Allen's R/C Cars

2008 King of the Wings Field

 

 
Traxxas Slash Modifieds (Oval)

    This is a "beginner's guide" to help get your Traxxas 2wd Slash up to speed in the Midwest (UMP) Modified class on carpet, or in any class where you intend to run the Traxxas 2wd Slash on an oval for that matter. Within this guide are just a few simple, basic things to do to get you "in the ball game". Even though it is a spec class and there aren't very many tuning options available on the Slash; we all know there are still a few "tricks" that experienced racers have figured out to help take this off-road vehicle and turn it into a pretty solid oval machine. Hopefully this guide will bring the beginner racer up to speed on some of the basics to help bridge the gap between the experienced and novice racers and make this class the most competitive class possible.

NOTE: This guide is specifically aimed at Slash vehicles being raced at Allen's in the Slash Modified class. However, this should still be helpful for anyone else running their Slash under similar rules on an oval as well.

 
Shocks (Ride Height & Shock Travel)

    Obviously this is the first place to start when trying to turn any off-road vehicle into an oval superstar. Off-road vehicles are built with plenty of ground clearance for obvious reasons. In oval racing, particularly on carpet, we dont need this much ground clearance. A lower ride height will do two things... First, it will help minimize the vehicle's tendency to want to traction roll. Traction rolling is where the vehicle grips too much in the corner and flips itself over. Second, it will make the vehicle a little more aggressive reacting and more predictable. Both good to have in oval racing especially on carpet.

    When faced with having to tune your vehicle with stock components only, you are limited on options available to be able to lower the ride height. Lets start with the front shocks first. The Slash comes with what is called pre-load spacers already installed on the shocks and a few spares in the box to tune with. These are the spacers that rest above the springs to help "pre-load" the spring raising the ride height of the vehicle. On the front shocks, the first thing to do is remove all pre-load spacers to start with. This will allow the vehicle to ride as low as possible naturally.

    Unfortunately, this isn't all you need to do to the front shocks. In addition to the ride height, the front shocks also provide more droop than is needed for oval racing. Droop is the amount the arms hang down when the chassis is lifted off the ground. With the front arms allowed to travel so much this provides too much weight transfer for oval racing, especially on the carpet. To reduce this, you need to add spacers inside the shock under the piston. You will need to take the top cap off, empty the shock fluid out, remove the lower rod end, and remove the shock shaft (with the piston still installed). Slide the spacers (limiters) on the shaft (we recommend about .350" worth) and then reinstall the shock shaft. The RJ Speed 1/8" nylon spacer kit (#5253) works great and is what most guys are using here at Allen's. This will limit the amount the arms can droop down as well as help pull the ride height down just a little closer to the minimum (.350" just barely pulls the arms up slightly higher than where the vehicle would rest with no pre-load spacers installed).

    The final two things to worry about on the front shocks is the shock oil weight and mounting location on the arms. For shock oil (on carpet), we recommend starting at 50wt oil with the stock 2-hole pistons. For dirt, you may want to go a little lower to about 40 - 45wt. For shock location, we recommend running the shocks on the outer of the two available holes in the front arms.

    Next, we need to look at the rear shocks. These will be much less hassle than the fronts. We do not recommend any internal limiters in the rear shocks. You will find, especially on the carpet, that you need the left rear tire to travel as much as possible so it stays on the ground as much as possible despite how much the chassis may lean in the corners. This will help keep the differential from unloading when the chassis tries to lift up the left rear tire and rob you of forward drive off the corners. For shock oil, we recommend, again, starting with 50wt oil for carpet and maybe going down to 40 - 45wt for dirt. As for mounting location on the arms; again, we recommend mounting both shocks on the outer most available hole on the arm. And last but not least, we recommend using one large pre-load spacer on the left rear and one medium spacer on the right rear to start with.

Starting Setup (Shocks)
Internal Limiters: Front = .350" / Rear = none
Pre-load Spacers: Front = none / Rear = large (LR) , medium (RR)
Shock Oil: 50wt all the way around (carpet) / 40 - 45wt all the way around (dirt)
Shock Location: Outer most holes on all four shocks

 
Tires & Camber

    If you are mandated to run the stock Traxxas Slash tires like we are here at Allen's, you will have three different choices of tires available (in stock compounds) as there are three different tread tires that comes on the Traxxas Slash depending on which Ready-To-Run kit you get. Your choices are:
    - the Traxxas "Spec" SCT tire (has the least amount of "bite", but low wear. Works great on carpet)
    - the BF Goodrich Mudd Terrain T/A tire (has slightly more bite than the "original spec" with still minimal wear. Also works great on carpet.)
    - the Kumho Venture MT tire (provides the most bite, sometimes too much on carpet, but also noticeable wear especialy on carpet)

NOTE: Be sure you DO NOT buy the S1 compound tire for any for the three treads. These are not legal as they are not the stock compound tire.

