why light wheels make your bike turn easier

Dances' point, if I am correct, goes to the ratio of sprung to unsprung weight. If you reduce the weight of the package, the engine/frame/rider, then you also should reduce the weight of the wheels, and/or, adjust springs and dampers. All to account for the reduced package weight.

And, I agree too that braking spinning wheels is an over rated aspect.

Dances makes a mute point as light wheels help heavier or lighter craft though lighter wheels may benefit a lighter cycle more than a heavier bike. If lighter wheels uspet a cycle then just means something innately wrong with the cycle construction not the lighter wheels. Just putting in a hot cam w/o changing other things may hurt performance until other components changed to take advantage of the valve timing. Lighter wheel imply need of less spring rate and shock dampening to get more benefit.

I sure could tell the brake benefit of Hienz Kugler 1.5 lb lighter factory rotor and so should everyone else.

xbacksideslider nailed it.

The primary benefit of lighter wheels is road compliance. It goes back to the basics of bike building and development - make it handle, make it stop and then make it go.

Hobot, the word is moot, not mute. I can assure you that any "brake benefit" you thought you felt with Heinz Kegler's 1.5 lb lighter factory rotor is not due to rotational mass but due to drilling and surface preparation (ex. new uncontaminated disk surface). The radius of gyration of a disk rotor is not significant compared to the tire, tube, rim and spokes.

hobot said:

If lighter wheels uspet a cycle then just means something is innately wrong with the cycle construction not the wheels

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"If?" Well that is not the case. Lighter wheels will allow the wheel to be more compliant to the road. A lighter wheel means less damping is required - good thing. For a given bike, if you reduce the wheel mass you may need to adjust (reduce) the damping to match the system (unsprung mass, sprung mass and springs). Think about it, if you could get the unsprung mass to zero, then in theory, you would not need damping and the tire would follow the road surface 100% compliant.

Thanks for correcting the dyslexic on mute vs moot, ugh. Neither Xrider nor you got the "main", "primary" reason for lighter wheels benefit, which is the spun mass - I indeed could detect on THE Gravel and pavement with 128 holes and 5 kidney bean sections out of the disc. [Burning pains hit my palm on first break-fear reflex to break that dangerous reflex in me for ever more.] It ya could get that much off just sprung fork mass say by carbon fiber axle and slider and no fender and alloy axle nut it would not pay back as much road compliance nor spin acceleration or deceleration as when taken out of the spinning parts, especially the outer rim of the spin. Ain't no meat off my bones if you don't understand this energy ratio so carry on with low opinion of me and your own new branch of unfounded physics.

" For a given bike, if you reduce the wheel mass you may need to adjust (reduce) the damping to match the system (unsprung mass, sprung mass and springs). Think about it, if you could get the unsprung mass to zero, then in theory, you would not need damping and the tire would follow the road surface 100% compliant. "

REBOUND damping is largely for the unsprun mass ( wheel assemblies )

But Your still going to need the COMPRESSION DAMPING for the Sprung Mass ; Motorcycle / Rider / Fuel , etc aboard .

No Damping and the right series of bumps would amplify and you be thrown into orbit . :wink: 8) due to the SPRINGS ,
so the ' spring action ' needs damping too . . . :?

If the wheel had no mass there would be no gyroscopic effect, and the bike would not stay upright. The mass of the wheel contributes to the feel of the bike when combined with the steering geometry. Some setups inspire confidence, others do not.

Referring to my theoretical case of zero unsprung mass:

Matt Spencer said:

But Your still going to need the COMPRESSION DAMPING for the Sprung Mass ; Motorcycle / Rider / Fuel , etc aboard .

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Not so. Maybe a greater and more progressive spring rate could be effectively used.

Matt Spencer said:

No Damping and the right series of bumps would amplify and you be thrown into orbit . :wink: 8) due to the SPRINGS ,
so the ' spring action ' needs damping too . . . :?

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In a zero unsprung mass scenario the springs also have no mass. There, problem solved. :wink:

I like your humor and you get it.

