MTB crank on a road bike - 46/30t 46/28t anyone?

Discuss light weight issues concerning road bikes & parts.
alcatraz
Posts: 1356
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Hello weenies...

A friend is getting ready for the Taiwan KOM climb and is worried of burning out and having to walk the bike the 27% grades at the end as well as not finishing within the 7h time limit. He likes to spin and just dislikes being out of the saddle.

He's on a wilier running campy veloce 10s with a compact crank 50/34 and a 12-30t cassette. The derailleur is already the longest available thats compatible (medium) and looks to be at the limit on the 30t cog. Not much space to fit even a 32t which isn't available from campy (campy freehub).

To the point. I saw on youtube you can fit an mtb crank on there. The problem is the chainring size. Double chainring cranks are usually maxed at 42/28t and we would like a 46/28 or 46/30. Do you have an idea which common crank can be fitted with such rings and could work on a 10s road bike?

He has a clamp on front derailleur that can be lowered appropriately. I've been looking to get an mtb crank in an appropriate bcd and switch a chainring if needed. What do you think?

Thank you for reading!
/a

by Weenie


shimmeD
Posts: 454
Joined: Thu Jun 28, 2012 10:52 pm
Location: eNZed

by shimmeD

46/33 on compact 110bcd is definitely doable.
mtb cranks have higher Q-factor, no?
Less is more.

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silvalis
Posts: 486
Joined: Mon Sep 07, 2015 1:02 am
Location: Aus

by silvalis

Look at those new fsa and praxis sub-compacts.
46/30 and 48/32
Chasse patate

Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

If you really want to fit an MTB crank (higher Q factor but most ppl don't notice) you can get *all* ring sizes from Specialites TA.

xeonrs3000
Posts: 7
Joined: Tue Sep 08, 2015 7:30 pm

by xeonrs3000

I replaced a Shimano compact with a 46/30 FSA Omega (2017) on my wife's road bike. Only gotcha is that you have to replace the bottom bracket since the FSA has a 19mm spindle, which also implies that there are not a lot of bottom bracket options (only the ones from FSA themselves). They also have a pricier version (SL-K adventure).

Overall we're very happy with it. Much better solution than having to fit a cassette with large gaps between gears.

alcatraz
Posts: 1356
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

What do you think would happen if you get for example a 3 ring crank like 48/36/24t and take out the 36, put the 48 on it's place and swap out the little one for a 30t (64bcd).

An outer ring being used as a middle ring. How would that work?

/a

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silvalis
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Location: Aus

by silvalis

I think your chainring spacing will be way out.
Chasse patate

mattr
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Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

All the spotfaces on the chainring will be wrong, ring spacing *should* be ok. But chainline might be odd.

morganb
Posts: 621
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

Rotor announced a 46/30 chainring set that mounts to their cranks but I have only seen one set in the wild.

Marin
Posts: 3149
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

alcatraz wrote:What do you think would happen if you get for example a 3 ring crank like 48/36/24t and take out the 36, put the 48 on it's place and swap out the little one for a 30t (64bcd).

An outer ring being used as a middle ring. How would that work?

/a


I did this on my old CX, riding 26/40 and 30/40 with a FSA Gossamer triple and TA rings. Shifting was *excellent*.

Because of the positive experience, I just did the same for my wife's new (all-)road bike, she now has an FSA SL-K carbon triple crank with the 26/40 combo and an 11-32 in the back.

Image

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bikerjulio
Posts: 1901
Joined: Fri Dec 11, 2009 10:38 pm
Location: Welland, Ontario

by bikerjulio

I had a Campy 10-speed cross bike that was used on trails. Ended up with a Deore crankset and needed a Deore FD as well. The stock FD will foul the chainstay before being low enough. Everything worked fine.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

ooo
Posts: 650
Joined: Sat May 21, 2016 12:59 pm

by ooo

Marin wrote:
alcatraz wrote:What do you think would happen if you get for example a 3 ring crank like 48/36/24t and take out the 36, put the 48 on it's place and swap out the little one for a 30t (64bcd).

An outer ring being used as a middle ring. How would that work?

/a


I did this on my old CX, riding 26/40 and 30/40 with a FSA Gossamer triple and TA rings. Shifting was *excellent*.

Because of the positive experience, I just did the same for my wife's new (all-)road bike, she now has an FSA SL-K carbon triple crank with the 26/40 combo and an 11-32 in the back.



What was source for 40T chainring?
Was it chainring for big or middle position originally?
Last edited by ooo on Tue Jul 11, 2017 2:33 pm, edited 2 times in total.
'

Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

ooo wrote:What was source for 40T chainring?
Was it chainring for big or middle position originally?


Specialites TA. Middle ring.

jeanjacques
Posts: 134
Joined: Thu Apr 14, 2016 11:01 am
Location: France

by jeanjacques

On Rotor crankset, it's possible to change the spider for the MTB one, 110/74 (or 60, Rotor proprietary). You keep the road Q factor, have the possibility to have less than 30t on the inner.

morganb
Posts: 621
Joined: Wed Mar 15, 2017 5:30 pm

by morganb

jeanjacques wrote:On Rotor crankset, it's possible to change the spider for the MTB one, 110/74 (or 60, Rotor proprietary). You keep the road Q factor, have the possibility to have less than 30t on the inner.

Didn't realize they were interchangeable, good to know as I primarily run Rotor cranks due to them offering shorter lengths. On a similar vein TA Specialites cranks allow you to do the same, although they are square taper.

by Weenie


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