www.jec.org.uk

A letter from John Seymour asking me to enter an item in the BB re this important aspect which if it comes into play we all would like to know how it activated.....i think this is in the correct dept ........Joe
The crux of the matter is, it does not appear to take much of a jolt to
trip the innertia switch, preventing vehicle starting.
In this case, the jolt was caused whilst jacking vehicle, it dropped only about 3/8" into the bottom of the fabricated locating channel on the axle stand.
Bearing in mind most jolts are through the suspension, these will be dampened, on normal running so the switch will not trip.
I am certainly glad I picked this up from seminar earlier this year, I think Paul mentioned this in the first hour, as I frantically scribbled notes down.
I note David Marks has copied to Nigel Thorley, so I daresay it will appear
in due course in J.E.............. John Seymour

Also at the seminar it was stated the correct procedures on jacking up a 308, you should always use the jacking points,even when you go into tyre fitters and garages. The positions for axle stands is under the coil springs as the box sections have rubber bushes which if disturbed can alter your alignment.
For the record watch that a "windy" tool is not used in conjunction with the special locking socket to undo or tighten the wheel nuts, as these have been known to shatter.....so changing a wheel is not just an ordinary procedure any more...........Progress?? who knows!..Joe

Joe, it is for me something of a coincidence that you should mention the use of what you termed "windy" tools to tighten/untighten locking wheel nuts. Last week whilst driving along the A12 to Chelmsford in the wife's X type we experienced a puncture. Using everyone of my sixteen stone I just managed to undo the locking wheel nut. The rest were comparatively easy. When re-tightening the lock nut after putting the spare on the head simply sheared off. (in a sense this was fortunate - had it happened while removing the nut we would have been buggered).

From what you say I'm assuming that two years ago when the tyre was replaced the garage used a "windy" tool. I've since been told that all nuts on a wheel should not be tightened beyond 120Nm. Do you know whether this is correct or will it vary vehicle to vehicle?

David.

David,any good tyre fitting depot now have a house rule that a torque setting for alloy wheels and the use of special locking sockets is a priority.
There is a torque setting for the 308 models, ( i dont know the exact setting?) with alloy wheels, as the overtightening can in some instances damage the alloy wheel. On some rare occasions it has been known to crack the wheel.
The correct procedure is to slacken the road wheel nuts off while the car is on the ground, using the locking socket and a suitable hand opereted wheel brace, then using the jacking points lift the car up to the required level.
Then either use an axle stand, or if on a ramp use the ramps equipment. After doing whatever work that is needed, replace the wheel and tighten up the nuts to hand pressure with a suitable wheelbrace then lower the car, and using a torque wrench check the torque settings.
If you dont have (as many of us dont have ) a torque wrench at the side of the road, tighten the nuts to what you think is tight,still using the hand held wheel brace and locking socket.
There is no need for extra tubes or bars to tigten the wheels up just tighten until you feel the nut nip.
Also when using axle stands evidently, dont just stick them under the first bit of box section that you can see, the correct place i believe, is under the coil spring base plate, the reason for this is on either side of the box sections is a large rubber bush which if disturbed can alter all your wheel alignment / geometry resulting in uneven tyre wear....expensive!!
Even at the side of the road wherever possible any work done underneath or in the raising of the car try and use an axle stand to support the car at all times never get under an unsupported vehicle.....i have a hydraulic jack and a stand as a combined unit in the boot that is in its own case and very handy if needed....Joe

David,
The wheel nuts on the XJR V8 Supercharger should be torqued
to 102 Nm. or 75 lbs.ft.
So I am told by the local indie.

Prospero.

Jaguar recommends:

Steel Wheels 68-82Nm
Alloy wheels 88-102Nm