theow

Hi, I want to make a cheap gravel bike, and I have found a mountain bike frame, but with thicker road wheels, which features a 21 speed Shimano gearing system, and twist shifters. I already have an old road bike which also features a 21 speed Shimano gearing system, albeit with brifters. My thinking is take the drop bars and brifters from my road bike, and put them on the other frame, because they run on the same brand gearing system, and have the same number of gears. Are there any major compatibility issues between the two, or would it be compatible?

delbiker1 

I believe the road brifters have a different cable pull and will not operate the mountain bike brakes properly. I think the road has short pull for brakes and the mountain has long pull.

70sSanO

If your mtb has linear/v brakes, the brakes are not compatible, as noted above.

There is also a compatibility issue with the mtb FD and the left (front) STI shifter.

John

Edit added: Your work around for the brakes is a travel agent. You “might” be able to run a road FD on the mtb, but chainring diameter (teeth) and chainline might be an issue.

theow

the brakes on the mtb are cantilever, im guessing they'd be okay? Is there a way around the compatibility issue?

shelbyfv

Your 7 speed brifters will operate your 7 speed mtb RD and will work with your canti brakes. They may or may not work satisfactorily with your mtb FD. If they don't, a bar end or downtube friction shifter might be an option. I would suggest you try riding your "gravel" with the mtb as is. Pursue the drop bar conversion only if your rides become long enough that the flat bar/single hand position becomes a problem.

Ironfish653

Old or low-end Shimano 3x7? 'Ought to work' I've found 7-speed is pretty much the last bastion of mix-n-match, especially early 90's stuff.
Not always, but often enough to make it worth the try.

I'm always wary of taking apart a complete, operating bike to get some of the parts for another bike. (unless you got it specifically for a parts donor) Especially if you don't really know what youre doing. The OP may end up with a satisfactory drop-bar MTB, and a flat-bar road bike, or he could end up with a cobbled-up 'gravel grinder' that doesn't quite work, and a pile of parts that won't quite make a complete bike.

dedhed

shimano mountain/road front derailleur issue see #7

Shiftmate Compatibility Charts and Choices - Jtek Engineering

theow

Low end unfortunately.
I would be inclined to agree, however the road bike would need a lot of improvements to be regarded as fully operating. My thinking is that I can either spend the money fixing up the road bike that im not particularly attached too, or try and build something im more interested in! (the price of fixing it up would be roughly the same as attempting the gravel build)

At the end of the day, im just excited at the prospect of doing it myself, no matter the outcome, and either way, ill have learnt something! To me personally, the build is worth a try, and if it goes well that'll be fantastic, and if it doesn't, thats on me, but this thread and your comment have been really helpful, thank you!

grinningfool

Check out RJ The Bike Guy on YouTube. He has tons of videos on how to do the kinds of things you’re asking about. Lots of good instruction there.

nick_a

I say give it a whirl! You'll know pretty quickly what works and what doesn't. You may need to find a short-ish stem since the reach of those drop bars could make you stretch way out compared to the mtb bars you've got on there.

SpedFast

I think it sounds like a fun project. Good luck,

dedhed

https://www.bikeforums.net/classic-v...nversions.html

Ironfish653

theow Sounds like you've got a "six of one, half-dozen of the other" situation, so nothing much to loose for trying. Best of luck with your build!

Viich

I swapped to drop bars for my winter bike - used an early 90's bike with cantilever brakes, drop bar, bar end shifters. 7 speed stuff is mostly compatible - you might have to swap front derailleurs (but you might not)

Bar end shifters are a good way to do this, friction front shifting almost always works. If you really want integrated, I'd go with something like this from Amazon over taking apart your road bike. Drop bars can be had cheap too.

cyccommute 

Yes, integrated road shifters have the pull for cantilever brakes.

The only real incompatibility is the front derailer. Mountain and road front derailers have close enough pull ratio that they almost work but not really. A front derailer will work but you may need to move the crank inboard to get enough reach.

SpedFast

Does anyone know if those Micronew 2X7 brifters will work on a 6spd freewheel upgrade? Current vintage road bike with indexed/friction stem shifters.

70sSanO

No, but the RD will work with a 7 speed freewheel, shouldn’t be a dropout width issue, if the RD is SIS.

The FD is unknown compatibility. If it is friction now, it might not work. There are work arounds with cable tension to get it to work. Basically with a 2x, if the shifter can pull enough cable it can be made to work.

John

Viich

There's a trick cable routing you can use with Shimano that will get you there. SheldonBrown.com

SpedFast

So if I replace the 6spd freewheel with a 7spd freewheel I should be able to make the brifter work? I have a Shimano freewhl and SIS derailleur on the back now. Not worried about the front derailleur,, Thanks

icemilkcoffee 

Yes the brifter will work with the 7 sp freewheel.
But you should be worried about the FD though. You need to replace the FD with a STI compatible road FD.

SpedFast

It took a bit but I found that article you mentioned, Good info there.

SpedFast

I have one of those in my parts/junk bin salvaged from a MTB. I did have a 7 spd freewheel too but I gave it to a neighbor because I didn't see the point in keeping it at the time since my 6spd and the 7spd were both 14/28 gearing. Now I have several 6 spd freewheels in my bin but no 7spd haha.
Thanks for the info

Edit=I just found a hub and freehub with an 8spd cassette on it. I'll have to clean it up and see how it looks. Maybe I can upgrade to 8 gears in the rear.

Leisesturm

Interoperability arguably began with 7sp. 6sp is still its own spacing in some cases. The 7sp may fit, it may not. A new rear hub may be necessary. What exactly is the rear OLD (locknut to locknut) spacing? If 135mm you are good to go with just about anything with that frame. If less you may have the ... annoyance of having to spread the dropouts* each time the wheel is inserted, or cold setting the frame so the frame submits to the upgrade. Swapping between MTB and Road is made deliberately hard to discourage exactly what the o.p. wants to do, and you as well. The reason is $$$. You are either going to pay in cash or in sweat. Pick your poison.
*maximum 2mm per side adjustability.

SpedFast

Thanks for that information. I'm going to clean up the 8spd setup in the parts bin and see about building a wheel around it if, and that's a big if, the hub will fit properly in the frame. I don't have a problem cold setting it wider, but not much. At this point the bike is still rideable so there is no push to make it happen. I might just opt to buy another 'used' bike with the brifters already set up on it and donate the old bike. (Wife only lets me have 2 at a time).

Leisesturm

Just to be clear, you can cold set wider than 2mm each side (~5mm total), but doing it by hand each time would get OLD (nyuk) really quickly for more than a very few mm total. Re: your domestic situation. Insist on the right to have (not that you will) 1/2 as many bikes as she has pairs of shoes. Problem solved. In the unlikely event that that fails ... there is Tinder.