davidlmed

Just got the Front and Rear sways put on the 350. Can't wait to get some miles on them!!!

Micaiah

M and B are confusing me.

Now I dont' know what I want for Micaiah. Not sure if I should just get the rear or both because they work in conjunction with each other? Or just leave him be.

mong

iTrader: (4)

just get both..so you won't stress over it later on.

sangomaru

You should just pickup the sway set. My thought is since the front sway bar's slight increase in diameter over stock one, it seems to provide a balance and compliments the larger diameter increase of the rear sway bar.

Sewell

iTrader: (9)

By our informational technical resources:

IS250:
Curb weight
3,435 lbs. (RWD/AT)
3,455 lbs. (RWD/MT)
3,651 lbs. (AWD/AT)
Weight distribution, front/rear
52%/48% (RWD)
54%/46% (AWD)

IS350:
Curb weight
3,527 lbs. (RWD/AT) - a meager difference of just 92 lbs
Weight distribution, front/rear
52%/48% - still, the same balance shared by both models

The stock front and rear sway bars to share the same part number along with many of the other suspension parts (i.e. end links, control arms, shocks). All this is excluding drivetrain options, like MTM and AWD. The upgrade sway bars too are the same for both the 250 and 350. Our assessment is the F-Sport brochure and catalog is incorrect. We do not call this lying or misleading, we just call it incorrect. This is not the first time F-Sport has been incorrect with the published technical data. In the couple times we cited errors on the F-Sport cite, it took them a bit of time to make the adjustments.

I hope this helps.
Darrel

brociouz

iTrader: (65)

^ Thanks for the info Darrel. So Lexus really must be wrong then. But what about all the first-hand accounts of people saying the IS250 handles better than the IS350 stock for stock? Identical weight distribution and 92 pounds (less than the weight of a person) is not it. And I wonder what the true improvement numbers are when upgrading to F-Sport sways... maybe in 2 years Lexus will release them. The mystery continues.

uz07lex

iTrader: (14)

if you have the cash get both but i will tell you the rear is awsome youll love the feel. my friends want to know if i redid my suspension and all i did was the rear sway.

flowrider

iTrader: (9)

OK, I've been telling you guys this for over a year now. The chart I have posted is in fact correct, and when I post something as fact, I do my homework. I just don't guess.

Lou

SC3coupe

iTrader: (4)

92 lbs is quite a good bit of weight, just relocating a battery to the trunk can make difference in handling already.

Sewell

iTrader: (9)

Well, my question has always been since there’s no universal constant for a baseline, how does one measure, equate or discern the measure of stiffness relating to body roll and handling. I've always considered lateral G-Force to be a better measure that % of stiffness. One driver may notice a significant difference yet another driver didn’t notice anything – well, I’m sure the conditions of driving were not the same and the factors were probably different as well.

As for the technical data post above, remember the stock IS350 is equipped differently like 18” staggered wheels while the IS250 standard options have the 17 x 8 wheels all around. The rear exhaust is different as well with the IS350 having a larger diameter pipes. These are just minor examples of where some of that 92 pounds weight is derived.

brociouz – I agree, the jury’s still out on this one.

Darrel

syzygy

I completely agree, I find the %stiffness figure to be relatively unintuitive.

Various independent magazines have tested lateral skidpad g force for the IS350 with F-sport sway bars.

Stock IS350 = .84g's + massive body roll
IS350 with F-sport sway bars = .90 g's + body roll severely diminished

Improvement of .06gs and much less body roll - not too shabby

Sewell

iTrader: (9)

carLx - would you consider posting your source to allow me to reference it on our site?

syzygy

Absolutely. The one that cited .90g's was one of the "follow up" tests by either car and driver or road and track which I'm trying to find right now.

In the meantime, I did find a few other sources that cite a figure that is close (.89g's).

Edmunds Insideline IS250 F-sport "follow up test" -

http://www.insideline.com/lexus/is-2...w-up-test.html

"Handles Like an IS-F
And it turns.

Powerslides are impossible with the big tires and little engine, but this car scorches our track with handling numbers that exceed the performance of the mighty IS-F. No, we're not kidding. This IS runs 71 mph through our slalom, circles our skid pad at 0.89g of lateral grip and stops from 60 mph in just 109 feet."

I will try to look up the source that recorded .90g in the meantime, hang tight.



Edit:

Here is Road and Track's test for a stock IS350 where they measure .84g's -

http://www.roadandtrack.com/tests/co...7-lexus-is-350

Click on the "data panel" under downloads -

http://www.roadandtrack.com/var/ezfl...b477099096.pdf



Edit again:

I Found an edmunds insideline testing the IS350C with F-sport goodies -

http://www.insideline.com/lexus/is-3...and-video.html

Again, they measured .89g's there.

Looks like an improvement from .84g's to .89g's is the best thing to put, since I've readily found two sources that cite .89g's so far. I'll keep looking for the .90 g's though and update this post as needed.

syzygy

Eh I give up can't find the .90g.

For stock IS, use road and track's figure of .84g. For F-sport IS250 and IS350C, use edmunds insideline's figure of .89g (.05g improvement).

Oh, I'm not sure if any of those magazines specifically mention body roll, but the diminished body roll after F-sport sway bars can be pretty easily discerned. It's one of the first things I noticed after I got my sway bars.

Honestly it pains me to see so many IS350s out there without F-sport sway bars, really a travesty given that the difference is so tremendous both objectively and subjectively.

Kurtz

iTrader: (1)

Actually, no... on RWD models the wheels are exactly the same 250 and 350.

http://www.lexus.com/models/IS/detai...fications.html

17 x 8.0-in 10-spoke alloy wheels with 225/45VR17 front, 245/45VR17 tires rear, is standard on both 250 and 350 models.

18s are optional on both.

AWD 250 is the only one that's different (17x8 non-staggered 225/45VR17s on all 4 corners as standard)



The Lexus F-sport info simply must be wrong... and given it's not just one website, but several they have put up over several years, plus printed material, one is inclined to believe it's not accidental.

Sway bar rate math is pretty well known... for example-
http://www.fromsteve.net/tech/Sway-Bar-Rate-Calculator

It has nothing to do with the car you put the bar on. It only cares about the dimensions of the bars.

As I said the most generous way to read it is that when they say the bars are x % stiffer they don't really mean that... because the bars are identical 250 and 350 both stock and F-sport. They are instead trying to represent some change in behavior on the car itself, rather than telling us about the bars. But it's certainly not written that way.