2004 IS300 Sportcross (USDM): Alignment Specs Advice

[Rajen]

Hello Everyone,

Hope you're all well. This seems like a very neat forum. I stumbled here over from USA IS forums while reading through alignment threads. Sorry that my first post here is to ask for help, but now that I'm aware of this forum I'm looking forward to future contribution.

Same as most, I've recently experienced the dreaded front inner tire/tyre wear, and, as a result, decided on a front-end refresh. Luckily, the rear seems to be doing well. Prior to wear I was able to get about 20k miles out of the existing tires before things quickly went south. I would appreciate alignment spec suggestions based on the following information.

Vehicle: 2004 IS300 Sportcross (USDM). Second owner and we're going strong at 203K miles on the clock =).

Location: Florida--mostly flat grid-style streets with about 65% highway and 35% city driving.

Weather: Mostly hot lol...with two season--dry and wet =).

Intentions: Spirited commute without breaking any laws or comprising the safety of anyone with/around me.

Tires: New Kumho Ecsta PA51 (would meet my needs just fine)

Wheels: OEM Stagger with 10mm wider cross-section.

• Front: 17x7 225/45
• Rear: 17x7.5 235/45

Ride Height: Lowered on Tein Flez Z coilovers with a 1-finger gap between fender and tire.

Parts replaced due to premature tire wear (a few other parts were also changed while at it lol) :

• FUCA - SerialNine Sport Version

• FLCA Bushing #1 - SuperPro via FIGS

• Caster Bushing #2 - SuperPro via FIGS

• Ball Joints - Mevotech (oem type)

• Inner and Outer Tie Rods - Mevotech (oem type)

• Roll Center Adjusters 17mm - FIGS

• Steering Rack Bushings - FIGS Solid

• Swaybars - Eibach

• Endlinks Front & Rear- FIGS Solid

• Endlink Relocation Brackets - FIGS

• Front Strut Tower Bar - Cusco

• Rear Strut Tower Bar - ExoticSpeed

When items need replacing I try to upgrade where makes sense. Little splurges are sometimes rolled into the overall expense lol.

Much thanks in advance!

Best regards,

Rajen

[Tony]

Hi Rajen and welcome to the wim forum.

Thanks for the in-depth information.

LOC UK contacted me 10yrs ago due to members ongoing inner front tyre wear. After research on some members' cars i found the reason, which have been widely used thereafter.

The problem is the castor position, which is too low and not adjustable directly.

I found by moving the castor position to -10' it will greatly displace the toe angle, when the toe is corrected it indirectly increases the castor.

The camber and caster control how much the camber will lean on a bend. The OEM castor allows to much lean.

So  a target of-10' minutes front camber with increased castor has proven to stop the tyre wear.

All other angles should be set to the OEM positions.

Important

The caster my go into the red, so out of the Lexus tolerances, this is fine.

Increment of measurement is 60' to a degree not 100'

Many shops don't measure the castor saying it's not adjustable, It's critical it's measured.

Feel free to ask any questions.

[Rajen]

On 05/06/2021 at 05:00, Tony said:

...

The problem is the castor position, which is too low and not adjustable directly.

I found by moving the castor position to -10' it will greatly displace the toe angle, when the toe is corrected it indirectly increases the castor.

The camber and caster control how much the camber will lean on a bend. The OEM castor allows to much lean.

So  a target of-10' minutes front camber with increased castor has proven to stop the tyre wear.

All other angles should be set to the OEM positions.

Important

The caster my go into the red, so out of the Lexus tolerances, this is fine.

Increment of measurement is 60' to a degree not 100'

Many shops don't measure the castor saying it's not adjustable, It's critical it's measured.

Feel free to ask any questions.

Hello Tony!

Thank you so much for your reply. Apologies for not responding sooner...took me a little while to ruminate on your advise in-between a hectic schedule. From reading back on the forum I see that you've been active all these years; even assisting those from various other countries. Thank you for your dedication to the community.

It's interesting to see how dynamic alignment can vary greatly from the static settings while everything articulates. You did mention a couple of things I would like clarification on:

1. You mentioned the caster position is "too low", meaning it's too positive?
2. You also mentioned, "Increment of measurement is 60' to a degree not 100'..."
   • Isn't 60' = 1 degree?
   • As long as Camber and Toe remain where desired, proceed to the next caster increment?

 

Considering all of this information I would like to summarize:

• Camber:  -10' (negative 0.167 decimal degrees)
• Caster:  I'm still not clear here...are you suggesting -10' (from your example) to +60' (max increment) (neg 0.167 to pos 1.0)?
  • My aftermarket front upper a-arm (link) adjusts camber using the two heim joints. I assume if one heim joint was adjusted more than the other, then caster can be dialed in as well.
• Toe: Remain within oem spec.

I know it's a lot, but thank you for walking through this probably for the n-th time--greatly appreciate it.

[Tony]

A few questions there.... Is the front upper arms adjustable, It's really important if we can use the upper arms rather than the lower camber adjusters.

[Rajen]

Yes, the front upper control arm is an adjustable aftermarket a-arm. There are two adjustable heim joints, one at each end, that attach to the body of the car, and can be adjusted while installed on the vehicle. 

[Tony]

Problem solved... The arms will allow camber and caster adjustment.

[Rajen]

6 hours ago, Tony said:

Problem solved... The arms will allow camber and caster adjustment.

Perfect. Based on this information, would you feel comfortable suggesting more concrete values for camber, caster and toe? Caster being the most crucial. I appreciate your assistance thus far. Please pm/dm if you wish to share privately. Thank you!

[Tony]

The entire positions depends on how much camber the rear has?.... You can't set the front until the rear values max out.

Put it this way you cannot set the front if the combined values at the rear aren't positions to balance the whole geometry.

Example we set cars for the drift BDC and EDC and we need to dial in an unstable balance. Front -3 degrees of camber, rear zero camber. This allows the cars to drift.

Toe and caster i cannot display because the cars are in competition.