Testing: Tanabe front sway bar

So I was the lucky sap to be picked by Tanabe to test a sway bar for the Prius. I dropped off my Prius in the morning, and they had me out before lunch time. At first I thought it was a test for the rear sway bar, so I kept looking for a rear bar and didn't see the traditional orangish-red trait of a Tanabe. I was a bit mythed since I knew they installed a bar and even left my stock bar in the cargo area. However, as I drove off, I noticed that the handling was definitely a lot sharper and tightly. The car reacted almost immediately to steering inputs, feeling was hyper-sensitive compared to the stock bar.

I decided to take it out on the freeway to do some higher speed runs and to test steering efforts on some off/on ramps. Holy smokes! Turn-in was so immediate! I was Braille driving on the inside Botts dots, caught out by the sharpness of the steering. I had to correct my steering input to compensate for the improved handling. Wow! Definitely liking the improvements. I took a couple more ramps, this time with full anticipation of the improvements, and wonder if you could make a more direct connection between brain to arms to steering to wheels turning... Once I got comfortable with the improved handling, the steering was so much more precise, and pushing the Prius was actually fun instead of being frustrated at the somewhat sloppy stock handling.

So I called up a friend with a lift to ask if he could jack up my Prius so I could have a look underneath. 30 minutes later, Prius lifted, I see the telltale Tanabe red in the front! Because of all the plastic shrouding under the car, I couldn't get an access point to measure the thickness of the front sway bar. However, my friend (who has a background in drifting and modding cars) was caught by surprise at how thick the bar is. I took some pictures but couldn't get s good view of the bar installed. Here's a link to the Tanabe site showing the details of the install: Tanabe USA R&D Blog | Toyota Prius (2010)

The important stuff:
My contact was with Danh at Tanabe. They run a top notch facility, and Danh was very professional and cordial. Danh showed genuine interest and understanding that some Prius owners want to improve upon the stock handling from the factory. He had mentioned that the aftermarket suspension pieces for the Gen III Prius have been selling a lot better than expected, especially compared to the Gen II Prius. He also said that of all the suspension pieces, the sway bars would make the most difference with improving handling (which I agree).
Good news is that the installation went well with no complications. I have to bring the car back in a few months to have them check the bushings. When asked, he said he didn't have the exact specs and thickness of the bar, but he'll email me once he receives that info from Tanabe Japan. Also no news on availability and pricing, although I think a decision will be made after the check-up.

Disclaimer: I also have Tanabe NF210 springs and a strut tower bar installed, so my car's handling was beyond stock sloppy prior to the fitment of the bar. The sway bar improved handling even further.

 

LOL. It could have been worse. They could have called the original tester back, so it would have been a black and WGM Prii testing again... or just a black Prius.

Thanks Mac. I'll tell him that you are demanding that Tanabe manufacture some Gen II suspension pieces for you to test.

Same here. I didn't like how the Prius was so resistant to turn-in. There is so much off-center play with the stock set-up that it requires a good amount of pull on the wheel to get the car to turn and then you have to constantly saw at the wheel to keep it tracking smoothly... No mas amigo! Stay tuned for Mac's review of the Gen II sway bars.

I definitely will provide an update once I get the specs from Tanabe. I also agree with your assessment of the STB. It really tightens the handling

I'll provide updated feedback once I get some more "seat" time with the front sway bar. A couple of initial impressions now that I've had some time with it:
1) Steering wheel feels a bit more "weighted." My previous car was a Lexus IS, and the steering weight of the Prius with FSB feels very similar. Just a nice "heft." I don't mean to say that it takes more effort to turn the wheel, the car just feels more substantially planted instead of bouncing all over the place. On the contrary, the Prius now reacts immediately to steering inputs.
2) Like I previously mentioned, the stock suspension set-up has a lot of play with the steering wheel. It also requires constant minute corrections to keep the car tracking straight, not excessive but enough to the point you have to keep attention. With the FSB, there is practically no play, and the Prius tracks straight. Firmly. Planted. No additional steering efforts.
3) Mid-turn and lifting off throttle, the FSB helps quickly tuck the nose of the Prius back in line controllably. No drama, no steering corrections needed. The car now provides great feedback as to what is going on underneath it.
4) Drawbacks? With the STB and FSB, the front end is quite a bit stiffer. This is noticeable under low weight situations, like when the gas tank is near empty. Push the car a bit, hit a mid-corner bump, and the tail end will want to talk with ya. Not that the rear will ever step out on you, but enough to catch you off guard.

 

Well, I'll see if I can find a empty parking lot somewhere and see if I could do my best impersonation of Paul Walker in Fast & Furiouos. The FSB does keep the Prius fairly stable at the limits but of course I would like to conduct more testing in a controlled environment.
As for less than perfect roads, not too many I could think of in SoCal unless I want to go into the 'hoods. There's a pass through a canyon I used to take to my old job many a years ago (like 6) which I wouldnt mind testing out. But it gets fairly crowded on the weekend. Theres always Ortega Hghwy but it's a traffic and police trap on the weekends. If I find any and conditions are right, you know I'll try.

 

Excellent advice... and something I plan to follow to the T.

I remember it to be 40psi front and rear. I'm still trying to find that delicate balance between economy and sport with these tires. Thanks for the advice on the tire pressure. I am have to test it for stability.

With your current setup, do you experience any bit of understeer? I was talking to Danh at Tanabe, who informed me that a bigger RSB would tend to cause the car to understeer more...

I'm running 205/55 16s, Continental ContiProContact. They are LRR tires but provide plenty of grip. Mid-corner, under hard acceleration, the tires just grip and rotates the rear-end very nicely. I haven't pushed it beyond what is controllable on the streets, but I can say that the limit on these tires are very high.

Similarly, trail braking around a corner is very controllable, although IMO, it could use a bit more grip. I think this is just a side effect of LRR tires. Through bumps mid corner, they still hold their own.

The 15 LRRs do slide very easily. When I was running with the stock Yoko 15s and had to brake hard and turn at the same time, I would also encounter that 4 wheel drift you are talking about. I know the Prius has anti-lock brakes, but my brakes actually locked up, forcing the Prius in a bit of a slide momentarily. Haven't had this issue with the 16's (nor the non LRR 17s which I ran for a bit), so my opinion is that the stock 15 LRRs don't provide enough grip under hard corner braking (or at the limit cornering).

 

Okay, so Danh from Tanabe just contacted me to advise that Tanabe just released specs of the front sway bar: 25.4mm in diameter. The FSB is on their website yet but still not available for purchase. Here's the link:
Tanabe USA Inc. - Sustec Stabilizer

Further feedback now that I've had additional seat time with the FSB: With the bar, the Prius just grips like a man hanging off a 20 story building.... Yeah, you know he'll eventually lose grip but while he's hanging on, he's gripping the edge for dear life. The FSB bumps the upper limits of handling and provides very direct, precise response. For those looking to improve and enhance the handling of their Prius, I would HIGHLY recommend this FSB. In fact, I'm surprised Toyota didn't develop one for their PLUS package.

 

LOL. Tempting. I already do that now... too bad I eat dust when the road straightens out.