Project log: Prius base suspension upgrades

Thanks Dan - this is another great option, and certainly the cheapest rear sway bar upgrade out there. I can attest from other cars that 20% change is large enough to notice.

If you don't want to spring for the ~$125 for the TRD bar, this is a good place to start. You may even be able to find one in a junkyard.

Jonathan

 

Update:

I've posted my impressions on Yokohama dB E-Spec tires. Relevant excerpt here:

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4) Yokohama dB Super E-Spec (Grand touring summer)
I replaced the stock touring Bridgestone Turanzas with Yokohama dB Super E-Spec's (195/55/16) purchased from TireRack at $139/each. I was after 2 main objectives:

a) Better turn-in response, transition, and overll grip
b) Equal or improved gas mileage
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Also, given I run a separate set of snow tires in the winter, I was not concerned with snow and ice traction. With these criteria, I eliminated wider than stock, heavier than stock, and any all-season tires that were not at least better than stock. The rest I left to research. I good place to start is TireRack's article: "When Round and Black Becomes Lean and Green"

Not sure the miles on the Turanzas - they came with the car and had been swapped from the touring with unknown miles. Turanzas were worn, but not bald, probably 4/32" left in the tread. Impressions after ~2500 miles below:

Comfort - These tires are quieter than the Turanzas, even with full tread. Quieter at steady state and quieter over bumps. I was not expecting this, but it is welcome

Fuel economy - I'm getting an average of 1-2 mpg better with these than with the Turanzas. This is a 2%-4% increase, consistent with what TireRack reports

Handling - Much better turn-in response. Car overall feels crisper and more poised. Steady state cornering ability is noticably improved. Wet handling is substantially better than stock. Overall, very happy with these in the handling department. These are certainly not the silver bullet, but a large improvement.
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Verdict: Pricey, but well worth it for the added safety alone, particularly in the wet. Not to mention the much improved handling overall.
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Update:

I recently got to drive an equivalent 2008 Prius base model with none of the upgrades I have made since starting this project. Wow - night and day difference. I described the un-modified prius as a "floppy fish" after driving it.

Major differences were in total grip, confidence in cornering (lots of lean in the un-modified base). The car just felt floppy all over the place - a real boat - vs the modified version.

Jonathan

 

Update:

I've posted my impressions of the TOMs front strut brace. Relevant excerpt here:

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5) TOM's front strut tower brace
This was a relatively easy addition to the car - 45 minutes from start to finish. I got mine from Sigma Automotive ($399). You'll need a 10mm, 12mm, and 14mm socket, 14mm wrench, 8mm hex bit, and torque wrench capable of doing 30 ft lbs. While it may look daunting given you need to take apart the front cowl and remove the windshield wipers, everything is easy to get to, remove, and re-install. There is a good how to with photos here:

[ame="http://www.flickr.com/photos/74284444@N00/sets/72157603921021144/"]BT Strut Tower Brace Install (by Gadgetdad) - a set on Flickr[/ame]

I took the car around some clovers and did some quick transitions at moderate speeds (35-45 mph) to test out the impact. The Prius behaves like you would expect with a front strut brace if you've ever used one before:

- Turn-is is crisper. Entering clovers, the car feels more connected to your steering inputs. The time between your input to turn, the car leaning, and then settling is reduced, making you feel more confident in corner entry. No change in amount of lean expected or experienced.
- As with all cars I've ever put a front sway bar on, the car feels more settled and stable throughout the corner - just a more solid feeling. You can consistently and predictably accelerate to the limit of the tires
- Likely as a result of the crisper input, transition response seems to be improved.

Verdict: Improved overall feel - not much overall improvement in grip. Better responsiveness to steering inputs is good. An expensive upgrade.

 

Josh - that's great news. Can anyone confirm having tried it?

Update: overall balance of the car
In other news, I took the car out and pushed it this weekend. I found that the balance overall is excellent.

On a clover, I pushed it to about 42 mph when the tires started to squeal. At ~45mph, it started to drift out from the desired line in a very predictable, slow, and, importantly, linear fashion. In fact, I was in a very mild 4-wheel drift.

After exiting the highway, I then tried sudden input into a 90 degree rounded corner (think merge lane on a right hand turn at a stoplight). I went in about about 30 mph and gave a quick steering input. Car entered the turn well, tires lightly squealing, and initiated a very mild 4-wheel drift (controllable, slow, and predictable - fantastic). Getting off the gas DID NOT induce oversteer.

Conclusion: The car is very well balanced currently and in my opinion still very safe to drive. If you need to push it, it is predictable and forgiving. The mods I have done to date I am very happy with as a combined package and would definitely recommend them.

Next steps: I still think there is too much lean in the car, particularly on corner entry. Further, I think the ultimate grip level can still be enhanced. To address, while hopefully keeping the great balance I have established this far, I will:

1) be replacing the rear struts and springs with the touring versions
2) Upgrade the front sway bar to the touring version
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As always, I will report back my findings. Happy motoring,

Jonathan

 

Thanks Josh - the Corolla is 24mm then? I'll have to look one up. What year(s) Corolla should I be looking at for my 08 Prius?

Thanks!

Jonathan

 

I've updated the thread with my impressions of the touring rear springs and stuts. Relevant excerpt here:

3) Touring rear struts and springs (5/7/2013)
I finally got around to installing the rear touring suspension - struts and springs. The parts were relatively inexpensive at the time of purchase - less than $300 all in. However, I had them installed by the dealer as I have just not had the time. This added nearly $400 to the total cost of this mod. Upon this writing, the front of the car remains stock save the BT strut tower brace.

Initial impressions: The rear of the car feels much more planted. Upon some low speed transitions (30mph - 40mph), the mismatch in roll between the front and back of the car if very evident. The front seems to be working very hard to keep up with the rear. That being said, the car tracks extremely well once set into a corner. Turn in is responsive, but not crisp.

I took a few higher speed corners - a clover onto the highway. Where before the car felt at the edge at ~45mph, with the rear struts and springs, the car felt very confident and tracked well. I was able to accelerate out of the corner onto the highway at full throttle with no loss of traction. I also tried to get the car to rotate mid corner by jumping on and off the gas. Even at 40mph in the clover, the back end stayed planted. I did notice the front end struggling to keep traction in this case - there is a hint of understeer creeping back into the car. This was confirmed on a 90 degree exit at 30 mph. The car tracked the corner well, but I could feel the front just barely skating along. I think the stiffer touring bar will even out the handling by setting up the front end faster. I will confirm Friday when I have it installed.

The verdict: Pricey, but well worth the investment. The margin of safety added to the car is quite large in cornering. The excitement factor is much higher, as is the confidence you gain while driving. Less roll is clearly evident and appreciated. If you can do this one yourself, it is a no-brainer. If you have to pay to get it done, I would think about how much you really want to push your car and if you would benefit from the added enjoyment of a markedly better handling car.
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Thanks all for the support and added advice and experience. I've enjoyed building up the car and glad that it can be helpful to the fourm. I'll keep the updates coming as I make more changes, but I'm coming to the end of the planned upgrades.

69shovlhed - Thanks - I'm looking forward to the bar. I've gone with OE bushings (not my initial preference), but again, since this isn't an ultimate performance machine, I think they'll be a nice compromise.

Jonathan