# Mountain bike crankset on road bike?



## Pierre (Jan 29, 2004)

Hi folks - so most of my riding is in steep mountains (the Alps in Europe), with frequent 8-12% bits. Currently using Dura-Ace Triple 7803 10-spd, with a 30-39-53 crankset, STI shifters and XTR rear with 11-32. I am annoyed that I bottom out frequently on the 30-32 combo, but don't even remember when was the last time I used the 53 big crankset ring. Very annoyed. So I would like to install a mtb crankset (e.g. the Deore XT FC-T781 26-36-48). But I just went to my LBS, a reputable place where I've come to trust the guys to know what they talk about. And the guy told me it wouldn't work with STI shifters. The crankset wouldn't work with my current 7803 front derailleur, and the STI shifters wouldn't work if I switched the front der to a mtb derailleur.

Any input into this? Do you know any solution to be able to use a lower than 30t front ring? I do not want to go to friction shifters or mtb shifters, I would like to keep STI...


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## bikerjulio (Jan 19, 2010)

If you never use the big ring then why not buy a Deore double? I fitted a Deore 40-28 on to my CX bike for trail riding. You could try a 40-26 or lower. It requires a Deore FD and I see no reason why it would not work with your shifters.


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## harryman (Nov 14, 2014)

I've ridden in the alps and Dolomites with a compact front, 50/34 with either a 11-34 or 11-36 in the back, you have to get a grade in the high teens before you might need to stand. Mtb cassettes and rear der.


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## Red90 (Apr 2, 2013)

I had done a bit of research on this for my cross bike for shimano groups. I ended up using SRAM. However if I was to use shimano, you can use a 9sp mountain bike deraileur on your 10sp STI shifters. This will allow you to go to a 36t at the back. As for the front, I still used a double, but was able to use a 42/28 mtb crank at the front with no issues. What you may need to play around with in the front is the chainline of the mtb crank as it's slightly different than the road bike. I had placed the spacers to one side to minimize any issues with the chainline.

I haven't done any research on triple cranksets so I can't help you there. My setup is limited in the top speed region, but I can still pedal to 40km/hr + which is more than I need anyways.


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## Pierre (Jan 29, 2004)

Thanks - when you use a 42 / 28 crankset, what front derailleur do you use? Road double, Road compact, Mtb double?

I know about the 9spd mtb rear der with 10s shifters, this is what I'm doing now with an XTR 9-spd rear der and 10-spd 11-32 cassette. I could change to a 11-36 cassette, but I thought it would make sense to investigate the crankset situation as I use the 30t ring all the time and almost never the 53t large one.


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## Pierre (Jan 29, 2004)

Thanks, this is in line with what Red90 suggested below - are you running this with STI shifters? The reason why this would not work is just if the cable pull required by the FD is too different from the cable pull provided by the shifters. If you're using friction or index shifters this is not an issue, but with STI shifters it is important.


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## sasquatch16 (Feb 7, 2013)

Older 105 and below triples you can put smaller than a 30 tooth inner chain ring. I have seen guys here talk about going as low as 26t. I think it is 5700 .


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## wgscott (Jul 14, 2013)

As an alternative to this, it might be worth considering a 46/30T crankset. Compared with a 50/34T, you only lose the topmost gear (50/11), since 46/11 = 50/12 .

I've started a thread here in case anyone is interested in that option: http://forums.roadbikereview.com/co...compact-cranks-46-30t-thereabouts-355739.html


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## geekjimmy (Mar 26, 2012)

Red90 said:


> I had done a bit of research on this for my cross bike for shimano groups. I ended up using SRAM. However if I was to use shimano, you can use a 9sp mountain bike deraileur on your 10sp STI shifters. This will allow you to go to a 36t at the back. As for the front, I still used a double, but was able to use a 42/28 mtb crank at the front with no issues. What you may need to play around with in the front is the chainline of the mtb crank as it's slightly different than the road bike. I had placed the spacers to one side to minimize any issues with the chainline.
> 
> I haven't done any research on triple cranksets so I can't help you there. My setup is limited in the top speed region, but I can still pedal to 40km/hr + which is more than I need anyways.


I did pretty much the same thing. I use a SRAM XX 156Q 42/28 on my gravel bike. Right side is Ultegra 11-speed shifter & rear derailleur. Left side is an Ultegra shifter connected to a 10-speed Force front derailleur. I didn't install it, but the LBS said the Ultegra front derailleur didn't move for enough to prevent rub on all 22 positions. 

I don't miss the bigger front ring at all, and the 28 is good for getting my tubby ass up and down until I'm less tubby. 

Sent from my LG-H810 using Tapatalk


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## bikerjulio (Jan 19, 2010)

Pierre said:


> Thanks - when you use a 42 / 28 crankset, what front derailleur do you use? Road double, Road compact, Mtb double?
> 
> I know about the 9spd mtb rear der with 10s shifters, this is what I'm doing now with an XTR 9-spd rear der and 10-spd 11-32 cassette. I could change to a 11-36 cassette, but I thought it would make sense to investigate the crankset situation as I use the 30t ring all the time and almost never the 53t large one.


Bikes will vary a little, but on my 40/28 conversion, a road FD would not work because the tail fouled the chainstay well before it was down to the correct height. Deore FD worked fine with the road shifter.


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## Lombard (May 8, 2014)

Pierre said:


> Hi folks - so most of my riding is in steep mountains (the Alps in Europe), with frequent 8-12% bits. Currently using Dura-Ace Triple 7803 10-spd, with a 30-39-53 crankset, STI shifters and XTR rear with 11-32. I am annoyed that I bottom out frequently on the 30-32 combo, but don't even remember when was the last time I used the 53 big crankset ring. Very annoyed. So I would like to install a mtb crankset (e.g. the Deore XT FC-T781 26-36-48). But I just went to my LBS, a reputable place where I've come to trust the guys to know what they talk about. And the guy told me it wouldn't work with STI shifters. The crankset wouldn't work with my current 7803 front derailleur, and the STI shifters wouldn't work if I switched the front der to a mtb derailleur.
> 
> Any input into this? Do you know any solution to be able to use a lower than 30t front ring? I do not want to go to friction shifters or mtb shifters, I would like to keep STI...


I don't see why the Deore XT FC-T781 26-36-48 crankset would not work with your STI shifters. Your shifters really do not care how many teeth are on each ring.

The main issue you will have is because your largest ring will now be smaller, your current front derailleur will need to be replaced. Think of your largest chainring's circle as an arc. The smaller the ring, the sharper the arc. The FD needs to match this or shifting will be sloppy at best.

BTW, the crankset you are looking into is a touring/hybrid crankset, not a mountain crankset which would be 22-34-44.

In order to get a front derailleur that will work with your setup of STI shifters and a touring crankset, you will need a previous generation (9-speed) front derailleur - specifically the Shimano Deore LX FD-M571. Google and Ebay are your friends.  This one is specifically designed for touring cranksets. A later generation FD will not work as the pull ratios will be different than your existing STI shifters.


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## Trekpilot52 (Aug 13, 2016)

Lombard said:


> I don't see why the Deore XT FC-T781 26-36-48 crankset would not work with your STI shifters. Your shifters really do not care how many teeth are on each ring.
> 
> The main issue you will have is because your largest ring will now be smaller, your current front derailleur will need to be replaced. Think of your largest chainring's circle as an arc. The smaller the ring, the sharper the arc. The FD needs to match this or shifting will be sloppy at best.
> 
> ...


I recently installed a non Shimano inner chainring with 26 teeth. Shifting still needs adjustment but should work out.


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