How to Adjust the Handle Bars on a Mongoose Mountain Bike

Getting a mountain bike to “fit” takes a couple adjustments.  The Mongoose Mountain Bike one of my kids has needs the handle bars adjusted.  I thought I’d explain how to adjust the handle bars on a Walmart Mongoose Mountain Bike.

1. Figure out the type of stem is on your bike. It will either have a “Quill Stem” which is on most Walmart bikes or a Clamp (sometime called threadless) Stem.
2. If you have a threadless, you will be very limited on the handle bar height adjustment.
3. On a Quill stem turn the handle bars and fork to face forward. Make sure the cables aren’t twisted.
4. With a 6 mm allen wrench turn the stem binder bolt in center of the handle bars in a counter clockwise direction to loosen. Back the bolt up about ½ inch.
5. With the bolt slightly above the handle bars tap on the head of the bolt to loosen the quill.
6. The quill stem will “break free” allowing the handle bars to be raised and rotated.
7. WARNING: the stem will have a MINIMUM INSERTION MARK. Do not raise the stem out of the steering tube beyond this mark.
8. Loosely tighten the stem bolt to allow adjustment up and down and side to side.
9. With the handle bars at your desired height, stand in front of the bike facing reward. Holding the front wheel with your legs. Align the bars straight to the frame.
10. Tighten the stem bolt.
11. Sit on bike and double check that the handle bars are straight.

Next let’s get into the details of how high the handle bars should be and how to rotate the handle bars to make them a little more comfortable.

Illustrated definitions of the handle bar area of your mountain bike.

So let’s get into the detailed steps for adjusting the seat height.

Type of Handle Bar Stem Quill or Clamp

Quill Stems

Most Walmart bikes and lower price point bikes will have a quill stem.  The quill, is basically a wedge that locks down onto the INSIDE of the steering tube.  This type of system (stem and steering tube) will make it difficult to upgrade the front fork.

The quill is also prone to rusting in place.  Usually a liberal application of penetrating oil from the top and bottom will loosen any rust. 

Because Walmart bikes are not “sized” usually the size is just called out as large, medium and small.  The adjustments with the stem allow some fine tuning to find that comfortable riding position.

The nice thing is that a quill stem is adjustable, but with that adjustability comes a little bit of risk.  Remember my note above you should never raise the stem above the minimum mark.  The reason for this is to allow the quill to wedge into the steering tube without damaging the tube and still hold the handle bars safely.  No one wants the handle bars to come off in the middle of a ride.

A way to align the handle bars is with the tires straight to the frame.  Straddle the font wheel facing the rear of the bike.  Grip the bar ends and turn the bars square to the bike frame. See the picture below demostrating. 

A Little about Clamp / Threadless Stems

Threadless stems are a stronger and lighter handle bar system.  The stem and steering tube are combined which eliminates the extra joint formed by the quill.  For this reason if you’re looking to upgrade the front shock and fork on a quill stem your selection is going to be very limited.

Truth be told if your reading this with the idea of upgrading your Walmart bike front suspension, I’m really sorry.  I think there is only one after-market fork that is available to buy.  I’m not a heavy guy and this shock easily bottoms out.

My plan with my Walmart Mongoose is to make it into a comfortable cruiser / commuter.

Tools required for adjusting the Handlebars

• 6mm allen wrench for a quill stem
• 5mm allen wrench for threadless stem and brake levers.
• A light weigh hammer and piece of wood
• 14 mm wrench if you want to slide the seat forward or back.

Maintaining and Replacing Your Handlebar

It goes without saying – steering is important.  Maintaining the handle bars by keeping them clean, having good grips and making sure everything is tight is essential to maintaining CONTROL on the bike. 

Do not try to straighten handle bars by bending them back into position. If you crash and things get bent, the bar or the bar end is exposed, get replacement parts.

Adjusting the Handle Bars Front to Back

You can also adjust the handle bars front to back slightly.  This is done by loosening the bolt and clamp on the front of the stem.  Insert a 6mm allen wrench into the bolt head and turn until the handle bars roll freely.

Essentially you are rotating the handle bars, which in turn moves them slightly closer to the rider.  This “rotation” is only effective to a limited extent.  The geometry of the brake and shifter levers also changes as you roll the handle bars so those will need to be adjusted as well.

Be very careful if you rotate the handle bars.  Being able to squeeze your brakes handles quickly is critical to maintaining control of your bike.  This is a simple adjustment using a 5mm wrench.

Setting the Seat and Handle Bar Height

The seat and handle bar are two of the touch points that form the “comfort triangle” on your mountain bike.  The third touch point is the pedals.  The pedals and bottom bracket don’t adjust, so adjusting the handle bars and seat are usually related back the bottom bracket.

Setting the Seat Height

The correct seat height has your knees almost straight with your leg in the full down position.  If your adjusting the seat height for your young beginning rider, you may want the height somewhat lower to allow the child to touch the ground when stopped.  You can read more about adjusting the seat height in THIS POST. (link to another post)

Do not raise the seat so high that your knees lock straight during the pedal rotation.  This is unsafe.  Read more about seat adjustments in this article – How to adjust seat height.

Another factor in seating position is sliding the seat back and forth relative to the handle bars.  I talk about this in another post, but basically using a 14 mm wrench you can slide the seat back and forth along the seat rails.

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Learn more about Pedals, Handlebars and Brakes

• Handlebars on MTBs are wide, find out why – Why are MTB Handlebars so Wide?
• Should you upgrade your handlebars? Read – Are Handlebars Worth Upgrading?
• Universal pedals? Read all about it here – 9 Universal Pedals for Your MTB
• Learning how to Jump? Learn more with – How to Jump a MTB with Flat Pedals
• Keep your disc brakes clean – How to Clean Mountain Bike Disc Brakes
• Is their a difference? – Mountain Bike V-Brakes vs Disc

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Comfort and Arm Angle for Handle Bars

The handle bars should be at a height and easily reachable from the seat while riding.  A baseline position is having your arms slightly bent at the elbow (about 10 degrees) with you bottom on the seat. 

If you feel like your reaching to far or your shoulder and arms a seem to be holding you up, adjust the seat position on the seat rails

Mongoose mountain bikes are not designed for aggressive single track trails.  You should be riding in an upright position.  This allows you to keep your head up, looking clearly at the path ahead.  Don’t push yourself beyond your capabilities particularly on a Mongoose.  The front forks are for comfort and not jumps or steep down hills.  I know for me the front shocks bottom out easily riding over a sidewalk curb.