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I'm new to cycling. I have a Soma Saga with SRAM X7 derailleur and Apex shifters. I have ridden about 200 miles on it.

When I'm cycling, sometimes my gears shift/jump to the next gear on their own. I lubed my chain but I'm not sure what or where else to check so shifting is smooth.

Any help is appreciated.

Thank you!🙂

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    After a few hundred miles your bike is due for a free tuneup from the dealer. – Daniel R Hicks Apr 2 '18 at 17:45
  • Thanks all! I had the cable wire tighten by a local bike shop. Did the trick! Much smoother shifting now. Now I can try to do it on my own. – Gabriel Panduro Jr Apr 5 '18 at 0:27
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There is a number of things that can result in bicycle gears 'auto shifting'.

The gear indexing could be out of adjustment, so that the chain is either getting caught by the next biggest sprocket causing a down-shift, or falling off onto the next smallest sprocket causing an up-shift. If the indexing is off enough to cause auto-shifting the chain would be making a lot of noise though.

Cables and housings may be dirty, worn or loose which causes the input at the shifter to not appear accurately at the derailleur.

There are many articles and YouTube videos available that will teach you bike mechanics (my personal favorites are from Park Tool). However, if you are not experienced with bike mechanics you will probably be best taking your bike to a good local repair shop. Ask the tech to explain what their diagnosis is and their recommended fix.

Update based on extra info:

New bike with ~200m very likely needs a post break-in tune up including adjustment of the gear indexing to account for cable stretch. Bike shops in the US at least (the extent of my personal experience) commonly do this for free,

  • Suggest "in the US" --> worldwide, or remove it completely. Any decent LBS will offer the post purchase tuneup. – Criggie Apr 3 '18 at 0:25
  • I personally only have experience of bike stores in the US – Argenti Apparatus Apr 3 '18 at 0:51
  • @Criggie - That's not true, unless "decent" means really good shop - 'cause I know lots of them with nothing like free tune up or a proper warranty – k102 Apr 3 '18 at 12:02

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