17” pit bike wheels are now commonly accepted as an alternative to the increasingly elusive Honda C90 wheels. I am demonstrating a simple method I have used here, for attaching to a standard 25mm kart rear axle to produce a fixed wheel solution.
Components:
2 off. Standard karting mono-alloy 3-stud rear hub. Typically £17.00 each online. Plus key steel.
2 off. 3mm steel ‘CycleKart adaptor plate’, newly available from Gemini Karts in their shop section. £2.80 each plus VAT
4 off. Flanged Oilite bushing OBF253516. Bearing Boys £3.88 each plus VAT
14 off. M8 x 25 Stainless steel socket button set screws. Toolstation Code 11982. £6.29 for a pack of 50.
2 off. Standard 25mm locking collar. Typically, £3.00 each online
2 off. External circlip. Less than £1.00 each online
Method:
1.The three 8mm studs require removal from the kart mono hubs. Mine unscrewed easily after carefully heating.
2.The standard 17” rim hub will require a couple of simple alterations. Remove the existing 35x15 bearings from both sides of the wheel by simply knocking out. The wheel hub has a raised flange to the disc carrier which is best removed flush and this can be achieved with an angle grinder, abrasive flap wheel or a hand file. See photo. The inside diameter of the wheel hub will most likely require a small amount of additional filing to remove casting flashing and allow the 25mm axle to pass clear through (this does not have to be accurate).
3. The Oilite flanged bushings are OD 35mm and ID 25mm and will press fit snuggly into both the inside and outside face of the wheel hub (in place of the original 35 x 15 bearings). These bushings are used as reducing spacers only and do not rotate on the axle.
4. The mono hub is fitted utilising the axle keyway. The 3mm steel adaptor plate is now bolted to the mono hub using three button head set screws, using thread-locker. Note, button head type screws are the best fit here but will still clash slightly with the wheel hub. This is remedied by cutting a small section off the outside of each screw head. See photo. This does have the advantage that they cannot back-out unseen.
5. Finish off by fixing four more set screws between the adaptor plate and the wheel hub, (photo shows a standard bolt in this instance) .Then a locking collar and a circlip.
NOTE. Each wheel has three separate attachments to the axle. The locking mono hub, the external locking collar and the external circlip. Individuals should ascertain for themselves the security of this suggestion, however I have yet to experience any issues.
See also my previous article on the tech forum utilising pitbike wheels with a front axle. ‘Turnkey dropped front axle’ 14.08.19