Hey gang, I'm about to order some springs to get the XKR down from 4x4 territory and am having hard time making a selection. Then I've also heard some can disable CATS so want to confirm this isn't the case (I have an 11' if that matters).

Ghostrider is on Paramount and says the ride is stiffer but not bad...

Pacio is on H&R and likes them...

Which set lowers the most? Which has the harder ride? I'm concerned that the springs would completely change the character of the car. I don't want it to ride like a buckboard but I do want tighter handling an better look.

Is there a general consensus here or has anyone felt more than one set and could provide some feedback? Also are they all about the same price?

 

I have not decided to lower my XK since one poster said that he could not bring the alignment into proper specs after the lowering. He used MinaGallery springs and he thought that they went lower than he would have liked them as after adjusting the front cambers the tires appeared to come very close to the sheet metal, probably requiring the rolling of the wheel arch lips. Remember that alignment is more and more important with these ultra low profile tires where the wide flat tire surfaces must sit square on the pavement for proper handling. The rear wheels have no camber adjustments, which make correct alignment of a lowered suspension unlikely. I just can not fathom why factories stopped providing alignment adjustments on their cars? On many newer cars, even the front cambers are non-adjustable. Guess, they are saving a few dollars, which must be really significant on a $100K auto, like the XK/R...???

An other issue is; The only way I would put lowering springs on my car if I were able to find out the specs on the springs. There is a wild world out there, people making and selling springs that are 100 percent stiffer than factory. My general principle for street performance cars was always to install stiff anti-sway bars/bushings, tight rebound rated dampers and the softest springs that I could get away with without bottoming the suspension. That usually worked out to be about 10-15 percent stiffer than factory springs. Much more than that will shake your teeth out and likely ruin your factory dampers as well as your handling on anything but the smoothest road surfaces. So, check with the manufacturers on the rates and if they tell you that they don't have that information, move on to an other make.

Albert

 

As particular as it seems Ghostrider is about his cars I'm sure he was able to properly align it. Ghostrider, care to weigh in here? Also on the spring options and pro's and con's...

 

Here is that write up/post on lowering springs that I was talking about;

https://www.jaguarforums.com/forum/x...red-xkr-69224/

Albert

 

Yep and Moe's comment at the bottom of that same post is the same thing he told me. That he has no uneven wear and the ride isn't too harsh. Certainly doesn't change the character of the car. It is still a GT - just a bit more focused and alert.

Would like to hear feedback from other owners that have lowered...

 

Same here; if I am convinced that the alignment is NOT an issue and the dampers do not bottom out with the lower spings I"ll likely lower mine too. I like the looks and could use a lower center of gravity.

Next few days when I get home I will look at the rear suspension geometry and see how a lowered ride will effect camber. On a well designed suspension the camber remains nearly constant even as the springs are compressed or lowered. With most strout type suspensions that is NOT the case. I will also check with my old race car sponsor who owns a racing/high performance auto shop and ask him about the max camber for a tire this wide (275) and this low profile. Like I posted, I already have over 1 degree negative in my rear wheels, which if I remember correctly, is more than enough for such tires.

Albert

 

Albert,

Well if lowering increases camber a little more it'll corner like it's on rails. And combined with stiffer bars you should be able to pull the cornering g's to lift an inside wheel just going out for milk! But I thought you liked the cushy ride now...lowering will take some of that away.

 

Bruce

Everything you say is true and I am really fighting over this decision. Every performance car I had ever owned before I altered. Lowered with springs, put different sway bars, dampers, bushings etc. Handling was always radically improved but, I am also very much aware of the trade offs: ride quality, having to worry about bottoming out, curbs, steeper drive ways, going over speed bumps, etc.

The big gaps between the wheels and the wheel arches do bug me, just like, apparently, most people here. I would put a bigger rear bar on this car in a heartbeat, if one was available. On my '05 XK I used a second factory rear bar in PARALLEL but, that is NOT a solution for this model. That is probably the biggest handling problem with the "08 XK.

