The organisers of the International Rally of the Lakes, taking place this weekend in Killarney, Co Kerry, have described the absence of Mike Gaine from this year's event as a dark shadow.
Mr Gaine, who has been missing from his home in Kenmare for more than six weeks, is a former participant in the rally.
Cars in this year's event are carrying his image with an appeal for information about him.
The May bank holiday weekend has been synonymous with the Rally of the Lakes in Killarney for almost 50 years.
This year, 170 cars from across Ireland, Britain and elsewhere went to the start line, many of them carrying images of Mike Gaine with appeals for information about his whereabouts.
Rally organisers say they wanted to show their solidarity with Mike Gaine's family.
"It's definitely a dark shadow, and the campaign now is to bring Mike home," rally organiser and Chairman of Killarney and District Motor Club, Tommy Randles, told RTÉ News.
Tommy Randles lives in Kenmare and is a friend of Mike Gaine.
"He was a cool character, never got too excited, a deep thinker that would steady things," he said.
"He read a lot and he had an interesting view on a lot of thinkgs."
In a practical way, Killarney and District Motor Club has printed 6,500 programmes for this weekend's rally and their appeal and Mike Gaine's story takes up a page in that programme.
"For his family not knowing, that there is no conclusion is the real factor to this, it's devastating," said Rally of the Lakes Clerk of the Course, Dermot Healy.
"His sister, Catherine, I would know pretty well because she's living in Killarney for many years, his other sister and his wife: it's absoutely devastating for the whole family."
Many of those taking part in this year's event participated in the rally previously with Mike Gaine, either as his driver or as his navigator.
Brian Hickey from Kenmare, one of the local drivers is this year's event, described being navigator for Mike Gaine during the Rally of the Lakes as "an experience".
He said their participation one year came to an end when one of the back wheels came off their car and passed them out.
"Mike asked: what's that!" Brian Hickey recalled.
"Mike was a gentleman," he added.
"He had a heart of gold. Rallying was a passion as well as his farming. He was very good to us, we were very good to him and we had a great friendship, you know.
"There's five of us hung around together and the way I can only describe it to you is that one of our digits is missing."
Another one of those five, Adrian Randles from Kenmare, described Mike Gaine as a great support to all of them.
"He had a fierce knowledge of what went on in the history of rallying," Adrian Randles said.
"Stuff we will never again hear, Mike had it."
Mr Gaine was last seen in Kenmare on the morning of 20 March, where he purchased phone credit in the local Centra shop.
His bronze-coloured Toyota RAV4 was found in his farmyard the following day. There were a number of personal items in the car.
Detectives at the incident room in Killarney continue to work on the case this weekend.
The re-classification of the investigation into Mike Gaine's disappearance mid-week means the investigation team based at Killarney Garda Station has now been expanded with the addition of several more detectives.
There is a change in the type of resources being deployed to the investigation, but there is no change in the scale of the effort to establish exactly what happened.
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