Those 1.5T AL jacks are SCARY! I highly doubt they are really rated to 1.5T because they have a hard time lifting a damn honda civic. I once used one on a crown vic to change a tire on the front and had to force the handle down with my 200lb fat ***. I have a really cheap mack branded jack thats 2T and its better.
Also be aware that the bolts that hold the caster wheels on those racing jacks like to loosen up.
Well.... which one are you talking about? There's a difference between the regular and RapidPump jacks. They have different leverage-ratios with the hydraulics.
Basic physics in leverage and changing the fulcrum will get you different amounts of leverage. The standard-jacks have the leverage set to require about 10-15 pumps to lift a standard car. If you're pushing down with 200lbs X 15 pumps, you've generated 200x15=3000lbs of force. Multiply that by the stroke-length and you have work. Divide out by the time for each stroke and you have power.
Now, the RapidPump jacks have leverage-ratios set to lift my car in just 5 pumps. To generate the same amount of lifting force as the other pump, 3000lbs, the human needs to apply 3000/5=600lbs or 3x as much force as the other one using the regular jack.
Just because a jack has different leverage-ratios doesn't make it inferior in any way. The same exact jack with same frame and wheels would have the exact same load-capacity. For example, the #68783 & #69468 trolley-jacks have higher leverage and require more pumps at lower force to lift the same amount. But, you can see the frames twisting and bending under the load. And they're rated for 2-tonnes!!! I wouldn't trust those trolley-jacks at the same 1.5-tonne load as the aluminium racing jacks with RapidPump.
That's actually why I bought them, I go to the track about once a month and like to change out tyres and brake-pads; sometimes multiple times a day. Having the low 3" front-end of these jacks is really handy in getting under a racecar. And being able to lift the entire front or back end in just 3-5 pumps is a real time-saver.
If it's too difficult for you to use a RapidPump jack, replace the outer removable-handle with a longer piece. Instead of 18" or so, get a 4-foot pipe and use that. Or just stick the longer pipe into the outer handle. The resultant longer handle will give you more leverage and lower the force needed for each pump.