IS250/350 F-Sport front sway with IS-F rear sway, Best Balance?
12-04-13, 07:34 PM
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IS250/350 F-Sport front sway with IS-F rear sway, Best Balance?
I have started an earlier thread displaying my thoughts about too much oversteer on the sport suspension and F-Sport front and rear sways. I've swapped out the fatty rear for a stock IS-F rear swaybar, and the car behaves perfectly now! Doing slaloms or quick direction changes with the F-Sport paired bars felt off, somehow it seemed like the rear would turn before the front. And the car seemed very unstable at mid to high speed corners.
Changing to the IS-F rear sway has increased the bodyroll, but I definitely gained more comfort, a much more balanced front and rear end, and handling went from always oversteer to nearly perfectly neutral, able to go both ways. The feel is still miles better than stock, and to me it's better than the F-Sport full set as well. Whereas before I felt afraid of fast sweeping turns because the rear felt vulnerable and eager to step out, the car seems to turn naturally and instills a lot of confidence! Pass it on!
Not everyone will agree with me, and I even doubted myself before calling a friend with an IS-F to swap with me. But you can see from this video that the car would suddenly start sliding with not much warning with the F-Sport rear bar. I was thinking about getting the IS-F rear bar before the track event, but I just wanted to make sure it was as bad as I thought it was. I couldn't believe that Lexus would release such a tail happy kit! I know that I'm kind of throwing the car around on some turns, but it still shouldn't be that eager to tail whip out.
The IS comes into view around 12:00 minutes, but at 0:55 it takes off from a standstill and sounds like a sexy beast doing it!
Changing to the IS-F rear sway has increased the bodyroll, but I definitely gained more comfort, a much more balanced front and rear end, and handling went from always oversteer to nearly perfectly neutral, able to go both ways. The feel is still miles better than stock, and to me it's better than the F-Sport full set as well. Whereas before I felt afraid of fast sweeping turns because the rear felt vulnerable and eager to step out, the car seems to turn naturally and instills a lot of confidence! Pass it on!
Not everyone will agree with me, and I even doubted myself before calling a friend with an IS-F to swap with me. But you can see from this video that the car would suddenly start sliding with not much warning with the F-Sport rear bar. I was thinking about getting the IS-F rear bar before the track event, but I just wanted to make sure it was as bad as I thought it was. I couldn't believe that Lexus would release such a tail happy kit! I know that I'm kind of throwing the car around on some turns, but it still shouldn't be that eager to tail whip out.
The IS comes into view around 12:00 minutes, but at 0:55 it takes off from a standstill and sounds like a sexy beast doing it!
12-05-13, 09:59 AM
#2
I was hoping some of the people who'd changed the sways in their cars would chime in here.
Nobody else has done this and cares to comment on the differences in handling?
I checked sewell, and I don't even see an is-f only rear sway. Only the f-sport.
Nobody else has done this and cares to comment on the differences in handling?
I checked sewell, and I don't even see an is-f only rear sway. Only the f-sport.
12-05-13, 12:18 PM
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it should be in the low 200s with both the bar and bushings, but the CL Sewell discount might get you a better deal. If anything just look under the suspension category in the IS-F section 
12-05-13, 12:35 PM
#6
Everyone's setup is subject to alot of other factors, including wheels/tires and suspension (coilovers/springs/etc). Personally, for the way I drive my car and the way it currently sits (~2.25" lower than stock), I've found I LOVE the "feel" I have in corner with a stock front sway and rear F-sport sway combo.
12-05-13, 12:53 PM
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It definitely had a more solid feeling with F-Sport front and rear sway, but at least on my car I was more worried about what the car was doing after I exceeded the limits. I was on 225/40 and 255/40 tires and upgraded to 245/35 and 275/35 tires and still had the same results. With coilovers, you could use different spring rates and damper settings, so it's true I would have no idea how your car compares to mine I am curious how it compares though
I am curious how it compares though
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12-05-13, 04:49 PM
#8
When TRD first developed and tuned the F-Sport Accessories package back in '07 or '08 at Willow Springs as their own pet project, they did so with the intent that all the components would work in unison with one another, giving you a responsive, neutral-handling car. Your current suspension set-up is a bit different with you running the OEM sport suspension so your spring rates and dampers may be giving you the balance issues that you've been describing like GVille350 had pointed out. The F-Sport Sway Bar is definitely stiffer than the IS-F sway bar which is why a lot of 08-10 IS-F owners tend to install the F-Sport Sway Bar to reduce the heavy understeer.
If you haven't seen so already, below is a great video produced by Lexus with an overview of the F-Sport Factory Package and the F-Sport Accessories Package:
If you haven't seen so already, below is a great video produced by Lexus with an overview of the F-Sport Factory Package and the F-Sport Accessories Package:
12-05-13, 08:49 PM
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I watched that a million times before pulling the trigger on the sway bars. The problem I have is this, I can feel the change in how the car reacts to bodyroll and that the rear was just way stiffer than the front. I didn't want to resort to getting rid of the F-Sport bar, but I felt like the car was extremely unstable with it on.
