HPI Racing - RS4 Pro 3 Bulding Tips

These are building tips that HPI team drivers have found will increase the effectiveness of your Pro 3 kit!

Spur Gear Mounting
Use the diagram below showing the "star pattern" to help you install the spur gear on the Pro 3. This will help make sure the spur gear does not wobble when the spur gear is installed. Since the spur gear hub is plastic, don't tighten too much or you could strip out the plastic hole.

Battery Foam Spacers
When installing the foam spacers for the battery pack, test-fit your battery to make sure you have enough space to install it. You may need to cut down the foam spacer depending on the type of battery (stick pack or side-by-side) you are using.

Servo Wire Clearance
If you will be using side-by-side battery packs, make sure that the servo wire is clear of the battery bar when the battery pack is installed. You may need to use extra servo tape to hold the servo wire clear of the battery bar, or use a product like silicone sealant or Shoe Goo to protect the wire from fraying.

Belt Tension Check!
After the first few runs using brand new belts, check the tension of each belt. You may have to tighten the belt as it breaks in and loosens. Do not make the tension too tight or you could lose some efficiency.

Wheel Air Holes
Use a small drill bit or hobby knife to put two small air holes in each wheel, opposite each other. This lets air inside the tires in case the tire is glued all the way around the tire making it almost airtight. If a tire that is almost airtight is compressed, the tire may not fill back up with air and expand, giving you a temporary flat spot on the tire. A couple of 2mm or 1/16" holes will prevent that problem.

Never Have a Tire Come Unglued!
Use denatured alcohol or our Nitro Car Cleaner to clean the wheels and tires where the CA glue will be applied. Before each race, check the outside edges of each tire for loose tire beads. Doing this will ensure a good bond so that your tires do not come off in a race.

Use the Right CA Glue
HPI racers have found that Pacer Zap CA (CyanoAcrylate, or Contact Adhesive) works best to bond the rubber of the tire and the nylon of the wheel. Use the super thin version, which runs between the tire and rim. It may run too well, so don't use too much, and have some debonder (solvent) available in case it gets on your fingers.