Which Wheels/tires will improve MPG above OEM?

2004+ Prius factory wheels weigh 6.5kg (14.33 pounds). They are 15x6 inches, 100mm PCD, 5-hole, with 45mm offset.

The factory Goodyear Integrity tire weighs 17 pounds according to TireRack.com

That's roughly 31.33 pounds for the factory wheel + tire combo.

If you want to improve fuel economy, you need to find a wheel + tire combination that weighs less than 31.33 pounds and do this without increasing rolling resistance very much.

I am researching all of the popular "tuner" wheel brands (forged aluminum) to find a wheel with a weight less than 14.33 pounds. I've found about 6 or 7 so far. My research indicates that larger tires (say 17") get quite a bit heavier, so probably should stick with 16" or smaller.

If you don't care about appearance, you could go with some sub 10 pound, 14-inch racing wheels and skinny lightweight tires. You should be able to get a wheel + tire combination that weighs less than 28 pounds.

I am looking at 16x7 wheels with 195/55-16 tires.

Here are some links to wheel weights:

http://www.z31.com/wheel.weights.shtml

http://www.miata.net/faq/wheel_weights.html

http://www.gti-vr6.net/library/wheels_tire...wheels2_16.html

In order to get weight of tires on TireRack.com, you must choose a tire, then click on the "Specs" link for that tire. Then you can see all of the possible sizes and weights for each size. For example, here are the possible sizes and weights for the Integrity tire:

http://www.tirerack.com/tires/Spec.jsp?mak...rtnum=865SR5INT


I wish there was a table at TireRack to compare all tires by weight, but I have not found one yet.

If you are shopping for wheels too, you need to be aware of wheel offset. Here is a nice wheel offset calculator. Be sure to enter 45mm offset and 6 inches wide as the default current wheel spec, then specify the values for the new wheel spec you are considering. Then you should be able to tell whether it will fit in the wheel well or not.

http://www.1010tires.com/WheelOffsetCalculator.asp

B)

 

The stock 15" wheels have been reported to weigh 14.8 lbs each in previous threads. There are many aftermarket wheels that weigh the same or less. Most wheel manufacturers will supply the wheel's weight and/or there are databases on the 'net. Of course, you could bring a bathroom scale to your local dealer too. The question is how much do you want to spend - light wheels aren't cheap.

The stock 15" tire weighs 17 lbs.

Rolling resistance is a function of tread design, and to a lesser extent, rubber compound. A "higher perfomance" tire will always have greater RR than a tire like the Integrity. I don't mean to be disagreeable, but your statement, "I have discovered that you need a tire that has a pressure rating that allows tire pressures up to 45 or more... these are the ones that have the less road resistance, provided you run that much air in them." isn't true. The design/max air pressure is a factor of the tire's load rating/index. The reason that Prius owners are able to over-inflate their stock tires for extra mpg is that the car's weight is less than the tire's max load of 4672 lbs. This over-inflation slightly reduces the contact area (especially on rough surfaces) without distorting/ballooning the tread.

Really, it's a trade-off - lose a small amount of mpg and gain a small amount of safety (but only up to a point). If you stick to 185/65, you're mileage hit likely won't be that significant. The people who have experienced big hits to their mileage are the ones who have gone to 17". First, there are few (if any) 17" tires in a 185 width - most are running 205 or 215, which puts a lot more rubber on the road. Second, there are very few 17" wheel tire combos that aren't heavier than the stock 15" set-up. Third, most tires in that size/profile are in the "performance" category, where RR isn't really a concern.

Plus, at some point bigger tires will actually reduce traction (mostly in cooler climates, and wet/snow situations).

A good compromise would be 16" wheels like the OEM Japanese and European models and a 195/55 like the stock tire in those markets. From all reports, their mileage is (on the whole) the same as ours. The problem with that is that there are very few 195/55/16 tires available in North America, and the few light weight wheels that would fit are mucho dinero.

If you just want better dry/wet traction, I'd recommend sticking with 185/65/15 and getting a tire that has received good reviews from reputable sources. If you need snow traction get pure snow tires ("all-season" is marketing BS), and don't worry about mpg, which won't matter if you're in the ditch.

Now if you're talking looks... that's a whole different ball game.

 

Technogeek,

I wrote my reply but had to leave my computer for a few minutes, then returned and hit send, hence the repeated info. You could be right about that 14.3 lb weight, my figure was off the top of my head (There was a thread, but it was lost in the last board crash).

I too like to idea of 16x6-7 with 195/55 like Euro and JDM, but high cost and lack of availability/choice here in NA are a big factor. Let us know what you end up deciding on.

 

Wilco,

The fact that a portion of our two posts overlapped a little bit seems to indicate we're on the right track. This thread is going to contain some really great info.

