Ask a Mechanic | How to Dial-in Shifting & The Rise and Fall of ISIS Cranks

Welcome to our Ask a Mechanic column where our expert mechanic Daniel Slusser answers your bike maintenance questions. If you have a question for Daniel, please post it on our Facebook Wall or e-mail Daniel directly at In today’s entry Daniel discusses how to dial in shifting with proper cable installation and provides a brief history of ISIS bottom brackets.

I have a 2012 S-Works Tarmac. The components are 1.5 year old Dura-Ace 7900 that were transferred from another bike to the Tarmac two months ago. Ever since I got the Tarmac frameset, rear derailleur shifting has been poor. Just two weeks ago I brought the bike to another shop and changed from standard cables and housings to Gore Professional. Shifting improved quite a bit, but was not quite right. Today was particularly bad.

Here is what I experienced today:

While in the 4th cog I could hear the sound that indicates that a rear derailleur adjustment is needed. I could eliminate the problem by pushing the dual control lever inward. I jumped off the bike and turned the adjuster 1/4 turn. I jumped on the bike and the sound persisted. I repeated this until the noise was gone. Shifting to smaller cogs were reasonably fast while in the small chain ring. With no further adjustment, after shifting to the large chainring, shifts to smaller cogs did not happen at all. I continued to ride a bit more and shifted to the small chainring. Now the derailleur adjustment was too tight (i.e. the rear derailleur was on the verge of shifting to a larger cog). Do you have any ideas on how to solve this? From: Dave


It is time to shift your attention away from cable tension because it sounds like you have a pretty good working understanding of how to adjust your shifting, as you are doing the right things to trouble shoot a typical cable tension issue. I suspect the problem can be traced back to excessive drag somewhere along the length of the cable.

The first thing I would check would be that the cable housing runs are the right length. Check to see if the loop to the rear derailleur is too short and the housing is kinked or if the housing between the shifters and frame are too short. Also check to make sure the housing is seated properly in the shifter. If the housing was too short it may have pulled out in the shifter when the bars were taped or when the handlebar was turned. You should apply grease to the white teflon ramp that the cable runs along on the hood of the shifter if it has not been lubed already.

The next thing to check is that the housing was cut squarely and that the inner sheath on the housing is flared at the ends and not dragging on the cable. This check can be performed by shifting the rear derailleur into the largest cog and then releasing the cable without turning the pedals in order to develop slack in the cable. Pull the housing out of the stops in the frame, shifter, and derailleur then remove each housing ferrule and slide it up the cable to inspect the housing ends.

Each of these items are quick and easy checks, which is why I advocate doing them first, but the problem likely lies elsewhere. Your S-Works Tarmac’s internal cable routing invites tangling of the two wires inside the frame. If the other inspection items fail to produce a culprit then you will likely need to remove and replace the rear shifter inner wire. Once the wire has been clamped and cut, do not reuse it after removal. This is because the wire will likely unravel when it is pushed through the housing and drag even worse.

I explained how to replace cables on an internally routed Tarmac without getting them tangled in an earlier post that can be viewed here. Best of luck David. Remember that your LBS should cover this derailleur work under warranty. If they don’t, it is time to find a new shop and mechanic that places a higher value on your business.


Say, I came across your site while searching the web for Isis BB manufacturers. There isn’t a site that lists Isis manufacturers. So how does one review and compare Isis BB’s when there doesn’t seem to be a place that lists them. I mean, even bicycle part etailers don’t provide bb filters to look only at Isis drive units; you can filter by brand or price but not type. What’s with all the non-info on Isis? Is it because they are on the fringe? Thanks for helping to answer this. As you may have guessed, I need an Isis BB and am finding it impossible to know who manufacturs them and how to compare them. From: Tim

This photo from shows the difference between JIS, Octalink and ISIS bottom brackets.


Finding ISIS bottom brackets is difficult because it’s a standard that was abandoned in about 2004. The story behind this standard is fascinating to me because it highlights the best and worst aspects of the bike industry with it’s remarkable ability to both cooperate and exclude, and serves as a cautionary tale on the dangers of groupthink and design by committee.

An example of an ISIS bottom bracket made by one of the original collaborators on the standard: Race Face

At the end of the nineties, when modern big-mountain freeriding was born and downhill racing was beginning to resemble the sport that it is today, it became clear to nearly everyone that the JIS square taper bottom bracket was not up to the abuse that this new style of riding placed upon it. Aggressive riders routinely snapped JIS spindles or wallowed out their crank arm spindle bores. A lighter stronger pipe billet interface was needed. While this idea was certainly not new, this is when a general consensus for the need for such a standard began.

