WHEELTOP Road TX OSPW Carbon Cage Review & Shimano Compatibility Test

I decided to take a close look at this "space-looking" WHEELTOP oversized pulley wheel system (OSPW) designed for the WHEELTOP Road TX wireless rear derailleur. Traditionally, old derailleurs used tiny 10-tooth jockey wheels, and modern ones use 11-tooth ones. The logic behind an OSPW is simple: a larger diameter reduces the articulation angle of the chain links, lowering friction and saving energy. While some brands use dual 17-tooth wheels, WHEELTOP uses an 11-tooth upper guide pulley and a gigantic 18-tooth lower tension pulley hidden behind an inbuilt fairing. This asymmetric design prevents excessive bending at the upper wheel while ensuring a gentler curve at the bottom for a smoother and quieter drivetrain. Plus, it features full ceramic sealed bearings (balls, inner, and outer races) lubed with a very light oil rather than heavy grease, making them spin incredibly well.

Taking the cage apart using Torx and 3mm Allen keys, the front and back plates are made of premium compound carbon fiber with about eight visible layers in the countersunk holes, decorated with a tough, light-reflecting multicolor decal. Weight-wise, the stock cage is 74g, and the OSPW is 105g, making the upgrade 31g heavier. Installing it on my WHEELTOP TX derailleur was easy: I removed the 3mm swing stop screw, let the spring unwind, backed out the 1.5mm holding pin, swapped the cages with a generous amount of grease on the pivot bolt, and reloaded the spring using the rear hole for lower tension. Because the tension pulley is 6 teeth larger, I mathematically added exactly 3 complete chain links (half a link per tooth) to my Connex chain before hitting the road.

I was also determined to see if this cage could fit the market’s most popular 11-speed Shimano Ultegra mechanical and Di2 derailleurs. Initially, the WHEELTOP pivot bolt fit the Shimano bodies, but the holding pin wouldn't go in all the way. Upon close inspection, the Shimano pivot bolt is squared off underneath, while WHEELTOP’s is rounded. It took me 3.5 hours of measuring, filing, grinding, and sanding to finally force it to fit both Shimano units, though the stopper screw placement was still slightly off.

So, what is my honest verdict after the road test? Is it faster? Honestly, I didn't notice any speed difference. It is ever so slightly smoother during gear changes and perhaps a fraction quieter, but that's about it. If you sum up the reduced chain articulation, the ceramic bearings, and the lower spring tension, the absolute maximum power you will save is just 1.63 watts. And if you factor in the aerodynamic penalty of a bulkier cage, you lose half a watt, bringing your net savings down to just over 1 watt. For the average rider, adding extra links can also be mechanically awkward and risk chain breakage if not done right. From a "bang for your buck" perspective, your money is much better spent on decent tires, TPU tubes, deep-section aero rims, or waxing your chain. However, the placebo effect is real; it looks brilliant, and during video playback, the lower wheel is so seamlessly covered that the chain looks like it's floating. If you are already running a WHEELTOP TX derailleur, have a spare $139 to $159 US, and want to treat yourself to some serious drivetrain bling, go ahead!