New gravel bike (GRX single conversion)

My first gravel bike came 2x10, and I switched it to a GRX 812 rear mech and 10sp Deore cassette - with a GRX 600 1x chainset to replace the shagged FSA 2x one.

That worked really well, and would save you the big expense of new brifters.

I have 2x GRX on my newish Gravel bike, I deliberated for a long time over 1x or 2x as I have only used 1x in recent years on mtbs (never been a roadie). I live in a very hilly area, so was convinced by the argument of 2x giving me a bit more flexibility and some lower gears for spinning up hills. It works really well and I have no issues with the front mech rubbing, unless completely cross chained when it does slightly.

I have 30/46 chainrings and an 11/36 cassette.  12 speed. I can spin out on the road a little if I really try to get a lick on, but as I'm not racing or group riding that's rarely an issue for me. I did have the front brifter fail soon after getting it, that was quickly replaced under warranty.  Other than that, I've had to tweak the gears a few times since new, as cables have stretched, nothing more than a quick twist of the barrel adjuster though.

Overall very happy with the set up for the kind of riding I do.

TBH I'd persevere with the front mech setup. There's no inherent design issue preventing it being a good setup. 

My gravel bike came with 610 1x12 shifters and a 40T chainring.

I swapped to the 820 shifters as I wanted the integrated dropper lever. I also fitted a 38T chainset to work with the 10-51 cassette.

Does mean that I now have 610 1x12 shifters, 172.5 40T 610 chainset and a pair of 400 brake calipers cluttering up the spares bin.

Came fitted to the bike, but never ridden.

Posted by: jwildcard

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I have had issues with the front mech running smoothly in the workstand due to what looks like a very tight tolerance with the clearance on the mech.  ...this 10spd grx set up it looks much tighter where I am getting rubbing in 4 gears in the big ring even after a lot of adjustments

You are aware of the 'trim' position are you? Push it firmly into the big ring for the higher end of the cassette, and a 1/2 click back for the lower gears. I'm not going to claim any superiority on this because I dicked about with an Ultegra gearset on a road bike for about 18 months before I happened on this by accident. 

Wildcard entry, buy a broken 11 speed shimano hydro (105/grx600)shifter and move the 11 speed mechanism into your current right hand lever (one pin, one bolt and slide it out). Then fit a single front ring + your choice of 11 speed cassette (grx 400 rear mech works fine with 11 speed). Alternatively you can get a 11-40 shimano 10 speed cassette (deore iirc) and use the 10 speed grx shifters with a single ring and the wider range cassette. That would probably be the lowest cost/hassle option outside getting what you have to play nicely.

That coming mech should work. It sounds like it’s at the wrong height. Start from scratch witha  youtube video or the original pdf from shimano. Or get who supplied the bike to get it working

You can use an grx rear mech. So Ranger is not an issue, there are 11 48 is available in 10 speed

Thanks a lot everyone here for the suggestions. Sounds like there are several options then here. Regarding my current setup (46/30) double chainset, most the gears don't rub in the 30 ring, chain line wise of course it's a stretch. Regarding the bigger ring yes with the trim function I can get more out of this set up, where I am having an issue is having  11spd 105 and ultegra on my road bikes I can get 90% of the combo without using the trim at all. I find the trim a bit of a pain with this 10spd set if I'm being honest. It's usable but is a factor in me posting this situation and also maybe the constant changing of front end gears. I would even say if my ring was even a 36t front I would probably have a decent range of gearing without needing to switch between a small and big ring. For sure I am now overthinking it a little bit as I did have issue setting up the front mech at first but find on this 10spd version it's tighter and finer tolerance wise. I think the 11 chain is thinner, certainly my R7000 front mech runs a lot easier clearance wise it seems on my road bike. 

I think I have ridden enough gear wise to know that the single may be my preferred option now moving forward albeit with a bit of inconvenience setting up. I was coming I think from a road bike mentality with the gearing. My other older MTB is actually a triple Deore LX chainset running 9spd where I use pretty much the middle ring only (36t) with an 11-30 cassette. With this gravel it is a little faster rolling with the tyres and wheels and position but generally similar. 

