Smaller sidewall tire size

Is that the Altimax RT or the Altimax HP that walmart is selling? I hope you didn't look at the tirerack ratings for the HP while looking at RTs at Walmart. Edit: I see you mention the H speed rating so they are HP. I'll leave the rest for lurkers that might not notice the difference.

I have the Altimax HP on our Saturn but wouldn't put the RT's on there because the traction is worse. The HP are 51 psi max, the RT are 44 PSI max.

The only advantage the RT has is longer treadwear rating and they make them in more 14" sizes so you can get them for an old 1990s Nissan hardbody pickup (D21).

General Altimax HP

General Altimax RT

Also on the Altimax (both styles) the RPM are

185/65/15 = 843 with 7.4" section width
205/60/15 = 837 with 8.2" section width

So not much change in RPM but definitely wider section width.

 

this is sort of interesting really

Thinking back, many of us older guys would recall how the diameters of wheels were quite a lot less 50 years ago. Considering small cars, gradually theyve moved up from 12 and 13" to more common 16", and I remember before the drag racing craze that if you customised a car back then, often wheels became wider but diameters were not usually altered.

On the purely aesthetic perspective I just wonder how this sits with wider 15 or 16" wheels that fill the guards well, instead of 17 or 18" wheels that are more popular now. I cant even remember seeing a gen 2 Prius with 16" wheels wide enough to fill out to the guards.

just a thought about options and compromises we should perhaps examine more closely

 

I remember 13" tires on cheapo cars when I was growing up. 14" tires were common on mid priced cars.

Going forward I've seen the creep until now we have the Prius with 15", 16", and 17" from the factory depending on the year/package.

Myself I'm in 3 mindsets when it comes to picking the tire size.

1. I want a tire designed for excellent traction (rubber, silica, whatever compound, tread design, anything they can do)

2. I want a tire that makes my odometer / speedometer accurate

3. I want to save money. That means lower price tires if I'm driving low miles per year and better fuel efficiency by way of lower rolling resistance if possible. More focus on LRR if I know I'll put the miles on it.

What size I'll get is more controlled 2 but 1 and 3 fight for influence in opposing directions.

I don't much care exactly how wide or exactly how tall my tires are. I care even less about how big the rims are.

Though I can tell you its harder to get good tires for my dads truck (14" rims) than any other car I own that has 15" rims. Considerably less choice in available new tires. For that reason alone I'd avoid unusually small or large rims.

 

of course one thing that would answer most of this and provides the 'best' of both worlds is fitting trim rings to alloy wheels.

For instance keep the 16" 'touring' wheels and ditch the hubcaps, which provides a relatively lightweight wheel solution, offers a good range of tyre choices
then add these or alternates
16inch Stainless Steel Trim Ring (2603)
......for that big wheel shallow sidewall look

as a benefit the save your alloys from scuffing

alternately play some options,
if the problem is overall wheel weight. Select alloy wheels and tyre combination in sizes weight competitive with the stock setup, and be in front of the the standard specification re acceleration and MPG.

Looking around at standard tyre weights of 17lbs, and perhaps advantaged by a few lbs in alternative wheel choices from high performance forged alloy wheels, if the theory that additional wheel weight holds, then less wheel weight offers even more performance. Dont know if its actually possible but I think it is a possibility.

 

Is there any update on how these tires and 205/60R15 size have done? Noise, handling, MPG, appearance? I am thinking of going from the 185/65/R15 to either the 195/65R15 or the 205 and looking for reviews from those that have made that change.

 

Steve I would wait if you can till the new Bridgestone Ecopia 001S becomes available in the US. The tyre is only made at the moment in 195/65/15, "more sizes to follow" it has the lowest rolling resistance of any tyre and is also rated with excellent wet grip. It is available in the UK.

The Uk gen2 Prius is fitted with 16 inch rims and 195/55/16 tyres, but I have fitted 205/55/16 to great advantage.

John (Britprius)

 

Thanks John. I do have time, though I recently rotated them resulting in increased noise. But I'm just starting to pull together some thoughts from reviews and advice. I have read that some have stated no MPG hit going to the wider tires but experienced greater stability and improved appearance. I thought I would either go with the 195 or the 205 and I guess go from the 65 to 60 to maintain similar rpm and MPG. What was the great advantage you observed going bigger and might I expect similar even with the 15" wheels?

