Guide: OPI steerer replacements and stem options
My '15 Scalpel came with an OPI 120mm stem. I wanted to use a conventional non-Cannondale stem, so I just installed a replacement 1 1/8" steerer. Here's a summary of what I learned about the various stem options for anyone who wants to do this in the future.
Much thanks to Cannondale Experts and Project 321 for their help.
1.56" FIXED STEM (OPI GEN-2):
The headset on my Scalpel and any Lefty-equipped Si frame has bearings with a 1.56" internal diameter. The OPI system is a 1.56" steerer tube that threads from below into an OPI stem. The steerer tube comes in two sizes: regular and XL, the latter for XL frames.
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Available OPI stems are 90mm to 120mm from -15D to +6D. The system allows for 1.5cm of vertical adjustment with spacers. Weight is 300g for a regular-length steerer and a 120mm stem.
Cannondale no longer appears to use this OPI system. They recalled them in 2015 to avert fatigue failure. One mechanic told me this occurs when the steerer is under-torqued, loosens in use, and develops play that excessively stresses the threaded join. Cannondale's solution is a dealer-installed "wedge kit" that surrounds and compresses the steerer, ovalising it and preventing it from unwinding. This limits the number of times the steerer can be removed and rethreaded.
If the problem description above is accurate, an alternative solution might just be thread-locker. That Cannondale opted for additional hardware suggests there might be more to it.
Cannondale OPI Recall
It's very difficult to find 90mm OPI stems. They tend to be $100 or so when they do become available. I opted not to pursue this.
1.56" REMOVABLE STEM:
One replacement option is the KT040 "extra tall" steerer.
![]()
Cannondale Lefty Extra Tall Steerer Tube - KT040
This tube uses the existing Cannondale headset and 1.56" stems. The only 1.56" stems are in Cannondale's Headshok XC3 line.
Cannondale Headshok Mountain Stem Kit - 31.8
These are, again, difficult to find in stock, somewhat expensive, and heavy. Not all are designed for 31.8mm bars. The shortest available are 60mm and 80mm, with -20D to 20D possible for the latter. Height adjustment is possible with 1.56" spacers.
Weight is around 325g for a typical stem and cut steerer.
Cost is around $150 for a steerer and stem.
1.56" FIXED STEM (OPI GEN-1):
Same as above, but with one-piece stem and steerer. (There's no middle join like OPI Gen-2; this one tightens with a slim bolt on the bottom of the steerer. It's therefore considerably stronger.) These XC3 Integrated stems do not appear to be height-adjustable, nor do they come in lengths below 90mm.
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Cannondale XC3 Integrated Stem
Weight is around 250g.
Cost is $10 to $100 depending on desired stem length.
1.5" REMOVABLE STEM:
This is Cannondale's current approach. They use a frame-height-specific 1.56" steerer (KH197 variants for most frames, KH193 for the Oliver) that tapers to 1.5" at the top.
![]()
Cannondale Lefty Oliver Steerer for 134mm Head-Tube
Once again, you're mostly limited to Cannondale stems. Very few third parties make 1.5" stems. (Truvativ and Thomson are among the few.) There's also less height for spacers relative to the KT040.
Weight is around 325g.
Cost is around $130 for a steerer and stem.
1.125" REMOVABLE STEM:
There are three ways to do this:
a) Replace the 1.56" headset with a 1.5" to 1.125" K205 headset and install a KH106 1.5" to 1.125" steerer
b) Install a third-party threaded OPI 1.125" steerer adapter from Flatland Bicycles
c) Install a third-party 1.125" steerer tube using the existing 1.56" headset
The first approach is expensive, benefits from a bearing press, and makes it difficult to revert to the OPI stem for resale if desired. The second relies on the same threaded OPI Gen-2 mechanism that Cannondale recalled and costs around $150 for buyers in the USA. I opted for the third approach.
Steerers are available from Project 321 (alloy), MCFK (carbon), Experimental Prototype (carbon), and Flatland Bicycles (carbon) that should use the existing headset, though I only have experience with Project 321.
