I find this number extremely difficult to believe. It is probably not tractable in the sense we use for the T-90 number you give...but may be a theoretical "no slip" max on the test range ramp. Looking at Type 15, the CoG also seems fairly low to aid this.
In a passing convo, an ex abrams tanker told me about all kind of real world limitations to what the abrams stated specs are on paper from the test range its qualified on after production.
These are all presented to the actual crews for training and then deployment...prioritised even by likeliest matrix intersection of conditions...it has taken decades of field experience to acquire.
I too find that very hard to believe! I have no idea what test standards Chinese follow for certification, if we knew that would give detailed account of test procedure.
Most of Military that produce/ oversee military vehicle production , certification and export have made their own test standards.
Russia now use standards that are very close to ECE type approval standards with little bit of tinkering, since they export their vehicles and equipment far and wide, the customer need to have grasp of what is he buying and who has certified the seller's claims.
US now has a separate command :US test and evaluation command that makes and regulates Military equipment and vehicle test standard . Most of them are very close copy of Commercial SAE standards.
Since China is also trying hard to grab a share of defence equipment market, it is likely that they are either already following some global standards or are in process of doing so.
Anyway, max gradability for military vehicles is a complex test and these days is performed at a specialised variable ramp dynamometer and not on actual ground. As soil, rock, water content of soil, temperature etc can all vary from country to country, a vehicle tested on either cemented ramp or ground may not perform as advertised while bought by some client country.
So in recent years, most manufacturers have turned to SAE certified Dynamometers which present same condition for testing throughout the world.
In military vehicles(Russian) not only the vehicle needs to go up and down the advertised max angle, but it needs to sustain 3.2km/2miles per hour speed while sustained climb for 300seconds. During which, Engine temperature must not reach within 10% of max engine operation temp as per engine manufacturer.
Secondly no liquid should spill over during this test, like coolant, fuel, brake fluids,fluid reservoir etc. Oil pressure,fuel pressure and other critical systems must operate within green zone. And many such things are included in test protocol.
During this and such other tests all auxiliary power drawing units like mission/ firing computers, climate control, auto loaders, battery charging etc are allowed to be switched off.
Also manufacture of vehicle needs to provide max sustainable speed at different ramp angles not just flat ground and max gradability.
Like 25kmph at 5*climb , 18kmph at10* climb etc.
Secondly Roll over angle ( angle at which the vehicle will topple front over) is also provided.
Another Major test is during descent, at what angle vehicle will slip downwards uncontrollably even after application of brakes. This angle is usually lesser than what a vehicle can climb in actual world and is taken quite seriously as it causes sure shot accident when it happens.
So, all in all, 60% claimed by Chinese may actually be 50-55* if they aren't yet following widely adopted standards, but even to claim 60% by any standard (doing just50) need to have pretty good torque low down the revs and very good gearbox. Here automatic gearboxes(Cvt) steal the show as they have ability to keep the engine working at max torque rpm irrespective of speed/ climb grade or gear.
They have proved themselves in every terrain but they are outdated now. Maybe something in the class of Piranha 8x8 or Stryker or Ratel series. The protection from small arms fire is there, mobility should be of lesser worry and can mount a decent cannon. But armored vehicles will not be the only candidates in the battlefield - expect others at some stage like gunships, lots of tube artillery, MLRS, ground strike aircraft which would require air superiority etc. Maybe transport helis for air borne Ops.
