The Altech Autopage Karan Beef pair hung on in a tight run into the finish at MacKenzie Club near Ixopo to claim the win over 79km in 2:58:09.
Multiple national time-trial champion David George and teammate Justin Tuck of The Gear Change were second on the day in 2:58:13, while race leaders Johann Rabie and Gawie Combrinck of EAI Cycling came in for third a further second back.
Rabie and Combrinck now take a commanding 19-minute lead (27:45:48) into the penultimate stage of the 900km race.
Kachelhoffer and Seyffert move into second overall (28:05:02) in the absence of overnight runners-up Tyronne White and Andrew Hill. The Avis Van Rental duo was forced out of the race after White sustained a knee injury in a crash on Wednesday.
Third place in the general classification now belongs to George and Tuck (28:10:51).
“This stage is always so fast and I think everyone looks forward to seeing how fast they can go on the flowing singletracks, so we knew it would come down to a bunch sprint,” said Kachelhoffer.
“Luckily, today Pieter and I had good legs into the finish.”
In the other racing categories, some leads changed hands while others extended their already substantial time gaps.
There was an upset in the mixed category as Seattle Coffee’s Billy Stelling and Carmen Buchacher stormed through the singletrack trails ahead of overnight leaders, an under-the-weather Samantha Sanders and teammate Justin Victor of Valencia Cycling.
Stelling and Buchacher finished first on the stage in 3:09:49 to slip into the overall lead in 31:21:43 – a full five-and-a-half minutes ahead of Sanders and Victor.
“I rode with the second group through the Oak Lane dual track and my plan had been to wait for Carmen and give her a hand up the hill on the Red Bull Run,” said Stelling.
“But then she came out in front and just rode brilliantly. We were just aiming to consolidate second but she rode so well today that the race is on again.”
Former downhill racer Victor said he and Sanders were particularly strong on the technical sections and would be looking to take the lead back on the Umkomaas descent on Friday.
Women’s race leaders Catherine Williamson and Yolande de Villiers continued their total domination of their category, with a seventh straight win for SasolRacing in 3:17:16 (30:56:18).
The City Lodge vets and masters categories remain unchanged with HiddenHunger’s David de Lima and Sean Henderson topping the former in 3:16:25 (31:11:26) and USN-Cycle Lab’s Chris Brand and Paul Furbank claiming the latter in 3:15:16 (30:09:23).
In the dice for the solo category, Timothy Hammond and Nico Pfitzenmaier were awarded the same time of 2:58:36 on the stage to keep Hammond in the overall lead (28:29:41).
Solo woman Paula Hardy kept top spot in the standings (34:24:39) with the stage win in 3:49:48.
Day eight of the nine-day race sees riders descend over 2 163m into the Umkomaas River Valley as they take on the 99km route to Jolivet Farm in the vicinity of Highflats in KwaZulu-Natal.
The race culminates on the South Coast at Scottburgh main beach on Saturday.
Men: 1. Pieter Seyffert & Hanco Kachelhoffer (Altech Autopage Karan Beef) 2:58:09; 2. David George & Justin Tuck (The Gear Change) 2:58:13; 3. Johann Rabie & Gawie Combrinck (EAI Cycling) 2:58:14
Women: 1. Catherine Williamson & Yolande de Villiers (SasolRacing) 3:17:16; 2. Sarah van Heerden & Cindy Theunissen (Old Mutual) 3:48:56; 3. Carla Plens & Graziela Takay (Brazil Legionarias) 4:16:16
Mixed: 1. Carmen Buchacher & Billy Stelling (Seattle Coffee) 3:09:49; 2. Samantha Sanders & Justin Victor (Valencia Mixed) 3:20:34; 3. Hayley Smith & Darryn Purtell (Bell Equipment) 3:34:48
Men: 1. Johann Rabie & Gawie Combrinck (EAI Cycling) 27:45:48; 2. Pieter Seyffert & Hanco Kachelhoffer (Altech Autopage Karan Beef) 28:05:02; 3. David George & Justin Tuck (The Gear Change) 28:10:51
Women: 1. Catherine Williamson & Yolande de Villiers (SasolRacing) 30:56:18; 2. Sarah van Heerden & Cindy Theunissen (Old Mutual) 34:31:22; 3. Ann Olivier & Shirley-Ann van Heerden (Mazi Capital) 38:23:17
Mixed: 1. Carmen Buchacher & Billy Stelling (Seattle Coffee) 31:21:43; 2. Samantha Sanders & Justin Victor (Valencia Mixed) 31:27:14; 3. Hayley Smith & Darryn Purtell (Bell Equipment) 33:00:19