I bought this for $90:
PROJECT 321 | Products: 1.125" Cannondale Steerer Tube
The tube is about 250mm. Cutting it to 200mm leaves room for, in addition to the stem, about two inches of spacers on my Scalpel frame in size L. The weight of the steerer cut to this length is about 120g.
Installation involves removing the OPI stem with a Shimano bottom bracket tool as here:
To install the new steerer, first cut it to your desired length (or just do all this twice for a test-fit if you want to be extra-sure before you cut it).
Slide the top black ring off the steerer. Grease the sides, then use a rubber mallet to carefully slide it into the top Lefty mounting ring and the headtube. Seat with a rubber mallet. Then grease the bottom ring, insert the steerer up through the top ring, and seat the bottom ring with a rubber mallet.
At this point, you can retighten the Lefty bolts or install a stem and top-cap and then retighten the bolts. The sequence doesn't really matter with this design, there's plenty of friction holding everything in place once you've seated both rings.
With a Kalloy Uno stem and alloy top cap, the entire combination with star-nut and top cap is under 250g. I detected no play or flex at all in my test rides.
COMPATIBLE STEM LENGTH:
With a Lefty 2.0 (Scalpel 2017+, FSi 2015+), you can use almost any stem because the top of that Lefty is nearly level with the higher mounting ring. Not so much the Lefty 1.0; some stem combinations will cause the handlebar to hit the Lefty body or the lockout.
I've mocked up various stems, a 31.8mm bar, and a Lefty 1.0 with a hydraulic lockout:
![]()
From top left to bottom right:
[stem length] [angle] [spacers]
60mm +6D 25mm
70mm +6D 15mm
80mm -6D 25mm
120mm -17D 15mm (stock)
With no spacers:
For a stem angle from 0D to -20D, 90mm is possible.
For a stem angle over 10D, 80mm is possible.
None of this is really bar-dependent. Riser bars will interfere with the Lefty before the rise begins. Backsweep will have a slightly more of an effect if you're really on the margins.
If you want to try this in Photoshop yourself, the squares in the graph scale above correspond to 1cm and the Lefty dimensions and position were pulled from my Scalpel.
Hope this helps someone! Let me know if you catch anything incorrect.
My '15 Scalpel came with an OPI 120mm stem. I wanted to use a conventional non-Cannondale stem, so I just installed a replacement 1 1/8" steerer. Here's a summary of what I learned about the various stem options for anyone who wants to do this in the future.
Much thanks to Cannondale Experts and Project 321 for their help.
1.56" FIXED STEM (OPI GEN-2):
The headset on my Scalpel and any Lefty-equipped Si frame has bearings with a 1.56" internal diameter. The OPI system is a 1.56" steerer tube that threads from below into an OPI stem. The steerer tube comes in two sizes: regular and XL, the latter for XL frames.
Available OPI stems are 90mm to 120mm from -15D to +6D. The system allows for 1.5cm of vertical adjustment with spacers. Weight is 300g for a regular-length steerer and a 120mm stem.
Cannondale no longer appears to use this OPI system. They recalled them in 2015 to avert fatigue failure. One mechanic told me this occurs when the steerer is under-torqued, loosens in use, and develops play that excessively stresses the threaded join. Cannondale's solution is a dealer-installed "wedge kit" that surrounds and compresses the steerer, ovalising it and preventing it from unwinding. This limits the number of times the steerer can be removed and rethreaded.
If the problem description above is accurate, an alternative solution might just be thread-locker. That Cannondale opted for additional hardware suggests there might be more to it.
Cannondale OPI Recall
It's very difficult to find 90mm OPI stems. They tend to be $100 or so when they do become available. I opted not to pursue this.
1.56" REMOVABLE STEM:
One replacement option is the KT040 "extra tall" steerer.
Cannondale Lefty Extra Tall Steerer Tube - KT040
This tube uses the existing Cannondale headset and 1.56" stems. The only 1.56" stems are in Cannondale's Headshok XC3 line.
Cannondale Headshok Mountain Stem Kit - 31.8
These are, again, difficult to find in stock, somewhat expensive, and heavy. Not all are designed for 31.8mm bars. The shortest available are 60mm and 80mm, with -20D to 20D possible for the latter. Height adjustment is possible with 1.56" spacers.
