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Characteristics of the following bars for MTB are:
• 780mm wide
• 30mm rise
• 5˚ up-sweep
• 7˚ back-sweep
I know what effects do the width and rise have on the feel and riding. But what about upsweep and backsweep?
For the last 2 years I've been using bars with 3x9 sweep (compared to the above's 5x7). What difference would it make?
From my experience upsweep make you pull easier for drops, manuals and bunny hops, but the other side of the medal is shoulder width. The wider your shoulders, the less comfortable will be upsweeped bars (you will feel your hands bent outwards). In fact when chosing BMX bars every degree of upsweep considered as something about a quoter inch of rise (from the ease of pulling perspective).
Not sure if my math is correct here, but using a triangle solver, and assuming that the up-sweep and backsweep act over a distance of 250 mm, (390 is half the bar, minus a bit for the middle part) the difference between 3 degrees and 5 degrees for the upsweep translates to 9 mm difference in rise, and the different between 7 degrees and 9 degrees for backsweep also translates to 9 mm difference (same difference in angles). Since the backsweep is less on the new bars your reach will be 9 mm longer, and the upsweep is higher on the new bars so the bars will be 9 mm higher. How this affects your ride I cannot say. Probably won't make a whole lot of difference, since the longer reach will be cancelled out a bit by the higher bars.
Just one thing to add is that with more backsweep you use your Latissimus dorsi muscles more (lats) this can be good for your core strength, your shoulders are more naturally positioned, and lastly it is more natural/comfort for your wrists too.
Once you go "too far" you'll loose out on some control/performance on tricky descents.
Rotating your bars for more upsweep coupled with the risewill give better control/performance on dencents as it brings your ballance point backwards on the bike. 30-40mm rise is good going down. But not so much going up.
Everyone is different of course, and it depends on stem length and angle too
