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New chain slipping

Why a New Bicycle Chain Can Slip on High Gears – And What to Do About It

When a new chain doesn’t mesh well with an older cassette — particularly on the smallest sprockets — it can slip under load. Here’s what causes it and what you can do next.


What’s Going On?

  • Chains and cassettes wear together over time. When you replace a stretched chain, the worn cassette may no longer fit the chain properly — especially the higher gears with fewer teeth. This mismatch is often only noticeable under pressure or during final test rides.
  • Even if chain wear measures within acceptable limits (e.g. 0.5?–?0.75%), wear on the cassette can still affect performance — dropping or skipping only on the hardest gears is a common sign.

Your Options

  • Replace the full cassette — ensures all sprockets mesh correctly with the chain. Going forward you know where you stand and can monitor chain wear effectively
  • Replace the top sprockets only – some brands/models of cassette are supported with replacement single sprockets, availability is also generally low so this is only an option for the lucky few. We will look for one to match your bike and let you know if it’s available.
  • (Refit the old chain), if it didn’t slip before — quickest fix if you absolutely need your bike back today. (Please note we strongly recommend AGAINST this option as the chain could start slipping, or snap at any time without warning.

What You Can Do in Future

  • Replace your chain routinely using a chain-wear tool: for 8–13-speed chains, consider replacement at around 0.5?% wear; if it reaches 0.75?% or more, plan to replace the cassette as well.
  • Clean and lubricate your drivetrain regularly — this slows wear and can help maintain gear accuracy.
  • Use easier gears under tougher pedalling loads and avoid sustained use of smaller rear cogs — they wear out faster when strained.

Why We Didn’t Spot It Earlier

This issue is subtle – unless there was obvious cassette wear (very hard to see) or the chain was slipping on the stand, it can be missed and often only becomes apparent once the bike is rideable and the chain is under load.


Summary

A new chain can slip on worn high gears — it’s rare but happens. The fix is usually replacing either the worn sprockets or the full cassette. Avoiding high-force pedalling in small cogs can help extend component life.


Need more convincing?

This article was written by Bike Man Dan with help from ChatGPT and the following sources:

https://bicycles.stackexchange.com/questions/14625/new-chain-causing-skipping-on-cassette-will-this-work-itself-out-or-is-it-unsa?utm_source=bikemandan.co.uk

https://www.bikeradar.com/advice/workshop/how-to-know-when-its-time-to-replace-your-bicycle-chain?utm_source=bikemandan.co.uk

https://www.reddit.com/r/bikewrench/comments/1lzl2ux/new_chain_slipping_on_cassette_on_certain/?utm_source=bikemandan.co.uk

https://www.velotricbike.com/blogs/story-landing/bike-chain-slipping?srsltid=AfmBOoraIHoX-djpbZJbFg0z92xKW5YMBh9YSjpeVLPq75KKuHAgQS88&utm_source=bikemandan.co.uk