I want to triple a bike for my wife. I have noticed that some road bikes use mountain components, and I wonder why.

As an example, my wife's current bike, a 91 Sirrus has Deore DX cranks and derailleurs. I have seen bikes from the same late 80's early 90's era use 105 and RSX triple components.

I am curious as to why one would pick one or the other--- can you tell me why? Are there functional differences? And are they generally cross compatible? Can you use a mountain cranks with road derailleurs?

Actually, I know there is at least one difference. The mountain cranks use 110 bcd chainrings. The road cranks use 130 bcd. I guess that could make a difference as to which chainrings are available.

For my wife's new bike I have the option of using the Deore DX from her old bike. That was the original plan when I thought I was going to be buying a bare frame. But I may not want to dismantle that bike now, as I may only need cranks and derailleurs to make this new bike a triple.

So If I want to go in search of triple cranks and derailleurs, should I look for road or mountain?

Jared

You'd probably be better off asking this in the Mechanics forum... not that mechanical ability is lacking here.

There's no real functional difference between "road" and "mountain" cranksets. The only real issue might come when you need to choose a front derailleur. The choice will depend on which crank, which shift levers, and what frame they're going on.

The 105 and RX100 groups didn't get triple cranks until 1992. Before that, the only way to set up a low-geared touring bike like the Sirrus was to use "mountain" parts.

If you're converting, the experience, and the trial and error, of others is the way to save time and money.

I've seen some nice touring bikes with mtb components mixed with road stuff. I've also seen some nice old triple touring bikes make great donor bikes. My mixte build, I hope, will be set up that way, with a triple group from a donor bike.

I've found a couple of problems when converting. One, the FD's are not all that common in 28.6 clamp-on size, or braze-on for that matter. You kind of have to keep on your toes to get one. Two, the FD may/may not work with the crankset. Some FD's, the RSX triple, for example, can cover a 48-26 difference, but cannot cover a 52-30 difference. The increased radius of the larger chainrings (130BCD) over the smaller chainrings (110BCD) can be too great for the FD cage to accommodate.

So, get an FD that fits the tube, and one that works with your choice of crankset. After that, a triple L shifter is a triple, and a long cage RD is a long cage, more sensitive to the cassette than the chain rings.

+1
and the RD choice is really a what type of freewheel/cassette you want to run. Most Road long cage RDs can handle up to 27 teeth cogs. If you want bigger, you have to go MTB.

I sell cranks and crank related tools for a living and the answer is simple.

Fast strong riders want the large chainrings of a road crank and mere humans need the small rings of a mountain bike crank. Road triple derailleurs will work sorta OK on MTB rings but not the other way around. I've sold about 150 shortened Octalink 105 and Ultegra road triples and about 1/3 have had me upgrade the rings to 24-39-48.

Modern road triples have recently gone from 30-42-52 to 30-39-52. Some of the newer triple road derailleurs won't even work with less than 12t difference between middle and large ring. Modern MTB cranks are almost all 22-32-44 - 4 bolt on 64/104mm BCDs.

The ideal touring setup for most people seems to be 24-36-46 but YMMV. Hardly anyone sells a nice 74/110 road triple anymore. Sugino sells the XD-600 with 26-36-46. The customer requested replacing the 26 with a 24 on almost every one I've ever sold.

Older 74/110 MTB triples are an excellent choice for a road bike for the average rider. With 11 or 12 small cogs very few of us need larger than 46t. I still use Suntour freewheels with 14t small cogs and 46t or even 42t is plenty for me.

I've just done two triple conversions using otherwise similar Sakae cranksets of 110 and 130 BCD. I fouind no appreciable technical difference between the two conversions or in the availability of chainrings for the different BCDs, which in my case happen to include 46T, 48T, and 52T (notwithstanding my penchant for insisting on stylistically compatible chainrings on a given crankset). YMMV.

blastphemy here, but i just finished this CF triple with a 34 tooth sram cassette and xt derailuer, shifted with Ultegra. Makes local hills a bit more fun for this clyde.

+1

I've rebuilt several older road bikes with complete drivetrain grafts from old donor rigib mtb's. Works great, and it is an easy, straightforward job to do.

Uhh... MTB triples also are a bit wider in "Q" factor than old road triples.

Isn't there also a top pull vs bottom pull distinction with FD's? Most MTB FD's are top pull, while road bikes are set up for bottom pull.

This is all real good information. I did not realize that there were limits as to total ring difference and a maximum difference for the intermediate and large rings. It sounds like you need to decide what gearing you want first, and go from there.

And on a related note, are the early 90's 105 triple components relatively rare? I did some searching and I am not finding much of anything. I can find lots of octalink triple cranksets, but not many square spindle triple cranksets. And the ones I have found are not 170mm.

