Lexus is200 geometry/tracking/wheel alignment

[Adzzz]

Hi everyone, I just joined but I’ve been taking valuable  information from this forum for over a year since I’ve owned my is200. 

The geometry legend Tony Bones from wheels in motion has passed away late feb 2022. 

From my understanding he helped a lot of Lexus is200/300/sc owners in the Uk and globally to correct their Geo. 

I was trying to locate Tony last week  as I was finally ready to book an appointment and finally get mine sorted, but the business has since changed hands, I am also not even sure if it’s the same staff that Tony trained up. 

I wanted to know if anyone has the geometry numbers/print out from a car Tony/wheels in motion worked on? 

Not a sports model and no modifications. My car is a standard 2004 automatic. 

Or or if anyone can recommend a good place to get the geometry sorted. I’m based just outside east London. 

Thanks 

 

 

[TigerFish]

Can’t help with a printout, but that is sad news indeed regarding Tony. I’d been there a couple of times with my GS’s in the past.

RIP Tony 🙁

[Adzzz]

The IS200/ 300/ SC issue is the castor position? In it's natural position it's unremarkable and not directly adjustable but it can be adjusted indirectly..... Here's where it gets a bit dirty? The problem we have is front camber migration. The actual listed camber positions are very low -21' stock, -30 sport so nothing to drastic there but the low castor and camber migration during yaw, or lock shall we say allows the outer wheel to lean to far negative. I wrote a new front camber position that during adjustment violates the toe which in turn when corrected moves the castor...... Point to note is no cars steering pivotal points are at right angles so any adjustment/ correction will be reflected. I found a front camber target of -10' allows enough toe displacement that when corrected moves the castor indirectly forward ( positive ) by 30'-40' minutes.

 

The camber's static position of -10' is still within the Lexus tolerance range so no problem there but!!! The castor position will probably go outside of the Lexus tolerance range ( positive ) and be displayed as red on the computer screen and printout, that's not a problem, in fact that's what we want.

As just said most places won't measure the Lexus castor position because it's not adjustable, problem number one..... Understanding the interaction between the camber/ castor/ Ackermann angle ( TOOT ) = Toe-Out-On-Turns and the lock angle surpasses toe and go so the real problem gets missed, problem number two.

As said i found moving the front camber position to -10' will murder the front toe position toward ( positive ) The toe correction is in a safe direction since the steering arms are screwed in the end not out. Ok your going to loose some lock angle so now your 3 point turn will be a 3.5 turn.

On the Lexus the toe's pivotal point is aft of the lower ball joint meaning it's correction will pull toward the front control arm and it's this perpendicular correction that indirectly moves the castor positive. Then the interaction between the castor/ camber and Ackermann during yaw has changed.

I know this must all read ???? but it's why the Lexus has issues and remember the manufactures OEM settings are nothing more than a "SUGGESTION", they are not the law!

This is going to read way more complicated than it needs to be.....

Most tyre shops will say the wear is a comber issue but it's not?

The problem is the front caster position. It's too low?

To explain the front camber and castor have a marriage. When the steering is turned each camber angle migrates, this means for example on a left turn the inner wheels camber lifts and the outer wheels camber drops. 

The problem you have is the rate of the drop is dictated by the castor position. There other factors going on but let's stick with solution.

The front castor is not adjustable "directly" but it is indirectly?..... Moving the front camber too -10' will massively displace the toe angle.... Correcting this will indirectly increase the castor. The position will violate the Lexus datum which is fine since they got it wrong.

The tech working on the car might be very alarmed on the toe displacement but the correction is in a safe direction, meaning the tie-rods are adjusted in not out.

REAR
Camber: 55’ Negative

Toe: 6’ Positive (partial)

Thrust: 0. Or as near to but no more than 5’

FRONT
Camber: 10 to 15’ Negative

Castor: 6 Degrees Positive if possible + - 30’ 

KPI/ SJI: even +- 30’
Included angle: - not relevant (unless uneven by more than 45’)
Toe: 4’ Positive (partial)

The castor position might exceed 6 degrees and turn red on the screen/ print, that's not a problem.

Quote
Tony
Posted March 31, 2015

 

these are the geo numbers by Tony bones, for a is200 on standard suspension and 17” alloys. 

[Adzzz]

Further in depth information 

The IS has the ability to handle very well but historically possesses an unstable chassis in particular the front camber positions.

As the camber creeps toward the negative it also reduces the castor angle which is vital for high speed stability. Here is an explanation taken from wim-web.

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

Tilt State Phenomena

In the chapter dealing with the camber angle of the wheels, it can be seen that the camber angle varies according to the positioning or length of the steering arms under the effect of the compression and release of the suspension,

This effect is very useful when steering around bends, when the centrifugal force deforming the parallelograms formed by the suspension units gives the outer wheel on a bend a negative camber and the inner wheel a positive camber,

The same result is obtained on the wheels with the castor angle, but this is generated on the basis of the steering width and the vertical movement of the suspension arms, so the following conclusions can be drawn: when the wheel turns about a kingpin with a positive caster angle, if it is in the outer position on a bend it will take on a negative camber that increases with the strength of the steering action, and will thus act against the overturning of the vehicle, if on the other hand, it is in the inner position on the bend it will take on a positive camber which follows and assists the turn,

Consequently, when the vehicle takes a wide bend (small steering action) at a very high speed, it will be the same centrifugal force which, by acting on the deformability of the suspension parallelograms, will create the advantageous position for the wheels: however, when the bend taken is very tight (strong steering action) and the speed is moderate, it will be the castor angle that will create the advantageous wheel camber angle,

Other factors influencing the castor angle, low-pressure tyres, in modern vehicles, contribute to reducing the castor angle given to the kingpin during construction, in fact, when under the influence of active or braking thrust, the tyres deform and tend to increase the longitudinal offset by shifting their point of contact with the ground,

The castor angle also varies with the variation in the weight distribution of the vehicle, If the load is shifted to the rear axis this will increase the positive castor angle, and if it is shifted to the front axis it will decrease it,

True vertical Kingpin axis extension

Theoretical pivot point

Trail distance

Longitudinal castor angle/ set as positive, the kingpin axis falls in front of the theoretical pivot point generating the trail distance, this gyroscopic affect guarantees stability, and can be defined as the castor angle.

 

[Adzzz]

[WC12OOT]

I can vouch for Joe who has remained at Blackboots post take-over by Pro-Tyre. Call the centre and ask for him. I have personally seen Joe and Tony work together in the past so cant see there being any issues with continuity. W