One of the most valuable motorcycles in the world is going to auction in Italy next month: the Brough Superior SS100 nicknamed "Moby Dick" by Motor Cycling (UK) magazine in 1931. In that road test, the SS100 was proclaimed as "the fastest privately owned machine in the world" at that time. The bike was sold by Bonhams for £210,500 (US$333,210) in 2011, becoming one of the top 10 most valuable motorcycles ever sold. This time around, Moby Dick is estimated by auctioneers RM-Sothebys to sell for between EUR€500,000 and EUR€700,000 (US$550,000 to US$770,000) though it might very well sell for more.

During that motorcycle magazine test in 1931, Moby Dick was timed at 106 mph, with further tuning of the 1,142 cc v-twin engine later raising that figure to 115 mph in top (3rd) gear, with 109 mph achievable in second.

The main picture of this article shows Moby Dick as it is going to auction next month, with the image directly above this paragraph showing the bike as it went to auction six years ago. Detailed images of the bike in 2011 and today are available in the image gallery.

Four other Brough Superiors on offer

Moby Dick is one of five Brough Superiors headed for RM-Sothebys' Villa Erba sale on May 27, with all of them expected to fetch more than €100,000.

The remaining four Brough Superiors include a number of highlights with the most valuable being a 1936 Brough Superior SS100 (pictured above), one of just 102 SS100s built with a Matchless engine. The bike is presented in excellent mechanical condition and is expected to fetch between €180,000 and €250,000 ($200,000 to $275,000).

Another of the Brough Superiors on offer is this 1938 Brough Superior SS80 De Luxe (pictured above) expected to sell for between €100,000 and €150,000.

Provenance is one of the key variables in any price at auction, so it will be interesting to see how much the prior ownership of Brough Superior owner and CEO Mark Upham makes to the price of the 1933 Brough Superior SS80 De Luxe pictured above. The bike is estimated to sell for between €120,000 and €180,000.

The group is completed by the 2011 Brough Superior SS100 750 "Baby Pendine", which set a new record over both the both mile and kilometer at the 2013 Bonneville Speed Trials in the hands of motorcycle journalist Alan Cathcart. With just one private owner from new, it is being offered in its record-breaking specification and is expected to sell for between €100,000 and €150,000.

View gallery - 43 images