Not sure what a flange is, but you need to remove the 17mm hex nuts to remove each wheel, if the wheel remains stuck to the hex, then chances are you may have rounded out the hex on the wheel... this can happen if you did not use any thread lock on your nuts and they make have slowly worked loose creating wobble and melting the plastic from the wheel.
FFI... RTR = Ready To Reassemble
That means you need to rebuild the entire car, such as applying grease on all rubber seals to prevent leaky shocks/diffs and most importantly you need to apply thread lock on all metal to metal fasteners.