Thursday 14 January 2021

1x (single chainring) conversion for Shimano 105 chainset

1x single ring Gravel/Cyclocross conversion for Shimano 105 chainset
This is my Shimano 105 chainset that I've converted to a 1x system.

Buying a brand new 105 chainset and then converting it to a 1x single chainring setup was, surprisingly, both cheaper and also lighter than buying a dedicated Shimano GRX 810-1 1x chainset.

Previously, I had a SRAM Rival chainset on my cyclocross/gravel bike.  I wanted to swap my Rival chainset for a Shimano one, so that I could then install a Stages Shimano power meter, which would be the same brand and type of power meter as what's on my road bikes.

If I had bought a Stages GXP power meter that would have been more expensive than the 105 power meter and also would not have been interchangeable with my other bikes.  Initially I planned to get Shimano GRX 1x chainset and a GRX or 105 power meter. However, I learnt that Shimano has created the GRX groupset to have a slightly wider Q-factor than the Q-factors of their road groupsets, like 105 etc.  This, again, would have meant the GRX power meter would not have been interchangeable with my other bikes, should I ever want to swap them around in the future (albeit with a Q-factor difference that is very small).

I decided instead that I'd get a new 105 chainset, convert it to a 1x single chainring set-up, and couple that with 105 Stages power meter.  Surprisingly, this 105 1x setup is both lighter and cheaper than the top level GRX 1x 810-1.  Comparisons are made against the more expensive and lighter 810 version of GRX.  Shimano also make a cheaper, heavier GRX 600 groupset too.

A comparison of prices and weights is shown below:

  Shimano GRX 810-1 42t      Shimano 105 1x 42t     Difference
RRP   £214.99         £186.59     £28.40
Current Wiggle Price   £179.99      £168.19     £11.80
Weight   656g      632g      24g

Cost and weight breakdown:
Shimano 105 5800 chainset without rings & bolts:  £154.99 RRP,  £136.39 current Wiggle price, 549g  
4 x chainring bolts:  £5.19 from Ebay, 6g
42t J&L wide/narrow chainring: 26.60 from Ebay, 77g
All 105 and 1x components were weighed myself.  GRX weights were taken from Shimano website


  1. What rear derailure and cassette did you use for this? does it work with the 105 levers?

  2. I still use the SRAM Rival cassette and rear derailleur that the bike same with. The bike came with a full SRAM Rival 1x11 groupset. I only changed the chainset to this Shimano 105 one, because the SRAM Rival one was fairly heavy. Changing only the chainset meant that I didn't have to change the cassette, the rear derailleur, the chain, or any other part of the SRAM Rival groupset. If you have Shimano 105 shifters, this chainset would be compatible with those, if you have a Shimano 105 or another type of Shimano road rear derailleur. As for the cassette, both SRAM and Shimano casettes are cross-compatible too, so either type would be okay.

  3. Can you kindly explain what you did to convert the 105 chainset to a single chainring set-up? I'd simply like to remove the front derailleur and second chainring on an existing 105 groupset...would an additional piece on the rear derailleur, like the Wolf Tooth Roadlink extension, then be required?

    1. Hi, To answer your first question, I wanted a single chainring set-up (a '1x setup') because this is my cyclocross/gravel bike, and 1x setup works very well for those kind of bikes. I couldn't use the Shimano 105 chainrings for a couple of reasons. Firstly, both of those 105 chainrings would be far from the size I needed. I use a 42 tooth chainring with my 1x setup, so the 105's inner 34t chainring would be too small, and the 50t outer ring would be too large. Secondly, and most importantly, the chainrings that come on double chainsets like the 105 are designed with teeth profiles that allow the chain to move slip off for one ring to another under the action of the front derailleur. Using one of those 105 chainrings as a 1x single chairing would cause the chain to fall off too easily. I tried that many years ago, and the chain regularly fell off, especially without a front derailleur to keep it on. Specific 1x single chainrings have alternating wide/narrow teeth, which keep the chain on very effectively, even not needing a front derailleur or chain catcher. I didn't change the rear mech or the cassette, which was already a 1x SRAM setup, hence no need for something like a Wolf Tooth Roadlink. This particular modification was purely a chainset swap, an old and heavy SRAM Rival single chainset changes to a much lighter 105 converted to a single chainring.

  4. I am in the progress of modding an old bike and I'd like to keep the current 1x setup for simplicity. I'd like to install a 105 groupset, but they only do a 2x for the crankset. So, all you had to do was remove the internal ring?

    1. Hi Marco, Yes that's right, I bought a compact double (2x) 105 chainset. When I say 'compact', I mean the version of the 105 chainset with smaller chainrings, a 34 tooth inner and a 50 tooth outer, which has a 110mm BCD. I actually removed both 105 chainrings then bolted the J&L 42 tooth single chain ring (which I bought from ebay, see: to the chainset using four 1x specific chainset bolts.

    2. Great, thanks for your reply!