Tire choice discussions seem to run through many of the larger truck threads and the 916A1 is no exception. The difference is there seem to be no defenders of the original issue rubber on Freightliners with their highway style tread. The one that I picked up from GL, for no apparent reason, had recently had its originals swapped for a new set of G177's in 11:00 X 20. A familiar size with a good mud/snow tread. I happily ran them through two winters while plotting their demise.
Going to a few shows and hauling some good weight determined two problems. Big truck, big wheel wells...small tires = something wrong. More engaging problem was the old RPM and MPH curves. The Detroit 60 will comfortably run at its rated max RPM giving a road speed of about 58 MPH. Fast enough for load carrying on two lane blacktop, but silly in terms of the RPM expended, when you have 400 HP available. So, change all three ring and pinion sets as some do, or swap the Allison for a later model with OD in top. Both good ideas, expensive for sure, but they wouldn't help with problem one. So bigger tires were in order.
Surplus choices of sufficiently larger rubber come in two sizes 14 and 16. I played around mounting trial tires in front and rear positions, checking the body interference, as the A1 is not as wide open as the A0. The 16's would require considerable adjustment of the front fenders, rear storage boxes, and generally looked a little out of place. The 14's however looked just like they were the ones meant to be issued with the truck. Lower front fender panel was moved straight back a few inches, and then add a few inches to the bottom of your boots and you are ready to climb aboard.
The fit was good, 14 Michelins on 5 ton combat wheels. First run down the road was the real fun. Was just like when back in the day I got a set of 4.88 gears right at the Dodge truck dealer for my M37, to replace the stock 5.83's..... found a used dial gauge, an inch pound torque wrench, and was in business. The effective gear ratio change in the Freightliner is equivalent to that, going from the 11:00's to the 14's is .877. Translated that means your top gear is equivalent to an OD of that ratio. This spreads your transmission gears out so that you haven't run through them all in the first half block. The real numbers mean 50 MPH before is now 57. Or for my running I can travel 50/55 loaded with reduced RPM and some extra headroom for safety and planning ahead down the road.
Trailer hook-up sets you higher at the nose, not a problem for the M172A1, as it was pulled by both the M123 and the M911. Run down the road with empty trailer was stable on the singles, and again much better match with the gear box and tire size. Next, the VT show last weekend provided an opportunity to work up some more loading and check the results.
John
Going to a few shows and hauling some good weight determined two problems. Big truck, big wheel wells...small tires = something wrong. More engaging problem was the old RPM and MPH curves. The Detroit 60 will comfortably run at its rated max RPM giving a road speed of about 58 MPH. Fast enough for load carrying on two lane blacktop, but silly in terms of the RPM expended, when you have 400 HP available. So, change all three ring and pinion sets as some do, or swap the Allison for a later model with OD in top. Both good ideas, expensive for sure, but they wouldn't help with problem one. So bigger tires were in order.
Surplus choices of sufficiently larger rubber come in two sizes 14 and 16. I played around mounting trial tires in front and rear positions, checking the body interference, as the A1 is not as wide open as the A0. The 16's would require considerable adjustment of the front fenders, rear storage boxes, and generally looked a little out of place. The 14's however looked just like they were the ones meant to be issued with the truck. Lower front fender panel was moved straight back a few inches, and then add a few inches to the bottom of your boots and you are ready to climb aboard.
The fit was good, 14 Michelins on 5 ton combat wheels. First run down the road was the real fun. Was just like when back in the day I got a set of 4.88 gears right at the Dodge truck dealer for my M37, to replace the stock 5.83's..... found a used dial gauge, an inch pound torque wrench, and was in business. The effective gear ratio change in the Freightliner is equivalent to that, going from the 11:00's to the 14's is .877. Translated that means your top gear is equivalent to an OD of that ratio. This spreads your transmission gears out so that you haven't run through them all in the first half block. The real numbers mean 50 MPH before is now 57. Or for my running I can travel 50/55 loaded with reduced RPM and some extra headroom for safety and planning ahead down the road.
Trailer hook-up sets you higher at the nose, not a problem for the M172A1, as it was pulled by both the M123 and the M911. Run down the road with empty trailer was stable on the singles, and again much better match with the gear box and tire size. Next, the VT show last weekend provided an opportunity to work up some more loading and check the results.
John
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