Condensed answer: It’s possible to install pegs on an MTB if the bike has long bolt-on axles. However, by definition, mountain bikes aren’t designed for pegs. If you decide to proceed, you risk damaging the frame and fork.
What Are Pegs?
Pegs are strong metal tubes that attach to the axles of the bicycle and allow the rider to grind ledges and rails. Pegs are very common in the BMX world.
Why Putting Pegs On a Mountain Bike Is a Bad Idea
1. Too much frame and fork stress
Installing pegs on a mountain bike and using them as intended can damage the fork and frame.
The tubing of MTB frames is more susceptible to damage because it’s longer and not as thick as that of BMX bicycles.
When you hop on a ledge, the peg acts as a short lever and stresses the frame and fork dynamically and statically.
In addition, most mountain bike frames are made of aluminum or carbon. Neither of the materials deals well with impact.
Aluminum is soft and can be easily scratched or cracked when hit. Carbon is even less resistant to impact coming from the side. You can total a very expensive MTB frame if you hit it hard on a ledge or a rail.
If you crack an MTB frame or fork as a result of using pegs, the manufacturers won’t respect the warranty due to misuse.
BMX bikes can handle the stress of pegs because they have thicker steel frames made of shorter and more rigid tubing.
2. Difficult And Insecure Installation
Normally, pegs mount to the axles of the bike. However, most MTBs use quick-release skewers whose function and structure are incompatible with pegs – quick-release skewers are too short and cannot be tightened when a peg is attached to them.
A large segment of MTB bikes are switching to thru-axles, but those aren’t the best for pegs either – they are short and not intended for lateral stress.
This leaves only two ways to install pegs on an MTB – by using bolt-on axles or attaching the pegs to the mounts for racks or fenders.
To use the first option, many riders will have to replace their axles because bolt-on models come stock only on department store bikes.
The second method (rack/fender eyelets) is weaker and potentially catastrophic for the frame. The peg is attached via a small M5 bolt which would break or at least bend upon the first landing. The aftermath will more than likely include damage to the frame.
3. Fragile Mech
The rear derailleur of a mountain bike can easily be damaged during grinds. One hit against a ledge would do it.
If the day is particularly unfortunate, the derailleur could get into the spokes and disintegrate the wheel too.
4. Wider Profile
Pegs make the bicycle wider. This is bad news for actual mountain biking because the clearance of the bike is reduced.
If a branch hits the front pegs, you may fall instantly due to a sudden change of direction.
5. Extra Tools
To install or remove a set of pegs, you would need a wrench extension and a socket.
You will have to carry the extra instruments with you. Otherwise, you won’t be able to take off the wheel to fix a flat.
A peg can easily reach over 200 grams. If you run 4, that’s close to an extra kilo on your bike.
Some people find pegs on MTBs non-aesthetically pleasing.
8. Social criticism
Get ready to face some scrutiny from fellow riders.
The Safest Scenario For Installing Pegs On a Mountain Bike
The following conditions reduce the danger of using pegs on an MTB:
1. Chromoly frame
Steel is more resistant to impact than aluminum and carbon. For that reason, high-end BMX frames continue to come in Chromoly.
2. Rigid Steel Fork
Most suspension forks are made of aluminum and aren’t built to resist the lateral stress that pegs create. Therefore, if you want to use pegs on an MTB, it would be better to rely on a rigid Chromoly fork. Alternatively, you could avoid installing front pegs in the first place.
Single-speed bikes don’t have derailleurs and are therefore less susceptible to technical failures during riding.
4. Strong Hubs with Extra Long Bolt-On Axles
Pegs require reinforced bolt-on axles and hubs. Those are hard to find in the world of MTB because the industry relies on thru-axles and quick-release skewers.
Having said that, some MTB frames work with 14mm axles (the same thickness as BMX axles).
5. High Bottom Bracket
If the bottom bracket of the bike is too low, the cranks may interfere with grinding themselves due to the lack of clearance. Hence why you need a high bottom bracket to make this work.
As you can see, the ideal MTB candidate for pegs has to cover a number of requirements taking the bike further away from the current MTB standards.
Are Pegs Designed Solely For Grinding?
In general, yes. However, pegs can also be used for a large variety of street tricks including wheelies and manual variations.
Another non-regulated use of pegs would be people transportation. There are two main ways to accomplish this task.
In the first case, the passenger is standing on the pegs and holding on to the rider’s shoulders or the handlebars. I’ve seen a handful of local BMX riders transport their girlfriends via front pegs.
The other method involves a rear rack. The passenger sits on it and uses the rear pegs as a footrest.
Note: There are also “passenger pegs” offering wider platforms on which the passenger can stand without having to balance as much.
FAQ: Can I run pegs on a dirt jumper?
Dirt jumpers can easily cover many of the criteria required to use pegs.
Most of them come as single-speed units and many have tough Chromoly frames.
However, the forks are problematic since they aren’t designed for peg use. The only notable exception would be 24″ Marzocchi D-Street from 2004-2005. Obviously, this fork is hard to find these days. It’s also quite heavy.
Having said that, some people run pegs on other dirt jump forks by replacing the axles with longer and stronger ones.
Note: If the dirt jumper’s frame is made of aluminum, it’s highly advisable not to use the bike for grinding.
Ultimately, the answer to this question is: you can install pegs on a dirt jumper as long as the bike has bolt-on axles, a Chromoly frame, and a fork that can handle the lateral stress.
What Do You Gain From Using Pegs On a Mountain Bike?
One’s motivation for installing pegs is very important. If you intend to turn a regular MTB into a pure street machine, you may be disappointed because the entire geometry of the bike is designed for a different riding style.
However, if you just want to add a bit more versatility to an MTB used to light tricks, you may like the pegs as long as you acknowledge the limitations and dangers.