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I recently bought a used rigid mountain bike, I'm very happy with it but I realized yesterday that I couldn't access the smallest chainring.

This one has a total of 3 front gears, but only numbers 2 and 3 are accessible.

I tried to adjust the Shimano but nothing works, I can't use chainring 1. (I am a beginner not an expert)

Can the problem come from the Shimano? Should I look at something else?

Note: bike reference: B'TWIN Rockrider 5.0

enter image description here

Photo from priceminister.com

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    Welcome. It's not clear what you mean by "tray". That's not a standard term. A cpiture would help, or if this is a matter of translation, perhaps telling us your native language and the term you use. A thought: do you mean "chainring" as they can come in threes and are round and flattish – Chris H May 3 at 7:59
  • Tray 1 as in gear 1 on your crank? Then most likely the front derailleur is not set up correctly. There are two small screws on top of the derailleur-fastening to the frame. These are to set the upper and lower limits of the derailleurs movement, so your chain doesn't get pushed of the cog-wheels. – Erik May 3 at 7:59
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    @ChrisH In French we call it "les plateaux de vélos" I updated my question accordingly, thanks for your feedback. – Ced May 3 at 8:20
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    Yes, chainring then (Sheldon has a glossary). And actually plateau as in the English platter (a big plate) is similar to calling big cogs dinner plates in English. – Chris H May 3 at 8:24
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    Shimano is by the way a brand of bicycle components. I'm guessing "the shimano" means front derailleur here, but that part could be more readable with correct terms. – ojs May 3 at 9:06
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Your front derailleur is probably just badly adjusted, although there may be issues with the shift cable or housing, or potentially even the shifter.

I'm not sure if by 'chainring 1' you mean the innermost or outermost. If outermost the cable is probably just too slack so the shifter cannot pull the cage outward enough. If innermost something is preventing the cage from swinging inwards, perhaps too much cable tension or something is jamming it.

Adjusting front derailleurs can be a bit tricky as cable tension, limit screws and alignment all potentially have to be dealt with. Park Tool has a good series of videos on derailleur adjustment that walk you through the steps and explain what each adjustment does. Front derailleur video is on this page. It's a good idea to go through these steps as if the derailleur has been knocked out of alignment no amount of adjustment will fix it.

You can work through that but it's not entirely guaranteed to produce success. If you are a real bike novice find a good local bike repair shop and have them fix the problem. It would be a good idea to have them check the rest of the bike at the same time, especially brakes and rear shifting.

  • Unless something weird has happened, the limit screws should already be in the right place. Don't touch them unless you have some reason to believe they're set wrongly. – David Richerby May 4 at 11:35
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You could start by checking your shifters and cables are in good condition. If the cable is corroded, too much friction could be causing a problem.

  • I just realized that different version of the Rockrider 5.0 have been made, I guess I have the 2011 or 2012 version because I don't have any front suspension it is a rigid and not semi-rigid. I found a picture of the exact same one here – Ced May 3 at 8:35
  • This should really be a comment on the question, not an answer post, as it's asking questions not giving answers. – Argenti Apparatus May 3 at 13:52
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    Your more than welcome to edit or delete as required – Dan K May 3 at 15:55
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    This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. - From Review – ojs May 4 at 8:43
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    Edited to keep people happy – Dan K May 4 at 11:43
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There are two screws on top of your front derailleur:

enter image description here

They adjust, how far to the left/right your darailleur might move, and thus the chain. This is to prevent the chain from being shifted off the cogs, which is possible with the screws untightened and enough slack on the cable for shifting.

Vice versa, these also can prevent the derailleur from moving far enough to the right or left to push the chain onto the outer cogs. So, as in the picture, take a screwdriver and fiddle with the screws, until everything works. As stated, be careful not to loosen the screws too much, since this might result in the chain going off the cogs.

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    Erik, welcome. I think it would be better to suggest looking up guidance on how to adjust these ‘limit screws’ methodically, instead of implying slightly random fiddling. There must be instructions online. It’s certainly a good thing to look into. – Swifty May 3 at 11:10
  • Sure looking up is better/safer, but since we don't know OPs type of derailleur (and he probably also doesn't), fiddling and looking at examples is what we got. – Erik May 3 at 11:16
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    Sorry, but 'fiddle with it until it works' is not the expert advice we're looking for here. The OP has already done that without success. – Argenti Apparatus May 3 at 13:50
  • Well, feel free to guess without any further material provided by OP which screw he has to turn which direction how far. You can't. And if you don't like my wording, feel free to edit the post. Other than that, I stand by my post, since based on current data provided by OP, it is a valid answer. – Erik May 3 at 14:18
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    @Erik It's not the wording that's the issue. The issue is that you're recommending blindly changing stuff without understanding what that stuff does. Worse, you're recommending blindly changing the wrong stuff. The limit screws should have been set correctly when the bike was built and there's no reason they should have moved since then -- unless somebody was blindly changing stuff without knowing what they were doing. It's possible that the limit screws need adjusting but it's the least likely option. Sorry but your answer is plain bad advice. – David Richerby May 4 at 11:40

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