I have put a rear sway on another car, a 2008 Honda Fit with coilovers and witnessed the same kind of results, less one-wheel tire spins b/c of flatter cornering, a more solid road feel, but also the introduction of oversteer. I have tried changing springs and playing with damper rates.. But if the sway is too stiff, than I feel like there isn't really a way of getting around it, only band-air solutions that require doing drastic changes to other things like spring rates or damper settings. So that would suggest that the F-Sport Accessories Springs and Shocks would make the car understeer like crazy without using the swaybar kit.. But I kind of doubt that.
I took my swaybar off the Fit today just to see how it changes the car, and immediately the car felt way more comfortable, but now I also get way more wheelspin in cornering because of more bodyroll. Whereas before the Fit would be fairly neutral and able to get into over and under situations, it's now a strictly understeer car although it still feels like it handles pretty well.
Anyways what I'm trying to say is that as much as I wanted to trust the F-Sport kit that is backed by Lexus, the rear just feels wayy too strong. Even their figures that they put out saying the front is like 40% stiffer and the rear is like 151%?? I know it understeers a lot from the factory, but something like 40% front and 60-80% rear increase would have made more sense.
I have put a rear sway on another car, a 2008 Honda Fit with coilovers and witnessed the same kind of results, less one-wheel tire spins b/c of flatter cornering, a more solid road feel, but also the introduction of oversteer. I have tried changing springs and playing with damper rates.. But if the sway is too stiff, than I feel like there isn't really a way of getting around it, only band-air solutions that require doing drastic changes to other things like spring rates or damper settings. So that would suggest that the F-Sport Accessories Springs and Shocks would make the car understeer like crazy without using the swaybar kit.. But I kind of doubt that.
I took my swaybar off the Fit today just to see how it changes the car, and immediately the car felt way more comfortable, but now I also get way more wheelspin in cornering because of more bodyroll. Whereas before the Fit would be fairly neutral and able to get into over and under situations, it's now a strictly understeer car although it still feels like it handles pretty well.
Anyways what I'm trying to say is that as much as I wanted to trust the F-Sport kit that is backed by Lexus, the rear just feels wayy too strong. Even their figures that they put out saying the front is like 40% stiffer and the rear is like 151%?? I know it understeers a lot from the factory, but something like 40% front and 60-80% rear increase would have made more sense.
12-06-13, 06:27 AM
#11
Between the F-Sport Rear Sway Bar, IS-F Sway Bar, and stock OEM ISx50 Sway Bar, the F-Sport version is easily the stiffest of the three.
Back when my car was configured with the stock front sway bar and rear F-Sport sway bar (along with my F-Sport shocks and springs), my IS was very tail-happy and I could easily oversteer with a slight turn-in and a light push of the throttle. It made the car a lot of fun to drive but it probably wasn't the ideal set-up for rear tire wear or lap times.
When I eventually swapped the front sway bar for the F-Sport version, the car lost a lot of its tail-happy traits and became more neutral.
I'd say that at the cornering limits, the F-Sport suspension kit is definitely an aftermarket set-up with the car's behavior being more tuned in the neutral/slight oversteer realm rather than the understeer set-up that most cars are delivered to the consumers for safety reasons.
Cars that are set-up with a bit of oversteer tend to do better around tight corners (especially for auto-x events) while cars that are tuned for a little bit of understeer will feel more stable around high-speed corners. It's definitely a preference of what set-up you're most comfortable with on the track and based on your input, the IS-F rear sway bar sounds like a good alternative to the F-Sport Rear Sway Bar for the ISx50 community. Either bar is a million times better than having the flimsy OEM rear sway bar!
Back when my car was configured with the stock front sway bar and rear F-Sport sway bar (along with my F-Sport shocks and springs), my IS was very tail-happy and I could easily oversteer with a slight turn-in and a light push of the throttle. It made the car a lot of fun to drive but it probably wasn't the ideal set-up for rear tire wear or lap times.
When I eventually swapped the front sway bar for the F-Sport version, the car lost a lot of its tail-happy traits and became more neutral. I'd say that at the cornering limits, the F-Sport suspension kit is definitely an aftermarket set-up with the car's behavior being more tuned in the neutral/slight oversteer realm rather than the understeer set-up that most cars are delivered to the consumers for safety reasons.
Cars that are set-up with a bit of oversteer tend to do better around tight corners (especially for auto-x events) while cars that are tuned for a little bit of understeer will feel more stable around high-speed corners. It's definitely a preference of what set-up you're most comfortable with on the track and based on your input, the IS-F rear sway bar sounds like a good alternative to the F-Sport Rear Sway Bar for the ISx50 community. Either bar is a million times better than having the flimsy OEM rear sway bar!