why light wheels make your bike turn easier

Although that Sportrider article discusses moment of inertia, it minimizes the effect of light wheels on acceleration and deceleration. They could afford to since the test was performed on a 150 horse, more or less, late model liter bike.

Our bikes make about one third of that power and, by comparison, have poor brakes. That means that we get more relative bang for the buck by reducing wheel weight; our ratio of rotating weight to power is superior.

Light wheels are one of the cheapest ways to enhance your Commando's performance and you don't need new spokes or new rims; keep an eye out for used 40 hole valenced Akronts or Borranis and when you find them re-use your stock spokes.

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,
I agree with you 100% on this one. Jim

Well on the other hand heavy-ish gryo's can help a 2 wheel inline'r or even one wheel alone go around like stink on a skunk and not fall over like Burt Monro and so many others like me from side impacts or stiff wind gusts.

http://www.youtube.com/results?search_q ... M4qH8opSuE

http://www.youtube.com/results?search_q ... 1vQOAkNBbA

Well well well a gryo stabilized RC cycle that straight steers at some speed like the robocycles and me. hmm very interesting a gryo allows this as otherwise w/o it essentially means committing to a turn the bike actually is about crashing over on its own, and sure can, do scary as it is thrilling. Sure could store some energy up that way too for a time.
http://www.youtube.com/watch?v=Wgrw7A1iUKM

omgoodness gryo bikes are flooring me even this toy.
http://www.youtube.com/watch?v=aD59V1VXy9g

Gryo used to help children learning to cycle and not fall over, even if they get off, neato
http://www.youtube.com/watch?v=4Va6qgWcieA

I don't agree that lighter wheels are always an improvement if you already have very reduced trail. If your steering is already very quick (as mine is), what happens when you quicken it even further by using lighter wheels ?
One thing which we have never changed much over years of racing classic bikes, has been steering geometry. Many guys ride converted road bikes which can be well removed from the optimum for racing on tight circuits - they simply ride around their handling problems. When you start altering geometry, it is easy to create something which can grab you by the throat when placed under duress.

You kind of worry me with talk like that Alan because I've lightened up Peel wheels and changed CoG around so hope it ain't messed up the total nuetralness. It hard to imagine having better suspension control and less energy required to speed em up or slow em down or turn to aim or recover could harm handling. Yet in defense of your point there is a new product for 12" children's bicycles that replaces front wheel with one that's got a 3 speed gryo inside which resists falling over enough bike can stand on its own and resist side shove on hi setting. Look in the Gryo thread for the ad video on it. I don't think you want to be testing limits on a cycle that heavier wheels help stablize, ugh.

One thing I've found out about street use of non DOT race tires is they are like thin stockings so after some rubber loss to nearly wear off grooves air leaks out their whole contact surface, leaves a foam covering that shocked me trying to find a leak on some of them, ugh. When they get like that its time to play spin em up and use em up on THE Gravel till cords show, usually d/t chunk thrown out rather than a smooth balding like DOT tires. I'm having trouble getting tubless beads to seal on tube rims so will try Hylomar or have to revert to tube mass inside. Dang ole 130 Avon race tire Ken Canaga gave is barely used as the racer blew it stack so tire set up beyond race freshness, yet it leaks in so many area's it almost foam covered like above. I'll use it up learning the slow speed tire spins I need at speed so good to have air station to keep it up.
Tubeless on spoked rims ain't so straight forward and keeping it on the rim with flats is the least of it.

Can ya imagine light sharp handling that invites ya to power into decreasing radius turns for the pure glee so much so ya just make em all feel like decreases because the G's forces increase the whole way around and out. That one of the wonders of Brit engines they torque like crazy long enough to tackle turns - even if not the hp to pull to highest speeds in the opens.

Tire beads or liquids extra mass inside over lap some with this subject. I see reports and told by Commando users they definitely feel more secure in handling turns not just smoother balance, though that can't be separated.

It strikes me that although there may be some theoretical point where the weight of the wheel is so low that it creates problems, it is unlikely to get there with conventional stuff. I put a set of new alloy Morad/Akronts on the Vincent, saved about three pounds per wheel and cant feel any noticeable difference. I know it has to be a little quicker accelerating and braking, and also must take a bit less effort to steer. I mainly wanted them for strength, prior to this we were breaking a lot of spokes, two up plus luggage.

Perhaps some twitchiness might show up with the ultralight carbon fibre BST wheels, those are the only type I have heard this complaint about. Those wheels are considerably below the weight of a traditional light weight alloy, spoked type Norton wheel.

Glen

Ain't no Norton or Vincent OD size carbon fiber or beryllium alloy rim I know of, and one thing i'm sure of is every 17" dia wheels/tire are more twitchy than 18 or 19" when pressing their edges hard, so maybe that's what being noticed, they had to convert to 17" size, ugh no wonder they didn't like it and we don't see more of that sillyness in our innately nice ballet handling BI, till frame oscillations gets in the way. When they fit 16.5" wheels are they scooters or motocycles?

hobot said:

Ain't no Norton or Vincent OD size carbon fiber or beryllium alloy rim I know of, and one thing i'm sure of is every 17" dia wheels/tire are more twitchy than 18 or 19" when pressing their edges hard, so maybe that's what being noticed, they had to convert to 17" size, ugh no wonder they didn't like it and we don't see more of that sillyness in our innately nice ballet handling BI, till frame oscillations gets in the way. When they fit 16.5" wheels are they scooters or motocycles?

