Brompton Sprinter Hub Repair

Sprinter shell

Way back in the early 90’s, prior to SunRace’s acquisition of Sturmey Archer, Brompton offered a five-speed model in its line-up. Brompton opted to utilise Sturmey Archer’s Sprinter hub for this. This week we have in a Brompton Sprinter hub for repair.

The Sprinter offered a wider range than the standard three-speed at 225% vs 177% for the three, along with narrower spacing; 1st being -33%. 2nd -21.5%, 3rd direct drive 1:1, 4th +26.6% and 5th being +50%. Sturmey also moved away from the awkward twin cable setup of the S5 and 5 StAr, using a much more intuitive single shifter to operate all five speeds and the indicator on the drive-side. The one we have in the shop is marked as September 1993 build date and is not running too well. The sprocket turns but binds after a quarter turn. It obvious that something internal has failed. Time to investigate.

Damaged sprinter hub

After a few minutes I have the internals removed from the shell along with the right-hand cone and the driver. Small chunks of metal fall onto the workbench along with a badly distorted driver pawl spring, no detective work required on this one. Further in I find this is actually the later ball-lock model, which uses ball bearings to engage the sun pinions rather than the earlier key-lock design. It could be possible the internals are not original to the 1993 shell as the ball-lock design came later on in the decade. It is apparent that someone else has been here before me as the clutch spring cap is fitted at the wrong end of the spring! Was this a repair attempt or the cause of the damage in the first place, who knows. With the internals fully disassembled and cleaned, it transpires that apart from a couple of damaged driver pawls, a spring and actuator plate, the parts are in remarkably good condition. There is no significant wear and both sun pinions have no damage from slipping (a common issue to the ball-lock model).

Damaged hub parts

With the new components fitted and all parts generously coated with genuine Sturmey Archer HMA106 grease (the only lubricant that should be use on these hubs, standard grease is far too thick), assembly starts. I pack the axle bearings and seals with red waterproof grease as this locks in the lubricate as well as providing a good barrier to water and grit getting in. Built back up and screwed back into the shell, bearings adjusted for minimal play, it’s bench tested to make sure all gears engage and no strange noises are present.

The complete wheel fitted back in the waiting Brompton and apart from an incorrect indicator rod, she’s running like a dream. It should see another 29 years of service with any luck.

Do you have a Brompton sprinter hub in need of repair? I’ve rescued many classic Brompton five-speed hubs over the years and so far it’s been a one hundred percent success rate. Get in contact if you own one and it too needs some TLC. Also check out my Brompton and Hub-Gear pages for more info.

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  1. Pingback: Brompton Sprinter Hub Service and Rim Replacement – PW Cycles

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