I’ ve come across these questions a lot: can I convert an MTB to a road bike? Is it possible to convert an MTB to a gravel, or a cyclocross bike?
No short answer to this; and this will be a long read about why should go ahead, or stop, or what are the disadvantages to this conversion? Which frames work best, which don’t; including a short primer on road bikes.
What is the purpose of a road bike?
This may sound as a stupid question, but in order to start a conversion, we have to determine if our idea makes sense in the first place.
A road bike is designed for efficiency: it aims to reduce drag, which is very, very, very pronounced after especially 30 km/h, and let the rider pedal more efficiently. For a rider to go “aero” position, rider leans forward, grab the handlebars at the bottom point, and lay as parallel as possible to the top tube. Road bikes are narrow, and bottom brackets are lower. They are much more aerodynamically efficient compared to MTB, touring bikes, hybrid bikes; well, any other bike! Also, center of gravity is lower, which is good for stability.
Most road bikes, especially newer ones, are designed in zero comfort in mind. I see middle aged man, never properly ridden a bike buy racing oriented road bikes. A road bike doesn’t have to be utterly uncomfortable.
Carbon bikes, in order to look sexy for clueless buyers, have weird angles and design choices. In the past, you can have a road bike that is both comfortable enough, but also slick. Carbon fiber bikes are not just uncomfortable, they are also unforgiving: super stiff frames are not good unless you’ re in velodrome. Also, very short chainstays means not just decreased comfort, but stability too. I came to think that frame manufacturers are trying to save on materials which are crazy expensive; also keeps the weight down. Longer tubes are means more material; not just longitudinally: in order to achieve same strength, you either have to enlarge the tube diameter, or wall thickness…more material, more weight. They are advertised as being more “agile” – a road bike does not have to agile, it has to be stabile. You expect agility from an MTB; not a road bike.
Why MTB frames are not fit for road bikes?
I won’t go into frame slang, but there are 2 parameters that are vital: reach and stack. To understand reach, draw an imaginary line from bottom bracket upwards vertically, to the upper level of headtube: distance between those 2 points is “reach”.
“Stack” is the difference between horizontal line from upper headtube end and bottom bracket’s horizontal line, as shown.
Without adding lots of parameters which will mess people’s mind, let’s talk about reach and stack: First of all, you need to have a frame that is tall enough so you can pedal with your knees almost locked at bottom stroke, but short enough so you can sit on saddle, not jump onto it like a horse. Once seated, reach should be long enough so you can stretch to handlebars and can take aero position without bending your back as if you’ re having a hunch, and short enough so you can still reach the handlebars and operate levers comfortably.
This is where most MTB frames, especially newer ones fail: They have huge reach compared to road bike frames, but generally ridiculously low stack in contrast to road bikes. You generally end up with very long reach, but very short stack. I have a medium size MTB frame that is having a stack of ~62 cm, but reach is somewhere at 45cm territory, which is pathetic, and such conversion will never work.
You’ ll need to buy a road bike fork, which is not cheap. Do not buy MTB or trekking specific rigid forks. These are quite long to maintain “correct” MTB geometry, but not fit for road bike conversion. If you have to, you can use those forks. Why? Because you may opt to go for disc brakes, or cantilevers, or V-brakes even. In order to use proper road bike rim brakes, buy a road bike fork. You have to get the correct size fork: Newer MTB frames generally have oversize headtubes, which are generally 1 1/4 at bottom, 1 1/8″ at top. You can use some conversion kits, but it is best to get the correct size beforehand.
Assuming you are using a 1 1/8 frame with a 1 1/8 fork, ahead set, you’ ll probably need new stems. Road bikes have generally 100mm long stems, or longer, with rather small angles, or flat. Stem choice is important, as it will effect the final fit of the bike.
You’ll probably need a longer stem but do not shop for it yet – first, complete the bike build, use your old stem, and try to determine which size fill fit better.
You may have no problems, or run into lots of problems – some are not even solvable – depending on your wanna-be road bike frame candidate.
Standard cranksets for for road bikes are generally 53-39, 52-36 double, or 50-34 compact double; or 50-39-30 triple. With gravel bikes, we start to see “sub-compacts” like 48-32 or 46-30. Unfortunately, 3x chainring on road bikes is a dying breed. You’ll not see a SRAM or Campagnolo crankset with 3x chainrings. Shimano’s best is Tiagra 4703; which will go extinct. Your best bet is either 8 speed Claris or 9 speed Sora after that; don’t know how long will they make them. Will road cranksets fit your MTB? There are many things go wrong here: Newer hardtails have short and wide chainstays. This means, I can confirm that any 50-34 sub compact road crankset won’t fit, because small chainring will rub chainstays, or even won’t get into the shell at all, since chainstays obstructing it. Triples are a safer choice; but you have to try before you buy. Every frame is different.