Ugh. Gyroscope of wheels does not keep a bike upright. The fork oscillation is what keeps a cycle upright when rolling and then pilot's balance and fork oscillation when standing still for a burn out stunt. Recent physics class made news of demo of cancelling gyro force of wheels - had no affect on bike rolling up right or turning. In the cycles we can ride with wheels fairly light compared to the bike and pilot mass only thing wheel gyro's do is resist change of lean angle to tip over or pick up. On the other hand with ridiculous size/mass/speed gryo's, such as automobiles attempting to use flywheel energy storage there is very serious show stopping problems trying to build it so bumps in road or steering action is not so harshly resisted by the gyro and its pression force it don't jerk steering wheel out of hands or rip gryo bearing supports out or even tip car on its side or flip upside down. OK in a bus but not a sports car eh or motorcycle. You can not really fully cancel gyroscopic forces by additional opposite turning flywheels as matter does not occupy same space at same time so can't mount opposite gyro's in same place needed to for full cancellation. Main light wheel advantage is less inertia to spin up or slow down, secondary is less unsprung mass to control.

ITs the bike and pilot mass and road texture that determine spring rates needed not the wheel mass. Lighter wheels need less spring dampening and if zero mass there would be no need of dampening. Picture raw fork spring pulled open or compressed then let go, one action-motion cycle to reach resting length. Put the wheel on then one action to stretch or compress but will bob a bit on rebounds till still. You need a mass on each end of a spring to cause it to need dampening to stifle the rebounding, remove mass on one end and spring will snap to rest length in one action w/o a damper needed just internal spring friction. While tires in contact with ground the spring acts as if whole Earth attached to one side of spring and little ole cycle and pilot to the free side. I catch enough air time to feel suspension cycle rates dampening down and the instant appearance of full engine vibes the iso's can't isolate w/o the Earth mass acting on other end of rubber springs.

In physical chemistry one needs to know the mass of atoms and subatomic particles to calc bond lengths and angles with some fudge factor converting the lightening fast motions of mass into energy of spin using E=mc squared. ugh.

This article has some the physics of bikes in it but only in regards to hands off peddle bikes or powered up Ms Peel and fast off road ridding > but very little of physics on how most road going m/c's are ridden with counter steering. Non of this is common sense intuitive, and I crashed a lot following the common nonsense offered here and in thick thesis till my Guru THE Gravel lesions sunk in to the bone-bike fractures. Of most note in the video animation is how line tires gets out of line when turning.
http://physics.stackexchange.com/questi ... ll-and-why

Hobot, if you sit on your stationary bike and put both feet up on the footrests, even if you bounce up and down you will fall over eventually. A boke only has to be rolling at walking speed and it becomes stable, due to the two gyros front and rear. otorcars are inherently unstable at high speed due to their combination of four gyros, however at very high speeds, some bikes become so stable that they are almost impossible to turn. If you have heavy wheels you need quick steering, if you have light wheels stability must come from the steering geometry to get the same feel. Modern bikes have light wheels but much larger ( heavier)tyres than old style bikes. There is intersting comment in Motorcycle Classics last month, from Cathcart about stability of the 750ss Ducati which was ridden in the six hour by Hailwood and Scaysbrook against the Z900s

Thanks for some more scope on wheels and geometry Alan. Steering = handling is influenced by everything we've covered but what makes it extra confusing is what may be the major influence one instant disappears and two other things slash together to dominate the next instant. People with good skill can balance a motorcycle w/o rolling, with great skill even swooshing tail about on a burn out and about any of us can creep 1-2 mph pretty well w/o gryo help using some fork correcting action. Proof gryo's not needed to keep a cycle from falling. Also note at creep speed to ~12 mph one straight steers but going faster wheels and crank gyro's both resist the turning and develop counter torque force to turn so we must lean in opposite to over come those forces and help it-rear tire fall over with counter steering. Do make special note that all cycles steering hands off are falling over on their own and automatically straight steering no mater the speed. Another proof gyro's don't matter much; as can't be doing opposite physics in same conditions, such as in nice banked turn at steady 70 hands on we all must counter steer, yet if you- me take hands off and use body English the bike will begin to lean that way and turn same radius lines with fork doing straight steering. Its slower to lean w/o hands help but once bike reaches the right lean then away ya go with gyro's helping hold steady state.

I know all I want to learn about balloon tires on/off pavement, they suck except for wear and heat handling. They are a drag on my arms and endurance just to motor around legally on a girly light bike and at hi speeds their mass makes even more work to tip and turn and lift back up in time, ugh. The sharper steering moderns use to counter their tire mass and wider shorter patch also makes them dangerous to twitch right out from under or toss to hi heavens even with a freaking steering damper hindering of extra effort to steer in time.

