nudderGS400

I am looking for the next mod to settle down the back end when cornering on rough surfaces (or bumps).

Currently, the Bilstein/Eibach combo, TRD front STB and LCB have helped a lot to improve performance. I am considering either TRD sways f/r or Tom's rear STB/LCB as the next mod.

Any advice abount which would help reduce the back-end walking more is much appreciated.

Thanks in advance.

RON430

nudderGS400 - Maybe someone can help but seeing as how no one has responded yet, let me throw in my two cents. If I understand your problem, it is one that is not very easy to get rid of. When the back end starts skating, especially breaking grip over a series of bumps (inevitably in a turn) it can be very difficult to handle. Especially because going stiffer can make it worse. Once the rear end breaks traction, it starts bouncing along. I am not sure anyone will be able to post a cure with a brace or a bar but if I were to guess, I would try more contact patch to keep the back end from breaking loose. The bars and braces will make the suspension less compliant and once it breaks loose, especially over bumps, it just makes things bounce along until you slow enough to re-establish traction. This is one of those areas where bimmers excel but it is having the suspension work as a complete package. All of the components, springs, shocks, bars, braces, bushings, body weight, tires, are all working together to keep the the tires planted. I am pretty happy with the bilsteins and TRD sways with the stock springs, I have a feeling that if I stiffen up the springs much I may get better body control but I will quickly exceed the rubber available. I don't really think I have given you a solution just some thoughts. This is a recurring problem and probably one of the worst to try and engineer out, I doubt you will every fully get rid of it. Some cars are far more prone to it than others. When it happens in a race car it is just like a big hand comes along and moves the rear end out. Of course, then you get those eyes like saucers for a short while....

nudderGS400

RON430 - thanks for the advice, you described it pretty well. I don't push it that hard thet I get the 'saucer look', but at high speed on the interstate around corners it is unsettling (no pun intended) when your back-end moves like that because of a single bump in the road.

Overall, I am very happy with the performance and handling of the car, just looking for the next logical place to work on. If the concensus is that neither sways or braces will noticably help, then I'll live with it.

I am guessing that the braces may help more since the change was very noticable for me on the front. On the other hand, if the car was flatter around the turns, (possibly transferring downward force to outside wheel through the bar) then that may be more noticable.

Eventually, will probably do all of it anyway.

Noticed you went with sways and shocks, and since your car is newer, it may not be as noticable, but for $300 from SG, the front bar and brace was (IMHO) a smart purchase. Makes the front feel a lot like a bimmer (you're analogy.)

oldguy

Ron430 can speak to this from experience. My past experience on another car leads me to believe his combination of stock springs, Bilstein sport shocks and TRD sway bars will lead to less understeer. TRD specs the front bar as 50% stiffer than stock and the rear at over 100%. This may be part of what you are describing. It is where I am heading, and in part for that reason. My shocks are to be put on next week, I have the strut tower brace and lower chassis brace (neither on yet) and the bars are coming as soon as the good folks in Japan send them to Steve. I expect the rear end to step out less easily. Bumps or just hard cornering or snow. My other experience was a S/C MR2 with ADDCO bars and Koni sport shocks. Huge difference in the back end of a mid-engine car. I'm hoping my GS430 handles as well.

I'll probably also add a limited slip differential , which will make it harder to brake traction, even on bumps.

Manaray

I too suffered from this but after I got my TOM'S 6-piece brace kit and TOM'S rear brace, I noticed that it "fixed" this problem...I think the problem is, is that the rear suspension is "too jiggly"...

Here's the suspension components I have on my GS430...

TRD Sway Bars - Front and Rear
TRD Front Lower Chassis Brace (Soon to be TOM'S Front LCB)
TOM'S Rear Lower Chassis Brace Type-B (Soon to be Type-A)
TOM'S 6-Piece Rear Link Kit
Ukyo Katayama UGO Carbon Fiber Strut Tower Bars - Front and Rear
H&R Stage 4 Coilovers (Soon to be Tein FLEX with EDFC)
HRE 20" 3-piece forged wheels (20x8.5 and 20x9.5)

The 20's are a little more "skittish" on rough turns than a 18" setup but the car still handles excellently. I've had many friends who own seriously well handling cars (like track Porsches) comment on how impressed they were with the handling of this car...

