Finally got the coilovers installed and so far I'm very satisfied. The car is about 5mm higher but looks perfect. The ride is firmer but more controlled when compared to the H&R springs alone. The ADS is fully functioning and the jag dealer verified there are no codes and nothing is out of paramter as far as the cars systems. The car just feels more planted and controlled I'm really happy so far. I could have taken the springs a bit stiffer but I think the key is going to be sway bars to really balance out the car.

I'll give you updates after I put some more miles on them. The car will be corner weighted and aligned by the same race shop that did the alignment a month ago, so I expect I'll feel more of the benefits then as well.

I'll post some pictures of the car when it gets out of the detailer tomorrow.

These are the springs used and the rear it has a tender, so it has a softer initial rate until the tender spring has compressed..

http://performance-suspension.eibach..._spring-system

 

Man, I love what you're doing to your ride. When will you be done? I hope you get the rear spoiler problem worked out. There's a thread about carbon fiber coating on the forum which can be clear coated for exterior protection. The carbon fiber coating would look great on your new spoiler, splitter, mirrors and vents. Always a pleasure reading about your mods. I especially love your choice of rims. Your putting some serious coin into your Jag. Please post us some detailed pictures of your car and the mods. You're going to have extraordinary well done XKR, not murdered, not over done, just right and better.


How does your upgraded suspension compare with the dynamic pack/XKR-S suspension?

 

Thank you sirs!

I think next will be the diffuser probably in Carbon, side sills(95% sure), Alcantara wheel, new paddle shifters of some kind, and I will probably replace the spun aluminum passenger side airbag cover/ driver side dash surround with the black piano pieces to match the center dash and console. I may also go with high flow cats as well but not sure yet lets see what the dyno says with the soon to be new tune. That should be it as I want to get started on an Elise for a track car

Compared to the R-S its a bit stiffer but more planted and predictable. Dare I say 911ish in feel as the car feels very lite. Its definitely a bit more tail happy under heavy throttle but very controllable and predictable in corners. The tail bob is finally gone and out of Dynamic mode it feels about the same as an R-S with more damping. So far I'm really happy with it, the corner balancing and alignment will be done Wednesday so after that I'll see more of the benefits of the coil overs. First track day will be Homestead on the 21st and possible Palm Beach Raceway before that if I force myself to take some time off.

Oh and the rear spoiler it ended up fitting perfectly and looks great. I'll get some pics up after I pick up the car this afternoon.

 

Did you have a choice with the spring rates? Do you have the rate numbers on the springs? I assume that the car sits where it sits just as the initial adjustment but, you do have the option to raise it or lower it on the adjustable perches? Also assume that it will not effect the warranty, other than maybe with the exchanged suspension pieces.

Sounds REALLY good. You are doing a great job of leading the way with the suspension improvements. You mentioned sway bars for the final tuning? What is available? I guess, only the XKR-S (or GT) bars? Do you know how they compare to the stock XKR bars?

Keep up the great work and documentations.

Thanks,

Albert

 

Here is what Spires sent me about the springs and dampers. They used custom Bilstein F-Type derived dampers and with the Eibach springs I mentioned before. The ride height is fully adjustable from stock down to 30mm which is what I have it at now. The height and rake may change a bit when its corner balanced but I want to keep it as low as I can while maintaining proper suspension function. We discussed many different rates and the ones below are the ones they have been using most customers XKR/XKR-S that are tracked often with experienced drivers. I have to say they have the spring and damper rates sorted.

Quoted from Matt@spires
"The dampers are subtly different in rebound and compression forces (circa 5% stiffer at higher forces and 5% softer in the lower forces). This will help with traction on slower bends and pull away, but give more ultimate control when driving quickly.
It's more the increased spring rate which will give the most benefit to the handling performance. The front spring goes up to 100N/mm from 79N/mm and the rear increases to 120N/mm from 95N/mm."

As far as warranty my dealer is ok with everything I've done so far they even replaced the aftermarket exhaust clamps for me yesterday with stock Jaguar pieces for free. The aftermarket pieces that were used would bumped against the underbody when I was accelerating and making a left turn.

For sway bars I'll probably end having some race shop custom make some adjustable bars as I don't think the XKR-S bars are stiff enough and the GTs geometry is a bit different. Beside they want 2600 for the GT rear bar, and I sure I can find custom setup for around that price if not less.

 

Is the ADS actually useful?

 

For everyday driving yes, just unplug them and go drive around and you can feel the difference.

 

That's about 26% firmer, so you're approaching the spring rates of the Dynamic Pack (though I guess the profiles are different, particularly with the tenders fitted). Are the dampers fully variable or stepped like the 4.2 ones?

 

The dampers are fully variable and a newer generation since they are based on the F-Type damper.

What are the spring rates on the Dynamic pack/R-S?

 

Don't know the absolute figures, but the front springs are 28% stiffer, rear springs 32% stiffer than the standard XKR (though the marketing blurb often shorthands it as "30% stiffer"). Based on your standard figures above, that would make the front about 101 N/mm and the rear about 125 N/mm.

In addition, the Dynamic/R-S package has different front suspension uprights that increase camber stiffness by 30%, and revised rear uprights. There's also a different Active Dynamics tune - probably just a different map rather than different firmware.

 

Heres a picture of the car with the Coilovers and the front/rear spoilers installed. Its a little higher but not much.

