why light wheels make your bike turn easier

All child's play really.










I've had these screen grabs from "To Kill A Mocking Bird" on my desktop for a while. I want to print them up for my shop.

The direction of the precession is not obvious when you think about turning a gyro. If the front brake is dragging and the bike is steering itself off into the bush, I wonder how many of us would know how to get it back under control ?

comnoz said:

swooshdave said:

comnoz said:

My preference is Excel rims.

I get them from - http://www.buchananspokes.net/

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What is the weight difference between the stock steel rims and the Excels? Buchanans makes it sound like there isn't much.

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No there isn't a big difference between an Excel and a stock steel. You will notice a difference when you change however. They do make the bike feel lighter. The Excels are about bulletproof.

I will not use the lightweight aluminum wheels anymore [Sun] after jerking the spokes out of one on a rough section of track at PPIR. One time is once too many.

Now if you want a night and day difference try replacing an old pair of SR500 mag wheels with spoke wheels from a TT500. You wouldn't think it was the same bike. It almost transforms them into a decent handling motorcycle. Jim

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That last part - about those stupid Yamaha "wagon wheels" is SO true. When I first got my SR500, I was accustomed riding a 450 Ducati with a pair of Borranis. The first turn I went into with any speed I overshot ! The darned SR would NOT turn. I quickly found an aluminum rim/steel spoke wheel off of a Yamaha TX 750 (air cooled parallel twin) that would drop in/bolt up; the rim was a knock off of a Borrani/Akront. Transformed the SR. Helped the braking too.


Lost to us now are the super light wheels of the late 60's/early 70's - light gauge painted (not plated) spokes, quality forged aluminum nipples, quality valanced aluminum road racing rims, and condom thin inner tubes. All things of the past. Those wheels were fabulous in terms of acceleration, braking, and turning agility.

That said, they cannot take the side loads that are presumed by today's chassis design. They pre-date hanging off. Technique and technology has moved on.

Ugh its a hobby of mine not to smash ass when nil-no front traction, with or w/o brake applied. If not doing it on purpose or even if ya do, its entirely possible to save it but more highly likely to crash in a bad orientation to loose blood and oil.

I've noticed as other off roaders report that staying lower gear than needed to keep crank rpms up sure helps doddle alone and not fall over on loose rough paths.

This stuff is what I cut my teeth on. In rotary phone-slide rule days we had to calc. the angular moment of inertia of a paint chip spinning on its own axis while orbiting a tumbling satellite it came off of in relation to the Earth's core the satellite was orbiting, ugh.

'That said, they cannot take the side loads that are presumed by today's chassis design. They pre-date hanging off. Technique and technology has moved on.'

They also pre-date gumball tyres, however I've never heard of spoked wheels giving a problem on a commando or a seeley race bike. Or even 70s classic superbikes - 'hanging off' riding style was around for a long time while spoked wheels were used in historic racing. What we didn't have was 200 BHP motors.

Just had my rear wheel off of the Nourish Seeley rebuilt; one broken spoke after NJMP in July. Had to do this at least once or twice before when the wheel was on the 750cc Norton Seeley with the ultra short stroke engine.

It happens.

Hm harsh loads break spokes, ok what might be a light wt solid wheel that might adapt in say 16" dia.
Mag wheels are effective if ya could just replace now and then or somehow seal well. Maybe print out some Mag-Beryllium wheels. Seeking weigh loss is excusable disease that can kill ya.

"Lost to us now are the super light wheels of the late 60's/early 70's - light gauge painted (not plated) spokes, quality forged aluminum nipples, quality valanced aluminum road racing rims, and condom thin inner tubes. All things of the past. Those wheels were fabulous in terms of acceleration, braking, and turning agility.

