I built myself a new road bike a few months ago and when I try and use the 12/13 and 39 rings the chain rubs on the inside edge of the 53 out ring and makes a horrid noise.

Now I was wondering whether a shim on the inside of the drive side bb cup will push the chainset out slightly and therefore reduce the chain angle from the rear sprockets to the inner front c/ring

Or should this combination never work?

Thanks

Not uncommon for rubbing IME, I doubt a spacer will help.

Big-ring time.

You usually cant fit spacers to road bikes as clearances are typically too tight. But as above, changing gear is the way everyone else deals with it (if you read the instructions that come with your gears, who does?, itll show you that those gears are ‘not recommended’ for use).

it is the result of short chain stays and it one of the reasons why you don’t use that gear combination.

I added some brass washers to the ring bolts one one of my bikes to widen the space because of a similar issue. Worked a treat, took a while to get the front derailleur set up though.

that can really **** up your shifting.

I just switched from a standard c/set to a compact 50/34 and I find that I want to use the 12/13 sprockets a lot more than when I had the 53/39 c/set

Very annoying

Its your gears trying to tell you not to use that combination.

Straighter chainline -> more efficient and less and ware stress on components.

39/12 ~ 53/16.