Anyone know what the top speed of a xk8 would be

 

Above the speed rating of the tires you have on it. I think the XKR is computer limited to 150.

How old are you?

 

My tires are rated above 168 and next week I'll turn 69. Still wondering if it will do the 170 on odometer

 

Everything I have read says "limited to 155" . The bad news is they, to my knowledge, have never said why they chose that number. Does the car lift? Does it become unstable? Was it arbitrary?

The Pirelli PZero tires it came with can certainly exceed 155mph.

I've seen articles analyze the engines power output and propose it could break 170 without the limits jaguar placed on it.

Anyone know why Jaguar chose 156 as the limit?

 

I've had mine up to 130 and I can tell you the suspension is very light at that speed. I'd guess the car lifts at speed and will become unstable, after all it is shaped like a wing! But what do I know

 

I had a 1970 Super Bee up to 135 with power to spare but was floating too bad to continue

 

I have read that the 155 limit is sort of an "agreement" with european car manufacturers, but not an actual law (or in the US either). Some Brits will be along soon to comment on that.

At 155 it is probably easier to get tires that would be affordable to the average buyer.

125 is my personal best (allegedly). Ran out of empty road before I ran out of acceleration. More importantly, it will run thru a full tank at 90 mph and not break a sweat (also allegedly).

 

Don't know if the lower scoop on the nose of the 2005 has anything to do with it, but my guess from experience, says it does. As I posted earlier, I've had mine up to 130 just recently and it was solid as a rock. I chickened out before the car did.
I think Jaguar has the cars electronically (probably thru the computer) limited to 155 and I think it could get that with ease--at least the 05 and 06's could. Since the earlier models don't have the lower scoop, they may in fact start to lift.........

 

+1 I had my 66 Charger ~130mph in 1966. It did not float , maybe because I was going into a curve around I-85 NC mi mrkr 18S. (I wasn't daring, just a stupid foolish kid)

My thinking on the speedo, 155mph is right at 250kph which sounds like a nice round number to limit it to.

 

In 1987, mass-producing German auto makers, such as BMW AG, Mercedes and Volkswagen AG, entered into a voluntary agreement with the German government to limit the top speed of even their most powerful models to 155 mph (249 km/h). This “gentleman’s agreement” was conjured up to offset a “social and political environment in Europe,” that was beginning to target automobiles as an environmental liability, says a BMW insider. If all cars pollute, fast, powerful cars must be particularly unsavory, the logic presumed. Seeking not to rouse an increasingly vocal environmental lobby, the German auto makers agreed no vehicle would be permitted to exceed 155 mph – despite ever more powerful engines with the capability to generate considerably higher velocities.


cheers

 

I'm an Englishman but have the relevant local knowledge.

The XK8/XKR is electronically limited to 155 mph although during development Jaguar tested unrestricted examples to 178 mph at the Nardo test facility in Italy.

This arbitrary figure (155 mph / 250 kph) originated as part of a “gentleman’s agreement” hammered out in the 1970’s, when Germany’s Green Party wanted to impose speed limits on de-restricted autobahns.

Mercedes, BMW, Audi in Germany and Jaguar in the UK all agreed to limit their products’ top speed to 155mph.

Ferrari and Porsche were the first to break the agreement and others soon followed.

Graham

 

Let me add a little info for the US side. Unless you can get into your cars computer and tell it to set the speed limit to ROW (Rest Of World) the old girl is limited to 130 MPH.
Can't remember where I read this and it was years ago when I would have given it a go.

Wayne

 

In my "younger" years I had my '64 xke coupe up to 135 mph beating the pants off a Porsche 911. Let off the gas as the transmission was whining too much for me. My '91 XJS would top out around 150 mph. It was fun to let "ricers" pass on the interstate then catch them, pass them and then slow down to let them know who the big cats where.
Please do not share with my insurance company!!

 

Fastest I've went in my car is 120mph, but really the fun is the acceleration.

 

We Open road race and have a few 1000 miles above 150 and I can say with certainty than an XK8, even unrestricted, does not have enough HP to run 170mph.

An XKR should be able to top out around there, but an XK8 is going to need more HP.

When you get above 150 mph, to accelerate to the next 10 mph takes an an increasingly larger amount of HP, and an XK8 doesn't have much extra to spare at that speed.

 

Fastest I've ever gone was 130 in a '87 Porsche 924S. Top speed was published at 134. Car was very stable.