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Traxxas Slash Dirt Oval MUDboss Conversion

These days, one of the most popular vehicles at the RC dirt oval track isn’t even a dirt oval car. It’s a short course truck. Specifically, it’s the Traxxas Slash. Not only is dirt oval racing with a Slash a thing, it’s a big thing. And, we really like the idea, so to get in on the action, we built what’s called Mudboss.

There are two types of people in the world. People who know what a Mudboss is and people that don’t. Hopefully by the end of this article not only do you know what one is, but you also want to build one. So, what in the heck is a Mudboss? Let’s get that out of the way. Well, it’s an offbeat nickname for the RC version of a rather old and odd class of race car. A Mudboss, or more specifically a Salvas MUDboss, is a scale version of an eastern modified dirt oval race car that uses a Salvas brand body and, as previously mentioned, is based on the Traxxas Slash. It’s also worth noting, because it’s essential to what Mudboss racing is all about, that this is spec racing. But, don’t let the spec designation fool you. Mudboss racing is anything but slow or for newbies. This is some fast, action-packed wheel-to-wheel racing.

To most people, a Mudboss is an odd looking machine, but it’s also a pretty good scale representation of an eastern dirt modified car, or EDM. Under a variety of different sanctioning bodies, full-size, real-deal eastern dirt modifieds “bang fenders” on dirt tracks from Canada to Florida. The distinctive features of the modified are the big panels making up the back of the car and the open-wheel front end. It’s kind of like a late model and a sprint car “got together” behind the grandstands after a race.

The Salvas MUDboss bodies are made from sheet Lexan and come pre-cut and pre-drilled. All screws are included. These bodies can be painted in the same manner as a molded Lexan shell, but most racers opt for a vinyl wrap. Eric Salvas, the creator of the body and class, suggests wraps over paint (see the interview below for more on this). Following his advice, I too went with a custom wrap. And, based on a recommendation from Salvas, I sought out Lyle Hoover of Hoover Graphics & Race Wraps. While installing a wrap is definitely a DIY project that just about anyone can successfully complete, a service I really liked about Hoover Graphics & Wraps, in addition to the awesome graphics, is that you can buy a body with the wrap applied. That’s a nice time saver and stress saver if this sort of job makes you nervous. As far as the design goes, he nailed it. Best part, it’s a computer file. When I need to replace the body and repaint–I don’t. Instead, I contact Hoover Graphics & Wraps and order a new wrap. How cool is that?

To mount the Salvas MUDboss body you need to remove the front bumper and front body mount assembly. Replace the front bumper with Traxxas part number 2735, which is a Bandit front bumper. The trick here is to mount the new much smaller bumper upside-down. This creates a surface for the front of the Mudboss body to sit.

Next, completely remove the two nerf bars. Leaving the left nerf bar is optional. Now, remove the two body posts from the front body mount that originally attached to the front shock tower. Use the 3×10 mm screws originally used for the body posts and install the posts in the forward holes originally used for the nerf bars.

You’ll probably notice the body contacts the steering servo. One fix is to raise the body posts using spacers. Another is to use aftermarket longer body posts. The best “fix,” however, is to remove the servo, which is mounted on top of the chassis, and mount it to the bottom. This will allow the body to sit lower, which will lower the center of gravity and improve handling.

One last point is the Salvas MUDboss body includes four front body post holes. The forward most holes are used for the stock chassis and the holes slightly further back are for the Low-CG chassis.

The Sportsman class allows a couple steering upgrades. One is the optional use of the Traxxas 2075X metal gear servo. This is the quick and easy way to get the durability of metal gears. The rules also allow the use of the black 6845X bellcrank style steering setup that has a built-in servo saver.

Since I am running in the Sportsman class with the Mudboss, I am limited to Traxxas tires. Any Slash tires are allowed, except the S1 compound. This means three tread options exist–Traxxas SCT,  BFGoodrich Mud-Terrain T/A KM2 and Kumho Venture MT tires. The general consensus is the original SCT tires provide the least amount of traction and the Kumho tires provide the most with the BFGs in the middle. That is rather subjective, but it will give you at least something to play with for tuning.

