Technical and Racing Tips
Main RS4 Rally Page | Manual | Spec Sheet | Parts List | Option Parts | Building Tips | On-Road Tire Tips | Updates | Electric FAQ
Since many of us here at HPI Racing compete on a regular basis, we come up with tuning, racing, maintenance and general technical tips constantly. This page will collect all the hints that we have gathered plus pull together the tips we get from our email bag.
Many of the tips in the future will have thumbnail photos of what to do, where to put a part, etc. If you click on one of these thumbnails, you will download a larger (5 to 6 inches across, 40K to 80K) photo of the process involved with the tip.
Off-Road Chassis and Suspension Setup
On-Road Chassis and Suspension Setup
Tire Selection and Chassis Width
Radio Equipment and Electronics
Maintenance Tips - Find out how you can maintain your car in the best condition! Split between general maintenance and "serious" racing tips
Setup Sheets - Blank setup sheets for nearly all of our car kits, plus setups that have worked great for our team drivers!
General Chassis and Suspension Setup
For modified racing, you should set up your car a bit stiffer than for stock, because the car is going to go faster into turns. Go up one piston number, a shock oil weight or shock spring.
The sway bar set is generally necessary only to fine-tune the car, maybe to get a little more steering.
We recommend you have a one-way diff for use on very large tracks with long straights. Since only the rear wheels will brake, the tendency for many racers, especially those who are not used to the one-way, is to spin out while braking. Most people do not use the one-way diff, and reserve it for very special track conditions. If you spin out while using the one-way diff, ease onto the brakes. Advance to full brake gradually and slowly. If you can train yourself to brake sooner, this won't be much of an adjustment.
Even though you may have the belt tensioner attached, the belt should ride loose, just enough to catch the gear teeth while not slipping.
To have your steering slop-free: he has his servo saver screwed very tight, about 7 or 8mm off the chassis. This will help make sure the steering servo centers the wheels correctly, but does not allow much room for the servo saver to protect the servo in case the front wheels scrub a wall.
If
you want to tighten up the steering linkage, you can take out the z-bend
piano wire and use HPI's short purple ball ends (# Z137) and a tie rod
and ball joint set to connect the bell cranks. This removes some of the
slop in the steering and the short ball ends prevent the ball joints from
rubbing the underside of the upper deck. The measurement from the center
of the ball joints remains the same at 48mm. This modification also allows
you to adjust the Ackerman angle, but most racer do not mess with this!
Another way to tighten the steering is to use two 4 x 8 x 3mm bearings
(#B017, $14.00) on the pilot shaft of the steering arm instead of the
plastic bushings.
Off-Road Chassis and Suspension Setup
For bashing around your yard, the settings from the manual work very well. If you are running on very rough ground, like at a construction site, you may want to add 2mm to 4mm of ride height to the shocks. You will find it easier to go over obstacles this way.
Driving Tip: Some rally races are held on dedicated off-road tracks with large jumps, tabletops and doubles or triples. If this is the case, you should raise the ride height and practice hitting the jumps properly so you don't go upside-down too often. Approach the jump head-on if possible and coast into it. As the front wheels hit the jump, go full throttle until the front wheels clear the crest of the jump. If done properly, you should land on all four wheels. You may have to add a larger wing or spoiler to the rear of the car to help keep the nose up while the car is in the air. (7/7/98)
On-Road Chassis and Suspension Setup
Many HPI customers have more than one kit, and have upgraded certain parts of the kits they have. If you have a spare shock set from an RS4 Mini or RS4 Nitro after you have upgraded to Super Shocks for that car, you can use that extra shock set to have a dedicated set for on-road rally car use! Real WRC cars have many sets of tires ready for pit stops and use the proper tire for the conditions they will face. The pit crews can also change the shocks in as little as 20 minutes, and you can do the same thing when preparing to run on a paved track.
For a track with a bunch of traction, such as a track that has been swept or blown off and then sprayed with soda or sugar water, use a firm suspension. Bill likes the #4 piston, a thick (40 wt) silicone shock oil and stiff springs, such as gold or white.
For a slippery or loose track, you will need a soft suspension setup for more chassis roll. Bill uses a #1 or #2 piston with 20 wt or 30 wt silicone shock oil, and copper (softest) or silver (one step harder) springs.