That said, they cannot take the side loads that are presumed by today's chassis design. They pre-date hanging off. Technique and technology has moved on"


They are back. The Morad Company of Spain purchased all of the old Akront wheel manufacturing machinery and the name. I just bought a set of very light weight flanged alloy rims fo the Noton and they look identical to the lightweight flanged alloy Akronts on my 192 lb 1972 Mick Andrews Replica Ossa Trials bike.
According to Central Wheel, these old style Morad/Akront flanged alloy rims are their strongest rims, stronger than any of their steel rims. Big old flange on there giving strength. I have certainly tried to bend them on the trialer, but they have held up to all the abuse including rock jumping.
To top it off the new rims even stamped Akront/Morad. Who says you can never go back?
The WM3 is about 2.5 lbs lighter than the chrome over steel Dunlop WM2 being replaced.

The basic rule of thumb is if ya remove 1 lb of spun mass its equivalent to 8 lb removed other places. I sure tired to find the Morads after hefting some used ones at a rally but they were not available far as I could find a few years ago. What do these go for nowadays? Usually spokes pull out before wheel collapses but very glad to hear some one lightly leaping about on them.

Check out thse rims for lightweight.
http://www.de-tris.com/#!slideshow/cjv3

I have some of the older Borrani shouldered rims on my p-11 scrambler. I wish they were a little stronger.

Neat carbon rims for sure but do they still require a tube to seal the spokes? Strength and toughness are not the same thing like we've seen in the Li battery saga.

hobot said:

spun mass

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Concerning weight removal, it's not about the mass being SPUN, it's about it being SPRUNG (with the suspension).

On another (unrelated) note, take your favorite medium-speed corner with as much of your weight possible on the inside footpeg. Try it again at the same speed with your weight on the outside footpeg. Notice any difference?

Fun with physics.

oh Dear Paul please correct your understanding of this spun vs un-sprung subject. A pound off the spun mass is said to be worth 8 lb off sprung mass as far as performance is concerned. I have tried every aiming handling method known to man and beyond to now ignore the slipshod wisdom-ignorance of peg weighing and or hanging off body English in a bike that weighs more than the pilot. What does matter-work at least for me is locking front patch to rear patch with my strength with me in as close to bike mass as I can. I can't afford carbon wheels right now but may have to against my prey with carbon fiber everywhere. Going tubeless is best hope Peel's got for lower spun mass, if I can keep the air in for some hours. I run tubeless pure race balloon tires on my corner cripple SV650 and can tell ya they are rather thin like house slippers compared to the boot like DOT tires. This didn't sink in till trying to find a leak I soaped the tire to be shocked the whole tire thread area was foaming from the points of Gravel poking through. I am still upset to hear a tale that lighter wheel made bike uncontrollable and heavier one solved that. Only thing i can think causing that is light wheel allowed the rear thrust to lift-lighten front out of traction, which is what I aim for when really getting with it on Peel which is the beginning of my thrill level on 'her'. Come on out on THE Gravel which teaches everything ya need to know about cycle physics with errors impressed immediately or sooner before ya even know what went wrong, till new sense of physics pounded in to the marrow.

BlackStone Tek– BST – Effects of Inertia
http://www.blackstonetek.com/inertia.html‎
Lighter wheels will make a major difference to the handling of your bike. They will also ... m being the mass and v being the velocity at which the wheel moves. Once the ... The lighter the wheels, the less your un-sprung mass. This means that ...

Dead weight v/s rotating weight [Archive] - Bike Forums
http://www.bikeforums.net › ... › Bike Forums › General Cycling Discussion‎
Apr 16, 2003 - 31 posts - ‎16 authors
3) Every extra gram of mass on a bike is extra unsprung mass, which has a ... As far as rotating vs. non-rotating mass, rotating mass is only a factor .... cause you gotta both accelerate them forward, as well as "spin them up.

Hobot is correct, the big advantage in having lighter wheels and tires is having less mass to spin up(acceleration), slow down (braking)or move off the straight line naturally followed by a gyroscope (handling). The advantage to suspension, mentioned by Paul, is also in effect.
The only possible disadvantage in having light wheels is the introduction of twitchiness. When you make the wheels lighter, now it takes less effort for the rider to make direction changes and they happen quicker.The bike also responds to imperfections in the road surface in the same way, it gets knocked off course more easily. There is probably a point where the wheels are so light as to make riding the bike fast on patchy pavement a difficult proposition.
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.

