Condensed answer: Rear MTB hubs are wider than rear Road hubs designed for bikes with rim brakes. Thus, rear road wheels built around MTB hubs won’t fit on a modern rim brake frame.
However, disc-brake-ready road frames have a 135mm rear O.L.D. and can therefore accept a wheel with an MTB hub.
A basic front MTB hub would fit on a road bike regardless of the brake system because most MTBs and road bikes have 100mm front O.L.D.
Requirements to Install an MTB Hub on a Road Bike
1. Corresponding O.L.D.
O.L.D. stands for over-locknut dimension and refers to the usable part of a hub between the two locknuts (image below)
Each frame is designed for a specific O.L.D.
If the hub’s O.L.D. doesn’t match the design of the frame, then the wheel won’t fit (too wide) or will be insecure (too narrow).
The table below contains the O.L.D. of road and MTB bikes:
|100mm (quick release); 110mm (boost hubs)
|135mm (quick release), 141mm (boost hubs)
|130mm (non disc brakes), 135mm (disc brakes)
The information above leads to the following conclusion:
- A basic front MTB hub can be used to lace a “road wheel”. However, if the MTB hub is “boosted” it will be too wide for a road fork.
- A road frame designed for rim brakes has a rear O.L.D. of up to 130mm and thus cannot accept a rear MTB hub by default.
- A road frame built for disc brakes is engineered for a hub with an O.L.D. of 135mm and can therefore operate with a basic rear MTB hub.
- If the rear MTB hub is boosted, then its O.L.D. will be 141mm, and it won’t fit on a road frame.
2. Matching Axles
The fork, the frame, and the hubs should be designed for the same wheel retention system.
The two most common types are quick-release skewers and thru-axles.
If the hubs operate with a thru-axle, but the frame or the fork of the bike are designed for quick-release skewers or bolt-on axles, the combination will not work.
FAQ: What Are The Downsides of Using MTB Hubs on a Road Bike?
As already mentioned, some MTB hubs won’t fit on a road bike.
MTB hubs tend to be heavier than their road equivalents.
The tables below compare the weight of MTB and road hubs.
|DT Swiss 240s Non Disc
|DT Swiss 350
|Novatec A291 SB-SL Superlight
|Shimano XT HB-M756
|DT Swiss 240 Straight Pull
|Shimano XT HB-M8000
|Campagnolo Record Front Hub
|Shimano XT HB-M8110
|DT Swiss 240 Classic
|tune Mig Front Hub
|SRAM 716 Disc
|White Industries T11
|Shimano SLX HB-M7110
Conclusion: On average, road front hubs are 46% lighter than front MTB hubs
|White Industries ENO Eccentric
|Shimano XT FH-M8000
|White Industries CLD Center
|DT Swiss 350
|Hope RS4 Road Rear Hub
|Shimano XT FH-M756A
|DT Swiss 180 Road Carbon
|White Industries XMR
|Rotor RVOLVER Road Rear Hub
|Shimano ZEE FH-M640
|Tune Kong Road Rear Hub
|Shimano Saint FH-M820
Conclusion: Rear road hubs are 35% lighter on average than rear MTB hubs.
Some people will not like the looks of an MTB hub on a road bike.
Road hubs tend to come with fine details adding to the finesse of the bicycle.
FAQ: What Are The Benefits of Using MTB Hubs on a Road Bike?
On average, MTB hubs are stronger than road hubs because mountain bikes endure more stress. The extra durability is also the reason why MTB hubs tend to be heavier.
2. Extra Spoke Holes
Road hubs tend to have fewer spoke holes than MTB hubs because road wheels are meant to be light and aero. However, those properties come at a price – fewer spokes and subsequently a weaker wheel.
Thus, if you have a road rim with 36 spokes, you may fail to find a modern road hub for it in certain bike shops.
3. Superior Seals
MTB hubs have better seals preventing dirt and moisture from getting into the mechanism.
For that reason, some road cyclists who often face bad weather, intentionally put MTB hubs on their road bikes.
4. Recycling of Old Parts
If you already have an MTB hub and want to build a road wheel, using the MTB hub will save resources.
FAQ: Can A Road Frame Be Stretched to Fit an MTB Hub?
The process of bending a frame to accommodate a hub with an O.L.D. that doesn’t match the dropout spacing is known as “cold-setting”.
A frame can be cold-set only if it’s made of steel. Aluminum and carbon frames should not be cold-set because the process weakens the material.
Steel can be bent (cold-set) without notable loss of structural integrity because its ultimate tensile strength is notably higher than its yield strength.
The ultimate tensile strength of a material describes the amount of stress that it can withstand before losing integrity and eventually breaking.
The yield strength, on the other hand, is the point beyond which the material permanently deforms.
For example, Chromium-vanadium steel has a yield strength of about 620 MPa whereas its tensile strength is 940 MPa.
Conversely, 6061-T6 aluminum has a yield strength of about 276 MPa and tensile strength measured at 310 MPa. Since the numbers are really close, cold-setting an aluminum frame is never recommended.
FAQ: I have a steel frame and want to cold-set it to fit an MTB hub? Will I lose the warranty?
Yes. If you cold-set your frame, you will instantly lose the warranty even if the frame is made of steel.
People have been cold-setting steel frames for a long time, but the process is too unregulated for a manufacturer to label it as viable.
At the end of the day, frames are not built with the intention to cold-set them.
Summary: What You Need to Know
1. A standard (non-boost) MTB front hub can be installed on 700c rims (road wheels) right away.
2. A standard (non-boost) MTB rear hub can be installed on a road bike only when the frame is designed for disc brakes. If the road bike uses rim brakes, the hub will be too wide.
3. Boosted MTB hubs would not fit on a road bike under any circumstances.
4. If you have a steel frame and want to install an MTB hub on it, the frame can be cold-set to accommodate the new hub. If the frame is made of another material, cold-setting is forbidden.
5. Road hubs are notably lighter than MTB hubs.
6. MTB hubs are more durable and have better seals preventing water and dust from entering inside the mechanism.