[xj-s] Very Rough Ride At Certain Speeds

Hi All,

My 84 has a very bumpy ride. It just sort of lopes along, making me
feel and look as though I’m on horseback when puttering along in so-
called ‘‘rush hour’’ traffic. It seems to smooth out at certain
speeds, while riding rough at others. It may ride silky smooth at
70, 90, and 110, while being rough as a buckboard at 60, 80, and
100. The ride is so harsh at some speeds that images in the center
rear view mirror blur from the vibration, while the reflections in
the two outer mirrors are clear, and steady. The car has done this
since I’ve owned it, dispite having the wheels balanced recently.
The Michelin X-One tires have good tread, and I see no obvious
defects such as unusual wear patterns, or sidewall buldges. I’ve
also noticed a tendancy for the car to follow grooves in the road.
Thanks in advance for advice.

Scott–
84XJ-S(JagZilla)ported heads,Flowmaster/Monza exhaust
Brandon, Mississippi, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

// please trim quoted text to context only

Hi All,> My 84 has a very bumpy ride. It just sort of lopes along, making
me
feel and look as though I’m on horseback when puttering along in so-
called ‘‘rush hour’’ traffic. It seems to smooth out at certain speeds,

Scott, I’m not totally clear if you are describing the ride or the way it
is running. This could be a wacky idea, but have you considered the
throttle potentiometer? I’ve never experienced a bad one, but I know they
act up at varying throttle positions Possibly enough to throw the timing
off enough to cause missing? Be interested in knowing the outcome.
Dale,
92XJS V12 Coupe

// please trim quoted text to context only----- Original Message -----
From: “JagZilla” thundercat1984@yahoo.com

In reply to a message from a51 sent Thu 18 Sep 2003:

It’s not engine related. During slow driving, the engine is purring
like a kitten, albeit, a very loud kitten (compliments of a
freeflowing exhaust). In fact, at speeds around 5mph, you can time
the rhythm of the inbalance (for lack of a better word) to about
one tire rotation, which would be several hundred crankshaft
rotations.
Yesterday evening, I had my wife drive by me very slowly several
times while I watched the wheels from various angles. I never saw
anything suspicious, and she stated that she did’nt feel the rough
ride. That made me wonder if the condition only rears it’s ugly
head after things warm up (grease, wheel bearings, air in tires,
shock oil, etc.). As I drove the car to work this morning, I
noticed that the ride was smooth at all speeds for the first
several miles. It was only after 5 miles or so that I started
detecting the ride quality deteriorating.
I’ll watch the car roll again this evening, only this time I’ll
make sure everything is up to temp. Any ideas what this could be?–
84XJ-S(JagZilla)ported heads,Flowmaster/Monza exhaust
Brandon, Mississippi, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

// please trim quoted text to context only

In fact, at speeds around
5mph, you can time
the rhythm of the inbalance (for lack of a better
word) to about
one tire rotation,

I think you have the beginning of tire belt
seperation. If you can switch tires/wheels with known
good ones you can confirm this. Another, but more
difficult, test is to spin the tire/wheel while
observing the tread directly on. If the tread has a
weaving track or a squirm the belt is shifting. If
jacking up the car and doing this please use jack
stands.

If it is a tire(s) with belt seperation eventually
(soon) it will go flat.

HTH

Geoff— JagZilla thundercat1984@yahoo.com wrote:


Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com

// please trim quoted text to context only

In reply to a message from JagZilla sent Wed 17 Sep 2003:

Scott,
You are describing eactly the same symptoms my XJ40 exhibited.
Started as a slight wobble about once per tire rotation and only
when I reached about 30 mph or so. As Geoff suggested to you,
someone suggested to me that the tire interior was probably
starting to separate. I discounted that as the tires looked good
to me, so I started imagining problems with ball joints, drive
shafts, even transmission mounts. It got so bad after a month or
so I stopped driving the car; it felt like I was riding the end of
an aligator’s tail and was being snapped left and right. When I
finally took the tires off I was shocked at how deformed the right
rear had become. Once the car’s weight was off it, I could see it
was looking more like an oval than a circle. New tires, no wobble.
I’m still embarressed that I didn’t listen when I was told it was
my tires the first time. If you can get your car up on a lift you
may be able to spot the offender once the weight is off it.
Otherwise, try moving the fronts to the rear and see if the
‘‘roughness’’ moves with them. Good luck! Let us know how you make
out.–
John - '90 Majestic, '95 XJ-S 6.0 Conv., '86 Volvo 760T
Stamford, CT, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

// please trim quoted text to context only