Jaybird180 Posted November 7, 2017 Report Share Posted November 7, 2017 I'm having a good time riding my new dirt bike. It's a first for me being on such a machine and I'm finding a lot of similarities to hard surface riding. I have a quick question from watching some motocross and hope someone can answer about some of the dissimilar things I've found: Dirt riders tend to push the bike underneath in a "crossed up" style vs asphalt riders want to go with the bike or even "hang-off" in the direction of the turn. Why? Dirt riders seem to not care about "racing lines". I'm not talking about situations where the rider is following a rut as that's understandable that you can't cross a 16" rut just to run a line, but they seem to not care about outside-inside-outside of turns like asphalt riders do. Why? 1 Quote Link to comment Share on other sites More sharing options...
JohnCBoukis Posted November 8, 2017 Report Share Posted November 8, 2017 1) Why do dirt bikers push the bike beneath them? "Because they can." Why do they not hang off? For what purpose would they do this? Can one flip a road bike side to side merely by shifting their weight? No, but one can do this laying the dirt bike beneath them, so this is actually an advantage in turning for the dirt bike. If you began a 180° from a crawl or a stop as dirt bikers do, this actually necessitates putting the bike underneath you. So I would say slow speeds and extreme turns physically necessitate this. To your point, dirt riders could hang off with their weight still on the outside peg, versus standing vertically on the outside peg like they do. However, that would be more work than merely laying the bike underneath, and their bodies would then be hanging out in traffic, traffic which is close or already colliding with them; more physical effort, with less safety, and for what purpose? There are lessons on this forum on how hanging off gains ground clearance. This is not a core problem on a dirt bike that has suspension travel designed to handle 5-story landings. One simply does not care about keeping a dirt bike more straight up. 2) You exclude the rut from your question but ruts and general degradation that quickly build up after the race start, and steeply banked turns are going to dictate many of the best paths on a given motocross track before other choices come into play. Any single gouge in the track surface is subject to directing the rider to another path that has more traction. A lot of motocross is correct obstacle execution at the correct speed (which is not always the fastest speed.) For the remaining rider path options I am going to make an uneducated guess that on a short motocross track that is only 5-8 meters wide, at speeds that are slow compared to road racing, the obstacle and turn execution will be much more contributory to the race times than an inside-out movement would be. Lastly, many obstacles such as whoops or jumps are approached best at a right angle. If one had to approach the road straightaway at a 90° angle, that limitation would completely throw away the path that clips the apex. Someone here described dirt biking as "point and shoot" and I think that says it concisely. The dirt has stops and starts and right angles but the road dictates a smooth, turn-interconnecting racing line. Thus they each have specific techniques which serve them. 1 Quote Link to comment Share on other sites More sharing options...
Lnewqban Posted November 9, 2017 Report Share Posted November 9, 2017 1) The traction is so marginal that the front tire cannot force the bike to turn as easily as tires on asphalt can. Sometimes, the rider tries digging the front tire into the loose surface in order to gain a traction that depends more on surface material building up over the sides of the tire than on pure friction. He/she achieves that by transferring the weight forward, by moving the body forward in the saddle and by extending one leg forward. When the described above is not sufficient to turn the bike as quickly as the next racer can, he/she increases lean angle which makes the rear tire step out of line. That achieves two things: the torque on the rear tires pushes the front tire to stay more or less in track by sliding less out of the turn and the material building up on the out side of the tire helps improve its traction. 2) Making the most from the marginal available traction is the priority. Those are their racing lines. Outside-inside-outside lines are for reducing the length of the curve and increasing the radius when traction is plenty and surface is firm enough to grant a precise line. 1 Quote Link to comment Share on other sites More sharing options...
Lnewqban Posted November 12, 2017 Report Share Posted November 12, 2017 Revisiting your #1 question, asphalt riders push the bike under them sometimes. Both types of riders are improving the agility of the bike to lean over the desired side when they "disconnect" the mass of their upper bodies from the mass of the bike. Yes, the result is an exaggerated final lean angle, but that could be beneficial on asphalt as well as the front tire turned at full lock will describe a smaller radius with a greater lean angle. The first five minutes of this video show the dramatic differences in steering inputs, accuracy of lines and available traction between dirt and asphalt: https://m.youtube.com/watch?v=BzF_q5ivlKE Quote Link to comment Share on other sites More sharing options...
Jaybird180 Posted November 12, 2017 Author Report Share Posted November 12, 2017 The most intense corner-workers I think ANYONE has ever seen! Thanks for the video. Yes, clearly there is a difference in styles. I'm wondering if it's a matter of machine design that makes the style difference more pronounced. For example on my dirt bike the other day, I noticed that it seems the designer wanted me to ride the front as there's a dip in the seat, like the dip in a two-hump camel. My long arms means I've got a short reach to the bars and therefore my steering isn't perpendicular to the steering head, almost a downward action. Conversely, the reach to the bars on my sportbike is further forward, causing me to lean in and requiring a distinct steering action to get agility from the bike. Where I place my weight seems a secondary effect of the bar input requirements. I'm wondering if this has some bearing on the counter steer vs counterweight debate....but I digress... Quote Link to comment Share on other sites More sharing options...
DucPati Posted February 3, 2018 Report Share Posted February 3, 2018 MX tracks have much tighter turns than a racetrack, at much lower speeds. Due to the lack of traction, you often steer by sliding the rear. It is easiest to control those slides with all your weight over the front - if your weight is over the rear, that’s a lot of extra momentum being thrown sideways. With your weight over the front the rear can slide around all it like without you worrying about a high side. So the standard riding position is: if standing, chest is literally directly over the handlebars (there are some exceptions, like soft sand, where your weight is as far back as possible); if sitting (usually only while cornering), sitting as far forward as possible, even on the tank, again with the chest over or nearly over the bars. How do you propose to hang off the inside of the bike for corners like this photo with deep ruts? Watch this and see if you can find any point where hanging off the inside of the bike would be beneficial: 1 Quote Link to comment Share on other sites More sharing options...
DucPati Posted February 3, 2018 Report Share Posted February 3, 2018 Just for a laugh, here’s how the amateurs (like me) do it. Five days later on New Year’s Day I over jumped a table top (on the same track), bottomed the rear suspension (I think the frame may have even hit the ground) and fractured my ankle, so am in a moon boot for another week or so. I did ride it out though, so it doesn’t count as a crash 1 Quote Link to comment Share on other sites More sharing options...
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