25 pounder rim question

[Keith Webb]

Not sure where to put this one - it may be better in the armour section but of course the 25 pounders were towed by my favourite CMP types...
I was asked yesterday by a friend from the RSL about the rim size of 25 pounders - he said one of the RSL sub branches is restoring it's 25 pounder and managed to purchase two good 16" tyres for it only to find the rim size is not 6.00 but a quarter of an inch larger.
Does this make sense to anyone? I would have thought the 16" split rims were all the same size.

[Phil Waterman]

Once again, I believe the issue of infamous 0 degree vs. 7 degree rim raises its ugly head. There was a thread on this in the old forum that explains this issue. Goeff can you lead us back to that thread?

[Keith Webb]

I recall something about that now you mention it.

[Geoff Winnington-Ball (RIP)]

Guys, I can't remember either, although what Phil said rings a bell... but the old forum's still up - if you do a Google search with various keywords, and SPECIFYING 'network54.com', you should be able to find it. Just remember to click on the 'cached' page rather than the true page.

I'll look later if you don't find it first.

G.

[Hanno Spoelstra]

Originally posted by Keith Webb
...two good 16" tyres for it only to find the rim size is not 6.00 but a quarter of an inch larger.

I've wondered before if the source of this enigma lies in differences in tyre diameter, not so much in a bead and /or rim taper. The quarter inch you mention is the same amount someone milled off his rims to get his tyres to fit.

Originally posted by Phil Waterman
Once again, I believe the issue of infamous 0 degree vs. 7 degree rim raises its ugly head. There was a thread on this in the old forum that explains this issue.

See my web page on 9.00-16 tyres and follow the link to the various forum threads, mailing list messages and web pages.

The jury still seems to be out on this issue, though. We need to assemble a 16" Rim Committee to see this solved for once and all

[Gord Falk]

I checked my 1944 Chev 15cwt wireless that last served with the Royals Canadian School of Artillery. The truck is sitting on what I believe are 25 pounder rims, not the split rim as on a CMP but with a locking ring. The tire size is 900X16. My questions is do 25 pounder rims fit on a CMP or are these some other type of wheel.

Gord Falk

[Richard Farrant]

Originally posted by Gord Falk
I checked my 1944 Chev 15cwt wireless that last served with the Royals Canadian School of Artillery. The truck is sitting on what I believe are 25 pounder rims, not the split rim as on a CMP but with a locking ring. The tire size is 900X16. My questions is do 25 pounder rims fit on a CMP or are these some other type of wheel.

Gord Falk

Gord,
The 25 pdr wheels have the same stud configuration as the CMP and British 15 cwt trucks. I actually used two 750-20 wheels temporarily on one whilst restoring it. This rim saga is puzzling as I have measured several rims on 15 cwt trucks and note that a number of the wheels are marked RF (runflat) and new Trackgrip tyres fit without much of a problem.

Richard

[Wayne Henderson]

The 25 pounder rim has the same stud patten as the CMP rim.
A CMP rim will fit on the 25 but not visa versa as the 25 pdr rim is fitted with wire lugs on both outer surfaces of the rim and will foul against the brake drum and hub.
The correct original tyre size for the 25 pounder is an 8.75 x 16 bar tread, s patten etc but as photos show, and latter directives dictate, road tyres were fitted in the latter war years.
When the 25 is fitted with 900 x 16 tyres it just fits on to the firing platform.
At the Royal Australian Artillery Historical Society, we fit 900 x 16 lug patten tyres to all restored 25 pdrs because of the availability. We even fitted ferret run flats to one particular gun, (army workshop) pressed on and held by the locking rim.