I have had another go at setting the front mech up but just not comfortable riding the bike with this set up. In small ring I get about 7 of the gears and the final three small cogs rub then when switching to the big ring it rubs from middle of the cog upwards unless using trim. It just seems old unlike my 11 speed double the tolerance is less with this setup. I've wasted a lot of time already trying to sort this now. I think gear wise I am looking at getting a 40t Front ring, it's a pain having to replace the rear mech too but the grx400 only accommodates to 36t I think. Would I be best going for another grx model if I am looking at running maybe an 11-42 cassette or maybe go 11-46 and then maybe go 42t front ring. My set up is 10speed though. Apologies if I am repeating myself a bit here but just re looking at these options and trying to get it right. 

I get about 7 of the gears and the final three small cogs rub then when switching to the big ring it rubs from middle of the cog upwards unless using trim.

Well you get such a massive overlap of ratios between the big and small rings, and if the trim works in the big ring, I'm failing to see the problem. 

You could try stretching the cage a little wider. 

7/10 gear combos spinning cleanly is how it’s meant to work. You’re not meant to cross chain. If you want to shift into that 8th sprocket, it’s better to get the same result by shifting chainring instead, and to the 6th sprocket to minimise the jump.

I’d try the existing mech on a 42 before buying a different mech. The no brand gear hanger extenders are cheap as chips

Yes, I had a ride out yesterday morning to see how the gears were ratio wise and found myself being between the two rings at times. When shifting up and down I then had to trim. Ideally I just want to ride and relax and not think about the shifting (trimming) on my road bike it was rarely an issue as I could get most of the gears without the trim on my 2x11 set up and didn't go big ring deep n the block much, especially riding solo mainly. 

I do have a new 10speed Deore 11-46 cassette currently I had purchased for a MTB last year but I think that would be pushing it. As you mention the 42t would be the better option, I have read they can sometimes be used with the grx400 though I thinks it's quoted at 36t maximum. Ideally I wouldn't want to swap the mech and chainset out. Regards the chainset I am looking at a 40t single ring option. Sometimes the chainrings cost what the chainsets cost from what I've seen? I have a GRX 600 double, will that take a single GRX ring or better to go with another manufacturer depending on price? I also have a R7000 chainset which I thought about using for the reason in also have a Power meter arm for that and could potentially use that also if not using the road bike as much thesedays but just a thought. 

I feel like you're seeking validation now for a decision you've already made, in which case, go for it. You can always put all the existing kit back on if it doesn't work. 

Yes, I must admit I had moved over to the idea of the single speed option. Having back tracked at the weekend due to the inconvenience of buying the new kit (chainring, cassette & rear mech to go to single. I was tempted to try initially just getting a single chainring set up for the front and trying an 11-42 Deore cassette at the rear but the more you research these things the more complex it can get. I've heard the GRX 812 is the optimum mech system for the single ring option which is a bigger outlay cost wise as well as the other changes mentioned. Yes it may well be worth it though if I get nice shifting and less stress with the setup. I think I have exhausted the setting up of the current set up and I think mentally it has become a pain about the trimming etc. when switching from small to big and big to small the tolerance is definitely different to my ultegra/105 systems (2x11) where minimal trimming was required, only on big big for those last 3 gears so not an issue. 

I have had a mechanic try and improve on how I had the mech setup just to definitely get the best out of it ideally, there is a slight improvement but even with what seems the optimum setup now with this front mech the chainring options aren't what I am after. I think ideally I would prefer a 36/46 set up as I could stay in one ring (small for more of the time on more off road riding and keep a slightly better chain line. Of course I would lose a couple of gears for extreme hill climbing but I have ridden an MTB for a long time using a 36t chainring and I am pretty comfortable with that. So this leads to me to now two options, one is to switch to a standard road style chainset with cyclo cross rings (I already have a RS510 with a 46 big ring tho I think the small is 34t so would need to switch to a 36t which is cheap to do And leave the 11-32 cassette. Or I can go for a GRX 812 double and fit an 11-42 Deore cassette on which I also already have as a possible switch also. With this option I would need a new single speed chainring (I was thinking either 38t or 40t) any recommendations on that? Would it need to be a narrow wide I assume for single ring and is it best to stay with something like a Shimano GRX version or a high grade brand. I've seen a few budget ones but never used a single speed set up so no experience on the differences in performance and quality. I also have a R7000 chainset that i could use or could use the existing GRX600 and take the double rings off. Has anyone done either of these? If I can get a deal on the GRX 812 I am pretty swayed to the single option as I just think it may work moving forward and put this situation to bed.