Shimano stepped up and designed their Octalink standard for their m951 XTR crankset. It worked magnificently and nearly every rider on the UCI World Cup Downhill and NORBA racing circuits adopted them immediately, rendering broken spindles an extremely rare occurrence. The problem was that Shimano patented the interface and required other manufacturers to pay a licensing fee in order to use it. This was a new development as the older JIS standard was open and all cranks and bottom brackets were universally interchangeable. Until XTR m951, the concept of proprietary cranks and bottom brackets was foreign outside of a few oddball offerings from Bullseye, Grove, and others.

With the industry unwilling to pay this licensing fee, a coalition between crank and bottom bracket manufacturers was developed that included, Race Face, Chris King, FSA, and a new upstart from Art’s hometown of San Luis Obispo, California named Truvativ. They developed what was termed an open, free to use “international standard” called ISIS (Internation Spline Interface Standard that whimsically shared the name of the ancient Egyptian goddess of fertility and magic)  that offered a similar interface to the Shimano Octalink standard, but with much more contact area between the crank arm and bottom bracket for a sturdier interface. The ISIS standard came to the marketplace in model year 1999-2000.

This SRAM Red 2012/Quarq power meter cranks show the ISIS splines peeking out just above the non-drive crank arm.

This newfound cooperation came at the same time the industry began to work together on developing disc brake standards that are still in use today. This spawned other cooperative efforts in creating the 1.5 headtube standard and chainguide standards, but that is another story. Even with this abundance of interindustry cooperation, all was not well in bottom bracket land. The dimensions of the ISIS spindle and the English bottom bracket shell, that every mountain bike had at that time, limited the size of the bearings that could be used in the cartridge ISIS bottom brackets. These minuscule bearings were not up to the task of supporting the abuse dished out during freeriding and downhilling and would quickly shatter. Chris King worked for years on developing an ISIS bottom bracket that would have the bullet proof reliability that all of their products are known for, only to give up after realizing that it was impossible given the constraints of the ISIS and English bb standards. By 2002 there was a growing consensus among riders that concurred with King’s view on the ISIS standard.

In 2003 the same coalition the developed ISIS began to push for a new, larger bottom bracket shell standard so that larger bearings could be made to fit around an ISIS spindle but remain inside the frame. The proposed standard was dubbed “Overdrive” and was instantly met with derision from both riders and the rest of the industry that was very resistant to adopting new standards at the time (imagine that!). In 2004 Shimano brought their Hollowtech II two-piece cranks and bottom brackets to market that solved the small bottom bracket shell issue by placing the bearings outboard of the frame, thereby making room for a spindle that was larger, lighter, and stiffer than both the ISIS and Octalink standards. This was the final nail in the coffin of both Overdrive and ISIS as a bottom bracket system. The standard lives on in another form as the interface for SRAM/Truvativ GXP two piece 24mm outboard bearing cranksets. It can also be found in Truvativ’s outgoing Howitzer standard three piece outboard bearing freeride cranks and bottom brackets.

An example of the 100mm shelled ISIS bottom brackets used on many fat bikes.

Today the only people still using ISIS cartridge bottom brackets on new bikes tend to be fat bike riders that require a crank that will fit the 100mm bottom bracket shell widths required to accommodate 4″ wide tires. The 100mm standard was developed as a downhill standard pushed by Tomac Cycles that conveniently worked for these weird but fun bikes. It helps that the old ISIS standard cranks and bottom brackets are very inexpensive for these franken bikes that are often built with very limited budgets.

There are a few ISIS bottom bracket manufacturers out there that are still making bottom brackets. FSA and Truvativ are going to be the easiest to find. Other manufacturers that made them in the past are Crank Brothers, Race Face, and SKF (there are a few more but these were the most common). You may be able to find NOS (new old stock) options from one of those companies. If you can find an SKF, they are the best in my opinion and were offered in both titanium and steel spindled versions. Between the FSA and Truvativ options still in production, I like the FSA Platinum ISIS bottom brackets best.

Daniel Slusser is a professional bicycle mechanic with over ten years of experience. He holds a bachelor’s degree in business administration from HSU and a master’s degree in history from Cal Poly University. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.