Slightly OT - steering the Buick
 

I visited a friend in Richmond, VA this weekend. He has 2 Buick LeSabres, an '89 with over 250K, & a 2000 with less than 10K.
He prefers to drive the old standby, because he says the new one wants to pull to the right on crowned roads, bad enough to produce a "tired arm." The new car has variable speed sensitive power steering, the old one, of course, could be steered with a pinkie. My guess was that at speed, the car's not getting the assist that the old one provided, thus becoming a beast to steer on certain roads. He did have the dealer do an allignment & rebalance all tires. No improvement. Does anyone know if there's way to "disconnect" the variable steering feature, or perhaps adjust the sensitivity? I drove over some of the same roads with the SVX & had no pulling problems. Any solutions out there?
Thanks as always, Ron.

Don't buy a Buick?

:D

The problem these days is that most cars don't allow for alignment adjustments. Front toe is always adjustable, but toe doesn't have any bearing on the car 'falling' down the crown. You would also be hard pressed to find a good alignment tech these days as most techs know how to set the toe and little else. Maybe that's a good thing.... :rolleyes:

First thing to do is to swap the front tires from side-to-side. Some radials will cause a 'lead' to one side. Normally the tire won't have any other problems. If that cures the problem - great! If not more than likely what he needs is a little more positive caster on the right front (or a little less on the left.) Not to worry, caster has no effect on tire wear (within reason.) But instead of trying to find someone that wants/knows how to accomplish that how about trying 5# less air in the left front (or 5# more in the right?) Less air in the LF will create just a slight bit of rolling resistance and help hold the car in place on a crown.

Trying to adjust the level of assist on a variable-assist rack is a pita, if even possible (depending on model) and still doesn't address the problem - the car will still follow the crown.

If he wants to pursue adjusting the caster the easiest way will be to shift the engine cradle. What he'll be looking for is about 1/2 -3/4 degree more positive caster on the right than the left. It really isn't as difficult as it sounds, but like I said, most guys doing alignments haven't a clue.

Beav

Thanks a bunch, Beav. I forwarded your response to my friend.
I still wonder though if the pulling is typical in speed sensitive power steering units, or if the adjustments would be necessary with ANY car. If we do adjusting to fight road crowns, what happens on flat roads?
Ron.

Everything you didn't ask for...
 

Speed sensitive steering is no more likely to pull than other systems. Uptown SVXs have speed sensitive steering and they don't exhibit the problem. Actually you'd be surprised how many cars do have the feature.

Fighting road crowns has always been the bane of alignment techs. Catch 22, damned if you do, etc. Typically a tech would figure on a 1/2 degree caster difference pushing left to counterract a 1 1/2" crown. But that's with rear wheel drive. Figure in unequal shaft lengths and drivetrain drag on fwd cars and you just play it by ear. I used to work in an area of Denver where most everyone drove the interstates to work. Imagine trying to explain to some hardheads how the dually ruts from large trucks didn't match the track width of their Honda. The car would be 'swimming' in the ruts and there's absolutely no way to make the car drive straight without constant corrections. Sorry, buy a Peterbilt... ;)

Quick primer on alignments: Three basic angles - camber, caster and toe. Camber is the tilt of the wheel in or out at the top - top of the wheel towards the car is negative and away from the car is positive. Camber pretty much stays constant in cars with strut suspension, and as such normally runs close to straight up or '0' degrees. Cars with unequal length 'A' arms have fairly dynamic camber, as the suspension moves up and down the camber changes quite a bit. Typically these cars will have 1/2 deg. positive camber. Think of camber in the terms of a Dixie cup on its side. It has two distinct diameters, and if pushed forward it will travel in a circle. If you force the cup straight ahead one diameter spins faster than the other. If a wheel has excessive camber the diameter differential comes into play and you can bet the tire will be ripped to shreds. Camber has little effect on pulling unless, obvously, it is so far from spec as to cause drag from the uneven tread diameters.

Caster is like the front wheel on a bicycle. Notice how the fork at the wheel is farther ahead than the handlebars? That's positive caster. On a car the wheel with the most positive caster will push harder towards the center of the car. More positive caster will also give more 'returnability' (steering wheel returning to center after a turn) and stability to the steering - to a point. Excessively positive caster can cause violent shaking in some vehicles. Older Chevy rwd pick-ups were notorious for it - a lot of miles + a poor alignment + 45mph + a big pothole and it was off to the races. Hopefully you didn't have manual steering with your thumbs inside the steering wheel. The only way to stop the shaking was to stop the truck (which you had to do in order to change your laundry anyway.) It's not the only vehicle to do it, but it was probably the most common. You would never forget the experience, the fenders jumping up and down, the steering wheel constantly whipping back and forth 3/4 of a turn and the noise of the truck beating itself to death. Whew!

Well, to get back on track ;) toe or 'toe-in' is how the wheels sit, pigeon-toed or duck-footed. Toe is absolutely the most critical adjustment, the most easily knocked out of alignment and the biggest cause of tire wear, next to underinflation. Toe on most cars is critical to .125". For rwd cars the toe is usually set 'in', because as the car drives forward the tires will drag back and 'out', to a parallel position. With fwd cars the toe is usually 'out' and the wheels pull 'in' as a result of power application. However that's not a hard and fast rule anymore, different geometry, bushings, etc. will cause some fwd cars to be set 'in' also. Basically the thing to watch for is tire wear on the inside or outside of the tires. If the wear is equally placed on both tires it's more than likely toe, if only on one tire or inside of one, outside of the other it's probably camber. Incorrect toe will cause wear on the leading edge of the tires - excessive toe-out will wear the inside edge of the tires and vice-versa.

There's a lot of other considerations, but those are the basics. Sorry for the looong post, but I needed something to do while waiting for sleep mode to kick in... :)

Beav

Wow, Beav, get some sleep! Thanks again for chapter II. I promise to buy the complete book when it hits the stands. LAST QUESTION - What would you do if the car was yours? (Besides trying the side to side swap & other stuff suggested in chapter I). Take it to an alignment specialist, & send the dealer the bill (if it's fixed)? Sell the car & buy another '89 Buick or a '92 SVX? Remember, this is a virtually new garage queen with no abuse the owner admits to.
Most humbly yours, Ron

How about all of the above? Actually I'd pass on the second Buick... ;) Swapping the tires will probably cure the problem, if not go to a reputable alignment shop. Good luck and fat chance on getting the dealer to pay for it though. Alignment on that car should go $50 - $100, depending on how much time is spent correcting caster, if needed.

Beav

OK Beav, I've forwarded all your recommendations to the proud Buick owner. Let's see what happens. Can I... I mean can my friend buy you a beer? OK.. two beers. (Ya' gotta come to Lafayette to collect).
Gracias, Ron.

No problemo. I may take you up on the beers, I kinda like to meet everyone. My schedule is more of a last minute thing though, I'll do my best...

Beav

OK - We'll see you at the last minute. Coronas with a twist you say?
Muy bien! Ron.

Beav - one more "last question" (THREE coronas comin' up)
Re: the side to side swap. This was considered a radial tire no-no. Is this another urban myth? My friend says he's raised tire pressure a few pounds to no avail. Hmmm...
Ronaldo.

It used to be a no-no years ago on domestic tires. They had a problem getting the rubber to stick to the steel cords. It's been o.k. to swap them since the 80's.

Beavario