Oval racing and batteries go together like peanut butter and jelly or, depending on your perspective, as Cal Naughton Jr. put it, they go together like Chinese food and chocolate pudding. So, whether you see it as good or not so good, batteries are a big part of oval racing. You are not going to be competitive with any old pack. It used to be a lot worse. 4-cell racing was a lot of fun if you had a hot pack, but if that pack was just a little bit soft, it was, indeed, about as enjoyable as someone dumping a Snack Pack on your General Tso’s. The Sportsman Mudboss class I’m racing in has a battery limit of 5200 mAh  with no more than a 50C rating. This prevents if from being a battery budget war, but having a good battery can and will make a big difference. For that reason, I hooked up with SMC Racing. Look, there’s a lot of hype (read: false information) out there when it comes to battery ratings, specifically C rating. Go with a company you can trust. More on that here. There’s no industry standard when it comes to rating, so someone’s 50C might be more like 40C or even 25C. SMC has been in the performance RC battery business since long before LiPo cells were a thing and have lasted this long on a reputation built on trust (and a whole lot of race wins).

The specific SMC Racing battery I went with is the True Spec Extreme Graphene 7.4V 5200 mAh 162A 50C hard case pack, which features 10AWG wires soldered directly to the tabs for lowest possible resistance. It’s a spec pack, but make no mistake, this is a race battery. The best part, besides providing a competitive advantage, is this pack costs less than $50. You’re getting a lot of quality and performance for your money with SMC.

The Sportsman Mudboss class allows for only a few adjustments. You can change shock fluid. I swapped the shock fluid for 30 wt. on the left front and left rear shocks and 40 wt. on the right front and right rear. I did this to slow weight transfer. I want my car to have as much steering as possible. I want to carve turns with as little turning of the steering wheel as possible. That said, there are three conditions I want to avoid. First, I don’t want the car to spinout. To start out, I’ll give up a little steering for drivability. Second, I don’t want the car to traction roll. Third, on a car with a high center of gravity and a relatively plush suspension, I don’t want to transfer too much weight or transfer weight too abruptly. When this happens I find the car is too unpredictable. A few things happen. The left rear gets unloaded and the car diffs out and when weight shifts hard to the outside while corning and it just as abruptly shifts the opposite way when the car straightens out. So, that’s why I went with thicker fluid on the outside. And, odds are I’ll make adjustments.

The Mudboss rules allow you to cut up to five rounds off each front spring. This, of course, lowers the car significantly. When you do this, it’s easiest to use handheld snips, but you must wear eye protection. Internal spacers on the shock shafts are also allowed. I went with .6 in. in the right front, right rear and left front. In the left rear shock, I went with a slightly shorter .4 in. spacer. This allows the inside rear tire to stay in contact with the ground during hard cornering. Installing the spacers requires dissembling the shocks. The spacers (I used fuel tubing) go inside the shock, on the shock shaft, under the piston. Be extremely careful when pulling the shaft out of the the shock body and reinserting it. The sharp threads on the shaft will easily cut the seals if you don’t go slowly and use a lot of care. To install spacers, remove the shock from the vehicle and remove the shock cap. Drain the fluid and discard. Next, remove the lower shock mount known as the rod end. If you have a tool specifically made for gripping shock shafts, use it. If you don’t you can protect the shaft with multiple layers of paper towel between the shaft and your pliers. It is extremely important you do not scratch the shock shafts. When the rod end is removed, carefully slide the shaft and piston out of the shock. Slide the spacer on the shaft and seat it all the way up against the bottom of the piston. Now, reassemble the shocks.

Since I lowered the front suspension with internal spacers and cut down springs, I used the inner suspension arm holes. On the rear arms, I used the second from the outside. This is hole number four on the setup sheet I created below.

