on my 2013xkr ragtop that has 35 mm drop from H&R springs,and 15mm spacers, I get rear end hopping especially driving fast and making sudden lane changes or turns.

No, I didnt put the springs on upside down.

I am disappointed that the car is doing this

Anybody else have this problem and i would appreciate anyone being able to tell me how to fix the problem. Thanks in advance

 

hops??? not had any hoping in spirited driving nor at the R Academy hitting the gas like crazy... anyone else??

 

maybe I should call it wheel hopping. Thanks for replying so soon. I appreciate that

 

Today I did hit the gas rather abruptly from stop on a straight away and felt 2 hard shimmies... I wonder how this differs from your hop? I figured the torque was just too much for the road and chuckled!!! Maybe I should be worried about my shimmies?

Loth

 

It probably has to do with the suspension. In my beater 2000 Ford Mustang V6 (only 190 horsepower or so?), you can get horrible wheel hop (as opposed to a smooth and glorious burnout) and it's not because it has a lot of power!

 

Did you have the same issue before you did the spring mods or did it just start. If it is a new problem then have you check to make sure everything is still tight and the suspension mounts are OK. How was the road and have you done the same move on a smooth surface.

 

I used to get terrible (front) wheel hop in my FWD 180 hp Hyundai Tiburon on hard acceleration. I don't know if that's any help but it seems in line with what you said.

 

The solution is a hop-not kit.


Rich

 

Never had any wheel hopping on my previous sports cars- m3, 911 turbo, or Xkr-s. I have only seen this on cars with aftermarket springs or coilovers. Did you have this problem when it was stock? Not to stay that modding the suspension is bad, because I have seen many well sorted cars on the track that have mods to their suspension

 

I going out on a limb here and say the new springs/shocks are not the right one's and there not applying the same down force as OEM. There's a lot more to springs than just the height.

Wheel hop making sudden lane changes with the back end???? maybe what your feeling is not wheel hop. What about spring hop?

You didn't put the spring in the wrong way but you bought the wrong spring. I'm sure you read the technical section of H&R web site,

Better yet, mount a GoPro underneath and watch the suspension work.

https://www.google.com/url?q=http://...LJw56JiZZyrZAg

https://www.google.com/url?q=http://...JOquFKfCUtnRaA

 

You have reduced the spring travel quite a bit with a 35mm drop. Do those kits also replace the dampers? With that drastic a reduced spring travel are you forcing the tire to absorb too much of the reaction?

Given that others have used the 35MM springs from Mina and have not experienced the issue maybe it is the springs from H&R?

I looked at new springs for a lower height when I had the 2010 XKR, but after researching the change in geometry of the wheels, the spring travel, and dampening I decided to go with the XKR-S springs. I was gonna do that but...

After looking at the height of the XKR-S and driving it, I can't imagine going much lower with these cars.

 

I get the shimmie (sidestep) accelerating and turning sometimes. I've looked at the rear suspension and noticed the tiny tie rod boots are blown.

My guess is this causes the sidestep, check yours, they maybe the same.

 

Don't screw with the suspension!

 

Its the dampers and why I went to coil overs. The stock dampers are at the end of there travel with the car lowered and IMHO even stock are inadequate in rebound damping on cars that do not have the dynamic pack. The bouncing at high speeds drove me nuts and made the car very nervous at 80+ on anything but a smooth road.

 

Hmmmm...Lets pretend I dont know anything about the actual underpinning's of a car (hence I dont mod- which I would if I understood anything).

What is Tiny Tie Rod Boots???

 

I'm at a 30mm drop with coil overs but the dampers were re-valved and bump stops relocated as well. If your lowering this car change the dampers, even if your using XKR-S springs get the dampers to match, as the spring are ~26% stiffer and the stock XKR dampers will not handle the rebound of the stiffer springs. Hence you get the "bob" on the rebound over bumps.

Once the stiffer spring compresses for a bump the dampers can't slow the movement (fast bump damping) so it compresses the spring more then it should then spring releases sending all that energy in rebound and the dampers can't control the fast rebound damping.. This is the trade off Jag put in the non Dynamic mode/XKR-S/GT cars for a smooth everyday ride. The slow bump/rebound (read braking turning etc) seems to be ok, its the fast damping that causing that bob.

With just H&R springs I was always in Dynamic mode and the dampers were just over matched by the springs, and I wouldn't track the car as it was scary at triple digit speeds over rough roads. I have no experience with the Mina springs and have no idea of their spring rates but I will say again that make sure your dampers match your springs so they can control the bump, rebound and travel. I've tired every route on this car when it comes to this.

So in short change the dampers if you change your springs.

Also suspension geometry changes with the car lowered. We looked at this at this as well when corner balancing and the XKR suspension has a lot of travel even at a 35mm drop but needs to be supported and aligned correctly for the amount of travel you have at slow and fast bumps. The lower the car, stiffer the springs and the less travel you have, but make sure the dampers can handle the springs.

Its taken me 4 months to get close to being 95% satisfied. I still want more rear bar or at least adjustable depending on the track. I'm actually going to also go to a bit of toe out on the front for very low speed turn in.

Albert ax6r wrote up a great post on this and he has way more setup and racing experience then myself. https://www.jaguarforums.com/forum/x...n-long-114413/

 

Just to add to that my dampers are modified F-Type dampers as they provide quicker fast bump response time compared to the XKR dampers and work the Dynamic stability control system in the car. This may be an option with H&R springs but I'm not sure of their spring rates.

 

Having driven a little in SoCal I would not contemplate lowering a car there. Many of the surface streets look like Lower Beirut complete with bomb craters. Then there is I-10 to the East of LA. That's just a large potato peeling taken from the Moon, stretched out, then given a center divider and ramps. Even frost heaved I-40 in Northern Arizona is not as gruesome.

It sounds to me like the combo of a 35mm drop with spacers has dorked up the geometry enough that the suspension may be binding up in extreme maneuvers. That will give you some odd effects. I would also suggest looking for signs of tire contact with the inner fender.

Another thing, I'm not convinced that ANY convertible can cope with extreme suspensions as well as a coupe. Could your "hopping" actually be chassis flex? I experienced flex in a Firebird with T-tops and it was a bizarre sensation to say the least.

 

I never thought about the flex in a convertible. that is a great insight to the possible problem.

the tie rod boots arent blown. I looked, and the car has less than 2000 miles. I only get to drive it once and a while and when I do I probably drive it too hard. Thanks for your insight

I compare it to my fiance's 911 4s cabrio and the handling is so much different and more "mannered" . This is why I couldnt understand the hop

 

The tie rod runs horizontally from the Differential to the wheel, in the middle of the rod you'll see a nut and it is screw shaped to make toe adjustments. On the wheel side it has a bushing and on the side towards the diff it has a small grease packed dust boot kinda like a axle half shaft does.