Off-Road / Cyclocross gearing

Trips, adventures, bikes, equipment, etc.
ike2112
Posts: 43
Joined: 19 May 2020, 10:57pm

Off-Road / Cyclocross gearing

Postby ike2112 » 1 Oct 2020, 10:18pm

I have a Ridley X-Night cyclocross bike that is ~7 years old. Its my winter bike for roads, but also my winter riding tends to be more inclined to path and trail detours.

Though its a top-spec frame, it was due to a factory mess-up (I actually ordered the X-Fire, entry level model at the time), so it came with 105 groupset and mechanical disc brakes. It's 46/36 chainrings and 10spd 11-28 casette.

The shifting is packing in - get chain rub on both ends of derailleur, and often struggle to get back from the 36 up to the 46 ring under load - its fine on the stand, but when pedalling it needs to be 'caught' just right. Bike shop reckon its time to replace bits - new crankset, new chain, or suggested might be as well considering new groupset as a whole.

I am already leaning towards overall upgrade. I'd always intended to upgrade the wheels at some point anyway.

However now that Gravel bikes are a thing, I'm thinking rather than just look at Ultegra and a more off-road hills friendly gear-ratio, GRX might be worth consideration. And hydraulic brakes.

But can I just stick GRX on an older CX frame? I presume if I replace everything, then a long cage rear derailleur means I can go for a MTB cassette on the back if I wanted and run something like 46/30 front and 11-42 rear? Or is that too wide a range and would cause chain rub?
EDIT: Think the Shimano site implies FC-RX810-2 has 48/31 chainrings, and could run it with an 11-42 cassette? Thats a huge range if correct...

I'd really prefer to have a granny gear, as some of the climbs I've done on my MTB were 20% and frankly I needed it, but I'd like to go back and try them with the cx bike. But I also want to have a decent overall range since the bike is still used on roads half the year.
Can I put 11spd parts on it even though it was originally 10spd - I presume the spacing involved is the same?

Single chainring options I presume the only pro there is less weight? I'd need a new BB for that I'd guess, and would end up with less gearing range.

Also in terms of wheels, with the age of the bike it's regularly dropouts not thru-axle. Can I still upgrade wheels (from Fulcrum 5 Sport) on hydraulic discs or would that only be compatible for thru-axle forks?

User avatar
LinusR
Posts: 442
Joined: 24 May 2017, 7:27pm
Location: London
Contact:

Re: Off-Road / Cyclocross gearing

Postby LinusR » 4 Oct 2020, 10:02pm

ike2112 wrote:I have a Ridley X-Night cyclocross bike that is ~7 years old. Its my winter bike for roads, but also my winter riding tends to be more inclined to path and trail detours.

Though its a top-spec frame, it was due to a factory mess-up (I actually ordered the X-Fire, entry level model at the time), so it came with 105 groupset and mechanical disc brakes. It's 46/36 chainrings and 10spd 11-28 casette.

The shifting is packing in - get chain rub on both ends of derailleur, and often struggle to get back from the 36 up to the 46 ring under load - its fine on the stand, but when pedalling it needs to be 'caught' just right. Bike shop reckon its time to replace bits - new crankset, new chain, or suggested might be as well considering new groupset as a whole.

I am already leaning towards overall upgrade. I'd always intended to upgrade the wheels at some point anyway.

However now that Gravel bikes are a thing, I'm thinking rather than just look at Ultegra and a more off-road hills friendly gear-ratio, GRX might be worth consideration. And hydraulic brakes.

But can I just stick GRX on an older CX frame? I presume if I replace everything, then a long cage rear derailleur means I can go for a MTB cassette on the back if I wanted and run something like 46/30 front and 11-42 rear? Or is that too wide a range and would cause chain rub?
EDIT: Think the Shimano site implies FC-RX810-2 has 48/31 chainrings, and could run it with an 11-42 cassette? Thats a huge range if correct...

I'd really prefer to have a granny gear, as some of the climbs I've done on my MTB were 20% and frankly I needed it, but I'd like to go back and try them with the cx bike. But I also want to have a decent overall range since the bike is still used on roads half the year.
Can I put 11spd parts on it even though it was originally 10spd - I presume the spacing involved is the same?

Single chainring options I presume the only pro there is less weight? I'd need a new BB for that I'd guess, and would end up with less gearing range.

Also in terms of wheels, with the age of the bike it's regularly dropouts not thru-axle. Can I still upgrade wheels (from Fulcrum 5 Sport) on hydraulic discs or would that only be compatible for thru-axle forks?


