As per this, the max size is 150cm. If I include the wheels it comes to 154cm worst case. Can they allow this without penalty?
Emirates has both weight and piece concept and, at 154cm, your checked bag is still under the maximum allowed dimensions, although you might have to pay an additional fee (added emphasis mine).
If you’re travelling to or from Canada, North America, Central America or South America, or you’re travelling from Africa, you’ll need to follow the rules of the piece concept.
This determines how many pieces you can travel with, and the maximum weight and dimensions of your pieces of luggage.
The total dimensions (length + width + height) of each piece must not exceed 150cm (59 inches). You’ll be charged an additional fee for any individual items exceeding dimensions of 150cm (59 inches), up to a maximum of 300cm (118 inches). If an individual item has total dimensions greater than 300cm (118 inches), it can’t be checked in as baggage and will need to be sent as cargo or freight.