I've explored this gyro, inertia and other handling phenomena that come and go in waves or instant terror spikes and developed ways to over come or make use of gryo and inertia and no longer ride smooth to ride accelerationly fast. I am the most jerky pilot I ever seen. If ya jerk on a gyro fast/hard its almost a solid sense, like slapping water fast-hard but if done smoothly slowly its almost like not even there. A tire can take horrenous loads - for an instant, but not longer. Grab/Jab brake in one hard stab and release > will spike a G force well over what can be gotten by best feathering or ABS. Same with front traction, can jerk fork to spike a vector for a instant then let go for the resultant reaction, like riding by someone close that kicks your bike the way ya want it too and is enough on that one kick to get over like ya wanted to, so suddenly no more steering action needed, just apply rear thrust as needed.

Of course that is how one low sides and hi sides a cycle, so low sides and hi side are just further evolution of advantages of a jerky pilot crashing on purpose any way they want. This is a phase change of energy handling, just like water heated turns to steam that requires different ways to handle its extra energy advantages. To get to that point means going so harsh the smooth control is not fast enough nor potent enough ti hold the loads so first real spike over whelms cycle trying to hold it stable.

I know all about the wisdoms of feathery smooth on every influence known while just commuting on THE Gravel in sections ya can't hardly stand on so loose, sloped. But that is just plain sane survival mode and tire preservation and not the method I use to travel it in hot purpose or being chased. Oh the bike and me may carve a nice arc with 2 tires lines almost 2 ft apart but its while doing hectic fork throttle and leans like little maneuvering jets on orbital craft, just spit for an instant but which need an opposite instant thrust blast to stop the first reaction or SPLAT.

Hobot, I suggest the most successful MotoGP riders are the ones who can interpret how their bike is handling and performing, and feed back top the support crew what to change. I don't think it is so much 'rider skill'. When first I started racing, one of the older fast guys said to me 'the bike has to do something for you'. Back in those days we had graded races - A,B and C. I had life membership of C grade. On a couple of occasions I lined up for practice, and the idiot on the gate waved me through into the A grade practice . I came to the realization that the A graders' machines were not much faster in a straight line than C Graders' machines (and I'm talking about back in the era of Manx Nortons and Goldies), however around the corners, the A graders were super smooth and effortless. I believe a lot of effort went into improving torque and handling, they also had decent tyres which most of us could not afford. I know a little bit about this stuff as I had a lengthy and painful apprenticeship which was full of anxiety. I love my Seeley 850, it is very kind to me.

tag for back ground flavor
http://www.youtube.com/watch?v=nYYTLJ8YHi4

yep Sir Alan, IIRC it was you that said only thing ya learn riding a bad handling cycle is how to not go fast fighting off crashes everywhere. As ya see the real test of cycles is their corner handling and a good cycle can make for joyful grateful pilot performance. I may be the only one in the world that no longer seeks nor can use any better handling > just 3x's more power to put it to the test. Various rock&roll themes hit me earlier on tri-linked Peel as I learned I could have me way with her w/o her complaining at all -

I almost died first few weeks on a factory Combat following a sports bike on its tail into a sweeper @ 80 when THE Hinge Hit! I knew then I'd screwed up getting a Commando as only good for quaint puttering around. Its was so clapped out and so not into mechanics I bought SV650 while learning hard lesions on Cdo fettering, ugh. SuVee got forks and shock upgrade then race tires and really got depressed at the loss I was taken to get the Cdo clunker sale-able and some sense of completed project. Took on anything with SuVee and learned to flat tract crossed up on THE Gravel but hesitant to try on tarmac so took Code's School with secret agreement to let me explore loss of traction on a real sports bike. OMG that pissed me off on wasted time money I could of had a real sports bike like the hot shots that frequent our area.

About 5 yr to get the Combat going with so much wrong others took pity on me on advise and parts it came out ok and started working up to what i'd learned to do on modern motorcycles and surprise surprise could match what I could do on them and nothing bad happened, Hmm??? WTF! So got to a make or break decision to see if I could break the dam thing and be done with it and discover when the SHIT Would Hit The Fan - like it always did on all the others... I called her bad names, I slapper her forks to crap, I tossed her around like a dirt bag. I made her wipe road grime up for me - I made her lick my ass and swallow - any thing everything just waiting to put her down at first hint of talking back to me or hesitating an instant to my commands, yet she did Everything Perfectly Eagerly beyond my imagination, till a deep shit eating grin permanently set in on what I had, She Was Under My Thumb, The Sweetest Pet in The World. The Change Had Come.
The rest are just corner cripples sluts to me now. Only reason I recovered Suvee goat crash 3+ yr later was for a friend to use out of my sight.

worntorn said:

In a recent test of the incredibly light BST carbon fibre rims, the testers recorded slower lap times with the lightweight wheels than with the heavier stock wheels. They speculated that the twitchiness introduced with the lighter wheels was causing the slower times.

