Condensed answer: Shimano and SRAM road bike cassettes can be installed on a mountain bike as the splines of the hubs are the same across the MTB and road models of both brands. However, a Campagnolo road cassette will not fit on an MTB hub.
The Benefits Of Installing a Road Cassette On an MTB
1. Smaller Gear Jumps
The gears on road cassettes come with smaller jumps to ensure smooth pedaling in a group. The gradual increments make it easier to maintain high cadence and fluid movement.
Cadence is a term referring to the rotations of the cranks per minute. High cadence (e.g., 90RPM) is associated with greater average speed and minimized energy expenditure.
If you already have a road cassette or can buy one for cheap, installing it on your MTB will save you money that can be invested elsewhere.
3. Beneficial For Commuting On Consistent Terrain
If you’re commuting on terrain with small gradient changes, then a road bike cassette will ensure a smoother transition. The jumps on an MTB cassette, on the other hand, could feel a bit too large.
What Are The Downsides of Installing a Road Cassette On an MTB
Road bikes use higher gears because it takes less effort to propel the bike forward thanks to the lower rolling resistance of the tires and the more aerodynamic position of the rider.
Consequently, the lowest gear on road cassettes is often under 30 teeth. By installing such a cassette on an MTB, it will become more difficult to conquer hills.
Mountain bikes use thicker tires with greater rolling resistance and put the rider in a less aerodynamic position. When you add the high gearing, you will notably increase the force needed to pedal the bike uphill.
This effect is less noticeable when one is using a triple chainset with a “granny ring”. But if you have a 1x or a 2x drivetrain, it will be wiser to stick with MTB cassettes offering greater low gears.
When the gears are close, one often has to make more shifts to feel a difference. Sometimes one upshift or downshift isn’t enough to reach a gear corresponding to the desired cadence.
Comparing The Jumps On MTB and Road Cassettes
The table below shows the total range of MTB and road cassettes per number of available speeds.
The “jumps” column contains the number of teeth on each cog. The “Min and Max Jump” column indicates the minimal and maximum jump in percentages.
Note: I’ve used mid-range Shimano and SRAM cassettes to extract the data.
|Speeds||MTB||Jumps||Min and Max Jump||Road||Jumps||Min and Max Jump|
The table reveals that the first 3-6 sprockets on road cassettes between 9 and 12 gears differ only by a single tooth.
Meanwhile, the first 3-6 sprockets on MTB cassettes between 9 and 12 gears differ by 2-3 teeth.
SRAM and Shimano
The term spline refers to the grooves/pattern found on the freehub driver – the place on which the cassette slides.
If the splines of the hub do not match the cutouts on a cassette, then that cassette cannot be installed on the hub.
Shimano and SRAM MTB and road cassettes have exactly 12 “cutouts” and can therefore be exchanged between road and MTB bikes.
The only requirement is to have a hub that is compatible with the number of gears on the cassette.
8-12-speed hubs are of the same width and one can therefore replace cassettes fairly easily. However, if you have a hub designed specifically for 7 or fewer speeds, then the hub’s body will be too short to accommodate an 8+ cassette.
A Campagnolo cassette would not fit on a Shimano or SRAM hub due to the different cutout pattern. One needs a Campagnolo hub to use a Campagnolo cassette.
However, since we’re talking about installing a road cassette on an MTB, it’s unlikely that your bike is equipped with a Campagnolo hub because the company is focused on road bikes.
FAQ: Can I use a road derailleur on an MTB?
Road and MTB derailleurs aren’t always interchangeable because some models have a different rear shift ratio.
The rear shift ratio of a derailleur describes how much the unit moves per 1mm of cable pulled or released by the shifter.
For example, if a derailleur has a 1.7:1 rear shift ratio, the derailleur moves 1.7mm for every 1mm of cable movement initiated by the shifter.
In order for two derailleurs to be interchangeable, both models have to answer the following criteria:
- Equal or greater capacity (You cannot use a short cage derailleur on an ultra-large MTB cassette.)
- Matching rear shift ratio
If a derailleur has an inappropriate rear shift ratio for the number of gears that you have, it will move too little or too much when you try to shift.
Of course, this matters only if you’re using indexed (modern) shifters. If you rely on friction (old-school) shifters, the rear shift ratio is inconsequential because the friction shifter is 100% controlled by the rider and can be repositioned to compensate.
Shimano’s MTB derailleurs have a 1.7 rear shift ratio from 6 to 9-speed models. Shimano’s 10-speed road derailleurs also have a 1.7 rear shift ratio. This means that Shimano’s MTB 6-9 derailleurs and the 10-speed road derailleurs are interchangeable as long as the derailleur can cover the entire cassette.
However, 10-12 speed MTB derailleurs and 11-12 speed road derailleurs have a different rear shift ratio and are therefore not interchangeable.
SRAM’s 10-speed road and MTB exact actuation derailleurs have the same rear shift ratio as SRAM’s road 11-speed exact actuation derailleurs. Thus, one can use a 10 or 11-speed exact actuation road derailleur on an MTB drivetrain as long as the capacity is right.
Summary: What You Need To Know
- Shimano and SRAM road cassettes can be installed on MTBs when the hub is wide enough for the number of sprockets on the cassette.
- Campagnolo cassettes are not compatible with MTB hubs.
- Road cassettes have higher gearing and smaller jumps between each gear. This property makes hill climbing a bit difficult but allows cyclists to maintain steady cadence over flat terrain.