So, my infrequent drives to contract work these day are 300 miles roundtrip, of which about 260 is freeway and a little bit of city while the rest, 40 miles, is winding, hilly roads near my home. Cushy ride is nice on the 260, the lack of handling is not so nice on the 40. So, decisions.... decisions...:-)

Albert

 

So, here is the scoop from my old race sponsor, Roger Krauss Racing. They are super qualified, having been in the racing/tire/high performance business for over 3 decades. I talked to the owner who specializes in alignments.

Before I could have told him my previous camber test results he told me that the '07XK variants have too much negative camber in the rears from the factory and, they are not adjustable and not correctable by spacers. That clearly confirmed my own measurement of 1.3 degree negative camber in the rears.

Once I told him that I was considering lowering springs, he asked me how much lower they would take me. I said; 1.2". He stated that would change the camber to 1.8 - 1.9 negative, way...way too much.

His advice, if I decided to go and still do it, was to do what some Porsche owners do with similarly no adjustment. Run a symmetrical tire, such as the Hancock Evo V12 and change its direction on the rims ever few thousand miles, like every 5K miles max, BEFORE you start seeing the wear. He stated that once the wear shows up, it is too late to switch the tire direction. That way you can get a somewhat better tire life. For optimal traction there is nothing you can do, that much camber will negatively effect the handling.

Sorry for the bad news guys, I was hoping for some better opinions as lowering the car seems tempting. With this info, count me out. However, I likely will do the spacers on my wheels after going home and checking my wheels for the inside groves to accommodate the standard wheel studs.

Albert

 

Haha, if 1.8 neg camber is too much what was my -2.3 lowered NSX's!!! Which btw were still mega fun to drive. Not sure this news changes the draw to lower. BMW M3's and E39 5 series have always had high neg camber too.

 

Yes, but with what wheel/tire combo? The older, taller sidewall tires deformed more under cornering, requiring more neg cambers. Heck, with the old RX-7 stock chassied race cars running 60 series R compound tires we ran 4+ degrees of negative camber. These modern, flat threaded, low and stiff sidewall tires must be maintained flat to the pavement, if not, they are running on that sharp and stiff inside edge.

The correct cambers for a 30/35 aspect ratio tire with 275 width should be under 1 degree.

Like he said, you can still lower the car, in normal street driving you probably will not feel much difference, just as reported by some who lowered the cars but, you will wear your tires quite fast on the inside. Your decision...

Albert

 

As I was driving the twisties on my way home today and my XK under-steered as usual, I thought of a different idea; just lowering the front end, not more than 1 inch. That would maintain the existing rear alignment, and the front could be aligned to specs after the lowering

The car would gain a slight wedge stance which, as a possibly significant side benefit, would help mitigate the heavy understeer of the XK. When dropping the front, traction is gained there which, in relations to that gained traction, would result in the rear of the car rotating around much better in turns. I have done that before and always liked a bit of nose-down stance for handling.

I assume that the total drop at the very leading edge of the vehicle, under the front bumper, could be closer to 1.5" when the springs are shortened 1" on the front and left untouched on the rear.

Also, I would expect, just going with the 20 mm set of spacers, front and back, would also result in a slight lowering of the car, simply because you would extend the lever that is acting on the springs. Not sure how much but, I bet it would be a measurable difference.

One thing I used to do on a number of vehicles where I wanted to lower not more than 1 inch, I simply cut the factory springs one turn. With the XK springs it would likely involve cutting one turn and using a torch to heat, flatten and grind the cut-end to seat it correctly. Cutting a turn out also raises the spring rates a few percent, likely enough for no bottoming. This used to be a popular lowering solution, done by leading performance vendors.

So, while likely not satisfying for those who wish to eliminate the wheel gaps, it is a compromise idea that could actually result in improved handling.

