Is200/300/sc Front Inner Tyre Wear

[Tony-Bones]

What's the symptom's

Front inner tyre wear involving about 10% of the total tyre width

What's wrong?

This bit's tricky to explain so stick with me.... The front camber position suggested for the IS200/300/SC is unremarkable but the pattern of wear is definitely camber related since the wear is so confined.

So!!

We found out the Lexus IS200/300/SC has three different Castor positions around the globe, Asia, Europe and GB but the Castor on the IS is a fixed angle?

What's Castor?

Outside of KPI/SAI "steering axis inclination" Castor is one of the most difficult angles to explain since it doesn't really exist? It's a position born from the steering upper and lower pivotal points, in all modern cars the lower pivotal point is forward from the upper, this is called positive Castor.

Duties

During a turn there are many geometric complexities going on that involve the Castor, the one that concerns us is the Camber migration?

Migration

As said the IS200/300/SC has unremarkable front static Camber positions, yet has historic Camber tyre wear and there's three Castor positions around the globe despite the fact the Castor is not an adjustable angle, so what's going on? The IS front static Camber position looks like this / \, during a left turn the angles, thanks to the Castor and other unmentionables migrates to this \ \, the problem we have in the UK with a low Castor angle is the outside wheel leans over to far during this hypothetical left turn.

Summary

Lexus UK are well aware of the problem but because the solution would be a "part replacement" they never excepted this since it is a build issue, other manufacturers offer new build solutions for the field geometrically as and when problems evolve, normally this is nothing more then new target position replacing those that simply don't work.

Solution

The steer axis pick up points are not made or positioned at right angles so it's possible to influence one angle by adjusting another... Several years ago i researched this possibility for this club using some donor cars.

Conclusion

A small change in the front OEM camber positions dramatically displaces the Toe position, correcting the Toe indirectly moves the Castor forward.. Simple.

My thoughts

A despicable situation that Lexus deny by claiming this a trait of the car "utter bollox". No manufacturer designs a car to wear front tyres to the wire in 5k, anyway you now have an explanation and actual data can be found in this clubs knowledge base

[iceman67]

the doctor makes it look easy well done tony for the detailed report :winky:

[Tony-Bones]

Your welcome.....

It's been a while since i've been here but i'm getting a steady flow of "help emails" recently so i thought i would bring this to the table again to help members.

[stevie_]

thankyou mate, very useful! all negated by fitting coilovers with very much visible camber though lol :D

i think this topic should be made a sticky and duplicated for all IS and altezza boards....

[Dave1986]

Tony can u PM me some prices and locations please?

Basically im looking to have all my geometry set up, my front tyres have wear on the insides, iv just replaced the rears, i drive an Altezza on coilovers if that makes any diffrence, im waaay up in Scotland so im in for a bit of a drive lol

[Tony-Bones]

Tony can u PM me some prices and locations please?

Basically im looking to have all my geometry set up, my front tyres have wear on the insides, iv just replaced the rears, i drive an Altezza on coilovers if that makes any diffrence, im waaay up in Scotland so im in for a bit of a drive lol

These are the partner centres we have around the UK http://www.wheels-inmotion.co.uk/tyre-fitting-centres.php

[Mossyn]

Nice to see you back on Tony.

My Lex is still going great guns after your magic fix....... Thanks again.

You may remember me............ I nearly set your new workshop on fire when my LED lights decided to ....AH.... go into fault mode!!!

Take Care

Mossy

[Tony-Bones]

Nice to see you back on Tony.

My Lex is still going great guns after your magic fix....... Thanks again.

You may remember me............ I nearly set your new workshop on fire when my LED lights decided to ....AH.... go into fault mode!!!

Take Care

Mossy

Good stuff, i'm pleased all's still well, oh and i remember the car very well!!

[Russell-H]

Hi Tony,

I have an IS300 that is scrubbing the front inners a bit, is it possible to fix this myself ?

One of our offices is in a MOT centre and they have wheel alignment equipment that they would allow us to use, what would i need to tell the guy to do different to what would be in his book of settings ?

I can not remember the name of the machine but it des do about 16 measurements i belive.

Kind regards

Russell.

[simonlexus]

hey whats the difference between Laser Tracking @ Newport & Cardiff branches

and 4-Wheel 3D Alignment @ Cwmbran branch , thanks (Both are Discount Tyres) http://www.discount-tyres.co.uk/

[MacRS200]

Know that this is a old thread but only just read it cos not been on here for a long time!

Only taken me 7 years but finally I understand :-)