Skinny vs fatso tire cornering

Flo said:

Well, Fullauto, my usual ride is a 167BHP k1200s, which has a 190x50 rear tyre. This thing handles superbly.

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Well, the K1200S has been designed to handle nicely with a very low CoG in mind. Just take a look at how low the whole structur of the bike is with the engine sloping that much - in total it's a brilliant concept. However there is a reason that the S1000RR follows a completely different pattern closer to the Nippon opposition. Race bikes have a pretty high CoG because they don't really care about handling but high speed stability. A high and front-ended CoG on a motorcycle is only bad for braking but they win far more on cornering speed than they loose on braking. It was pretty interesting to see where the Ducatis put their tungsten when the FIM was trying to balance out the 750 HoYaSuKa superbikes against the mighty L-twin.


Tim

I remember a few years back, one of my mates took a manx, still on 19" tyres to a modern trackday at Cadwell park, out with big Dukes, 7/11 GSXRs etc.......he was 4 secs a lap quicker than anything else there!!

Seeley920 said:

I remember a few years back, one of my mates took a manx, still on 19" tyres to a modern trackday at Cadwell park, out with big Dukes, 7/11 GSXRs etc.......he was 4 secs a lap quicker than anything else there!!

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Rider, not bike.

swooshdave said:

Seeley920 said:

I remember a few years back, one of my mates took a manx, still on 19" tyres to a modern trackday at Cadwell park, out with big Dukes, 7/11 GSXRs etc.......he was 4 secs a lap quicker than anything else there!!

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Rider, not bike.

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Both....I've been racing for 30 years, I should know!! Manxes are capable of higher cornering speeds than lots of modern bikes, Supermonos, Rob North Tridents etc.....try coming to a race meeting. The fastest lap of the weekend usually goes to a 500 single, not an unlimited bike....same rider before you come back with some response!!!

Yeah, bloody 500 singles.
Thought I was going fast along some lanes a few years ago, until a Venom came hurtling past me.

I remember a few years back, one of my mates took a manx, still on 19" tyres to a modern trackday at Cadwell park, out with big Dukes, 7/11 GSXRs etc.......he was 4 secs a lap quicker than anything else there!!

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Both....I've been racing for 30 years, I should know!! Manxes are capable of higher cornering speeds than lots of modern bikes, Supermonos, Rob North Tridents etc.....try coming to a race meeting. The fastest lap of the weekend usually goes to a 500 single, not an unlimited bike....same rider before you come back with some response!!!

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Well there ya go, ONLY advantage of best elites is top speed straight line full upright acceleration to top speed. I already know this and have lost all respect or awe of the screaming angry looking insects a real motorcycle can snap up like tadpole bait confused by slight bends in their path hehe haha HOHOHO.
Get them into a real turn with leans over 45' and they have to slow up to
1st or 2nd and tip toe around in very limited choice of lines to commit too.
[Snickering smirking sheet eating grinning by ole obsolete Cdo rider here]

So appears skinny tires matter most in corners over hp or mass or pilot skill.

Thank goodness for modern advances in brakes or there would be nil fans to support turning track races as they'd have to creep up on corners so slow.
Consider that best examples of over powered corning ability is found on speedway racers and they don't have brakes. But to me on rod linked Ms Peel,
speedway racers seem too unstable to handle the chassis loads and tire conflicts to be able to straight steer chicanes and sweepers like ice spiked bikes do, so flat tracker style with a foot down is just lazy dazy low thrill waste of time and traction to relieve bike and pilot loads into wide slide. Pashaw.

Imagine a 500 thumper mass isolastic Commando that hooks like a 125 but has more torque power per mass than about anything fielded that leans so far.
Next subject to explore is effects of chassis resonance on narrow arc of rim edge tyre patches + power pulse frequency. Flexy vs Rigid deserves its own subject line discussion.

My fat tire test disappointments




My tyres that pleased me to point boots needed re-treads.




Don't yet know if I could stand the corner G's full street tire narrow tread
may grip. I hear tales full tread street tires are used to help in sharp
tarmac turns, sounds intriging enough I'll buy a set for next time out on Peel.

hobot

Fullauto said:

Danno said:

Flo said:

Well, Fullauto, my usual ride is a 167BHP k1200s, which has a 190x50 rear tyre. This thing handles superbly.
But, on corners up to around 80mph, I can get the Commando around them faster. It actually, as you say, feels nicer.
I do have conversations with other people about this, & of coarse, they don't believe me.
Just wish I could get rid of my high speed weave, which is the only thing that lets the Commando down.