Glen

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Glen, were you referring to this article? - http://www.sportrider.com/gear/146_0402 ... ewall.html

They conclude by saying that a stiff wind came up which made it difficult to compare lap times with stock and lightweight wheels fitted. The problem with that test is that, as they say themselves, they didn't play with the suspension when the light wheels were on, so they were not able to compensate for the reduced unsprung weight. Maybe it made a difference, maybe not, but we won't know. I can see a further advantage with light wheels in reducing rider fatigue during a race. You can sure work up a sweat on the track from the effort of simply counter-steering on a twisty track with fast directional changes and if the bike is easier to turn, you get less tired. They also mention chatter under braking with the light wheels. I know what that chatter is like on the track; you have to back off a tad and it slows you down.

Jim - interesting subject - thanks for posting.

Wow, it's getting pretty deep here. I always thought it was pretty obvious that lighter wheels and tires were better, but I guess everyone doesn't agree. So, leaving out the physics, I'll just summarize my experience, and you can take it for whatever it's worth.

I've gone from heavier (usually stock) wheels and tires to lighter (usually magnesium racing wheels and lighter racing tires) on several race bikes over the years, including Nortons and a variety of Japanese bikes, and in every case the benefits of the reduction in usnprung weight were really obvious to me as a rider. Noticeably quicker turn in, with less effort, and much less upset from bumpy track conditions. I never experienced any problems from the much discussed hypothetical changes in gyroscopic precession forces mentioned here. The only increase in chatter I ever noticed came from the fact that l could stuff the bike into tight corners quicker. If you go fast enough, almost any front end combo will chatter in corners. With a properly set up front end, you will go faster with a light wheel/tire combo before experiencing chatter than with a heavy one. If you're going slower with less unsprung weight, you don't have the suspension set up properly.

It's the same on the street. LIghter wheel/tire combo equals better ride and better handling.

IMHO, of course

Ken

To get a properly set up front end which do you change first - the rake and trail, or the wheel weight and tyre size, spring rate, and damping ? Personally I cannot think of a logical progression towards the ultimate for a given circuit , and getting there piecemeal seems expensive. My feeling is that the standard Seeley steering geometry is the point most guys work from, and don't move towards small offset yokes. I think my bike could become quite dangerous with lighter wheels, even as it is I am quite wary of it. Over the years I've had a couple of bikes grab me by the throat, it is very unpleasant. I am not imagining that my bike self-steers quite positively, and even Tony Foale has mentioned that happens as you reduce the trail.

Well well well Alan the truth comes out - which is All Cycles are Dangerous Corner Cripples, but one. All the rest are either too floppy loose like a real Norton Commando or are too stiff rigid like most 'elite' moderns - that can not be compensated for by fork geometry or anything else but not taking turns competitively with w/o risking unpredictable surprises. Oh sure some corner cripples configuration are faster than other corner cripples but all still cripples waiting to cripple you no fault of your own but to try to ride em past their capacity to handle the loads coming from all directions. No one has any idea but me how fantastic it is to have a ride that nothing can upset and lighter components only means more harsh accelerations to explore in several ways in & out of traction or even surface contact. Rigid frames need some extra mass at its ends to help dampen the splashes of resonance so apparently at some point too light of wheels become counter productive to corner cripples. Sail boats need ballast to handle wind and turn loads but hydro planes do not as they fly over the surface and cut corners so fast pilot needs harness to stay in control.

lcrken said:

Wow, it's getting pretty deep here. I always thought it was pretty obvious that lighter wheels and tires were better, but I guess everyone doesn't agree. So, leaving out the physics, I'll just summarize my experience, and you can take it for whatever it's worth.

I've gone from heavier (usually stock) wheels and tires to lighter (usually magnesium racing wheels and lighter racing tires) on several race bikes over the years, including Nortons and a variety of Japanese bikes, and in every case the benefits of the reduction in usnprung weight were really obvious to me as a rider. Noticeably quicker turn in, with less effort, and much less upset from bumpy track conditions. I never experienced any problems from the much discussed hypothetical changes in gyroscopic precession forces mentioned here. The only increase in chatter I ever noticed came from the fact that l could stuff the bike into tight corners quicker. If you go fast enough, almost any front end combo will chatter in corners. With a properly set up front end, you will go faster with a light wheel/tire combo before experiencing chatter than with a heavy one. If you're going slower with less unsprung weight, you don't have the suspension set up properly.

