Hi, is there an available set of chainring wherein the biggest is 52t or 50t?
if not, is it possible to combine the road bike big chainring to 2 mtb smaller chainring?
i would like to use my mtb on roads. and it seems that the 40t is not enough for the speed.

thanks in advance

What are your desired chainrings sizes for all three rings?

Here is a "Road Triple", 30/39/50. But, you could use larger rings.

Shimano 105 5703 Triple 10sp Chainset | Chain Reaction Cycles

Here is a Vuelta Corsa, 30/42/52
https://www.vueltausa.com/components...170-175mm.html

A 110BCD crankset can support a 34 Low, and 52T or larger rings with a 2-ring configuration, or sometimes you can mount a triple on them.

hey thanks! i didn't know road has triple chainring.

Some of the latest groupsets are eliminating it. But, older groupsets still support the triples. They have been popular for certain riders (women, & heavier riders).

The Q-Factor offset may vary between MTB and road groupsets. Make sure what you choose does fit your frame.

Are you using a 11T cassette? That is one easy place to increase gearing a little bit.

Most mountain bikes will not clear a 30t on the granny -smallest chain ring. Some frames will also have problems clearing a 50t ring.

I'd look at something like the Shimano Touring cranks -48/36/26- rather than road cranks.

And for what is worth, once I learned to spin I never found my mountain bike that undergeared on the road. A 40x11 pedaling at 100rpm gives you 28-31mph depending on wheel size. Not many people will sustain that speed even on a road bike.

What? Slightly older mountain triples were 64/104 bcd. Standard 3x9 drivetrain. 22-26, 32-36 and 42-48. Most were like 22, 34, 44.

22-32-42 was the most common, actually. And that's why most mountain bikes will not clear a 30t granny like the one someone was recommending. You may be able to make that 30/39/50 road triple work by using a longer-than-you-should bottom bracket spindle, at the expense of chain line.

On road bikes I have been using 52-42-28s and 26s for decades. Sugino square taper 130-74 bcd cranksets. It is inconceivable to me that the BB of sufficient length to clear the chainstay isn't available.

Yes, if you have to push the crank out to clear the chainstay with the cogs, your chainlne will suffer. I'd say, build it up with the "proper" axle. If it hits, go just longer enough that it clears.

Ben

What is the frame material?

If it is steel, one could easily press in a few crimps to clear the large and small rings. Also clearing the pedal ends of the cranks.

It shouldn't structurally damage the frame very much.

already have a functioning crank?, buy larger chainrings

my touring bike (13-34t freewheel) runs a 24,40,50 triple, an older frame ,

to clear FD lower tip with an over the BB cable run to the RD, its 52,42,26..

Would be helpful for the conversation to tell us what chainrings you have now and the bcd of the crank.

Hi. i'm not familiar with the BCD. but currently, my crankset is an Alivio with a 22-30-40t.

bolt circle diameter.. Sheldon Brown's Bicycle Crank/Chainring Bolt Circle Diameter Crib Sheet

Yep.

Sounds like it could be a Alivio FC-M4050 with a 96/64 BCD

The Alivio FC-M4060 has 26-36-48 tooth chainrings and a 104/64 BCD

Bigger chainrings means a new front derailleur.

50 or 52 tooth road chainrings means you'd need a road front derailleur

Road front derailleurs don't work well with mountain shifters

With a 26-36-48 mountain/trekking crankset you would need a new front derailleur but you could keep your shifters

With a road crankset that has 50 or 52 road chainrings, you would need a road front derailleur and a shifter for a road front derailleur.

Shimano specifications: https://productinfo.shimano.com/#/spec/2.3