[arizona charlie]

Today I spent time researching the possibility of changing wheels from the factory installed 185/65/R15 inch wheels which come standard on the 2004 Prius to a larger diameter wheel. The choice is either a 16 or 17 inch wheel.

The advantage of installing of a larger diameter wheel is that that your car will handle better. For proper fitment you will necessarily have to install a tire with a sidewall height which is not as tall as the factory tire. The lower profile tire will give you a harsher ride and will also cause you to replace the tire at 20K miles or less.

If you are concerned that the installation will cause your speedometer to misread your speed and that the trip odometer will not record the true mileage which you have driven is not a concern. After you have installed a larger diameter wheel on your car, you can bring your car to the service department at your local Toyota dealer and they will recalibrate the computer in your car to accurately indicate both the speed and distance driven.

Is it worth the bother? Probably not. Most of us did not buy the car to drive it like a Porsche or SLK 32 AMG Benz. If you were to make the change, you necessarily, for the sake of safety, should install a quality tire such as a Michelin Pilot Sport or a Bridgestone. The Michelins will cost about $190.00 each installed, the Bridgestones perhaps $150.00. Add the cost of a set of quality wheels and your will probably be looking at $1000.00 to $1500.00 to make the change.

Arizona Charlie

 

[john1701a]

There is a MPG plenty from having a larger tire, in the city & suburbs. Rollerbladers know that "from a stop" concept well. By increasing the wheel size a few millimeters, starting up again becomes more difficult.

And sharp turns become harder, so we really need to find out what "handle better" actually means with respect to Prius. My guess is that handling is improved at high speeds only, with a penalty when going slower.

On rollerblades, cruising is definitely improved with larger wheels. And since long sustained trips is what I prefer, that is a welcome change. It allows me to glide further between each stroke. Perhaps that translates to a highway cruising MPG benefit for Prius. Hmm?

In short, like everything else in life, there is no magic solution. A trade-off is required if you select either extreme. Fortunately, there are choices in the middle... like the tires that come standard.

 

[windsurfdog]

Help me understand this larger wheel thing........
You replace 15" rims and the tires that come on them for 16" or 17" rims with tires that have a slimmer profile. I'm assuming the outside diameter at the tread is not increased in order to have the tires fit properly in the wheel wells. You have gained a different look, a harsher ride and nothing else :?:

 

[jamarimutt]

You gain a different look, which is important to many people, but for daily normal driving you get nothing else.

Note that 16 inch wheels are standard in Japan and Europe (as are rear disk brakes).

 

[Jonnycat26]

Note that 16 inch wheels are standard in Japan and Europe (as are rear disk brakes).

Which is something I find a bit irritating... Does Toyota think we don't need to stop quite as quickly as our european and japanese counterparts?

 

[mdacmeis]

Note that 16 inch wheels are standard in Japan and Europe (as are rear disk brakes).

Which is something I find a bit irritating... Does Toyota think we don't need to stop quite as quickly as our european and japanese counterparts?

There is no adverse affect to stopping distance with the rear drum brakes. This is purely a cost and market acceptence issue. In Europe, rear disc brakes are the price of market entry. They may also offer better fade resistance at high speeds, something else somewhat unique to Europe. The real advantage is cost. The disc brakes are consiserably more expensive than drums. In the US, many vehicles have rear drum brakes, and most don't even know or care.

 

[Jonnycat26]

There is no adverse affect to stopping distance with the rear drum brakes. This is purely a cost and market acceptence issue. In Europe, rear disc brakes are the price of market entry. They may also offer better fade resistance at high speeds, something else somewhat unique to Europe. The real advantage is cost. The disc brakes are consiserably more expensive than drums. In the US, many vehicles have rear drum brakes, and most don't even know or care.

I disagree, and I think the facts will back me up here. The majority of midsize cars on the market, even GM cars, are all 4 disc brake standard (Alero, Grand Am, Grand Prix, Impala). And having come from a Jetta, and having learned to drive on Saabs, 4 wheel disc brakes are something you definetly learn to appreciate.

The only place you still see the disc/drum combo are on entry level cars. The prius clearly isn't. As you said, it's a cost thing, and we're being held to a lower standard than the overseas people.

 

[Phoenix]

Re: Rear drum brakes

I think Toyota figured that most people that spend the extra money to buy a Prius are interested in saving gas, and they are probably not going to be standing on the brakes approaching every red light. If you drive to maximize gas mileage, rear drum brakes are fine. The only time you might need disc brakes is if you do a lot of extreme mountain or high performance driving. And, if you do, you probably bought the wrong car. If you have to worry about faded rear brakes, you should probably be driving a sports car.

Also, all drum brakes aren't necessarily bad. I owned a 1963 Corvette that had drum brakes on all four wheels. Motor trend made repeated stops from 100 mph with no fade. (Just don't try that after driving through deep water!)

