2008 Miata with "Whump" sound in the morning

I have a 2008 Miata that is new to me (<40K miles). When I first drive it in the morning it has a very noticeable bumping feel for the first couple of minutes then smooths out and is not noticeable for the rest of the day, even if I park it for a couple of hours. I believe the bumping is coming from the rear driver’s side. I just replaced the tires (thinking they were flat spotted), but the problem persists. Open for suggestion.

assuming tire pressure and balance/alightment done right, you should check the wheel bearing and rear left suspension assembly to see if they are out off the spec. If the oil leakage comes out below that bump cap, replace the shock (both side same time). I believe your OEM shock is dued to replace. I recently replaced the struts and shock in 2009 MX5, but I could be wrong about yours. Please update what you find out.

Inner CV joint.
That’d be my wild guess. Check it out.

I know this is an older post but…

Almost certainly a bad shock. It is getting stuck after sitting all night but has enough gas that after moving around for a bit that it gets you through the rest of the day. A bad shock is almost perfectly described by a “bumping feel”. A bad front shock when you hit a bump will feel like the steering wheel is connected to one of those spring door stoppers and someone just flicked it. Just much scarier and bumpier.

A bad wheel bearing or CV joint will not get better after driving around. A bad wheel bearing will be especially noticeable when taking turns, sounds grindy.

Again, I am just posting this in hope of helping future viewers diagnose a problem.Please tfouts, if you found the solution, please repost and tell us what it was.