The grey car collided with a red Honda CBR 650 on the northbound carriageway at the junction with the M25 at 5.35pm on May 20.
It left the biker with a broken pelvis.
Police have now released a picture of the car involved and are appealing to the public for help finding it.
An Essex Police spoksperson said: “Officers investigating a collision on the M11 where a motorbike rider with a broken pelvis are now in a position to issue an image showing a vehicle we want to identify.
“We have been carrying out enquiries since the incident at 5.35pm on Tuesday 20 May.
“A grey car and a red Honda CBR 650 motorbike were in collision on the northbound carriageway at the junction with the M25.
“The rider of the motorbike sustained a broken pelvis.
“We are looking to identify the grey vehicle and are now able to issue a photo showing the car itself.
“We appreciate the image is not great quality and from a distance away but someone has sustained serious injuries so we are doing all we can do locate the car.
“If you have any information, CCTV, dash cam or other footage in relation to this incident, then please get in contact with us.
“Please quote incident 882 of 20 May.
“You can let us know by submitting a report on our website or by using our online Live Chat service which is available 24 hours-a-day, seven days-a-week.”
“Visit www.essex.police.uk/digital101 to find out more about our online reporting services.
“If you would like to make an anonymous report you can contact independent charity Crimestoppers, by visiting their website or by calling 0800 555 111.”
