How much weight (in pounds) can the bigger breeds of horses or the riding ones pull?

Answers:
that depends on what you mean. the clydesdale i know can pull about 700 pound blocks behind her easy enough. but on wheels its completely different. she can pull an 11000 pound tractor without much strain. once she gets it going she can trot in nice active paces pulling that much. and she isnt as big as they get. she's 16.9 hands. which breed in specific were you asking about?
i've seen a team of two shire horses pull 15000 pounds at a light canter without breaking a sweat. they were both big stallions though. shire horses get almost as big as clydesdales and percheron are next in line when it comes to avaerage size. though the biggest horse alive is percheron who reaches 19 hands that isnt average its quite rare. clydesdale stallions avaerage at max of 18 hands.
a sigle draft horse can pull at least one and a half times it's own weight. maybe not at an active canter but they should be able to get to a good trot with that much. even the lesser ones can pull that much.
a team of two draft horses can easily pull three times their own weight on wheels.

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A horse can easily pull a wheeled vehicle that is six times his own weight, however most carriage or draft horses are used at only 25% of that capacity. A carriage or draft horse averages in weight from 1200lbs to 2300lbs, therefore they are able to pull anywhere from 7200lbs to 13,800lbs.