Sort of like the difference between a racing sailboat with a knife keel and a cruiser with a full length keel.
The cruiser takes some effort to come about, however it can be left with the tiller pegged in position while you go down below and make a sandwich. Try that with the knife keel boat and you will be in big trouble!

Glen

Twitchiness can mean a crash if your steering geometry is on the limit. With my bike, I am always careful when I start to use its self steering effect by getting on the gas very early in corners, Even a change in tyre pressure can affect what it does under duress

Yes, Alcotrel, on the latest forged/heat treated aluminum wheels, the ones that weigh about the same as steel wheels, riders can hang off, and those wheels are built with big heavy spokes/nipples too.

No comparison to the narrow flyweight wheel sets that were built back in the late 60's - WM1 and WM2 Borranis with thin painted spokes/alloy nipples on bikes that were in the low or even sub 200 pound range. Those wheels will "potato chip" if you apply side loads.

Worntorn - yeah they bend more easily; back when, for dirt, the Akronts were much preferred; they were stronger than the Borranis and considered to be quite a bit heavier. Back then my opinion was Akronts were for dirt, Borranis were for road racing. And, yes, the Morads are a welcome offering.

The evolutionary response to the "twitchiness" of super light carbon wheels might again be changes in geometry, or even the addition of a substitute - light weight small electronic gyros - but yes, the gyroscopic stability lost by way of lighter wheels is a definite trade off against quicker acceleration and braking and as Grandpaul noted, better suspension action.

Now, many folks know of bikes where no matter how heavy or how light the wheels, the bikes were twitchy at highway speeds and felt like they were going to spit you off at any time (like early Z bikes). Forget trying to corner on those lugs, no matter what you did with the wheels AND suspension.

Are you including British bikes in that ? Many evolved in companies which had been involved in road racing and handled very well. If you fit the wrong fork yokes to a featherbed, it can grab you by the throat. Fitting lighter wheels to a bike which has rake and trail already on the limit of stability could create a problem - great in theory, but in practice you might find yourself fighting the disappearing handle bars if you don't proceed with caution. Changing steering geometry is not easy, and I suggest that many road racers who ride converted road bikes already simply ride around their handling problems. You will note that modern MotoGP is usually only run on very smooth circuits. Perhaps the bikes are on the limit of stability ?

worntorn said:

Hobot is correct, the big advantage in having lighter wheels and tires is having less mass to spin up(acceleration), slow down (braking)or move off the straight line naturally followed by a gyroscope (handling).

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Opinions sure vary about this. All your claimed "big advantages" in having a lighter wheel amount to nothing if the wheel is not compliant (hooked up) to the ground. One of the most critical things is traction and if your wheel is unable to maintain contact your literally flying away.

This becomes ever more important as the sprung mass becomes lighter; if you don't do something with reducing the unsprung mass the task of damping becomes more difficult and you compromise with less road to tire compliance. A little more power (engine or brakes) will easily overcome the rotational mass. Stopping a bike has never been an issue of too great a rotational mass (except maybe for Fred Flintstone).

There is probably a point where the wheels are so light as to make riding the bike fast on patchy pavement a difficult proposition.
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.

Sort of like the difference between a racing sailboat with a knife keel and a cruiser with a full length keel.
The cruiser takes some effort to come about, however it can be left with the tiller pegged in position while you go down below and make a sandwich. Try that with the knife keel boat and you will be in big trouble!

Glen

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Oh man Glen the closest thing I know to compare my Peel too is water craft both the kind that slice the water as well as those that plane on top. Modern racers are innately twichy when pressing down into powered turns. Much as it may urk Dances, I know why there is such a thing as too light of wheels on the corner cripple moderns and it has to do with their mis directed over rigid frames w/o enough dampening built in, the poor dangerous unpredicable things.

Dance's I can't believe you believe that spun mass has not hindered motorcycle braking or accelerating for ever and ever. Glen knows ya can hang on to a line on a light boat but will rip arm off or drag off dock trying to hold mass of a heavy boat. Ya can put a boat on a ship but ya can't put a ship on a boat.