The Sportsman MUDboss class require 16-tooth pinions matched with 90-tooth spur gears. This is what is included with a stock Slash. The rules also require no gear cover to allow for quick and easy gearing inspections. In addition to Sportsman, there are other Mudboss classes with different gearing rules.

Like the majority of the spec racing classes based on the Slash platform, the Sportsman class is limited to an unmodified Traxxas Titan 12T motor with stock XL5 speed control. We’ll cover race prepping one of these motors in another article. For now, keep it simple and use some bushing oil (thicker than nearing oil) on the bushings, run the motor and then thoroughly clean it and lightly relate it.

There are two important things to know about camber when it comes to racing Slashes on oval. One, it’s one of the few adjustments you have, so take advantage of it, and, two, camber is crucial to oval racing.

The simple definition of camber is it’s the angle, looking from the front, that the top of the tire leans in or out. The top leaning towards the center of the car is negative camber. Positive camber is just the opposite. As a car corners, the cornering forces encountered cause the car to roll to the outside and causes the tires lean to the outside. So, to maintain traction, by having as flat of a tire contact patch as possible while cornering, negative camber is used. Say the cornering forces cause the tire to lean to the outside by 2º, if you start with -2º, in theory, the tire would have 0º as it cornered. That would mean more contact patch and more traction.

Race cars that turn left and right, off-road or on-road, will run negative camber on all four tires. Kids driving their mom’s old Honda will a lot of negative camber.

Oval cars are a little different because they only turn left. An oval car will run negative camber on the right front and right rear (known as the outside tires). The left front, or inside front, can have zero camber or even positive camber. There’s no rule saying negative camber can’t be used on the left front tire, but it isn’t a typical setting. Negative camber is common, however, on the left rear. A common setting is -2º for both rear tires.

Camber Starting Point
LF     RF
+1º    -2º

LR     RR
-2º    -2º

If you’re flying down the straight and as soon as you cut the wheel, you’re witnessing more flips than an Evel Knievel highlight reel, you are not going to win many races. That sudden snap flip when cornering is called a traction roll. With high speeds and a lot of cornering forces, it’s fairly common in certain classes of oval racing. Any car can flip over if a large enough force is applied to it, and the more traction the outside tires have, specifically that right front, the less force is needed to cause a roll. A traction roll problem can be extremely frustrating. Instead of pulling your hair out, try these tips:

Right front tire with less grip. Less traction at the right front of the car means less traction rolling. For a Sportsman Mudboss this may mean going from a Kumho tire to a SCT tire.
Firmer Insert: If the rules allow, trying a firmer insert will help prevent the tire from deforming or rolling over, which can initiate a traction roll.
Lower center of gravity. Consult your rules on this move. If the class you’re in allows the LCG chassis, install it. If the Low-CG chassis isn’t an option, cutting the springs may be. This will lower the chassis. Again, consult your rules first. Moving the lower shocks mounts further out on the suspension arms will also lower the center of gravity.
Decrease right front camber. If you’re running -1º, try -2º. Try even more. It’s counterintuitive to why we use camber, but we’re trying to add so much camber that the tire doesn’t reach its maximum contact patch when cornering. The idea is to prevent that outside edge from digging in and rolling the car.
Stiffer right front spring. Most likely different springs are not allowed, but if they are, a stiffer rate spring will help alleviate a traction roll problem. Please note that adding spring clips or spacers does not increase spring rate.
Thicker right front shock fluid. While changing springs usually isn’t an option, changing shock fluid usually is. Since it’s next to impossible to tech, most tracks allow you to run any shock fluid you want.
Track width. Increasing track width by using different offset wheels and/or wider hexes will reduce traction rolling.
But weight, there’s more. Check those rules, but if you’re allowed to add weight, add weight to the left side of the chassis–as close to the edge as possible.

To get on the Salvas MUDboss fast track, we went right to the source, the mastermind behind Mudboss racing, Eric Salvas.

RC Truck Stop:
Tell the RC Truck Stop community a little about your RC background?

