greetings,
My 1999 XK8 upon hitting puddles can swerve violently. I have had the car for a couple of years and not noted this before. No problems on previous MOTs and new tyres all around. That being said I have not driven it in bad wet weather before. The wheel bearing have been replaced and everything else is standard. The mileage is only 73000. Is this a trait of the car or is there a problem. I have searched the forum but not found any similar problems. The speed I have noted this happen is between 50 and 60 as I dont drive fast in wet weather.
Cheers

 

It. Sounds as if the car started to hydroplane, loss of friction between the tires and pavement. The new tires may not be channeling the water as well as your pervious tires. Jim

 

I have the same issue with my car, so much so that I will not drive it in the rain. The next time I have to buy tires I'm getting tires designed for higher performance in the rain. Currently I have Continentals, I don't know which model as they were bought by the previous owner. They are very good on dry pavement but terrible on wet roads.


Mark

 

The condition is somewhat obscure and relatively new because it does not apply to fixed live axle rear suspensions. It took a lot of searching to find the cause and solution after a particularly scary drive on slush over black ice on the highway. The little gem was finally located in a single thread on a automotive board in Canada ... the home of winter slush. This led to refining search terms to find more information. Most of it came from northern areas with a lot of snow. But, still not a lot of hits.

On a live rear axle the tires point straight ahead at all times ... provided the axle has not been bent or twisted.

However, on a independent rear suspension with adjustment provisions this is not usually true. There is usually some toe-in on the rear suspension. This toe-in or even worse, toe-out, will tend to push the rear end from side to side when the tire grip is not even in low traction situations. Each tire is fighting the other to be in the natural straight ahead position. If one gets the upper hand, the other is in worse position and will fight harder to get to straight ahead. The wobbles in the rear is the result of being a witness to the ebb and flow of the fight.

The solution is to set the rear toe-in to zero or just a hair in and exactly equal on both sides. Never toe out ... at least on Jaguars.

Doing the above requires either very careful DIY, or a custom four wheel alignment. "in spec" is not good enough as the spec is quite wide. I chose diy.

 

Same thing happens to me here in heavy rain and puddles on the road. I put the Jag away before slush and snow can affect driving.

 

@Plums

Good info !!!


Do you have some tips for a diy ?

 

Never had that issue with mine, I have Michelin Pilots which I wouldn't recommend for spirited driving but fine in the rain. I store the Jag in winter. What tire are you running? Did you have it aligned? Plums might be on to something.

 

I think Plums is onto something as well; good info/points.

But.....

I'm not quite sure that Plums' discussion addresses the condition described by the OP: rear end wobble when driving on low traction surfaces -versus- violent swerving when hitting a puddle of water

Cheers
DD

 

Hi Fulton, might be that yours is just "**** on" and set to zero where most others are " out " just that little bit?
Great detective work Plums, that's another cut and paste info sheet, cheers M8.

 

Gentlemen,
Thank you for your responses. It appears that I am not the only XK owner with this problem which I had not come across in my research before committing to buy an XK8. Many thanks to Plums for the concise explanation of cause and effect, and others for why some Jaguars suffer and some do not. And why some tyres are good in the wet and not great in the dry. As I dont want to drive a fair weather car only, I will try to get the rear wheels toe in/out settings to zero or slightly less as recommended. Many thanks for your help and advice

 

The diy alignment has been in progress for a loooong time.

In a past post when the rear toe-in was done, I posted some details about the interaction between rear camber and toe-in as well as the expected change for "x" fractional turn of the adjusting cam. It would be in either General Tech Help or X308.

Using a laser level, you can get resolution below 0.10 degrees decimal because the straight beam of the laser can extend the measurement to great distances. There are a number of DIY articles on this on various forums.

The reason for DIY is that it eliminates a middleman who might decide that close enough is good enough.

 

For the OP's problem, the front can also be a factor if cross caster or cross camber are off, and also toe-out.

Toe-out is used by some racers to aid in initial turn-in, but the cost is instability on straights. For a driver that is aware of his own setup, this is managable when paying 100 percent attention to the task. On a street car, it is suicide.

If it were moi, I would start with baselining all four wheels with a custom alignment. By that, I mean an alignment to a particular set of numbers rather than the usual "check if in spec". Due to the spec range, a Jaguar can be "in spec" and still exhibit squirrelly handling.

A car that is acceptable cruising at highway speeds in the dry can be a nightmare in low traction conditions because under dry conditions holding the wheel straight ahead is sufficient. But, in low traction conditions, any imbalance in the way the car wants to track naturally is going to come out and smack someone in the side of the head.

 

Please post the results one way or the other. There is not a lot of information out there on this behaviour.

If this gets to you before your alignment is performed, make sure you specify to the shop that you want before and after printouts. This way, if commentary is needed, you can post the printouts.

 

One last thing ...

zero or close to zero toe-in also benefits tire wear.

So the alignment can pay for itself

And contary to conventional belief, once you get an alignment you like, don't change it. Alignment seldom changes unless you curb a wheel hard. So it is cost effective to get one great alignment and then leave it alone.

 

I have Michelin Pilots and can say I never experienced a loss of control yet.

 

I had the same pull when hitting a puddle with over an inch of water with Pirelli P-zeros. Doing nothing but changing to Hankook V-12 I have no pulling in the same conditions.

 

I finally had my mechanic look at the car with a view to adjusting the rear toe in/out adjustments to solve the sudden swerving in the very wet situations. Seemed timely to get it done with the MOT. He advises because of the set up on the Jaguar rear suspension there is no adjustment possible. and only the front can be adjusted for toe in/out. This will be done in a couple of weeks. I will report the effects of the adjustment. But I had noted bad wear on the outside of both front tyres for "ahem" two years because I had never checked the tyre pressures since buying the car 2 years ago!

 

Rubish. The Rear Toe is adjustable with a Cam Setting on the Rear of the lower Pivot Pin behind the Rear Wheel.

 

1) might as well cancel the appointment and book with another shop that is familiar with Jaguar alignments

2) you never revealed the bad tire wear ... that would not be helping your situation.

 

Gentlemen, Thank you for your comments. The tyre wear was not noticed as I incorrectly assumed that the new tyres on the front would have been inflated correctly and with only driving less that 3000 miles a year with that particular car would not have worn. My mistake. I will pass your input to another specialist whom can make the necessary adjustments for all wheels. I will report back the findings. Many thanks again for your input