Tires again??

[JimIsbell]

Looks like I need new shoes.

Are the Portenzas still the best tire for the Insight or has someone come up with something as good??

A note on tire wear and high tire pressures:

I have about 70K on theses tires and I think that is pretty good. At the beginning I was running 44 PSI as was recommended by the seller who put 40K on them. For the last 30K I have been running 52 PSI. The tires are showing the wear on the outside! So running 52 PSI does NOT cause wear at the center...yet.... Maybe I should run them at higher pressures to get rid of the wear on the sides...# But then that side wear pattern was probably set in the first 40K miles by running them at too low a pressure...44 PSI.

[Kevin Dougherty]

Originally Posted by JimIsbell

But then that side wear pattern was probably set in the first 40K miles by running them at too low a pressure...44 PSI.

Not really Jim. I've been running mine at 50 since install and have the same edge wearing pattern.

[crx_rogus]

The RE92s are rated on the sidewall for 44psi max inflation pressure, yet I've read of folks running them at up to 60psi w/o issues. Past 44psi seems like asking for catastrophic safety issues, especially at sustained speed.

What is the consensus from experience regarding max real-world tire pressures for the RE92s?

[satchel]

These have been run at 60# for over 22,000 miles. Very even wear and the little tits are still on the edge of the tread because the tire doesn't roll over on the sidewall on corners. Handling is better IMO.
Crx_rogus, I don't know where you get this catastrophic safety issue at speed business. Sustained speed creates MORE heat in an UNDERinflated tire because the sidewall is allowed to flex more. This was the issue with all the Ford Explorer tire failures. They were underinflated and combined with people's inability to monitor their tire pressure it led to tire failures and deaths.
The only real alternative in OEM size is the Michelin Energy sold in Europe. It is a all-season LRR tire where the Energy sold in the USA is not, totally different tread.

[JimIsbell]

Good picture. Its worth a thousand words!!!

Mine looks just about the same except that the wear bars on the sides are beginning to show. In the center they are not indicating wear. These are the front tires I am talking about. The wear bars on the rear tires are not showing at all so I may just rotate front to back and increase the pressure to 55#. But, hey, with 70K on them I am well pleased.

BTW, most of this last 30K miles was on the highway at "sustained speeds" of 70 to 85 MPH....while getting 70 to 85 MPG.

As to problems from over inflation, I see none. My car handles better and gets MUCH better MPG. There is better traction in ALL conditions because the tread stays on the ground at ALL times and doesn't roll up on the side wall. I see no indication of any tendency to hydroplane, in fact, I see the opposite. With the higher pressures the water doesn't get trapped under the tire but is allowed to spread to the side and out from under the tread.

[crx_rogus]

Originally Posted by satchel

Crx_rogus, I don't know where you get this catastrophic safety issue at speed business. Sustained speed creates MORE heat in an UNDERinflated tire because the sidewall is allowed to flex more. This was the issue with all the Ford Explorer tire failures. They were underinflated and combined with people's inability to monitor their tire pressure it led to tire failures and deaths. ...

I was figuring the 44psi max pressure rating suggested that if you go much above that it would rupture, especially if heated by more sidewall flexing at speed. But when it's already hard as a rock vs. 34 / 38 psi, then sure, there won't really be any sidewall flex (thereby minimizing the "I'm driving on narrow tires" steering response lag). I guess I'm just wondering how much of a safety margin there is with the tires; how much pressure would it take to rupture them? Noone's experienced or heard/read of anyone else experiencing ruptures with over-inflated RE92s?

I also live in Pennsylvania, home of some highway stretches bad enough to blow out truckers' headlights. The thought of a 44psi -rated tire on a 14" wheel dealing with a bumpy pavement at 65mph while inflated to 60psi does not induce complete serenity. Many PA highways have plenty of rather large disintegrated tire fragments from 18 wheelers lining them, especially a bit after the more memorable bumpy stretches. I really don't want to add to them, nor add me in my Insight to them.

[crx_rogus]

Originally Posted by satchel

...Crx_rogus, I don't know where you get this catastrophic safety issue at speed business. ...

A search for "blowout from over inflation" yielded this, tread separation at 75 - 85 road trip -sustained mph at 50psi, 35k miles on tires, but pretty much only that for tire problems... amazing tires! My commute does include some length on a winding back road, and I do consider not braking much for turns a very valid mpg booster (minimizing tire slip would really help there), but don't want that to lead to a dramatic tire event (especially while cornering hard).

