i recently got a 1989 ibanez rg570. i belive the string guage is 9-42, cuz it feels way to thin. what do you think is the highest guage the neck could stand?

Assuming you're in standard, 10-46 should be plenty tight. After that if it's still to loose for you either get a heavier set (eg 11-49) or if it's just the bass strings you want tighter get a light tops-heavy bottoms set.

11-49 sets are called medium, I would doubt a set called 'medium' would be too much for a neck. Just turn the truss rod a bit and away you go!

oh ok. i guess 10-59 would be too much...

That would be a 7-string set. Or a custom 6-string set with a really weird balance between the wound and unwound strings.

The idea that a certain set would be "too much" is a little vague. In D-standard tuning (down a full step), a set of 11s would be perfectly fine and will probably be around the same overall tension as 10s. The lower you tune, the larger gauge strings you can use without actually increasing the tension at all. Add too much tension, and you'll have problems getting your trem set up correctly. Finally, your strings will fail from too much tension long before the neck will, so I wouldn't worry it from that point of view.

I know guys who run 11s just fine. Personally I have 10's on my wizards, but I tune down a half.

i mean THAT on standardtuning.

Zakk Wylde uses I believe 10-60, in drop d, so That should be fine. I'd be more worried about the string breaking at that kind of tension anyways. Not to mention the nut might not even be big enough to handle the A and E strings.

The trussrod is the thing that hold the neck together, not the thickness of the wood of the neck. I've heard a lot more stories of Gibson Les Paul necks breaking than Ibanez wizard necks.

The strength of a neck is in the wood, and style of construction. Gibson necks break a certain way because of how they are made.

A thicker neck is going to be stronger than a thinner neck period.

The truss rod is there to prevent the neck from curling up under the string tension.

0.11 - 0.54 on my S540, nothing to worry about.

If you're using 9s then you should just go up one gauge to 10s and see how that feels first. Check out the difference in overall tension between 9s, 10s and 11s on your guitar:

9s = 85.1 lbs. of tension
10s = 103.6 lbs. (22% higher tension than 9s)
11s = 118.6 lbs. (39% higher tension than 9s)

Actually, a set of 11s tuned down a whole step will be lower in tension than a set of 10s at standard tuning. correct. If you go up a gauge, then detuning all the strings by 1/2 step is much closer in overall tension to the lighter gauge at standard tuning.

10s standard tuning = 103.6 lbs.
11s at 1/2 step down = 105.7 lbs.
11s whole step down = 94.1 lbs.

You may need to add an extra spring to your trem to counteract the tension and still get the trem set correctly. I run 10-46 on my RG3120 in standard tuning with an extra spring on the trem. That neck is hands down the most stable with temperature/humidity fluctuations of all my guitars.

k thanks