Originally Posted by
cyccommute
You've got it backwards. Modern frames designed for suspension have slacker head angles than older nonsuspension bikes. The longer the travel of the fork that the bike is designed for, the slacker the head angle. This makes sense since the head angle changes as the fork compresses. Bikes from around 1990 had head angles of 71 to 73 degrees (depending on brand) while most modern suspension frames have head angles around 70 degrees. A rigid mountain bike with a 71 degree head angle is a handful to ride off-road. A steep angle puts you over the bars on downhills...scary...and but it centers you over the bike on climbs making them very a little easier. It takes a lot of finesse to ride a steep angled bike
The first generation mountain bikes (about 1983) had 69 degree head angles but you don't want to ride one of them. They are superbly stable on downhills but they are terrible to climb on.
"Suspension corrected" is usually used to refer to a rigid fork. The blades are a little longer so that the head angle isn't too steep when installed.
Yes, I would have had it backwards if I was referring to post 1990 rigids vs. a modern FR bike. But I wasn't. Perhaps I should have communicated more clearly - I guess I assumed that "classic" mountain bike (esp in the context of the OP) universally referred to '80s bikes, like original Stumpy's, MB-1's and so forth. Of course, that was my first mistake (you know, assuming).
Anywhoo, I should have qualified my post with the context: 80-100mm travel "corrected" 29ers, which are commonly running 72 degree angles in the medium to large frames. I've seen some in the 73 range. Freeride and DH bikes with big travel are definitely running slacker angles.
That said, there does seem to be a trend towards slacker head angles on SS rigid setups and the 80/100 frames, and many are now starting to see more fork offset (50-55mm rather than 43-45mm) as well to keep handling (and climbing, as you mention) in balance with the slacker angle. Jeff Jones embodies this approach with his frames, and others are beginning to follow suit - whether or not intentionally - I think there is enough interest in full rigid that frames are now beginning to cater to the "rigid-centric" design, with 69-70.5 HT and 72-72.5 seat, 55mm fork offset, and no room for a squishy fork.
