ACS Maindrive External Headset (Blue) (1-1/8")

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ACS Maindrive External Headset (Blue) (1-1/8")
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ACS MainDrive External Headset.


  • Forged steel cups
  • Alloy tops, and a cap with sealed bearings
  • Fits EC (traditional cup) applications

Size: 1" (25.4mm), 1-1/8" (28.6mm)
Weight: 157 g

This product was added to our catalog on March 12, 2019

Verified Owner
Monday, Mar 20 2023 (9 months ago)
ACS Maindrive External Headset (Blue) (1")
These headsets are garbage. I ordered three. The bottom cup and bearing and top cup and bearing seem switched. The crown race fits better in what should be the top, and the top fits better in what should be the bottom. The whole headset fits together poorly. Regardless, there was no top race in any of these kits. I had to salvage parts from my spares bin to make two of the headsets work. The third set was destroyed trying to install it and make it work with whatever parts I had on hand.

I own a bike shop specializing in BMX race bikes. I have real bike shop tools. I've been doing this for long enough. I say again this headset is trash. I've used ACS internal headsets and they work great. I've used other brand external headsets and never had an issue. For some reason the ACS external headsets are junk. There aren't a lot of options for 1" externals anymore, and now there is one less option for me.