Other problem about road cranksets is, they have different chainline. Generally, chainline is the smallest problems of all. Especially if your crankset is square tapered: you can then experiment with different bottom brackets with different width.
Third problem is the front derailleur. As you can see, most road cranks have 16 teeth difference between chainrings, while MTB / trekking front derailleurs max out at 14. That’s not all: MTB derailleurs have shorter cages which cannot handle big chainrings such as 53T; while bigger capacity front derailluers like Shimano Alivio’s can handle up to 48T theoretically, but can work with 50 or maybe 52T. This is a well-known problem: before GRX or other gravel / cyclocross oriented groupsets, some manufacturers used MTB cranksets with road derailleurs; but problems doesn’t end here: if you’ re going on road derailleur route, you also have to find a one that matches your seatpost angle; well, MTB and road frames generally have different angles, sorry.
So, is there a reasonable way? Yes. Buy a 48-38-28 or 48-36-26 crankset like Shimano Alivio T4060. Unfortunately, SRAM even doesn’t make doubles. So, Shimano is your best bet – they luckily have lots of 3x options available in 48T. Why not 2x? Because they are too small: biggest chainring size is 42T which is too slow for a road bike.
Out of curiosity, I compiled a list of available Shimano cranksets that can be used to convert your MTB / trekking / whatever frame to road bike (sort of):
- Tourney TY FC-TY501, 6/7/8 speed, Square taper bottom bracket, 48-38-28T, 50mm chainline, 185.5mm Q factor
- Tourney TX FC-TX801, 6/7/8 speed, Square taper bottom bracket, 48-38-28T, 50mm chainline, 187.8mm Q factor
- Acera FC-T3010-8, 8 Speed, Octalink bottom bracket, 48-36-26T, 187.3mm Q factor, 50mm chainline
- Acera FC-T3010, 9 Speed, Octalink bottom bracket, 48-36-26T, 187.3mm Q factor, 50mm chainline
- Alivio FC-T4010, 9 speed, Octalink bottom bracket, 48-36-26T, 50mm chainline, 187.8mm Q factor
- Alivio FC-T4060, 9 speed, Hollowtech II bottom bracket, 48-36-26T, 181.7mm Q factor, 50mm chainline
- Deore FC-T6010, 10 speed, Hollowtech II bottom bracket, 48-36-26T, 181.5mm Q factor, 50mm chainline
- Deore XT FC-T8000, 10 speed, Hollowtech II bottom bracket, 48-36-26T, 176mm Q factor, 50mm chainline
There are also some Chinese alternatives like SR Suntour XCT or XCM, either 8 or 9 speed, mostly square taper or octalink. Sunrace and Sunlite are good contenders, cheaper then both Suntour’s and Shimano’s lowest Tourney, but weighing less.
Then comes the biggest problem: shifters and derailleurs. Dropdown shifters are crazy expensive; luckily you can get Micronew, Sensah or LTwoo at AliExpress. I suggest not to go over 3×9, because otherwise you cannot mix and match rear derailleurs: until 10 speed, Shimano road and MTB derailleurs, and most Sram’s, are compatible. I did not see any 3×10 shifter combo for road bikes. While it may be theoretically possible, I doubt 3×10 combo will work for road bikes: Even you change the 2x shifter that comes in 2×10 setup with a 3x front shifter, road front shifters have trim function that will not be compatible with a 10s setup. That is not tested. If someone tested that, let me know.
I’ ll be trying the new “brifters” that Chinese made, probably Micronew or LTWoo. Micronew is much like Shimano with 2 smaller levers for upshifting or downshifting; LTWoo is like lower end Shimano or Campagnolo – One big lever, and one small thumb shifter on inner side. Sensah works like SRAM shifters; so a single blade is used for braking, upshifting and downshifting. All 3 brands uses Shimano pull ratios, so you can couple Shimano deraiulleurs if you like.
Some very cheap road bikes use old style brake levers without shifters, and have MTB like shifters mounted nearby stem. I only came across Shimano ones so far; these are 2×7 or 3×7 shifters: SL-A050 from Tourney line. These have indexed or friction type models.
Most people wants to know if 700c wheels fit 26″ frames. I have a small, 26′ MTB frame. Even 700x35mm fits.
Let’s not talk about Boost for a while, as it complicates things: there is another issue. Standard, now “old” MTB hubs are 135mm wide (O.L.D) while road hubs are 130mm at rear end. So, if you have 29″ MTB wheels, that will fit nicely. The issue is, MTB wheels are for large tires, where putting a tire that is 25mm, even 23mm is a risk. Most MTB rims are 19 or 21mm (or even higher) internally. A rim with 19mm internal diameter accepts minimum 28mm tire. Otherwise, you may get pinch flats at best.
I successfully fitted a road wheelset to my MTB by fabricating a special washer with lathe. This is a small trivial thing, and its already available at AliExpress. What it does to sit between hub flange to “fill” the 5mm gap.
