from Rookie’s keyboard
Hello, friends
The other day, a guy with some beaten Trek hardtail came to the shop with a request to replace his stem with a “cool BMX model”. When I asked why, he looked at me as if I’d been stealing his lunch money for a decade.
What’s the issue?
Personally. I consider this mod “semi-pointless” even though it’s 100% possible.
But let’s imagine for a second than it wasn’t and analyze what it would take to install “a cool stem”.
A BMX stem could fit on an MTB only when the following criteria are met:
1. The clamp of the stem must match the diameter of the handlebars.
BMX stems have a 22.2 bar clamp. That’s too thin for common MTB handlebars which have а 31.8mm clamp-on diameter.
Therefore, only MTB bars with a 22.2mm clamp area would work with a classic BMX stem.
The common MTB handlebars sizes are different, however.
25,4mm, 31.8mm, and 35mm bars dominate. The available 22.2mm options are limited.
It’s also worth noting that most 22.2mm MTB bars are made of Chromoly steel which greatly increases the weight of the bar.
An average 22.2mm steel MTB bar weighs between 500 and 700 grams whereas a 31.8mm aluminum one is 300-400 grams.
22.2mm MTB bars are made out of steel because the diameter is too small to produce a strong bar out of aluminum.
Aluminum isn’t as dense as steel and nees more volume to match the strength of a steel component. Hence aluminum frames have much larger tubes than steel ones.
Here’s a list of 22.2mm bars that would work with a BMX stem:
| Bar | Material | Crossbar | Weight |
| NS District | Chromoly Steel | No | 550 grams |
| DMR Wingbar | Chromoly Steel | Yes | 700 grams |
| Nemesis Project | Chromoly Steel | No | 655 grams |
| Gusset 3″ Open Prison 750 Bars | Chromoly Steel | No | 580 grams |
| Gusset 2″ Open Prison 750 Bars | Chromoly Steel | No | 560 grams |
| CTN Eastwood Bar | Chromoly Steel | No | 590 grams |
| Atomlab GI Riser Bar | Chromoly Steel | No | 590 grams |
| Renthal Jump Bar | 7010 T6 Aluminium Alloy | No | 380 grams |
| Black Market Molly Hatchet Bars | Chromoly Steel | No | 455 grams |
| Dartmoor Toxic v.2 | Chromoly Steel | No | 415 grams |
| Fireeye FIRE BAR | Chromoly Steel | Yes | 790 grams |
| Surly Sunrise | Chromoly Steel | Yes | 778 grams |
| Norther Cycles Custom Steel Sweepy Riser Bar | Chromoly Steel | No | 485 grams |
| Fairdale MX 28″ Handlebar | Chromoly Steel | Yes | 453 grams |
| Dobermann Bikes | Chromoly Steel | No | 645 grams |
| Average: | 575 grams | 20.28 oz |
2. The stem’s fork-clamp diameter should match the diameter of the fork’s steerer tube.
Modern MTB bikes have suspension forks with a steerer that’s either 1 1/8″ from top to bottom or tapers from 1 1/8″ to 1 1/2″.
А standard BMX stem would work because it has a fork clamp diameter of 1 1/8″.
Questionable Benefits
Looks
Let’s get real, fellas. The primary motivation for installing a BMX stem on an MTB is appearance rather than function.
Many people like the design of BMX stems and install them on their MTBs for style points.
Compatible with BMX Bars
And another obvious benefit is that BMX stems work with BMX bars. (Most MTB stems don’t). So, if you want to make an MTB->BMX bar conversion, you can use a BMX stem.
1. Limited Bar Choice
A BMX stem restricts you to 22.2mm bars. And while there’s a decent number of them on the market, the volume is nowhere near close to that of dedicated 25.4mm and 31.8mm MTB bars.
2. Heavy Bars
Most 22.2mm are made of Chromoly and some have a crossbar/brace for extra support.
Thе combo results in bars that are substantially heavier than MTB models made out of aluminum.
Larger clamp areas (25.4mm, 31.8mm and 35mm) allow designers to use hollower tubing and lighter materials such as aluminum while still achieving a satisfactory level of strength.
The larger the tube, the hollower it can be without losing strength because most of a pipe/tube’s strength comes from its outer layers.
For that reason, a pipe is stronger than a solid rod of equal mass when both are made of the same material.
Bicycle engineers have been relying on this phenomenon to produce components with excellent strength to weight ratio.
The most obvious example would be bike frames – they’re all composed of tubes.
The table below contains the weight of popular MTB bars with common diameters:
| Model | Weight |
| Renthal Fatbar® 35 | 305g |
| LEVELNINE Team 35 | 326g |
| Truvativ Hussefelt Comp | 347g |
| Race Face Atlas 35 | 320g |
| SQlab 3OX MTB 31.8 | 325g |
| PRO FRS 31.8 40 mm Riser | 345g |
| Spank Spike 800 Race | 330g |
| Chromag Fubars FU40 | 330g |
| Ritchey Trail 2X 31.8 | 276g |
| Ritchey Comp Kyote | 355g |
| Average: | 325.9g/11.49oz |
The average weight of regular MTB bars is 325g. Meanwhile, the average weight of 22.2mm MTB bars is 575g (table 1).
The difference is 250grams – a lot of weight in the world cycling.
3. Heavier Stems
Short MTB stems are notably lighter because the design requires less material.
BMX Stems
| Model | Weight |
| Sunday Freeze | 298g |
| Odyssey Nord | 354g |
| BSD Dropped | 320g |
| United Purge | 382g |
| Fit High Top V2 | 344g |
| BSD Levelled | 320g |
| Cinema Martinez | 286g |
| Animal Inverse Stem | 382g |
| Profile Acoustic | 272g |
| Fly Volcano 2 | 281g |
| Average: | 323.9g/11.393oz |
MTB Stems
| Model | Weight |
| Thomson Elite X4 Stem | 165g |
| Renthal Apex Stem | 146g |
| NEWMEN Evolution 318.4 | 167g |
| LEVELNINE Team AM Stealth 35 Stem | 135g |
| Hope FR/AM 31.8 | 134g |
| Syntace MegaForce3 | 97g |
| Race Face Chester 35 Stem | 170g |
| Race Face Turbine 35 | 150g |
| Chromag HIFI V2 | 200g |
| Chromag BZA 35 Stem | 165g |
| Average: | 152.9g/5.39oz |
Conclusion: On average, MTB stems are two times lighter (323.9g vs 152.9g).
Strength
It depends on the model. In general, both MTB and BMX stems are plenty strong to handle a lot of abuse as long as the production quality is good.
And since some of you may be wondering, my customer gave up on the idea after he realized that new bars will be needed.
Anyway, thank you for stopping by.
Until next time,
Rookie
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