Weight is around 325g for a typical stem and cut steerer.
Cost is around $150 for a steerer and stem.
1.56" FIXED STEM (OPI GEN-1):
Same as above, but with one-piece stem and steerer. (There's no middle join like OPI Gen-2; this one tightens with a slim bolt on the bottom of the steerer. It's therefore considerably stronger.) These XC3 Integrated stems do not appear to be height-adjustable, nor do they come in lengths below 90mm.
Cannondale XC3 Integrated Stem
Weight is around 250g.
Cost is $10 to $100 depending on desired stem length.
1.5" REMOVABLE STEM:
This is Cannondale's current approach. They use a frame-height-specific 1.56" steerer (KH197 variants for most frames, KH193 for the Oliver) that tapers to 1.5" at the top.
Cannondale Lefty Oliver Steerer for 134mm Head-Tube
Once again, you're mostly limited to Cannondale stems. Very few third parties make 1.5" stems. (Truvativ and Thomson are among the few.) There's also less height for spacers relative to the KT040.
Weight is around 325g.
Cost is around $130 for a steerer and stem.
1.125" REMOVABLE STEM:
There are three ways to do this:
a) Replace the 1.56" headset with a 1.5" to 1.125" K205 headset and install a KH106 1.5" to 1.125" steerer
b) Install a third-party threaded OPI 1.125" steerer adapter from Flatland Bicycles
c) Install a third-party 1.125" steerer tube using the existing 1.56" headset
The first approach is expensive, benefits from a bearing press, and makes it difficult to revert to the OPI stem for resale if desired. The second relies on the same threaded OPI Gen-2 mechanism that Cannondale recalled and costs around $150 for buyers in the USA. I opted for the third approach.
Steerers are available from Project 321 (alloy), MCFK (carbon), Experimental Prototype (carbon), and Flatland Bicycles (carbon) that should use the existing headset, though I only have experience with Project 321.
I bought this for $90:
PROJECT 321 | Products: 1.125" Cannondale Steerer Tube
The tube is about 250mm. Cutting it to 200mm leaves room for, in addition to the stem, about two inches of spacers on my Scalpel frame in size L. The weight of the steerer cut to this length is about 120g.
Installation involves removing the OPI stem with a Shimano bottom bracket tool as here:
To install the new steerer, first cut it to your desired length (or just do all this twice for a test-fit if you want to be extra-sure before you cut it).
Slide the top black ring off the steerer. Grease the sides, then use a rubber mallet to carefully slide it into the top Lefty mounting ring and the headtube. Seat with a rubber mallet. Then grease the bottom ring, insert the steerer up through the top ring, and seat the bottom ring with a rubber mallet.
At this point, you can retighten the Lefty bolts or install a stem and top-cap and then retighten the bolts. The sequence doesn't really matter with this design, there's plenty of friction holding everything in place once you've seated both rings.
With a Kalloy Uno stem and alloy top cap, the entire combination with star-nut and top cap is under 250g. I detected no play or flex at all in my test rides.
COMPATIBLE STEM LENGTH:
With a Lefty 2.0 (Scalpel 2017+, FSi 2015+), you can use almost any stem because the top of that Lefty is nearly level with the higher mounting ring. Not so much the Lefty 1.0; some stem combinations will cause the handlebar to hit the Lefty body or the lockout.
I've mocked up various stems, a 31.8mm bar, and a Lefty 1.0 with a hydraulic lockout:
From top left to bottom right:
[stem length] [angle] [spacers]
60mm +6D 25mm
70mm +6D 15mm
80mm -6D 25mm
120mm -17D 15mm (stock)
With no spacers:
For a stem angle from 0D to -20D, 90mm is possible.
For a stem angle over 10D, 80mm is possible.
None of this is really bar-dependent. Riser bars will interfere with the Lefty before the rise begins. Backsweep will have a slightly more of an effect if you're really on the margins.
If you want to try this in Photoshop yourself, the squares in the graph scale above correspond to 1cm and the Lefty dimensions and position were pulled from my Scalpel.
Hope this helps someone! Let me know if you catch anything incorrect.
