Castor way off

[emirc 0]

My right castor is off with 1

[dr_mat 0]

Replace the wishbones (and their bushes). Also there's a small amount of movement possible by shifting the position of the three bolts holding the bottom ball joint in place.

Bear in mind that 1 deg of castor is about 1 inch of movement at the BJ.

It's highly unlikely that the chassis is twisted.

[emirc 0]

Wishbones looked relatively OK last time i checked, no visible damage/bending, no serious rust, etc. However I will replace them soon i guess... Forgot to mention i already replaced complete tie rods. Should i go genuine VAG item, or..?

 

Roads are utterly poor here and it's my daily drive. Sometimes when i'm in the rush just don't have a time to avoid some potholes. Combine that with a non-marked speed bumps that are most of a time invisible, and you just hear them (when it's too late of course)!

Should i let them do 4 wheel alignment with me at a driver's seat next time?

[Lufbramatt 0]

theres no way at all of adjusting castor angle on a corrado, the setting on the ball joint will allow the camber to be changed but not the castor. Only way that it could be wrong is that a rubber bush (wishbone or top mount) has failed or something is bent (subframe, wishbone or shell)

 

camber can be adjusted with either the hub to strut bolts or the balljoint to wishbone setting.

 

Do you definately mean castor? ie the angle between a straight line (through the ball joint and the top mount) and vertical, when veiwed from the side of the car?

 

or camber- the amount the wheels lean inwards when veiwed from the front of the car?

[emirc 0]

I mean Castor. Ideally it should be +3

[dr_mat 0]

The rear axle can be twisted easily, particularly if it's ever been off the car, so ignore the placing of the REAR wheels when computing caster. Caster should be calculated using the amount of lean on the front wheels when steering lock is applied - and ONLY that. The rear axle mounts with bolts in slots to allow alignment, or plain moving it backwards and forwards.

If you drop a plumb line from where the centre of the top mount sits, you should be able to measure ~3 inches BACK to where the bottom ball joint line is. It's not easy to see this though.

If your steering was consistent I'd say you should worry about the caster angle, but since you say it feels inconsistent there must be something moving about .. and chances are that's the wishbone bushes.

[Kevin Bacon 5]

Yes. Castor must be identical on both wheels or you'll get the pulling problems as you've described. The steering might feel a bit weird too, slightly heavier turning right?

 

You're correct, castor is fixed to 3 degrees, + / - 0.25 on the Corrado. Agreed with Lubrafmatt, Castor that far off suggests problems! I would recheck the top mounts and rear wishbone bushes.

[emirc 0]

The rear axle can be twisted easily, particularly if it's ever been off the car, so ignore the placing of the REAR wheels when computing caster. Caster should be calculated using the amount of lean on the front wheels when steering lock is applied - and ONLY that.

 

Mat, what do you exactly mean by "steering lock"?

 

Yes. Castor must be identical on both wheels or you'll get the pulling problems as you've described. The steering might feel a bit weird too, slightly heavier turning right?

I would recheck the top mounts and rear wishbone bushes.

 

I rechecked them week ago, i then changed top mount bearing just to be sure... I'm positive bushes and mounts are all right. No clunking or squeaking or anything like that.

You are correct Kev, steering does feel heavier turning right! First i thought steering rack gave up, but when i checked alignment and castor then... Other of that, steering isn't so bad actually, it's precise and predictable around the bends, just have to add more right input to compensate for left pull, even little more on the WOT :grin:

Also did balancing of the wheels while i was there, and check this out: front right rim was slightly more deformed, it actually wobbled very little while you watched it rolling on the balancing machine. Thought it's normal, but asked them to switch wheels front-rear just to be sure it wasn't problem in the bent rim. Nothing changed. I'm affraid i hit something hard with my right side (oh-er!), hard enough to bend something on the whishbone-subframe-shell line just what Lufbramatt was pointing out, but isn't obvious to a naked eye...

Is it also possible to be a differential?

 

Cheers.

[boost monkey 0]

Replace the wishbones (and their bushes). Also there's a small amount of movement possible by shifting the position of the three bolts holding the bottom ball joint in place.

 

That's a bit of a grey area; Bentley explicitly states that those 3 bolts should be tightened in the dead centre of the holes and not used to adjust ANY suspension geometry.

 

Anyone else heard anything different?

[dr_mat 0]

Well anything bolted into slotted holes has room for movement, but it's a tiny amount and everyone always says "don't do it".

 

The laser alignment rigs calculate the castor angle when you've put 20 deg of steering angle on. (i.e. turned the wheels!) They look at the difference in "camber" between when the wheels are straight ahead and at 20 degrees and that difference allows you to calculate the castor angle. Any reference made to the rear suspension is just to gauge the thrust line.

 

Of course, the only way to *accurately* measure castor therefore is to set camber and toe *accurately* before you start, and given that you can't adjust caster, most places never re-check it after doing the camber/toe so the readouts you get are not very accurate.

[was8v 0]

I'd still gamble wishbone bushes if you have no record of replacement.

 

Stick the handbrake on and have someone balance the clutch. Watch how much the front wheels mve forwards in the arches!

 

My right wishbone rear bush was shot (clunking) and the left looked fine, doing the test above and the wheels moved a fair way!!!!

 

Replacing both wishbones complete with new bushes led to there being almost no movement.

 

My car measured quite a difference in centre of rear wheel to centre of front wheel ont he left side as to the right side. Now they are within a couple of mm.

 

The cars handling is transformed - I thought it was good before! lol.

[emirc 0]

Bushes are replaced all around as i wrote before, checked them approximately a month ago, used solid OEM TT/R32 rear wishbone bushes and everything else VR6 standard. Ball joints and tie rod ends have no play at all.

I'll try that test over the weekend though...

 

P.S Also forgot to mention that i have intermittent stuttering while steering. Strangely, it never happens when the car is cold, only when heats up a little. It's also more or less pronounced depending on road bumpiness/elevations. It's noticeable only when car is slowly driven, somehow it's not that obvious when driving faster. Feels almost as like power steering doesn't work - it's harder to steer and you can actually hear short pop!-pop!-pop!'s while slowly turning a steering wheel. My first thought was logical, knackered top mounts, but replaced them as i wrote before, and nothing changed at all... Actually i think it got worse! Must look into it too over the weekend i guess...