Slack-R IS42S Upper Cup 42-46mm
0000-1374Regular price $40.00 USD
The 9point8™ Slack-R™ kit changes the head tube angle on bikes with IS headsets. (IS41 and IS42* upper bearing and IS52 lower bearing only.)
Have you found a Kit that fits your bike? There are convenient kits that group the parts you need HERE. But if you want to buy individual Slack-R parts, you are in the right place! You need three individual parts to adapt your bike (Upper Cup, Tensioner, and Lower Cup); use our KIT SELECTOR on the kit page to get the right combo.
Confirm the three checks below and complete the drop down menus to see what Slack-R kits are available for you.
1. Confirm your headset is the IS Standard
If you are not sure, read this article on headset identification by the experts at Park Tools.
| 2. Confirm you have enough steer tube length to install a Slack-R
If measurements A + B are greater than below there is enough steer tube to install a Slack-R
3. Measure or look-up your bike's head tube length (HTL)
Bicycle manufacturers often list your bike's HTL in geometry charts on their websites. You can also measure this yourself as shown below.
What does installing a Slack-R do to your bikes geometry?
Click HERE to take a deeper look.
Want more customization?
Add additional parts to your Slack-R Kit to fine tune your HTA and test the extremes. Individual parts located HERE.
Slack-R is now compatible with MOST Tapered IS headsets. There are 3 different styles of upper cups now to go along with the IS52 lowers. IS41, IS42, and IS42S.
IS41/IS52 will fit a number of bikes from manufacturers such as Yeti, Santa Cruz, and Trek (eliminates the need for a Knock Block in most cases). Cube is an exception as they use a deeper upper bearing seat and the Slack-R IS41 will not sit properly in the Cube frames.
IS42/IS52 will fit many bikes from Cannondale, Norco, Marin, Orbea, GT, Revel, Scott and many more including some Specialized with a standard depth IS42/IS52 headset. Standard bearing seat depth is 3mm
IS42S/IS52 will fit Specialized bikes that have the 6.8mm deep upper bearing seat. (some Specialized bearings sit deeper than the standard IS42 geometry so they require their own specific top cup to insure proper fitment)
Headset types do vary across the same manufacturer, make sure you are sure what kind of headset you have. (IS/EC/ZS or hybrids of these)
Some IS bearing seats in the frames have a smaller bearing seat inside diameter than others so in some cases a bit of sanding will be required to fit in the 34.5mm upper sleeve and 44.5mm lower sleeve. In most cases the frame allow the kits to drop right in but in some cases opening up the upper and/or lower bearing seat inside diameter(s) will be required so double check your frame clearance prior to ordering if unsure.
Contact firstname.lastname@example.org if you are unsure about your application prior to ordering.
Does your bike have a Trek Knock Block headset?
The Stop Chip must be removed from all Trek Knock Block headsets before installing a Slack-R. Read more here.
|Upper Cup||Min L||Max L||Lower Cup||Min L||Max L||Tensioner||L||Kit Weight (g)||Kit|
Click on the image, or click here to download the Slack-R Instructions PDF