[kevster]

Mornin' all
After fitting my new wishbone bushes I took the car in to have the wheel alignment check....not jsut because of the new bushes but also because it was wearing excessive tread off the inside driver side tyre and also the steering wheel had to be turned slightly left for the car to go in a straight line. After re setting the wheel alignment the steering wheel is now straight, but I noticed that the left-to-right toe in/toe out measurement was not the same. The guy doing the work said that it is not possible for most cars to be set perfectly at all wheels and that it was the front-to-back wheel alignment that was the important one. He also showed me that the gap between the driver side wheel and the rear of its wheel arch was wider than the same gap on the passenger side wheel. There was no sign of a prang looking at the joints, seams, subframe alignment and panels under the car.

Is this normal? Am I going to have problems if I want to fit wider tyres?

I do wonder sometimes if these places have all their figures correct. He went round all the wheels first and checked the tyre pressures (which I was glad to see) and set them all to 30psi (which I wasn't so sure about). My user maunal quotes tyre pressures as about 34 to 36 psi, where as his wall chart shows 30psi. Which is correct?

Cheers
Kev

 

[PHudson]

Originally posted by kevster:
[qb]Mornin' all
set them all to 30psi (which I wasn't so sure about).  My user maunal quotes tyre pressures as about 34 to 36 psi, where as his wall chart shows 30psi.  Which is correct?

[/qb][/b]

From memory, the back of my user manual has them as 30psi (unless fully loaded at high speed) for my 15" wheels...

 

[kevster]

Doh...sorry, forgot to say they are 205 55R16s on a 1993 aero.
Kev

 

[sj]

For my MY95 9000, the manual showed 35psi for 205/55R16. I ran my tyres at this, assuming the book couldn't be wrong, but I wore the centres out of the treadband. I was using 7 1/2" rims though. I found that about 30 worked well for my particular setup.

I suppose the main thing in terms of alignment is that he set all the pressures the same so that there was no (avoidable) distortion of the measurements.

 

[kevster]

I'm assuming that my alloys are the original aero standards (they are certianly corroded enough) and so I think are 6.5 inch? My tyre wear is much greater on the edges than the centre, so I don't think I can have been over inflating at 36psi, although the wear pattern could be a reflection on my driving

The alignment thing is a separate issue I think. Still worries me that front to back is ok, but side to side is well out . It suggests that one of the fron wheels is slightly ahead of the other, which also appears to be the case with repect to the wheel arches, and a possible problem with rubbing on one of the wheels if I decide to try 225/50R16s
Kev

 

[saabz2000]

It sounds like your man is not fully versed in suspension/wheel alignment procedure. The first thing to do is get the "toe-out-on-turns" correct for both directions. this needs to be done on special plates that have degree markings on them. The idea is that the inside wheel of the turn has to turn more than the outer wheel to provide true rolling. If someone has adjusted 1 track rod all the way in and the other all the way out, this will balls things up completely. This must be done before and after your man gets out his beaten up old dunlop tracking guages!!

alternatively take your car somewhere that has a laser tracker and tell them to IGNORE steering wheel position, because it is probably wrong.

virtually nowhere knows how to track a car correctly, and there is no way to do it properly without the right gear.

Dave

 

[kevster]

Hi Dave
He was using a four-wheel laser alignment system. Basically it gave a line running either in line with the wheels (front to back) or at 90 degrees to the wheels (side to side). He aligned the front to back no problem. But any adjustment to try to bring the side to side alignment into line would have screwed the front to back up. The result is a car that seems to run nice and true, and all the wheels are atleast trying to go the same way, but one front wheel is slightly ahead of the other .

Should I take it to another garage and see what they come up with? I'm not sure how much can be adjusted as just looking down the line of the wheels it is possible to see that the wheels are roughly in line, but it is also clear that there is less gap behind the driver side front wheel than the passenger side front wheel

Hope I dont have a car that has been bent in the past

 

[saabz2000]

all wheels in line is great when going in a straight line, but when you turn the inner wheel must turn more. Did he adjust both track rods while ignoring the position of the steering wheel, or did he centre the steering wheel and adjust it off that????

 

[kevster]

He centered the steering wheel and then locked into position with some kind of clamp, he then checked the tyre pressures, he then mounted the lasers on each wheel and turned them on. He then adjusted the alignment of the front wheels such that each one was off set by the same amount relative to the targets on the rear wheels. I presume there is not much else he could do as the alignment of the rear wheels is not adjustable (I assume) and I'm not sure if you can adjust any other form of miss alignment of the front wheels???
Kev

 

[carrera]

If one front wheel is in front of the other, then assuming the chassis is straight and the same components are fitted left / right, then this would tell me that the problem is in the front wheel castor settings.

