Thursday, July 26, 2012
Car care: selecting and installing sports rims
[Article copyright Ewe Paik Leong]
Sports wheels complement high-performance tyres in terms of appearance and performance. Wheels can be made from a variety of materials such as cast steel, cast alloy, aluminium, hot die forged aluminium and cold die forged aluminium. They can be one- two- and three-piece makes as well as those that are chrome plated, clear coated, painted, brushed and polished.
When selecting new wheels, make sure they are of the proper size, dimension and load-carrying capacity. Two factors that determine wheel size are the size of your tyre and ride application. There is an approved rim width range for each tyre size. Using wheels that fall outside the range will put stress on the tyre resulting in poor performance. A wide rim increases steering response; on the other hand, a narrow rim gives a comfortable ride. To maintain a balance between ride comfort and precision handling, the average driver can go for wheels with mid-range rim widths. Also, remember not to use millimetric wheels on standard-inch, and vice-versa.
Backspacing is also an important factor to consider. Backspacing is the space between the inner plane across the rim to the surface of the centre disc at the lug bolt holes. It is advisable to stay with the original backspacing figure to avoid problems with vehicle suspension during cornering. To determine the backspace, position the wheel space down, lay a straight edge across the back of the wheel, and measure the distance from the straight edge to the wheel hub’s mounting surface.
A torque wrench should always be used to install sports wheels (or for that matter even an ordinary wheel) and proper tightening procedures must be followed. To install, first check that the nuts and lugs are of the proper size. Also, ensure the nuts are of the proper seat design for the wheels. An incorrect seat design may cause the wheel to sit incorrectly on the hub.
Once the wheel has been mounted on the hub, screw the nuts on with your hands until they fit snugly. When tightening the nuts, do so in a criss-cross pattern.
Give careful consideration to the clearance and the tyre diametre when upgrading to a bigger wheel and tyre size. Make sure the tyres and wheels do not extend beyond the fender, or interfere with any part located at the inner side. The outer diametre of the new tyres should be within plus or minus 3% that of the standard tyre.
Sports wheel needs frequent cleaning as brake dust often accumulates on them. Normal soap is too weak to wash off such dust which can cause the finish to deteriorate. For this purpose, get aftermarket wheel cleaners which usually have pH levels of 8.5 to 9.5, and clean the wheel using a soft brush. Do not spray water on wheels when they are hot as the sudden contraction can result in damage to the drum and rotors. Always wait until the wheels have cooled down.