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Fork Brace

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More like rear isolastics and swingarm bushes I would think.

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Wish it was, that would be easy.

Fullauto said:

Danno said:

Flo said:

Well, Fullauto, my usual ride is a 167BHP k1200s, which has a 190x50 rear tyre. This thing handles superbly.
But, on corners up to around 80mph, I can get the Commando around them faster. It actually, as you say, feels nicer.
I do have conversations with other people about this, & of coarse, they don't believe me.
Just wish I could get rid of my high speed weave, which is the only thing that lets the Commando down.

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Fork Brace

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More like rear isolastics and swingarm bushes I would think.

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When Cycle tested the Commando back in the early days, the late Gordon Jennings commented on it's fine handling-except in switchbacks, where the fork would wind up and unwind like a spring, causing the bike to wallow like a pig. Smoothness was the key to keep the weave at bay, but any cornering G-forces strong enough to compress the suspension made it near impossible to avoid. A fork brace is about the only thing worth trying, because a stiffer front end would only transfer the force to the steening neck, leading to frame flex.

When Cycle tested the Commando back in the early days, the late Gordon Jennings commented on it's fine handling-except in switchbacks, where the fork would wind up and unwind like a spring, causing the bike to wallow like a pig. Smoothness was the key to keep the weave at bay, but any cornering G-forces strong enough to compress the suspension made it near impossible to avoid. A fork brace is about the only thing worth trying, because a stiffer front end would only transfer the force to the steering neck, leading to frame flex.

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Yep a number of items and issues must be modified on an isolastic Commando for its supreme handling manners on narrow meats to show up. Once Roadholder stiffened and spring rate and dampers spiffed up just the nuance of slider vibration on the stanchion bushes can show up on far over fast leans on textured surfaces. Other than that I know a Commando that suffers none of the upsets everyone else Cdo's do plus their modern garage mates must back off for.
Tyre issue solved by above testimony of past and current witnesses. YEA!
So only Chassis - flexy vs rigid vs inbetween dampened articulated, remains to resolve for a world dominating nil effort totally neutral handling isolastic
Command.

Don't even think about steering dampeners for the very tights or to recover a wide sweeper upset. Front tire, until lifted out of traction, Must follow the road travel line within ~10% max slip angle. Think Flat tracker dolly wheeling front
to have no resistance to the CoG line of rear drive.
If bike needs a crutch of a steering dampener, then absolute evidence its a corner cripple with someone on it trying to exceed its innate deficiencies.

Hope someone else that enjoys such excess catches on to more than catch up
on skinny tyre obsolete cutie pie rubber baby buggy Norton Commando!

hobot

ludwig said:

Interesting topic .
I can't explain it as well as Tintin , but with a little understanding of Physics , it is evident that weight in itself has no influence on lean angle .

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Isn't there a great weight difference between the two bikes?

Believe it or not I've done my own experiments following and riding various two wheelers from tiny low CoG scooters to top heavy two up Goldwings.
I find there's about as much difference in lean angle and fork angles as there are in various types of cars, tiny tire short wheelbase to large tires long wheel base.
Duh until tire Slippage occurs, all their tires just follow in line behind each other.
In other words regardless of the motorcycle it just like cars some need a bit more or less steering angle to get same turn radius per speed but its withing same range of difference as not quite right air pressure in tires, not a significant difference.

What does significantly differ in cycles tire size is how far a bike can lean over before fouls, tires let go on leans or bike get unstable at high speed. I like to drift and kick my wife's Honda 250 scooter around on the grass and THE Gravel but boy howdy I can't get away with that much over 20-30 mph. Tends to hi side leaned and tires squirm above 85 mph interfering with smooth line inputs by pilot.
But the tiny tire scooter is quicker turning up to sluggish speeds real racers do in tight chicanes so of course the misguided modern elites now run scooter size tires that were once outlawed in early vintage racing d/t unfair advantage.
Similar said about Mini Coppers by Ferrari and Jaguar racers, If God intended them to go around so fast he'd of given them bigger meats.
http://www.youtube.com/watch?v=6NU_4bY_ ... re=related

hobot

Ludwig — where is the road?

