Home > Other Fun Stuff > Advocacy & Industry News > News

More 9point8 Headsets Get Slack-R for ZS

9point8 Slack-R Zero Stack angle adjust headset ZS/EC
Support us! Bikerumor may earn a small commission from affiliate links in this article. Learn More

9point8 grow to their Slack-R angle adjust headset family with new press-in ZS and EC cups that can slacken your ride out between 1-2.8°. If you’re riding a bike that you wish wasn’t quite as steep to better tackle tougher trails, a 9point8 Slack-R Get Slack-R headset might just be the ticket to getting slacker…

9point8 Slack-R ZS & EC angle adjust headsets

A few years ago, Canadian component maker 9point8 launched the first angle-adjustable headset that worked on bikes with IS Integrated headset cups. That original thread-together affair worked by relocating your existing IS bearings above & below your headtube, into new eccentric offset cups that sat in the old bearing races. Now, riders of bikes that have Zero Stack headsets – where alloy cups are first pressed into your frame, with their own pressed-in bearings – can get the same slacker Slack-R conversion, as well.

What do you need to know?

9point8 Slack-R Zero Stack angle adjust headset ZS/EC standsrds

Modern tapered press-in headsets come in essentially 2 varieties – Zero Stack (ZS) where you don’t really see the cups and External Cup (EC) where you do. The 9point8 Slack-R headset solution again works by moving the bearings of your headset, outside of the headtube and offset a few millimeters from the centerline to effectively change your headtube angle.

9point8 Slack-R Zero Stack angle adjust headset ZS/EC, impact of headtube length
impact of headtube length on effective headtube angle change

Doing so results in between a 0.8-2.8° slacker head angle. (Or the same amount steeper if you want to go that direction.) It is dependent on headtube length, so shorter headtubes will see more dramatic changes.

Swapping in the external cups means a taller combined stack height of your headset. So, it’s important you have a spacer or two you can pull out from under your stem. Lest your steerer tube be too short. It will also most likely raise your headtube by up to 10mm, increasing frame Stack. And in addition to slackening your headtube, it will also increase fork Trail a bit.

Quite a bit of small geometry changes will take place. But that’s why you want to give it a try, right?

If you want more of a geo change explanation, 9point8 offers a deeper look at their Slack-R system, here.

Tech details

9point8 Slack-R Zero Stack angle adjust headset

9point8 calls the Slack-R design “creak-free”, made with machined 6061 aluminum cups and sealed stainless cartridge bearings. Headset kit weights range from 57-104g depending on your desired ZS/EC combo.

9point8 Slack-R Zero Stack angle adjust headset ZS/EC, machine shop bench

The 9point8 Slack-R now comes in press-in options to fit ZS headtubes. Upper bore diameter is available as 44mm, and lower bores of 49 or 56mm. With that, you can mix-and-match. Internal ZS44 or external EC44 up top. Then ZS 56, EC49, or EC56 down below, to get the angle change you want, within acceptable stack height increase.

ZS cups have minimal added height and less angle offset; while EC brings bigger changes.

9point8 Slack-R ZS & EC – Options, pricing & availability

9point8 Slack-R Zero Stack angle adjust headset ZS/EC, options

There’s a “Filter Your Slack-R Kit” tool on the left side of ZS/EC Kit page. It will show your options based on headtube length. Select 44mm upper and 49mm or 56mm lower, then it will show the resulting angle change and headset stack height of all possible options.

9point8 Slack-R Zero Stack angle adjust headset ZS/EC, contents

All Slack-R ZS/EC headset kits sell of $99USD including upper & lower cups with bearings, a crown race, star nut & top cap, and 9point8 installation and alignment tools. These new Slack-Rs, and the wide range of $109 IS integrated Slack-R headsets are available now. 9point8 includes free shipping in North America direct from 9point8.


Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments

Subscribe Now

Sign up to receive BikeRumor content direct to your inbox.

Subscribe Now

Sign up to receive BikeRumor content direct to your inbox.