I wonder if this is more a case of unfamiliarity rather than "the wrong gears"?

My main bike has a 3x10 triple with a 22T granny ring & an 11-36 cassette; I've been ridding it regularly for going on for 8 years and I'm really attuned to it.

I built myself a steel gravel bike with RX400 group set (46/30 & 11-36). It's a rather lighter but more highly geared bike and I've really been struggling with climbing in the 30T inner, it just feels harder somehow & I think that psychologically I'm a bit fixated on the fact that I'm in a 30T ring not a 22T (even though my HRM shows that I'm not really putting in the effort).

I have fitted a 28T inner but I'm realising that really I just need to ride the (very much a different) bike & get used to new gears & cadences.

I would agree that the RX400 front mech. is a pain to set up cleanly. It also seems to need an awful lot of cable tension to work properly in the Trim positions.

If you want to go down the 1x route Bike Discount have an RX610 1x12 group set for less than £500 but it does seem a lot of cost & expense for something that might work.

https://www.bike-discount.de/en/shimano-grx-rx610-1x12-speed-group-disc-160/160mm

Posted by: jwildcard

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I think ideally I would prefer a 36/46 set up as I could stay in one ring (small for more of the time on more off road riding and keep a slightly better chain line.

We did a thread on this a while ago actually '2x GRX - Are you ever in the right ring?' and I think you're reaching the same conclusions as a lot of us did on that thread!

I've gone 46/30 with an 11-36 cassette and although it has improved things I'm still thinking about a 44 tooth chainring for the front, TA Specialites do one for GRX but it would mean bodging the front mech a bit as I'm already at the bottom of the braze on so it can't go any lower. As it happens I've decided that my gravel bike isn't the best tool for the job on bigger hillier days so I've gone 2x on the 29er (38/28) and will go 1x on my next gravel bike and keep it for lower level smashing around when gear range isn't as important.

Are the chainset and front mech both GRX? Remember that GRX 2X chainsets & front mechs are spaced 2.5mm outboard of Shimano road kit. I tried to make an Ultegra front mech work when swapping a 50/34 Ultegra chainset for a 46/30 GRX. The Ultegra mech ran out of outward travel and I had to buy a GRX front mech. You may have the opposite problem?

You don't usually need anything special for a NW single ring, if you decide to do that, cheap ones are fine. However, I think there's something specific about the grx hole spacing, maybe an asymmetry, that means you need to be sure it is grx compatible.

I bought a couple of aftermarket big cogs recently from wolftooth and stone, that fitted fine. Or you could just get a shimano one.

Thanks for the info, I also have an R7000 chainset which I have seen also make a good conversion to single speed for the single ring setup. I have seen some for very low pieces (from China I think) for £10-£14 and then the wolf tooth and Shimano and ta special around £60ish. I am thinking maybe a 40 over the 42 as looking to go 11-42 cassette though I hear the GRX 812 will take a 46t rear. I think gearing wise I like the slightly smaller ring of the 40t, had even considered 38t but 40t should be about there. 

Posted by: tthew

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I feel like you're seeking validation now for a decision you've already made,

Very much this.

Garbaruk will do a 38 tooth ring with the necessary offset to run a 2x chainset as 1x, I've successfully been running a 2x GRX 600 chainset as 1x on the CX bike this way

Thanks for the mention of the "grx am I ever in the right ring" thread. I can relate to that and coming from road with the double set up I think dropping down to a 30 on the inner explains this. I have worked out rear cassette and mech options still running 10speed for a single ring conversion. Chainset wise I am thinking of switching the GRX 600 out initially and putting a R7000 105 spider in. Reason being I may be using the power meter 4iii set I have over winter. Are the Shimano RX810 rings compatible with the 105 chainset, I think they are with the RX600. I see there are a few options on single NW chainrings. At this stage thinking 40t . I could always adjust it if need be in the future but that sounds about right.