Tire Upgrade

[dixon]

Originally Posted by nyprius

I’ve benefited greatly from the experience of others on Priuschat and therefore wanted to share my experience and research related to choosing a replacement for the Prius US OEM tire (Goodyear Integrity 185/65R15). My OEM tires had 25,000 miles on them with some tread left. But I’ve had bad experiences with them. So I wanted to upgrade. I’ve gone sliding on the snow with nearly no control. The tires are very scary in heavy rain on the highway. The car gets blown around and wanders on the highway. And it feels like it doesn’t hold the road well on turns. The Integrity is an OK basic tire. But as many others on PC have said, upgrading it will lead to vast improvements in handling.

When I looked on PC for tire recommendations, many tires were suggested, but three seemed to be recommended the most – Michelin Hydroedge (HE), Goodyear Comfortred (CT) and Goodyear Tripletred (TT). The TT was rated the best all season passenger car tire by Consumer Reports and Tirerack. I didn’t fully trust the opinions given on Tirerack and other self-entered tire opinion sites, such as epinions and 1010tires. On these sites, owners give opinions with little frame of reference other than the previous tires on the same car. These would have been worn down, so almost any new tire would feel better. More importantly, marketing people for the tire companies can enter good ratings on the sites. I have no proof that this occurred, but if you read the opinions given on the above sites, you’ll see many were almost certainly written by tire marketing people, since no one would talk about tires this way in the real world.

While the tests of Consumer Reports aren’t perfect, at least they’re unbiased (I hope). Tires are compared to peers on the same tests and cars. After looking at many tires, I preferred the TT. Of course, this is a personal opinion. The CT and HE are both great tires. As noted by others, they work well on the Prius. But given all the tests and opinions (even assuming many were from Goodyear), I was leaning toward the TT.

The problem was it didn’t come in the OEM size. I originally had a strong preference for sticking with the OEM size. However, as I researched it, I saw that Europe, Australia and Japan (where the Prius is designed and built) use a 195 width tire. The Prius is designed for a 195, not a 185 tire. I assume the US got a cheaper tire to keep costs down, in the same way we got rear drum brakes, while most other places get rear disk brakes. Alternatively, knowing the US appetite for more and better things, the US Prius may have been intentionally dumbed down (ie: narrow tires, rear drum brakes, front seats with no height adjustment, etc) so future Prius’s could be easily spruced up, thus prompting turnover among Prius owners who want the best.

Further evidence that the Prius is designed for 195 tires is the fact that the 2007 Prius will be offered with 195 tires in some option packages. (It is extremely unlikely that Toyota makes smaller wheel wells for the 185 tires. All Prius wheel wells probably are the same around the world.) Following an 04-06 US Prius on the highway, it looks like the car has bicycle tires. If you review the specs, very few cars of the Prius’s size and weight use 185 tires. 185’s are usually used on smaller cars. Given all this, I decided there’s no way I’m putting undersized 185 tires on the car again.

The problem with the 195 is tire height. If I wanted to change rims and go with a 195/55R16 (the tire used in Japan and Europe) I could get nearly the same revolutions per mile as the US OEM tire (855), which means speedometer/odometer readings and ground clearance would remain the same. But I didn’t think it was necessary to change the rims. 6” wide rims, such as those on the Prius, can handle up to a 225 width tire.

In the 195, I looked at the 195/60R15 and the 195/65R15. The 195/60 has 863 RPM (.9% higher than the US OEM). The 195/65 has 836 RPM (2.2% lower than US OEM). According to others on PC, the Prius speedometer over-reads by 1-2 mph (ie: it says you’re doing 60 when you’re really doing 58 or 59 mph). The 195/60 has less than half the distortion of the 195/65. It would increase the over-read by less than 1%, whereas the 195/65 would reduce over-read by more than 2%, possibly resulting in under-read (a more risky condition). Personally, I don’t mind a little over-read. It helps to minimize speeding tickets. The radius of the 195/60 is .325 cm less than the 185/65 (about one eighth of an inch). So ground clearance won’t be affected significantly. (The 195/60 tire is .65 cm shorter than the 185/65, but the car would only be .325 cm lower.)

I also considered a 205 width tire. There appears to be plenty of room for this on the Prius. Others have reported that the 205 works fine on the Prius. If you turn the wheel all the way to one side and run your hand around the interior sides of both front tires (US OEM 185), you’ll see there’s more than an inch between the tire and all points in the wheel well. A 205 is .3” wider than the true Prius OEM tire (195). This means it would extend .15” beyond the designed tire width toward the interior side, which is no problem. A 215 would probably work too. I considered the 205/60 because it has 846 RPM, (1% lower than OEM). This would partially correct speedometer over-read and give about .1” more ground clearance than the 185/65 US OEM tire.

