Bicycles Asked by askvictor on February 8, 2021
My son’s bike has a SRAM i3 internal gear + coaster brake hub. It has recently started sometimes only activating the coaster brake after backpedalling a good one or two full revolutions. When in this situation, it sounds somewhat clunky or grindy when the brake finally activates. However, sometimes, it kicks in straight away. I haven’t found a solid pattern to when it works and doesn’t, but it seems that the brake is more reliable in gear 1 than in gear 3, though I might be wrong about this. Can this adjusted/fixed, or do I need to replace the mechanism?
EDIT: After experimenting with the brakes and gearing with the bike in a stand (previously I had been trying while riding it) it seems that in gear 1, the brake always works fine. In gear 3, it requires almost a full rotation backwards before the gear engages. While in gear 2, it’s somewhere between – about half a rotation.
SRAM recalled 7,700 of these hubs due to brake failure in 2019.
Evidently the brake pawls were not lubricated properly.
According to the company, some of the affected hubs may have been manufactured with grease that gets sticky over time, especially if the bike sits unused for a while or is stored in a hot area. When the grease becomes sticky, the brake pawls in the hub can fail to engage.
Further
The recall applies to all bikes with this cruiser brake model that do not have independent front brakes.
The logic appears to be that if you have a front brake your hub does not need to be recalled.
According to the SRAM manual for this hub there are no user serviceable parts.
Only a qualified bike dealer should perform any necessary work on the gear hub, shifter, and brakes. SRAM i-Motion 3 User Manual
The manual says that "the brake jacket has to be lubricated with special grease. This work must be performed by a qualified bike dealer"
First I'd read the manual and make sure everything is adjusted correctly.
If that does not work then you can choose between:
The easy way to get rear brakes might be to add a hand brake to this bike if it will take one.
Answered by David D on February 8, 2021
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