Lowering Prius IV on stock 15's

This is good information. It makes sense to me as my Vette goes 2 mph faster and .2 quicker in the 1/4 mile from adding skinny and light tires up front and other minor weight reduction. Unsprung weight makes a huge difference.

And you are right, I'm a very well versed forum guy, just getting lazy in my old age I guess. Sorry about that. I know better.

I answer the same questions over and over at Corvetteforum, but hey, I make new friends doing it so it's ok.

Thanks for the info.

 

I knew this was not your first rodeo. I used to be at Corvetteforum.com and Ls1tech.com as well.

Some things transfer over from drag racing and some don't. In is case, light weight and narrower tires do translate. Unfortunately, weight doesn't seem to play as large a part as one would think. Unless you do a ton of stop and go city driving I wouldn't bother spending big bucks on super light wheels. Anything under 24lbs/ea. is fine. Tires are the key ingredient. You simply must choose a good low rolling resistance tire or you'll be looking at those 4+mpg losses for sure. Hit me up when you're ready for a tire and I'll provide more info.

 

^^^ Will do! I did read the sticky on tires but I'll be in the market in 6 months or so and I'll hit you up.

I see you are a valued member here...nice to e-meet you.

Ps I'm on ls1tech too, since 1999. It's loose or lack of moderation cause me to rarely get on, too many disrespectful posts.

Lol I realize I've hacked this thread beyond belief. I'll stop now.

 

Nice to meet you too. It's good to see some fellow LSx folks in here. You'll have to meet xs650 and ask him about his new supercharger on his C6.

So to get this thread back on track, for those who want a more sporty look without giving up fuel economy or comfort I suggest getting the lowering springs and sticking with 15" tires. When it comes time to change tires try to find a set of Michelin Energy Saver A/S 195/65/15. They offer 2-3mpg better than the stock tires, they are quieter, last longer, are more comfortable, blah blah blah.

 

^^^ I googled the tires and your review was at the top. Great review.

Michelin Energy Saver A/S Review | PriusChat

 

I think this forum is very well moderated. I don't see personal attacks and bickering, but we have the freedom to digress a bit (or a LOT in the case of this thread) without a moderator in jackboots coming into the thread and stomping all over us.

Back on topic:

Wheel weight is a factor, but so is tire weight...those larger diameter tires usually weigh more. Also, as I pointed out earlier in the thread, you're moving the weight farther from the center of rotation, which means it takes more energy to start and stop the weight.

In the Energy Saver A/S Plus, a 195/65R15 is 18 pounds and a 215/50R17 is 22 pounds. That's an extra 4 pounds per tire, with the weight moved out farther from the center of rotation. Even if the larger diameter wheels are the same weight as the 15s, that's a significant weight gain. Now think of how light an aftermarket 15" wheel can be...I've seen some that are 10 pounds or less, compared to the stock PipA alloys at ~18 pounds each, if memory serves.

 

I understand all of this and have made the same arguments. My reason for discounting weight is based on steady state operation where weight becomes less of a factor and the fact I have tried a set of 15lb 17" wheels and 24lb 17" wheels using the same tires. The effect was not noticeable.

There is also the argument for the OE 17" wheels at 24lbs and Toyo Proxes A20 at 21lbs. This combo while heavy does not drop mpg nearly as much as a lighter wheel and other LRR 17" tire.

My point? If you like a particular super light 17-18" wheel and can afford it then by all means buy it. I simply do not recommend buying an ugly wheel that is expensive just because it is light. The difference in fuel economy between such a wheel and a heavier cheaper wheel is negligible.

 

How much do the stock 15s weigh? 16 lbs?

 

The SSr Competition Type C wheels on my Supra were 18" (I would have preferred to stick with the OE 17" diameter, but got the 18s lightly used for $250/wheel instead of their MSRP of $500/wheel) They weighed 17.9 pounds vs. the OE 17" wheels @26 pounds each, despite the larger diameter. They also looked nicer. That same wheel, in a 15" diameter, weighs about 10 pounds, but unfortunately isn't offered in the Gen 3 Prius bolt pattern.

The 17s rode better though!

 

Yes. 16.3lbs approx. for the non-PIP wheels.

18lbs for the PIP alloys.

24lbs for the Prius Model Five 17" wheels

22lbs for the Performance Plus 17" wheels.

 

Here is my goofy math from back in 2009.

 

I agree...this is a great forum and well moderated for the reasons you state above. Moderation is a fine balance and so far this forum is hitting it perfectly in my book.

Nice helpful folks as well.

 

Well F8L found his way in here, hands down the most knowledgeable wheel tire guy I have met. Glad he clarrified my assumption.

My only question would be typically when people go to a 17 they go wider on the rim/tire. I would like to see a test maintaining the same width and thus a much closer tread patch. My guess woudl be thats what puts a strong hit on larger rims/tires by increasing the rolling resistance.

 

I tried keeping the same width when I did my weight comparison, but F8L's recommended brand/model of tire doesn't offer a 195mm width in a 17" diameter tire, so I went with the narrowest 17 they offered. Wider tires will also increase the C/D, even if only marginally.

 

That's the crux. Rarely will you find a 17x6" wheel and even worse is the lack of acceptable tire sizes that would fix. My solution was to use a 205/50/17 which reduces tread width and slightly increases diameter. My hope is that the extra diameter decreases gear ratio (overdrive compared to a 215/45/17) and helps offset the extra width (195 vs 205). Blah, who knows. lol

 

Overdrive only helps if Toyota didn't already optimize the gear ratio for the available torque...Maybe with the "simulated CVT" it won't hurt though.

 

So.... straight to the point, how low should I go?

- 2013 Prius III
- Stock 15's
- No Suspension Mods (yet, but considering: Rude person's's Center Brace, Rude person's's Front Brace, Cusco Strut Tower Bar)
- Purchased: Eibach Pro-Kit Lowering Spring Set
My dealership friend (at Toyota) is offering to install the springs w/ included alignment for $200 cash under-the-table. Yay or nay?

 

Disregard my previous post... I'm an idiot. I clicked on my own link of what I purchased and it clearly states what the springs are pre-lowered to. 1.2" in the Front and .08" in the Rear

 

yeah, you listed a spring kit not a coil over kit.

Alignment alone will run you around $50 or more.. sounds like a good deal. Don't get it aligned right away, you'll need to break in the springs.