CALGARY -- For the past 40 years, 36 wagons have competed in the Rangeland Derby, the Calgary Stampede's iconic chuckwagon races.

But starting in 2021, that number will be reduced to 27, meaning three wagons competing in nine heats instead of the four they've had in the past.

That was just one of the changes the Stampede announced this week, in a letter it sent out to drivers from both World Professional Chuckwagon Association (WPCA) and Canadian Professional Chuckwagon Association (CPCA).

That latter group discovered that starting in 2022, only WPCA members will receive an invitation, making it tougher for Canadian riders to get even compete in the lucrative event.

The Stampede will also install light-weight, collapsible arms along the inside rail of the track, in order to create a buffer zone between racing wagons and the rail.

There will also be behind-the-scenes changes, including intensified pre-race inspections of horses.

The Stampede also announced there would no longer be a tarp auction, a Stampede tradition for 40 years.

"The auction....will always be recognized as a special part of our history," the letter said, "but our goal is to have you (riders) take control and achieve the greatest possible benefit from the advertiser relationship."