    While all three different tread tires will perform differently; so far it has been proven that, at least on the carpet, all three tires can be made to be competitive and get you an A-main win. On carpet, a lot of times too much bite is a bad thing which can, and will, make the car want to traction roll. The key is to find just the right about of traction that puts you on the edge of traction rolling, yet keeps the LR tire planted enough not to unload the differential causing you to lose forward drive. All three tires can be set up to achieve this. The Original Spec SCT and BF Goodrich Mud T/A tires are probably the more versatile tires for carpet. The Kumho Venture MT tire is also a nice tire on the carpet, especially on days where the traction is on the low side. However, it may take a little more work with this tire to keep the vehicle from wanting to traction roll.

    Reguardless of which tire you choose, or which ones comes on your vehicle, you need to follow some basic guidelines to make the tires on your vehicle work. First, if your car tends to want to traction roll, you can add black electrical tape to the outer edge of the right front tire. This will keep the tire from over biting on the outer edge where the tread meets the sidewall and help calm the vehicle down. We recommend doing this to start with reguardless of which tire your vehicle has. We recommend using the full width of the tape and applying it so that about half the width of the tape covers the actual tread of the tire and the other drapes down the sidewall. This will be the single biggest, as well as easiest, thing you can do to your vehicle to keep it from wanting to traction roll.

    The second thing you need to look at is how much camber you run. We recommend starting with -1 to -2 of camber on the RF and about -2 to -3 of camber on the RR. You will not want to use much, if any positive camber on the left sides. Maybe +1 on the LF. We recommend keeping the LR at -2 to -3 just like the RR. This will add some stability to the car, particularly on the straightaways if(when) you have to turn to the right to avoid crashes.

    Also remember that when adjusting camber, you may need to reset the front toe. Generally you will want the front toe pretty even, or maybe just slightly toe'd out. A half turn to a turn on the camber link won't usually require much, if any adjustment to the toe links. However, any more than that and you may want to hit the toe link for a half turn or so as well.

Starting Setup (Camber)
Traxxas Spec SCT
LF: +1RF: -3
LR: -2RR: -3
BF Goodrich Mud Terrain T/A
LF: +1RF: -2
LR: -2RR: -2
Kumho Venture MT
LF: +1RF: -1
LR: -2RR: -2

 
Gearing

    Gearing is pretty straight forward and there does not seem to be any sort of sweet spot. If you get it close you should be ok, especially indoors on the carpet. We recommend starting with a 21/86 (pinion/spur) on the indoor carpet track. This gear has won several races in a row here at Allen's with a different driver each time. One tooth one way or the other on the pinion will not make a noticeable different in speed on your fastest lap. However, too big of a pinion might result in loss of performance near the end of the race due to overheating.

Starting Setup (Gearing)
21/86 (pinion/spur)

 
Tuning Tips

    Tuning the Traxxas 2wd Slash for oval racing is pretty basic and usually pretty simple. The Slash out of the box does not have as many tuning options as most race vehicles, so this will keep it simple. You will find the main things to tune with during raceday will be your shock pre-load spacers and the camber, particularly on the RF. Carpet racing is a little more beginner friendly than dirt racing as the track conditions won't usually vary drastic enough from week to week to require a major overhaul to your setup.

    However, don't let the fact that it is carpet racing fool you. Track conditions can, and will change throughout a raceday, and can still vary slightly from week to week. One week you may have your vehicle handling just right, and the next week you may find that you are a few tenths of a second a lap off what you ran the previous week and struggling to get it back. In most cases you should be able to tune the car with the camber, especially the right front. A mere half turn on the camber link can be the difference of running a 5.3 fast lap vs. a 5.4 fast lap. This has proven to be the case on several occasions, even for the experienced racer.

    On days where the track seems to be lacking the grip it had before don't be afriad to add a little negative camber to the right side tires. On days where the bite seems to be more than usual and you are struggling to keep the vehicle from traction rolling, take a little bit of camber out of the right sides, particularly the right front.

   Don't ignore the pre-load spacers or shock oil either. Adding or subtracting pre-load spacers from one corner or another can make a pretty drastic difference in the handling of your vehicle. You are basically changing the cross weight and attitude of the chassis. Shock oil will also have a major affect on handling and is probably one of the main foundations of the setup. However, the shock oil probably won't need to be adjusted much once you settle on something that works for you.

 
Summary

    Hopefully now you have a pretty decent understanding of how some things affect your Traxxas Slash on the oval track. If you make the recommended starting point changes to your Slash then you should have a Slash capable of contending for a spot in the A-main, at least on the carpet. The rest will be up to you. Remember, the Traxxas Slash is a simple and basic vehicle. If you keep things simple in how you approach setting up your Slash then you will find more success than when you try to over-analyze things.

    If after following this help guide you are still struggling to find speed; don't be afraid to ask one of the experienced racers in the A-main for assistance. More often than not they will be more than willing to help get you on the right track. As with any form of racing, things evolve and we learn to new things every week. Maybe they have found something that hasn't been covered in this guide that can help get you going better.