Averaging 43.194 kph over a loop of 55 kilometres that included a 14km climb to the top of a mountain outside St Etienne, the German won an important time trial by more than three minutes.
"I wasn't sure what I could do in this particular stage," he said. "It was very tough but I was lucky because I avoided the rain.
"Gaining this time will make it a little more comfortable for me in the mountains. There I am sure to lose some time to the climbing specialists. There is still much to fear from my rivals. I just hope that I do not have a bad day.
"The coming days are going to be very hard and I don't want to talk about my chances before getting over the Alps."
Ullrich humbled his main rival, Richard Virenque, who had started the time trial three minutes before Ullrich. The Frenchman cut his left knee when his chain jumped, causing him to bang his knee on the handlebars.
Then after being overtaken by Ullrich, who had started three minutes later, he could only watch as the German rider became a diminishing yellow dot on the road ahead. Virenque fought back to close an embarrassingly large gap to a matter of metres at the finish.
Virenque, third overall last year, said : "I managed to limit the damage. Now comes my terrain and I'm going to fight to the finish."
An earlier embarrassment for Virenque, resplendent in his polka dot jersey of best climber, came as Ullrich pulled back two minutes on him in the climb to the summit of the Col de la Croix de Chaubouret.
Ullrich rates Ferrari and BMW as his favourite cars, but drives an Opel fast, resulting in two suspensions of his driving licence. His high-speed race through the countryside left Bjarne Riis, his Danish teammate and the 1996 Tour victor, third fastest, four seconds slower than Virenque.
Throughout the time trial no body topped Ullrich at four timed points. He was seven seconds faster than Abraham Olano and Virenque. Then Marco Pantani rose to challenge for some 30 kilometres, before falling back to finish 3:42 slower at the Cours Fauriel finish.
It was another agonising day for Chris Boardman. Unable to ride his specialised bike because it was too uncomfortable with his neck injury, he faded to 23rd, six minutes and 45 seconds behind Ullrich.
"It is hard on my morale especially when potential sponsors are coming to watch our team perform," Boardman said. "It is the first time that I have started a time trial knowing that I was not able to race flat out.
"I am worried about the stages that are coming. I cannot get out of the saddle to push harder on the pedals because it hurts, and if I stay in the saddle all the time I get cramp. I should manage the L'Alpe d'Huez stage tomorrow, but the day after there is a lot of climbing."
Boardman starts today more than an hour and a quarter behind Ullrich. Two weeks ago he led the German by two seconds as the battle for the yellow jersey opened in the prologue time trial in Rouen.
Britain's Olympic bronze medallist, Max Sciandri, is 74th, an hour and 10 minutes down overall, after finishing 8:31 off the pace yesterday.
Today L'Alpe d'Huez mountain, noted for its 21 hairpins, 14 kilometres and thousands of rabid fans, is sure to break the field apart. Tomorrow's leg into Morzine includes six mountains and even more pain for the 172 survivors as they begin the third and last week of the 3,950 kilometre route.
A week later the Tour has its grand finale in Paris. It can only be hoped that Boardman will still be taking part.
TOUR DE FRANCE 12th stage (St Etienne, 55 km time trial): 1 J Ullrich (Ger) Telekom 1hr 16min 24sec; 2 R Virenque (Fr) Festina +3:04; 3 B Riis (Den) Telekom +3:08; 4 A Olano (Sp) Banesto +3:14; 5 M Pantani (It) Mercatone Uno +3:42; 6 F Casagrade (It) Saeco +3:56; 7 F Vandenbroucke (Belg) Mapei +4:44; 8 Z Jaskula (Pol) Mapei +4:50; 9 B Zberg (Swit) Mercatone Uno +5:00; 10 M Boogerd (Neth) Rabobank +5:04; 11 J Jimenez (Sp) Banesto +5:19; 12 F Escartin (Sp) Kelme +5:23; 13 L Brochard (Fr) Festina +5:34; 14 J Pascual (Sp) Kelme +5:35; 15 P Jonker (Aus) Rabobank +5:52; 16 E Dekker (Neth) Rabobank +5:53; 17 O Camenzind (Swit) Mapei +6:15; 18 T Gouvenou (Fr) Big Mat +6:22; 19 L Dufaux (Swit) Festina +6:26; 20 J Odriozola (Sp) Batik +6:35 Others: 23 C Boardman (GB) GAN +6:45; 65 M Sciandri (GB) FDJ +8:31.
Overall standings: 1 Ullrich 61hr 22min 41sec; 2 Virenque +5:42; 3 Olano 8:00; 4 Riis +8:01; 5 Pantani +9:11; 6 F Escartin (Sp) Kelme +11:09; 7 Casagrande +11:16; 8 Dufaux +12:28; 9 Camenzind +13:15; 10 P Lino (Fra) BIG +14:16; 11 J M Jimenez, (Sp) Banesto +14:52; 12 P Luttenberger (Aus) Rabobank +15:47; 13 A Elli (It) Casino 17:16; 14 D Nardello (It) Mapei +17:33;
15 B Zberg (Swit) Mercatone Uno +17:47.
Others: 74 Sciandri +1:10.25; 85 Boardman +1:17.27
Points standings: 1 E Zabel (Ger) Telekom 272pts; 2 F Moncassin (Fr) GAN 191; 3 J Blijlevens (Neth) TVM 168.
King of the mountains 1 Virenque 259pts; 2 Brochard 185; 3 Ullrich 162.
Teams: 1 Telekom 184hr 37min 19sec; 2 Festina +00:14; 3 Mercatone Uno 07:15.Reuse content