"For all of the 'doubters,' please stay stock... I really don't give a ***** !"


Not sure why you would write that, pretty unprofessional for a guy that works on quarter million dollar cars all day long, but logic dictates that if you change the track width of a vehicle SIGNIFICANTLY (as you said), regardless of the unsprung weight, it will affect the behavior of the vehicle, don't need to be a mechanical engineer.

 

Unprofessional?

How about when someone asks your "Professional Opinion," than goes out & does the opposite of your advice: then they have the gall to complain to you about it? Happens all the time.

I'm not directing this at you personally: I'm just sick of the time wasters... the reality is that not everyone can afford our product (well, actually, very few people can), and that's okay with me.

BTW, unsprung weight makes a BIG difference. I'll install my 19x9 +37 and 19x10 +37 wheels and 245/35zr19 + 275/30zr19 Toyo T1-S, and post feedback on the forum ASAP! No worries...

 

SoCalSC4;

That is a subjective statement made by the driver (yourself in this case), going from +50mm to +37mm offset must have an effect on the SC steering, as you know the scrub radius cannot be altered by this positive amount (+13mm) without increasing the torque applied by the road/tyre relationship into the steering.

Changes/reduction in unsprung weight will have a great effect on the suspension (anything that changes the suspension characteristics of the front suspension must alter the steering to some degree), but unsprung weight has much less effect on steering than widening the front track or extending positive scrub radius.

Whether or not you find this "adverse" is in your determination. I am happy with the more weighted steering, quicker turn-in and increased feedback from +35mm offset, others may think it is way too lively (specially for a Lexus), what we might consider to be good, positive steering feedback, some would think it was "darty" or "unsettled".

Fitting shallow offset rims to the front of the SC will effect the steering/handling, it's not a right/wrong thing, it's whether or not you will like the result, extending the track by 25+mm is more likely to be found on a race circuit saloon car (UK saloon car circuits are twisty), I am not sure the average driver is prepared for this difference and that’s why I advise anyone to stick as close as possible to the factory spec for front offset.

 

Precisely Bill, thx.

 

Okay, you guys are entitled to your opinions...

But if you're looking to fit a wider/stickier tire, isn't the goal higher performance in handling and braking? Futhermore, is it realistic to expect to use (for example) an 8.5" wheel with a +50 offset? How many wheel manufacturers can even build such a wheel?This will certainly contact the front suspension upright.

So you're stuck with an 8.0" wide +50 front wheel, which has a maximum allowable tire width of, say, 235... 10mm wider than factory.

Wow... you might as well stay stock. Enjoy your 225/55-16s.

Also, if you're comparing a touring-type OE 225/55-16 tire (tuned for quiet & smooth ride and high mileage), it's pretty difficult to get a fair comparison of road feel to, for instance, a +2, 245/40-18 tire. I've driven on all types of high-performance tires, and I can tell you some are more prone to tramlining than others, and some become more prone to tramlining as they wear. We're not comparing apples to apples...

Perhaps a true 'enthusiast driver' isn't as bothered by slight changes in camber, caster, scrub radius, etc. (I'm not saying they are not SENSITIVE to it), but he/she takes it in stride and compensates- automatically. A good feeling chassis doesn't bother me a bit: in fact, I prefer it.

So for the naysayers, worriers, and conservatives, fine: stay stock. I'll be the guy driving my modified car on Mullholland Drive with a giant grin on his face!

 

I've been trying to stay out of this but the above quote egged me on.
I think that Bill is on the money when he says this is a highly subjective issue. I went to a +38 offset and I hate that I have to grip the steering wheel tightly in order to remain in control of my SC. My buddy Frank on the other hand loves the new feel because to him it feels like a "sports car". Well, when you have a tractor trailer roaring at you and you're fighting to keep from darting in front of it, that changes things. It's not about being an enthusiast or driving down Mulholland drive. That's an arrogance filled crock. It boils down to personal preference. Some are not going to put their health at risk just so they can call themselves an enthusiast.

 

Webb, right on the money, no denying that an SC with a +38 offset behaves drastically different than with a deeper offset. SoCal, no one here was talking about comparing to the stock 225-55-16 in any way, shape, or form, you're the only one to bring that up. We're talking about offset here, and IMO I don't like the effect such a large change in track width has on this vehicle, and I AM an enthusiast, believe me, i've built up 25-plus cars/bikes, I have the timeslips to prove it, and the skills to use it. As everyone else has said, this offset thing is simply a matter of personal preference, but you can't deny that there is a measureable effect. If we can simply agree on that I can get back to my Eldridge...
JonJon

 

I'll agree with you Lex...

