Man I am tired of this bouncing while riding. I have never put this much effort into fixing something that seems to be so simple. I know we have slightly discussed this in a different thread about road force balance. I decided it was time to just discuss the entire problem…
2004 Monte Carlo SS with FE4 suspension. 86Kmiles with factory struts. ATE rotors with ATE ceramic pads. Factory wheels and new Uniroyal Tiger Paw GTZ tires in the correct size per the door sticker (replaced previous tires due to wear and were a slightly smaller size previously). Road Force numbers from 14 to 25 lbs calculated by the GSP9700 Hunter balancer. New axles about 1K miles ago. New wheel bearings at 60K. No play in any suspension components noticed when at the tire shop… I cannot remember how long this has been doing this but I think it was very near when the tires went on in November last year. I cannot remember for certain. Driving impression, car is planted on the road other than this bounce. Handles well when pitched around corners.
Here is what I have noticed so far. Some days on the same stretch of asphalt it rides like glass and others it is like riding a buck board. Much worse when the fuel tank is almost empty as compared to a full tank. Tire rotation does nothing to improve. Tire pressure has been varied from 35 LBS down to 28 LBS cold tire pressure with almost no change. Door sticker says to run 30 PSI… Can be very severe at speeds as slow as 20 MPH and when it is doing it the problem is just there up to 70 but there is an improvement as it speeds up.
All rotors look the same no bluing from a dragging pad. All pads look like the same amount of material still left on the pads. The brake system has not been taken apart in 25Kmiles but inspected when the tire store threw on the tires almost 5K miles ago.
The output trans axle extension was taken out and checked. No discernible warp seen and the differential looked good with no funny wear patterns. This is when the axles were replaced and lower motor mounts were replaced. I rotated the upper radiator support mounts like the GP guys claim helps. No codes from the trans or the engine to boot.
The kicker in all this, a romp on the gas once it starts to bounce usually pulls it out while the car is under acceleration. It returns as soon as you release the throttle though.
I would really like to fix this. It is making the short drive to work very hard to handle.