Gap Between Headset And Fork! (Must Know Things)

Gap Between Headset and Fork

A strong and capable bike is all you need for easy movement within the city.

Negotiating a good bend or passing over a porthole is possible when your bike’s headset and fork align. So, what does it take for both to align?

The gap between the headset and your bike’s fork should be at least one millimeter. Modern bikes don’t have a gap between the headset and the fork. This gap is dependent on the bearing between the headset and fork. 

Is it Normal to Have a Gap Between my Headset and Fork?

Gap Between Headset and Fork

Yes, it is normal to have a gap between your headset and your bike’s fork. However, most modern bikes have no gap between the headset and the fork.

If you find a gap between your headset and fork, it shows that a part is missing.

Commonly, the manufacturer fills that gap using a plastic ring that performs the seal function. A seal between your headset and fork prevents the entry of tiny dirt or dust.

The absence of the plastic ring might be that the supplier did not supply it when bringing the headset, or you must have misplaced it at some point.

Seeing the gap between your headset and fork might be normal, especially considering how well the bearing is seated on the crown race. 

A good adjustable headset allows for the smooth movement of your bike’s head from side to side.

When you’re in doubt, you can also return to where they installed the headset to access more information; shockingly, they will tell you what you see is normal.

#1. Types of Headset 

There are different types of headsets for specific bikes.

You put some factors in place to determine the kind of headset your bike needs Bikes such as road bikes, mountain bikes, and a combined species of road and mountain bikes. Below, you consider some of the factors:

#1. Head Tube Type

You require a headset cup for a press-fit head tube type. This head tube type is either the press-fit or the integrated. The headset bearings usually sit inside the headset cups. 

The press-fit head tube could come in either the zero stack headset or the external cup.

The external has a taller stack height when compared to the zero stack headset cup, which houses the bearings.

The Integrated head tubes come with molded integrated races, which are a part of your bicycle’s frame, and you test the bearings on it. 

#2. Head Tube Dimensions

It would help if you considered the head tube’s dimensions when you want to have your headset changed.

You use a good set of calipers to measure your press-fit. After measurement, you could find the head tube dimensions numbers like 44mm, 49mm, or even 56mm.

#3. Fork Steerer Tube Dimensions

Virtually all modern bikes have an upper steerer tube with outer dimensions of about 28.6mm. Some of the fork Steerer tubes are straight, while others are taper.

For the straight, the steerer tube had a crown race seat dimensions of 30mm, whereas that of the tapered steerer tube tapers off to 1.5 inches.

How do I Measure my Fork Headphone?

You use a good set of vernier calipers to measure your fork headphone to get an accurate measurement. Here’s how to measure your fork headphones.

Firstly, measure the fork at the bottom of the steerer tube; this measurement will give you your crown race diameter.

For instance, after measurement, you get a value of 26.4mm, it shows the crown race is called ‘ISO’ but in situations whereby the value got is 27.0 mm, then it is called ‘JIS.’

Next, you measure the inside of the frame head tube of your bike. If the value obtained is 30.0mm after measurement, it is a JIS headset or a proprietary Raleigh headset.

If the frame measured is more or less slightly wider at 30.2 mm, you are dealing with an ISO headset.

You measure precisely the inside and outside diameter of the fork where the bike’s stem goes, starting from the top.

In a situation whereby you got the outer diameter to be 25.0 mm and the inner diameter to be 22.0 mm, the headset you need is a French type.

Or after measurement, if you got an outer diameter of 25.4 mm and an inner diameter of 22.2 mm, then it is the ISO/JIS headset you require.

The fork’s threading will greatly help you reach your dimensions compared to the above dimensions.

The same fork could allow all the ISO standards and JIS headset to be threaded interchangeably.

The table below shows the types of the headset and their measurements in mm, making it easy for you to know which size of headset you need: 

Types of HeadsetCrown RaceHeadtubes IDSteerer ODSteerer ID
JIS 27.0 mm30.0 mm25.4 mm22.2 mm
ISO26.4 mm30.2 mm25.4 mm22.2 mm
French26.5/27.0 mm30.2 mm25.0 mm22.0 mm
Italian 26.5/27.0 mm30.2 mm25.4 mm22.2 mm

How Tight Should Your Headset be?

There are a few simple steps you follow to tighten your bike headset. You tighten your bike headset when they are loose or weak. 

However, in some cases where the headset is too stiff, you must loosen it a bit. If you want to tight your headset properly, then all you need to do is to follow the steps below:

#1. Undo Headset Bolts

You undo the two bolts at the side of your bike’s stem. It would help if you took caution not to undo the bolts entirely. After that, you undo the headset bolt. 

You use the Allen key to undo the bolt, which in this case might be a different Allen key. Normally, the side bolts are 4mm, but the top bolt may be either 4mm or 5mm.

#2. Move Headset Spacers

Ensure you put the spacer above the stem when you lower the stem. After all, make sure the stem is straightly aligned. 

When you adjust the spacer placed beneath the stem, you alter the height of the handlebar. The amount you can add underneath depends on how much the fork column you cut. 

#3. Tighten the To Cap

When tightening the headset top cap, apply pressure down on the stem or the spacer above it. You should avoid applying force on the fork column itself.

You will see that your headset will tighten up when you do all these. Please note a warning, do not overtighten it because it might make the headset stiff.

#4. Do up the Side Bolt

You alternate between each side of the bolt as you tighten them up. Ideally, you use a preset torque or a torque wrench so that you do not over-tight the bolt.

The torque you require is usually 5Nm on the bike’s body. You can test your bike to see if you have properly tied the headset.

You do this by lifting the front of your bike off the ground and letting the front wheel and handlebars move from side to side.

If the movement of the handlebar and the front wheel is smooth, you are good to go, but if it is stiff, it is too tight.

MTB Headset Gap

The mountain bike headset gap is between 0.5mm to 1mm. It is normal for a headset gap in your MTB bike.

Most mountain bikes come with this gap for their effectiveness in moving from one side of the mountain to another. However, when these gaps become enlarged, it then calls for tightening. 


The gap between the headset and your bike’s fork should be at least one millimeter, depending on the bearing between the headset and the fork.

Modern bikes don’t have a gap between the headset and the fork. It is normal to have a gap between your headset and fork.

Josh Matthews

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