BTW I still want to spend a few more weeks researching and thinking about the wheels and tires some more. There's a lot of good choices that could be made, now it's getting tough to narrow them down to one set of wheels and one set of tires. I will post pictures and real-world MPG figures before and after the upgrade. I'm still weeks away from making a decision.

I am also evaluating whether I should get a different wheel offset for the rear vs the front. The front track is exactly 1 inch (25mm) wider than the rear. That means the rear tires touch the ground approximately 0.5 inches narrower on each side. That means the rear tire does not follow the exact path of the front tire, it is skewed inward by half an inch. I am thinking of getting a different offset on the rear to bring the rear tires perfectly in line behind the front tires. Getting a rear wheel with an offset of 13mm less than the front should do the trick (if the front and rear wheels are the same overall width, say 7"). This means the tires cannot be rotated though because off the offset difference of the wheels. However, not rotating the tires means the rear tires are always along for the ride and should wear well, thus meaning only the front tires would need to be changed once during the lifetime of the rears. There are two main reasons for considering the different offset for the rear. First, tracking of the rear tires perfectly behind the front tires could improve rear-end stability (strictly speculative). For example, if you are driving on grooved pavement or catch a rut on a well-worn expressway, the rear-end could be more stable in situations like that. Again, strictly speculative. Second, it could improve appearance, as the rear wheels look like they stick under the car an extra 1/2 deeper than the fronts. Bringing them out pefectly behind the fronts would improve asthetics, at least for the hyper-detail oriented people such as myself. But I'm a car nut to begin with. I notice stuff like that. Anyway there would be slightly different wear pattern on the rear bearings, but if it's only a 13mm difference in wheel offset, it probably isn't going to make a difference. Just food for thought.

 

This differential is quite likely deliberate by the Toyota engineers, so I'd be hesitant to alter something that could adversely affect stability or handling withut knowing EXACTLY what I was doing. Perhaps you could e-mail the Toyota engineering dept. and ask why the differential is there - their answer would guide you to selecting the best offset for non-OEM wheels.

One inch is not trivial. If I changed the angle of incidence of the wing's attachment to my Cessna's fuselage by one inch, for example, I'd make the airplane completely unflyable. Certain measures are critical far beyond their apparent insignificance. If the engineers built in that inch, they did it for a reason. Perhaps the reaosn was mere styling - but I'd try to find out first. It'd be somewhat upsetting to blow $500 on wheels only to discover that you've made the car's handling a handful!

Mark Baird
Alameda CA

 

I've been messing around with cars for a long time too - and have experimented with wheel offsets on other cars (for performance - not appearance), and my advice is to stay as close to stock/centered as possible, and get four of the same wheels. Having 2 and 2 is a PITA. And, as another poster mentioned, the Toyota engineers likely designed the track that way intentionally.

There seems to be two threads on this topic running concurrently.:blink: This board had a crash a while back, where many threads were lost, and there was quite a bit of info on this topic. The bottom line was that everyone who went to 17" (even the TRD and Scion wheels which are pretty light) took a significant mpg hit.

When I was looking at wheels, the 16s that were light enough were more money than I can currently justify spending on this type of mod, so I'm not going to make a change at this time.

Take a look at Advan/Yokohama, Motegi, Volk/Gram Light, OZ, Konig, and Mugen for starters. Rota and BBS make nice wheels too, but I'm not sure they offer anything in a 16" that would fit.

Here are some links for wheel weights

wheelweights.net

mysportscar.com

As for tires (and this is the real issue with 16s in NA), the OEM (JDM and Euro) tire is the 195/55/16 Michelin Pilot Primacy (852 revs/mile - 20 lbs). I've driven a car with this tire in Europe, and it was better than the Goodyear Integrity, but a little on the noisy side. For better dry/wet performance there is the Toyo Proxes T1R (854 revs/mile - 18 lbs). That's about it AFAIK for "performance" tires in that size. There are the Nokians, which are good, but are more of a winter tire.

 

I'm seriously considering a wheel called the SSR Competition. Each wheel weighs only 11.8 pounds at a size of 16x7, versus 14.33 pounds for the stock 15x7 wheel. As you can see, these are an inch wider and have an inch larger diameter, yet weigh 2.53 pounds LESS than the factory wheels. These wheels are available in two finishes (Silver or Anthracite) with a polished lip on TireRack.com:
http://www.tirerack.com/servlet/CallJsp?ta...%2FMachined+Lip

I have included a picture of a 16x7.5 with a Silver Finish. Note that I would buy the 16x7 version, not the 16x7.5 version, and this picture is also of a 4-lug version, and the Prius needs a 5-lug version. I need to verify the wheel is available in 16x7 with 5x100 bolt pattern. I know it is available in 16x7.5 in 5x100 bolt pattern with 42mm offset. The factory wheels have 45mm offset, so moving to new wheels with a 42mm offset is nearly an identical offset and is within the acceptable range.

