Lexus Technical Articles
Altezza / IS200 / IS300 suspension lowering and recovery research results.
By Tony Bones of Wheels In Motion
Feb 27, 2008 - 11:49:56 AM

Altezza/IS200 suspension lowering and recovery research results.

• Donor car SXE10 owner Neil MacDonald aka member MacRS200
• Results also relevant to the IS200/300
• The car: W index Altezza tyre size 215-45/17 fitted with Apexi N1 V coil-overs
• The use: Road only

• The objective: Observe the natural reach for the Geometry adjusters whilst lowering the vehicle in progressive increments, allow settling of the chassis then lower the vehicle and recover the Geometry. 
  

• History: Neil MacDonald kindly agreed to this research realising the end results could be of value to LOC, WIM and himself. The duration was 18 months and 30 thousand recorded miles. 
  

The initial measurement with stock suspention showed the normal discrepancies, and was recovered to stock geometry positions other than the front camber/ castor which adopted the wim positions of

Front camber: -20’

Castor: + 5degrees 55’

Observations showed the usual inner front tyre wear, and all adjusters were still available for future geometry corrections. 

Stage two -30mm

The figures displayed are the after correction positions.

What was evident was the loss of castor. Although the IS does not have direct castor adjusters, the angle can be adjusted indirectly via the camber correction. Also there is a need to retain a near equal disparity between the positions or the car will pull toward the lower value.

The rear cambers initial position was near to 1 degree 10’ after the lowering but we had a problem? Unfortunately there is a design flaw with the near side rear toe adjuster that effects 2 in 10 cars, the adjusted is basically a captive off-set D cam, like the image below.

When the cam is rotated it requires a constructed ledge to push against enabling the movement, on some cars this ledge is to shallow allowing the cam to ride over it denying any movement. So what now?

It is feasible to adjust the rear toe, again indirectly, in this particular cars case it was a necessity since the toe was resting Negative (toe out) and definitely not desirable for a rear wheel drive car unless Drifting is you past time. Using the pivotal action of the camber we lowered the position to -1 degree 58’ and achieved a 0 toe position. 

Stage three -35mm

The figures displayed are the after correction position.

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This time the front camber adjusters were near to the maximum adjustment range. It was decided that since now the dynamic camber curve is denied by the lower suspension and the fact the castor position is so high we would leave the balance and monitor the tyre wear. I personally thought the balance front and rear was complementary. The rear positions were totally compliant and adopted a natural positive toe in position. 

Stage four -50mm

The figures displayed are the after correction position.

The front camber adjusters were now exhausted. The camber/ castor ‘over the axel’ disparities showed no real concern. What was interesting was the rear toe had moved positive (toe in) since I was unable to use the toe adjuster directly on the near side rear I was able to recover some of the deep negative camber to correct the toe position much to our relief. Since these positions were effectively the done deal the next stage was to monitor the consequences regarding the expected tyre wear…How much?...How fast? 

Stage 5 -50mm re-check

The figures displayed are the final position 

This final check concludes our research. Neil was a little naughty with this one leaving the re-check for some 6K. The Geometry now was totally settled, a need to manipulate the off-side rear camber to enable the toe to comply was necessary but after 6K this was a small price to pay. The tyre wear pattern mimicked the Geometry positions exactly and Neil decided to replace the long serving tyres happy with the wear rate. 

Summery

The analysis taken from the Altezza SXE10 is also relevant to the IS200/300 suggests a safe natural Geometry recovery is possible from a -35mm suspension drop and will still allow for future adjustment to compensate for the cars normal chassis displacement over time.

What was also noted was that the -50mm was not without consequence but the reduction significantly changed the dynamics minimizing the damage born from lowered suspension. It is true to say that if you are aware the tyres will suffer reasonable loss then -50mm may well be desired or indeed welcomed by some members. 

Wim is unreservedly grateful to Neil MacDonald aka MacRS200 for his participation in this project, the information born over 18 months and 30K is unique and the results volunteered to LOC. On a sub note I decided not to display the mileage intervals since this could be considered as literal. This could be dangerous since our relationship monitoring these results required constant communication, this may not be available everywhere.