HPI Racing - RS4 Sport 2 Tech and Racing Tips

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 tips that we have gathered over time plus pull together the tips we get from our email bag.

The Tech and Racing Tips pages for all the cars will be updated as frequently as needed to keep pace with the new race hints and ideas we come up with. This page will have the newest tips listed first, with the date noted next to it, so that you will know how recent the update is.

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.

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!

HPI Factory Team Drivers have found great success using dual one-way bearings (a one-way diff in the front, plus the one-way pulley on the gear shaft) and our #73008 Pro 2 Handling Kit. The one-way bearings allow a higher top end speed but WILL require much practice to get used to. If you set your ESC brakes high enough the car will spin out if you brake. Most HPI Team Drivers using this setup do NOT use brakes (that's right!) and with some practice you will see your cornering speed pick up dramatically.

For racers who use foam tires, we have a great setup tip from Matt Lee, who is a consistent top finisher in high-level Australian races. After careful experimentation, Matt settled on a shock length of 65mm (instead of the 63.5mm from the instruction manual) when using foam tires trued to a diameter of 62mm. This gives a ride height of 5 to 6mm, and Matt uses the tweak screws to lower the car further. Keep in mind that as the foams wear the ride height will need to be raised, so check the ground clearance after each race! Thanks for the tip, Matt!

Expert and experienced drivers who race at tracks that use transponders can benefit from using a practice transponder. Depending on where you place the transponder, it will affect the steering and handling of your car. Experienced drivers can feel the effect of an extra ounce of weight (about the weight of a transponder), so using a practice transponder can get you used to running with the extra weight on the car.
41 KB	These are the materials you will need to make a practice transponder: servo tape, hobby weights and a paper clip or something else you can make a loop out of. You can also use coins and servo tape them together. It may actually be cheaper!
32 KB	Attach servo tape to the hobby weights and put the paper clip in between them.
11 KB	This is the finished practice transponder. It weighs about 30 grams, and a real transponder weighs about 25 grams. You may want to cut off part of one block of weight to get a more exact weight.
50 KB	This is how most of the HPI factory racers attach the transponders to their car. You can also use a c-shaped piece of Lexan and screw it to the middle hole in the bumper, or mount it off the servo, although that may throw off your car's balance. Mounting it on the chassis also looks better than drilling a hole in the body, and it contributes to a lower center of gravity!

Two 4 x 8 x 3mm ball bearings or bushings will fit perfectly in the right-side steering arm. This will take up a lot of steering slop and make the steering a little smoother and quicker. To replace the plastic bushings, use #B067, $1.50 (six 4 x 8 x 3mm bushings) or #B017, $14.00 (two 4 x 8 x 3mm bearings).

The camber link locations provide some tuning ability for experienced drivers (intermediate and above). The stock locations work great for almost everyone, but experimenting with the car can bring some people added benefit. If you move the inside link of the front upper tierod to the lower position, the front tire will get more negative camber when compressed. The farther IN and UP you move the outer link of the rear upper tierod, the more camber the rear wheel will get when compressed. This can give you more traction in turns as the suspension compresses.

If you run your car very low to the ground you may want to remove the nerf wings because they limit how far the chassis can lean, and they can catch on the racing surface in a turn.

Your car chassis should be level or slightly nose-down when seen from the side with the body off and at running weight (all electronics installed). To set up your car this low, you can: 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.

Many racers agree that the sway bar set is generally unnecessary, preferring to set up the car as close as possible using shocks and tires, then possibly using a sway bar in the rear just to fine-tune the car, maybe to get a little more steering.

If you would like to try the one-way pulleys or one-way diff, here's a tip: 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 very loose, just enough to catch the gear teeth while not slipping.

We recommend using saddle pack batteries for two main reasons: a lower CG (center of gravity), because the cells sit lower than stick packs, and quicker steering reaction because the cells are closer to the front of the car than with stick packs.

To have your steering slop-free: try setting servo saver screwed very tight, about 4 to 6mm 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. Suggested for experts only!

To make knowing your shock setup easy, install the shock pistons with the numbers face-up. This way, if you take off the shock cap you can read the piston number through the oil.

Use a Sharpie permanent marker to write the piston and shock oil weight on the caps of your shocks.

To remove the shock of the ball ends, lift up the spring perch and use needle nose pliers to twist off the end of the shock, then use your hand to twist off the top. This prevents scratching the ball end, which could make your shocks act erratically.

Have some spare ball ends handy in case you scratch one of the ball ends on your car. The shock action will not be the same because the scratch will cause extra friction and make the shock act slower.

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. try the #3 or #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.

The HPI factory drivers are big believers in using 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. Use new o-rings whenever you rebuild the shocks.

The colored springs, such as white, yellow, red, black, green, blue and purple, are HPI's stiffest springs, going from softest to hardest. These are used on tracks with very high traction.

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.

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 in the front and 0mm offset wheels with 2mm spacer in the rear, your narrow RS4 Pro will be at the limit of most rules (190mm). (3/12/98)

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 now from HPI (see the Inner Foams page!), will almost eliminate the squeal. See the tip below. (1/27/98)

The recent surge in popularity of the molded foam inserts is making tire choice a little bit more confusing. Using these on some high-bite tracks will improve traction, but you may have to soften your suspension. As always, experiment! (1/27/98)

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! (10/1/97)

Bill Martinez likes to use a high-speed high-torque steering servo to handle the front wheels of his Pro. His favorite is 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. Beginners will do fine with the cheap 35 oz./.22 sec servos that come with most radio sets. Intermediate drivers may want to get a faster servo, around a .15 sec rotation speed. (10/1/97)

Mount the motor as low in the chassis as possible to gain the advantage of a lower center of gravity. (10/1/97)

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. (10/1/97)

Try to split your car maintenance into two or three sessions, doing the front end one day, the rear end the next, the diffs the next, etc. This will keep you from getting 'burned out' on cleaning your car. (10/1/97)

The front and rear diffs should be checked (but not necessarily rebuilt) every time you race the car. If the action is gritty or dirty, it's time for a rebuild. Just follow the instructions in the manual again, and if the diff washers have a groove in them (they will have marks, but don't worry about that), replace the washers. Always use new diff balls when rebuilding diffs. Carbide diff balls will last longer than the stock diff balls. (10/1/97)

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 urethane bumper (# 6231, or #6264 or #6275 for precut foam bumpers) 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. (10/1/97)

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. (12/11/97)

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. (10/16/97)