Albert

 

Yikes! Cutting and torching springs? That practice has been criticized since the Civic crowd made the practice popular along with installing annoying shiny mufflers! They at least did all four corners to screw up performance uniformily. The idea of dropping one end in such a questionable manner in an effort to deal with understeer just completely blows my mind.

Bruce

 

Bruce

I don't know what you're talking about? Screwing up performance uniformly by cutting and torching springs? How do you rationalize that statement?
How do you think springs are made, in general? They cut them, heat them and grind/machine the ends to shape them. I've seen top racing shops do it routinely making custom springs for well paying customers.

Do you have any better suggestion to get rid of the understeer? Swaybars would be better but, you can not buy them, as my old sponsor also pointed out today, there is not enough enthusiasts driving Jaguars for them to make and market those. Now, he will make you one by cutting, torching and bending a piece of steel but, if you have to ask the price....ha...ha...ha.... I remember the $12,000 custom bar he made for a Porsche 962 racer, oh, 15 years ago?

Besides, what is so questionable about dropping the front end and be still in range of all correct alignment specs? A slight rake in the car's stance is nothing unusual, some actually prefer that looks to a level stance. Now that I thought of it, I think that I will actually do it. I prefer to buy a new set of aftermarket springs, if I can find one with the proper specs but, if I don't I will have no problem with getting a second set of OEM front springs and cut/torch/shape them. I bet that mod will be a decent improvement over the factory handling.

Albert

 

Albert,

You can address understeer by adjusting tire size, pressure and alignment. Use a stickier compound tire ...did I read elsewhere you use all-season's? Maybe one day someone will make an adjustable sway bar or do the R&D for other suspension components. The lack of available options does not justify cutting springs, using spring stiffeners, or other off-road/race only procedures, but buying another vehicle that handles more to your preference shouldn't be ruled out if the other options don't satisfy you. Insurance policies have clear restrictions on vehicle modifications to consider as well. Ask your insurance company about continuing coverage with your proposed modification.

Purchasing new springs of the correct size, and with the desired spring rate, would be a reasonable approach if the existing spring rates could be determined, if it could be established that the electronic absorbers could operate properly in all regards with those changes, and if vehicle testing showed the desired results. Absorbers are designed to operate within a specific range of conditions, and are carefully matched to each application. I very much doubt that they could operate properly under your arbitrary approach of cutting the springs, or of changing the springs at just one end of the car, and I'd suggested those changes could easily lead to unpredictable and undesirable results.

By all means feel free to research the project, and let us know what you find out, but you're a long way from being able to suggest this as a safe or suitable approach to improving handling. I would hope and expect that after-market spring manufacturer's have thoroughly researched and tested their products, and they would have been done so using a complete set of four new springs...not just changing two.

Bruce

 

Bruce

You are incorrect on this one. Yes, you can adjust by tires size and compound but, at what cost and effort? New tires, new wheels for each test? One of the likely reasons for our understeer is the two different tires sizes, smaller up front, larger in the rear. Thus, balance is compromised. As to suggesting different compounds on the front vs. rear; now we are moving into dangerous waters; how will those different compounds behave as heat and wear put into the equation. Changing the alignment for tuning understeer is really not a good solution. That is not what alignment is for.

My suggestion for using the OEM springs and cutting them actually solves pretty much all the worries that you listed. You start with a KNOWN spring rate and raise it slightly by cutting. Likely around 5-10 percent per turn. Our OEM dampers WILL BE ABLE to handle the small increase. Also, Pacio reported no bottoming out with his HR springs that he claims are similar for comfort. I would lower my front less than Pacio, therefore, likely I would experience no damaging bottoming process with the dampers.

There is nothing unexpected or undesirable by using a factory spring, minus 1 turn. It has been done zillions of times by top performance shops when no alternatives were available. I have done it myself and if you think it is a "Civic" crowd-only trick, I have to tell you that my sponsor cut and reshaped my springs on my Lamborghini right in front of my eyes, which happened to give me this idea. Needless to say there were no springs available for the Lambo at the time and the improvement was lasting, predictable and significant.

