Every cyclist needs an accurate chain wear checker that is simple to use. Trying to measure manually with ruler or calliper is time consuming and often inaccurate as one is trying to eyeball to fraction of a mm accuracy.
An accurate drop in checker allows for quick, easy and therefore very importantly – regular chain wear checking.
I used to stock the Unior however first they turned the tools black making graduations impossible to read. I tried their dial checker but it was wildly inaccurate.
Over the last 12 months in conjunction with many customers I have assessed many brands chain wear checkers, and a common problem is accuracy from one tool to another. Many are cast and finished or simply cut to very rough tolerances, and for a tool where every 0.1mm really, really matters – they just don’t pass muster. I have had numerous situations of customer tool reading 0.75, only to find when checked with digital checker or shimano Tl-CN-42 that it is only around 0.25 etc. Worse is a tool that under reads meaning you will have a chain run too long and eat into your cassette and chain rings.
The shimano TL-CN-42 is laser cut and many have been checked over last 12 months and all have been exact – hence, finally ZFC is happy to endorse and stock this as the most important tool in your workshop.
**NOTE especially for drip lube users – Chain wear rates are NOT LINEAR. Initially a quality chain will have wear protective treatments such as a low friction coating and one version or another of chromium plating on some components. As these coatings / plating’s become compromised from wear, AND typically the amount of abrasive contamination deep inside chain builds over time, people get caught out doing a check at “X” kms to find chain wear is minimal, and then again at same km’s later to find chain has ripped past recommended replacement mark.
Regular chain wear checking is simply a very good habit to get into and always err on replacing chain early – your chain is a consumable part like your tires and brake pads, and your chain is responsible for the lifespan of your drive train components.
When a chain is within wear tolerance, the rollers slot neatly in between chainring and cassette cog teeth, and then by the time rider load is introduced, they are pressed into tooth face with force laterally transferred into tooth. When chain is worn (stretched) beyond tolerance which is at 0.5%, what happens is now the rollers start to catch the tip of chain ring / cassette teeth and slide down the face vs neatly slotting in. A chain past this wear tolerance will have no wear protection left and will now be quickly wearing to greater and greater length, and it will merrily be eating through your cassette and chain ring teeth as it does so.
Wearing through the metal cogs and chain rings on your bike is not low friction running, and its can be fudging expensive.
Rule of thumb #1 – Check chain wear regularly and check at least 3 to 5 sections of chain each time as chains do not wear evenly.
Rule of thumb #2 – Replace chain just before or at 0.5% wear when any section of chain is reaching this point.
Rule of thumb #3 – The more expensive your drive train components (cassette / chain rings) – the more you really, really need to get into the habit of doing rule 1 &2
Rule of thumb # 4 – If you are running expensive drive train components – STRONGLY consider running two training chains. You are always going to need another chain, so pre buying next chain to have two on rotation costs no more. Running two training chains on rotation ensures you will get two chains through your cassette. Many high end cassettes are a titanium alloy vs steel (especially the larger cogs) and these cogs have poor wear resistance. Many are caught out with only getting a single chain through a cassette even if replace at 0.5%. Also, running two chain on rotation makes it easier to maintain chains better – should chain 1 have been caught in a wet ride where front tire has hosed chain with dirty road water, or its been a particularly dusty gravel ride etc and you have another cool ride the next day, this enables your to pop chain 1 off, pop chain 2 on, and then give chain one a proper flush clean or re-wax to reset contamination, friction and wear of that chain (and saving expensive drive train components from the same). There are simply a number of great benefits to running two chains on rotation vs just hammering the one, and the benefits increase the higher the cost of your components, and this tool will also be your trusty guide to help keep you lovely components seeing multiple chains for cassette, and typically 5 or 6 chains per set of chain rings.