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RUBIK'S CYCLE or madmotomike's continuing education
[size="4"]must clarify..i keep refering to my street beastie as an 1980 sr500...................that was its "starting " point.
just yesterday it grew a cast 3.00x 17 rim off a suzuki gs500e[. this is because is ran out of 18 inch tires to cannibalize for the stock rim. (18 rears are getting a bit hard to find in cast off tire piles) i have a good supply of 17s and had an almost new avon gripster 130-80-17 that sure works a treat on my beast.
so how's it work? great!!! the smaller diameter reduces slightly the gyroscopic influence of the rear wheel makeing the bike get " on its side" even faster! this is a good thing. the extra width creates MORE CONTACT patch and that reduces the "PPI"-----"THE POUND/INCH" loading of the patch =better tire longevity .
of course it took a rear sprocket off a suzuki gs550L 1985 out of my backyard to work with the new tire/ wheel circumference to reestablish the "gearing" i want to run.
bike has taught much about motorcycle setup and how the "settings" of assorted components affect handling /stability. ...." THE BIKE'S NOT MINE..LOL"
BIKE has worn handlebars from 22 -34 inches wide....from flat track to clubmans.
front wheel has been as small as a 16 and as large as a 21.
rear wheel has been 16-18
shocks have been from 13.5-------8 inch struts
best front springs have come off of 750 -1100 bikes from the 80's( need 36 mm fork springs off of much heavier bikes....deal with my aggression and weight).
swing arm off a yamaha radian 1.5 inches longer....huge advantage especially in tight lower gear corners where more "modern" high power high cg short wheelbase bikes decree that you accelerate "carefully" and accurately lest you end up in the bush on the outside of the corner or worse.
fact is a "long swing arm" is desirable but not a long wheelbase. long wheelbase slows steering and handling. long swing arm forces more load on the front wheel . good as most bikes from the 80;s-90"s have a built in rear ward weight bias.
the brake torque arm is off a honda cb650c.
shocks are off a honda cb700sc.
has run stock pipe...aftermarket low pipe...and aftermarket high pipe
tires have ranges from knobbies to road racing compound tires. best rears are the dual sport tires or anything with alot of "pattern..". makes the tire very forgiving and gives more "options" when cornering hard.
best front is dunlop k81 but it has worn almost any and every thing at one point or another. knobby worked great on the rear but was a bit "dicey" up front. but HEY my determination to NOT have to BUY tires is strong. and it has been an education.
over tireing is a bad idea..under tireing is not much better---every ride "off" the edge of a tire? NOT FUN! I ASK YOU --if your foot is a size 12; you do not buy a shoe size 13 for it . do you? oversize tires distort profile and will create "false limits" as you lean over. just much more difficult to deal with. DON'T DO IT.
MY bike has worn front tires as rears. generally just reverse the arrow as the sheering forces at work on the bike are in opposite directions. not front tires always have more pattern than rears and less tread depth. the tread depth is too bad but the more extensive "pattern" gives much communication/forgiveness. the metzler 110-80-18 me 33 laser was superb!!
if i have a regret it is that i have yet to find a handlebar with enough rise to allow me to ride standing up in a relaxed yet powerful position. most of the bars coupled with my extreme build have me bent over severely and somewhat off balance. might try some atv bars with about nine inches of rise......
note the longest shocks did improve travel and dampin but they created a down angle on the arm itself. placing the swing arm pivot point significantly about the line thru the axles and centerline of the crankshaft that is agreed to be ideal. end result...cornering clearance improved but now the cg is raised enough relative to "THE LINE" that the bike wants to wheelie under hard accleration. not a good thing for hasty corner exits....shocks were put back on shelf.
strut s were good in that they eliminated changes in geometry. and they allowed a very low center of mass to be achieved which helped speed of turnin. HOWEVER ...."ANY" pavement imperfections negatively and instantly affected traction. not good but educational.
next experiment is to adapt the complete rear swing arm shock and wheel from the gs500e AND the front end as well!
i really like the commitment the stock 19 gives. it is a strong and some what large gyroscope that gives my beast maximum versatility when used in conjunction with the 34 inch flat track bar. stability /speed / agility all in one.
19 is also more stable under max braking than the smaller fronts;
the 21 is great but much larger gyroscopic inertia...just what you want in sugar sand or slimey mud but not so great on tight race tracks. would be my choice to circumnavigate the globe but most 19 rims are cast and tubeless. an THAT IS MY FAVE.
REAR brake was too fierce on the sr500 --the mz baghira sumoto and the bandit 400(all bikes with weight transfer issues). i reduced the swept area on all of them to my corner entrys a bit smoother and easier to execute at a high level. just grooved the pads to take away some power. worked great!
yes my sr500 has been a wonderful tool..teaching many lessons and aiding my understanding of "how /why things work" as they do.
most bikes do not reward "'spermentation" or "fiddling". an old bike from the earlier eras can allow a person to "test" ideas and they are forgiveing. modern bikes have very small ranges of optimum setup ...b
but most people are not "REALLY" as involved with their bikes and how they work or how to improve them for a specific rider.
my personal test with new riders is a simple conversation about tire psi. "say what tire pressures are you running ?"
worse thing some one can say is "oh i don't know" . second worse thing is "oh THEY set it at the dealer" FACT: THIS IS THE BARE MINIMUM KNOWLEDGE AND SOME WHAT CRITICAL SETTING THAT AFFECTS EVERYTHING"
MAKE IT AN ISSUE...UNDERSTAND.....tuning range is 26-40. 26 gives biggest footprint but allows carcass heat to be higher. 40 has smaller contact patch but does help tire carcass run cooler at the expense of faster more severe wear in a smaller area in the middle. if track /street is damp run dry pressures . if standing water...over inflate tire by about 4 psi(will reduce contact patch open tire sipes and increase ppi)
AND IF you WANT to ruin some under wear...set the front at 45psi. set the rear at 28 psi. turn the front preload and damping all the way hard. set the rear preload and damping full soft/low.
for added measure introduce about 4mm of slack in the throttle cable. position the levers very high...
bring a camera and make a fortune!!
any way the research continues and my sr500 beastie and i will keep doing the testing. of course THEN I HAVE TO DECIDE which compromises give me the most joy and versatility...for i truly hate limitations.
just a simpel motorcycle but what a reference manual it has provided.
tommarow's speriment is to establish an absolute limit as to how much front end "drop" my bike will tolerate BEFORE contacting the front fender to the exhaust head pipe. and then work out and optimum with regards to height of center ofmass, speed of steering, cornering clearance, cornering stability of the vehicle.
wish me luck
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