It's the same on the street. LIghter wheel/tire combo equals better ride and better handling.

IMHO, of course

Ken

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Well there you go again, introducing logic, reasoning and real world experience to this particular stream of conciousness; it went from wellies to waders pretty quick.

acotrel said:

Personally I cannot think of a logical progression towards the ultimate for a given circuit , and getting there piecemeal seems expensive.

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I suppose a solid start (as suggested by Ken above) would be lighter wheel/tire assemblies. This is a solid primary improvement to handling and IMHO would be a logical first step to building a racer (or just about any other bike).

lcrken said:

Wow, it's getting pretty deep here. I always thought it was pretty obvious that lighter wheels and tires were better, but I guess everyone doesn't agree. So, leaving out the physics, I'll just summarize my experience, and you can take it for whatever it's worth.

I've gone from heavier (usually stock) wheels and tires to lighter (usually magnesium racing wheels and lighter racing tires) on several race bikes over the years, including Nortons and a variety of Japanese bikes, and in every case the benefits of the reduction in usnprung weight were really obvious to me as a rider. Noticeably quicker turn in, with less effort, and much less upset from bumpy track conditions. I never experienced any problems from the much discussed hypothetical changes in gyroscopic precession forces mentioned here. The only increase in chatter I ever noticed came from the fact that l could stuff the bike into tight corners quicker. If you go fast enough, almost any front end combo will chatter in corners. With a properly set up front end, you will go faster with a light wheel/tire combo before experiencing chatter than with a heavy one. If you're going slower with less unsprung weight, you don't have the suspension set up properly.

It's the same on the street. LIghter wheel/tire combo equals better ride and better handling.

IMHO, of course

Ken

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Ken - interesting to read your take on this from your own experience.

I suggest there is a problem in building a bike if you are relatively inexperienced. You can buy a Seeley frame and fork yokes and fit the light wheels, and then where are you if the bike doesn't handle ? My Seeley ended up with Yamaha TZ350 fork yokes simply because I had a fair idea what would handle from years of being involved in racing. I had the option of making fork yokes - however what offset should I have specified to the manufacturer ? You can ask all the other idiots, and you would get a variety of opinions. Most of us have raced for years and never changed steering geometry. We simply rode around our handling problems. One approach is to attend a lot of race meetings and watch the guys who are riding similar bikes to your own, then sneak up and copy what the best of them is using. They might get a bit upset when you click the magnetic base protractor onto their fork leg ?
What offset are you using on your fork yokes and has the frame got the standard Seeley 27 degree rake, Ken ?

daveh said:

worntorn said:

Glen, were you referring to this article? - http://www.sportrider.com/gear/146_0402 ... ewall.html .

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Yes, that is the article. I was surprised by the result, although as you say, suspension changes could alter the result.
I am interested in trying lighter wheels on my Special, but do not want to spend the money only to find out that the net result is only a small improvement, or worse, a detriment to the overall ride. Most of the numbers on acceleration/ deceleration improvements and claims of dramatic positive results come from the Companies which build and sell the rims, so they may be a little optimistic.
It would be nice to see some hard numbers, but other than the actual weight and moi numbers provided by SportRider in this test, there isn't much out there to go by. I mistakenly said the test was recent because I read it quite recently. It is actually quite old, from 2004. Searching for newer info hasn't yielded anything yet, other than there is some concern that the Carbon Fibre wheels might have a tendency to go POOF at very inopportune times.
From that article-
The lighter unsprung weight of the Blackstone Tek hoops also made a difference in the bike's suspension. The GSX-R tracked better over the Street's rough patches, and felt more compliant in general. With more time on the wheels, we'd want to make some suspension adjustments to account for the decreased unsprung weight.On the downside, the normally solid Suzuki was noticeably less stable in fast transitions, and we encountered some brake problems with the wheels mounted. A slight pulsation under heavy braking from fast speeds with the stock wheels turned into a major chatter, and it felt like there was less feedback under braking.Lap times during the test were inconclusive-a stiff wind came up once we had the Blackstone Tek wheels installed, and our man went a hair slower than with the stock rims.Hoop It Up ExtrasFor additional images and information for the February 2004 wheel test, simply click here.Read more: http://www.sportrider.com/gear/146_0402_motorcycle_wheel_comparison/viewall.html#ixzz2gVJsNoAJ