Do the frame and forks have "bosses" for hydraulic brakes?[edit sorry misread your post[/edit] I doubt if you will need a "granny gear" (triple chainset) as the wide range cassettes you mention with a double chainring will get you up pretty much anything. You can run 10speed GRX mechs, cassettes and cranks with 10 speed Tiagra 4700 shifters, which would allow you to use your existing brake set up and some of your old kit. You can build up disc wheels with regular quick release axles, no problem.

You should check the spacing of the rear dropouts. Hopefully they are 135mm - not 130. That way you can fit most rear hubs for disc braking, and 10, 11, or 12 speed.

freeflow
Posts: 1434
Joined: 29 Aug 2011, 1:54pm

Re: Off-Road / Cyclocross gearing

Postby freeflow » 4 Oct 2020, 10:58pm

As a first step I'd just replace the shifter cables with a nice set of jagwire cables and outers.

hamster
Posts: 3789
Joined: 2 Feb 2007, 12:42pm

Re: Off-Road / Cyclocross gearing

Postby hamster » 5 Oct 2020, 4:37pm

freeflow wrote:As a first step I'd just replace the shifter cables with a nice set of jagwire cables and outers.


Quite. I can't see why bad shifting requires new cranks. It's amazing how much shifting perks up with new outers.

mumbojumbo
Posts: 778
Joined: 1 Aug 2018, 8:18pm

Re: Off-Road / Cyclocross gearing

Postby mumbojumbo » 6 Oct 2020, 7:28pm

Try removing cables,rubbing with petroleum jelly,common in most homes,and replace,This will aid shifting-certaily you need noy buy a new groupset,What a con.

rfryer
Posts: 779
Joined: 7 Feb 2013, 3:58pm

Re: Off-Road / Cyclocross gearing

Postby rfryer » 7 Oct 2020, 6:36am

For GRX I'd double-check the allowed ratios. It's possible that when running 2x, the cassette must be considerably smaller than is supported when running 1x, maybe 11-34 rather than 11-42.

Roy A
Posts: 35
Joined: 28 Dec 2015, 7:41pm
Location: West Midlands

Re: Off-Road / Cyclocross gearing

Postby Roy A » 7 Oct 2020, 2:15pm

Are your shifting problems down to mis adjustment of the FD? This many also cause chain rub and lead to "struggle to get back from the 36 up to the 46 ring under load" could mean the stop screw needs easing slightly. Is the FD correctly positioned about 1 or 2 mm above the 46 ring? Shimano's instructions detailing setup and adjustment are available to download if you don't have the printed version.

Cleaning and lubricating the gear cables with silicone grease (as recommended by Shimano) should ensure less drag within the outer casing that may arise when oil or other greases are used that attract dirt and increase wear, and provide a smoother change generally.
King of Mercia, Giant Defy, Raleigh MTB, Brompton M3L & S6L

ike2112
Posts: 43
Joined: 19 May 2020, 10:57pm

Re: Off-Road / Cyclocross gearing

Postby ike2112 » 20 Oct 2020, 2:43pm

LinusR wrote:I doubt if you will need a "granny gear" (triple chainset) as the wide range cassettes you mention with a double chainring will get you up pretty much anything. You can run 10speed GRX mechs, cassettes and cranks with 10 speed Tiagra 4700 shifters, which would allow you to use your existing brake set up and some of your old kit. You can build up disc wheels with regular quick release axles, no problem.

You should check the spacing of the rear dropouts. Hopefully they are 135mm - not 130. That way you can fit most rear hubs for disc braking, and 10, 11, or 12 speed.


I've probably misinterpreted what the term "granny gear" means - I didn't realise it meant triple. I just thought it meant any gear more appropriate for a Mountain Bike.
I did a couple rides near Blair Atholl this year on my mountain bike with some ridiculously steep sections (over 20%), and my mtb 32 front 51 rear still had me barely making it up there. Hence moving to GRX 31 front small ring and max 34 on cassette at the back, it might be a 'ratio' of less than 1 and hence great for climbing on any normal local road riding I'd do, but I still don't think it'd be enough for me when I go do some steep hills and trails in summer.

As the bike was from the year 11spd came in, it takes either 10 or 11spd so I believe I can just switch to the GRX600 range (they don't have a full 600 groupset so seems some mix-and-match is always required).

ike2112
Posts: 43
Joined: 19 May 2020, 10:57pm

Re: Off-Road / Cyclocross gearing

Postby ike2112 » 20 Oct 2020, 2:53pm

rfryer wrote:For GRX I'd double-check the allowed ratios. It's possible that when running 2x, the cassette must be considerably smaller than is supported when running 1x, maybe 11-34 rather than 11-42.


