Let's say you have a full susser frame designed for 4 inches of travel front and back. That's
100mm in new money. If you stick a pair of MTB wheels and chunkies on it, you'll find that
your bottom bracket is a certain distance from the floor, let's say 13 inches as a rough
starter.
Now then, common best practice is that you get what you pay for, end of story. However,
there's absolutely nothing but money stopping you from playing around here and trying
some different ideas. Easiest and most common desire is to change front forks, so we'll
look at a couple of examples of this, either way, up or down.
If you tear off your old Marzocchi MX Comps, for instance, and substitute a pair of Z1 Drop Off
130s, you gain 30 millimetres, or 1.25 inches of height at the front of the bike.
Now then, common wisdom, or "expert opinion", like what you get from your
MBUK/MBR/WhatMTB magazines will say you've totally bu**erred up the handling of the
bike now. Well, in Gollum's World, that's Utta Bollox. What you have done is slightly
increased the head angle of the frame to the ground, making the bike a wee bit longer. It
has also lifted your bottom bracket a wee bit, making the bike a wee bit higher.

First, let's look at what harm you could have done:

1) Bottom bracket up = higher Centre of Gravity = less stability
2) Longer bike = harder to turn quickly = loss of steering sensitivity
3) Front suspension no longer matched to rear = worse handling and bump response
4) Higher bike = harder to get your leg over (I'm waiting...)

Now, let's take a different, slightly more positive view:

1) Bottom bracket up = more ground clearance
2) Longer bike = more stability, especially on tarmac downhills with the Reivers
3) Front suspension gives you another inch before it hits capital T
4) Higher bike = lower seatpost = almost back to normal
AND
5) Longer forks = more sag available = smoother, better ride on the rough stuff
6) Your bike looks meaner with an upright stance at the front (it all counts)
7) It's your bike, you'll do what the huck you like with it

Now let's go the other way, and fit 80mm Rockshox Reba Race forks, bad:

1) Front end and bottom bracket down = falling sensation as you ride = less stability
2) Shorter bike = twitchy handling = increase in steering sensitivity
3) Front suspension no longer matched to rear = worse handling and bump response
4) Lower bike = higher seatpost = same as (1)
5) Less travel = harsher ride
6) Lower front end - it's a bit harder to wheelie the thing now

And again the Golly View:

1) Bottom bracket down = lower centre of gravity = more stability
2) Shorter bike = quicker steering and it'll fit under the stairs now
3) Less front suspension  = firmer and more precise handling
4) Lower bike = quicker round the turns
5) Less travel = more ground feedback
6) Lower front end - climbs like a whippet now
AND
7) Your bike looks racier with a dipping cockpit
8) You've got cushier back suspension than a 3 inch (75 - 80mm) rig and an extra inch of sag
9) Shorter forks = a lighter bike, especially with Rebas
0) It's your bike, dee daa dee daa

CONCLUSION

We're ALL different. No one bike feels the same to any two riders. Some people ride perched well forward all the time. Either because they feel safer that way, or they don't know any better, or they don't know you can get stems shorter than six inches. To these people, an extra inch of front travel would hardly be noticed because they're compressing most of it away by sitting or leaning forward. Also, suspension these days is so adjustable that you can get a similar effect just by tweaking the settings at both ends. If you ride with your seatpost almost out of the frame you have no feeling for suspension tuning anyway, and most people do, or at least the Cross Country Brigade. They may as well be on a
Penny Farthing, whatever that is, or a Pogo Stick, whoever she is.

Question One: What goes faster round corners, is it

a) a Pantechnicon

or

b) a Ferrari Formula1 car?

Question Two: Why?

If you have a consistent riding style and not too much fear of getting hurt you can train yourself to keep the front end light on the rough stuff but give your forks loads of sag, anywhere up to 50%, and still have full travel available for the bigger knocks by riding with them fully extended and keeping your weight well back. This is a technique I use on both my bikes and it usually gives me enough of an edge to pass most people I ride with on chunky ground, up or down, when they slow down for the dodgy stuff (although I'm dead slow otherwise).

And finally, most people would hardly notice the change of a few millimetres here or there. Be brave. Test yourself. Experiment. Don't believe everything you read, especially this parcel.

***add-on! Looks like someone at What Mountain Bike (June 07 Edition - bike setup) must have read this and at last there's a bit of sense being shown about different riders with different styles, weights  and sizes related to frame angles/fork travel etc!

Have you Killed A BIKE THIEF TODAY?