[Straight eight]

Do you have cupping of the rear tires? Other than rotating front to rear every 4,000 miles or so, are there any other cures?

[BJM]

The 85 Riviera has an independent rear suspension requiring a proper four wheel alignment. Be careful and take it to a trusted mechanic or else they will only adjust the front suspension angles.

Not 100% sure what you mean by cupping as that has several meanings but there are 2-3 adjustments that can be made on the back of the Riviera, toe, camber and maybe caster.

The suspension probably has adjusting bolts seized or hard to loosen and adjust. Therefore, lubricating every visible suspension fasterner back there well in advance of the alignment would be good for you.

Mechanics get paid about 1 hour for an "alignment" but this can mean many things. We were trained to "set the toe and collect the dough" meaning if we could "align" it in 15 minutes, we got paid for one hour.

Most of the cars I did required 4 wheel alignments. I took a different outlook and took my time in doing all four wheels and still made some money.

This sounds horrible but is not. Do you want a rookie doctor replacing your knee and it takes 4 hours or a do you want an experienced surgeon taking half that time?

On the other hand, this can create abuses. If the mechanic gets underneath there and sees rusted adjustment cams, they can fudge the front end numbers to bring the car inot alignment - long enough for you to leave.

You should tell the service advisor ahead of time you will want the print out of the alignment results. This should show an alignment correction to within tolerances.

The issue comes with the rusted / seized rear fasteners needed to be limber in order to do the alignment. A time limit places a burden on the mechanic and a suspect mechanic could cut corners. Since you specifically noted the rear tire as the issue, the adjustments need to made back there.

Make it clear to the service advisor that you want the issue fixed. You want proof of the fix and may even want to talk to the mechanic.

[RivNut]

In my experience, cupped rear tires on any FWD vehicle usually meant that the rear shocks were worn. Instead of putting the tire back on the ground and holding it there, the worn shocks will let the tire dribble down the road.

Is your leveling system still functioning or have you perhaps changed to some aftermarket non-air shocks?

Is the cupping uniform across the entire width of the tread or just on one edge? Is it the same for both tires?

Ed

[sosuzguy]

I have also noticed the rear wheels at an angle too because they were adjusted with a leaking ELC system. Basically adjusted with no air in the system, then you get in the car driving it and it's inflated and not aligned right.

[Straight eight]

Thanks guys for the help. When I bought the car with 14,000 miles on it the previous owner warned me to be careful who aligned the wheels, as few techs understand the system. This had the effect of my just not getting an alignment. I'm at thirty thousand now with uneven, sort of cupping on the outer edge of the rear tires only. The tires have about 6,000 on them now.

[tim63riv]

Because of the rear suspension design of the 79 to 85 GM "E" body cars, they are very sensitive to rear wheel toe-in adjustments, and that is what is causing the cupping of the rear tires.
Most reputable alignment shops will only do a four wheel alignment on vehicles that have four wheel independant suspension like your Riviera. The trick can be to find those places! Most GM dealers would be able to handle the alignment as well as a good quality independant garage, but look for one of those that specializes in alignments if possible.
After the alignment, rotate the tires in an "H" pattern (front to back, back to front) every 2500 miles and you won't have any further issues with the tire cupping.
Good Luck!
Tim

[Straight eight]

Has anybody got a copy of the shop manual suspension pages? It is the only section missing in my 85 Riviera manual. I would like to read how the air suspension works, and how often the pump should come on. Tests for proper operations would be helpful too. If someone has, and would like to email them, I sure would appreciate it.

[sosuzguy]

Straight Eight, I have the ELC section scanned already and will email to to you.

[sosuzguy]

Straight Eight, your email address isn't working.

[Straight eight]

Thanks for the copy