 

[lasrx]

For proper fitment you will necessarily have to install a tire with a sidewall height which is not as tall as the factory tire. The lower profile tire will give you a harsher ride and will also cause you to replace the tire at 20K miles or less.

I'm hoping not all low profile tires require replacement at 20k. When going for low profile tires look at the Michellin HyrdroEdge and MXV4 Plus both come in 17" and in low profiles yet are rated extreemly highly in treadwear. Depending on if you like rock hard tires for maximum mpg these tires could actually be smoother and more comfortable than the OEMs. $1000-1500 does sound right if you also add in extra light weight aluminum alloy rims (better MPG / handling).

If you drive to maximize gas mileage, rear drum brakes are fine. The only time you might need disc brakes is if you do a lot of extreme mountain or high performance driving.

In normal driving your probably not going to need it. However in an emergency, inches count. Add in potholes, uneven surfaces and even rain you'll wish you had every ounce of stopping power availible. Too much braking power is better than not enough. If you truly believe only sports cars have rear discs look agian. The Camry(SE, XLE, V6), Accord(EX, V6), Galant(STD), and Mazda 6(STD), and JP/EU Prius all have rear discs. All within the Prius price range, and are all considered midsized family sedans. Don't argue that the Prius is a compact, and should be compared to Corollas or Civics, its not.

In Europe, rear disc brakes are the price of market entry. They may also offer better fade resistance at high speeds, something else somewhat unique to Europe. The real advantage is cost. The disc brakes are consiserably more expensive than drums. In the US, many vehicles have rear drum brakes, and most don't even know or care.

Freeways in CA are definately a high speed roads, note 80+ MPH is not uncommon, its called criusing speed. Complete aftermarket drum to disc conversion kits start at $400, an automaker like Toyota would probably be able to get much better prices especially if they designed it into the car. R/D is nill as they could just lift the designs from the JP/EU Prius. Maintainance (pad replacement) isn't neccessarily going to be expensive because of the regenitive braking plus rear discs generally last twice as long as the front discs. Don't forget rear discs are easier to modulate and would could possibly even solve the "weird" braking feel some people complain of. Think of it like the HIDs, they aren't proven to be safer than Halogens. But seeing farther can help you avoid accidents, so isn't it safe to assume being able to stop faster would in turn also help you in avoiding accidents?

If Toyota does it at reasonable costs I'll consider that a good investment for avoiding a call to the insurance company or an ambulance.

 

[Jonnycat26]

I'm hoping not all low profile tires require replacement at 20k. When going for low profile tires look at the Michellin HyrdroEdge and MXV4 Plus both come in 17" and in low profiles yet are rated extreemly highly in treadwear. Depending on if you like rock hard tires for maximum mpg these tires could actually be smoother and more comfortable than the OEMs. $1000-1500 does sound right if you also add in extra light weight aluminum alloy rims (better MPG / handling).

My Jetta came with 225/45 17s (I believe... too lazy to look it up, but I'm pretty sure that's correct. At least the 225 and the 17 bit). When I got rid of it at 52K miles, only two tires had been replaced (due to some pothole damage). The two original tires still had plenty of tread life to them.

Also, you're absolutely right about the rear discs. It's always been my belief that Toyota should have included rear discs on the prius.

 

[lasrx]

I'm hoping not all low profile tires require replacement at 20k. When going for low profile tires look at the Michellin HyrdroEdge and MXV4 Plus both come in 17" and in low profiles yet are rated extreemly highly in treadwear. Depending on if you like rock hard tires for maximum mpg these tires could actually be smoother and more comfortable than the OEMs. $1000-1500 does sound right if you also add in extra light weight aluminum alloy rims (better MPG / handling).

My Jetta came with 225/45 17s (I believe... too lazy to look it up, but I'm pretty sure that's correct. At least the 225 and the 17 bit). When I got rid of it at 52K miles, only two tires had been replaced (due to some pothole damage). The two original tires still had plenty of tread life to them.

Also, you're absolutely right about the rear discs. It's always been my belief that Toyota should have included rear discs on the prius.

52k with plenty of tread seems right for tires of good quality; the MXV4 Plus is an 80k tire. The lower profile of the tires just means less sidewall, and less flex when cornering. When changing to a larger rim and lower profiles tires you can actually get to within 1% of the OE tire diameter this means there is no need for a speedometer recalibration or a negative increase in turning radius (city performance). The only down side is you will be more susceptible to tire damage from potholes.

 

[mdacmeis]

There is no adverse affect to stopping distance with the rear drum brakes. This is purely a cost and market acceptence issue. In Europe, rear disc brakes are the price of market entry. They may also offer better fade resistance at high speeds, something else somewhat unique to Europe. The real advantage is cost. The disc brakes are consiserably more expensive than drums. In the US, many vehicles have rear drum brakes, and most don't even know or care.

