Rolling Resistance

Jacer Race CarsHave you ever put 30lbs in your Vee tyres and noticed how easy it has suddenly become to push? In short, it’s rolling resistance. The contact patch of the tyre to the ground has shrunk in relation to your normal pressures, giving you less resistance or effort required to move the vehicle.

It may be impractical to use 30lb pressure in your tyres in a racing situation as that lack of contact patch to the track becomes a disadvantage, but other parts of the car can give you a similar resultant gain. The most basic of resistance in our cars come through the brakes. Be it either drums or discs, the result is the same.

If when you jack your drum brake car up you can?t rotate the wheel and have it spin easily for at least 7 to 10 seconds (front wheel here) there is a resistance that the engine must overcome. Wheel bearing and brake adjustment will be your main area of gain there. Disc brake cars are slightly different though. Yes, wheel bearing pre loads are something that are important, but brake adjustment is non-existent, so is there anything that can be done to help?

Yes, of course! By nature of the system, the pedal doesn’t move that far, meaning that the caliper and master cylinder also don’t move that far, and unlike a drum brake set up, discs don’t generally have a proper return spring to retract the pads away from the discs. In time they can stick slightly, meaning the release of the pad from the caliper becomes a lot slower.

Something simple that you can do yourself is to remove the wheels and push the pads back slightly and then pump the pedal until the pads are pushed back out again against the discs. Do this a few times on all wheels and you should find the pad „releasing? a lot faster. If you have the VW callipers and the anti rattle springs have been removed, put them back in. They act as a form of return spring also. It goes without saying that the gearbox consumes its fair share of h.p. through its resistance.

Internal pre loads and viscosity of lubricants play their part. The same can be said for the engine with piston ring drag or valve train friction, but if you don’t have the budget to chase drive train frictional losses, there are gains to be had in the most basic of areas with just a little bit of time and effort.

Wheel Alignment

Formula Vee Wheel AlignmentHi, this time I’ll cover a basic Formula Vee wheel alignment. This will use the string method which is the only practical method you can use at a race track.

Firstly you need to get something that you can tie string to that has a height roughly at the axle height of the car. Two bars with pins the same distance apart set up on car stands will do. The idea here is to set two parallel strings either side of the car and have the car set up with its centerline parallel to the strings. When you measure from the string to the car you won’t have the same measurement front to rear, but side to side will be – the measurement from the front axle to the string may be 100mm but the rear may be 90mm.

Providing that the string in front of and behind the car is the same distance apart, and both sides at the front axle are the same and both sides at the rear axle are the same, then the car should be parallel inside the „box”. Depending on the type of rear suspension you have, you?ll need fairly flat ground, but not spirit level flat. For a twin coil over or rear torsion car, you will, but that’s not going to be covered here. Once you’ve got your car straight inside its “box”, you?ll need to set the steering wheel straight ahead and come up with a method to hold it there.

It must be noted that if you are going to adjust camber/caster, you have to do this first. Any time you change camber/ caster (the eccentric not under the top ball joint will do both) on a ball joint front end, toe will change. Measure out from the string to the front of the tyre, and then from the rear of the front tyre to the string. If those measurements are 95 mm at the front and 100 mm at the rear on the left hand side, for example, then that side has 5 mm toe out.

Repeat the same for the remaining three corners and adjust according to the settings required. Noted again that I will measure off the tyre, NOT the rim. The rim?s straightness will depend on how many curbs it has hit, and some of the rims I see look like the car has been dropped off a building (sorry guys!). Small deviations in the rim will affect your alignment. However, the tyre will tend to even itself out better than the rim. This is just a basic reference as to the method of checking toe in/toe out. What you set things to will depend on the manufacturers settings.

Grab the spanners and have a go.