Still confused to be honest!
My bike shop said no, that the 11-42 is 1x only...though that's the same shop that told me I need a whole new groupset when many responses above suggest I should start with new cables and outers
(and which is beyond my doing myself given the internal routing etc, so I'd now need to find another shop to even try it, to see if it fixed my issues).

Yet the Shimano own website doesn't explicitly state this is 1x only, nor explain. At the page here -> https://bike.shimano.com/en-US/product/ ... speed.html It lists all your part options (since they don't do a set 600 groupset for example, you have to mix parts, choose your cassette, rear derailleur etc). And from that it suggests I could used FC-RX600-11 2x11 crankset 46/30 and the Deore cassette CS-M8000 which actually goes up to 46 largest sprocket.
It lists further down the rear derailleur options, one of which is RD-RX812 - "GRX Rear Derailleur 11-speed (42T max low sprocket)".

And on this page https://road.cc/content/buyers-guide/yo ... set-271025 it also states "Riders choosing an XT, SLX or Deore-level 11-40/42 cassette need to use the longer cage Di2 RD-RX817 (pictured above) or mechanical RD-RX812, both of which come with a pull ratio similar to Shimano’s road derailleurs."
And someone in the comments noted:
"This weekend I will build a bike with what I thought would be full GRX but in the end it is only 3 parts from GRX - GRX 600 shifters/hope calipers, GRX 810 front gear, GRX 600 46/30 chainset, rear gear is long cage XT 11s mated with 11 - 42 XT cassette, a wolftooth Tanpan by the bars to convert the cable pull."
I have no idea what a "wolftooth Tanpan" is and i don't want this to get too complicated.... but if I can go 46/30 at front with 11-42 at the back I think I'd be happy with that. Might feel like there's some gaps in it, but that would be a hell of a range to put on a light racey CX frame that I can fire around the MTB trails on.

mattsccm
Posts: 3679
Joined: 28 Nov 2009, 9:44pm

Re: Off-Road / Cyclocross gearing

Postby mattsccm » 20 Oct 2020, 5:34pm

How low do you really need? You have a typical off the peg CX chainset. Low gears are not needed in CX as you get off and run if the hill is that steep or the mud/sand that claggy.
If you are using it as an off road knock about you could proabably just stick a 34 chain ring on and a 11-32 cassette. Even a short rear mech will just cope , expecially if you keep the 46 outer which is quite nice if you don't spin out. Chain rings are usually cheaper than chainsets although its surprising how these things are not always as you would think.
One alternative if you don't want the higher gears might be a MTB double, usually in 28/42. With an 11-32 cassette you get wall climbing gears. This could be made out of a triple ignoring the outer ring. An older style 28/38/48 chainset can be used withe the 28 and 38 .
All of this means no other changes aprt from the cables which are probably shot plus cassette and chain which are probably needed anyway.
1x suits some people, especially thos from a MTB background but it does use a very gappy cassette.

ike2112
Posts: 43
Joined: 19 May 2020, 10:57pm

Re: Off-Road / Cyclocross gearing

Postby ike2112 » 20 Oct 2020, 6:40pm

mattsccm wrote:How low do you really need? You have a typical off the peg CX chainset. Low gears are not needed in CX as you get off and run if the hill is that steep or the mud/sand that claggy.
If you are using it as an off road knock about you could proabably just stick a 34 chain ring on and a 11-32 cassette. Even a short rear mech will just cope , expecially if you keep the 46 outer which is quite nice if you don't spin out. Chain rings are usually cheaper than chainsets although its surprising how these things are not always as you would think.
One alternative if you don't want the higher gears might be a MTB double, usually in 28/42. With an 11-32 cassette you get wall climbing gears. This could be made out of a triple ignoring the outer ring. An older style 28/38/48 chainset can be used withe the 28 and 38 .
All of this means no other changes aprt from the cables which are probably shot plus cassette and chain which are probably needed anyway.
1x suits some people, especially thos from a MTB background but it does use a very gappy cassette.


That's the thing - I use the bike for different things. Everything except actual cyclocross (I bought it before gravel bikes were a thing, when cx was your standard all-rounder option).
Its my winter bike so is used for weekend rides and occasional commuting, often with old wheels and thick road tyres. Hence currently the 46/36 chainset and 12-28 is handy enough as road gearing; there's decent climbs near where I live but in winter I'm not expecting to get up them quickly. Sometimes I'll put the cross wheels back on a go on some trails.

