What is wheel hop?

This is generally wheel hop, also known as a convenient automatic windsheild wiper activation feature. Both AWD and FWD DSMs apparantly suffer from this, in proportion to other mods; FWDs tend towards front wheel hop, AWDs prefer rear hop.

Not really caused by wheels bouncing, wheel hop occurs when the tires are getting/loosing grip in rapid sucession. Wheel hop tends to stress transmissions, differentials and other driveline components quite badly. It has also been posted that the majority of center differential failures are directly related to wheel hop. Slicks, stiff suspensions, hard launches and burnouts promote wheel hop, and the resulting driveline failures.

Mark's solution (provided by Road Race Engineering) involves filling the stock engine mounts with polyurethane rubber to make them stronger.

Other FWD solutions include: equal tire pressures (left to right), lower tire pressures, softer suspension, a front sway bar (not strut tower brace) and less drastic launch techniques. AWD solutions include: equal tire pressures, softer suspension, and less drastic launch techniques.

Scott Willard describes his experience with a loose driveshaft striking the bottom of his car. This is not the same as wheel hop but has the same symptoms - he describes a test to differentiate between the two conditions. AWD cars which exhibit a thumping from the rear are likely to have this problem, which is caused by worn carrier bearings. The solution to this problem is listed on the VFAQ Locator; the $5.00 Carrier Bearing Fix page has the details.