As to dropping one end not being a viable solution, well, that is exactly what all racers do with their race cars. Just about every serious race car I have ever seen comes with threaded spring perches where the ride height is separately adjustable for each corner. It was the most common solution to dial understeer with the lowering of the front of the car as referenced to the rear. I had done that zillions of times in between session when a set of tire or track conditions caused the change in handling and my adjustable swaybar would not do the trick. Try doing such fine tuning by changing wheels or tires!

I always considered myself a good DIY fabricator. No brand, Lamborghini, Jaguar or any stood in my way of modding them, making them better. I built practically my GT race cars, welding them, building engines, transmissions, suspensions, fiberglass bodywork, etc. I have consistently shown that my alterations were for the better. My XK is a beautiful car, which is why I purchased it. Handling wise, it is far from ideal, leaving a lot of room for improvement, if that is a priority for some. You probably would have been horrified at the mod on my '05 XK where, following the example of a poster on this forum, I installed a second OEM swaybar in parallel to cut down on the understeer. That was a "truly radical" solution but, done right, it worked, held up for years, improving the handling of the XK significantly.

So, nothing wrong with fabrications. Oh, and one more thing; I would trust a spring that I cut far ahead of trusting the words of an aftermarket manufacturer or parts dealer that their spring rates, that they won't publish, are the correct ones. I have seen aftermarket springs tested by my sponsor that were over 2x the OEM rates and the driver was complaining that his car was loose in the corners and the ride was unbearable. The particular springs were from one of the major manufacturer and, likely intended for drifting and not street driving. But, the parts dealer sold it and installed it all the same for this fellow's fancy street car. Looking at the example of Pacio, as he reported, he used H&R springs. I went to the H&R website which stated that their springs were such high rates that they required new higher rate dampers. Wonder of Pacio missed that statement, or his parts dealer/installer missed that statement, as I do not remember seeing high rate dampers amongst Pacio's mods. So, blindly trusting an aftermarket product is obviously a mistake.

No, I am not using all season tires. The funny thing I realized yesterday after talking to my sponsor that I happened to have the very same Hankook Evo V12 tires on my car that he recommended as a solution for too much camber. When I purchased my CPO car over a year ago, these were put on by the Jag dealer, brand new. Now having 8K miles on them they still look great for wear. The funny thing was that besides the compound advantages listed by my sponsor for this tire, he also said that it was a super quiet tire. Indeed, it is super quiet, which got me wondering about my drone issues. When the tire makes noise on the rough pavement I do not hear any drone; it is being masked out. But, on new pavements this tire is simply so quiet that you hear everything else. Solution to my drone: buy a noisy set of tires???

Albert

 

I wasn't suggesting mixing tire compounds on the car but simply using a higher grip tire to minimize understeer, and you'll get more rear grip to tame throttle oversteer for free! I have staggered f/r tire widths on all three sports cars and none of them have an understeer issue so stagger does not create the issue. If cornering limits are determined by the fronts, even after cutting springs or whatever, then that's how you drive the car. The rears dictate my XKR limits and I respect that. If however you have less than 255's on the front, and that size won't fit on your existing rims, you can buy used factory rims in the for sale forum pretty cheap. Put on a good tire like the Michelin Pilot Super Sport and forget experimenting. Learn to drive it at the new limits and enjoy it, or change/cut springs, make/modify roll bars, whatever you like.

You can make that claim after you've done it, and I suggested an alternative other than spring work. Some applications have experienced undesirable effects from removing one turn, others have been successful. It's hardly a slam-dunk, especially if we consider whether the stock dampers can operate properly with the one inch shorter stroke over an extended period of time, and how well the damper valving can accomodate the different effective spring rate. Springs and dampers are best chosen together, and you'll be unable to establish the specs for either. Might be a good match, might not.

