Here's a carpet guide that I found in RC Driver magazine.
I put together this guide for Carpet racing. It's a good manual for newbies, but it has somethings veterans might not have heard anything about. I gradually add more as I find more ideas & racing tips. MAKE ONE OR TWO ADJUSTMENTS THEN TEST YOUR CAR, OR ELSE THE CAR WILL HANDLE HORRIBLY!
Chapter 1
-----------------------Asphalt vs. Carpet------------------------------
On asphalt, a 1/10-scale touring car reacts in a realistic way, so much that the dynamics are similar to a full-size car, you can drift into corners & the car itself has a degree of slide. You also have the ability to experiment with grooves, depending on the track conditions & your car set-up.
This isn’t the case on carpet though, where most of the racers who are fast look like they’re driving “dot to dot”. If you aren’t 5mm from the board, you’re driving a bit too slow. Racing T.C.’s on carpet with foam tires is much like driving a slot car. Everything happens instantly & there’s NO room for mistakes, especially in the 19-T & Mod classes.
----One Common Car-------
The most popular car that I’ve seen is the Tamiya TRF-415MSX. Mainly, I’ve seen it at asphalt races, but it can be converted to be very aggressive on carpet. I’m not saying that you should ditch the car you have now to get a 415-MSX, I’m just saying that it’s the most common I’ve seen besides Corally’s & X-Ray’s. The U.S., especially in the mid-west (MICHIGAN, YEAH!!) & on the east coast, indoor carpet racing is a favorite among T.C. racers.
Many of the set-ups that are excellent for asphalt are horrible on carpet. For one thing, most carpet surfaces have insane amounts of traction, especially when you’re using foam tires & traction compound. From my 5 years of racing at CEFX, everything that works on asphalt is exactly the opposite on carpet.
--------------------Asphalt--------------------------
Most of the time, I‘ve seen racers with belt-drive cars use a front spool & a direct center pulley when they’re racing on asphalt. While sometimes a spool tends to bind the car, it does allow you to be able to use the brakes to the full extent of the cars ability. With a one-way in the front, the brakes seem not to work as effectively. Add a center one-way & it becomes worse. A spool & direct center pulley are a very popular tuning method that allows you to use brakes in situations where you want to out-brake a competitor, such as a tight 180-degree hairpin, like the one a Tamiya America.
People often ask why on asphalt, diffs aren’t used. Well a ball diff can work, but there’s a mysterious effect when using diffs, called diffing. Diffing occurs when one wheel is lifted off the track by high-cornering speeds, sending the power to the other wheel that’s on the ground, causing that end of the car to pull to the side. Throughout a race, this will gradually decrease your lap times. A one-way or a spool will lock the front end during acceleration & give the driver a little extra advantage when exiting corners. With a front diff, you’ll have good turn-in, but you’ll lose exit speed in the turns. Setting a touring car’s droop and front & rear toe in can make or break the car’s handling. Add a bit of rear toe-in to make the car more stable when entering turns.
Chapter 2
---------------Carpet Set-up Tips--------------------
Front drive options
Save the spool & one-ways for asphalt when carpet racing season starts. I’ve yet to see a racer use that combo when racing. You’ll need a front diff & a direct center pulley! Because carpet has an INSANE amount of traction, diffing is almost non-existent. The front diff gives the car the amount of turn-in it needs & the drivability to give you the confidence to go fast. And the suspension should be set much stiffer than it would for asphalt. The tires tend to be much more stable, which minimizes diffing.
-----------------------------Stiffer is Better------------------------------
Flexible flyer RTR touring cars aren’t ideal for carpet, but it only takes about a day to a week to turn your RTR into a full-blown aggressive racer. You want to get your car as stiff & rigid as possible. If you have a TRF-415MSX, Tamiya makes a stiff & rigid 4mm chassis that is ideal for carpet. While the standard MSX chassis is rigid, the stiffer your car’s suspension is, the more grip & stability the car will have, especially on carpet. Always check with your car's owner-manual, hobby shop employees or the local hot-shots before deciding on parts for your car.
----------------------------Wider is Better--------------------------------
Get ready to make your car as wide as the rules allow. This isn’t the most common method to make a car more stable, but it works. To me, this allows the car to lean in on the turns, especially hard, tight sweepers. Even a few millimeters will make a car that’s a pain to race into a very stable, aggressive competitor. On asphalt however, the wider the car is, the less responsive it becomes, so don’t make any permanent mod’s, unless you have a seperate car for asphalt.
