Steering wheel off centre a knats dick

[aceparts_com]

Just got my Porker back from a suspension alignment and the steering wheel is just sitting round to the left by a few degrees. Instead of taking it back on a 3 hour 150 mile round trip I was going to wind one track rod in and one out after carefully marking them by about 1/4 a turn.

Anyone see anything wrong with this? I don't want to upset the alignment but i'm 99% sure that this is all they did the last time

[Sam_68]

Should work ok, but since any KwikFit can check the tracking, why not get it re-checked afterwards just to be sure?

I wouldn't trust the fast fit centres for a full geo, but there's not much to go wrong with a simple tracking check?

[denisb]

No problem in adjusting it a little bit.

Adjust it off centre too much and the car will pull to one side.

[aceparts_com]

I spoke to the garage who did the alignment - they were happy to see it back and said that all they need to do is wind the track rod ends in/out one flat 1/6th of a turn.

Funny how whenever the car has been aligned it's always been slightly off to the left, never the right.

[jwb]

In theory adjusting the track rods like you suggest WILL alter the bump steer characteristics. It all depends on how good the suspension alignment was. Ideally, first you centre the rack and lock it in position. Then you adjust the wheels to the correct toe with reference to a vehicle centre line (or rectangle around the car). The track rods will then be the correct length. If you then adjust the trackrods a bit each side you move the rack pivots accross the car. This could put them in the incorrect position regarding bumpsteer. The steering arms are now running on different pivot point positions each side.

John

[Mr Whippy]

jwb said:

In theory adjusting the track rods like you suggest WILL alter the bump steer characteristics. It all depends on how good the suspension alignment was. Ideally, first you centre the rack and lock it in position. Then you adjust the wheels to the correct toe with reference to a vehicle centre line (or rectangle around the car). The track rods will then be the correct length. If you then adjust the trackrods a bit each side you move the rack pivots accross the car. This could put them in the incorrect position regarding bumpsteer. The steering arms are now running on different pivot point positions each side.

John

I asked a load of questions about this a while ago...

Seems that no one really knew how to find the "middle" of the rack easily.

What if you find the middle, adjust TRE's appropriately, then find the wheel is still out, and doesn't have enough notches to allow it to sit straight?

Starting to think the bump toe changes and ackerman and associated camber change with steer is irrelevant as long as both TRE's are "about" the same...

Would love to actually find an establishment who KNOWS what they are doing with regard to this.

Dave

[leorest]

Mr Whippy said:

Would love to actually find an establishment who KNOWS what they are doing with regard to this.

Chris Franklin is your man www.centergravity.co.uk/

[Sam_68]

jwb said:

In theory adjusting the track rods like you suggest WILL alter the bump steer characteristics.

But, of course, unless they have adjusted the rack height for bump steer all they will be doing by centring the steering wheel is re-setting the rack alignment to the correct factory setting. Assuming that Porsche aren't in the habit of building cars deliberately with off-centre steering wheels!

[jwb]

Mr Whippy said:

I asked a load of questions about this a while ago...

Seems that no one really knew how to find the "middle" of the rack easily.

What if you find the middle, adjust TRE's appropriately, then find the wheel is still out, and doesn't have enough notches to allow it to sit straight?

Starting to think the bump toe changes and ackerman and associated camber change with steer is irrelevant as long as both TRE's are "about" the same...

Would love to actually find an establishment who KNOWS what they are doing with regard to this.

Dave

Finding The Rack Center

In theory this is quite easy, in practice to get it accurate is harder. What you are interested in is the pivot centres at the end of the rack where the track rods attach. On my car I centred these to the lower suspension chassis pickup points, so I would have the same bump steer characteristics each side. However I also referenced my suspension to a chassis centreline. I have notes of the dimensions required to centre the rack plus this neat marker on my pinion....



This means I can return my rack to its centre position easily.

If your wheel is still out on a production car such as a Porsche I would guess your actual rack centring is incorrect or the car has been bent or the rack isnt bolted in correctly. The only way to get a straight wheel is to set it straight and then adjust the track rods to get the correct tracking and live with the results or adjust the bumpsteer at each side.

John

[aceparts_com]

OK, I've just been under the car and adjusted one track rod in and one out 1/6th of a turn in order to align the wheel (yet to be verified)

Anyway, the odd thing I noticed is that on one side, when I loosened the lock nut the track rod end became loose in the end of the rack damper (on a 993 the rack has a ball joint connected to a female threaded damper that the track rod end screws in to).
I could wobble the track rod end around slightly.


Should I be concerned or was the other end tight due to age/rust etc?

Edited by aceparts_com on Wednesday 4th October 23:05

[bales]

This is completely off topic but jwb, I remeber seeing your car at Formula Student 2005, were you a judge? I just looked at your profile and thought hang on i've seen that car before

[jwb]

aceparts_com said:

OK, I've just been under the car and adjusted one track rod in and one out 1/6th of a turn in order to align the wheel (yet to be verified)

Anyway, the odd thing I noticed is that on one side, when I loosened the lock nut the track rod end became loose in the end of the rack damper (on a 993 the rack has a ball joint connected to a female threaded damper that the track rod end screws in to).
I could wobble the track rod end around slightly.


Should I be concerned or was the other end tight due to age/rust etc?

I would not expect the track rod to be any looser than a normal bolt in a nut or threaded hole. That means there should not really me any noticable play. However if the threads are slightly worn as you describe it would still take a lot of force to pull the track rod end out. The risk is if the lock nut comes loose then the wear would accelerate.

I generally do not compromise on steering, at least if your brakes fail you can pick which tree you are going to hit, if your steering goes then..........


Bales.....Yes I was a judge at Formula Student in 2004 and 2005. I was very disappointed to miss it this year, hopefully I will be back in 2007.

Good luck in finding employment in motorsports.

John

[aceparts_com]

Right, i've adusted the track rods a sixth (one flat) of a turn each side and it now tracks straight and true.

I've noticed that the steering dampers (track rod is fitted to the rack with a rubber sleeve to reduce shock i guess) can allow the rack to move in and out 1-2mm without moving the track rods when stationary. I know the RS has less rubber between the parts and i've heard of people welding them up. What's the PH general view on welding them?

[aceparts_com]

Update (not sure if anyone's actually bothered but here goes); I welded the inner to the outer sleeve thus bypassing the rubber and lo and behold the vagueness around the straigh ahead and most importantly the constant drifting to the left has gone!

So after five suspension alignments I may have finally found a solution!