Brett Lee has backed South Africa's controversial speed guns by declaring he is bowling faster than at any time during his eventful career as the Test series winds down.

Lee was again clocked in excess of 156km/hour yesterday in the most energetic moment of a flat third Test at Kingsmead here, taking 4-82 with the help of brilliant catches from Matthew Hayden and Damien Martyn.

It was a positive note in a mixed season for Lee, who was recorded at a personal best 157.4km/h during the second Test in Cape Town last week amid doubts about the accuracy of the speed guns.

On those readings, Lee has bowled faster in the last two Tests than he has bowled in his 21-match career, or during his 34 one-day internationals, but the Wollongong quick believes the measuring devices.

"I'm probably bowling quicker now than I ever have - consistently quicker over a long spell and I couldn't do that six months ago," Lee said.

"It's a rhythm thing. A fast bowler always bowls his quickest when he's not trying to bowl quick and that's something Dennis Lillee has taught me.

"I wasn't trying to go out there and bowl full pace. I was hitting the deck and charging in, but I was trying to work on my action as well, standing nice and tall."

Lee ran in for Australia on a day when it appeared the strain of a long summer and back-to-back Tests were wearing on the world's top two teams.

On a relatively comfortable Kingsmead wicket, 17 wickets fell for 278 runs on the second day, finishing with Australia 8-159 in its second innings, leading by 307 runs.

Lee and South African all-rounder Jacques Kallis, who landed a blow on Mark Waugh's Test career by bowling the veteran for 30, admitted the Durban heat and the recent workload may have influenced some careless batting.

But neither player doubted the motivation of the teams and Lee was Australia's best example as he charged in on a humid day hitting 30 degrees.

The 25-year-old's speed might be going up but so is his bowling average and his economy rate after a difficult period marred by injuries.

After taking 31 wickets in his first five Tests at an average of just 16.06, Lee has taken 53 wickets from his next 16 matches at the moderate average of 31.69.

He has to compete with Glenn McGrath, Shane Warne and Jason Gillespie for wickets in cricket's most potent pace attack but that does not excuse his economy rate, which has ballooned to 3.6 runs per over in the last two years.

"On the last couple of grounds we've played it's been a pretty fast outfield, so I wasn't too worried about going for too many runs," Lee said.

"We have got pretty attacking fields too. Steve Waugh likes to attack as much as possible and he came up to me today and said: 'don't worry about the runs, just try to get a few breakthroughs', and that's what we were aiming at."

Lee also contributes to Australia's slow over rates because of his long run and follow-through, but he has not been the only offender in this Test.

The over rates have become laughable, even with spinners bowling and allowing for drinks breaks in the heat, with both days ending in bad light almost one hour after the scheduled close time.

There were 89 overs bowled on the first day and 87 yesterday leaving genuine reason to consider the future of scheduled two-hour sessions.

On yesterday's rate, both teams completed less than 12.5 overs per hour, with spinners bowling 26 overs.

© 2002 AAP