Another approach is that threaded spring perches are used to adjust overall vehicle height first, and then to corner balance the car on scales. Once set optimally they're locked in place and left alone. That's how sources I've consulted recommended it, and that's how the most respected Porsche race shop in Toronto does it. But I'm not sure discussing race car components and setup relates very well to the needs of the XK/XKR owner that wants to improve his car's looks or handling.

I think I picked up on that


That was the first thing I looked for. New springs and dampers together unless you can be sure they are compatible...and just because a set-up doesn't bottom out does not mean it's compatible.

I'm not trying or expect to talk you out of doing anything, but I wouldn't personally recommend the route you have suggested for the reasons I've shared. If you do it and it works well then that's awesome. I can see the wedge "Starsky and Hutch" look working for you...


hahaha

Bruce

 

Nice picture of the Starsky and Hutch mobil :-). Of course, I would hardly think that the XK would look anything even close to that. IMO, it would look BETTER, more aggressive with a slight wedge and with a 1.5" lower front bumper. You have to agree that the present 7.5" gap under the front bumper of my XK is way too high visually, while nice practically because it allows going over most parking curbs. Still, as a compromise, I like the 4.5" gap under my TT's' front spoiler.

As to locking in the corner-weighted settings, no serious racer would ever do that. Since you constantly adjustring the front to back ride heights to compensate for either handling problems or for the surface bumps on a given track that would be not possible or even advisable. I always adjusted my ride heights for each track so I would just barely scrape at the worst bump on the track and then raise the ride 1/4" from there. We carried our own sets of scales to the track and corner weighted the cars every time we adjusted the springs.

Most street/track cars do not even have adjustable spring perches installed, so it would be a complete waste of time to cornerweight them unless one wants to spend a lot on a shimming process. Even then these cars tend to be far too heavy for the process to make any difference in real lap times.

Albert

 

Totally. Now sell it and buy the one you should have...

Low, sleek, powerful, fenders stuffed with meaty tires for neutral handling tires ..."R" badge! Hang on, is that a slight "wedge" stance...good Lord, I think it is...perfect!!!

Which serves nicely to bring the conversation back around to Evoking, and his newer XKR, where he's considering lowering for appearance sake alone. I think both Albert and I agreed that a consideration would be whether the factory dampers would properly accomodate the lowering springs reduced length and increase in spring rate. Dampers are made to fit pretty specific applications in those regards, and I'd suggest the electronic units used on the XKR are very specific indeed. Afterall, they do receive sensor input from various sources to adjust their operation continuously to optimize handling, and that software was based on the stock springs and ride height. Jaguar did an amazing job with that software, and it would be worth the effort to try to find out if lowering will compromise either that, or the longevity of the factory dampers.

This is a good example of how not to treat your dampers...
Bullitt Car chase

Enjoy,

Bruce

 

What dampers are you talking about? Did those cars have dampers....???? They wallowed all over the road and turns, per the standards of the 1960's American muscle cars. Still, one of the classic car chases of all times that i never get tired watching.

The XK with my suggested spring changes would probably have no more rake in it than the XKR on that picture that you attached. I agree that it looks good. Now, why didn't I purchase the XKR vs the XK? Purely on the intended use issue. 85 percent freeway drive vs 10-12 percent twisties. If I want to burn up my local twisties I still got my TT in my garage that with its light 2600 lb weight, 500Hp and race suspension could not be even remotely matched by the XKR or even the XKR-S.

As I stated before my next purchase will likely be an other Jag. If I had to pick at the moment, it would be the new XJL. I really like the looks and the elegance of that car and the fact that it is only into its first year of this bodystyle. The new XK or F models may make me want them more but, those are at least a year down the road. I tend to not want to buy a model that is only 1 year away from being superseded by a new bodystyle and all around improvement.

Albert