Tuning Your Mayhem

Whether you have a Mayhem RTR, Mayhem Pro, or the new Mayhem ST, you are bound to run in some less than ideal conditions. For some people it’s sand, others mud, and still others—well, I’ll just say that these cars have seen just about any kind of conditions you might want to throw at them. While your vehicle may run just fine for the first few times, you’re going to need to wrench on your ride from time to time to ensure that you will enjoy the same level of performance each and every time you take it out.

Shocking Results

The first time I had taken my personal Mayhem RTR out to race, the car turned really well in one direction, yet turned really poorly in the other. This car had been run a lot in my backyard and at my father’s cabin in northern Wisconsin, and I had beaten it up pretty well. I discovered back in the pits that during one of my “thrashings,” I had bent the right front shock shaft so much that I only had about ½-inch travel on that shock. I also noticed that there was quite a bit of buildup on the bottom of the shock bodies on three out of four shocks. It was definitely time for a rebuild.

I headed into the Hobby Store and picked up some necessary parts. I knew with the amount of buildup on the shocks, that the seals would need replacement as well. I grabbed two Sportwerks Shock Rebuild Kits (SWK3024), one for the front shocks and one for the rear, along with some Titanium Nitride replacement Front Shock Shafts (SWK9005). Once I had the old oil out of the shocks, I pulled the other three shafts out of the bodies and rolled them on my pit table to make sure they were straight, and they were. With the new seals installed in the shocks, I reattached the pistons, and applied some shock oil on both the seals and the shock shaft before I reinserted it. This is a key point that some hobbyists miss. If you try to insert the shock shaft through a dry O-ring, the friction can tear that new seal, leading to problems down the road. Following John Adams’ suggested setup, found on www.HorizonHobby.com, I filled all four shocks with Team Losi 40wt Silicone Shock Oil (LOSA5226), bled them (FYI, these are some of the easiest shocks you will ever find to bleed), and was almost ready to reinstall the shocks. I noticed that my front shock tower was also tweaked, so I took the time to upgrade the front tower to the 5mm thick Front Shock Tower (SWK9143) which should resist bending better and has additional mounting options for the upper shock mount. My last change to the shocks was to install a full set of threaded shock adjustment collars (SWK3012) and a set of medium red front (SWK3049) and rear (SWK3059) springs to give the car a more sure-footed feeling around the track.

Feel the Difference

I don’t clean my car as often as I should, but the last time I did give my car a thorough cleaning, I noticed that there was a build-up of gunk under my center diff. I took a closer look and noticed that the screws that hold the diff halves together had backed out, allowing some diff fluid to escape and drip onto the chassis. After talking with John Adams and Anderson Yau, two drivers who have a ton of experience with this car, both suggested that since I would have the diff apart anyway, I should double up on the diff gaskets. I picked up two sets of seals (SWK3086), which would allow me to double up the seals on all three diffs.

With the diffs out of the car, I sprayed the chassis down with some Dynamite Nitro Car Clean (DYN5505) to get all the buildup off the chassis. While that was drying, I turned my attention to the diffs themselves. The kit lube was really thick and gummy, and I needed to really blast out the housings and the gears to get all the old lube out. Once everything was cleaned out and dry, I started rebuilding, starting with the front diff. Again I followed John Adams’ setup and filled the front diff with 5000wt Sportwerks Silicone Diff Oil (SWK2906). Now I say filled, but you actually only want to use enough diff oil to cover the cross pins. If you over-fill the diffs, the diff action can feel overly firm, almost like you needed to back the gear mesh off if you could. I proceeded to fill the center diff with 10,000wt oil (SWK2903), and the rear with 3000wt (SWK2905). With everything resealed and ready to reinstall, I took a couple extra seconds and cleaned out all the bearings thoroughly before I reinstalled the diffs and input gears.

Them’s the Brakes

Before I reinstalled the center diff, I inspected both the brake pads and the brake rotors as well. I was glad I did, as I found one of my brake rotors was warped, while the other had quite a bit of brake wear on it. I removed both the front and rear rotors, along with the brake pads to see exactly how much life they had left in them. I laid some fine-grit sandpaper flat on my workbench and worked the rotors back and forth across it until all the buildup was removed. I was able to clean the brake pads off using fine grit sandpaper as well, just scuffing them up enough to remove the glazing. You don’t need to go crazy here, just scuff them enough so that any shiny spots on the pads have been removed or treated. Also remember that you may need to readjust your brakes, depending on how much material you needed to remove to deglaze the pads.

I tried to re-flatten the warped rotor , but it was never very true. I decided to simply replace the warped disc with a new one (SWK3096). I don’t have a ton of experience with nitro cars’ braking systems in race conditions yet, so I opted to stay with the stock brake system. I could have upgraded the brakes to the Quad Brake Set (SWK9194), but I decided to stick with what was more familiar to me.

