Suspension - Drifting and Pulling At Highway Speeds

SOURCE:
Honda Service News September 2003

TITLE:
Drifting and Pulling at Highway Speeds

APPLIES TO:
All Models

SERVICE TIP:
Got a customer complaining that the vehicle drifts or pulls when driving at highway speeds? Use this handy procedure to diagnose and repair the problem.

NOTE: Before doing the procedure in this article, check ISIS for related S/Bs and other S/N articles for the model you're working on.

1. Check if your customer has original equipment wheels and tires and that the ride height hasn't been modified.

- If the wheels, tires, and ride height are OK, go to step 2.

- If the wheels or tires aren't original equipment or the ride height was modified, stop here. Aftermarket wheels or tires or a ride height that's been modified pose challenges that this article doesn't cover. Resolve these issues with your customer before going further.

2. Set the tire pressures to the recommended cold inflation values listed on the doorjamb sticker.

3. Find a straight stretch of 4-lane road where you can safely (and legally) go 60 mph for several minutes. Ideally, you want a road that's perfectly flat, but most roads have a crown that��s anywhere from 1.5� to 1.75� so they can drain.

Flat Road - While driving at 60 mph, use a stopwatch to time how long it takes to drift one full lane from center to center. Record the time. Repeat this, driving in the opposite direction to cancel the effects of wind, then average the two times you recorded. If the vehicle drifts one full lane from center to center in less than 6 seconds, go to step 4. If not, return the vehicle to your customer.

Crowned Road - While driving at 60 mph, check if the vehicle climbs the crown. Do this for both a left- and right-crowned road. A drift to the right on a right-crowned road and a drift to the left on left-crowned road are considered normal. If the vehicle climbs the crown or it drifts to the right on a left crowned road, go to step 4.

4. Record the original toe, camber, and caster readings. On Passports, set the ride height to spec if needed. Refer to Ride Height Adjustment in S/B 99-043, Steering Wheel Shimmy or Chassis Vibration.

5. Loosen the subframe mounting bolts, and move the rear beam (it��s the entire front subframe on some models) to get the maximum amount of caster and equal side-to-side camber. (As little as 0.4� of camber stagger can cause the vehicle to pull.)

6. Make sure the steering wheel is centered, then set the front and rear toe to the maximum toe-in spec. (Toe-in improves vehicle stability and reduces the tendency to drift or pull.)

7. Test-drive the vehicle on the same road you used earlier.

- If the drift is now within spec, return the vehicle to your customer.
- If the drift is still out of spec, go to step 8.

8. Swap the front and rear tires on each side of the vehicle, then adjust the tire pressures to the recommended cold inflation values listed on the doorjamb sticker.

9. Test-drive the vehicle on the same road you used earlier.

- If the drift is now within spec, swap each rear tire back to the front, one at a time, and test-drive the vehicle on the same road you used earlier. Replace the bad tire, then return the vehicle to your customer.

- If the drift is still out of spec after swapping the front and rear tires, go to step 10.

10. Test-drive a known-good donor vehicle on the same road you used earlier, and check its pull.

11. Swap all four tires from the donor vehicle with the tires on your customer��s vehicle.

12. Test-drive your customer��s vehicle on the same road you used earlier.

- If the drift is now within spec, swap the tires back to the donor vehicle one at a time, and test-drive your customer��s vehicle on the same road you used earlier. Do this until the drift comes back. Replace the bad tire(s), then return the vehicle to your customer.

- If the drift is still out of spec using the donor vehicle tires, contact Tech Line for further action.