At some point during 2009 I began vaguely thinking about replacing
the hardworking Hydroedges on the Prius. They had already served a
solid 70,000 or more miles -- and that despite the feathering effects of a
minor misalignment in a rear wheel, and a very slow recovery across the
right-side pair had been ongoing once that was corrected. Then one of them
suffered a fatal puncture on one of that summer's roadtrips, pronounced too
close to the sidewall to reliably patch -- leading to having one oddball
cheap-ass Korean tire on the car and the three remaining Hydroedges. Despite
the odd tire still being fairly new, maybe at this point it was just time to
employ the bigger hammer and get a whole new set. Among other advantages,
it would fix the serious mismatch in the
wheel speed delta indicator caused
by the one odd tire being a slightly different size.
This was helped along by the parental collective wanting to supply a nice holiday-time present, so the decision was made to forgo the remaining service life in the old tires and swap to something newer and hopefully better. Not that the Hydroedges weren't fine tires in their own right, but there seemed to be some interesting new options emerging on the market. In fortuitous synchrony with this idea being hatched, a fellow participant in one of the forums I'm on had read about my scary experiences with prematurely degenerating valve stems and a brief mention of having tire trouble on the recent road trip, and offered to send me gratis a set of four of the type of metal bolt-in valve stems I had favorably mentioned in the safety writeup. Said it wasn't any particular trouble or expense, he had 'em laying around. A while later, a package containing four Milton 409 type valve assemblies showed up in the mail. "Top shelf stuff", he said in a followup. |
This was fascinating, but having never actually used such things yet it
was unclear to me where to install the two rubber gaskets. [Well, if I had
actually looked up the catalog page earlier in the game, I could have
probably figured it out.] My forum buddy quickly set me straight -- only
*one* is used at installation, and which one depends on the size of the rim
hole. Okay, now it was bleedin' obvious -- I'd only need the one with the
.453" diameter flange, as rims with the larger holes are fairly rare.
At the same time, having a collection of new stems recalled a tiny bit of concern about how firmly the little valve cores had been installed. At one point in the past I had discovered [by observing a minor straight-line anomaly developing in the aforementioned "green diamond", in fact] that at least one of my present rubber valve stems had been leaking just a little -- because the valve body itself wasn't tightened into the stem properly and a tiny bleed of air was getting out past that and the cap. Easy enough to fix with a valve tool at the time, but I thought it prudent to check that on these too. That led to total disassembly and inspection of all four. | |
Well, one of these things was not like the others. Its core body seal came out black instead of red, and somewhere I seem to recall a mention that red core seals indicate higher pressure tolerance than other colors. I cannot substantiate that but there are hints about different colors matched to different applications and conditions in some of the material on Schrader's web site -- either way, it was already clear that there was something odd about this third stem. |
Fast forward to December, which found me temporarily in much warmer climates. After talking with the guys at the local Pit Stop Auto, we agreed that they'd have no problem using my supplied metal stems and letting me go into the shop areas and work with the tech to exchange some Prius-related hints for a little more info about the tire-mounting process. I never really documented the first time when the Hydroedges were installed, but wanted to collect a little more info on this go-round. Once I demonstrated that I pretty much knew what I was talking about, they were fine with it. More shops need to operate like this -- most of them have fallen victim to "too many lawyers" disease and are terrified of letting customers anywhere near work in progress. We scheduled a day after the tires would be ordered and delivered when I'd come back and have it done. |
The new stem and its .453" collar fit *perfectly*, almost like it was designed for that rim, with plenty of room for the inner stem plate to seat. |
The washer and nut on the other side fit with equivalent dimensional elegance ... |
... and the whole thing gave a much lower height profile than standard rubber stems. |
Meanwhile, Ian was already mounting up the new tires -- here letting the machine squidge the bead over the rim lip ... |
... and then seating the bead with a bit of air pressure. As the final gap closed, the bead snapped up into the seating area with a quite energetic pop. |
The balancer's test spin doesn't take very long; if you blink you'd miss it. |
With the car finally back on tarmac-firma, I settled our paperwork [including
handing the guys at the desk a printout of my valvestem rant and a couple
of flyers], and headed off.
I could tell the difference within a hundred yards after pulling out of
the shop driveway. These things really *roll*. My glides immediately seemed
to be going longer, using momentum much more effectively. The car now felt
like a 3,000 pound object sitting on an air table -- once the effort was
applied to get it moving, it just wanted to keep going forever. And the
*lack* of tread noise was a welcome relief from the rumbling of the
Hydroedges I'd gotten so used to, not to mention the fact that the green
diamond was once again usefully functional with the top and bottom LEDs
almost invariant on a straight road.
With around-town average MPG reaching into the 70s on those warm flatland local roads over the next few days, I figured I'd made a good choice. |