QBP’s house brand Problem Solvers started out offering those boring little nick-knacks necessary to put your bike together, like headset spacers and cable hangers, but lately they’ve been pulling a few cool tricks out of the hat. I saw this item and I got all tingly. The E46 bottom bracket is an eccentric bottom bracket to install 24mm spindle cranks and GXP-type cranks to PressFit BB30 (PF30) frames. So what? So that means that you can get 16mm of chain tensioning eccentricity on your very latest PF30 road and mtn bikes, thereby facilitating some elegantly clean single-speed conversions, without the need for a chain-tensioner.
I guess it’s necessary to explain PF30 here: Like the BB30 standard, PressFit BB30 use a bearing about 44mm OD and 30mm ID to fit specific BB30 cranks. The difference is that BB30 has the bearings pressed directly into the frame and held in with C-clips, while the PressFit BB30 has the bearings fitted into plastic cups which are in turn pressed into a larger, 46mm ID shell. What this means is that the tolerances needn’t be as tight (plastic cup is forgiving of minor inconsistencies) and less material is needed (no groove for a C-clip). For use in carbon frames, PressFit BB30 makes the most sense (less weight), and even for materials such as titanium I can see the benefits (less machining). Remember, PressFit BB30 uses the same cranks as BB30.
Back to the single-speed hacks: 16mm of eccentricity should be enough to tension a chain (since each chain link is 12.7mm long). So rather than using a BB30 crank on your PressFit BB30 frame, you install Problem Solvers E46 bottom bracket plus the 24mm spindle crank of your choice. Granted, the 24mm cranks tend to weigh more than the BB30 cranks, but given that some of the PF30 frames are amongst the lightest available, you still have a lot of potential for the bike as a whole. As cool as it sounds to me to build up a sub-13 pound SS or fixed gear road bike, I think that the E46 will be most attractive to mtn bikers as the eccentric BB is ideal for using with disc brakes because the rear axle will always be perfectly aligned with the disc caliper. Same goes for cyclocross bikes, though it usually isn’t a big problem for cantilever brakes. But with single-speed cross being such a hot category for racing, this could be the ticket if you’ve got the PF30 frame.
The E46 can be fitted to both 68mm and 73mm PF30 frames and will fit cranks with 24mm spindles such as those that fit external cup BBs, and it will come with the additional pieces necessary to fit GXP-type cranksets. I think this item has a lot of potential, but I’ll reserve final judgement until I see how well the E46 holds chain tension while in use (the downfall of many a cheap eccentric BB on single-speeds).
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