light wheels

[F8L]

Originally Posted by minispeed

Maybe it's that the light wheel reduces the amount of energy that can be had from regen braking. I know a couple people on priuschat have done a lot of testing with 17s and shown the heavy weight made a fuel economy hit.


OP where did you get them and in what size? I'm also looking for a light pair of wheels and like these.

During my testing I was using a set of lightweight 17" wheels (15lbs). One set of 15" tires weighed the same as the 17" tires so the entire combo weighed the same as the 17" combo so there was no net change in weight yet the mpg difference persisted much like it had with previous testing I had done in my GenII over the last 5 years. This along with other data like the OE 17" wheels (24 lbs) having and even lower impact on mpg leads me to believe that weight is not the prime force in determining mpg with wheels unless you do a lot of stop and go driving.

I think the bigger factor is tire friction and hysteresis.

[BHarvey]

What I have noted about 17's is that with lower profile tires you normally will take a hit in compound (softer) and load rating (lower). Both can affect mpg negatively.

[Christ]

Originally Posted by F8L

During my testing I was using a set of lightweight 17" wheels (15lbs). One set of 15" tires weighed the same as the 17" tires so the entire combo weighed the same as the 17" combo so there was no net change in weight yet the mpg difference persisted much like it had with previous testing I had done in my GenII over the last 5 years. This along with other data like the OE 17" wheels (24 lbs) having and even lower impact on mpg leads me to believe that weight is not the prime force in determining mpg with wheels unless you do a lot of stop and go driving.

I think the bigger factor is tire friction and hysteresis.

Don't forget about angular force.

Larger wheels push more of the weight toward the outside of the package, which gives it more of a levered advantage, and takes more energy to start/stop.

On most combinations, the tire makes up at least half of the weight of the total package. Do you want that weight all in a very compact area?

The plus side to lower profile tires, however, is that you can generally move more quickly through curves - less slowing down and speeding back up.

[Christ]

Originally Posted by Sporty Modder

IIRC for every 1 lb of rotating weight it is the equvialant of removing 7 lbs from the chassis. That being said, for each wheel you replace its like removing 100 lbs from your car.

This is only partially correct. It's a "starting point" for people to understand and make functional changes, but it's not even close to a strict rule of weight reduction.

WHERE you take the weight from has more to do with total performance than HOW MUCH weight you take off.

[royanddoreen]

Bought wheels at this site...ww.wheelandtireguy.com/products/Default.aspx?cid=46&clev=1

[vrmilionzx]

So, maybe I'm missing some key concept here - while what everyone has mentioned seems pretty on target, I haven't seen anybody address the fact the the prius picks up a serious bit of it's fuel efficiency due to the elec motor. The motor starts the car moving, and starting from zero is one of the more wasteful bits of driving - which is why stop and go is absolutely awful for your mpg. Since the electric motor starts you off, the lightweight wheels won't have as great an effect for a hybrid (my thoughts, not verified, not claiming it's fact). Seems to me that on things like a prius, while you might see small gains (although if what everyone is saying about heavier wheels kicking more juice back via regen. braking, then heavier might work better that way) from lighter wheels, you'd do better to get some taller (overall) wheel/tire combos, and work on aero.
My .02

[F8L]

Originally Posted by vrmilionzx

So, maybe I'm missing some key concept here - while what everyone has mentioned seems pretty on target, I haven't seen anybody address the fact the the prius picks up a serious bit of it's fuel efficiency due to the elec motor. The motor starts the car moving, and starting from zero is one of the more wasteful bits of driving - which is why stop and go is absolutely awful for your mpg. Since the electric motor starts you off, the lightweight wheels won't have as great an effect for a hybrid (my thoughts, not verified, not claiming it's fact). Seems to me that on things like a prius, while you might see small gains (although if what everyone is saying about heavier wheels kicking more juice back via regen. braking, then heavier might work better that way) from lighter wheels, you'd do better to get some taller (overall) wheel/tire combos, and work on aero.
My .02

The heavier and/or higher friction wheels/tires do require more eneger to get rolling. I notice this every time I swap out the lighter set. It feels like you are dragging something because ti requires more throttle to get moving. This will most definitely use more energy but maybe it is recovered with regen? I'm not sure.

My confusion comes from the fact that taller tires tend to help fuel economy on a fixed gear transmission by reducing cruise RPM at a given speed but on a CVT-like system what is the effect?

[LeanBurn]

I use the stock Corolla steelies for my winter tires and Prius wheels for my 3 season tires, both are 15". The Prius wheels are ~14lbs while the stock steelies are ~21 lbs. I notice a pronounced difference between the two straight away after the swap, in the handling/steering response department as well the car's pep starting off even when driving conservatively. I know the winter tread/compound are completely different, but it is remarkable regarding the dead weight even picking them up and mounting them.

[F8L]

Originally Posted by LeanBurn

I use the stock Corolla steelies for my winter tires and Prius wheels for my 3 season tires, both are 15". The Prius wheels are ~14lbs while the stock steelies are ~21 lbs. I notice a pronounced difference between the two straight away after the swap, in the handling/steering response department as well the car's pep starting off even when driving conservatively. I know the winter tread/compound are completely different, but it is remarkable regarding the dead weight even picking them up and mounting them.

Aye, I feel the same thing with my 17s vs. 15s. Be careful when trying to make any mpg conclusions though because not only do you have to contend with weight but you have weather and tire compound to think about. Some of the best winter tires are also the lowest in rolling resistance! The Nokian Hakkapellita (sp?) is Nokian's lowest RR tire and the Michelin XiCE does very well also.

[royanddoreen]

Tuneko Ltd has designed new TuneCover - hubcap range that will fit also on aluminium wheels. Purpose of these wheel covers are to protect the wheels outer edge from curbwall hits but also to save fuel. Fuel savings are from 2 to 5% depenging on rims design. Fuel saving part comes from reduced aerodynamic drag on speeds above 80 km/h (50MPH). Car will also accelerate faster and the cars top speed increases.Check out their site good story on a vw lupo.