Chainline with a MTB Hollowtech2 chainset.

GuyBoden

Veteran
Location
Warrington
I'm thinking of putting a MTB Deore triple Chainset and Derailleur on my roadbike, currently the bike has a square taper chainset.

The MTB Deore triple Chainset has hollowtech2, which I know very little about.

The axle length seems to be fixed, so, how do you get the correct chainline?

Is it just a case of adding/subtracting washers on either side of the axle?
 

ianrauk

Tattooed Beat Messiah
The chainset should come with a spacer for the non drive side.
 

Cycleops

Legendary Member
Location
Accra, Ghana
I’ve got two bikes with Hollowtech triples, one a MTB and the other a gravel bike which I converted from ST. You get three spacers with the chainset. I put two on the drive side and the other on the opposite. The MTB came the same way. They are so narrow they’re not going to make any difference to the chainline, I think they are there to ensure the cranks are the correct distance apart and to accommodate different shell widths.
The bearings are outboard of the BB shell so that in itself will have more effect on the line but it doesn’t seem to make much difference In operation.
593419
 
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Ajax Bay

Guru
Location
East Devon
Are the BB shell widths the same? I'd expect the road bike to have a 68mm wide BB shell. Whereas the H2 MTB spindle will be designed for a 73mm wide MTB BB shell. Forgive if wrong. 5mm seems a lot of washers, to me.
 

si_c

Guru
Location
Wirral
Hollowtech is a nice system to work with but the bearings don't last quite as long as a sealed square taper unit though unfortunately. As mentioned above the spindle width for Road and MTB are slightly different - 68mm for Road and 73mm for MTB, if you buy an MTB bottom bracket rather than the road it should be sized 68/73mm and come with the spacers needed - for a 68mm shell you need all three, for a 73mm shell, just the one.

Edit to add: If you get a road BB then it'll be sized to 68mm and won't come with spacers, I know it's probably obvious, but worth mentioning. You'd then be left to try shimming the outside of the bottom bracket rather then the spacers which sit inboard of the bearings on the MTB, so I wouldn't recommend it.
 
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si_c

Guru
Location
Wirral
Are the BB shell widths the same? I'd expect the road bike to have a 68mm wide BB shell. Whereas the H2 MTB spindle will be designed for a 73mm wide MTB BB shell. Forgive if wrong. 5mm seems a lot of washers, to me.
For an MTB it's 7.5mm of spacers as there is always one on the drive side so you have a spacer left where you can mount chain catchers on 1x drivetrains if you don't have a braze on. You just fit 2 on the driveside and 1 on the other when fitting to a 68mm shell.
 

Ajax Bay

Guru
Location
East Devon
Why, Guy? Derailleur change: fine.
 
I tried fitting an MTB HT11 triple to a roadbike frame when building a bike for my son. Despite putting loads of spacers on the NDS (less than ideal for BB shell thread engagement) I still couldn't get the chain line to allow the front mech to shift onto the big chainring.
In the end I bit the bullet and bought a bargain road triple with square taper BB from Spa Cycles and it runs like a dream. Square taper is far superior system anyway so don't be tempted to 'upgrade' to HT11.
 
Location
London
I tried fitting an MTB HT11 triple to a roadbike frame when building a bike for my son. Despite putting loads of spacers on the NDS (less than ideal for BB shell thread engagement) I still couldn't get the chain line to allow the front mech to shift onto the big chainring.
In the end I bit the bullet and bought a bargain road triple with square taper BB from Spa Cycles and it runs like a dream. Square taper is far superior system anyway so don't be tempted to 'upgrade' to HT11.
yep - i bought a bike with HTII by mistake not really considering the BB.
A fair chance I may "downgrade" it to square taper in the near future - picked up a nice secondhand deore ST chainset so it's just sat there waiting to be swapped - chainrings can just be transferred I think.
One of my ridgeback hybrid conversions got a Spa road ST chainset - a problem with getting the chain to drop onto the small ring was sorted by just using a ST BB with a 2mm longer spindle - problem solved for evermore. Simples.
 

si_c

Guru
Location
Wirral
I agree my Hollowtech setup is 10 years old, 112,000 miles original BB etc Rubbish durability.
Fair enough, I've found the left bearings tend to go after about 4k miles, the right hand invariably outlasts it. Anecdotal I know, but I've heard other people say similar that the bearings don't last as long as a fully sealed unit. I'd expect a BB-UN55 to last well beyond 10k miles.
 

ColinJ

Puzzle game developer
One of my ridgeback hybrid conversions got a Spa road ST chainset - a problem with getting the chain to drop onto the small ring was sorted by just using a ST BB with a 2mm longer spindle - problem solved for evermore. Simples.
I put a triple chainset from Spa on my CAAD5 and I have a similar problem. Next time I buy a BB for it I will buy one with a slightly longer spindle. For now, the work-around is to change to the smallest chainring before venturing up onto the biggest few sprockets. (The extra lateral bend in the chain helps the front derailleur peel the chain off the ring.)
 
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