GRX 10sp pull ratio?

Ive had a query from a friend who bought 10sp GRX rear mech, chainset, front mech.  She wanted to use her existing 10sp 105 shifters. She has fitted these items but the indexing is awful.

Does 10sp GRX have a different pull ratio requirement to a 105 rear mech? Is it correct that a set of 105 shifters (cable brakes) dont work with a 10sp GRX rear mech? She has been told that she needs Tiagra 10sp shifters but she isnt very convinced by this advice.

Can anyone shed any light on this problem?

Thanks

Ian

10sp GRX is ONLY compatible with the Tiagra 4700 10sp road stuff cos it still uses the 11sp pull ratio.

There’s a chart of it all here:

https://productinfo.shimano.com/#/com?cid=C-453&acid=C-454

4700 Tiagra was very much an anomaly in Shimano’s road groupset hierarchy, it’s different pull ratio to all other 10sp road.

Yeah, uses the leverage ratio of 11 speed components.

To use her existing 105 levers, she could use a 9 speed Shimano mountain bike derailleur, if she was looking for greater capacity. I think she’s out of luck for a compatible clutch derailleur, though.

Thanks all. I wasnt aware if the pull ratio anomaly

Ian

A 5702 10 speed 105 rear mech (still available) will cope with 34T cassette. Got it on my CX bike.

Still won’t work with the front mech though unfortunately.

It’s a good example of a know win situation. All current road and gravel 10 and 11 speed is the same pull ratio. So you can mix and match to your hearts content provided the shifters match the cassette for speeds. But that means losing compatibility to old road 10 speed

Is road 12 speed a different pull ratio?

I have found a mint 9sp XTR rear mech in the cupboard of spares for her! Im hoping that does the trick. She is flying to one of the ‘stans on sunday for a bikepacking trip with a couple of friends and i really need to get her 11th hr chaos into a functioning bike!

I have found a mint 9sp XTR rear mech in the cupboard of spares for her! Im hoping that does the trick.

Should do – I’ve got a 9sp XTR on my otherwise 10sp gravel bike and that’s got GRX levers. Works perfectly.

Thanks!

Should do – I’ve got a 9sp XTR on my otherwise 10sp gravel bike and that’s got GRX levers. Works perfectly.

Er, don’t the GRX 10 speed levers also use the 11 speed derailleur ratio?

(Irrespective of that, I’m sure 105 10 speed / xtr 9 will work)

Thread resurrection – so will GRX 2 x10 shifters definitely work with a 9sp Shimano MTB mech?

GRX 10sp and Tiagra 4700 use the same cable pull as Shimano 11sp, approx 2.8mm per click, whereas all other Shimano 10sp road shifters pull approx 2.3mm per click

Shimano 9sp MTB mechs have a cable pull to movement ratio of approx 1.7. i.e for a 2.3mm pull shifter each click moves  derraileur 1.7 x 2.3 = 3.91mm, Shimano 10speed cassettes have a 3.95mm pitch.

Therefore a GRX lever will move a 9sp derailleur 4.76 per click, which is almost exactly the right pitch for an 8 speed cassette which has 4.8mm sprocket spacing.

@ballsofcottonwool – many thanks ?

@Dickyboy Now you’ve got a reason to use that 8sp cassette from the bottom of the spares box you never thought you’d need agin

Now you’ve got a reason to use that 8sp cassette from the bottom of the spares box you never thought you’d need again

Unluckily I think I skipped 8sp and went straight from 7 to 9sp :-)

So what hydraulic brifters do I need look out for with a 9 or 10 speed monstercross set up?

Shimano have only ever made hydraulic brifters in 11speed and above apart from the 10speed GRX RX400 and Tiagra R4700 which use the weird cable pull. Theoretically your GRX 2×10 shifters should work with a GRX rd-rx812 which has 40/40T limit, allowing you to run a 11-42 MTB cassette. Because RD-RX812  is  an 11 speed derailleur you may need to use an 11sp chain so it doesn’t rub on the narrower cage plates. The internal width of 10 and 11 speed chains is the same, so no problems there.

There is no way to run a 9 speed with hydraulic brifters without using a JTEK shiftmate  9 to convert the cable pull.

I’m running mechanical Ultegra 10sp Brifters with a 9sp XT RD on a 10speed cassette, braking courtesy of Avid BB5 road pull mechanical disc calipers

I’m running mechanical Ultegra 10sp Brifters with a 9sp XT RD on a 10speed cassette, braking courtesy of Avid BB5 road pull mechanical disc calipers

Thanks again, was trying to avoid mechanical not because they are bad but because hydraulic are so much better, might try some of the mechanical to hydraulic calipers instead and see how I get on with them – or just stick with flat bars :-(

10sp 105 shifters

5700?

If so it’ll be a different cable pull ratio for both front and rear.

I recently goosed a 5700 front mech and ended up replacing it with a 6600 triple from the spares tub that just about fitted/worked with my double.

You’re after an earlier road front mech 6700/5700/4600 series or earlier.

4700 is the anomaly, using current road (11 speed onwards) pull.

GRX wasn’t about yet when 105 10speed existed.

If GRX 10s shifters are the same cable pull as 11s stuff you can achieve a bodge with a Wolftooth Tanpan and a 10s MTB mech. I used to have RS685s (11s) running a 10s Zee mech over a 10s XT cassette sing the tanpan. It wasn’t beautiful but it was entirely functional.

If you’re dead set on lower gear counts and hydraulics I’d probably just wait for Cues drop bar stuff though! Or microshift to add hydro options to Sword?