I have an 80mm RST CAPA ML suspension fork. it's not bad, but it has literally no small bump sensitivity. it's great for medium speed going over small-medium rocks, but I want to upgrade sometime soon. I'm looking at the RST deuce. I know that the extra 60mm of travel will void the warranty, but I only have like a year left anyway. I also know that it will change the geometry, but I was wondering just how much the geometry would change. the thing is that there's little to no sag when I lean on the CAPA without bouncing on it (stupid coil shock! XD) and I know that since the Deuce is air, there should be a fair amount of sag when I lean on it. I like the deuce because it's fairly cheap and most reviews of it are good. I can't afford like an 80mm reba that would actually fit my bike perfectly.
My question is this:What would change if/when I upgrade the fork, how much sag can I expect, and is it a good upgrade that would work??

I would only go up to a 100mm travel fork max if I were you. Might help out if you said what kind of frame you have. I think it is something like 1 degree per 20mm of travel, but the geometry change would be the least of your concerns. Adding so much travel is asking for frame failure if you are hitting anything of decent size.

altairX butted 6061 aluminum. what about 100-120mm? Because I want an air fork...any recommendations for a cheap air fork?

I believe OP has a Dawes (BD) bike.

There's no small-bump sensitivity because the Capa is most likely oversprung (something that, unfortunately, many RSTs suffer from). That's besides the fact, of course, that it's an undamped, entry-level fork. Not much help on the Deuce, as it seems to be a new model and I'm not even familiar with it. But 140 is a pretty radical change. I would keep it to not more than a 120mm fork. In general, 20-25mm in increased length slackens head angle by 1°, so 40mm could make it 2° slacker - - not a bad improvement many times. Your 80mm Capa probably has a 460mm axle-to-crown height. A-to-C is the true measurement of a fork; so if you want that much more travel, look for a fork that suits your needs with the least-radical increase in A-to-C length.

ok. there's a deuce 120mm...and the sag would bring it down to about 100mm. is that alright? are there any other entry level shocks? I'm really only familiar with rockshox and rst. I know marzocchi makes some decent shocks, what about the 22 rlo
my options-
Marzocchi-22 RLO-coil
Rockshox-Dart 2/Dart3/Tora
RST-F1st air, deuce air [cheap/entry level air shocks...however they may get me a better ride than a coil shock from rockshox]

Tora looks like the best out of those to me. A decent coil is usually more plush than air. The main benefit on an air fork is the weight reduction.

"OP" stands for original poster - that's you.

That aint the first question you should have. More like, how would that drastic change affect handling of the bike. You like chopper-like handling? Hella wonky handling? Go for it! Hell, it's your bike. Do as you wish. Who cares what others think. You'll be just like that home-less guy who rides a drop bar bike with the bars flipped up.

Save a little bit longer and get that 80mm Reba. Even a 100mm would be a better bet. 140mm is just to extreme a travel change.

Yeah, baby.

Is the Rockshox Tora TK more plush than a rockshox dart 2 or the Rst deuce? personally, I like the feel of air, but the tora would probably last longer. I'm probably not going to get a new fork until spring next year, too. Thanks for all of the help so far. Oh yeah...the tora=100mm, rst deuce=120mm, rockshox dart 2=80mm. 80mm is what I have on my bike, so would the tora still be worth the extra 60$ or so, even if it changes the geometry slightly? I also don't care too much about the weight...I weigh about 120 (therefore I'm not about to overload any of these shocks) and my bike just under 30.

yeah, i don't think I want "hella wonky handling" lol...which is better for the money/for me...rockshox tora trail tk [100mm] or rockshox dart 2 [80mm](not much better than what I have now, but at least it's the same travel....)

This is a great exchange. I see this question probably comes up fairly frequently, albeit in slightly different forms.

That "axle to crown" measurement is interesting........

My tapes do not have metric, but my "Axle to Crown" on my Tora was 17.25 inches, and "Axle to Crown" on the Fox Float is 19.25 inches.

I will go on record to say that this is TOO MUCH additional front-end travel. Steering is slowed down CONSIDERABLY, the front of the bike being raised makes it too light, and then you have the additional stress on the frame.

I am still working with my LBS to get an "semi-integrated" (or "zero stack") bearing in my head tube, but will then be looking to shorten the stroke of the Float. It will be a question of how much.