He got involved in bull riding after being encouraged to take up the sport by a friend in Dunedin who breeds bulls used in rodeo.
Sandri said his first couple of rides were "a blur".
"It's hard to explain unless you've hopped on one. It's just a complete rush and I guess there's lots of little things to think about too. It's just a cool feeling."
He believed his mountain-biking experience, particularly the balance and mental preparation aspects, had helped him in bull riding.
He planned to stick with bull riding for now and had no immediate plans to jump back on a mountain bike.
"I've been taking a bit of a break from it ... I'm not sure if I'll go back, to be honest. I don't have any real plans to at the moment."
Rakaia's Adam Williams won the open bareback category and Ross Dowling, of Havelock North, claimed the open saddle bronc.