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I recently bought a bmx and after doing a few tricks on it, the front-load stem became loose enough for the bars to slide forward (they rotated towards me about the point the bars were connecting at the stem.)

After tightening every bolt on the stem and adjusting the bars upright, I encountered the same problem after a few more tricks.

I was looking into buying a new stem and wanted to know what the major differences were between a front-load stem and a top-load stem.

Image of a Front-Load stem

Image of a Top-Load stem

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Sounds like you're more concerned with durability and reliability than performance. –  Neil Fein Sep 27 '11 at 10:27

2 Answers 2

up vote 5 down vote accepted

There should be no difference, other than the quality of the materials and workmanship. One can clamp just as tightly as the other, and both will be apt to produce the same symptoms if the bar is slightly undersized or too flimsy at the mount point. In both cases, if you do have a slightly-undersized bar you want to keep you can grind down the faces of the clamp a hair (though it would tend to deface the upper unit more).

I suspect the main difference between the above units is weight and "sex appeal" -- the upper unit appears likely to be a few grams lighter, and it's that cool black color.

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Just t o add to DH's comment it is also important to tighten the bolts evenly. Iwould suggest a crossing pattern (top left then bottom right etc.) increasing the torque gradually over four or five rotations until the correct torque is achieved. The top load stem also appears to have a larger clamping surface which in theory would make it grip tighter. –  user2486 Sep 27 '11 at 13:22
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Clamp surface size may be good or bad, depending. A smaller surface allows the clamp, for a given bolt torque, to place more pressure on the bar, deforming it to a degree, and increasing the "bite". But if the bar deforms too easily then you want to spread the pressure out over a wider area. Also, the hardness of the metal in the stem used may make a difference in clamping effectiveness -- softer metal will have less "bite" on a smooth surface, but may actually work better on a knurled bar surface. So, "It all depends." –  Daniel R Hicks Sep 27 '11 at 16:03

The main difference between front-load and top-load stems is the stack height. Top loads will usually have a greater stack height. This would allow you to remove spacers or increase the height of your existing bars.

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