I disagree, and I think the facts will back me up here. The majority of midsize cars on the market, even GM cars, are all 4 disc brake standard (Alero, Grand Am, Grand Prix, Impala). And having come from a Jetta, and having learned to drive on Saabs, 4 wheel disc brakes are something you definetly learn to appreciate.

The only place you still see the disc/drum combo are on entry level cars. The prius clearly isn't. As you said, it's a cost thing, and we're being held to a lower standard than the overseas people.

Sorry to disappoint you, but I was a brake designer for most of the vehicles you mentioned above. The base model Grand Am comes with rear drum brakes. Now transitioning to the Epsilon platform (Malibu Max, G6), the base Malibu comes with rear drum brakes, while the G6 will be available only with rear disc brakes. There is no appreciable performance difference with either. Uplevel vehicles, such as the Grand AM GT, have offered the rear disc brakes to the appeal of those who will pay more for them, and think they are getting something extra.

To your GM midsize comment, Chevrolet typically has the rear drums (least cost product line) and Pontiac/Cadillac typically have rear disc brakes (performance image/high cost content). This is not always the case though. The Impala switched to rear discs in 2000. This was not for performance, but rather for platform commonization. Many trucks also have rear drum brakes. Ford and Chrysler have numerous drum brake applications.

Technically speaking, you simply need to generate enough torque to be able to lock the wheel on a high coefficient surface. Once you achieve that level of torque, unless fade becomes and issue, there can be no additional braking benefit achieved. Also don't be confused by the uplevel vehicle's shorter stopping distance numbers. This benefit is almost always a result of the uplevel tires, which are typically wider and offer a higher peak coefficient of friction. I can size either brake design to generate the torque needed. However the image is that disc brakes are better. In Europe, where higher speed driving is more common, higher coefficient brake linings, wider and stickier tires, and fade resistant rear disc brakes can provide a benefit, however they are not needed in the USA, and the resulting brake noise and harsher ride is also not well tolerated.

Just because other vehicles have something does not make them bettter. If the were true, the unique Prius drivetrain should be considered a disappointment since it is not the same as everyone elses. The real question here is if you were charged an extra $400 for rear disc brakes, would you get any benefit for your investment? The answer for this application is no.

 

[mdacmeis]

Freeways in CA are definately a high speed roads, note 80+ MPH is not uncommon, its called criusing speed.

For reference, high speed driving is considered to be sustained driving above 120 MPH, or 200 KPH. Doing a few stops from 80 mph is well within the capabilities of any brake system, and MVSS requirements demand demonstated performance at these speeds.

This is all about market acceptance and cost. No one is not buying a Prius because it does not have rear disc brakes. You have to stop somewhere. Add power seats, rear discs, performance tires, wider wheels, then see how many avoid the $30k upper model in favor of the $25k model. I understand it is something you want, however Toyota has decided to price the Prius at a $20k entry level price, and that is not possible with rear disc brakes.

 

[Joel]

Just because someone installs larger diameter wheels does not mean they are changing the overall wheel/tire diameter. In fact, my tire wheel combo is dead on the same overall height as the OE tire/wheel.

I believe there benefits to larger wheel / lower profile tires - other than just the improvement in looks. The added handling gains, improved wet weather traction should not be ignored for those who really enjoy driving (obviously not everyone here).

Larger wheels don't mean they are heavier - in fact, mine are eight ponds each lighter than the OE wheel - combined with a lighter tire - brings me to an overall per wheel weight savings of 11 lbs. Most pros will tell you that a pound saved on the wheel is like 10 lbs. saved on the chassis - because this is un-sprung rotating mass.

So why do I only get an average of 46MPG - the wider tires are stickier - increasing rolling resistance - I drive 65MPH 8/10ths of my daily driving.

Yes, the ride is more ridged, but not so different from those who put 42 PSI in their tires.

 

[lasrx]

Not to sound argumentative, but I think there is a case to be made for making some changes.

Although US Prius was never made to go 120MPH; as it simply won't be able to sustain a cruising speed that high. I would imagine brake fade being more of an issue with repeated braking such as constant acceleration and deceleration between a realistic 85-30 in rush hour traffic rather than 1 time stops from high speed. But your the brake systems engineer if you say its "enough" fine. I know drum technology has VASTLY improved since the '70s and are comparable to discs of that time period. But why are they so popular on other midsized cars? Except for entry models it seems that they are becoming standard equipment. If cost is such an issue why not just make ALL Prii the with rear discs so they dont have to maintain two braking systems, economics of scale right?

