Can tiller be changed from more on top less on bottom .and vise versa. I have heard you can twist up or down but doesn't that change your brace height then ?

Unless you have an ILF bow the only way to change tiller is by reducing weight on one limb more than the other.  Generally not a DIY project,  and not something I would suggest unless you were having the bow completely refinished anyway.

Twisting the string changes just the brace height and will affect tiller on both limbs pretty much equally. If you are trying to shoot 3 under on a bow tillered for split (or vice versa) you can make it work fine by  adjusting your string nock.

What whip said

Yup, you can do it, but it will forever change the bow and not necessarily for the better.  Listen to Whip, he knows.

Chuckc

If its a three piece bow you can simply grind a thin wedge and put under the limb and change tiller that way without harming the bow .

You can try different thicknesses of shims  in the bow first and then make the final product to the thickness of the shim down  to zero in the back./ ,  You can then drill the holes and even glue it on the limb if you would rather have it there instead of the riser. I would use just a dab of glue though so you can take it off if you decide you don't like it.

God bless, Steve

Like Steve pointed out it can be done pretty simple on a TD bow....I wouldn't attempt it on a one piece though...

But.....Why do you want to change the tiller?

Yup, you just take the loop off the nock on the limb you want to increase the tiller on and twist up that end of the string more.  <

Them bowyers is pretty cagey.  Wouldn't have thought of that.

I guess,I don't follow on twisting one end to change tiller.
The effect is that the string is shorter. Should just give you a higher or lower brace height.

I adjust my longbow all the time by twisting one end.