Not noticed this before but when I stand behind my XKR (2008 MY 4.2 s/c coupe) there is a slight 'sag' or 'dip' on the right hand rear side. I confirmed it by measuring the gap between the top of the tyre and the wheel arch and there is a noticeable difference. The 'sag' isn't huge but it is definitely there.

Does anyone have an ideas as to what might cause this? I'd welcome some suggestions before I book it into my local Indie for them to have a look at it. The car is due for service in March and I don't want to take it in beforehand, unless it is something which needs urgent attention (potentially dangerous or damaging to the car). Many thanks.

 

Possible causes include:

1. Incorrect tire pressure.
2. Bad spring, shock absorber, or bent suspension component.
3. Suspension bushing rotted, cracked or missing.
4. Improperly repaired chassis damage.

An inspection by a body shop that is qualified to do Jaguar aluminum body repairs should be able to identify any paint, body, or chassis repairs and pinpoint the cause.

 

Thanks Stuart. I can rule out 1) and 4). Rear bushes may be due for a change so that could be the cause. I hit a bad pothole recently so that may cause 2), although I would expect the front end to take the impact in that case.

Happy New Near to you BTW, and thank you for all the help in 2020.

 

Uh, another thing that causes driver-side sag is a .... well........ a large driver. With an additional 100 kg predominantly on one side, that's a bit of extra weight. More than 100 kg and, well, things do wear out, springs included.
Since I have no idea the sizes of any drivers, my statement is merely a generalization of possible causes.

 

HNY to you Cee Jay.

Not guilty. I am just over 70 kilos... that's 154 pounds to you guys, 11 stones to the Limeys present.

 

 

The difference between Limey English and Yank English is amusing, if not hysterical. A Yank with 11 stones would be in the Guiness Book of World Records and wouldn't be able to walk!

 

If you're talking WOOL stones, I'd be surprised you'd fit in your XK

 

1 stone = 14 lbs.
https://en.m.wikipedia.org/wiki/Stone_(unit)

 

Barnsie, could it be that the previous owner of your car was a FB?

I'd bet on springs or shocks, springs get compressed and sag over time.
.

 

We sag over time, too!

 

I always replace springs and shocks in pairs, but some will try to keep the costs down (to get through MOT or resell etc) and only change one side.

Could be the case with yours and the sagging side has the original.

 

Nope. He worked on the oil rigs off Aberdeen and was as lean and fit as a butcher's dog. Dunno about his wife though

Yeah that is my bet too, following the advice here. I'll get it seen to when it goes for its service in March.

 

I had a problem like that once. Due to an small accident, rear sub-frame shifted a bit and that impacted the rear geometry and alignment. I was able to detect it myself when I put rear on ramps and got under the car. Look at the bolts (4) that attach rear sub-frame to the body. The way they go through sub-frame mounts should look the same on both sides. In my case, the fix was pretty simple. Loosen the bolts, push the sub-frame a bit to realign and then re-tighten the bolts.

It's also possible that your rear is out of alignment due to a pothole. That would impact the ride height, I've experienced that as well. Take it to shop, ask them to inspect the sub-frame (or do it yourself) and check the alignment.

BTW, check the ride height off the ground, not the gap.

 

Thanks. An alignment check was on the cards anyway when it goes in for service because of the huge pothole I ran over not so long ago. I'll also get them to check the subframe while they're at it.

 

DO NOT measure from the ground, but from the wheel center to the top of the wheel arch:



With a metal straight edge, magnetic level, and measuring tape, you can get a pretty accurate measurement.

Note that in the manual, the only listed cause of 'riding low' or 'bottoming out' is the coil springs. If your ride height is out of spec it must be the springs - unless your fenders and/or frame are significantly damaged.

 

That's correct, but perhaps not what the OP is looking for. Far be it from me to challenge an aerospace engineer, but I thought Barnsie intended to compare the left and right rear suspension heights, not determine whether the car was within the absolute ride height specs. If the rear tires are inflated to the same pressure, he can see the difference whether he measures from wheel center or the ground.

My .

 

+/-15mm Impressive

 

Haha don't challenge me, challenge the chaps who wrote the manual! All I vouch for is accurate and reliable data =]. You can compare right to left but measuring is the only thing that will tell you if both or just 1 needs to be replaced.

Different tire brands, materials, pressure, and weight distribution, etc... all affect the height if measured form the floor. The correct measuring method IS NOT dependent on tires or tire pressure.

So if you measure the ride height per the manual, then deflate any (or all) of the tires and measure again, you'll get the same numbers! Engineering at its finest.

 

Thanks. The car has never been in any sort of accident and never repaired, so I am guessing it's the spring on that side. What I don't quite understand is why one would settle more than its counterpart on the other side of the car.