Thursday, March 12, 2009

Our favorite truck shop

We are at PEDCO, in Santa Fe Springs, California (map). Long-time readers will know that we've been here several times before, twice for over a week each time as our Detroit Diesel engine was overhauled "in frame."

The guys over at Eagle Tire in Riverside were great, getting us in and out quickly and efficiently. When we pulled the old drivers off, the inner shoulders of the inside tires were worn to the belts, with progressively less wear moving to the outer shoulder.

Likewise, the outers had more shoulder wear on their inside shoulders as well. What this means, of course, is that our axle is bowed slightly in the middle -- not surprising, as we have nearly 24,000 pounds of load on it.

There really isn't anything that can be done about this, short of replacing the whole drive axle. If I could find a way to shift 3,000 pounds to the tag axle, which, at just 11,000 pounds, is that far under its rated capacity of over 14,000, we'd get better wear on the expensive drive tires, not to mention less wear and tear on all the components in the axle. The only way I know to do that would be to go to larger diameter air bags on the tag -- a non-trivial undertaking.

What we have decided to do moving forward, though, is to take the trouble to rotate the outer drivers to the inner wheels and vice-versa periodically. In the past, we've only swapped the wheels side-for side, because we have steel inner wheels and aluminum outers. Rotating the tires inner-to-outer will mean dismounting and remounting all four tires each time, but we can try to even the wear across the shoulders that way.

The new Bridgestone M711's look just as butch as the last set did back when they were new. There is something about a Mud & Snow rated tire that just looks all business.

Given the inevitable shoulder wear, and the inherent vibration of the block treads, we opted not to spin-balance the drivers, and we also did away with the Equal powder that we had been using in those positions.

The steer tires were very badly cupped, as we knew from the bone-jarring ride. I took dozens of photos of the damage, in case we need to analyze the patterns as part of diagnosing whatever is causing this rapid and irregular wear.

One benefit of the new 12R22.5 Firestones that replaced them was immediately noticeable: the smaller contact patch made low-speed steering much more effortless.

Riding over here on the new shoes was a velvet experience -- smooth as glass, and, with the square tires gone, we could once again enjoy the legendary Neoplan ride; no other bus is as smooth, in our experience. The new block-tread drivers are "singing" again, which is just barely noticeable in the cockpit. The old ones were so worn, they were as quiet as rib tires.

After we landed here at PEDCO, we checked in with the office, then settled in for the night in an empty spot across the street (map). Proprietors Virgil and Rachel Cooley were just about to go for a late lunch with customers Steve and Shawna, who were picking up a monster engine for, I think, a show truck, and they invited us along. It was great catching up with the Cooleys, and we really enjoyed meeting Steve and Shawna, who seem to have irons in a lot of interesting fires.

Despite rumblings that they might not get to us until tomorrow, we had a knock on the door around 9 this morning, and were backed into the shop half an hour later. Well, more precisely, we backed in to the fenced yard next to the shop, where we can be comfortable on board for several days, if needed. During one of our visits here, the yard was occupied with another half-dismantled truck, and we ended up in an inside bay, where we lived for a week.

They spent the rest of the day tracking down and rectifying a dozen or so oil leaks, a sort of trademark of two-stroke Detroits. A good deal of oil has been oozing out around the alternator housing, which was cause for concern. We put tremendous loads on our oil-cooled alternator, typically 6 kilowatts or so, and we need to watch for early signs of bearing failure or other issues, since catastrophic failure of the unit can easily do serious damage to the engine as well. After some consultations, the determination was that the oil seepage was not a harbinger of imminent failure, and they did not feel the alternator needed to come out for either rebuild or inspection. Good thing, because it weighs over 100 pounds, and would need to be wrestled through the bedroom hatch.

What they did not find is any indication of how we are getting high silicon levels in the oil. While they had the airbox covers off they inspected the liners and rings, and all looked normal. Tomorrow, they'll change the oil, pulling another sample for analysis, and inspect the transmission, which seems to be seeping expensive synthetic fluid at an increased rate of late.

With any luck, we should be finished up here by the end of the day tomorrow.


  1. That is some serious looking tire wear. Glad you are getting some new ones.

  2. Looks like you got every penny out of those tires you could. Be safe. All the Best, M&C

  3. Outside wear on both edges of the steering tire could indicate it's been running underinflated for the load it's handling.

  4. @Spyderman: I've had some direct messages suggesting the same thing, so I will repeat my response here:

    That's a good guess, but the tires were never, ever run below the recommended inflation pressure for the load, per the manufacturer's load and inflation tables. These 315's are rated to carry our 6,400lbs (per side) at just 85psi. They have always been run at or above 95. When the cupping got so bad we could hardly stand it, we went all the way to 120psi, just to ride on a little more of the less-cupped center tread and less of the more-cupped shoulders.

    We have electronic pressure and temperature monitors in the wheels, so we are quite certain that the pressure has always been above limits.

    Most of the wear is on the outside shoulder, which is normally indicative of a toe-in problem. But the cupping (irregular wear)is of much greater concern. The cupping has been happening much sooner than the shoulder wear.

    I expect the shoulder wear to be less of a problem with the 12R22.5 tires, since the narrower tread will mean less scrubbing just due to normal steering activity.

    The way bus fleets deal with the inevitable shoulder wear on steer tires is to rotate them to the drive axle, which tends to square them off. We can't do that, since we run ribs on the steers and traction tires on the drivers.

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  6. It looks like you have a history of very bad tire issues. I suggest you consult with a frame/alignment shop.

  7. my bus tires looked like that.

    after my 4000 miles trip, I realized that I was running way low on bearing oil. I don't know if the damage was done, but I refilled it and seeing if it smoothes itself out.

    what was your previous tire size?

  8. @Anonymous: We have greased, rather than oiled bearings. One thing we just had done at Freightliner was to have the bearings repacked.

    We've always had 12R22.5 tires on all positions except the steer axle. We had changed those to 315/80R22.5 a couple years ago, and now we've changed back to 12R22.5

  9. on mine, there is a plastic cap with a rubber plug, on the front rim, with the indicator for minimum oil level.

    it's supposed to have gear oil, 90-140w. I replaces/filled it with synthetic oil, and the wear seem a little less severe.


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