WARNING: DO NOT OVERPRESSURIZE YOKOHAMA AVID ENVIGOR TIRES
I had hoped to give a detailed writeup on my troubles with the Yokohams, but this convoluted summary will have to do, as I'm leaving town next week for a month.
As some of you remember, I'd been running my tires variously at 60psi, 51psi, 44psi, and the OEM-recommended 36psi. My reasoning for overinflation -
1. Reduce rolling resistance
2. Improve handling
3. Reduce sidewall flexing leading to tire heating
No problem running at 60psi with the OEM Dunlop ENASaves for two years - wore out the first set (evenly) at 23K miles.
Replaced the tires on Mitsi
(my original i-MiEV) with Yokohama AVID ENVigor and continued experimenting with tire pressures, eventually settling on 44psi after I became convinced that the higher tire pressure did not noticeably improve efficiency.
My second i-MiEV Mitti
already had the rear tires replaced with Yokohamas (previous owner had damaged tire and replaced both rears with Yokos). With this car, I also experimented with tire pressures before settling down on 44psi.
Long story short: in hot weather a short while ago, the right rear Yokohama on Mitti catastrophically had tread separation at around 55mph, whapping and damaging the bumper. The tire (inflated to 44psi) DID NOT DEFLATE. This happened 50 miles from home and luckily I had my two Gen1 Insight spacesavers + jack onboard and was able to replace both tires. Went home using back roads with dashboard lit up like a Christmas tree (due to tires of unequal size front to back) but everything working fine once the car's ASC or ABS or whatever got over trying to react to the weird tire diameter. Replacing the tires with OEM Dunlops took away all the warnings. The failed tires had about 15K miles on them.
Shortly thereafter, Mitsi
(my original i-MiEV) developed a rumbling noise in the front after about 18K miles on the Yokos (lots of treadwear). The left front tire tread had started a bubble. No sooner had I replaced the two front tires with OEM Dunlops that a rumble in the right rear started - same thing, a bubble. Replaced tires. Now have all my cars running on OEM Dunlop ENASaves, the only difference being a quieter ride than the Yokos and the car's range now appears to be identical amongst all three cars, despite wildly different battery ages. Can't tell any difference in handling. I'm running all tires at 44psi, despite Mitsubishi's recommended 36psi.
So, three out of six Yokohama AVID ENVigors had tread separation, two of which I caught before the tread fell apart.
Was my previous driving at 60psi the cause? Probably a contributor. I didn't keep records so I don't know how many miles I put on the tires at what pressures. These are the first tires I've experienced failure with after ten years of running higher-than-allowable pressures in both the Gen1 Honda Insights (special ultra-low-rolling-resistance Bridgestone Potenza RE92) and i-MiEVs.Let this serve as a warning.
Once again, maximum pressure allowable by tire manufacturer is 51 psi, with i-MiEV recommended pressure being 36psi
. Don, you can now say you told me so...