So you bought a Mongoose Mountain Bike and realized that the seat height is way off.  This article explains step by step how to adjust the seat height on a Mongoose Mountain Bike.

  1. Identify the type of seat height clamp is on your bike. This will be either a swing clamp or a 5mm head bolt.
  2. Loosen the seat clamp bolt or swing clamp (quick release) just enough to enable you to slide the seat up and down.
  3. Slide the seat up to the “Minimum Insertion” mark. This is a safety consideration – more below.
  4. Straddle the bike and roll it forward until seat nose touches your tail bone.
  5. Tighten the seat clamp
  6. Test for comfort

Before I jump into the detailed instructions let’s talk a little about safety.  If you are adjust the seat height for your young child make sure they can comfortable mount and dis-mount the bike.  There is nothing worse than seeing a child ride up to a stop then fall over.

Seat height has a lot to do with comfort and power while mountain biking.   There are more seat position adjustments that can be made to improve comfort and reach to the handle bars.  I’ll probably get into those adjustments in another article.  So let’s get into the detailed steps for adjusting the seat height.

Identifying the type of seat clamp

Mountain bikes will have two types of seat height adjustment.

  • An adjustable clamping system that uses a swing clamp (quick release) or bolt to tighten on the SEAT TUBE.
  • Custom seat height, high end carbon and aluminum frame bikes will integrate the seat tube into the frame. This save precious weight.  With this system the seat tube is CUT to fit the rider.

All Mongoose mountain bikes will have an adjustable seat tube with a clamping system.   Adjustable systems are great, they enable the bike to “Grow” with the rider.

Some tools may be required to tighten the clamp, the most common wrench needed is a 5 mm Allen wrench.  There isn’t anything special with the bolt direction so use the “Righty, Tighty – Lefty, Loosey” technique for turning the bolt.

If you have a swing clamp seat, to loosen the clamp.  Grab the swing arm and swing it away from the seat tube.  What’s nice about this system is that you can quickly adjust the seat without any tools.

How bike seat posts work
How bike seat posts work

Loosen Seat Tube Clamp Just Enough

During the seat adjustment process I mentioned loosening the clamp just enough to allow the seat tube to slide, but not free fall into the frame.  This is to test the position without actually sitting on the bike.  Sometimes finding that perfect tightness can be tricky especially if the bike is new.

If you have an older bike the clamp might be frozen or rusted into position.  If this is the case, liberally apply some penetrating spray to the joint and wait a bit for it to sink in.  I use WD-40 but any penetrating spray will work.

Slide the seat up to the “Minimum Insertion” mark

Every seat tube has a marking that shows the “Minimum Insertion” for the tube.  This is a safety consideration.  Usually the words are stamped onto the tube with a stamped hash mark ring all the way around the tube.

Again the clamp is gripping just enough to hold the seat position without gravity dropping it down.

If you see this ring after adjusting the seat height, you’ve out grown the bike.  Positioning the seat above this mark will cause frame failure.  Which could result in injury.   Just don’t risk it.  I’ve broken bike frames and usually it occurs at the worst time.

So slide the seat up to the hash mark and move onto the next step.

Straddle the bike and roll it forward until the seat nose touches

This step sounds tougher that it really is.  Straddle the bike, but don’t hop onto the seat.  I step through the middle area of the frame.   Grip the handle bars like you were about to ride.  Your feet should be flat on the ground.

Roll the bike forward until the seat nose touches your back.  With young kids this is sometimes way up on their back.

When the seat nose touches your tail bone, hop off the bike.  Be careful not to knock the seat out of position.

90% of the time this is the perfect spot for the seat.

Tighten the seat clamp

With the seat in position, tighten the seat clamp.  Either screw the bolt in or swing the cam lock over.  As you tighten the bolt or swing the clamp over double check to make sure the seat is pointing straight.

how to adjust height on mongoose seat
how to adjust height on mongoose seat

At this point I’ll also inspect the seat post clamp assembly for damage.  This is unlikely to be hit since the seat protects this from impact.

Usually I’ll spray a little penetrating oil onto the surfaces to reduce the chances of rust.

