A bit of subject here
Why are American Dirt track bike set up so different from Aussie bikes.
tyres etc. Is it because of track surface...?
MAin reason we both do Flat track is we have similar climates, its not somthing that can be done in very dry weather or mud, it needs some level of predictible. So to some degree we are the same, but like aminals we have evolved differantly because of local differances and influences ( ie JAps and Mx).
but there are Lots of reasons id say.... mostly for them thats how it has always been, they used to ride on staked out flat land like wagon train racing in the real early days, then over the years as they got faster they built banked corners, even to specialised wooden board tracks.
As the fair ground scene took off, races where promoted as winner take all rides at the fair grounds usually set up on open land with on a horse racing track so the same road bike would be ridden to the track, road gear removed and raced to try to get the promoters $$ purses. as money was good, the roadies followed the circuits trying to make a living out of it going town to town following the carnies. the bigger tracks where 1/2 mile or mile horse tracks, so the bigger road bikes would eat up the little ones on the 2 main straights, so they kept the road look but streamlined em to go fast, and it evolved from there,
nowadays they are mainly MX bikes dropped on the rears links and fork to get a lower CG, the same as what we use now.Also its worth remembering that many of these period bikes where also interchanged in the old GNC series rounds, so in one season the same ridders doing grand national points did TT, Short track, long track, Road racing and maybe pikes peak or somthing, many would use the same motor in differant frames, or reset the frame/bike for the other disipline, like level the pegs out and add a front disk for the TT ( track with jumps), i guess the best version of that would be the KR - TZ750 where they used his road bike motor and stuck it in his DT frame for that meeting. So strong motor setups often outbid original frame layouts which would be modified for different events/distances. If you notice on a good flat track the guys pass in corner or on the run out with the speed they carried out of the exit, nothing really happens on the straights, so out and out power means little its all about Traction and getting it through the rear, in the right amount of hook up. Hence many frames can change there Rake, trail etc
The other thing you would notice about there good tracks is that there professionally made, thats what lets them run purpose made tyres like the goodyears. These top tracks arent farmers dirt like some over here, lucky to see a grader once a year, Many top tracks are like a les burdett cricket pitch, has just the right blends of a number of elements including clay, granite and sand. The banking helps drainage but so does the mixes in it. A good mix means good water depth through the clay, while keeping it solid to eliminate bumps or dust. Remember unlike here in Aus where we pay an entry to win a plastic trophy on a track stacked with volunteers, overthere it was a promoted business with prize money. it was a serious business, to attract the show card riders you needed a good purse and a good track, so its stands the tracks had a more predictable element than here in Aust.
I think Australia though kinda stayed more with the british and went Speedway style on the Ovals and Mx/dirt bike or xs 650 style on flat tracks, specially the ones with the kidney shapes or right hand turns, these bikes dont go so well in the other direction unless you reset the pegs and a few other bits. I got a couple of Flatties and they turn left by themselves on a 50 cent peice, but ask them to go the other way and its like writing left handed.
Its a case of horses for courses.
As far as the tyres go though as mentioned, the surfaces are differant. You can see some US bikes with blue line tyres ( like road wets) cause the surface is so hard packed and oiled in, its rock hard with only some movement, other tracks are soft and loose sand like salinas (calif) and they would run speedway style tyre front and rear there.
They also do indoor meets on concrete (dont ask why) over there, but most period fotos you see where taken by the likes of Dan Mahony or his dad, and only a few others who covered only a few tracks back in the day, many fotos - a few tracks, so your more likely to see the same tyres over and over again, just because thats the bulk of where the pics came from.
It would be safe to say Most period bikes would have either the early universal Pirrelli MT trails or the later rounded Carlise style pattens (also in Goodyear, maxxis etc) as they both became standard race use in the 19". Going with that size, F/R the bike was not only level but you could swap backs and fronts and also flip them to the other edge and get double the wear, in a period where some guys lived from race to race travelling the US racing 3 nights a weeek, in fields of 150 riders in the heats alone, being able to get more out of tyres, be able to recut them or regroove them for differant tracks ment they could kept chasing there Pro dreams longer. ( attached piccy shows both tyres on my champion)
And there also was that weird period say from the late 80's the rules went very Harley, bit like the ford/holden stupidity of our supercar class, its a bit hard to get other makers or tyre makers innovating in a class that became a little too specialised, having said that though i have noticed there has been a resurgence in the other manufactures big twins offerings. In the size classes Yamaha, rotax, ktm, honda etc all provide bikes to riders and are the staple at all local tracks the same as they are here, chookies are now the standard worldwide for the majority. So the differances your thinking about really is from a period of the bikes themselves, where we moved appart, but due to global forces and influences have really come full circle and now run similar kit again.
I guess in a short answer to your question, you could just say the same thing for Car racing, why do they go round in circles and we go around left and right on street style ciruits ? Either car would find it hard to compete on the other track THE SET UP required is very different.
