GRX crankset query

[Lostcause]

Does anyone know if GRX crank arms are the same on 1x and 2x? I have some 170 cranks which are the perfect length for me but they are 2x. Is it simply a case of bolt on the desired size of 1x chainring ?
Thanks in advance…

 

[Sharky]

I'm pretty sure that it is a simple case of fitting a new chain ring. Try and get a narrow/wide chainring when you do. Helps to stop the chain from escaping.

 

[wafter]

The Shimano diagrams for the 810 and 820 seem to imply the same crankset is used for both 1x and 2x applications..

 

[ColinJ]

When I turned a Shimano setup into a 1x, I had to buy a set of shorter chainring bolts and some washers to compensate for the missing ring. Without them I couldn't tighten the bolts to hold the single ring in place.

 

[ColinJ]

I probably should have bought a narrow/wide chainring because the bike started dropping the chain on a regular basis after the conversion. I fixed the problem by using the redundant front mech as a chain guide. (No cable attached, just held in position by one of the endstop screws.)

 

[ktmbiker58]

When changing to a 1X setup it's worth spending a bit of time ensuring that the front chain ring is as central as possible to the middle ring in the cassette, with threaded BB it's sometimes the case that there are spacers either side which you can swap around to move the crankset over. The bend in the chain is more extreme with a 1X than a 2X (as long as you aren't cross chaining) which can lead to the chain dropping off the front chainring in top gear (where the chain tension is lowest) or dropping off the bottom gear ring especially if you back pedal in bottom gear.

 

[wafter]

When changing to a 1X setup it's worth spending a bit of time ensuring that the front chain ring is as central as possible to the middle ring in the cassette, with threaded BB it's sometimes the case that there are spacers either side which you can swap around to move the crankset over. The bend in the chain is more extreme with a 1X than a 2X (as long as you aren't cross chaining) which can lead to the chain dropping off the front chainring in top gear (where the chain tension is lowest) or dropping off the bottom gear ring especially if you back pedal in bottom gear.

I'd caution you against spacing the crank at the BB to correct chain line as this will also offset the crank arms relative to the bike's centreline which can't be good for ergonomics.

The chainrings bolt to the inside of the crank so if you need to reduce chainline you can fit spacers between the crank and ring, using appropriately longer chainring bolts.

 

[Lostcause]

Thank you all very much 👍

 

[ktmbiker58]

I'd caution you against spacing the crank at the BB to correct chain line as this will also offset the crank arms relative to the bike's centreline which can't be good for ergonomics.

The chainrings bolt to the inside of the crank so if you need to reduce chainline you can fit spacers between the crank and ring, using appropriately longer chainring bolts.

We are only talking a couple of millimeters which is no big deal , unless you are Mr Pogacar maybe, (human beings aren't generally made to those sort of tolerances )

Fitting spacers between the crank and the ring often isn't straightforward, you need to watch out that the barrel of the chainring bolts is the correct length to pass through the crank arm, spacer and chainring - but not too long that it prevents the whole assembly from being properly clamped - I've ended up with bag fulls of bolts from my various experiments!

 

[mtpthi]

Yes, the GRX crank arms are the same between 1x and 2x, it's mainly the star and the chainring that change. I did the same with a 2x crankset by mounting a 1x chainring without worry. Just check the BCD and the chain line.

 

[oxoman]

Yes definitely the same. Converted mine to 1x11 with wolf tooth 38t nw fitted.

 

[Lostcause]

Thanks a lot chaps, that’s reassuring 👍