OliverMTB1999

Hi,

I’ve recently started getting into mountain biking. I’ve started with a decent budget hardtail but still keep running into issues. I’ve spent a lot on the bike and can’t really afford to keep up with the repairs! To save money I’ve decided to learn how to do these repairs myself.

I recently managed to strip all the thread from the crank arm so replaced it for a new shimano crankset. The only issue was the chain ring it is was slightly bigger. Just giving it a quick ride around it seemed alright but after taking it on trails I realised in gear 1 and 2 it catches really bad and now has a tendency for the chain to come off! (It’s an 8 speed box 4 by the way). I can’t tell where it’s catching because when I get off the bike and pedal it with my hands it doesn’t make the noise.

I thought it may be due to the chain being to small for the new chainring as the derailleur was a bit stretched out in those gears. I have since changed over the chain to a slightly longer one but still have the same issue. Can anyone advice what this may be? All the higher gears work great and I have no issues with those! There is a slight bit of movement in the crankset though I think it needs a small spacer but I’m not sure that would be causing it

thanks,
oli

Andrew R Stewart 

"Box 4 gearbox" is not a reference I know of. Is this a brand name or your term?

With incomplete data it's hard for us to diagnose long distance. Since I don't know the gear system I can't even begin to list the usual possibilities. If terms are a challenge I suggest going to the Park Tool co website and looking at their Big Blue Book or the Sheldon Brown site as a start. Andy

OliverMTB1999

Hi - thanks for the advice, sorry I think I just meant box 4, not box 4 gearbox! It’s an 8 speed and I think the box 4 part I was referring to is the derailleur, not quite there with my bike part names yet😂

Rolla

No offense, but I don't think you're going to save any money by attempting trial-and-error repairs on parts that you can't even identify. If I understand it correctly, you're having a problem with the derailleur dropping the chain -- which might be solved by adjusting the limit screws -- but if there's movement in the crankarms, you need to address that first. But I'm not at all convinced your chain is the right length or that your new crankset is even compatible. Instead of adding a random spacer (?), cut your losses now and take it to a shop.

Andrew R Stewart 

It's pretty common to spend more then a shop will charge for the first few repairs you do yourself if you're just beginning. The tools and the mistakes collectively add up quickly. It's when you do stuff a couple+ times that the costs start to even out and after a few more you are cost wise ahead. And you also begin to learn how to avoid some problems before they happen. Of course the more mechanical savvy the beginner the shorter the learning curve is and I tend to agree with Rolla that the OP hasn't expressed much skills in this area, problem solving and self learning. Sorry to say that out loud. Andy

dedhed

​​​​​​https://boxcomponents.com/products/b...lleurs-8-speed

Andrew R Stewart 

Thanks, I had searched with "box 4 gear box" and nothing bike related came up. Andy