 

Steve, I actually gained more MPG over the 195/55/16 OEM Bridgestone ER300's going to 205/55/16 Hankook Eco Kinergy tyres "around 3MPG", the 205 section tyres have a lower RR than the 195's of the same make and type. The wider tyres have now been on the car for 15,000 miles. There is also in the 205 16 inch size a much greater choice of tyres at up to 20% cheaper than 195's

The speedo is now more accurate "though still reads 2MPH fast", and the MFD now reports the fuel consumption so accurately that I now rarely bother to do the maths only doing it occasionally to keep a check on the MFD.

The only downside is the oddo under reads by 2.8% "the reason why the fuel consumption is now reported correctly, but it does mean my guaranty is extended by 2.8% millage wise.

There was also an unbelievable level of noise reduction.

The car now travels in a strait line without continual steering correction on motorways at speed with steering turn in greatly improved making it feel like a different car.

The weather here has just begun to warm up "around 10C" and just did an 85 mile round trip on a mixture of roads (country lanes, motor way, and town roads) returning 67 MPG "UK gallons".

I can only guess how bad the Prius must be on 185 section tyres.

The new Bridgestone Ecopia 001S is only being made at the moment in 195/65/15's and if I were in your position would fit that size to gain the advantages of improving the accuracy of the MFD, and speedo. This tyre in the UK/EU mandatory tyre tests comes out with an A rating for economy "the only tyre to reach this rating", and an A for wet grip. If it becomes available in 205/55or60/15 section size when you are ready for tyres go for that size at the 60 aspect ratio.

John (Britprius)

 

John, thanks for the detailed observations of your tire change. The results sound similar to some other reports I have seen here. You say the speedometer is more accurate yet still 2 MPH fast. How far off was it before? I'm guessing the system is designed to report MPH in relation to your 195/55/16 tires. Would there be a difference with the 185/65/15 or does the 55 vs 65 difference result in the same? I have read the 185/65/15 gives an inaccurate MPH readout but I thought it was like 2 MPH and corrected by going to the 195/60/15 tire. But then would the 205 make it incorrect again. I should probably be asking a USA driver instead of burdening you with this. I'm just thinking out loud.

I'm sure I will be going to either the 195/60 or the 205/60 next time. The Bridgestone Ecopia 001S sounds like one to look for. I wonder if it will be introduced here in the near future. Glad to hear the weather there has broke and presumably you don't have high snow drifts anymore since you are able to get out now.

 

Steve, my speedo was about 3 MPH out at 30 MPH, so the improvement was about 1 MPH or about 3% in line with the oddo now under reading by 2.8%.

The rolling circumference of the tyre or turns per mile (TPM) is what affects this. If you go to 195/60/15 tyres from 185/65/15's there will be virtually no difference in the TPM figure. This is because the hieght of the tyre wall is given as:-
For 195/60 tyres the hieght of the wall will be:- 60% of 195 mm = 117 mm .

For 185/65 tyres the hieght of the wall will be:- 65% of 185 mm = 120.25 mm.

For 195/65 tyres the hieght of the wall will be:- 65% of 195 mm = 126.75 mm.

So as you can see the 195/60 tyre will actually be smaller in diameter than a 185/65 tyre, and the 195/65 tyre will be 6.5 mm (or 1/4 inch) larger in radius or 13 mm (or 1/2 inch) in diameter.

At this larger size your speedo will be corrected by about 1 MPH or about 2.8%.

Hope this is not to confusing.

John (Britprius)

 

Steve, Should have added if you go to 205/60 tyres this works out at:-

60% of 205 mm = 123 mm.

This is only 2.75 mm larger than the 185/65 tyres giving an increace in diameter of less than 1/4 inch.
This is less than the difference between different manufactures, and is also less than the depth of tyre tread.

John (Britprius)

 

John, again thanks. This is very helpful. So with the 205/60/15 sounds like there would be practically no difference except in width with whatever that brings, maybe better handling, but no difference in the side appearance filling the wheel well. MPG depending only on the efficiency of the tire?

 

Exactly, one other plus point in going to this size is that the extra width helps protect the wheels from scraping the curb damaging the wheel covers. A final point, if you do go to a wider tyre change all four together. It is not a good idea to change just two.

John (Britprius)

 

Gotcha, good points. I am almost excited about changing tires now.

 

Check prices of tyres in your area of the two sizes 205/60/15 and 205/65/15 obviously of the same make and type as sometimes there can be a large difference in price between sizes, also there can be a large difference in the number of choices in a particular sizes.

John (Britprius)

 

May I ask, what kind of difference did you observe after going to this size tire?