 

DGL - totally forgot to address your carbon fiber question. I'm still not 100% on where and if I'm doing carbon, I'm pretty sure I'll get the rear diffuser in carbon but other then that I'm not sure. I dont want to over do the carbon as my goal is to enhance the XKR, and add parts the bean counters would not allow the designers and engineers push to production. So that being said I'm still up in the air on the carbon but if I add the carbon diffuser it has to match something else on the car. What else its going to match I'm not sure.

 

Looks GREAT! Would like to hear your review of the handling and the ride qualities once you get some seat time in the car. I am wondering if the software for the suspension has to be changed for the F-type dampers?

Albert

 

I thought you may want to get your rear spoiler carbon fiber (CF) dipped and clear coated before putting it on. CF with black looks very subtle and rich. I wrapped the mirrors and front splitter in CF vinyl wrap on my sold 175 and liked the look. I'm thinking about removing my splitter, rear spoiler, vents and mirrors and having them done. IMO the CF would look great with your HRE gun metal rims. Picture below.

 

That looks really good, the Carbon splitter would look great with the carbon diffuser.

 

I was told the software is fine and you can tell when you put it in Dynamic mode. Its a very noticeable difference, much stiffer and much less forgiving. It's very stiff in dynamic and exactly what I wanted.

I'm getting the corner balancing and alignment done tomorrow and will post the results of the weight distribution and alignment when I get home.

I'll say so far I'm very happy, they are not cheap but anyone who has owned a car with coilover knows where I'm coming from.

 

Just got back from the corner balance and alignment. Car feels great and I will post the results later tonight or tomorrow.

 

So here are the final specs after the corner balancing and alignment. As before he drove the car made some notes as to where it pulls, how it turned in each direction, turn in feel etc. Then brought it in and got an initial alignment, then set the ride height with a slight rake as he knew it would need one for the proper balance. The he placed 170lbs in the driver seat to simulate me, and went back and forth between alignment and height adjustment to balance the car out to a near perfect cross weight of 50.05. The ride height measured at the pinch welds behind the front wheels and in front of the rear wheels is 4 1/2" front and 4 7/8" rear, with a 1/2 turn on the right rear spring collar to finally balance it out.

The attached photos show the final alignment specs, last three cross balance sessions weight, ride height and how it progressed.

Also the car weighed in at 4139 with 2/3 tank of fuel and 170LBS of weight so its no lightweight literally LOL

I only had a chance to drive it home but it felt great very responsive, and it felt like a light sports car which is exactly what I've been chasing!

 

I do like your final alignment specs. The rake is one way to make the rear end more neutral without installing a larger rear sway bar. What I am dying to see or find out is; what were the effects of the lowering on the rear camber. Your final camber numbers look fine, although 2.0 is starting to look a bit too much for the street. My old XK's factory non adjustable rear camber was 1.7 negative which I figured to be good but, I was very worried that if I lowered the car it would go way over 2.0. Not sure how the rear suspension geometry effected by ride height?

The one thing, however, that alarms me is the spring rates. First, I never set up a car that weights over 4000 lbs so. But, in every single instance with front engined cars, I always set the front springs stiffer than the rear springs. It seems as if the ultra-stiff rear springs are designed to compensate for insufficient sway bar size; which would be, IMO, the very wrong direction.

For instance, on my RX-7, which has absolutely superb handling, I used 350 or 375 lbs fronts and 275 rears, in combination with a 3/4" adjustable swaybar the rear and 1 1/4 front. I always preferred relatively soft springs, particularly in the rear for good traction. Looking at your new spring rates and deriving the stock XKR spring rates I now suspect that I may see the reason why the XKRs are so slow on the tracks. Those stiff springs in the rear truly limit traction.

Again, I apologize if I am wrong as the cars that I had set up before weighted more like 2600 - 2800 lbs. So, naturally, they needed less spring rates. But, to me the higher rear stock and Spires springs rates seem very backward. I need to be educated on the philosophy for such setup.

Do you know how the Spires spring rates compare to the H&Rs?

Also, had a very disappointing appointment yesterday with the Jaguar NA rep, regarding the bad ride of my XJL. We went for a test ride, and my car refused to co-operate, the ride was actually acceptable (not great). So, naturally, nothing came out of the meeting. On my way home over the very same roads, I was cursing all the way; the ride was fully terrible. The only thing I could figure is that both the Rep and the Service Manager who rode along weighted way over 200 lbs and that extra 500lbs weight must have smoothened the ride. Guess, now I am stuck trying to figure out how to dump that XJL early in my lease. My personal opinion, without knowing the stock spring rates, is that the rear springs on the car are far too stiff and they will defeat the dampers at high frequency vibrations, such as from certain pavement types.

Albert

 

I was wondering about the spring rates as well as you typically have higher rates in the front on a front engined car. The stock rates are front 79N/mm( need to convert properly)and rear 95N/mm, and this is also common on stock and modified BMW M3s/M5s so its not out of the ordinary. The higher rear rates remove the inherent oversteer on these cars. Keep in mind how heavy all of the above mentioned cars are as well.

Whats interesting in non Dynamic mode the car feel as soft as it did stock but with better control. In Dynamic mode its race car stiff but feels great at higher speeds. Overall the feel and control is very good.

The H&Rs are supposed to be stock spring rates but can't verify that as they do not post the rates. They are not stiffer that I can attest to.

You would have laughed when he disconnected the rear sway bar on one end. You can literally move it through it range of motion with one finger.

Sorry you couldn't get your XJL issue resolved, I personally think the rear of these cars are not damped correctly.

I just did some quick searching on this and the E36 BMW can run 400LBS fronts and 800LBS rear due to motion ratio. Now I'm not a suspension thats a start.