I probably would have gone with the 205, but I noticed the tread width on the 195/60 TT and 205/60 TT are the same (6.4”). Therefore the wider tire would not give me wider contact at the road surface. I decided to go with the 195/60R15 TT because I felt the slightly lower tire would give me better cornering and less wind resistance. I felt the 1/8” less ground clearance (compared to the US OEM) and slightly higher speedometer over-read were not significant.

Also, while it seemed certain the 205 would work in the Prius wheel wells, I felt a little uncomfortable going beyond the “real” OEM width (195). Fortunately, the 195/60 TT gave me the best of both worlds. I got the wider tread without having to go with the wider tire. In terms of road contact, the 6.4” tread width of the 195/60 TT compares to 5.7” for the 185/65 CT. The HE tread width is not listed but is probably about the same as the CT. This indicates the TT will corner better with little, if any, mpg loss, as reported by others on PC who are using the 195/60 TT.

I put the 195/60 TT’s on a week ago. On dry pavement, the car sticks to the road like glue. The car seemed to be as stable in sharp turns as when going straight. I just got back from a 400 mile trip mostly in the pouring rain in Massachusetts and Vermont. Much was on route 2 in MA. A narrow 4 and 2 lane fast moving highway with lots of construction. On the US OEM tires, I would have felt like I had no margin of safety when driving at 65 in the rain on this road. I often gave up on trying to pass someone with the old tires since the car felt too unstable. With the new tires, the very wet road usually felt like a dry road. I felt I had a wide margin of safety – that I wasn’t anywhere near losing control. The car felt stable going through deep puddles too. No hydroplaning.

It was the same on the 2 lane Vermont 50 mph highways. I was cruising at 60-65 on windy country roads often in heavy rain. The car again felt very stable and safe. I also got over 50 mpg for the first time ever in my car. In the summer, I get 45-47 on the type of drive I did this weekend. This time I got 52 mpg. I was surprised. Part of the reason might be the .9% over-read on the speedometer/odometer due to the 195/60 tires (ie: when the odo says the car went 100 miles, it only went about 99).

Bottom line: The US OEM tire is poor quality and not the right size for the Prius. Putting good 195/60R15 or 205/60R15 tires on the car is an easy and relatively inexpensive way to greatly improve the performance and safety of the Prius, with little or no mpg loss. The car looks a lot better with the 195/60 TT too. The 195/60 is .4” wider than the 185/65. This is noticeable. It makes the car look more stable and solid. This is the way the car was designed to look.

Very impressed by all your research. I have a 2004 Prius with 75K miles and have now missed twice on replacement tires! The OEM tires got me only 31K, Pirelli P3000's decreased MPG dramatically so switched to Goodyear Assurances CT but only got 33K. Now have to try again and would like to get it right.

Wonder if you're still happy with the 195/60R15 size and the Goodyear TT as a choice? Also, any feedback on Cooper GFE's, a new LRR tire made in both the 185/65 and 195/65 sizes?

Many thanks for update, Dixon

[dixon]

Very impressed by all your research. I have a 2004 Prius with 75K miles and have now missed twice on replacement tires! The OEM tires got me only 31K, Pirelli P3000's decreased MPG dramatically so switched to Goodyear Assurances CT but only got 33K. Now have to try again and would like to get it right.

Wonder if you're still happy with the 195/60R15 size and the Goodyear TT as a choice? Also, any feedback on Cooper GFE's, a new LRR tire made in both the 185/65 and 195/65 sizes?

Many thanks for update, Dixon

[nyprius]

Hi Dixon,

Thanks for your feedback!

on the previous page of this tread, I mentioned that I replaced the 195/60 TT's with 205/60 Toyo Extensas.

The 195/60 TT's are excellent tires. But they became noisy. I also had a slight pull to the left that couldn't be fixed with alignment. I couldn't confirm if the tires were causing the problem since you can't rotate directional tires to the other side of the car without taking them off the rims.

So I got symmetrical, non-directional tires. As noted, the extensas are excellent. Very quiet and smooth ride. They handle well too. The TT's probably handled a little better on dry pavement. But I'm glad to give up a tiny bit of handling to get a much nicer ride.

The 205/60 probably partly improves the ride. The taller tires provide more cushioning on bumps. The 205/60's look great on the car too.


Wonder if you're still happy with the 195/60R15 size and the Goodyear TT as a choice? Also, any feedback on Cooper GFE's, a new LRR tire made in both the 185/65 and 195/65 sizes?

Many thanks for update, Dixon[/QUOTE]