The chicken strips — I wonder is it to do with the difference in width between the WM4 110 rear and the WM2 90 front? When I had a 190 section rear on the Sukuki, it had a narrow chicken strip even with hard riding on the track. This disappeared completely with a 180 fitted, wearing right to the edge. Then again I have roughly the same tyre/rim combination as yours on my Seeley and no chicken strips. Or maybe it's because you don't have to lean as much for the same corner speed as your bro. Some riders may not lean as much but have quicker turn-entry and turn-exit speeds, thus keeping pace with a rider who leans more in the apex. Maybe it doesn't matter if you can get down the mountain as quickly as the other guys!

If you look at the profile of a 100/90 19 on a standard 1.85 inch rim (WM2) there is no way you will ever get to the edge of the tread because of the profile. Put the same tyre on a 2.5 inch rim and check out the difference. The profile will be flatter with more tread on the road at any lean angle. Wider tyres on narrower rims make the profile more mushroom in shape. This would be why the 180 had no chicken strips but the 190 did. On the same rim, the 190 would be higher, but not necessarily wider.

Revealing feed back to me. Stock Commandos foul center stand or pegs before full tire edge reached. With stand gone and rears sets the silencers scrap before full chicken touched. A lifted Commando can remove the stripes of 110 on a WM2 rim
and 120 on WM3 rim.

What pleases me so very much more on 110-120 18" vs the jump to 160-+ 17"
is the traction does not decrease nearly as much or as fast when on edges of 110-120 as it does on the fatter tires. Beware jumping straight from a handy spunky skinny tire cycle coming off a canyon run and go back the other way on a fatso shod power house.

hobot

hobot said:

What pleases me so very much more on 110-120 18" vs the jump to 160-+ 17"
is the traction does not decrease nearly as much or as fast when on edges of 110-120 as it does on the fatter tires. Beware jumping straight from a handy spunky skinny tire cycle coming off a canyon run and go back the other way on a fatso shod power house.

hobot

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Felt similarly when I had my 750SS Duc comparing to my ZXR750R. It really was more fun and easier to work the slower bike at speed than the powerhouse. The powerhouse required much more smoothness on throttle and brakes because of the shear power involved. I was faster on the slow bike without the same fear of loss of traction,(and consequences). Slow bike fast vs. fast bike slow. Probably why I also like Supermoto and dirtbikes. Just say'n. Or maybe I'm out in the weeds...

I was faster on the slow bike without the same fear of loss of traction,(and consequences). Slow bike fast vs. fast bike slow. Probably why I also like Supermoto and dirtbikes. Just say'n. Or maybe I'm out in the weeds...

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Alrighty Will we see bike life the same way wring everything ya can out of but never over do to ever get scared. Terror will find you regardless of your style so why invite extra loads of it to you.

The secure ease of my rear linked Commando whether creeping in woods or flinging supermotard tights is simply uncanny. Every other bike including stock Combats takes some athletics to press near max. Not ole Ms Peel - Only thing that may worry ya is blind hazards directly in your face or running out of power to accelerate harsher on entry. Acceleration is exactly like drugs or sex, keep needing more to get the same high. Straight sprints are only one G vector, throw in a bigger vector to center of turn, Whooweee that's fun as is gets
with your clothes on w/o fear of loss of control.

Every bike I get on I soon find how far it can lean then what lean loads before tires let go some, then power+lean skip outs and stay within those for sane ride.
I've not been able to foul lifted Peel nor find tire angle skip outs but on THE G.
Hi Power+Far lean+Sharp fork turn is needed to force Peel to loose grip on pavement but it just screws her in tighter not flung wider and no sense of rebound in chassis that just unwrapped or forks that just untwisted.
Sling shot-ish to Ricochet Rabbit-ish.

I tell you truly its a huge leap of faith to taste best hot fat race tires on a track and then get to that point on a Commando hardly breathing hard and grit teeth
to really nail in some power and nothing happens but wrist stretched, butt squashed as turn sharpens and blood flushes down brain stem to rear patch.

