Flyhalf Peter Grant scored a try among 20 points to guide South Africa's Stormers to a 35-26 win over the Chiefs in a Super 14 round five match in Hamilton.

The Stormers scored three tries in a dominant first half then banked their second bonus point on the road with a disputed penalty try in the 55th minute which allowed them to hold out a strong Waikato comeback.

Australian referee Matt Goddard awarded the penalty try, which pushed the tiring Stormers from a 28-23 to a 35-23 lead, for what he judged to be a tackle from an offside position by a Waikato player.

The penalty seemed to be an extreme sanction for what was shown to be a merely technical infringement and played a part in allowing the Stormers to establish and hold on to their winning margin.

"I didn't see it but obviously the ref thought it was a penalty try," Waikato captain Mils Muliaina said. "We were right in the game then. It was a big decision and we couldn't come back from that."

The Stormers benefited from a number of contentious decisions in the second half. Television replays showed the Stormers' Fijian winger Sireli Naqelevuki had stepped into touch in the leadup to the penalty try.

Waikato had two tries disallowed in the second half. All Blacks scrumhalf Brendon Leonard crossed the Stormers' line late in the spell but was called back by the linesman who ruled flyhalf Stephen Donald had stepped into touch in the lead-up. Replays cast doubt on that decision.

Winger Lelia Masaga, who scored one of the Waikato side's two tries, was denied another for what was deemed to be a forward pass.

The Stormers built a 25-13 halftime lead from an outstanding first 40 minutes.

Grant, winger Tonderai Chavhanga and fullback Conrad Jantjes scored tries as the Stormers came close to gaining a bonus point by halftime.

Waikato was kept in the match by Donald, who came into it with a 48 per cent goalkicking record but landed six goals from seven attempts - two conversions and four penalties for 16 points.

The home side closed to 25-23 after seven minutes of the second half but a penalty to Grant and the penalty try made the game safe for the Stormers.

After starting the season with three losses, the Stormers beat Queensland in Brisbane last week to move off the bottom of the standings.

"It's good to get back-to-back victories. That's never easy away from home," captain Jean de Villiers said.

"It's great scoring four tries. To get 10 points from two games on tour is great and it puts us in a good position for a tough match against the Blues."

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