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Anyone experiencing the 'frame oscillations' that hobot frequently mentions, should have a look at, (if you haven't already done so) 'Worlds Straightest Commando' via Google. Also please have a look at my web site, http://www.parallelengineering.co.uk. Carrying out the recommended work will see an end to your 'frame oscillations' - guaranteed! PS I'm aware some photo's require amending on my website.

Sorry to say Al but a straight perfect made Commando only helps to assemble easier and isolate sooner not much help to its innate floppy eared scary handling. I ran modern robust frames into oscillation too, just hits at higher loads than a un-tamed Cdo can take and more suddenly and at higher freq. and too often w/o warning. Peel's frame was about dead on, and the mis-manufacture of engine surfaces squared to each other too but still ran into THE Hinge w/o the rump rod, the top and front links helped smooth the ride sense but did not stop the wobble/weave onset at some point. Believe me or not i'm not the one missing out but have no more concerns worries or thoughts to better handling -beyond the dangerous unpredictable moderns- so just lightening up and adding MO Power to have more fun faster. I've had pow wow's with Ken Augustine and he told me his process to sharpen up Cdo handling involved shortening the wheel base by taking up the space between engine and tranny, which surprised his race riders and the competition, but of course ran out of hp in the wide opens. I gave up trying to even practice Peel's lines and speeds on my SV650 as can't even take the loads required to enter like Peel let alone go on around like her. Nothing else can satisfy after that and no work out athletics involved either.

IRRC Peel's new front wheel with brake rotor and 100 size tire but tubleless came in ~32 lb. Rear is about 10 lb more.

So 74 lbs for front and rear combined then. Are these stock rims?
The GSXR wheels I used on the special are 48 pounds for front and rear complete with their very large but tubeless tires, rotors, sprocket etc., so 26 pounds less than your Norton wheels.
I would like to replace these stock GSXR rims with forged magnesium, this will reduce the combined weight by about ten pounds to 38 pounds total. BST carbon fibre wheels will knock another four pounds off that, but this is perhaps where the twitchiness comes in. Wallet hand twitchiness for sure, maybe the bike too.
So we can do a lot of weight reduction to the stock setup before getting anywhere close to a modern tubeless lightweight design.

Glen

These rims and tires came in at 40lbs for the pair.


I just built up some stainless rims/spokes for my combat.


I should have weighed the stock rim versus the stainless ones.

Brent, to get apples to apples, the weights I listed (and I think Steve's are as well) are complete, sprockets, bearings spacers, axles, rotors and all carriers.
Wheel weight only of forged magnesium is 5 lbs front, 8.5 lbs rear. Hard to imagine, but Carbon fibre are lighter yet.

Glen

Brent, there is an obvious difference between your bike and mine - the offset on the fork yokes. With that much trail, it will probably always be safe to lighten the wheels to the practical limit of materials. With my bike, riding it I get the message loud and clear not to take it for granted. Even tyre pressures could be a factor in the worst situation where it could tie itself up in knots and crash me. It is brilliant to ride, however I suspect it is at the limit of the geometry for quickness and self-steering.

Ken, all genuine Seeley frames have 27 degree head angles, how much offset are you using on your fork yokes ?

Dang it - I didn't go all out and try to find real Mg cast wheels like brent bragging on. Just more time/money if I live long enough. There may well be an optimal 'extra' mass for a particular frame and tires but also the extra lighter wheels may just be handling so extra well you are able to add energy enough to be entering what I call phase 3 and 4 where no matter what one or the other tires is letting go some. This can cause forks to snap to real road following instead of a kind of counter steering tire dragging angles. This is a mystery factor i will face working up my bragging rights on Peel. Not too concerned though as was amazed at all the various loads thrown at Peel at once w/o any weird unpredictable actions. Shop around for me and if coming across nice WM2 19" front and WM3-4 rear in 18 or 19 and also a 16" WM5 I may have to go into debt jumping on em. I go by the G's forces on my body so hopfully lighter wheel testers can tell that way. Twitchy is too scary for me anymore.

Hobot, with a road racer it always pays to go fast slowly, and work up to speed. Practice makes perfect.

acotrel said:

Ken, all genuine Seeley frames have 27 degree head angles, how much offset are you using on your fork yokes ?

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Alan, I think you are confusing me with that other Ken, Kenny Cummings, who races a Seeley, and who hasn't posted to this thread (yet). I raced Commando-engined bikes in Commando, featherbed, and custom frames, but never a Seeley. I owned one for a while, but never raced it. But to answer your earlier question, steering head angles ranged from 24.5 to 28 degrees, with different yoke offsets to suit. I've raced other non-Norton bikes with head angles from 23 degrees to 30 degrees. In general, steeper forks make the bike quicker to turn in and flick from side to side, while the opposite tends to give more stability at high speeds. That's assuming you get the yoke offsets right keep the trail in a fairly narrow range. Trail is the significant parameter, not the fork angle. That's pretty basic chassis info, and I'm sure you already know all that.

I did do some experiments with Commando frames, cutting and welding to change the steering head angle. Bringing it back from the stock 27 (28 for 850s) degree angle to 26 seemed to be the sweet spot for racing, along with less offsest in the yokes to bring the trail back. Going steeper on the head angle made the bike much quicker to turn in, but seemed to make it really prone to high side, so I didn't pursue that any further. It's important not to over simplify this sort of modification. Keep in mind that besides steering head angle and yoke offset, I also was trying different ride heights front and rear, different wheel and tire combos, different rear shocks, different front forks, varying shock and fork settings, different swing arm lengths, and so on. It's all a trade-off, and there is no one setup that's the best for all riders and all tracks.

Ken