Toyota isn't selling many 20k entry level Prius. Their best selling version is the #9. Prius is marketed as being extremely environmentally friendly and loaded with the latest cutting edge technology. People are willing to pay for these things; look at the signatures on this board, many have or want a #9. It may be slightly skewed but my dealer told me that last month they got nine, #9s in and only one #7 and one #6. They dont even offer the base package.

I'm sure there is a (US) market out there for a Prius with 16" wheels and rear discs. You buy a Prius for the technology and peace of mind that they you are polluting 4X less than an average car. Its not about the money that could be saved (although its a nice bonus) as it would take about 4-5 years (62,500mi) @ $2.4/gal to equal the cost of driving for a comparably equipped Camry (unless gas goes up again). They could sell a upgraded Prius as the package #10 (based off a #9) and #11 (based off a #7). A #11 being a slimmed down version is great for people who don't need a JBL Premium Audio System, Home link, or Navigation, but includes safety features such as HID, VSC and side curtain airbags. The price could be as low as 23.6k and this is still less than what theyre charging for a #9.

The technology, the designs, and the demand are here. Toyota just needs to start pumping these cars out.

 

[TauZero]

Marketing point (from an engineer, so proceed with caution):

Even if folks aren't buying th ebase model, base model price is a (potentially/arguably) good way to get folks in the door.

"Gee, I can get this cool hybrid car with this great gas milage for 20K? Let me see!"

I suspect that, while probably not identical, most cars sell with more than base package

Tau Zero

 

[lasrx]

I'm a business major,and I have had marketing as well. Percieved value is as good as any technical value. Even if going to a disc only marginally increases performance in rain and hard use it is still a major marketing plus. The general public, not engineers believe that discs are safer so this is the "truth" Toyota needs to work with.

Toyota can sell it in so many ways that their car is not only the most enviormentally green and technological, its also one of the safest. Four wheel discs, ABS, VSC, Traction Control, HID, Side Curtain Airbags, etc.

Hm I didn't know the base was already up to 20,810, there isn't much room to work with to keep it in the important 20k range. Your right about the base price being kept low enough to get people in the door. But there are a lot of uncompromising #9 buyer's who want it all. So its quite probable there is enough demand to warrent larger wheels and discs in the more feature loaded models.

Or they could just turn the car over to TRD to come up with a post sale solution.

 

[mdacmeis]

I'm a business major,and I have had marketing as well. Percieved value is as good as any technical value. Even if going to a disc only marginally increases performance in rain and hard use it is still a major marketing plus. The general public, not engineers believe that discs are safer so this is the "truth" Toyota needs to work with.

Toyota can sell it in so many ways that their car is not only the most enviormentally green and technological, its also one of the safest. Four wheel discs, ABS, VSC, Traction Control, HID, Side Curtain Airbags, etc.

Hm I didn't know the base was already up to 20,810, there isn't much room to work with to keep it in the important 20k range. Your right about the base price being kept low enough to get people in the door. But there are a lot of uncompromising #9 buyer's who want it all. So its quite probable there is enough demand to warrent larger wheels and discs in the more feature loaded models.

Or they could just turn the car over to TRD to come up with a post sale solution.

This is a pretty good summary of the issues. However, the buyers of the Prius have proven to be different than those of mainsteam vehicles, not that it should be unexpected. Things to consider: the entry level vehicle is what generally gets somone in the door. The market price of the base model is generally what is stated in advertising, since one never knows what options the customer actually wants. In cases I am familiar with, (1) Vehicle A was standard drum rears and no ABS. Option was ABS, disc rears, and a gadget or two for $750.00. Less than 15% of buyers opted for the rear disc package. (2) For vehicles which offer ABS, Traction Control, or air bags as options, less than 20% of buyers select these options. This data has been valid since 1992.

The Prius buyers seem to appreciate more of the technology. We have seen reports, however, that suggest that many more #9's have been requested than Toyota anticipated. The reality here is that Toyota did not believe Americans would pay extra for rear disc brakes. We (the forum) represent a minority of owners. It is possible the majority agree with this. Or Toyota could have misinterpretted this desire.

To a previous comment: it would appear that having rear discs standard would leverage pricing and reduce cost. It does. But not to the level of savings achieved by offering the drum brake.

 

[ifftster]

only reason I like rear disk brakes is because they look good. Never really thought about which one operates better. guess i figured if disc was that much better than drum they would simply not make drum anymore. it certainly had no effect on my decision to buy a high qual vehicle like the prius. the drums haven't failed me yet(on any vehicle i have owned or operated).

 

[AgentElrond]

My 2004 came in at the dealer with Enkei 17" wheels* and Pirelli "P Zero Nero" (? - that's what it says on the sidewall) P215/45ZR17 87W M+S.

* Window sticker lists option as WB7; Enkei card (no model number) describes EFPC = "Environmentally Friendly Painted Chrome" - whatever that means.

mdacmeis, if you have any tech. views on these, I'm all ears.