Got the final alignment. Strange that moving one caster shim forwards on Right didn’t make much difference, but moving one caster shim backwards on Left made a huge difference? I said now Left is out of spec, but he said it will be fine, and like you guys, he said you want the Left a bit smaller angle than the Right. Or did they just not want to bother to do another pass? (I already got two alignments for the price of one) Should I move the Left shim back to where it was? Or will that mess up my Toe In?
I’m almost thinking of moving Left back to 2/2 so it would ‘roughly’ be back near 3.75, and then moving Right one more forward so it’s 0 Rear/4 Front, hopefully getting close to 3.75. I’d rather have higher caster. But I wouldn’t know the real values unless I went for a third alignment. Ho hum.
Front Camber now looks good. And rear thrust is not bad. He said anything with a 0.0X is great.
Front looks good.
You could move one shim back on the left side to increase Caster, it will not affect Camber or Toe, but it depends on how much road inclination you have on your roads, your personal taste and OCD level.
But as the rear (if the measurements are correct) will have a slight tendency to steer the car to the right due to the thrust angle it’s maybe not a bad thing.
On the rear there are some inconsistencies…
Left Toe: from -0.01"/-0.02" it’s now +0.04. This is 0.05" - 1.2mm difference.
Right Toe: from +0.06" it’s now +0.01". This is again 0.05" - 1.2mm difference.
You don’t know if Rear Camber is correct without the mid-laden tool, but it’s equal and consistent.
How the car drives and how the tyres wear is the ultimate test.
OCD aside, if it goes straight and doesn’t pull it’s fine.
But keep an eye on tyre wear.
Well, my OCD got the better of me, I didn’t like knowing caster was out of spec with a decreased caster. (I like my car sporty) So I moved one shim forward on BOTH sides for more Caster. (Left is now 2/2, Right is 0/4)
Car still drives nice and straight, no real change there. But I tried a few hard turns, and I swear the car cornered better, felt like oversteer, or was this my imagination with such a small change?
Well, I gave it a really good test drive. I’m going back to how I had it this morning! (L 3/1 and R 1/3 that I had with alignment)
It’s way too twitchy on the highway for my liking. I guess combined with my steering rack poly bushings, it’s just too much…barely any turn of the wheel at 60mph and you’re moving, but you can feel the body lagging. Kinda scary. At least I better understand how Caster can affect steering.
Increasing caster should make the car LESS twitchy. It increases self centering of the steering. Did you recheck your toe-in after changing caster? Caster can affect both camber and toe.
In many other cars it could be the case, my Mercedes for example.
But not on the Jaguar.
The shims move the upper pivot just front/back and do not change the Camber angle, nor Toe.
I think Caster has nothing to do with this Greg.
Caster effects the tendency of the wheels to go back to straight. If you had zero Caster you would turn the steering wheel and it would stay there, no coming back action.
It does also have the effect of increasing Camber when you turn the wheels, but in such slight variations of Caster the change difference is very small.
But your poly steering bushes would have that effect for sure.
Plus the fact that the car is now aligned, all four corners are equal and with correct angles, so there is no tyre friction and the car obeys commands much more willingly.
BTW, my car is also like that, kind of twitchy on highway speeds ever since I addressed my steering bushings.
I could even say that before it was more confortable when going fast and straight.
Maybe the reason for the original steering bushings design was to give some deliberate slack to make the car less responsive.
But, like everything, it’s an other compromise…
Interesting info, thanks. Well, I’ve put it back to the way it was when it was at alignment shop, so I’m just going to leave it. Yeah, those poly steering rack bushings really have a lot of pros/cons. Though I do like the overall response better, so just have to get used to them I guess. So subframe is in, suspension is rebuilt, and car is aligned. Time to move on to the next issue!
I have had the poly rack bushings for 10-12000 miles; I immediately noticed increased feel (harshness to road irregularities) in the steering wheel and twitchiness at higher speeds. I also installed a Motolita steering wheel at the same time which might be part of the harshness.
It now seems normal, probably a combination of the bushings breaking in and my getting used to it.
I’ve driven many cars known for their superior cornering/handling prowess. In most cases the steering is so hyper-responsive that it becomes an annoyance, IMO.
Driving a Jaguar should never be annoying. It should always be pleasurable.
The Jag engineers, when faced with the inevitable compromises, always tended towards more comfort, more softness, less NVH. As a result these cars respond very well to modest “let’s firm-things-up” type changes. That is, small changes yield a large result.
Go too far, though, and the negative sides become apparent.
Speaking of, I definitely want to keep my poly rack bushings and poly lower control arm bushings. But I’m thinking of going back to rubber for upper arm bushings for a degree of more comfort. Do these make much difference?
I’ve never used poly control arm bushings on my Jags so I can’t speak to that. Over the years there has been a lot of discussion; I think the consensus is against them. But let’s hear what others have to say
