Top Speed worries?

[dannyd2450]

TM says we should max out at 55MPH, but my M923 will hit about 67 (GPS). RPMs all stay within range; other than killing fuel, what harm is this doing (or not doing)?

 

[BKubu]

Check the speed rating on the tires. I assume from your post you are driving an M923, which would imply that it has 1100s on it, right? G177s? If so, they probably could handle the speed. I don't believe the super singles are rated for that kind of speed. I have seen on the sidewalls of the some of the tires a warning: MAXIMUM SPEED 55 MPH. I believe that was on the Goodyear super singles. Others may have the warning, too...I just have not looked for it opn the Michelin XLs or XZLs.

 

[dannyd2450]

You hit that one perfectly.. They are Michelin's and have a recommended top speed of 62. What are your thoughts of the transmission / axels, etc?

 

[doghead]

Are your tires new and in perfect condition? If not, I'd "prorate" that speed down a bit.

Handling characteristics at 55 may be a realistic reason why the speed is listed as maximum.

 

[61sleepercab]

The other side of the coin of going fast is that YOU HAVE TO STOP IT SOME TIME!!! The faster you go the longer your stopping distance and the distance your truck will cover in the time between seeing trouble and getting the brake pedal down. Going 60 from 50 is a 20% increase in speed and wind resistance really starts killing mpg above 55 or so. Some major trucking lines are cutting trucks back to 60-65 mph on runs to save fuel.
A old mechanic told me while running an International 2 ton that she could run 50 mph forever but living on borrowed time at 60-65. From my street stock motor dirt tract friends who push higher than normal rpm on stock engines, they either spit out a valve head that can go everywhere in the upper block or rod bearings seize and spin in the rod or the rod bolts or rods themselves give up and all heck breaks out.

I would rather start out a little earlier on a trip than push the truck to its limits just to save time or get there faster. My 5 ton on stock 20" regular tires smooths out out at 45-50mph and purrs like a kitten and I do not have a white knuckle grip on the wheel or start hearing imaginary death rattles from the power train . Mark

 

[Suprman]

If you have an M923A2 the engine is governed to around 2200 rpms at that speed you are around 67mph. That motor can safely rev into the 3500 rpms range but your drivetrain is only rated at 3000. I wouldnt advise it. Playing around for a short spurt on open dead highway I hit 80 something and killed a ctis hub seal in the process. I can tell you it smoothed out after 70.
Will

 

[RustyM923]

I got up to 67mph (on the GPS) once. The ABS light came on and didn't go off til a week later. Pinion seal leak now.

55 and stay alive (IMHO)

 

[Triple C]

This is what you need to worry about. I didn't pay attention to the 55mph rating either and this was on front. Believe me, it is a quick learning curve.

 

[Floridianson]

One would think that with the age of these tires inless you just bought brand new rubber then high speeds you will be pushing your luck. Just because the tires look good from the outside does not mean they are not drying out.

 

[Vintage iron]

I do a lot of driving in my 5 tons. I had a few different ones. I cruise a 1900 Rpm/55 Mph -/+ on the highway and drive around in fourth gear around town. I always use caution and adjust my speed to the driving situation. I have even driven my M813 with 1600's in Boston traffic. If you are going to drive on long trips or at high speed always check you truck over before, during and after your trip. Small signs of trouble can save you from big trouble. Have fun and motor on!

 

[emr]

These are tactical trucks, as fast as you can go is not a good choice, Like said above, over 60 is a seriously dangerous thing to do. You may well get away with it for ever , but the ods are not everybody will, once these trucks let go on the road, I don't care how awesome someone is, It will be luck if no one get hurt or killed. these big tires hop, and slide. thanks for asking. Nothing on these trucks is designed for speed period.

 

[73m819]

A FRONT blow out is a REAL attention getter, which in my case no one got hurt just the 819 got busted up (air born landings tend to break things)