120mm Fork On 100mm Frame: Will You Die Or Be Safe?

Experimenting with different bike parts is exhilarating. But compatibility issues are the party pooper here.

Nowadays, we often try to mix-match different sized forks and frames together. There is an existing dilemma about this pairing and the uncertainty is sky-high.

So, can you fit a 120mm fork on 100mm frame?

You can fit a 120mm fork on a 100mm frame, and it’ll work! Note that, there are advantages and disadvantages to this pairing. You’ll get better control (air and ground) and faster acceleration with the 120mm fork. Yet, you’ll need to sacrifice the aesthetics and making sharp turns will be tough. 

Is that all? Obviously not! You’ll need more information before making this big decision. But fret not! I’ve explained all the pros and cons of using a 120mm fork on a 100mm frame.

Get started now!

Is It Possible to Put a 120mm Fork on a 100mm Frame?

We know that the frame holds every important part of any bike. Matching the parts with the frame size is important. Yet, it’s not always possible to do so. There may be a bit of a mismatch in the sizes.

So, there are two groups on this topic. One side believes that the fork and frame size has to match. If the sizes do not match, the bike will be dysfunctional.

On the contrary, the other group believes the opposite. These people think that matching fork and frame sizes are good, but it isn’t necessary. 

Source: Black Bean Lounge

A 120mm fork on a 100mm frame.

As you can see, there is a dilemma existing between fork and frame sizes! You can easily lose yourself between these two groups. So you might ask, can I put 120mm forks on a 100mm frame?

Yes, you can put 120mm forks on a 100mm frame! In fact, you can use this as a cost-saving strategy at times! It’s also a good fit if you’re using a mountain bike.

The frame holds the other parts of the bicycle. Accordingly, it is far more important than the fork. 

Let’s say you have got 120mm forks at a discount. So, would you need to change your frame as soon as possible? The answer is- no.

The 100mm frame will be compatible with it. Whether it’s a giant talon 120mm fork or a specialized chisel 120mm fork, it’ll fit just fine. So, you can upgrade the frame at your convenient time.

Note that, you may own a 140mm fork. In that case, you might wonder, can I put 140mm forks on a 100mm bike?. 

The answer will be no. It won’t be safe; since there is a gap of more than 20mm. The cycle might actually break! These are some symptoms of too big forks.

You should avoid putting forks that are more than 20mms compared to your frame size. For instance, a 140mm fork on 100mm frame is a bad idea.

At this point, we know putting a 120mm fork on a 100mm bike is possible. You can easily do this at your home if you want.

Still, it’ll differ from matching a 120mm or even 110mm fork on 100mm frame. Let’s know the effects of putting a bigger fork.

Advantages And Disadvantages of Putting 120mm Forks on 100mm Frame

Since pairing up is possible, you might think it’s okay for all cases. However, it does not apply to every situation.

Pairing up a 120mm fork and a 100mm frame may be possible, but it’s not recommended for everyone. It has its advantages and disadvantages.

Below, I’ve elaborated on the pros and cons of this combination. If you’re trying to decide on this decision, the discussion will help you immensely. Check it out.

Advantages

Let’s see some advantages of pairing up a 120mm fork with a 100mm frame-

Increased Acceleration

You can accelerate much faster than usual. 

Since their central gravity will be shifted towards the backside, the wheels can spin faster. Especially the front wheels. 

The front wheel is the main contributor to accelerations, so in that sense, you’ll have increased bike acceleration.

Better Control

The control of the bike will improve when you achieve high speeds.

The ratio of weight will increase when the frame is taken into account. The 120mm fork’s size will be bigger and heavier. This weight can improve control.

Additionally, the fork will elevate the angle at the front. This will help with the turning because there will be less pressure on the front wheel.

Improved Drops

You can achieve better drops and jumps on a mountain bike.

Due to this reason, many mountain bikers keep their fork bigger than the frame. The airborne control of the bike is easier due to the weight shifts! 

Source: Bike Radar

Following the first advantage, you’ll need less strength to turn the front wheel. Since the weight will increase, it’ll improve the control. Here’s a first-time riding review of the 120mm travel fork Sonder Cortex.

When you’re landing, the front wheel will land faster. The same goes with when you’re going airborne. The big fork improves the efficiency of the bicycle.

Disadvantages

Let us look at some disadvantages of this setup-

Less Appealing Aesthetics

You’ll be sacrificing bike aesthetics. 

When you attach a fork that is bigger than the frame size, the bike will elevate. This elevation will make the bike look a bit deformed. Some people do like this structure but for some basic usual structure is more aesthetically pleasing.

Source: DIY Carbon Bikes

However, it mostly depends on personal tastes. The bike structure won’t look like a regular one, that’s all.

Less Sharp Turns

Making tight turns will be a hassle. 

A 120mm fork on a 100mm frame will decrease the turning radius of your bike. Although you will require less force to turn the handles; you will need time. 

There’s a big chance the bicycle will lose balance when making a tight turn. Sharp turns are something that is dangerous and you have to watch out for them.

So, if you’re traveling at a high rate and a steep turn is approaching, slow down! You may simply make the turn with less speed and without risk!

This disadvantage is also seen when pairing up 26 size frames and 27.5 forks.

More Hassle

You have to change your braking pattern.

This is a disadvantage because oftentimes, you have to apply a hard brake on a bike. Yet, applying a handbrake on a 120mm fork will almost topple the bike over.

So, you have to either maintain your speed when riding or get used to soft brakes. This is actually one of the main differences between 100mm and 120mm forks.

Also, you will need an air spring to reduce the 120mm fork into 100mm fork. So that it suits your 100mm frame. You can use the air spring from Fox Racing Shox. This will cost you around $35-40.

Also you’ll need to oil up the whole fork after reinstalling it. You can use WPL Forkboost Lube or Lucas Oil 10771 Fork Oil for that purpose.

So, there are some advantages and disadvantages of 120-100mm setups!

Should You Put a 120mm Fork on a 100mm Frame?

All of these conversations might have you a bit confused. Well, don’t worry. Let me sum up all the pros and cons of this setup for you!

The decision is solely based on your priorities. 120mm forks can give you more air control in mountains. It also provides better control at high speeds. However, you’ll be sacrificing aesthetics.

Alternatively, you can match the 100mm frame with a 100mm fork. That way, the regular turning radius, and speed controls will be maintained. 

Also, your bike will be more visually pleasing. If you have a hard time adapting, don’t put 120mm forks on your bike.

FAQs

Can you put downhill forks on a hardtail?

Yes, you can put downhill forks on a hardtail. For off-road biking, hardtail bikes are some of the best bikes! Downhill forks on a hardtail bike can make bike riding easier for you. Usually, when riding downhill, you have to pull the speeds. With a hardtail, pulling the speed becomes an easy task.

Can you jump with a 100mm fork?

Yes, you can jump with a 100mm fork. Usually, forks are designed in a way that you can jump with them. Forks are basically a suspension system for your bicycle. You can apply force on the handlebars towards the ground. When you release it, the counterforce can make the bicycle jump! It’s a very fun thing to do.

Is 120mm enough for trail riding?

Yes, it can be enough for trail riding. However, small bikes are the best for trail riding. In this case, 120mm will only fit bigger bikes. Bigger bikes will increase weight and decrease efficiency; when considering trail riding. So ideally, it is possible to trail ride with 120mm but it is not recommended.

The Final Words

I hope now you’re crystal clear about everything about putting a 120mm fork on 100mm frame.

This pairing is a very creative option for your ride. But, these changes are not for everyone. If you face difficulties with this pairing, match your frame and fork sizes!

All the best!

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