New Slack-R IS42 Upper Cups Have Arrived!

New Slack-R IS42 Upper Cups Have Arrived!

IS42/IS52 Owners!! You asked for it so here they are! 


The new Slack-R IS42 and IS42S upper cups are now available!

What is a Slack-R and what does it do? Slack-R is our Head Tube Angle adjusting kit that allows you to slacken your HTA by up to 1.8°!  It is designed for bikes that have an IS style headset where the bearing seats are built into the frame instead of Press Fit bearing cups like you would find on ZS/EC headsets.


For More Information on how Slack R Effects Geometry Click Here

A little over a year ago we introduced the first Slack-R kits for IS41/IS52 headsets and made many Trek, Santa Cruz and Yeti owners very happy giving them the ability to get extra years out of their old frames or adjusting the geo on their brand new bikes to find the perfect fit. Some have even put the Slack-R on a new frame with a stock 63° HTA resulting in a HTA of less than 61°! Trying to chase the Grim Donut maybe...? The IS42 crowd was left waiting for a solution for their bikes and I am happy to announce the wait is officially over!  

IS42 is for all bikes that have a standard tapered IS42/IS52 headset which covers many popular bike brands

IS42S is a special upper cup that will fit Specialized brand bikes with an IS42/IS52 headset that have the upper IS42 bearing recessed deeper into the frame. The deeper recess also means you will need a total of 24mm of steer tube spacers on your bike currently to allow room for the Slack-R kit. 

*Not all Specialized have this deeper upper bearing and you will need to check which style you have on your frame*

Sure you have an IS headset but can't tell if its IS41 or IS42? Give your upper bearing a measure. 

IS41 Bearing OD = 41.0mm

IS42 Bearing OD = 41.8mm

Slack-R kits are made from 6061 Aluminum and weight between 112g and 146g depending on the kit. 

Always remember you need to have a minimum of 20mm of steer tube spacers for standard Slack-R kits and 24mm of steer tube spacers for IS42S Slack-R kits to make sure you have room to install. 

Find Your Slack-R Kits Here