I don’t know a way to fit a standard road wheelset (with QR axle) to a boost rear, either 142 or 145mm or maybe even more.
Road hubs will fit road forks, or rigid MTB / trekking forks if they’re 100 mm O.L.D. Same as MTB. If your fork is not thru axle, road front will fit yours.
Ok, here we go again! Brakes are often overlooked, but perhaps the most problematic thing about such conversion.
If your frame is built in this century, it does have disc mounting tabs.
In short, you have these options:
– Get shifters with hydraulic cylinders, and couple them with your hydraulic calipers. Depending on piston diameter / stroke of shifters’ master cylinder, you can have under/overpowered brakes.
– Get shifters with cable brake option, and couple them with mechanical disc calipers on fork / frame. However, mechanical disc calipers are designed for flat bar bike levers, and pull ratios are different. You may need to buy an adapter, or they can work just fine, depending on caliper model.
– Get shifters with cable brake option, and couple them with cable pull, hydraulic calipers on fork / frame. TRP has well-known parts for this conversion, but it’s not cheap. Your last resort is AliExpress, again. They sell these type of calipers cheap, and they’ re quite good.
– Get shifters with cable brake option. Use a road fork with standard road rim brakes, and modify your frame to accept road rim brakes. Depending on your frame, this can be easy / hard, and safe / risky: Easiest approach is to drill a hole into seatstay bridge, which compromise frame structure.
– Get shifters with cable brake option. Build a horse shoe adapter, and use MTB V-brakes. For this conversion, you may also need a brake ratio adjuster.
Best frame candidates for road bike conversions
Trekking, touring or city bikes with triangular structure best fits the bill, because they have shorter top tubes and longer seat tubes, and the closest match to a road brake. These bikes also have narrower chainstays, which lets you use narrow Q-factor cranksets with bigger chainrings.
Older, commonly steel MTB frames are good candidates too, because of their similar geometry to a road bike, and they generally have longer chainstays without fancy shapes. Steel frames are easier to work with, especially if you are planning to use rim brakes of any kind, as you can braze on brake bosses, or add extended seatstay bridges to fit road rim brakes.
Most hardtail frames built after 2005-2010 is a tough choice, because of their high reach and low stack, which is exactly the opposite of a road bike frame.
26 frames are the best – with 29″ hardtails, you will have silly amounts of wheel clearance. Also, they are heavier, if that matters in a such conversion.
Disadvantages of road bike conversions
They will never come cheap even if you buy the cheapest parts, or second hand. Buying a second hand road bike from the start is way cheaper, but if you have lots of parts laying around like me, it can be cost effective.
What you must consider in such conversions is that, they will never handle like a road bike, because of geometry. I’ ll not go into every detail like fork rake, as it deserves another post, but at least, you’ll have a high bottom bracket, for example – which raises center of gravity, which is not good if when you’ re going downhill at 90 km/s.
Obviously, real road bike frames are not just handle better, they are also lighter and more aerodynamic. MTB’s or hybrid bikes have wider rear ends, which is not good for aerodynamic, let alone newer carbon fiber frames have almost no tire clearance for reducing drag (and comfort, stability and tire options).
Planning, gathering the parts and putting it all together is no easy task; but time-consuming and puzzling, because you have to know every detail. Even very trivial parts will cause problems; like barrel adjusters: most road bike derailleurs do not have barrel adjusters, never seen one on a road front derailleurs or shifters. So, you have to buy 2 inline barrel adjusters at least. This is a small example, but if you miss them, you probably cannot complete the build process that day.
Advantages of road bike conversions
People never learn without trying, making and get themselves hurt in many ways. I think such endeavors teaches a lot. You’ ll be making a bike, solving problems and learning many things during the process.
Building a road bike out of an MTB frame and parts was stemming from a necessity in my case, as I have lots of MTB parts, including a 26 frame laying around. This is a bike I use with my trainer, so handling, aerodynamics and some other advantages of real road frames does not matter. All I needed was a frame with dropbars, that’s it.
If you still have the parts, you may want to try out if a road bike is for you. I know many people “upgrade” from an MTB to road bike, and go back later on. A road bike is an entirely different thing, compared to an MTB or a trekking bike. It’s like driving a rally car: most people think they would set some world records with them, but it is really hard to handle. I once drove a rally car for a short distance, and it was really hard to control: clutch is very hard and instant, idles at 2000rpm and power band is very narrow; though it becomes a beast at over 4000rpm. Not to mention suspension was rock hard, tuned for asphalt. You cannot go fast in such a car on a rough asphalt, because it bounces like a tennis ball and tires constantly lose contact with the ground. Road bikes are such creatures. They are fast but unforgiving. Speed is enticing, but if you have good roads to ride. That’s why most people like them first, but switch back to MTB later, because they don’t ride well anything other than smooth asphalt. Maybe that’s why gravel bikes became so popular.
With an old school MTB frame, you can have a nice road bike that can be ridden occasionally, though.