left rear sag
 

On the RX-8, the fuel tank sits just in front of the rear axle on the driver's side (on the US model anyway).

I noticed on my car that the gap between the wheel and fender is a little bit smaller on the left rear wheel. The effect is small. Maybe 1/4-1/2 inch or so.

Is it possible that this is caused by the extra weight of the tank and fuel? The extra weight might be ever so slightly compressing the suspension components?

I would think it's possible. A good way to check would be to measure the gap while the tank is empty,then again when the tank is full.

Wow, what a good eye to notice such a small gap! I don't think I've ever really paid much attention there...

The tank is a saddle type and is on both sides so it should not effect one side more than the other.

after 4 months since my tanube spring install I tweaked my rear driver side spring with a sreader kit due to driver side sag....adusted and leveled with 1/2 in spreader adjustment. I found it was needed because of being the only car occupant over time :D

I have Eibach springs. I measured mine using fender gap and floor to bottom-of-bumper gap. The front driver side is lower by about 1/5 inch in both measurement. I did not check the back though. I think it's pretty much standard that the drivers side is lower than the other side. I heard previous complaints about it. I don't think the gas tank has anythin to do with it due to its design.

considering that most roads are crowned in the middle it might make sense to have the drivers side lowered slightly more than the passenger's side.

i thought the fuel tank was centered... :confused:

actually i'd figure to have the passenger side lower because when the driver is in the vehicle, it would balance out.

i thoguth cars were developed with the driver side a bit harder and a bit higher than the passenger side because or the driver being presence in the vheical more often than the passenger?

yeah that :)

Well by that logic, a Japanese build car imported into america might have the drivers side lower if they use the same suspension specs as they do on JDM cars - the japanese drive on the left dont they?

but then if they change the car from right hand drive to left hand drive, y not bother changeing the suspensions from right to left?