Now if an isolastic Commando could just not give up much if any thing after the apexes to hi HP fat tire bikes and be novice easy to handle, yum.

hobot

willh said:

hobot said:

What pleases me so very much more on 110-120 18" vs the jump to 160-+ 17"
is the traction does not decrease nearly as much or as fast when on edges of 110-120 as it does on the fatter tires. Beware jumping straight from a handy spunky skinny tire cycle coming off a canyon run and go back the other way on a fatso shod power house.

hobot

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Felt similarly when I had my 750SS Duc comparing to my ZXR750R. It really was more fun and easier to work the slower bike at speed than the powerhouse. The powerhouse required much more smoothness on throttle and brakes because of the shear power involved. I was faster on the slow bike without the same fear of loss of traction,(and consequences). Slow bike fast vs. fast bike slow. Probably why I also like Supermoto and dirtbikes. Just say'n. Or maybe I'm out in the weeds...

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Watch a hill climbe & see how quick the dirt bikes get round the corners.

ohhh noooo Flo, its the off road that challenges me on Peel most.
On the dirt bike MX type tracks where they hook a U turn with a rooster tail jerk out of it >>> are Using Straight Steer because their rear tire is locked from slide out by the rut in the steep banked berm. If they tried to counter steer that sharp the front would wash out just like it does on tarmac racers.
Do note that fat tires are not used in corning off road events, just the sprints down a strip or up a steep slope. Both events go sour if leaned very much.

Notice too that they sometimes pull a sideways wheel out of the apex.
Can ya even imagine doing that in glee on a Commando? I can't shake it,
so aiming for more.

hobot

Hobot — Europeans must think you're a bit crazy to take your Commando off-road, but then we have to remind ourselves that the Norton P-11 and other such models were made for what you're doing. The only Commandos I've seen on the dirt on this side of the pond were in Sidecar Motocross. The Norton Wasp combination was well known in the 70s and early 80s.

We missed out on the great tradition of flat track that you have in the States. I guess you had a lot of gravel back roads, which is maybe how it developed? I used to read about the exploits of Norton riders like Dave Aldana in mags like Cycle and Motorcyclist. If I'm right, to win the coveted AMA No. 1 plate, one had to compete in all three disciplines: road racing, motocross and flat track/TT. This seemed to me to be the supreme test of a motorcyclist. I think it was one of the reasons why Kenny Roberts cleaned up when he came over to Europe — because he was comfortable on the dirt, he was able to slide his bike and that gave him an edge.

Notice too that they sometimes pull a sideways wheel out of the apex.
Can ya even imagine doing that in glee on a Commando?

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So you should be sitting with your b***s on the tank to get weight over the front so it digs in and allows you to break traction and slide the rear controllably? So you would need a Roadster or Hi-Rider tank with some padding, effectively extending the seat forwards? Just be careful!

Dave

daveh said:

Hobot — Europeans must think you're a bit crazy to take your Commando off-road, but then we have to remind ourselves that the Norton P-11 and other such models were made for what you're doing. The only Commandos I've seen on the dirt on this side of the pond were in Sidecar Motocross. The Norton Wasp combination was well known in the 70s and early 80s.

We missed out on the great tradition of flat track that you have in the States. I guess you had a lot of gravel back roads, which is maybe how it developed? I used to read about the exploits of Norton riders like Dave Aldana in mags like Cycle and Motorcyclist. If I'm right, to win the coveted AMA No. 1 plate, one had to compete in all three disciplines: road racing, motocross and flat track/TT. This seemed to me to be the supreme test of a motorcyclist. I think it was one of the reasons why Kenny Roberts cleaned up when he came over to Europe — because he was comfortable on the dirt, he was able to slide his bike and that gave him an edge.

Notice too that they sometimes pull a sideways wheel out of the apex.
Can ya even imagine doing that in glee on a Commando?

Click to expand...

So you should be sitting with your b***s on the tank to get weight over the front so it digs in and allows you to break traction and slide the rear controllably? So you would need a Roadster or Hi-Rider tank with some padding, effectively extending the seat forwards? Just be careful!

Dave

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If you look at pics of older flattrackers, that's how they did it, but since the Springsteen era, flattrackers have "railed the turns, only breaking traction long enough at the entrance to the turns to get the chasis set. The days of the broadslide are gone as this only slows you down.