Any idea why?

[beyond]

Just a thought (second time this year). :)

I've noticed this for some time and it's even apparent on photos taken from the side of the road. One of my riding buddies mentioned it the other day as well and he rides a GSXR1000 and was following me for a bit.

When cornering, my GSX1400 does not seem to have the same lean angle as a full on sportsbike, for the same corner, at the same speed. This of course is good for me as it means the hard bits don't touch down so early. BUT, why does a sportsbike have to lean more than mine to get around a corner at the same speed?

Is this a wheel base/physics thing? Weight? Seems a bit strange but it is apparent.

Any ideas from the weight versus mass versus wheelbase, cornering phyics specialists out there??

[dnos]

i wont say im an expert, any physics knowledge i did have is pretty much forgotten since high school.
But i think weight would have a lot to do with it. and perhaps the centre of gravity being higher or lower?
Would be interested to hear this from the experts meself

[98tls]

seems strange eh....maybe its tyre profile....i have tried both 180 and 190 rear tyres and there is a difference on turn in....just guessing really...will be interested in others theories.

[Devil]

But i think weight would have a lot to do with it. and perhaps the centre of gravity being higher or lower?

This is the reason.
For the extreme example, follow a cruiser. Really low weight and they hardly lean at all compared to a sprots bike.

[BNZ]

Heavier wheels as well maybe? Something about a rotating mass having resistace to move yadi yada :whocares:

Ouch, thought too hard

[sAsLEX]

Your off track there I think with the weight issue, the reason cruisers dont lean in corners as much is they cant you start decking stuff out

I think the real reason lies more in the wheel base coupled with the tire and how that makes the bike turn

[Devil]

Your off track there I think with the weight issue, the reason cruisers dont lean in corners as much is they cant you start decking stuff out


Follow a cruiser, even a small one like crashe's which doesn't have a long wheelbase and you'll see how much more you have to lean than she does at the same speed on the same corner.

Weight is a factor, but also where it's carried.

[McJim]

The whole objective of lean is because of the combined vectors of gravity and centrifugal force acting on the bike. Since both of these vectors owe a lot to the weight and the weight distribution on the bike the key factors have to be it's mass and centre of gravity.

Travelling in a straight line the only lateral force is Gravity - hence the bike is upright. As the bike turns the centrifugal force comes in to play. The greater the mass/speed or tightness of the turn the greater the centrifugal force applied and the more lean required to maintain balance to ensure the bikes wheels point to 'virtual down' (being the combined direction of the 2 vectors of Gravity and Centrifugal Force)

That's the application of logic but doesn't seem to prove the fact - the heavier bike had LESS lean....not more.

[sAsLEX]

Follow a cruiser, even a small one like crashe's which doesn't have a long wheelbase and you'll see how much more you have to lean than she does at the same speed on the same corner.

Weight is a factor, but also where it's carried.

So a 300kg bloke on a r6 (would look silly but this is a mind exercise) would therefor ride like Crashe?

There is also the rake and trail of the forks which affect the interaction of the tire and its apparent radius with the road which would again have more affect than weight on its own.

So thats is a good point I jsut raised, your forks/ ride is more relaxed as is a cruisers than a GSXRCBRRRZX whatsit, maybe this is the answer to your question

[Masterchop]

I have noticed a similar thing.
When following my mate on his Aprillia and me on Ducati, going the same speed (fairly quick) I lean alot more than him.

I put it down to wheel base and steering geometry,but only guessing.

[Drunken Monkey]

The whole objective of lean is because of the combined vectors of gravity and centrifugal force acting on the bike. ...


OMG! It always makes me laugh when someones tries to come accross all 'physics expert' and then says the word 'centrifugal'...

I would have to say "combined vectors of gravity and centrifugal force" is the best faux-science I've seen for a while. LOL, nice one!

Edit: For those who still don't get it: From Wikipedia-

Common misunderstandings
... should not be confused with centrifugal force. The centrifugal force is a fictitious force that arises from being in a rotating reference frame. To eliminate all such fictitious forces, one needs to be in a non-accelerating reference frame, i.e., in an inertial reference frame. Only then can one safely use Newton's laws of motion, such as F = ma....

[sAsLEX]

The whole objective of lean is because of the combined vectors of gravity and centrifugal force acting on the bike. Since both of these vectors owe a lot to the weight and the weight distribution on the bike the key factors have to be it's mass and centre of gravity.

Travelling in a straight line the only lateral force is Gravity - hence the bike is upright. As the bike turns the centrifugal force comes in to play. The greater the mass/speed or tightness of the turn the greater the centrifugal force applied and the more lean required to maintain balance to ensure the bikes wheels point to 'virtual down' (being the combined direction of the 2 vectors of Gravity and Centrifugal Force)

That's the application of logic but doesn't seem to prove the fact - the heavier bike had LESS lean....not more.


Confusion and misconceptions

Centrifugal force can be a confusing term because it is used (or misused) in more than one instance, and because sloppy labeling can obscure which forces are acting upon which objects in a system (which is true for physics in general). When diagramming forces in a system, one must describe each object separately, attaching only those forces acting upon it (not forces that it exerts upon other objects).

