutch (PDF)

When I built and installed the slipper clutch from the XXX-4, it fit into the car quite nicely. However, there was a slight problem: The drive belt gear attached to the spur is a few teeth smaller than the one normally supplied with the XXX-S. (I assume that this is to compensate for the larger tires on the XXX-4.) This caused me some pause, since the belt tension adjuster -- in its stock form -- cannot be adjusted far enough to put the appropriate tension on the belt. In other words, we have more belt than we can use, because at its furthest adjustment the belt still has way too much slack.

After much thought, I decided that the most straightforward (and effective) solution is to simply drill another screw-hole in the tensioner. I carefully marked and drilled a pilot hole a little further up on the adjustment arm, and then drilled it out to be just a little bit smaller than the adjustment screw. I then took an older steel screw with a large hex and drove it into the aluminum arm, being careful to ensure it was straight. I backed it in and out a few times to cut some threads into the new hole.

It worked like a charm! The placement of the hole is perfect (to ensure that I'd get it right, I drew a dot on it with a Sharpie while the whole tranny was assembled) and the mod was completely effective. Now the belt's tension wheel comes up a little higher inside the assembly, but everything still works as it is designed. There does not appear to be any detectable friction increase, and the tranny is still very smooth.

Options: "Overdriving" the Tranny, Shock Tower Options

After asking around, I decided to use the optional overdrive pulley in my XXX-R. It's included as an option with the XXX-S kit. Installing this pulley, especially in an offroad car, is likely to help with on power traction in (and particularly out of) turns. If you're an aggressive driver (like me), this is a good thing. If you're "brakes happy" (particularly diving into turns) you may wish to leave the stock configuration intact. I installed it, and I'm very pleased with the car's handling in the turns.

Here's what the XXX-S Manual has to say about the Overdrive Pulley:

Overdrive/ Underdrive; In bag H you received a 41T pulley for your XXX-S. This allows you to over-drive (make the front tires turn faster) or underdrive (make the front tires turn slower) the car. Using the 41T pulley in the front of your car will give you overdrive. This will give the car less offpower steering and will give you more steering exiting the turn. Running the 41T pulley in the rear will underdrive the car. This will give you more steering entering the turn and less exiting the turn.

A full set of instructions for installing the pulley (which is simply a replacement gear for your front differential) are in your XXX-S manual, so I won't repeat them here. Just remember that you want the smaller gear in the front. This will direct more of the motor's power to the front wheels, making them the dominant pulling force, particularly out of corners. I found this to be advantageous in the dirt; you may find it to be irrelevant. Your call, it's optional!

Also - I added the PRP "Mega-Tune" shock towers. With the many as yet unknown variables at play, it's comforting to know that I have a ton more options for tuning at my disposal. They're very well made, quite stiff, and they really did make getting a solid setup much easier.

Results

Straight up: the car is a complete success. It's very fast and smooth, hooks up really well in the dirt - both loose and hard packed - and it jumps very well (which was not a strong point of the Rally Weapon). It's extremely stable and seems to be up to the abuse so far. I've raced it competitively on a large, fairly harsh and loose off road track, a hard-packed dirt track with small jumps, and a "tarmac" stage (on pavement with treaded tires.) The XXX-R excelled in all three environments. I have not flung it over really large jumps yet, but I anticipate that it will be up to the challenge, considering how well it handles in the air on smaller jumps.

We'll have to see about durability over the long haul - so far I've only broken one part: A c-hub snapped when I T-boned a solid metal pole. If something hadn't broken on that shot, I'd have been shocked!





Special thanks to Todd Hodge of Team Losi for his help with the slipper clutch part numbers (before the parts were released.)
All material and pictures �copyright 2002 Mark Gollihur. All trademarks are owned by their respective companies.