Un-Bind That Suspension

Much like a bent shock shaft, a bent hinge pin can prevent your suspension from working as it should. With the shocks detached, lift the A-arms and let them drop. If they hang up or fall slowly, there’s something bound up and you need to fix it. Remove the inner hinge pins and roll them on a flat surface, such as a setup board or another flat surface to see if there is any wobble. If there is, then it is bent and should be replaced. If they are straight, then you’ll need to look elsewhere. On my personal car, my front hinge pin brace was bent, while my hinge pins were perfectly straight. I simply replaced the brace with one from the Mayhem Pro Set (SWK9133) and I was good to go.

The hinge pins aren’t the only place where your suspension might bind up, especially on the front end. Check the inner bushings that the upper hinge pins mount to for the upper wishbone in the shock tower; if there is binding there, that’s your problem. You should also inspect your upper and lower pivot balls from time to time. They can be bent during a hard impact and yet it’s not easily visible that they have been bent. Much like your shock shafts and hinge pins, roll your pivot ball along the edge of a table; if it wobbles, replace it. Finally, any built-up dirt and crud around the hinge pin holes or suspension mounts can cause the suspension to work inconsistently. You can use a pipe cleaner to clean any gunk out of the hinge pin holes and suspension mounts, while a firm bristled toothbrush works well to scrub things clean.

Keep That Engine Running

The Sportwerks .26 engine that comes with the RTR Mayhem is an absolute beast, but you need to take care of it if you want it to run well tank after tank. Using the right fuel is one of the biggest keys to success. If you don’t plan on racing your Mayhem, stick with a sport blend of fuel, such as Blue Thunder’s 20% Sport Formula (DYN2320). This type of fuel is specifically blended with hobbyists new to tuning nitro engines in mind. The addition of the ZX-7 additive protects the engine if it is tuned too lean, since the lubricant will actually begin to combust and stall the engine out instead of causing excessive damage to the piston and sleeve. If racing is in your future, then switching to White Lightning 20% (WTL420) might be a good idea. White Lightning is blended with all-out performance and competition in mind, unlocking the hidden potential in the engine. And these fuel suggestions aren’t just applicable to the Mayhem’s .26 engine; you can also follow these guidelines with your Mayhem ST’s .26 or the Sportwerks .21 as well.

Once you’re done running your car or truck for the day, don’t even think about just tossing it in the closet until the next time you’re going to run. I don’t know how many people I see struggling to get their engines running, all the time saying, “I don’t know what’s wrong, it ran great last week?!?” I’m willing to bet that the majority of these people never even thought about using after-run oil following their last run of the day. After-run oil will help prevent the different castors and other fuel components from breaking down and gumming up the bearings, piston, and sleeve. You can use Marvel Mystery Oil, available at many auto parts stores, or you could use hobby-specific after-run oil such as Prather After Run Oil (PRA7140). Simply put a drop or two into the carburetor and rotate the flywheel by hand to move the after-run oil around in the combustion chamber.

Save That Flywheel

Since its initial release last year, many Mayhem Pros and Mayhem RTRs (and soon to be joined by the Mayhem ST) have found their way to racetracks around the country. While the hand-starter is extremely convenient, the additional one-way bearing on the back plate can cause additional drag on the engine, reducing the horsepower. You can improve the engine’s performance by replacing the hand-starter with an Eliminator Back Plate (SWK8057) and a starter box. But in addition to the new back plate, you’ll also need to replace the stock engine mounts with non-pull start mounts which allow the flywheel to sit lower in the chassis, otherwise the starter box wheel won’t contact your engine’s flywheel. The standard engine mounts that come with the Mayhem Pro (SWK3228) work perfectly to lower the engine in both the Mayhem RTR and Mayhem ST, allowing you to use a starter box such as the Sportwerks Cyclone Universal Starter Box (SWK9902).

Before you install your engine back on the chassis with the new mounts, you’re going to need to prepare the chassis to accommodate a starter wheel. You will need to open up the flywheel opening in the chassis with a file or rotary tool, otherwise the starter wheel may rub on the chassis, which could ruin it. You don’t need to remove a lot of material, just enough that there is approximately a 45-degree slope at the leading and trailing edges of the flywheel opening. If you own a Mayhem Pro chassis, this has already been done for you. Once this is done, you are ready to reinstall your engine. And don’t forget to use some Loctite on the engine mounting screws to prevent them from vibrating loose.

Before	After

The entire Mayhem series of vehicles can provide hobbyists with endless hours of fun and worry-free operation, but some basic maintenance will help your car or truck run longer and stronger. The steps set forth here are easy enough that just about anyone should be able to perform them. So go out, rip up some grass, throw some dirt around, but most of all—have fun!