The question is up for debate. Personally I would answer that there are enough elite riders who don't have a competitive background on dirt to say "Yes". But from watching my local club racers (whilst racing with them) those that started young on dirt and successfully competed were and are the standout guys on bitumen. I think personally I would have been a much better racer had I started off-road. I didn't take to trail riding until relatively late in my amateur racing career. And the looseness of a bike underneath you when new to it is a shock - a whole other set of skills to road racing obviously. And I think it follows that being able to capably control and harness an off road bike with it moving around unpredictably every second beneath you gives you a gift in transitioning to tarmac. I have witnessed guys who raced dirt from 5-15yo transition to road racing like ducks to water. They are at home so quickly on a race 600cc bike and I think are more adaptable to a bike that might not have a great set-up. On top of that their bike control is attuned to unpredictability every second on dirt and it translates to instinctive inputs constantly when on bitumen. Anyway, just my humble opinion. (And yes I have endeavoured over years now to become a half decent offroad rider (to improve my racing)) ... with very little success. In fact I suck on the dirt.
I think you only need to look at some of the absolute top tarmac riders in the world and what their training regime includes, to come to the conclusion that the answer to your question is yes. I would add however, an early background in off road riding doesn’t preclude you from becoming a good tarmac racer. A natural talent goes a long way. Andy
Dirt gives early understanding of rear steering and the mechanics of how bikes work in a relatively slow and soft(er) environment but imho it’s not essential
Due to low grip, how one is pushing the tyres in the ground by the means of positioning/transitioning from the inside to outside foot peg is extremely important when braking, cornering, accelerating. Basically, most of the steering if done with the foot pegs. It is very possible after couple of years off-road, some develop an extra sense on when the bike is near the limit, based on feedback from the foot pegs. As android853sp wrote, there is a reason many pro-racers are training on low grip terrain.
Aged 63 I have just started Supermoto, sort of dirt, but on tarmac. The drills force you to brake very hard and late, turn and gas out. The real skill is in the braking. It’s a very different line on a hairpin like T5 at Portimao. The front wheel is more upright, the rear hanging out to the side. That means way more weight and pressure can be on the front tyre because it is upright, not on it’s edge. The rear is out to the side, so the turn is completed faster and gas can be applied earlier than the normal style that has to wait and run wider. Just watch a slo-mo of a MotoGP rider. I am learning to do this technique in Spain. Will take it to the track in May.
My Son goes here for the Winter race series and isn’t at all nervous of a bike moving around under him. He’s been going a number of years now after taking a level 1 then2 course. https://www.flattrackschool.co.uk/
There was an interview with Ron Haslam in a recent magazine and here are some of his quotes when talking about Freddie Spencer: "He didn't have to think to do anything - he could just ride whatever was in front of him. He didn't have braking or turn-in points - he just looked at the corner & rode it. He went to Assen having never seen the track before.. didn't practice on the Friday, went out on the Saturday and having no set up time broke the lap record on his third lap. That's a lot of ability." "His knack of sliding the front tyre into corners was his biggest skill. It's where the line between crashing & not is very narrow but that fact was never in his head. For him it was natural to half lock the front brake and feel it slide - if that happened to the rest of us we'd be wooo we got away with that. He had such good feel no one could get near him" "We were on a test day and the only two on a clean track and I noticed little black lines appearing going into the corners - all the way to the apex. And it wasn't just one line it was everywhere lap after lap. Incredible. I could do it but my confidence wasn't at his level. I was comfortable spinning the rear & braking very hard but sliding in... I couldn't get the feeling out of the brake to feel confident to do it on every corner"
Off road riding skills can keep you alive when things go tits up on the road, I would recommend all young , would be motorcyclists to learn on dirt from an early age.
We went to Cyprus on a family holiday when I was 15 and it was the first time I was properly allowed to “do my own thing”. Hired a moped and spent two weeks terroring around the dirt tracks across the island on it lol. I’m still shit on tarmac though, so what happened lol
Here is their website https://www.supermotoland.com/ there is also Rocco Ranch in Spain, not to be confused with Rossi Ranch…. https://roccosranch.es/?