This "may" be felt when allowing the steering wheel to return to the straight ahead position after cornnering.

Is that even adjustable on a Saab ???

 

[9000CS23T]

Originally posted by kevster:
[qb]He centered the steering wheel and then  locked into position with some kind of clamp, he then checked the tyre pressures, he then mounted the lasers on each wheel and turned them on. He then adjusted the alignment of the front wheels such that each one was off set by the same amount relative to the targets on the rear wheels. I presume there is not much else he could do as the alignment of the rear wheels is not adjustable (I assume) and I'm not sure if you can adjust any other form of miss alignment of the front wheels???
Kev [/qb][/b]

This method is correct for 4 wheel alignment. You check pressures, put the lasers on with the wheel set straight. Then you check the measurement. You need to set the marks on the rear the same on each side, this ensures that the car is running straight, then you adjust the front equally each side to get the Toe right. Ensuring that the rears are still equal. On the fronts you add the measurements from each side to ensure that you are within the tolerances given for the Toe. If everything is right you tighten the track rod lock nuts back up and test drive to ensure it drives true.

To set the toe out on turns accurately you need more accurate setting gear which measures the castor and camber etc. Merc garages use this set up and it takes an hour to check and adjust the settings.

 

[saabz2000]

Ok, what he has done is the cardinal sin in alignment. If the steering wheel has been removed and refitted a few splines out, then he has just buggered up your entire steering angles!! If you can imagine that someone has would 1 track rod all the way in, and the other one all the way out, not only will the steering wheel be pissed, but you affect the amount of lock in each direction that can be achived by each wheel.

It is all very well setting the wheels straight to the back wheels, but that is only part of the whole picture.

 

[kevster]

Now I really don't know what is going on Do I need to find myself a Saab dealer to check this properly, or even a Merc' dealer. I'll be a bit pi**ed if I end up having to insist on my money back from the current people.

 

[sgould]

When the Saab steering is set up correctly do you get the same number of turns each way to full lock? Can someone confirm this?

 

[9000CS23T]

Things are getting blown well out of proportion here! As long as you have an equal number of turns each way there is no cardinal sin committed. From what you put down, kevster, the tracking has been adjusted properly.

 

[carrera]

Yes, but even if the tracking is correct I still think wheel castor is out.

 

[kevster]

Yeh..I'm starting to think there is something else well out . If the wheel alighnment is correct but one wheeel is ahead of the other can I corect his by loosening the subframe bolts, trying to shift the whole right hand side forward ( the side that is currently trailing), tightneing up and having it re aligned....or am I looking at a trip to the main dealer for a re jig' and alignment of the whole chassis?

Or.....(financially much easier), live with it and forget the fat wheels?

Kev

 

[saabz2000]

Originally posted by Neil(CS2.3T):
[qb]Things are getting blown well out of proportion here! As long as you have an equal number of turns each way there is no cardinal sin committed. From what you put down, kevster, the tracking has been adjusted properly. [/qb][/b]

and what percentage of a turn is supposed to be measurable??? With all due respect, i was trained by professionals at great lengths over 2 years about all things cars... And i personally paid a lot of attention to the geometry side of things. After all, a car that does not drive straight when expected, is really no good to anybody!
It is really very simple, and i quote from geometry section of the steering/front assy device from the Saab 9000 service manual :

Turn the steering wheel to the left until the right hand( outer) wheel is at 20 degrees. If the steering angle is correct, the inner wheel should be at an angle of 21 degrees +/- 0.5.

Ther are normally only 2 main reasons for this to be wrong.... somebody has bu99ered up the lock by winding 1 track rod all the way in, and the other all the way out. OR, and this seems likely.... seeing as the 'setback' (difference in distance between the front and back wheels) differs from side to side. You probably have a bent steering swivel member ( wishbone ).

 

[saabz2000]

just found this website with some nice piccys that might help....... see what it says about Ackerman angles. Also read right at the bottom in bold red where it says that the track rods must be the same length, and that the steering must be centred ( thats STEERING, not steering wheel!!!!!)

http://www.uk-hotrods.co.uk/technical/tech...ng/steering.htm

 

[carrera]

Originally posted by saabz2000:
[qb]Ther are normally only 2 main reasons for this to be wrong.... somebody has bu99ered up the lock by winding 1 track rod all the way in, and the other all the way out. OR, and this seems likely.... seeing as the 'setback' (difference in distance between the front and back wheels) differs from side to side. You probably have a bent steering swivel member ( wishbone ). [/qb][/b]

I would tend to agree with that.... except that Kevster starts off his post by saying he has just had new wishbones fitted.

, I doubt they would be bent from the factory, but perhaps they are not the correct parts that have been fitted ?