The 9point8 Slack-R kit allows you to change the head tube angle on bikes with IS headsets.
If you've ever wanted to try a slacker or steeper head tube angle on your bike but have been restricted by your IS headset then the new Slack-R is for you.
Using a patent pending modular system, you can now adjust the head angle by 1.2° to 1.8° depending on your frames geometry and which Slack-R kit is installed.
Please note the Slack-R is only compatible with frames using IS headsets and only those frames that run IS41/28.6 upper bearings and IS52/40 lower bearings.
Follow the three checks below to determine which Slack-R kits are available for your frame:
1. Confirm your headset is IS standard. If you're not sure check your frame manufacturers specification.
Park Tools also have a useful headset guide here: https://www.parktool.com/blog/repair-help/standardized-headset-identification-system
2. Confirm you have enough steerer tube length to accomodate the extra height of the Slack-R kit. If you have at least 20mm of steerer above your stem, below or combined in your current set-up then you will have enough room to install a Slack-R.
3. Measure or check your frame manufacturers specification to get your head tube length. This is often listed as HTL in manufacturers geometry charts. It's important to make sure this measurement is correct so if you are measuring yourself please ensure you use an accurate tool such as a digital caliper.
When installing any Slack-R kit please be aware that the effect on your bikes geometry will be more than just slackening the head tube angle.
Generally you should expect a small change in bottom bracket height, a slight increase in stack, a small decrease in reach and a noticeable increase in the wheelbase.