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Hey everyone, I haven't really found much in terms of performance parts for these old cats, which I'm surprised no one has really modded these to modern era. The suspension is too old and soft for my liking, and I have noticed that in the upper spring perch there is a hole, which I see most people use to take out springs.
Question is could one not put a generic coilover that would be an eyelet mount with a tab on the bottom and a stud mount through that hole to make it a pretty easy coilover swap?
The hole I am referring to is slightly left of the jack.
and here is the coilover for reference.
Thoughts? concerns? Depending on the size of the hole you could just weld it to the proper opening size.
Hey everyone, I haven't really found much in terms of performance parts for these old cats, which I'm surprised no one has really modded these to modern era. The suspension is too old and soft for my liking, and I have noticed that in the upper spring perch there is a hole, which I see most people use to take out springs.
Thoughts? concerns? Depending on the size of the hole you could just weld it to the proper opening size.
No one. LOL I've taken many as far as they can go and still be street legal. There are a few others too. Xcessive manufacuring has a drift jag that's really well done.
If you have an I6 use V12 springs and a pan spacer then Bilstein or Koni Front shocks.
For the rear you can use Single QA1 adjustable spring and shock on the forward side is best. Start at 600Lb/in and any thing more than 800 will get really stiff.
Consider a thin rear swaybar and 1 inch front.
Add some 18 wheels and some ultra high performance 235 series Michelin Pilot Super Sports 4S tires (summer only) and you'll have quite a machine
Dont forget to upgrade all your bushes. Sold forward front subframe bushes help alot, and rack bushes help much too. Front eurothane lower control arm bushes if you're really really serious but I track my Jag and dont use 'em. They're squeaky and stiff.
Welding skills will help, not much bolt on. Dont forget the brakes.
Hope to see another on the track soon!
Last edited by icsamerica; 10-17-2019 at 08:15 PM.
There is a place in Brisbane (QLD Australia) that can do this mod (I have been told through only brief discussions with them) and it is on the to do list (in the distant future).
Basically I want to install the below theory - not for race related, but to be able to lift my car to get over speed bumps and to leave my drive way with out damaging my front (and rear) bumpers
Does require some serious re-engineering though (the backs are fine I have been told). It might be a pipe dream and never get done, but that is what dreaming is for
thanks for the reply. So do you think the front coilovers wouldn't work? What is your setup for the front? It will have track specific modifications to it down the road. One step at a time.
You also mentioned brakes, what are you running?
I do have xk8 rims on it with summer tires. Thats the extent so far. I want to work on suspension next. If I convert the rears to coilovers I can run 1 coilover per side on the front?
No one. LOL I've taken many as far as they can go and still be street legal. There are a few others too. Xcessive manufacuring has a drift jag that's really well done.
If you have an I6 use V12 springs and a pan spacer then Bilstein or Koni Front shocks.
For the rear you can use Single QA1 adjustable spring and shock on the forward side is best. Start at 600Lb/in and any thing more than 800 will get really stiff.
Consider a thin rear swaybar and 1 inch front.
Add some 18 wheels and some ultra high performance 235 series Michelin Pilot Super Sports 4S tires (summer only) and you'll have quite a machine
Dont forget to upgrade all your bushes. Sold forward front subframe bushes help alot, and rack bushes help much too. Front eurothane lower control arm bushes if you're really really serious but I track my Jag and dont use 'em. They're squeaky and stiff.
Welding skills will help, not much bolt on. Dont forget the brakes.
Hope to see another on the track soon!
meant to tag you in the post above. Where do you get your bushings from?
I run Aston Martin DB7 GT suspension front and rear. I was able to hang with a C5 Corvertte at Limerock until the final turn which is super-fast and and XJ coupe just doesnt have the CG to do as well. An XJS with 450HP might come close.
On the DB7 GT suspension everything is different except for the sub-frame itself. Spindles, springs, shocks, control arms, swaybar, brakes... all different and impossible to find. Took me 5 years of looking. I learned a lot from the DB7 GT stuff. Aston maintained the smoothness and managed to get prodigious amounts of grip and precision. Interesting items to consider are the front spring are super short and extremely high rate, so when the car leans over the out side completely unloads so the car is very flat. Yet the shocks are huge and soft compared to the XJ stuff. Also AM used rubber bushes in the lower control arms with nylon washers as sholders to limit movement. They also used solid aluminum rack bushes.
Look for my threads,I've posted many picts over the years.
.
Last edited by icsamerica; 10-18-2019 at 10:40 AM.
Superpro / Superflex are the Aus? & UK based suppliers for racing spec poly bushings, Polybush is good to but you might have to shop around to get the set you want.
I used all Superflex on my car except one key area has to be OEM I think it was front lower bushings? Or upper, something about excessive shock transfering into and stressing suspension components when you run all poly. Have all Polybush red 2x uprated bushings (discontinued?) on rear with uprated front and rear frame and cage mounts. The car tore the radius mount once already so thats an area to beef up.
