Sounds great what model XJS do you have? What further plans and mods do you have in mind.

With my suspension I am keeping the stock springs (at least for now). I will remove the 2 packing spacers under the front springs to lower the front end. The rear I will look at modifying the lower spring seat on the shocks to lower the car. Not sure yet how or what this is a while off yet.

I bought an 18mm rear sway bar but it will not fit without moving fuel and brake lines and relocating ABS sensor wiring. It does not mount to the factory mounts.

My car does have factory mounts but no bar. So my plan is to modify the old 22mm (7/8) front bar to fit the rear and add the new 18mm bar in parallel so dual bars, and adjustable.

Front bar I might upsize from the 24mm (1") to a 30mm adjustable.

I have a 4L60e to go in and I have already rebuilt the diff with 3.58 gears. My plan was to rebuild the undercarriage before I commence any mods, the rear is finished and I am well into the front. I have found a few things that need to be replaced, like the stub axles have had the wheel bearing spin so they need to be replaced as do the caliper pistons.

Once I have this completed I can then evaluate how the car handles and start changing things. Engine rebuild will most likely late this year or early next year.

 

i have an 87 he xjs, i plan on doing something to get rid of the large radius arm bushing and make something with hemi joints and threaded rod, A for tire clearence and B to stop the wheel hop. i am still trying to figure out how to fit an adjustable sway bar in the back, since i have no idea how the orignal fit to the car. i would like an inch in the back and maybe an inch or an inch and a quarter in the front. im planning on lowering the car 1.5in and using 18X8/9 bbs Lm wheels. and i am also attemtping to get the hyper xjs body kit from paul hands. AND im also doing this as my highschool seinor project because im a 17 year old highschool seinor.

 

Well for a young person you have good taste in cars.

You do not want to solid mount the radius arm, doing this will increase the amount the rear end is pulled as the wheel moves through bump and rebound. The ideal solution is to remove the radius arm and add a mount to the chassis in line with the inner fulcrum shaft and install a new radius arm to this point, the wheel can then move freely.

 

what is the rate amount of travel the wheels have?

 

i talked with some guys that i autocross with today, (16, xjs, 5 speed, and autocross dont mix very will i know)
and they were telling me that spring rates and rollbar stiffness are all varaibles of

personal preferance. some people put larger swaybars in, But larger rear sway bars

tend to make a car have snap over steer, drive or as a 911 or 930 owner and they

will tell you how horible it is. which is why the iroc-z camaro my friend lent me to drift

in has 1.25in in the rear and 1in in the front and it's rear end flies out on every turn.

Too stiff springs will allow your wheels to hop out, too easily, but too soft springs will

allow too much body roll in all directions, too stiff dampeners will cause the car to not

propperly shift its weight bias and will result in impropper breaking, causing you to

have to adjust brake bias. too soft and you will be fighting the body jerking around

on every shift. its all a balance game.



two of my friends have moderatly stiffer springs and all around sway bars of high

stiffness, while another has stiffer springs and smaller sway bars, and the best driver

of all of us has very stiff springs with heavy shocks and a heavy front sway bar, but

no rear sway bar at all. he says it keeps more rubber on the back when he pins a

hard turn. His car not mine.

Each option has the option to be set up in a car with the rest of the suspension designed to match and work with it.

 

You are pretty well spot on there. Suspension setup is an individual thing and requires a holistic approach. Everyone will setup a car differently. The aim is to get as much traction from both ends as possible. If you run stickier tyres you can firm up the suspension as the tyres grip more the car will roll further. If you go too stiff the weight is not transferred on to the tyre and the tyres will lose grip.

So stiffening the rear or softening the front will increase oversteer, and the opposite will increase understeer. It is a matter of balancing front and rear roll stiffness to get the handling to your liking. It is easier to stiffen a sway bar than to stiffen spring rates, this is why I like running softer springs and adjustable sway bars. Also if the spring rate is too stiff the car will tend to hop over undulations and when the tyres are not fully in contact with the surface you lose traction.

Dampers only control the rate at which the weight is transferred - so stiffen bump on the rear and the car will tend to oversteer on entry (we are talking about a sweeping steady rate bend) before settling. Too stiff on rebound and the inside wheel will not drop quick enough reducing the anti-roll bar rate.

The top V8 supercar team here in Australia runs the softest spring setup in the field. This allows the car to ride the ripple strips better than others it also gives them better drive out of corners.

 

Please excuse my butting in to this very interesting thread. I just wanted to mention that the rear camber seems to have a huge effect on the cornering characteristics of the XJS. The racers in the UK all remove sufficient of the camber adjustment shims from the driveshaft inner end where it bolts to the diff, to give up to a degree or even a touch more of rear wheel negative camber.

I have about 3/4 of a degree of negative camber on my standard sprung road car and it transformed the rear, particularly in damp conditions, making it much more grippy and with very predictable break away.

Greg

 

Negative camber meaning the outside bottom of the wheel moves out or inward?

 

Negative camber the outside bottom of the wheel is further out than the top.

The idea is - as the car rolls onto the tyre the tyre flattens on the road surface. The negative effect is greater wear on the inside edge of the tyre in a straight line, and for front wheels with a lot of negative camber the car will tend to tramline.

 

Thanks Greg thats good info - I have currently installed the standard shims back into the rear, I was planning on playing with these once I got a benchmark.

 

is i got lowering springs made that were 50% stiffer all the way around, would that be stiff enough to keep a 18x9 wheel with 265-275 tire from rubbing? just curious

 

sway bars wont give you a firmer ride, just less body roll.

 

???? If you read the post I was talking about weight transfer as it relates to over/under steer, stiffening a sway bar WILL give you a firmer ride if one wheel moves through bump as the other moves rebound. Like going over a speed bump with one side wheel only.

Too many variables to comment on this. Ride height, offset and camber will all contribute to tyres rubbing if the clearance is tight like it will be with 18x9's

Ride height especially if the top of tyre is level or inside the guard they will almost certainly rub. Not necessarily on the lip but on the inner guard higher up as it curves inwards.

 

The way I set about measuring for fitment was to use cardboard, one piece cut 280mm wide ( a few mm for clearance and other errors) and another bit to fix to the wheel hub from this you can measure what offset is needed.

I also removed the springs so I could move the hub through its movement to the bump stop.

I have attached a rough pic of what I mean, hope this helps

 

yeah ill go this, this weekend and hope fully ill be able to start looking into a new wheel purchasing!

 

just put the car together, with what you think is correct, and drive it!

then make adjustments that fine tune it!

JEEwhizz nothings ever perfect anyway!

 

i was just looking thru an old 1977 Road&Track , and Group44 racing XJS changed the rear suspension and radius arms. they kicked buut in trans-Am with it.

i think i can(maybe) post a picture of it,from the magazine. its before internet existed!

 

i wanna get as much right the first time as possible so i dont have to keep spending money!!!