ShowGSLuVv

ok well I have two things to say, I dont know about u guys but I try to avoid going over bumps at high speeds it really bothers me to feel that and i know it isn't doing good any time it happens, another thing is if u are gonna take turns fast, and get annoyed by by the back end going out a bit, try putting the car in 3 if ur below 80 and if ur over then put it in 4, gate shifting helps alot going through turns to equal out some of the body roll, I went over bumps today going through a turn doin about 120 and i had it in 4 and the car took it like a pro, in fact I was racing a GS400 and was actually so far ahead of him im assuming it had to be 10 or 20 car lengths by that time so im not sure if he was pushing it to the limits but I was and it made the car handle very nice, maybe that might help

ShOwGS

nudderGS400

Tahnks for the advice Manaray -
What was the order you put on the rear STB/LCB/6pc?

Did you do the 6pc link and the LCB at the same time? Since the 6pc is replacing something (even if it is just stamped steel) that is all ready there, do you think the LCB was more important?

What do you think about starting at the top and working down? Flimsiest point (shock towers) to lower chassis?

Thanks!

RON430

Most times, the more comfortable you get with your car, the faster you drive, whether you know it or not. Just natural, race drivers make a living getting comfortable with a cars setup at any given track. A problem, very likely too strong a term, that doesn't show up on the stock suspension can come up after a few mods as you start driving faster without really knowing it. All the suspension mods in the world are useless if the pavement is junk. Racers complain about generally billiard table smooth courses because they are constantly driving at the limit of adhesion if they are any good and any road irregularities, even very slight ones, get the car upset big time. Worse thing has got to be bumps in mid corner that get the car unsettled. And why is it always the back end? Once the back breaks loose you can be an instant away from oversteer induced end swapping which can ruin your whole day. On top of his other mods, manaray obviously has some serious rubber at the corners and with the other mods he has must have some markedly increased g capability. I am at a lot simpler stage particularly because I really don't want to make too many tradeoffs on ride comfort. Race cars (and especially race tires) are great for sticking but not so great to live with on the street. I also think oldguy hit on a significant point. When I put on the TRD sways (and it is probably a lot easier than changing that ECU if you haven't done it) I felt the biggest improvement would come from the rear bar. The stock rear bar is just not very impressive for the mass of the GS. Only thing is, from my autocrossing days, it seems like the rear bar has more affect on the flatness of the front end and vice versa for the front bar. To demonstrate my grasp of the obvious, I look at the suspension in its entirety. I am pretty pleased with the handling and ride right now but when the stock 16s wear out (or I get tired listening to the Michelins howl) I will go to 245/50-16 which is going to drop the ratio a bit from the stock 225/55-16 and have just slightly increased sidewall stiffness to go with the larger contact patch. I am hoping this makes the last tweak on handling while keeping ride Lexus like and not loading down the rotating mass. Outside of continuing work on upgrading the sound system, figure the next hardware change is brakes. Problem is the GS has very, very good stock brakes, I just don't like the feel. Once again, I have pegged the weirdmeter. Obviously, I may have to make the tradeoff with bigger wheels and offsets if I feel the only way is to go with a big brake kit. I think I will fool around with the stock setup for a while, at least then the guy who gets the car after me won't have to spend weeks turning up pads for some unique setup.

QBranchCars

I also have a similar setup as Manaray's. I had the TOMs rear STB installed first, then the TOMs rear LCB and 6-piece together. the 6-piece replaces only existing 2-pieces, so four of them are totally new locations, hence greatly enhancing stiffness.

I think your next mod should be the TRD anti-roll (sways) bars, before the various braces. You'll see more benefits. My rear braces were the last suspension mods.

nudderGS400

Thanks everybody!

This thread has been extremely valuable.

QBranchCars - I think the sways may be the next mod. SInce RON430 also seems pleased with his decision. Probably add the Tom's rear STB after that.

One last thing......

Rod Millen Store is now listing Intrax f/r sways $425. Until I saw them I only considered TRD's. Anybody know which are stiffer, better fit, etc.? Want to order from SG! Maybe he can get the Intrax!?

bitkahuna

iTrader: (20)

Intrax sways apparently have bushings that require lubricating fairly regularly or they squeak.

The TRD sways KICK ***.

Manaray

Skip the InTRASH. Get the TRD's...

What I did in order (from memory...may not be 100% correct)...

1) TRD Front STB
2) TRD Sways and Front LCB and H&R suspension
3) UGO Front and Rear STB (removed TRD front STB)
4) TOM'S Rear STB and 6-Piece Link Kit

I only removed the TRD Front STB because I wanted matching front and rear STB's (I'm **** like that)...but I'm glad I did, cuz I would have had to change out the TRD STB anyways to get my Tein EDFC to work...