One can avoid dealing with pseudo forces entirely by analyzing systems using inertial frames of reference for the physics; and when convenient, one simply maps to a rotating frame without forgetting about the frame rotation, as shown above. Such is standard practice in mechanics textbooks.

Because rotating frames are not vital for understanding mechanics, science teachers often de-emphasize the centrifugal forces that appear to exist in a rotating reference frame. However, in their zeal to stamp out the misunderstanding of the term in this one case, they may try to expunge it from the language entirely.

Try to avoid centrifugal force as the basis of an argument as it is a rectionary force to the Centripetal Accelleration and force one undergoes in cornering

[McJim]

OMG! It always makes me laugh when someones tries to come accross all 'physics expert' and then says the word 'centrifugal'...

I would have to say "combined vectors of gravity and centrifugal force" is the best faux-science I've seen for a while. LOL, nice one!

That's cool cos I piss myself laughing when I see people using 3 letter acronyms!

Buwahahahaha

Now tell me my first post wasn't a troll.

[sAsLEX]

3 letter acronyms!
.

Thats TLA to you son.

[Drunken Monkey]

...Now tell me my first post wasn't a troll...

Okay, "your first post wasn't a troll!"

:P

[Pwalo]

I'd go with wheelbase, combined with steering angle and perhaps tyre profiles.

Ok I really don't know and can't be bothered to try and recall my high school/university physics. You could work on trajectory change, braking dynamics, weight, chassis bias, reider weight, etc, but I'm pretty sure that getting a simple equation would be problematic at best.

Also you must remember that a lot of this is pretty subjective. You always feel more cranked over on a sportsbike because of the riding position, c of g, etc. You also look more 'tucked in' which further enhances the image of leaning over.

[sAsLEX]

I have noticed a similar thing.
When following my mate on his Aprillia and me on Ducati, going the same speed (fairly quick) I lean alot more than him.

I put it down to wheel base and steering geometry,but only guessing.

Now this adds to the puzzule as surely, if he is on a race rep Ap as well, the rake and trail of your two bike are similar....... hmmmm

[Drunken Monkey]

Is one rider hanging off the seat more or less than the other? I have found hanging off the bike moves your weight enough that you can turn in the same radius with the bike more upright. While at the track this is exaggerated, you might find that only a slight shift of the bum is all that's required to make 2 apparently similar dimensioned bikes to turn the same radius with different lean angles.

[Fishy]

Is one rider hanging off the seat more or less than the other? I have found hanging off the bike moves your weight enough that you can turn in the same radius with the bike more upright. While at the track this is exaggerated, you might find that only a slight shift of the bum is all that's required to make 2 apparently similar dimensioned bikes to turn the same radius with different lean angles.

I don't think Beyond was shifting his weight (I don't think so) but I was sitting square in the saddle. We were both two up and riding at a medium pace.

[beyond]

Yeah, had my missus on the back so wasn't doing any moving around at all, just sitting in the middle of the seat normally. I also know sports bikes riders are more tucked in with more weight over the front, but lean angles for them are still more severe when you look only at the bikes actual lean angle and not the rider.

[sAsLEX]

Yeah, had my missus on the back so wasn't doing any moving around at all, just sitting in the middle of the seat normally. I also know sports bikes riders are more tucked in with more weight over the front, but lean angles for them are still more severe when you look only at the bikes actual lean angle and not the rider.

This brings it back to rake trail and wheelbase then as weight though your ride would be a little more we have excluded the use of your body hanging off to shifting the CoG of your bike inward to alter the cornerning characteristics.

GSXRthouh
Overall Length: 2030mm (80.0 in.)
Overall Width: 710mm (28.0 in.)
Overall Height: 1130mm (44.5 in.)
Seat Height: 810mm (31.9 in.)
Ground Clearance: 130mm (5.1 in.)
Wheelbase: 1405mm (55.3 in.)
Dry Weight: 166 kg (365 lbs.)

GSXR1400
Overall length 2100mm (85in)
Overall width 810mm (31.9in)
Overall height 1140mm (44.9in)
Wheelbase 1520mm (59.8in)
Ground clearance 130mm (5.1in)
Seat height 790mm (31.1in)
Dry weight 228kgs (502lbs)

Indication of your weights combined passenger weight on each bike?

Oh and anyone got rake and trail for these bikes?

[Motu]

Now this adds to the puzzule as surely, if he is on a race rep Ap as well, the rake and trail of your two bike are similar....... hmmmm

Have a read of Foales chassis book - he has a nice little diagram there to explain it.Wider tyre profiles require the CG to be higher,or move inward with the contact patch - that is why you slip of the seat and move your body to the inside of a turn,to put the CG over the contact patch.I don't need to with my skinnier tyres,I can stay on the seat and just lean.So I think it will be CG and tyre profiles that are making the difference.

[idb]

I'd expect tyre profile to be the most likely the difference in your example as the bikes are fairly similar and neither rider is climbing off much.

