www.jec.org.uk

As you know, or may not, I am new to all this XJS business, really enjoying though….

I have a 95 4.0 Coupe. The tyres are a brand I have not heard of and look a little agricultural, that may be a clue. At an alleged speed of 85 there is a vibration in the foot area not on the pedals and not through the steering, nothing serious but you can feel it. The car also feels vague with the steering and not sure footed (would not feel comfortable over an alleged 85)… Any thoughts?
Many thanks,

Carl

It's not unheard of for people to put van tyres on XJS's because they are the same size. Where they don't come up to spec is speed rating etc.
I would suggest finding a decent tyre specialist that has the proper equipment to do a full geometry check on your car. If they have the right equipment then they can measure toe-in, camber and castor at the front and camber at the rear. Toe-in can be adjusted relatively easily but the other settings take a bit more spanner work.
I use Micheldever Tyres near me both because they have the right kit but they also have a guy called Julian who really knows his way around Jag suspension. He even has developed his own settings to improve on the standard set-up.. He's done both my XJS's and made a real difference.
Hopefully you'll find someone like that near you. Cost should be £30 or so to check it and correct the toe-in.
Another thing you may want to get checked out is the wheel balancing but, as you can't feel it through the wheel, it's unlikely to be the front wheel balancing that's at fault.
If you can feel the vibration through the body of the car and the seat of your pants then it's more likely to be the back wheels that are out of balance.
Probably worth getting those basics checked just to eliminate them before looking for more complex issues.
Hope that helps
David

wheel balance ?

BB

wheel balance ?

BB

I suppose what I mean is the balancing of the wheel and tyre combination to ensure that it does not wobble due to uneven weight distribution.
Sorry if my language was imprecise!

Carl,

I tend to agree with David's view that if you're not feeling it through the steering, it's less likely to be the front wheels.

Another option could be propshaft imbalance, but I'd certainly get all the wheels balanced first before looking further.

Good luck

Paul

What brand are your tyres? The size and quality should be 225/55 ZR16 98W which you will find written on the tyre wall. You will also find the date of manufacture which appears as a number such as 2212 which means week 22 of 2012. If you find Black Circles on line and put in your reg number you will find a whole range of suitable tyres.

I agree that if you are not feeling any vibration/wobble through the steering wheel (you lucky bugger!) then it won't be the front tyres regardless of what brand they are (just make sure that they are the correct speed/load rating otherwise it could affect your insurance in the event of a claim).
Vibration could well be coming from a tired gearbox centre mount, propshaft UJ's knackered or shot bushes on the rear suspension.
Vague steering is a classic sign of worn radius arm bushes or corrosion where they are mounted; there will be a tendency for the back end to try and steer itself until you are back in a straight line. Highly entertaining in the dry but a but worrisome in the wet!
If you are taking the car to a garage to get the work done it will be worth soaking all the bolts in WD40 or similar for a few days before you go; it could knock a couple of hours off the labour cost; the bolts can be a pig to get out.