Eric Salvas:
I’ve been racing RC cars since 1989–30 years now. All oval—carpet, paved, dirt.

RC Truck Stop:
That’s a lot of experience. When did you come up with the Mudboss body idea and the concept behind the class itself?

In the spring of 2014, the idea evolved from the fact that an entry-level class in oval racing was not present. Also, I wanted to bring the ‘easy way’ of RC back into the hobby. I wanted to bring a new class that would bring new blood to the hobby. I decided to go with the Traxxas Slash chassis because it’s sold almost everywhere, is inexpensive and parts are readily available. I decided to design a body that would suit better the oval racing tracks that we were running on weekly, loose dirt oval. Being from the North East, the premium dirt oval full-scale class is the Super DIRTcar series modifieds. I designed a body that would almost be race-ready—predrilled, pre-bent. In matter of minutes, the body is assembled and ready to go!

RC Truck Stop:
What’s the story behind the Mudboss name? Is it a play on the mud bus name that has become somewhat synonymous with eastern dirt modifieds?

Mud bus was a name used in the early ‘80s by Maynard Troyer, a full-scale dirt modified builder, on one of their own chassis designs. I decided the MUDboss name was good to use for my new class that was, at first, mainly running on loose dirt oval tracks.

RC Truck Stop:
Did you ever imagine this class taking off as much as it has?

The first five bodies were handmade. It quickly came obvious I could not supply them fast enough, so the CAD conception came into effect to have these CNC cut. Doing so, I also made sure all these would come out exactly the same. The first summer, 100 or so bodies were made. Now, in 2019, it’s twice this number monthly!

RC Truck Stop:
That’s a lot of growth. How has Mudboss racing changed since it first started?

At first, only one class was available, 13.5 brushless motor with 2S LiPo. But with popularity, and improvement in electronics performances, that class became way too fast for newcomers. Mainly, the rule set has not changed much from the beginning—stock parts, no modifications to the chassis and suspension. But in 2019, we implemented a new class structure that would fit all racers needs. We now have the Sportsman class, which is stock 12-turn and XL5 electronics, fixed gear and any Traxxas tires); Small Block class, 17.5 spec ESC, fixed gear and Traxxas spec tires); Big Block class, the ultimate Mudboss class with 13.5 blinky ESC, HOOSIER tires and LCG chassis. This way, we now have a true entry-level class, Sportsman, and a class that fills “the need of speed” for the experienced racer, Big Block.

RC Truck Stop:
Those sound like solid improvements and something for everyone. What do you have planned for the future of Mudboss racing?

As of now, I want to bring stability of the class structure, so no ‘big’ change in the near future! Stability is key in RC health.

RC Truck Stop:
What tips do you have someone assembling a Mudboss body?

The body comes predrilled, pre-bent, with 32 supplied screws/nuts. Only a few handmade final bents are needed to complete the build. Simply bend all the edges to a 90º angle so the body fits nicely. All useful info is right up there on our Salvas MUDboss Facebook page.

RC Truck Stop:
Do you prefer or recommend wraps or paint for these bodies?

Wrap is really the way to go. First reason, the look! A lot of full-size wrap companies offer clone style wraps of real dirt modified designs. Secondly, longevity. I have bodies that are close to four years old, and been rewrapped multiple times. One negative side of using paints, is that, if not handled properly, paint could harm the plastic—polycarbonate—and crack the edges. Racers that choose paint should make sure to use real thin layers. The aerosol in paint is real cold and it could damage the folds.

RC Truck Stop:
After the get the body done, it’s time to hit the track. Do you have any racing and setup tips for someone just starting out in Mudboss racing?

There are as many setups as there are tracks and racers. The cool thing is not much can be done to the cars. Mainly the only thing that we can work on are shocks and camber. The best advice would be to talk to local, fast Mudboss racers and ask for advice. The Mudboss community is strong and helping others is the best way to improve the popularity of the hobby . . . and class.

RC Truck Stop:
And, speaking of racing, what is the biggest race of the year for you?

