Is it easily possible to install a 2x GRX crankset and BB in a 73mm English threaded BB shell?
In other words, is the crank wide enough to fit?
Nope. Not easily. Max width spec is 70mm/Italian BB standard.
The White Industries crank is a good option for people doing gravel builds on a 73mm BB shell.
Thanks for the info.
Not sure if this is the case, but a 2x GRX crankset is narrower than a typical shimano 2x MTB crank, is that correct? In terms of the distance between the centerline of the bike and the chainrings. If yes, do you know by how much?
The reason l ask is l am wondering if l can get a GRX FD to shift properly with any 2x crank that l can mount on to a 73mm threaded BB shell.
It all comes down to axle length.
Correct, but good quality shimano cranks have fixed spindle lengths.
That’s why a GRX crankset won’t fit in a 73mm bottom bracket.
GRX is +2.5mm chainline compared to standard road.
The first question you need to answer is what is the chainline of the crank you are wanting to use?
And then is this within the range of the derailleur, which it probably is.
Remember though that the expected front ring size is 46-48, 30-31, so the contours of the cage may not suit a smaller MTB ring.
Why not use an MTB derailleur?
Yes, l understand that.
But, to ask again, how does the GRX chainline compare to shimano 2x MTB cranks?
GRX is +2.5mm chainline compared to standard road.
So I waded through the shimano tech docs site.
It looks like GRX is ***not ***+2.5mm compared to road.
Shimano road chainline = 43.5mm
Shimano GRX chainline (2x) = 46.9mm
So the difference is actually 3.4mm.
Kinda weird because all of the marketing info I have seen also mentions the 2.5mm number …
There are some conflicting numbers on the Shimano website for sure. Page 5 of this document from Shimano clearly states it’s +2.5mm vs. conventional road. I haven’t actually measured the chain line on my GRX crankset so I’m not sure what’s correct.
https://bike.shimano.com/content/dam/productsite/shimano-northamerica/pdf/GRX%20DOC%20CONSUMER.pdf
Yup, shimano FDs show that +2.5mm chainline difference (GRX vs road).
But the cranksets clearly show (according to published shimano specs) a +3.4mm difference (GRX vs road).
Just called shimano and their rep had never been asked this question before … but he says he is going to do some research and get back to me.