Chainlines and 12 speed - 2 quick questions

[cameron_15]

Hi All,

Been somewhat out of the game for a while now and standards are getting the better of me.

I've just purchased a new to me norco sight 2016 model with iscg 05 tabs and MRP chainguide. I want to swap this chainguide with the one on my 2016 specialized enduro. I thought this would be fine, both are non boost frames but the chainline appears off. Namely the guide from my enduro rubs on the inside surface of the norcos chainring. Not by a little, by a lot!

My assumption is that ISCG tabs/guides are a universal fit and not boost/non boost or bottom bracket specific? I must be wrong?

Also whilst we're here, can I run a 12 speed mtb cassette on a regular 8,9,10 speed hyperglide freehuh body or does it need to be 12 speed specific? I'm wanting to do a 1x12 conversion on my partners bike but don't want to buy a new wheel or hub body.

Thanks for the advice, I must be getting old.

 

[Lucaw]

Only nx or sx cassettes will fit on a hg freehub

 

[Mattyp]

Only nx or sx cassettes will fit on a hg freehub

Aswell as the other 12speed cassettes that are made to fit a HG freehub...Garbaruk, Sunrace, ztto to name a few.

 

[beeb]

Hi All,

Been somewhat out of the game for a while now and standards are getting the better of me.

I've just purchased a new to me norco sight 2016 model with iscg 05 tabs and MRP chainguide. I want to swap this chainguide with the one on my 2016 specialized enduro. I thought this would be fine, both are non boost frames but the chainline appears off. Namely the guide from my enduro rubs on the inside surface of the norcos chainring. Not by a little, by a lot!

My assumption is that ISCG tabs/guides are a universal fit and not boost/non boost or bottom bracket specific? I must be wrong?

Also whilst we're here, can I run a 12 speed mtb cassette on a regular 8,9,10 speed hyperglide freehuh body or does it need to be 12 speed specific? I'm wanting to do a 1x12 conversion on my partners bike but don't want to buy a new wheel or hub body.

Thanks for the advice, I must be getting old.

Cranksets can have different chainlines, that's probably where the difference is occuring as (like you say) that ISCG-05 tabs are generally standard (AFAIK).

From memory M8000-series Shimano had 48mm and 51mm chainlines available (@The Duckmeister?), which is definitely enough to cause a hearty rub. Some chainguides (ie: OneUp, not sure about the MRP), have removable/stackable 1mm shims to adjust the guide to the chainring. Maybe see if there's something can be removed to prevent the rubbing.

Most non-boost frames would've had the narrower chainline, but some manufacturers did different stuff here and there. Sometimes they'd use a boost crankset/chainline but then offset the (non-boost/142x12) rear hub 3mm toward the driveside to keep the chainline from crankset to cassette more aligned, but create a few millimeters more tire clearance.

What's the aim for the 12sp conversion? Unless they're specifically asking for tighter gear spacing (generally only desirable for flatter/mellower trails) or massive gear range, it may not be worth the expense/bother. 12sp can be great, but is farkin' expensive for what it is - unless buying the cheap stuff, which is then typically either fragile or exceedingly heavy. Just IMO.

 

[cameron_15]

I'm aiming for an 11-50 cassette of which there's a few options. Just wanted to make sure it's not like road freehubs where there are different widths for 11 speed.

The chainguide has me more perplexed.

The norco bike has BB92 with sram gxp cranks
Specialized has BB30 with sram BB30 cranks

 

[The Duckmeister]

There are a few ISCG mount variants; it may be the case that the Spesh frame and its chainguide are not the 05 version, hence the inabilty to swap the guides across frames.

As for the 12-sp. stuff, there are a few cassettes that will fit on a HG hub, but many that won't. If it has an 11T top gear it will fit; anything smaller will not.

 

[beeb]

I'm aiming for an 11-50 cassette of which there's a few options. Just wanted to make sure it's not like road freehubs where there are different widths for 11 speed.

The chainguide has me more perplexed.

The norco bike has BB92 with sram gxp cranks
Specialized has BB30 with sram BB30 cranks

I have no idea about SRAM cranks sorry, I'm out!

 

[The Duckmeister]

I'm aiming for an 11-50 cassette of which there's a few options. Just wanted to make sure it's not like road freehubs where there are different widths for 11 speed.

The reason for road 11-sp. having a longer freewheel body than standard HG is because the comparitively small big sprockets wouldn't have sufficient clearance from the spokes if fitted on a normal HG. The much bigger sprockets of MTB cassettes easily clear the spokes, so the cassette cores can be made to fit on a standard HG. 8/9/10/compatible 11/12-sp. cassettes can fit a road-11 hub with a 1.8mm spacer behind the cassette.

 

[cameron_15]

Just measured the 2 guides then. The specialized guides backplate is about 2mm wider than the MRP guide, just enough to cause the fouling.

Not sure what to make of it. The chainring on my specialized sits bang in the middle of the guide yet on the norco it's clearly well off centre.

The chainline of both bikes look good too.

Probably not worth losing to much sleep over though...

 

[BurnieM]

My MRP AMG chainguide/bash guard came with spacer washers.

I ended up using different spacers at the bottom than the top mounts.
A bit of trial and error removing cranks etc more than once.