MTB Tools I Love and Recommend

Bike Hand Repair Stand
Bike Hand Repair Stand
Bike Hand 37 pcs Tool Box
Bike Hand 37 pcs Tool Box
Topeak Smartgauge D2 Air Pressure
Topeak Smartgauge D2 Air Pressure

I own each of these tools and only recommend things I own and use.

  • Bike Hand Bike Repair Stand.  Nice mountain bikes don’t have a kick stand so keeping your MTB safe but conveniently stored is essential.  I keep my bike on my stand whenever I’m not riding it.  This makes it easy to lube the chain, inflate the tires and adjust the derailleur.  Highly recommended – Bike Hand Bike Repair Stand (👈 Link to Amazon to see what thousands of others have said)
  • A basic MTB toolbox for replacing a chain, adjusting brakes and dialing in the fit.  Bike Hand has a 37-piece box that has most of the specialty bike tools to keep your MTB properly maintained.  The Bike Hand brand is value packed for the avid rider.  Check out the competitive prices with this link to Amazon 👉 Bike Hand 37 pcs Bike Repair Tool Kit
  • Get a good air pressure gauge, if you get just a tiny bit serious about MTBing you’re going to start playing with tire pressure.  A couple psi can make your tires sticking or not.  Get a good gauge, I highly recommend the Topeak Smartgauge D2, it’s accurate, flexible and easy to use.  An Amazon best seller, here’s a link 👉 Topeak Smartgauge D2
  • Carry a multitool with you on every ride.  I’m serious, most of the time you can MacGyver something to get back to the trailhead if you have a multitool.  I’ve got the Crank Brothers M19, it’s worn, rubbed and abused – but it still works.   Thousands sold on Amazon – check it out with this link 👉 Crank Brothers M19

Test Ride for Comfort

Now is time to try it out.  Again two things to consider: safety and comfort.  Young kids should be able to stop and touch the ground with their tippy toes.  Like I said before improper height will cause a crash either starting out or stopping.

A test ride is more than 30 seconds.  Go around the block, while pedaling think about comfort.  Stop a dozen times, to check out how it feels.  Can you stop with your butt on the seat?

Before the test ride drop your 5mm allen wrench into your pocket if your bike has a tightening bolt.  After 10 minutes of riding if you think something doesn’t feel right.  Stop and make a minor adjustment.

Tightening the Seat Clamp to Stop Movement – Quick Release

Sometimes with the swing or quick release doesn’t seem to hole the bike seat in position.  It either slides down or twists back and forth.  This is pretty easy to adjust swing cam clamp for movement if the seat moves.  Simple grab the thumb nut on the opposite side of the lever and tighten it in a couple turns.  This increases the grip of the cam lock.

Learn more about Pedals, Handlebars and Brakes

Seat Height Adjustment for Power

To get the most power from your pedal stroke some of the items above get tossed out the window.  For kids and general riding safety when starting and stopping are critical.  Pedaling for power incorporates a couple other criteria.  Most of the measurements roll into the three touch points on the bike.  (Hands, bottom and feet)  The starting point is with the pedal the dead center bottom of the stroke your knee should be bent at 25 to 30 degrees.

This position allows for you to lift your bottom off the seat for obstacles and still get the full power of the pedal stroke.

Gravity riding or stunt bikes will have the seat even lower.  Most of the riding is done off the seat so the seat is almost an afterthought that needs to be out of the way

So what is a Dropper Seat Post for Mountain Bikes?

Dropper seat posts are telescopic seat posts whose height can be adjusted while riding.

Usually with the flip of a lever or the push of a button the seat height can be adjusted to the optimum height for the trail conditions.  You’re going over lots of roots and rocks.  Push the button and lower the seat, the trail opens up to a long flat and straight away, push the button and raise the seat for power.

Other Saddle Adjustments Tilt and Front to Back

Usually Mongoose does a good job of positioning the saddle.  Generally having the seat level and in the mid-point of the seat rails is a great starting point.  We’ll get into adjusting the seat forward and back, along with tilting in another article.   Stay tuned!

I’ve written quite a bit about Mongoose MTBs, mostly how to keep them running. Check out –


David Humphries is the creator of DIY Mountain Bike. For me a relaxing day involves riding my mountain bike to decompress after a long day. When not on my bike I can be found wrenching on it or making YouTube videos at 👉 DIY Mountain Bike Read more about David HERE.