Bike type differences

[Wernervdmerwe]

Greetings,

 

 

 

I am not too familiar with the physics and science behind the different geometries. My question is how does the type of frame impact the ride?

 

 

 

I understand for example a downhill frame being stronger (therefor more heavy) and with a slacker head angle your center of gravity is more to the back, which makes perfect sense.

 

 

 

My question is more the differences between for example an all-mountain frame vs a trail frame or xc frame, when it comes to e.g. switchbacks etc?

 

 

 

So the finer changes, excluding climbing and bombing over bigger stuff and higher jumps if that makes sense...

[droo]

I'm not a complete expert, but here goes my 2c worth..

 

 

 

Steeper head angles make for sharper, more responsive steering, because the front wheel is more directly under the headset's pivot point. This makes it easier to tackle technical climbs. A slack head angle makes the front wheel want to 'flop' to one side when climbing, but when it points downhill it's way more stable.

 

 

 

Seat tube angle determines where your weight is over the bike, more than head angle. The slacker the angle, the further back your weight is, making slack angles better for DH/FR bikes. The trade-off is that your weight is not directly above the pedals, making for more effort to get maximum pedaling force.

 

 

 

A long top tube gives an 'arse up, head down' riding position, best for XC and roadies, because it stretches you out and puts your weight forward. Good for climbing, bad for descending. Short top tube makes you sit more upright, and thus keeps you weight back.

 

 

 

Short chainstays keep your weight directly over your back wheel, which helps traction on climbs. It also minimises flex and chain length, making pedalling more efficient. But if you make them too short, you lose out on mud clearance, and you can loop out (fall on your butt) when climbing steep or technical stuff.

 

 

 

The last bit is suspension. XC bikes tend to have the least, for more efficiency, then trail/AM bikes which are usually around 130mm with climbing friendly geometry, then DH and FR. Forks like the Fox Talas have adjustable travel, which changes the geometry of the bike for climbing and descending.

 

 

 

Hope this clears up a few questions, and (everyone else) feel free to correct me if I've made any glaring boxups

[Wernervdmerwe]

Thanks - very helpful. So a slacker head angle will count against you in technical climbing and switchbacks, but count for you in straight downhill trails...

 

 

 

Just want to make sure I am not gonna make a complete ass of myself when I go cycle with guys with other bikes - last thing I want to do is bring a hardtail on a ride where everyone rides AM bikes - leaving me in the sidelines

 

 

[droo]

That just depends how gonzo you are... got a mate who rides a full-on XC hardtail, and he keeps pace with guys on 5" trail bikes on the downhills - he just stacks more often!