Yes, I've been a fan of the Chieftain's contributions for some time. Quite where he got that 'anatomical' picture of the Cromwell's suspension, I don't know; but it's very revealing. What he doesn't say, though, is that the armour plate that makes the Cromwell's suspension system hard to get at for maintenance purposes, also supplied extra protection for the crew in their cramped fighting compartment (trade off of space for safety),
and protection for the crucial suspension components too.
Here's a bit more info on the trials. It shows that the Cromwell of that time (still under development and with oil seal leak issues, and other problems that should have been rectified), needed twice the number of man-hours
in maintenance than the Sherman. However, in action, the Cromwell offered better crew protection (up to 100mm armour in later iterations, even without the sloped glacis- and comparable with the Tiger-), was infinitely faster and more manoeuvrable, and had had the same gun, effectively as the Sherman. Better yet, it didn't have the skyscraper profile of the Sherman; and so it was much harder to hit...except when trapped in a street
in Normandy township (infamously..
). Apparently, the six-pounder (57mm) anti-tank gun it was originally fitted with, had better penetrating capabilities than the Sherman 75mm, but lacked an effective HE shell. The bored out 6-pounder then morphed into a 75mm with the same characteristics as the Sherman: a 'doorknocker', when meeting the Tiger...
Trials:
"...The first real field test of the design was carried out in August–September 1943, when examples of the Centaur, Cromwell, Sherman M4A2 (diesel engine) and Sherman M4A4 (multi-bank petrol engine) were all tested in Exercise Dracula, a 2,000 mile long trip around Britain. The Shermans proved to be the most reliable, by far, requiring 420 hours of specialist fitter attention over a total distance travelled of 13,986 miles (22,508 km). This corresponds to 0.03 hours per mile. In comparison, the Cromwells drove 11,582 miles (18,639 km) and required 814 hours, or 0.07 hours per mile. The Centaur managed only 8,492 miles (13,667 km) due to constant breakdown, and required 742 hours, or 0.087 hours per mile..." (Quoted from Wikiwand, in turn a reference to David Fletcher's 'Cromwell Cruiser Tank 1942-50')
The Cromwell and Centaur were given additional time to work out these problems. The Cromwell's problems were mostly related to oil leaks and brake and clutch failures, an observer noting that these were well-known and should already have been corrected. The crews, however, expressed their love for the design, and especially its speed and handling.
On the plus side though:
"...The gearbox had five forward and one reverse gears. The first gear was for "confined spaces, on steep inclines or...sharp turns". The transmission was the new Merrit-Brown Z.5, which offered differential steering without clutching or braking, a major advance on previous designs. It gave the Cromwell superb maneuverability, with only the German Tiger I, using a similar design, able to match it..." (From Wikiwand)
This 40MPH tank could also outmanoeuvre the opposition with speed and agility. Final drive reduced top speed to 32 MPH to preserve the gearboxes, but even so apparently on one occasion:
"..Cromwell was the fastest British tank to serve in the Second World War, with a top speed of 40 mph (64 km/h).[18] This speed was extremely beneficial in both attack and defence, outmanoeuvring opponents. At least one case is known of vehicle commanders using the vehicles fast speed to jump large gaps - In Holland, a troop of three Cromwells was able to leap a 20 ft wide canal when surprised by enemy forces.."
What puzzles me, though, is that during the war they were unable to come up with a turret for it that could accommodate either the 17-pounder, or the Vickers 75mm (equivalent of the German 75mm on the Panther).
Yet after the War, they mounted a 20-pounder (3.3in) on it and sold the tank to the Jordanians, the Austrians, and many others as the FV 4101. I guess it's just difficult to research, develop and introduce not merely a new tank, but all manner of fighting vehicles (Ships, Aircraft, tanks, etc..) in the middle of a major war; not simply in Europe but globally.
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.
). Just leafing idly though Youtube webpages, when I came across this fascinating little clip showing the Cromwell and Centaur variants competing with a Sherman M4 on an obstacle course. If only the 17- pounder had fitted the Cromwell. Pity we had to wait for the Cromwell to morph into the Comet, 
The trial would have been even more revealing with sound, but alas it's not there. 
Benefit of (long) hindsight, eh? Here's the Cromwell rebranded as the Charioteer FV 4101, sporting that massive 20-Pounder. Crazy. Yet, the 17-pounder was a no-go. 
This Cromwell variant, with the massive appendage, saw active service well into the 1960s and beyond; mostly in the Middle East. The long narrow elongated turret was the answer, and echoed German 'narrow' turret design from the War's end. It was conceived and built by Robinson and Kershaw of Cheshire. Or maybe by Gandalf and his magic staff!
