road triple chainline / mtb crank for road?

[nathan ramsey]

someone wants to put a mtb triple on their road bike...

typical road chainline is 43.5 - 45, modern outboard bb mtb triples
are all 50 i think. road dropouts are narrower too, which could
exacerbate a bad chainline.

anyone have any experience with this? i guess i'm going to have to
just go ahead and try it and see what happens.

[Hank]

On Jan 10, 9:44*am, nathan ramsey <nnmmr...@gmail.com> wrote:
> someone wants to put a mtb triple on their road bike...
>
> typical road chainline is 43.5 - 45, modern outboard bb mtb triples
> are all 50 i think. road dropouts are narrower too, which could
> exacerbate a bad chainline.
>
> anyone have any experience with this? i guess i'm going to have to
> just go ahead and try it and see what happens.

Shimanos can be set up with a 45mm chainline. They come with three
2.5mm spacers. Two are to allow you to adapt to a 73 mm shell, and the
third is to allow for an E-type FD bracket. Normal setup for a 68mm
shell and clamp-on FD is two spacers on the drive side and one on the
non-drive side. Move all three spacers to the NDS and you have a 45mm
chainline.

I guarantee the rider would not feel that much offset, but if they
freak, a pedal washer on the DS can compensate at the cost of a wider
Q-factor.

I imagine most others can be set up similarly, but haven't looked too
closely.

[treynolds@my-deja.com]

On Jan 10, 9:44*am, nathan ramsey <nnmmr...@gmail.com> wrote:
> someone wants to put a mtb triple on their road bike...
>
> typical road chainline is 43.5 - 45, modern outboard bb mtb triples
> are all 50 i think. road dropouts are narrower too, which could
> exacerbate a bad chainline.
>
> anyone have any experience with this? i guess i'm going to have to
> just go ahead and try it and see what happens.

I've had an LX crankset, bottom bracket, front and rear derailleurs on
a road bike since 1995. Actually, I've used those components on three
different road bikes since 1995. The chainline can be adjusted via
the usual techniques. Personally, I didn't bother. You're talking
about the 5 mm which is the center-to-center spacing on a 7 or 8 speed
cassette. I never had a problem dropping the chain and the chain
didn't wear out faster than on my other bikes (I have a lot).

If you use a MTB front derailleur and Shimano road indexed front
shifter, you may have a problem. Clamping the cable on the opposite
side of the fder clamp bolt worked for me but others have said it
didn't work for them.

Tom

[David L. Johnson]

nathan ramsey wrote:
> someone wants to put a mtb triple on their road bike...
>
> typical road chainline is 43.5 - 45, modern outboard bb mtb triples
> are all 50 i think. road dropouts are narrower too, which could
> exacerbate a bad chainline.
>
> anyone have any experience with this? i guess i'm going to have to
> just go ahead and try it and see what happens.

I did this for years, but with a crank that took a standard square taper
bottom bracket. I used a shorter-than recommended bottom bracket (107
instead of the listed 113 IIRC) and it worked fine. I usually used
this as a double, but did put the granny on for a loaded tour or two.

But with outboard bearings, you may be stuck with the bottom bracket
axlethat is attached to the crank, so you can't do this. You can try,
as suggested, to see whether it will work OK. It probably will, though
the chain reach for any of the big-big combinations will be quite bad.
Just avoid such combinations (big ring and the biggest 2 sprockets
should be enough), the gear ratios of which are duplicated on the middle
ring, anyway.

--

David L. Johnson

Let's not escape into mathematics. Let's stay with reality.
-- Michael Crichton

[Hank]

On Jan 10, 9:55*am, Hank <h...@wirtznet.net> wrote:
> On Jan 10, 9:44*am, nathan ramsey <nnmmr...@gmail.com> wrote:
>
> > someone wants to put a mtb triple on their road bike...
>
> > typical road chainline is 43.5 - 45, modern outboard bb mtb triples
> > are all 50 i think. road dropouts are narrower too, which could
> > exacerbate a bad chainline.
>
> > anyone have any experience with this? i guess i'm going to have to
> > just go ahead and try it and see what happens.
>
> Shimanos can be set up with a 45mm chainline. They come with three
> 2.5mm spacers. Two are to allow you to adapt to a 73 mm shell, and the
> third is to allow for an E-type FD bracket. Normal setup for a 68mm
> shell and clamp-on FD is two spacers on the drive side and one on the
> non-drive side. Move all three spacers to the NDS and you have a 45mm
> chainline.
>
> I guarantee the rider would not feel that much offset, but if they
> freak, a pedal washer on the DS can compensate at the cost of a wider
> Q-factor.
>
> I imagine most others can be set up similarly, but haven't looked too
> closely.

I should also add, be careful with your chainstay/chainring clearance
with this setup. If it does have clearance issues, go with the 47.5mm
chainline. If it needs wider than that, the frame should probably have
135mm dropouts anyway.