So I finally got my 99 XJR off the jack stands and did a danger run around the hood before dropping her off for an alignment check and brake fluid flush. Initially she went up in the air to allow me to remove the trans valve body to replace the conductor plate and do a fluid & filter change. While I was on my back I noticed the outer tie rod boots were gone then slowly as I was doing work realized all 4 ball joint boots were gone, the stabilizer bar link bushings were shot, brake pads were almost completely gone, all 4 rotors were beyond their service limits, and front calipers had slipped their dust seals. I had shocks for all 4 corners waiting in the basement along with a fuel filter, and a couple of quarts of fresh rear end lube so I accumulated a few more parts and started to work.
Well after finishing off most of the list I couldn't wait any longer and had to drive her around to see what a difference I'd made. I was shocked that I had a slight wiggle in the steering wheel that got worse as I got up to 30 mph. Thinking it could be how I'd set the eccentric wishbone pivot bolt after the ball joint job I left it at the shop hoping the alignment would take care of things. It didn't but when I got the call to let me know she was all set the service manager told me that on their test drive they'd spotted the wiggle and looked all over for a bent wheel. They found that one of the lug nut washers had come off the lug nut and jammed between the wheel and the rotor when I'd put everything back together. Lucky I had it in for the alignment soon after reassembly or I could have really screwed something up.
These stock lug nuts always impressed me as overly complex for the job they do. Has anyone got a source for a traditional, single piece lug nut to replace these with? FCP Euro sells some fancy theft resistant ones that need a special tool but I'm looking for a simple hex nut that will fit over the studs and hit the tapered seat correctly on the wheel.
After all this I do have to say that with the offending washer out of the way the old girl feels like a new car and all the little rattles and clunks I'd become used to are silent, very nice feeling indeed!

 

There's tapered seats in the wheels? Got a pic?

 

There are no tapered bore original rims for the X308. The rims need the washers for friction and protection. No way tapered nuts are going to work...

 

20pc OE Mag Style Lug Nuts with Washer 12x1 5 Toyota Lexus Chrome Silver | eBay

Tom in Dallas/Plano

 

I thought x308 oem lugs were 1/2-20?

 

I am not sure about your car, but these are an ideal fit for my 05 S-Type.

I show the lug nut part number for your car to be CCC7028 (CCC007028)

http://www.ebay.com/itm/WHEEL-NUT-Ja...-/291560403722

http://www.ebay.com/sch/i.html?_nkw=...&ul_noapp=true




Tom

 

I believe they are. And I can confirm that the Eurospare CCC007028 nuts are a perfect fit.

 

Part number comes from Jag EPC and if you plug in on Internet you will find verification at numerous Jag dealers, (Terry's and others).

Tom

 

You are in the X308 section.

Completely different animal.

The X308 has 1/2-20 imperial/SAE thread wheel studs
while the S-Type uses metric thread.

Wheel nuts to fit a X308 will not fit a S-Type and vice versa.

 

No idea of what that wall of text contains.

There is no cautionary tale other than user error.

 

I am aware of that after the post. I just gave him the part number for the correct part from the Jag EPC

T

 

Plums,
Cautioning people to check the washers on the end of the lug nuts when they remove and replace. Certainly my fault but you know what, this is the first car I've ever had to deal with this type of lug nut, and I still don't know why they can't be one piece like every other car I've ever taken a wheel off of...

 

It's due to the manner in which the wheel is located and centred with respect with the hub or spindle it's attached to..

Cars with tapered lug nuts have wheels with matching tapered holes where the lugs/studs to pass through. The tapered-against-tapered surface hold the wheel concentric with the hub it's mounted on. This is called 'lug centric' wheels. The lugs and lugnuts take all the radial load as the wheel rotates.

Jaguars, and other cars, use a different system where the wheels have no tapered holes for the lugnuts to mate against. Instead, the wheel is kept concentric by having the centrebore of the wheel match a spigot on the mating hub of almost the same diameter. This is called hubcentric wheels. The centrebore-to-spigot tight fit takes all the radial load and not the lugs and lug nuts.

Your wheels have no tapered bore for tapered lug nuts to fit against. Instead there is a square, machine shoulder. Using tapered lugnuts would create tremendous stress, possibly cracking the wheel.

Use of a two piece lugnut allows the nut to be properly torques while the washer prevents scoring or galling of the significantly softer wheel surface.

 

I understand the design decisions Jaguar's engineers made I just don't think they were well thought out in all cases. Plenty of cars running around with taper seat, one piece, uncomplicated, lug nuts that don't crack wheels. The ones on my e39 beemer actually fit the hub and have a tapered slot for the lug (bolt) to bear against. Complex solutions aren't necessarily better, just complex. Sometimes you have to take a step back and ask yourself if something simpler would work just as well.
In looking for lug nuts to at least replace the broken one I've noticed these same parts work for XJS's so maybe this is some left over, "we always did things like this" decision.
Surprising that the metric post from the S type owner was an ebay listing for a Toyota. I'd expect the Japanese to know better...Of course my Mazda RX-3 relied on the same tapered seat lug bolts as the beemer, not bad in your driveway but on a rainy night on the side of the road loads of fun to line up that first bolt.

 

Do the wheels have a tapered seat or a square shoulder?

 

These are the stock XJR wheels and apparently have a square shoulder. Looks like I'm stuck with something like the stock nuts as long as I use these wheels. I'll just have to pay closer attention when reinstalling and toss anything that looks like it's ready to be two pieces instead of one...

 

That was my point- a tapered lugnut cannot be used with a square shouldered wheel.

The design is not unique to Jag by the way- it's quite common on newer cars with alloy wheels.