XT FC-M730 on a Retro Tourer - someone must have done it here!

[Woz]

OK, ok, ok, I know it's not about Classic Road and Italian racers, but it's worth a shot.

Someone here must have done it. Using an old MTB XT FC-M730 chainset on a touring / randonneur / CX / Retro-mod Gravel / whatever
to take advantage of the smaller 110 BCD compared to the ubiquitous 130 BCD road chainsets with silly big gearing at the time.

My big question is, what BB length would we be talking to get a reasonable 45mm (or so) road type of chain-line?

I know they are old straight un-profiled cranks and were supposed to be mated to a whopping 122.5mm BB at the time.

These cranks seem useful again, since there are loads of 110 BCD rings out there.....round ones too, and not Biopace !

[Please don't tell me I need to join the CTC and go through a 30 year archive to find the reply ;-) ]

 

[Takingabreak]

118mm. That's my guess. Along the lines of, well 130 rear spacing means the chainline needs to be moved in a bit from 135 spacing so lets plump for a common size square taper bb that will achive that.

If it's a little out, it doesn't matter because most of the gears are out of line. As long as there is clearance for the arms and inner ring on the chainstay all is good.

 

[pigman]

I'm a bit confused by this thread. You seem to suggest that the only road chainsets are the 130bcd ones. Thats not true. Compacts have been with us for 10 years or so and are 110 bcd. So, you can gear down and being lighter than mtb chainsets and having a smaller Q factor are more suited to road riding

 

[Deleted member 69416]

I put an MT60 on a Galaxy with a 118 . Please forgive if this is irrelevant , they appear very similar .

 

[Woz]

Squirrelchaser, very relevant ! I think the DX and XT crank were indeed very similar, and I also have the MT60 on the short list too !

If you get chance, would it be possible for you to measure the Q factor of your set-up?

 

[Woz]

I'm a bit confused by this thread. You seem to suggest that the only road chainsets are the 130bcd ones. Thats not true. Compacts have been with us for 10 years or so and are 110 bcd. So, you can gear down and being lighter than mtb chainsets and having a smaller Q factor are more suited to road riding

Oh I'm good at confusing things.

Compact, silver, JIS square taper road chainsets are in fact not common. Pretty much limited to Sugino or the FSA Vero as
far as my research as taken me. Going back in time to early MTB cranks ticks a lot of the boxes with more availability in
the crank length I want. There is no way I'm going down the more modern route of Octalink and External BBs etc.

The only think I don't know, is the what kind of chain-line and Q-factor I can achieve. I will be using it as compact double
with a very wide ration cassette. Would like the rings fairly inboard since the small ring will only be an occassional panic button.

As a side note, I've come across an interesting Shimano CX400 chainset that was road orientated with a very interesting BCD pattern.

 

[foz]

if you're not going to install the inner ring then you can probably go shorter than 118mm BB. You should go as short as possible because if you plan on riding most of the time on the large ring then you ned that one as central as possible with respect to the cassette

 

[Deleted member 69416]

if you're not going to install the inner ring then you can probably go shorter than 118mm BB. You should go as short as possible because if you plan on riding most of the time on the large ring then you ned that one as central as possible with respect to the cassette

I think you can get away with a 114mm if you run the outer two . I sold the Dawes Woz , sorry.

 

[Woz]

if you're not going to install the inner ring then you can probably go shorter than 118mm BB. You should go as short as possible because if you plan on riding most of the time on the large ring then you ned that one as central as possible with respect to the cassette

Exactly, that is my thinking too. The outer ring will only be about a 44T or 46T so I should have some margin to go inboard without
hitting the chain stay.

 

[Woz]

Thanks eveyone. I'll make an attempt with a 113mm or 115mm and see how it goes.