from BikeRadarwhat level pressure would you have in the tyres?
"Big tubular tires inflated to modest pressures are the norm as well, with typical sizes up to 27mm across and pressures as low as four or five bar (58-73psi)."
http://www.bikeradar.com/road/news/article/2012-paris-roubaix-equipment-check-photo-gallery-33654/