If it’s your first time on carpet (which I doubt many of you have been on carpet before), take a few slow laps, because carpet tends to make a car feel more responsive in an un-natural way. Widening the car takes a edge off of that feeling.
----------------------Less Toe-in------------------------
On carpet, rear toe-in isn’t needed as much as asphalt. On carpet, it’s all about how hard your car can turn-in, so the less rear toe-in, the faster your car can turn-in. Rear toe-in can be reduced by changing the rear suspension arm mounts, at least on my TC3, I know, VERY OLD SCHOOL!!!
--------------------Stiff Shocks-------------------
I’ve found that many racers only need to go 1 or 2 oil weight’s to find the best set-up for their car on carpet. Mostly, I’ve seen racers switch to 2 or 3 hole shock pistons. Sometimes when I talk to racers about the best set-up for carpet, they say that "Using a 3 hole piston makes my car fell lazier.", & sure enough, they do on most cars. When choosing springs for carpet, stiffer is much better. The main rule is when buying springs for carpet, the front should always have a stiffer spring, because if you have a lighter spring in front, the rear of the car will tend to want to over-rule the front. For my TC3, I use purple springs (30 lbs.) in front & red springs (22 lbs.) in the rear. But be careful when figuring out the oil weight & spring rate. If you use an oil that’s too thin with a spring that’s too stiff,
The car will act like a pogo stick with very bad handling.
---------------------Sway Bar Options----------------------
Racers usually favor a heavy sway bar in the front of the car with no sway bar in the rear. The heavy front sway bar calms the cars steering & eliminates twitchiness. By not using a sway bar in the rear or using a light one, the car is allowed to roll just enough to make it easier to drive. When using sway bars, it’s a good idea to check with other local hot-shots & experiment with different combos.
---------------------Caster & Camber-----------------------
On carpet, a car’s camber & caster settings can impact its handling much like on asphalt, but you should think about how the foam tires will wear. If your local track has a tight course, I would suggest 2-degree caster blocks. If it has a few sweeping turns, I would suggest 4-degree caster blocks. Increasing caster on most cars will give it more steering entering turns, but less steering exiting turns. More caster will also make the car more stable in bumpy conditions. You can add even more caster by placing shims on the front of the suspension blocks to raise it. More caster seems to calm a car down. Just be sure to never use negative caster, but on some tracks, the amount of caster the car needs may be extremely negative to ensure normal tire wear.
--------------------------------Tire Options-------------------------------
Tires are the main tuning counter-part when racing on carpet, so before deciding on new treads, it’s a good idea to talk to your local track’s top racers. Just be sure to run harder tires in the front. This works for me, but experiment with compounds first. Softer tires in the rear will have more rear traction & harder tires in the front will make it so that the rear doesn’t try to switch sides with the front. Another thing to do is buy or borrow a tire truer to trim the tire to a reasonable size. When truing tires, be sure to think about roll-out & gearing. Always have a can of traction compound in your pit box. It’s all about the way you apply it, so watch what the fast guys do.
-------------------------------Roll Center----------------------------------
Normally when racing on asphalt, racers keep their suspension blocks slammed. If the car needs a little more stability, experiment with raising the front suspension’s block rearward 0.5mm to make the car have less dive angle under deceleration, but you might lose a bit of steering, but it’s O.K. if you’re looking for a more stable car that can be driven hard. This is especially a good tuning tip when the track bite is very high.
------------------------- Ball Bearing Tips-----------------------
To get a bit more spin from your bearing’s, here’s how.
Remove one of the seals with an Exacto-Knife or dental pick.
Blast the bearing clean with motor spray.
Use a few drops of high quality ball-bearing lube to lube the bearing.
Replace the seal & install the bearing.
---------Battery Connectors-----------
Many RTR's come with Tamiya, or JST, connectors. These can build up heat & reduce the batteries power, & on some occasions could melt together because of the heat build-up. It's like putting a garden sprayer on a firehose. A simple up-grade are Dean's connectors. These can withstand heat build up & suck more juice faster from the battery.
This is the preferred method that hard-core racers use-most competition ESC's have 3 tabs to solder the motor & battery to, which in turn allows them to use no connectors so there's barely any heat build up.