I did some degree of testing with some different combinations of wheels and tires on my car to address the tramlining and the pulling left and right on crowned roads (especially bad under braking)

The problem originated with 17x8 40mm offset wheels and Dunlop SP5000s. I decided to swap the 17x8 50mm wheels from our GS400. The GS400 has Michelin XGTZ4s. Both are same size 235/45/17. Although the tires aren't identical, they're close in terms of construction/indended use, etc. With the swap, the GS400 with the 40mm offset exhibited some of this same darty behavior. The SC300 was tamed of the tendancy somewhat with the 17x8 50mm. It still didn't track as well as the GS400 with the 17x8 50mm setup. I think the GS400 was designed from the start for wider 17 inch wheels and engineers left out some steering feel in compensation for no kickback from the wheel. I can feel this difference between the two cars--- The SC300 lets more road feel through.

I tried one other combo: 18x8.5 45mm on Bridgestone 740s(?). This combination was actually less darty (but far noisier) than the 17x8 40mm setup. The ride on the 18s was actually better than the Dunlop SP5000s and comparable to the Michelins.

I checked 100s of feedback reports from the Tire Rack on all three of these tires and there are no notes of tramlining or dartiness on any of them.

 

Lex: what do 1/4 mile times have to do with steering feel or offset? I guess I missed that Engineering lecture...

SC300T: offset difference or not, you simply cannot make a fair comparison with two different brands of tires. Period. The Michelins and the Dunlops you tried are worlds apart in tread design & rubber compounding. Also, if your car is pulling hard to the left (especially on a crowned road), you've got other issues, dude. Warped rotors? Sticky caliper? I dunno...
I can assure you, Lexus did not 'deaden' the steering feel of the newer GS: in fact, many people have complained of too much feedback-, this is usually related to wheel/tire imbalance or non-hubcentric wheels (though many have had issues with OE wheel/tire set-ups).

hoops: Risking your health? C'mon... you can get killed walkin' your doggie. If your car is that darty, you've got other alignment or suspension issues. Check your tire pressures lately?

This thread should be moved to "Suspension and Handling"

 

A +38 offset will make the SC darty and it WILL want to torque the steering wheel out of your hand if you brake hard on rough pavement, that's what hoops and SC300T are referring to and it DOES happen, you have three people here who have experienced it, and I do think it can be unsafe. No warped rotors, sticky calipers, or suspension or alignment issues. Quarter mile times have nothing to do with steering feel or offset, I never said they did, and to be honest, i'm trying to be patient, but you just love to put words in my mouth. If you still won't admit that this condition exists, it's OK, but the math doesn't lie chief. It is possible people other than you know what they're talking about
- Jon

 

Putting words in your mouth? Jesus, man, you're talking about "having the timeslips to prove it." Whatever...

Yes. I'll agree the scrub radius changes- with a sophisticated suspension like the Lexus, camber & caster change is minimal throughout the travel. It's not like we're talking about a '65 Nova here. So, we have three people who have experienced it: I can tell you, we build over 1500 sets of wheels per year, and I have not even had ONE comment about dartiness or tracking issues.

In my experience, the effects of offset charges on these cars have not been objectionable. My opinion of "feel" IS subjective (so is yours), but I've probably driven more cars than 98% of the population, so I feel my opinion is derived from real-world data, and has value.

This is not to say you guys didn't experience a change in feel, but I don't like it when guys run around basically saying "well, I did this or that and it sucked, so nobody else should do it or they will be sorry."
I've seen numerous posts from a few of you guys saying (in effect) "well, you can do that 17x8 +xx, but your car will get squirrely on you." I think this is a real disservice to the CL members if it isn't accomanied by some sort of explanation... scare tactics suck, chief.

 

SoCalSC4;

Fact: Altering the scrub radius will effect the steering on the SC.
Subjective: This is either a good or bad thing.
Advice: Dont do it unless you are aware of the issues.

End Debate?

 

So Bill,you,uh,mentioned that you have some Bilsteins on your car;are they being used with the stock Supra springs or have you swapped those out for something else,or what?
The reason I'm asking is that in the event of these Supra TT shocks wearing out,I was planning on getting a set of the Bilsteins to replace them,as these have worked very well on my other cars.
If they crash around like you said,maybe I'll just get some more TT shocks,since they're rather oem-like in the way they work,a perfect match to the TT brakes/17" wheels for the unsprung weight factor I believe.

 

SCV8;

The Bilsteins and springs where fitted in Japan before I got the car, the struts have adjustable platforms and the springs are certainly non-standard (single rate), could well be Supra fitment, I just know the whole set-up is HARD and NOISY.

 

I've heard the Bilsteins will loosen your fillings, and yes Bill, end debate, you summed it up succinctly.
- Jon