Being an oval racer at heart, the biggest race on my calendar is the Snowbird Nationals down in Florida. That’s a carpet race, but the Mudboss class was kindly added by race director Mike Boylan a couple years ago, and it’s become one of the popular classes of the event. This is exactly what is cool about the class, the exact same car can be raced on dirt or carpet. Only a few minor changes are made for Snowbirds, such as the tires since foam tires are used on carpet at this event.

RC Truck Stop:
Thanks, Eric. Hopefully we’ll see you at the track.

The Internet is an amazing volume of information. Some of it’s actually useful. Of course, I hope you find this article useful. If you want even more, I found a few resources online that I believe have good information. One is Allen’s R/C Cars, a hobby shop and track, and a second is Murfdogg Racing, a dirt oval manufacturer and retailer. Allen’s R/C Cars’ info is geared more towards carpet, but if you want to learn the basics, it’s a great resource. On Murfdogg Racing is Chassis Tuning 101, Matt Murphy’s Dirt Oval Chassis Tuning Guide. This guide is exceptional. The only advice he gives that I disagree with is part of what he says about toe-in and toe-out. I believe slight toe-in increases straight-line stability. It makes the vehicle track straight, not twitchy. Decide for yourself. Another resource if you’re looking to take a Traxxas Slash dirt oval racing is, well, Traxxas. See the link below and check out how they built some Slashes to go fast and turn left.

Allen’s R/C Cars
Murfdogg Racing

My choice of race venue for the Mudboss is Thunder Alley R/C Speedway in Wilson, North Carolina. In addition to the dirt oval track, this outdoor facility features a large off-road track, which is perfect for 1/8 scale and short course action. There is also a well-stocked hobby shop, World of R/C Parts, on site. Check the schedule or give a call before heading to the track, but they race oval on every other Wednesday evening and every other Saturday. They also frequently have trophy and cash-payout races, as well as points series. In fact, the first time I raced this Mudboss was a trophy race.

In my first qualifier I fought a horrible push, but ran a consistent race. That’s code for I was slow but didn’t crash too much. But, of most importance, at least to me, I had a lot of fun.

I made a few changes for the second qualifier, such as front camber. The car still wouldn’t carve turns, but it was clearly faster. I was on pace to go a lap faster. I might have been able to go two laps faster than my first effort with some good driving. Instead, I decided to park my race car on its roof on the back straight. I couldn’t pick a worse place to crash. The push (aka understeer) was better, but still required me to run wide down the back straight. On occasion, the tires would harmless hum as they brushed the yellow corrugated pipe. Well, this one time the right front tire didn’t hum. It caught and over I went with no corner marshal in sight. My fault, not theirs. Overall, it was still a good run. Not enough for the A-main, but I was in easy position to bump up. I’m not one to count my proverbial eggs before they catch, but it was looking good.

As it turned out, I didn’t even have to run the B-main. I started near last in the A-main, but with changing track conditions and a few tweaks in the pits, my push was replaced by slightly loose. Well, lose is fast. I wouldn’t say I was anything close to a threat for the top three, but I worked my way through a large field, had some good luck along the way and finished fourth. Not bad and certainly a respectable finish.

Want to try dirt oval? I hope so. There’s a reason why dirt oval is one of the fastest growing segments in RC. Thanks to classes based on popular and relatively simple platforms like the Traxxas Slash, dirt oval racing is fast, fun and action packed. With the Salvas MUDboss, specifically the Sportsman class, I was able to quickly, easily and inexpensively get in on competitive dirt oval racing. I had a blast, and after just one race at Thunder Alley, I was hooked and couldn’t wait to go back.


You might also be interested in these Mudboss articles: “7 Ways to Cheat at Mudboss Racing” and “Mudboss Setup Tips & Tricks.”

Hoover Graphics & Race Wraps
Salvas MUDboss
MUDboss Rules
SMC Racing
Thunder Alley R/C Raceway
World of R/C Parts

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