Why does Jaguar understate performance specs?
 

According to Jaguar, the 5.0 XKR has a zero to 60 time of 4.6 seconds. But on the zeroto60times.com website, performance is listed as 3.9 seconds zero to 60 and 12.1 seconds in the quarter mile. Anybody know what the reasoning would be for understating performance?

I'm only guessing but it could be for insurance purposes. There may be governmental regulations at play also? I know the American Muscle car builders played the insurance game in the 60's.

Because nothing sucks worse then getting caught exaggerating claims.

Yup, get caught overstating regulated specifications and the manufacturer can be fined for each unit produced. I remember it happening to Ford on the Mustang years ago.

There are a lot of factors in 0-60, tire temp, road traction, air temp, humidity, quality of fuel, etc.

Then there is over time detrimental performance from build up and variance between units when new.

Magazines report what they find, the manufacturer reports what they consider to be the least flattering end of a likely tolerance variable.

Yep, R+T's '07 XKR tester only got 13 mpg but was tons of fun...

Traction seems to be the biggest issue with the 5 litre. My best standing quarter when the car was stock was 12.533 and that only dropped slightly to 12.521 with the XKR-S tune even though the terminal speed was 2.77 mph higher.

I also struggle to do 0-60's in much under 5 seconds so I am trying to wear out my Dunlop Sport Maxx's as quickly as possible so that I can get some PS4S's!

This is going to vary by climate/storage conditions, I find grip fall off on summer tires for my car is noticeable after about 20 months.

I can only see dates on two of my tyres and they are both from 2014 so that might be part of what the issue is.

Pretty much everyone makes a good tire that is a major player on the market, it is for the most part different compromises of priorities.

It has amused me reading reviews on tires to see people complain of their OEM tire, and how much gripper their new tire they switched to was when I have had both tires new, and while there was a difference in feel and ride, the grip was about the same.

A tire that sees less sun exposure, and is not in temperature extremes will have longer lasting tires.

My tires get a lot of sun exposure, and there is also a wide range of operating temperature. The fall off will vary.

I would take manufacture 0-60 & 1/4 mile times with a grain of salt

The true representation of how quick a vehicle is (1/4 mile , 0-60mph) can only be taken seriously once measured at a drag strip.

Drag strips are slippery as all get out unless you have slicks. You want to feel true performance, go find some freshly laid concrete on a straight stretch of road. There's a bridge over the Lillypons estate in Frederick County, MD that's a legendary street race spot. Bridge is @ 1/4 mile of 2 lane concrete and launching from a stand still is way, way more spectacular versus the drag strip where you are peddling to get off the line clean. I felt the seat back flexing on my Mustang it was so violent. Never felt it before or after.