This weekend, following a rescheduling due to unfortunate unforeseen events, the 90th Pikes Peak International Hill Climb will take place in Colorado. And Audi is preparing a surprise.

The picture above was posted on the company's Facebook page, with a cryptic line attached: "To pay homage to our record-breaking past, we've got a surprise in store for you..."

What are they talking about? We checked the competitor list for this year's Pikes, and found five Audis: a 1983 Quattro run by rookie David Hackl, a pair of 2001 Audi A4s, a 1991 Quattro Coupe and a 2000 Audi S4. None of these, you will agree, are RS5s.

So what's the surprise? Naturally, Audi is being tight-lipped about the whole thing (what with it being a ‘surprise' and all), but we do know that sadly, Herr Rörhl won't be participating in the race. Will he instead be doing something with this Audi? After all, it is 25 years since he set a blistering time of 10m 47s in the Audi S1 to take the PP title. For many of those minutes, he was sideways.

Or could it be a special edition road car? Who knows. Post your best speculative guesses in the box below, using only the power that the Internet has vested in your information addled minds, and then watch a video reminding you of Audi's former glories on this most prestigious of mountains.

We'll be there this weekend, so check back for more on TopGear.com throughout the week. Don't forget, a certain British driver will be taking to the mountain in his dad's Ford RS200 too.

Tags: pikes peak, rs5, audi