Changing space for searchform on Twenty Eleven

Please add below css code on style.css. It may work for you.

input[type="submit"] {
    width: 137px;
    height: 36px;
    margin-bottom: -3px;
    margin-top: 7px;
}

Thanks

Paste this code on your style.css

#branding .with-image #searchform {
max-width: 325px;
}

#branding .with-image #searchform {
max-width: 325px;
}

This worked. With thanks!