Jared

I love these threads. I have 3 road bikes converted to triples. 2 are mtb drive trains and 1 has a road triple and a mtb cassette. I personally prefer the mtb setup even though they are 6 and 7 speed. The road triple is a 52/42/30 with a 12/30 9 speed. When riding the triple I never use the 52 ring and never run out of gear except on steep down hills which is fine with me since I am no racer. I mostly use the middle ring on the mtb triples but when I run out of top gear I do switch to the big ring which is a 48 on one and a 44 on the other bike. I do enjoy the really low gears on the steep hills around here and I do use the granny on most every ride locally. If I still lived in a flat area I would be riding a double with something like a 34/46 crank and a 13/24 5 speed, 13/28 6 speed, and a 12/30 9 speed. I used to ride a 34/42 .....14/24 5 speed on the flat lands. I had an honest 10 speeds and it worked out great for me as a recreational rider. One of the mtb fd is mounted to a bracked that is mounted behind the fixed cup of the bb. This is not a high end drive train but it has worked fine for me and would do the same conversion again. If you make the triple conversion for your wife I think she will "Thank" you for it I would suggest the mtb conversion. Good luck! PM me if you would like more detail.

This was my 1st triple attempt. Converting a Trek 613 with parts form Ebay. Sugino triple crank, added 2 Sinz 48T and 38T, and a Salsa 28T. With help from this forum I installed the 122mm cup & cone BB. Went surprisingly smooth for my first attempt. Installed a new Sram PC-850 chain and a nice old Suntour V-gt Luxe. The rear cluster is a Shimano HG-22 14-28. Road the entire last Summer without a problem or adjustment.
My new project, this Spring, will be to triple a nice old Lotus Classique. This time I will go 46,36,26 with a new Hyperglide and a Suntour Cyclone.

+10 I rarely/never need a 52 tooth crank ring either. So MTB cranksets are more useful to me.

Sort of. A lot of that wider Q has to do with using 135mm spaced rear hubs compared to 12X-130mm road spacing. A lot of MTN triples moved onto a road bike can often use a shorter BB spindle to reduce the Q factor.

+1

Most times, it is simply a matter of removing the road double and installing the mtb triple, without having to change the BB. Straight swap.

Sometimes a big ring is pretty nice to have up front. Here are my 2 triples:

In this one, the freewheel is 14-28, so I really need that 52 on the 52/42/32 (ST oval tech crank and Deore RD)



This one, has an 11-28, so I can live with 46/36/26 (full M500 -Exage 500LX- components)



(of course, the 2 bikes serve different purposes, but I've got to keep going on the flats and down hills in both...)

Good heavens. I hope you really need a triple.

That's kind of like putting a tractor engine in a Porsche.
It's bizarre.
It's odd.
I like it.

That thing has got to climb like a nimble goat. It would be perfect for the Assault on Mt Mitchell.

My first conversion, a 1987 Centurion Lemans RS, from 2x7 Light Action to 3x7 RSX, 48/36/26 in front, Sante 12-28 in the rear. The owner is planning on touring it and doing Bike Virginia with it.


My second conversion, sorry for the bad photo, is a Sora 3x8 group with Bontrger Race crankset (Sorry E, it's all I had). It was my commuter bike, and is going back to double because a fellow BF guy needed that L triple shifter worse than I, and I think that frame was thinking of throwing me in a curve. Of course, now that I've seen a triple Kestrel, I don't feel so bad. 53/42/30 front, and 12-23 rear, I think.


If I do another one, it'll be a 9-sp 105 group, or Ultegra if I can find the parts. It won't be an Ironman. I think it really messed up my mojo for a while.

Yeah, the early 105 and RX100 triple cranks and triple-capable derailleurs are pretty rare. I took a while for "low-geared" road bikes to take hold in the marketplace... or maybe we all got old and slow. I forget.

I have a bike with an early 105 triple rear, 180mm XT cranks with larger chainrings, and bar-end shifters:
https://home.comcast.net/~jeff_wills/fort/index.htm
It's pretty neat, but I hardly ride it. Too many bikes!

How strong of a rider is she, what is the rest of the bike?

Compacts are pretty common on touring bikes. my 95 t700 came with 44-34-22 wasn't horrible but on the flat unloaded I'm on the 44 often. The 98 came with 42-32-22. I found my self spinning out often and jumping up and down between the 42 and32 a LOT. Heavy load I might like it but I really hate it commuting.

Found a set of 48-36-26 and really liked them. The 36 with a 12-28 cassette is a nice gear selection.

I recently came up with a brand new Octalink 30-39-50. Loving the 50 for the long down hill I have but 39 is a little higher for general use then I like. I would love to find a 50 36 26.

This thread is really interesting, especially in the chain ring sizes. For years, I thought 52 or 53 ruled the world, period, except for mtb's, but have seen some real smooth riders lately, running casually high rpm's. Now I know why.

It is nice to see that I am not the only rider using smaller chain rings. I started using small chain rings when I was in my middle 30's which was before the mtb craze and they were not as E Z to find back then. My 1st small ring bike conversion concerned me. I hate to spend money uselessly but I never looked back after the conversion and I still have the bike. I have since changed it to mtb triple for the granny.