The results I think are good, some people say the rear large radius bushing should be OEM and the small end poly for more flex in the rear, I wouldn't know without a second identical car to test. I don't race or anything I just wanted my XJS to be as planted and nimble as modern sports cars without issues doing near right angle turns at high speed.
thanks for the reply. So do you think the front coilovers wouldn't work? What is your setup for the front? It will have track specific modifications to it down the road. One step at a time.
Front coilovers were used on the racing XJSs produced by TWR on the 1980s. They require the subframe to be modified and fabricated at the top (more or less where the inner top wishbone fulcrum is) so that the top of the coil/shocker unit can be located just inside the top wishbone's fulcrum, thus running inside the wishbone triangles.
The racing XJSs had their subframes bolted solidly to the body, so the coilovers damped the entire structure. On the factory setup, the front shocker damps the entire structure as it runs from the bottom wishbone to the body. Mounting a coilover to the top of the subframe tower will not damp body movement completely if rubber subframe mounts are retained.
The only real criticism of the dynamics of the classic Jaguar independent inboard-braked rear axle (as fitted to the XJS and most other models of that design era) is that the rear shocks to not damp body movements completely, as the top is mounted to the rear subframe, which itself is flexibly mounted to the body. In the iteration of the design fitted (for instance) to the XJS's successor, the XK8, the rear shock absorbers were mounted at the top to the body, rather than the rear subframe.
So in theory it could be done in the spring perch? It just wouldn't be the best as the subframe is also going through the rubber subframe mounts? What about another option of putting a coilover where the shock is? Are you saying basically the twr had a mount in between the top a arm? Removing the metal where the spring currently sits would clear up some room for sure.
Originally Posted by Greg in France
Front coilovers were used on the racing XJSs produced by TWR on the 1980s. They require the subframe to be modified and fabricated at the top (more or less where the inner top wishbone fulcrum is) so that the top of the coil/shocker unit can be located just inside the top wishbone's fulcrum, thus running inside the wishbone triangles.
The racing XJSs had their subframes bolted solidly to the body, so the coilovers damped the entire structure. On the factory setup, the front shocker damps the entire structure as it runs from the bottom wishbone to the body. Mounting a coilover to the top of the subframe tower will not damp body movement completely if rubber subframe mounts are retained.
The only real criticism of the dynamics of the classic Jaguar independent inboard-braked rear axle (as fitted to the XJS and most other models of that design era) is that the rear shocks to not damp body movements completely, as the top is mounted to the rear subframe, which itself is flexibly mounted to the body. In the iteration of the design fitted (for instance) to the XJS's successor, the XK8, the rear shock absorbers were mounted at the top to the body, rather than the rear subframe.
So in theory it could be done in the spring perch? It just wouldn't be the best as the subframe is also going through the rubber subframe mounts? What about another option of putting a coilover where the shock is? Are you saying basically the twr had a mount in between the top a arm? Removing the metal where the spring currently sits would clear up some room for sure.
I have looked at Allan Scott's book and there are only two small pics that I can see of the front suspension. They fabricated bottom wishbones, and had a 1:5 spring leverage ratio (ie 1 movement of he hub = 0.2 movement of the spring - if I understand correctly). The spring shocker looks like it was anchored inboard at about the inner edge of where the factory spring pan is. In one pic the subframe had what looks like a 3 inch hole drilled in it behind the upright part that holds to top wishbones, and the S/S unit came up through it to the body. In the second (later) pic the S/S came up through the triangular gap between the top A arms (wishbone) close the the fulcrum. It must have also been anchored to the body and so must have been anchored at the top onto the wheelarch, roughly at a guess where the OEM one is anchored. I think that this second arrangement is what was used, as obviously it would be far easier to change the S/S unit mounted in that position.
A search turned up this set of photos. If you scroll down to near the bottom, you will find a side-on shot of the car, wheels off. It is clear that the S/S rod is coming up to the body inside the top A arm. I suspect some metal was removed from the subframe tower to make room for it. Essentially the S/S unit is where the OEM shock absorber is, but the bottom is mounted much more inboard. This gives a high ratio of hub to S/S travel (as mentioned above) so necessitates quite stiff springs to accept the higher leverage. https://www.dhrofgo.com/media/7457/t...nformation.pdf
Last edited by Greg in France; 10-24-2019 at 06:41 AM.
That picture would look like they ran an adjustable shock with probably lowering springs? Maybe I'll just have to go for it and buy one to see if it'll work.
That picture would look like they ran an adjustable shock with probably lowering springs? Maybe I'll just have to go for it and buy one to see if it'll work.
