I have a 2013 Trek 7.2FX (25" frame) with a 90mm long stem and a 10 degree rise.

The handlebars feel like they're too close to me, and I'm kicking around the idea of getting 110mm long stem with a 20 degree rise.

With a 72.5 degree headtube angle, the steering is very "twitchy" (sensitive) in stock trim.

My question is: will moving to a longer stem and a higher rise perceptibly effect the handling/feel of the bike? If so, what could I expect?

Thanks for your input!

A longer stem increases stability, but higher rise decreases stability. Pretty sure going from 90mm 10° to 110mm 20° would overall increase stability.

That works for me. Thanks Tyrion!

I went 10* up & forward 20mm with my road dropbar setup & gained a more reassuring directional feeling. Didn't change the "no hands" stability. The rake & tail length wasn't messed with.

^This is how it works^ The bike doesn't become more stable or less stable. The perception of stability or lack of changes.

For Troul & CXWrench, that will be fine with me. The stability is more ancillary to my main objective, and that is I'd like to move the handlebars a little further forward.

Now, does anybody know if this would necessitate all new cables?

The "twitchiness" of your bike with a 72.5 head angle is meaningless without posting the rake of the fork.
Concerning requiring new cables, you won't know until you try the switch. My guess is you won't have to change cables.

Bear in mind that an increase in stem height or angle will reduce reach. With the set up you're considering reach will only increase 8mm and the bars will be 25mm higher. (Provided stem insertion height doesn't change)

You're not going to see a big change in anything with that switch. Someone gave numbers, you are moving the bars up more than out, little more upright position, some added knee clearance.

Stems can be pretty cheap. Not a bad idea to have a pile of extras for experiments.

On one road bike with drop bar I have swapped back n forth between a 80 and 100 mm stem. I cant honestly say steering is affected, its a bit twitchy no matter, - but the fit of the bike does change noticeably. Id say getting the fit right far outweigh the minor (or non existent) impact on steering.

This doesn't answer the OP's question about twitchiness but this comparison chart will show what the difference between the two stems would look like if the stem were mounted at the same height. You can plug in any measurements you want. Stem Comparison Tool | yojimg.net

How could we know? We haven't seen your bike. If I had to guess I'd say no.

72.5 degrees isn't anything too crazy. Like someone else mentioned, most likely has more to do with fork rake.

Stems have a profound effect on the way your bike handles. Ones which may look similar in design can each offer dramatically different handling. If yours is a crappy stock one, upgrading will be worthwhile. I think 110mm might be too long unless you like the stretched out position. Maybe try installing a stem riser first and see how that changes the feel.

Please...explain. Given that the trail isn't going to change, no frame angles are going to change...tell me how this works. Think about it first.

...the changes you have listed won't change much, (in my experience). Personally, I do find that getting a longer stem and better overall fit on a straight up quill stem road bike usually helps me to redistribute my weight a little better over the wheels, and I do notice that. I don't have a whole lot off personal experience with changing stem angle by 10*, but in the one or two instances I've done it, again I noticed little other than better anatomical fit, and better weight distribution.

A stem that is too short will tend to make you ride more upright, so you have a tendency to put more weight over the rear wheel.

FWIW, you can also fool around with saddle position fore and aft, and see if that helps or not. The whole thing off finding proper fit for you is a process, and you might need an even longer stem for optimal results. Once you have something that feels right for you, measure the distance from saddle (at the post) to centerline of the bar. Then measure saddle height at the top down to pedal contact surface. Those are the numbers you need to set up another bike at the start when you are figuring it out at the beginning.

The numbers are different depending on the purpose for the bike (racing, touring, around town and more upright, etc.)

...as stated above, other than the effects from repositioning your body and weight on the bike, I have not personally found that to be the case. I could be wrong.

Have you tried using different stems before?

I'm guessing it says 'junior member' because you're young. Yes, I have. I've raced bikes for over 40 years. I've been a pro team mechanic and a shop mechanic for 25 years. I've worked with some of the best bicycle fitters in the world. I know of what I speak.

I switched a drop bar road bike to bullhorns, ones that angled out and up a good way. I agree with everyone that the bike stability is unaffected, but with my hands a good half foot (or more) farther out, the bike's response to handle bar input changed dramatically. One inattentive twitch of the bars practically puts the bike down.

This is on a bike I've ridden for over 30 years.

Recumbent riders call this the tiller effect

Sort of becomes a semantic argument about what one means by the word "handling". Getting your grip points farther out from the headset unquestionably affects the bikes response. Is that handling?

I'm not questioning your experience in any way, but I've dealt with stems which seemingly look similar to one another, but felt completely different in response.

to answer your question, they are often cast slightly different with different thicknesses of aluminum used.

I think this is just a matter of semantics. Different stems won't change the fundamental, or inherent, stability of the bike. This is observed and demonstrated with no-hands riding. The length of the stem or, indeed, no stem at all, won't change the geometry and stability of the bike as a machine. However, different stems lengths can change dramatically how the bike feels, how the bike responds when you provide inputs to the bar or grips, and perceived stability. I think we're all taking the same thing, just using different words.

Re stem length and twitchiness--lets be honest here, what one rider may find twitchy and nerve wracking to one rider may be nothing at all to another rider.
internet blah blah by any of us will never know how this bike is.

if the person still feels their bike is twitchy, going to wider heavier tires could help them feel more comfortable.

I have a drop bar bike with a 50mm stem and it's fine for me, but this is specific to this bike. My most twitchy bike is a 700c hybrid with hardly any toe strike with 35s and fenders, and was twitchy with 40s also. An old hybrid.
My older dropbar cross bike to me is perfectly stable at any speed up to 80k, but is probably my best no hands bike--yet a friend once rode it and didn't like it because it was too twitchy for him.

You said 'dramatically different handling' and I asked for an explanation. Please, explain. This is not the same as what you're now talking about with 'different response'.

Tiller effect is slightly different than what you're describing. The tiller effect is due the bars rotating around the fork axis, not the center axis of the bars. As the stem gets longer, your hands don't move in a circle.
The MTB community is increasingly going to very wide bars with the shortest possible stem to provide stability at both high and low speed.

Longer stems are generally better for stability, but narrow bars and weight forward are much worse. That's why TT bikes are notoriously twitchy. Small left/right weight shifts cause steering inputs, with a wider bar, those are decoupled.

The handling characteristics are still based on geometry of the bike. From my experience...Transition Scout and Specialized SJ. Same bar width, same stem. The Scout is very twitch and easily put off line by rocks and roots...at my climbing speed. The SJ is much easier to control and I don't over compensate as I'm clumsily bouncing off of every rock within reach. Same on slower technical descents. The Scout seems to come into it's own as the speed goes up but the SJ is still more comfortable for me to ride. The Scout is a longer travel bike and intended to be ridden hard, I guess. But seeing as the bar and stem are the same it's got to be the geometry of the bikes, and maybe a little bit the wheel size difference?