Thread: Info needed: Building a repro LRDG 1940 Chev.
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Old 02-03-19, 04:27
Bob Carriere Bob Carriere is offline
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Join Date: Mar 2003
Location: Hammond, Ontario
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Default Answers to Tony then Hanno....

Hi Tony

On posting #9 that rim when enlarged shows signs of being a rim with an outside ring........ I have no doubt the rim has been modified and possibly mounted backwards....... if it is mounted on 10 bolts then they have to be mounted to a hub/adapter of unknown size as the actual adapter mounts to the brake drum with only five bolts of different diameter to the 7 1/4 diam 10 bolt pattern............ it is unusual and would not be surprised if it was 18 inches....and here is why I think so

If you look at my mock up posting the brake drum is fully cleared of the CMP rim. The inside diameter of the CMP rim is 15 + inches as it is slopped a few degrees as you get closer to the center....and we measured the stock brake drum which measure a hair over 14 iinches....leaving less than a half inch clearance between rim and drum....The other is that the front picture fo Rick Cove's repro shows clearly the front brake drums outside the front rms and his brake drums are ribbed/fins....... which is a variety of brake drums used on those vehicles by GM.

Another factoid...... just got a hold of two new 1940 Chevrolet and Maple Leaf parts book and in the listings.....although only one size hub/adapter of 4 1/4 inch is listed they have four different offset rims sizes ranging from 4 1/8 to 5 1/4 offsets on the rim center parts....all in 20 inches. My spare rim and spare axle has the inside part of the rim even with the brake plate ...this to me implies that it is the smallest offset......... Philippe in Florida has the opposite on his 1939 Chev and his rim clears the brake drum completely. so GM played with the track width by varying the offset of the wheels and the greater offset seems to be on the larger truck axles....series 15 to 18 had the wide offset....... they were not to concerned with the overloading of the bearings. Honestly I am concerned with the old technology and will search to see if I can find roller bearing that fits that particular hub/adapter....... too much unsprung weight to far outboard for my taste.

Hanno.... I agree they are not split rim as far as I can tell.....but have a closer look at the rim/ring edge........looks to me to be a 2 or 3 part rim of that period with the tire pressure locking the rim bead....

The tight fit of the GM brake drum and the split CMP rim may partly explain the reason for using a two part 18 inch rim......18 inches rim where popular in that period and Ford trucks did use them as well.

It would seem possible that a regular 16 in. CMP rim would fit by reversing the location of my adapter plate and mount the rim backwards.... in any event I will play with the mockup to see if I can have the wheel mounted with less overhang..... yet not quite overlap the brake drum...... might be able to gain an inch or so......

Thanks for the interest and questions in this challenging project.

Now looking at finding mid to late 40s production Chev/Maple Leaf 3 ton front axle...... and Ford also had 3 ton I beam front axles...... but only after this snow cover finally melts.......

Bob C
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Bob Carriere....B.T.B
C15a Cab 11
Hammond, Ontario
Canada
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