I know, for a fact, that the front suspension on the ETCC racing TWR XJS used spring/shocker units (maybe what you mean by coilovers?). Of course these had adjustable spring height and bump/rebound. The OEM spring position and its attachment points was not used. The ride height was controlled by the platform adjustment on the S/S unit. What is in the photo looks to me like the top of the rod from the spring/shocker unit attached to the body. Basically something that looked like an OEM rear spring/shocker unit; but with a greatly extended top mounting.
In your pic of a unit in your first post, the unit in the pic is missing a top mount for the spring, if there was one, then compressing the unit would compress the spring, so no chassis mount for the spring top would be needed, just a mount for the top of the shocker unit.
The spring on the TWR ETCC XJS unit was obviously a custom spring, wound to the desired strength, to take account of the different leverage on it from the different positioning of the unit on the bottom wishbone.
Last edited by Greg in France; 10-24-2019 at 11:20 AM.
That picture would look like they ran an adjustable shock with probably lowering springs? Maybe I'll just have to go for it and buy one to see if it'll work.
As others have said I would recommend to look at the Xcessive Manufacturing as they already designed a great full coil over kit that includes the front and rear for the Jaguar XJ; it is very nice with a nice inverted coil over setup in the front and a cool cantilever coil over design for the rear.
It is better to go with someone whom has a proven setup. I had to custom modify a coil over since my Jaguar is a 1963 3.8s and nobody has done any kit, but I did use the same QA1 coil overs you pasted in your original post for my setup in the front and rear and needed to have custom fabricated front lower control arms.
Yes, the Excessive site has a photo of what I was trying to describe:
Except that in the TWR case the unit was mounted further inboard on the bottom. And the subframe in this photo looks like it has been heavily modified to allow space for the S/S unit. It is not clear from the photo how the suspension load is being fed into the body and the subframe.
Last edited by Greg in France; 10-25-2019 at 12:30 AM.
Especially since the shocks are a load carrying part, when the car is lifted. 2 Bolts at the front, the tiny little cradle mounts at the rear and the shocks hold the engine and subframe in the car when lifted...
thanks for the insight so far. The picture I had attached is for a mustang. so the top mount for the spring would be in the mustang itself I would assume. There are other units like this one attached that is a custom mount, with different length options and different spring rates to purchase. Could I remove the front shocks, and the spring perch and run this where the shock is located? Looking at the mount, it would need a different mounting tab to get it to work but I don't think that would be too bad. Would the top mounting spot where the shock is located be strong enough to run a coilover or S/S unit there? That would be mounting from the subframe to the body correct?
Originally Posted by Greg in France
I know, for a fact, that the front suspension on the ETCC racing TWR XJS used spring/shocker units (maybe what you mean by coilovers?). Of course these had adjustable spring height and bump/rebound. The OEM spring position and its attachment points was not used. The ride height was controlled by the platform adjustment on the S/S unit. What is in the photo looks to me like the top of the rod from the spring/shocker unit attached to the body. Basically something that looked like an OEM rear spring/shocker unit; but with a greatly extended top mounting.
In your pic of a unit in your first post, the unit in the pic is missing a top mount for the spring, if there was one, then compressing the unit would compress the spring, so no chassis mount for the spring top would be needed, just a mount for the top of the shocker unit.
The spring on the TWR ETCC XJS unit was obviously a custom spring, wound to the desired strength, to take account of the different leverage on it from the different positioning of the unit on the bottom wishbone.
The shock absorber top mounting on the wing will not, repeat not, be strong enough to take the load of the spring/shocker. On the pic posted of the Excessive Dynamics mod, reproduced below, they seem to have extended the subframe to take the load, and then somehow attached something between the modified subframe and the wing. By the look of it, I suspect they have a rubber cushion in there, so, in effect they have another subframe rubber mount between the top of their modified subframe - to which the S/S unit is clearly bolted - and the wing mounting spot of the original OEM shocker. They must have something, or the front of the car body would be attached only by the subframe mounts and be completely undamped.
The wing is nowhere near strong enough, nor properly placed even if it was, to feed suspension loads into it at that spot, which is why the ED mod uses a modified subframe. Essentially, you would have to do something similar, or solidly mount the subframe to the body.
I would assume it wouldn't take much to reinforce the inner fender for the load. Most cars use strut towers mounted to the inner fenders and wouldn't be too different than the xjs.
I would assume it wouldn't take much to reinforce the inner fender for the load. Most cars use strut towers mounted to the inner fenders and wouldn't be too different than the xjs.
Strut towers are a designed-in part of a unitary body, with a wide diameter load-spreading reinforced area taking the load. The shock absorber top fixing on the XJS is reinforced, but not nearly strong enough to take the full weight and load of the suspension. The front subframe is the only member strong enough to take the full suspension loads. Essentially, feeding the loads directly into the body is no different from feeding them directly into a solidly mounted subframe, so why not do that? or even just fit much more stiff front subframe six shots, but still feed the loads into the subframe?
10-17-2019 | 07:49 PM
possible coilovers?
https://xcessivemanufacturing.com/ja...nsion-761.html
