Problem with disk rotor position on DT240 Front Hub and On-One Superlight Carbon fork

The bike is a Scandal 29" with superlight carbon fork. It's been running Hope Mono Mini front brake with a Hope Pro II hub and 183mm floating rotor for a while, no problems (though clearance between the rotor and dropout is tight, at about 0.8mm).

The new wheelset uses Swiss DT240s hubs, and on the front wheel two problems occur with the disk - firstly the rotor position lies outside the adjustment range of the brake caliper, and secondly the rotor carrier scrapes against the dropout (second problem can be fixed, just, by using a non-floating rotor since on floating rotors the carrier is a bit thicker than the actual rotor).

The issue appears to be because the rotor mounting surface is about 1mm closer to the clamping surface of the axle on the DT240 hub compared to the Hope Pro II hub. The effect is to move the rotor 1mm outboard, to the extent it scrapes the dropout and falls outside the range of the brake caliper.

The following pictures show the problem - click any of them for a larger version, and use the browsers 'back' button to return to this page.

Above: Front view of floating rotor on DT240 hub. The rotor carrier scrapes against the dropout.

Above: Back view of floating rotor on DT240 hub. The Mono Mini caliper is at the limit of its adjustment (as far outboard as possible). There are no shims/spacers present but the rotor is still too far outboard.

Above: By comparison here's the fork fitted with wheel built on Hope Pro II hub and identical 183mm floating rotor (except for the carrier colour). There is just enough space between the rotor carrier and the dropout for a 0.8mm thick steel ruler to be a snug fit, and although the brake caliper is at the limit of its adjustment it works ok.

Above: The problem appears to be that the DT240 has a shorter distance between the rotor flange and the axle clamping flats. The distance was measured by laying a steel ruler across the flats and measuring the drop to the rotor mounting surface (ruler not shown in pic).

Above: On the Hope Pro II hub, the distance appears to be 11.2mm (12mm as measured, less the 0.8mm thickness of the ruler laid across the axle flats).

Above: On the DT240 hub the distance appears to more like 10.2mm (11mm as measured, less the 0.8mm thickness of the ruler laid across the axle flats).

Also visible are the scrape marks on the rotor carrier where it fouls the dropout.

Above: View of the dropout sans wheel, showing the scrape marks and general positioning of brake caliper.

Above: Gratuitous pic of my On-One fleet :)