[red1dr]

Roger, it turns out I have a tiny bit of data which bears on this. My Subaru tires are rated at 51psi, and I run them at that. Late one hot sunny summer morning last year I checked them (car had sat all night and was in the shade), drove about 70 miles on I-95 in 85-95 degree air temp, pulled into a gas station, and immediately checked them again, using the same gauge I had used at home (a fairly good dial gauge). The pressures were no more than 1psi higher, if that. So the tires did not heat up significantly (Boyle's Law). If they had been at the Subaru-recommended 32psi I'll bet there would have been a measurable pressure rise, but unfortunately I didn't run that scenario.

Tire mfrs probably build a large safety margin into tire pressure ratings:
(1) gauges on gas station air hoses take a beating and are often wildly inaccurate;
(2) if a tire explodes from over-inflation, determining the pressure it was inflated to would not be easy;
(3) statistics: for liability reasons tire manufacturers don't want ANY explosions, and the only way to ensure that not even 1% of tires would explode at even 20 psi over the rating is to make them strong enough to withstand much higher pressures (I've heard 200psi quoted) - don't forget that tire shops often overinflate tires when mounting them to set the bead.

As for truckers, I don't know if recaps are still commonly used, but some of the shed treads could be from poorly adhering recaps. Another consideration is that truckers often continue with deflating or flat tires, letting them disintegrate on the highway. I have seen this on I-95 around here. When you think about it, the tire is probably shot anyway and stopping on the road means delay and an expensive roadside service call. So they cut their costs and either continue to the nearest truck stop or perhaps even drive to their destination.

So I inflate my Potenzas above 44psi and don't give it a thought. However, as the pressures get higher the mpg gains for each additional psi diminish, so I try to strike a balance.

[satchel]

The photo is the front driver's side BTW.
I'm not at all worried about a blowout due to the 60# inflation alone. Tire defect or road hazard but not the 60#. I unwisely passed on a washed out shoulder recently and hit the exposed concrete lip of a cross road hard. If an impact was going to blow them that should have done it! Jarred the skirts loose but didn't hurt the tires(or alignment).
Coasting and mpg performance and handling are markedly better at this inflation.
My drives are 200-600 miles on mostly good roads. KDOT has done a great job over the years. I can tell the instant I cross the border into Nebraska, suddenly feels like driving down railroad ties. Missouri used to be bad but MODOT has done some good work. Still, no forgiveness for Quantrill.
Dodge those gators here too, one of the reasons I won't draft semis(except at a distance).
I too have seen the built strong enough to take 200# statement.
Crx_rogus you obviously wouldn't be comfortable at 60# but you should at least try the max sidewall for the improved handling and mpg over the manufacturer's spongey suggestion.

[crx_rogus]

Originally Posted by satchel

...I unwisely passed on a washed out shoulder recently and hit the exposed concrete lip of a cross road hard. If an impact was going to blow them that should have done it! Jarred the skirts loose but didn't hurt the tires(or alignment). ... I too have seen the built strong enough to take 200# statement.
Crx_rogus you obviously wouldn't be comfortable at 60# but you should at least try the max sidewall for the improved handling and mpg over the manufacturer's spongey suggestion.

One of the first things I did with the car is get the front tires up to 44psi, rears to 40psi.

If the tires can take being smashed into a concrete road lip at 60 psi, then up to 60F/50R on my Insight they go!

Re: tread picture
The fact that the original casting tits or whatever you want to call them are still on the tire is very impressive... zero sidewall rollover on a 65-series tire over 22k miles. Never seen that before! The totally even treadwear is odd for being run at such pressures, but maybe that's related to the narrow tread width? 60psi clearly causes zero uneven tread wear issues with the RE92s.

I have read of highly inflated tires bouncing around on bumps while braking enough to trigger the ABS, thereby turning off the regen, causing the car to feel like it's suddenly lunging forward when you're trying to stop. If I start encountering that, I'll back the front pressures down a bit. (But the speeds I remember it being reported as happening at are about where regen in 2nd falls away anyway...)

red1dr -
That's a very useful bit of data there. Zero harm if kept to rated max then, and probably easier on the tires.

Another part of the reason for my caution is that I want to explore the max corning behavior of the Insight the same way I did with CRXes before (if nowhere near as often), and I'm trying to get a handle on what stress level they can take. It does sound like there's insignificant chances of a blowout at 60psi from such driving, and steering response would be much quicker (... and my other comments about the power steering being just interference would be even more relevant!).

Thanks much for the feedback.