I have modified an original picture of a Prius using Photoshop to sort-of mock-up what the 16x7 might look like on a Silver Prius.

Now I just need to find some lightweight tires (preferably 19 pounds or less) in the size of 195/55-16 that are also VERY quiet.

 

the SSR Competition wheel in 15x7 is 9.2 pounds. 15x6 is 7.9 pounds. If you are looking for best MPG, get the 15x6 and keep the stock lightweight tires. Total weight would drop from 31.33 pounds for wheel+tire combo to 24.9 pounds. That should produce a noticable gain in fuel economy.

 

I'm familiar with SSR Comps (Speedstar Type-C in the rest of the world), but I didn't think they made a wheel with a close enough offset. Let us know what you find.

Don't know how quiet they are, but the 195/55/16 Toyo Proxes T1R weigh 18 lbs.

 

Wow, that's very light, especially for a 16" tire. That tire combined with a lightweight wheel would greatly improve handling characteristics. Something to think about... Thanks for the info! B)

 

I used an actual picture of a 16x7.5 inch wheel in the photoshop image in order to maximize accuracy. I counted the number of pixels used by the diameter of the 15" wheel in order to get a pixels-per-inch figure. Then I converted it to 16 inches and resized the new wheel to those dimensions. You are looking at what I think is a very accurate picture of the 16x7.5 inch SSR Competition wheel on a Prius.

Now I need to determine if the width of the wheel and the available offsets and wheel load rating are acceptable. I'm starting to have doubts because TireRack said a 5x100 bolt pattern can only be had with a 7.5 inch width wheel. The only two offsets are 35mm and 50mm. I'm concerned about clearance. I would prefer a 7 inch width and a different offset. So more research is needed.

 

I just posted a message to the fuel mileage forum regarding the impact of new tires. My mileage has suffered, and like you I assume that the more traction you need, the higher the rolling resistance will be and lower the mpg. The tires I bought are Michelin Hydroedge...good in the slop, but hard on the mpg, despite Consumer Reports calling them 'very good' in terms of rolling resistance.

 

I believe the SSR Competition has metallic paint on the spokes and a polished aluminum outer lip.

I called TireRack and found that in size 16x7 the wheel (spokes anyway) is only available in Anthracite which is a dark gray metallic color. It looks good but I was hoping for the light silvery finish instead. You must go up to the 16x7.5 to get the silver finish (as shown in the photoshop above).

Also they only come with a 35mm offset or a 50mm offset in 16x7 with 5x100 bolt pattern. I've read that people have put other wheels (not SSR) 16x7 with 48mm offset on the prius (default wheels have 45mm offset and are only 6 inches wide).

Moving from stock 6-inch wide wheel to 7-inch wide means the wheel is 25mm wider. Divide that by 2 and you find out that the inside wheel clearance is less by about 13mm. Bring the offset in from 45 to 50mm and we've lost 18/25ths of an inch of clearance. I wouldn't want to buy the wheels and find out they rub when turning sharp and going over bumps (suspension compression while turning) or something like that.

Moving to a 16x7 with 35mm means the outside clearance is reduced by almost a full inch. Not sure if the front can handle it (might rub on something).

But I admit I don't have Prius to conduct measurements of the front suspension. My 2006 is still on order.

I'm considering other wheels now because the SSR Comp doesn't come in the offset I'd like, and they aren't even listed as a possible wheel on the TireRack website when you choose Prius. Even though the wheels may bolt on successfully, they might rub (depending on the offset) on the inside our outside.

The search continues...

 

I find this discussion interesting, but I'm too cheap to change wheels (and a full size spare doesn't fit in the trunk :angry: ). I replaced my GY Integrity tires at 45,000 miles with Michelin MXV4+ 185/65HR15 tires. Here are my observations after about 1000 more miles on my 2004 Prius:

- They ride a litte harder (at 42/40 psi) but since my first car was a Triumph TR4, I can't be too critical .

- The handling on Dry/Wet/Snow seems better than the OEMs

- The MPG reads about the same (hard to tell exactly) but since the new Michelins have a somewhat larger diameter (causes the odometer/speedometer to read about 1% lower), I would say I'm actually getting about 0.5 MPG better now .

- Yes, I realize that these tires have a low treadlife expectancy (so did the OEMs) with a 400 rating .

I hope the group finds my experience useful.

JeffD

 

I am also waiting for my '06. I'm planning on replacing the OEM tires with either GY Assurance Comfort or TripleTreds, but am now also considering replacing the wheels (the latter primarily for looks). I'm curious to know if you guys have come up with anything, as I've had a hard time finding an inexpensive, light wheel.