But in the summer I use it to do some stuff that is usually more for mountain bikes - I rode up the majority of a munro this summer, then around the side of some other ~1000m hills. I did other nearby hills on the mountain bike as I knew I'd never make it up them on the CX. Some of this is paved but easily over 20% in sections, other bits are maybe 2km at 8% avg and gravel/loose stones. Its pretty hard, and I needed all of the lowest 32-51 mountain bike gearing to get up the harshest parts.

So with that in mind having a highest gear of 48-11 and lowest of 30-42 is perfect for literally every possibility. Messing about with mountain bike chain rings etc seems even more complicated - and I'm not even that bothered about cost/budget. Have already sourced all the parts from various places if full groupset was needed, and am ok with cost. I just don't quite know what is all compatible.

rfryer
Posts: 779
Joined: 7 Feb 2013, 3:58pm

Re: Off-Road / Cyclocross gearing

Postby rfryer » 21 Oct 2020, 3:21am

ike2112 wrote:
rfryer wrote:For GRX I'd double-check the allowed ratios. It's possible that when running 2x, the cassette must be considerably smaller than is supported when running 1x, maybe 11-34 rather than 11-42.


Still confused to be honest!
My bike shop said no, that the 11-42 is 1x only...though that's the same shop that told me I need a whole new groupset when many responses above suggest I should start with new cables and outers
(and which is beyond my doing myself given the internal routing etc, so I'd now need to find another shop to even try it, to see if it fixed my issues).

Yet the Shimano own website doesn't explicitly state this is 1x only, nor explain. At the page here -> https://bike.shimano.com/en-US/product/ ... speed.html It lists all your part options (since they don't do a set 600 groupset for example, you have to mix parts, choose your cassette, rear derailleur etc). And from that it suggests I could used FC-RX600-11 2x11 crankset 46/30 and the Deore cassette CS-M8000 which actually goes up to 46 largest sprocket.
It lists further down the rear derailleur options, one of which is RD-RX812 - "GRX Rear Derailleur 11-speed (42T max low sprocket)".

And on this page https://road.cc/content/buyers-guide/yo ... set-271025 it also states "Riders choosing an XT, SLX or Deore-level 11-40/42 cassette need to use the longer cage Di2 RD-RX817 (pictured above) or mechanical RD-RX812, both of which come with a pull ratio similar to Shimano’s road derailleurs."
And someone in the comments noted:
"This weekend I will build a bike with what I thought would be full GRX but in the end it is only 3 parts from GRX - GRX 600 shifters/hope calipers, GRX 810 front gear, GRX 600 46/30 chainset, rear gear is long cage XT 11s mated with 11 - 42 XT cassette, a wolftooth Tanpan by the bars to convert the cable pull."
I have no idea what a "wolftooth Tanpan" is and i don't want this to get too complicated.... but if I can go 46/30 at front with 11-42 at the back I think I'd be happy with that. Might feel like there's some gaps in it, but that would be a hell of a range to put on a light racey CX frame that I can fire around the MTB trails on.

See here, where it says the capacity of the long cage rear mech is 31 teeth, which matches an 11-42 cassette. If you wanted to run 46/30 with 11-42, you'd need a rear mech with a capacity of 47.

ike2112
Posts: 43
Joined: 19 May 2020, 10:57pm

Re: Off-Road / Cyclocross gearing

Postby ike2112 » 21 Oct 2020, 6:18pm

rfryer wrote:See here, where it says the capacity of the long cage rear mech is 31 teeth, which matches an 11-42 cassette. If you wanted to run 46/30 with 11-42, you'd need a rear mech with a capacity of 47.


Thanks, though not sure I understand. How is the 31 teeth calculated? Is it some sort of combination of the front and rear largest rings?

rfryer
Posts: 779
Joined: 7 Feb 2013, 3:58pm

Re: Off-Road / Cyclocross gearing

Postby rfryer » 22 Oct 2020, 5:21am

ike2112 wrote:
rfryer wrote:See here, where it says the capacity of the long cage rear mech is 31 teeth, which matches an 11-42 cassette. If you wanted to run 46/30 with 11-42, you'd need a rear mech with a capacity of 47.


Thanks, though not sure I understand. How is the 31 teeth calculated? Is it some sort of combination of the front and rear largest rings?

The capacity is the difference between the largest and smallest sprockets, plus the difference between the largest and smallest chainrings.

It is a statement of how much chain slack the rear derailleur is designed to take up. The stated figure can often be exceeded in reality.