Info needed: Streetable CMP truck

[Hanno Spoelstra]

Originally Posted by Grant Bowker

Understood that original CMP boosters are about as common as NOS Chevrolet master cylinders...
For the style shown, you will need to check for available space in line with the brake pedal (easier to find this space on a C15 without the transfer case to get in the way...). Another option is a remotely mounted booster, mounted to the outside of the frame - sometimes fitted between the supports for the step (at least partly hidden by the battery box).

The first modern brake booster I saw fitted on a CMP was on John Hotson’s C30. He modified his trucks to make them suitable for modern traffic. Look where he managed to fit it:

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[Bob Carriere]

A top speed of 55 mph with standard C15a axle gear ratio.......

My 261 stock rebuilt gives me 44 mph with the 10:50 Chevron tyres and that is pushing near 2990 RPM........

Now my speedometer has not been calibrated using a GPS reading and I think my rpm meter is reasonably close to a testing separate rpm meter gauge.

Planning to calibrate the NOS GMC speedo with a telephone app this Spring.''I do have a mounted set of NOS 9:00 x16 Michelin that have not tried yet.. I believe from all account thats the radial are far smoother b ut not sure they would increase the top speed unless the rolling diameter is greater than the 10:50.......

How do I get more top speed without pushing the 261 much over 3000 rpm????

44 mph is a handful not sure I would feel comfortable at 55.......

Note that non of my tires have ever been balanced yet....... one truck tire shop would not tackle the 10:50 on my CMP rims ..... have yet to check with Benson truck shop....

Properly adjusted new brake linings on radius linings matched to turned drums seems quite adequate.

Comments/suggestions welcome before I paint RED racing stripes on my CMP.......

[Bob Phillips]

I think Bob C. has preempted my question about roadspeeds on stock 15cwt drivelines. I have had severaal roadworthy CMPs over the years and could never achieve speeds any where near 50mph without fear of engine destruction or vehicle instability resulting in catastrophe.
I have 20 inch wheels and tires on my current 15cwt chev it it wont do 50mph
without fear of imminent disaster.
So what experience do others have on this question?

[chris vickery]

60MPH in a 12 cab CMP. Not the most intelligent choice, but back in the day that’s what she could do.. Was it safe? Foolhardy? Probably

[Harry Moon]

in 2005 coming home on our first big freedom convoy I had on a set of 1100x20 on my C15A, we hit about 65 mph when we just had to pull out and pass an LSVW. Only time I ran the big tires on the C15A.
I regularly cruise at 50 mph (gps confirmed) in my C60L with 1100x20's with the 235 with Fentons.

[Grant Bowker]

Canada's Fighting Vehicles lists maximum speeds between 40 and 50 MPH. The maximums do vary within the same basic model (eg. C60) which I assume may be due to weight as to the best of my knowledge all C60 had the same power, gearing and tires.

[Harry Moon]

Originally Posted by Grant Bowker

Canada's Fighting Vehicles lists maximum speeds between 40 and 50 MPH. The maximums do vary within the same basic model (eg. C60) which I assume may be due to weight as to the best of my knowledge all C60 had the same power, gearing and tires.

I imagine with the 216 and 10.50x20 tires that is the upper limit.
Way more useable RPM with the 235 and a few MPH from the 1100 tires.