tires causing pulsing

[76 cadillac bob]

Cadillac Bob Here, I have brand new Cooper P235/75R15 Trendsetter se, MS tires. Here is what is going on
I drive the freeway for 15 miles, 65-70, wobble at 70 for sure probably balance, I had front end checked and bushings replaced; nothing at 65 smooth as can be.
I get off freeway, park for an hour and take surface streets home.
Whole car pulses as though brakes are being applied with a warped rotor, but I am driving 35-45 no braking.
Speedometer also wiggles in unison with car, and it is the whole car not front or rear end.
I leave it overnight, no wiggle no jiggle no pulsing, runs great on city streets all day.
I suspect tires?  Old tires that were 8 years old never did this.
I have heard things about Cooper Tires, not my choice, my tire person got them for me.
CB

[Dan LeBlanc]

Sounds like the tires may be going out of round when hot?

If you had a tire shop that could spin them up after a drive on a balancer without the shield in place, you would likely see the wheel hop.

[TJ Hopland]

Are you sure you don't have a brake issue?   Could be something like a failing hose keeping some pressure at the wheels.   Overnight it bleeds down and things are normal for a while.    If they are dragging enough to cause that much of a vibration there should be some signs of heat. 

[The Tassie Devil(le)]

I suspect tires?  Old tires that were 8 years old never did this.   

I too would suspect the replacement tyres.

Bruce.

[The Tassie Devil(le)]

I purchased a set of tyres of a reputable brand, and it was the worst decision I made.   Couldn't replace them till they were worn out, as I couldn't afford to, but it was like driving on a surface of jelly.

As soon as they were worn out, went back to a better brand and boy, what a difference.

Bruce.

[Jon S]

Cadillac Bob Here, I have brand new Cooper P235/75R15 Trendsetter se, MS tires. Here is what is going on
I drive the freeway for 15 miles, 65-70, wobble at 70 for sure probably balance, I had front end checked and bushings replaced; nothing at 65 smooth as can be.
I get off freeway, park for an hour and take surface streets home.
Whole car pulses as though brakes are being applied with a warped rotor, but I am driving 35-45 no braking.
Speedometer also wiggles in unison with car, and it is the whole car not front or rear end.
I leave it overnight, no wiggle no jiggle no pulsing, runs great on city streets all day.
I suspect tires?  Old tires that were 8 years old never did this.
I have heard things about Cooper Tires, not my choice, my tire person got them for me.
CB

What year/model Cadillac?

[TJ Hopland]

Some of you have had tires that act like his?   Bad tires is possible but how can they fix themselves sometimes? 

[Tpicks55]

My son witnessed  some testing on tires for all vendors.  He was setting up the machine that runs the testing of tires.  He told me there are three grades of tires.  1. perfect condition tires which go to the car manufactures and retailers of high end tires.  2.  Normal tires which we get at the local tire retailers.  These are of good grade but may have some small issues but still good tires.  3rd are the tires which may have issues in the tread or build up and are sold to discount houses and walmart.  I guess  you get what you pay for.  Just fyi

[Scot Minesinger]

Proper tires are a start.  Given your handle it must be a 76 Cadillac, is it RWD or FWD?  FWD are very intolerant of imperfect tires.  If it is an Eldorado buy the very best quality tire available.  Also get a proper mount and balance.  In our area the quality of tire mount and balance was so bad, bought my own machines.  Your rims could be bad.  Probably tires, very difficult to diagnose over the internet

[76 cadillac bob]

I have a 1976 eldo front wheel drive, 5300lbs of metal. Unique front end. In this year, split CV and one of a kind rims. Tires do need to be balanced, I confirmed with my dealer, long story.
Will try that if not will explore other options.
CB

[Scot Minesinger]

76 Cadillac Bob,

The short answer is probably the tires, rims or tire balance need replacement/attention/corrective work.  Impossible to really diagnose over the internet.

Got a double whammy here in crowded Washington DC area - lying is a way of life for many and there are not enough businesses so that basically they can survive on no repeat customers.  Normal stuff like mounting and balancing tires is done by the least talented labor with no ethics, to be kind.  I'm in the construction field, and I can always tell when someone is lying - they won't write it down.  Dealer says...

Anyway, it is not difficult to get the 1976 Cadillac to drive beautifully:

1.  Tires must be top quality, under 6 years old.  Probably have to buy Diamondback radials or Vogue, the standard cheap brands are no good.

2.  Rims must be in perfect condition, the 67-76 (maybe up to 85) are easy to bend and get out of round.

3.  The tires must be properly balanced, this includes two stages, the tire balance machine before adding any weights measures and tells you if the tire is not mounted with respect to the lightest part of tire on heaviest part of rim, and often the tire has to be removed and rotated say 60 degrees radially before it goes back on the balancer and weights applied.  Weight may be required to be added to front or back of rim, you can't add the old style to just back so hub cap fits on OK, and as an aside the correct offset weights need to be installed.

4.  The hub caps or wheel covers need to be balanced.  The spun stainless steel ones are generally fine, but have seen the spoke and turbine style create balance problems - you can quickly find this out with a ride down the highway with no wheel covers.

5.  The suspension generally will not create a vibration, but maybe a pull or something, but in any case the suspension must be in top repair, the upper suspension bushings, tie rod end bushings seem to be the first to go.

6.  The front drive shaft system and brakes must be in top repair.

One of these six has got to do it.  Have not worked on a lot of 67-76 Front drive Eldorados, but every one I did had the same issue as you and in every case it was tire, tire balance, or rim issue related - not to bad to cure.

It would have been great to spare myself the 7k it took to buy that tire mount and balance set up (and they are used), but there was just no way to get a good job consistently here locally.  Around the rest of the Country and especially in more rural areas the quality of professional work on automobiles is astoundingly better than here in DC.  Hope my rant on DC was not too much for you,

Scot

[TJ Hopland]

If you are looking for rims 69-78 Eldo Toro should be good.  66 toro 67-68 eldo toro there were apparently some wheels that don't clear the 69+ disc brakes.   79-85 won't fit, they were an overall scaled down wheel including the bolt pattern.