Bump-steer. A GS300 from Germany

[Tony]

This owner has had dire bump-steer issues and contacted wim. I asked him to replace the steering damper and have the Geometry measured, which he did but not without consequence....

Here is the latest email.

 

.................................................

Hi Tony, well after 4 weeks I have finally driven the Lexus to Berlin!

 

If you have a few hours the story unfolds thus.............

 

With only getting back to the UK every other weekend it took some sorting.

I booked it in for a geometry check but decided to have a play before hand

and having marked the positions I adjusted them from one extreme to the

other - made no difference, still bad bump steer.

So I set it back and left it to the garage to set - I've attached the

printout.

The following weekend home I picked it up and no change - they suspect the

steering rack is buggered. So I ordered a new one from a breaker - £105, not

too bad. I had noticed there's a bolt hanging down off the passenger side on

the track rod end of the tie arm and I guessed there should be a damper of

some sort fitted. Now there happened to be a GS300 for sale in the local

dealer so I nipped down and had a look underneath - sure enough there's a

damper fitted running parallel to the rack. So I phoned a Lexus dealer to

see if mine should have one, yes they said and a new one is £280. Bugger

that, so I phoned the breaker again and made sure the rack came with the

damper too. By this time I'm back in Berlin so get the rack delivered direct

to the garage who fit it, but are having trouble getting the steering wheel

to be straight when the wheels are straight!

On my next trip home I take it for a test drive and it's no different -

still bump steers.

Back at the garage I get them to raise it up on their lift and once

underneath you instantly spot that the rack isn't parallel to the

crossmember - passenger side is low by about 20mm. But the wierd thing is

that the brackets seem correct and have been correctly fitted! Also, the

rack didn't have a damper because I'm now told 1996 models didn't have them

fitted ??????????? who is telling the truth I don't know. Anyway, I took the

car away and played with the bracket and by putting a 12mm nut as a spacer

between the bracket and the mounting lug on the subframe the rack is level

and hey - no bump steer. I took it back to the garage the next day and got

the tracking corrected again - job done, and drove the 940 miles from

cornwall to berlin yesterday!

 

Must say though that it's not as stable at high speeds as I though - not a

problem in the UK but out here on the unrestricted autobahns it wasn't as

planted as I thought it would be - but we are talking 130mph!!! seemed OK

upto 100-110 but seemed to suffer from instability when one wheel only hit a

bump. Could be that this will all be cured when I eventualy get the correct

mounting bracket - but finding the correct part is gonna be fun! Also, it

suffered from a lot of tyre roar - is that normal - or can I put it down to

the crap tyres fitted - BARUM on the front CONTINENTAL eco somethings on the

rears.

 

Other than that it drove over really nice - managed roughly 31mpg so quite

happy.

 

Anyway - I hope I haven't bored the pants off you too much - any advice

regarding the correct bracketry would be welcome.

 

Cheers

 

Steve

........................................

Here is the Geometry report.

 

 

Can you see any problems on the report.

[yemgi]

the individual toes front and rear. Left is negative and right is positive ?

[Tony]

the individual toes front and rear. Left is negative and right is positive ?

Certainly so in the initial readings. Here are my immediate concerns with this calibration.

1: Where are the after measurements.

2: Why is the nsf toe 12mm out and the osf 12mm in

3: Why is there such a disparity in the toe-out-on-turns

[Roger440]

the individual toes front and rear. Left is negative and right is positive ?

Certainly so in the initial readings. Here are my immediate concerns with this calibration.

1: Where are the after measurements.

2: Why is the nsf toe 12mm out and the osf 12mm in

3: Why is there such a disparity in the toe-out-on-turns

 

1. On the right hand side off the screen?

2, Cos some numpty didn't centre the rack when they fitted it? But centred the steering wheel during the alignment chack

3, See 2

 

Well thats my take on it. Interesting the stering coupling etc(ive no idea what it consists of) was unaffected by the racks incorrect location.

[jon]

What Roger said. The after figures are hidden on the right.

[Tony]

the individual toes front and rear. Left is negative and right is positive ?

Certainly so in the initial readings. Here are my immediate concerns with this calibration.

1: Where are the after measurements.

2: Why is the nsf toe 12mm out and the osf 12mm in

3: Why is there such a disparity in the toe-out-on-turns

 

1. On the right hand side off the screen?

2, Cos some numpty didn't centre the rack when they fitted it? But centred the steering wheel during the alignment chack

3, See 2

 

Well thats my take on it. Interesting the stering coupling etc(ive no idea what it consists of) was unaffected by the racks incorrect location.

Odd the image is so large... It's fine on my screen, maybe my resolution is wrong. The toe and toot positions are wrong due to the incorrect horizontal alignment of the steering arms. Rack behind the wheel. so a lower arm toe's in and higher toe's out. Although after adjustment the toot will still be incorrect. Also the radii of the steering arm and the wishbone would be incorrect, subjecting the car to bump-steer.