Bill likes his chassis to run very low to the ground - about 3 to 4mm! To set up your car this low, mount the top of the rear shocks on the upper hole of the shock tower, the hub carriers in the lower holes, remove the unflanged rings from the shock bodies and use the shock clips to adjust the ride height.
Tire Selection and Chassis Width
The stock tires that come with the RS4 Rally are great for most off-road bashing. Grass, loose dirt and sand are all good places for the kit tires. Don't run these tires on asphalt for very long! You'll notice the knobs wear off very quickly when they are run on a surface they are not meant for. For hard-packed dirt or clay tracks, the softer rally tires (soon to come from HPI) will work much better. Testing by HPI factory drivers has revealed that for the typical clay/blue groove dirt track, the soft compound Rally tires that will be available soon are the best tires to use.
The spacers that come with a pair of HPI wheels are 2mm wide. They will basically widen your car by 4mm. The RS4 Rally with standard-offset 26mm tires is about 196mm wide at the outside of the wheels. With the spacers the car is about 200mm, which will make it a little more stable in cornering. You can glue them in the wheels, but we recommend that you glue them to the hub adapters if you use them so you don't lose them or have to re-install them each time you change your wheels. Some drivers like to have the spacers only in the rear to get more steering, some like them all around. Experiment, and see what feels best to you.
Using the wheels with 3mm of offset gives you an extra 6mm of width to use for better cornering and stability. With the 3mm offset wheels and the 2mm spacers, your RS4 Rally will be a little wider than 200mm.
Since the introduction of the belted tires, many sedan drivers have been impressed with the tire squeal when the car is cornering. While it sounds like a real car, the squeal means you are losing traction. Using the new molded tire inserts, available from a couple of companies, will almost eliminate the squeal. See the tip below.
The recent surge in popularity of the molded foam inserts is making tire choice a little bit more confusing. The companies offering molded foam inserts have them available in two different compounds: soft and hard. The soft inserts are stiffer than our included foam donuts or strips, and the hard insert is even stiffer. Using these on some high-bite tracks will improve traction, but you may have to soften your suspension.
For more on-road tire tips, check out the tire tips page.
Radio Equipment and Electronics
Use the stock external antenna mast, not a 'stealth' antenna that is hidden underneath the body. A little wind resistance is better than risking radio interference that could cause a huge crash. Also, if another racer is running on a frequency that is close to yours, your car may glitch and get twitchy at the opposite end of the track. The extra range may mean the difference between you hitting a wall and getting around that hairpin!
Many racers like to use a high-speed high-torque steering servo to handle the front wheels. His favorite is the Hitec 525BB, a servo that has 55 oz. of torque with a .10 sec. rotation speed. Fast and strong servos do cost some money, so they are only recommended for serious racers.
Mount the motor as low in the chassis as possible to gain the advantage of a lower center of gravity. You can vary the height of the motor mounting by choosing spur gears and pinion gears of varying sizes.
Maintenance
Use a very lightweight bearing oil on the bearings. Make sure that there is no grit in them. If there is, use motor spray to blast the dirt out, then reapply bearing oil. The bearings that are sealed in the kits won't have to be cleaned, so you won't have to worry about those!
Bill and Frank are big believers in using MIP Blue Seals and RCPS Green Slime when building or rebuilding shocks. The Green Slime goes on the o-rings and lengthens the time between rebuilds, but by no means does this mean you can ignore your shocks! Rebuild them when you notice a leak, or about every three to five race days.
Other Tips
Many racers like the large front bumper that is included in all HPI 1/10 touring car kits. Most of us here at HPI use our optional Foam Bumper (# 6231) to make our bodies last a bit longer. Foam bumpers also support the nose of the body, so the front spoiler doesn't hit the ground as the wind goes over the car.
Many racers have never bent a stock tie rod in several months of racing. Options like a good selection of tires and an extra body and/or wing set are a higher priority than titanium tie rods.
Speed Tip from Kent Clausen: Your ball cups should be kept fairly loose when on the ball ends. They should be able to flop around easily but still stay on. One way to do this is to put the ball cup on the ball end, then pinch the sides of the ball cup with a pair of needle nose pliers. Then, push down on the top of the ball cup by using pliers (slip joint pliers work great) and pressing down on the top of the ball cup and the threaded end of the ball end.