[Fishy]

Indication of your weights combined passenger weight on each bike?

Oh and anyone got rake and trail for these bikes?

Combined weight on the 1000 is about 145kg's.

[sAsLEX]

Have a read of Foales chassis book - he has a nice little diagram there to explain it.Wider tyre profiles require the CG to be higher,or move inward with the contact patch - that is why you slip of the seat and move your body to the inside of a turn,to put the CG over the contact patch.I don't need to with my skinnier tyres,I can stay on the seat and just lean.So I think it will be CG and tyre profiles that are making the difference.
Thats was along the lines of what I was thinking also, but surely rake and trail would come into it as this determines where the contact patch is?


I'd expect tyre profile to be the most likely the difference in your example as the bikes are fairly similar and neither rider is climbing off much.


Would the tire profiles therefor be not too dissimilar?

[Fishy]

Would the tire profiles therefor be not too dissimilar?

I am running standard sized tyres...

120/70/17F
190/50/17R

[beyond]

Combined rider weight for me and my missus 140kgs.
I'm running Metzler Z6's 190 rear.

I think Fishslayer is running Pilot Powers with a 190 rear???

[beyond]

GSX1400 full specs

Technical Specifications
Overall length - 2,160mm (85.0 inches)
Overall width - 810mm (31.9 inches)
Overall height - 1,140mm (44.9 inches)
Wheelbase - 1,520mm (59.8 inches)
Ground clearance - 130mm (5.1 inches)
Seat height - 790mm (31.1 inches)
Dry mass - 228kg (502 lbs)
Engine type - 4-cylinder, 4-stroke, air/oil-cooled with SACS, DOHC
Bore x Stroke - 81.0 x 68.0.mm
Max. power - 106 ps @ 6,800 rpm
Max. torque - 126 Nm @ 5,000 rpm
Piston displacement - 1,402cc
Compression ratio - 9.5 : 1
Carburettor - Fuel injection 34mm
Lubrication - Wet sump
Ignition type - Electronic ignition (Transistorised)
Starter system - Electric
Clutch - Wet multi plate
Transmission - 6-speed, constant mesh
Drive system - Chain
Front suspension - Telescopic, coil spring, inner cartridge, spring preload adjustable, rebound and compression damping force 12-way adjustable
Rear suspension - Swingarm, oil damped, coil spring, spring pre-load hydraulically adjustable, rebound and compression damping force 4-way adjustable
Rake/Trail - 26 degrees / 105mm (4.1 inches)
Front brake - 6-piston calipers, dual disc brake
Rear brake - 2-piston caliper, disc brake
Front tyre - 120/70 ZR17 tubeless
Rear tyre - 190/50 ZR17 tubeless
Fuel tank capacity - 22.0 litres
Colours - Blue/White, Blue, Silver

[The_Dover]

Combined weight on the 1000 is about 145kg's.

*cough* bullshit.

You gotta be 105 on your own, tubby.

[sAsLEX]

I am running standard sized tyres...

120/70/17F
190/50/17R


Combined rider weight for me and my missus 140kgs.
I'm running Metzler Z6's 190 rear.

I think Fishslayer is running Pilot Powers with a 190 rear???

So tire profile is out of the equation.

Weight is still there but only a diff of 55ish kgs so not that excessive.

back to rake and trail and chassis set up, maybe GoG, fishys would be alot higher what with the higher pegs and his mrs perched up there on the pillion seat.

[Fishy]

*cough* bullshit.

You gotta be 105 on your own, tubby.

Don't be jealous mate, just cause you're built like a siberian endurance racing insect.

[beyond]

GSXR1000 rake and trail are 23.45 degrees and 96mm

[The_Dover]

Don't be jealous mate, just cause you're built like a siberian endurance racing insect.

Hey buddy, you need a big hammer to drive a big nail.

[sAsLEX]

GSX 1400
Rake/Trail - 26 degrees / 105mm (4.1 inches)



GSXR1000 rake and trail are 23.45 degrees and 96mm


a reasonable difference there I would say.

<img src=http://www.jeris-springer.com/trail.jpg>

[Fishy]

Hey buddy, you need a big hammer to drive a big nail.

Can't have a big party under a small marquee.

[eliot-ness]

Couldn't the answer simply be that sports bike riders tend to turn in later than tourer riders, thus tightening up the corner and requiring more lean at the same speed??? Had a brother who, riding an identical bike, regularly scraped the pegs when I didn't, yet was traveling at the same speed. He was the same height and weight and the bikes were set up the same.

[Drunken Monkey]

Good point mr prohibition enforcement dude. If I'm bored and the pace is slow I will definately wait and turn late to make the corner more 'interesting', so although the bend of the road is no different, the line of each rider through the bend can be. In saying that, aren't we talking about different lean angles given speed AND line are constant?

[beyond]

In saying that, aren't we talking about different lean angles given speed AND line are constant?

Correct, same lines, same corner, same speed, different lean angles.

[Fishy]

. In saying that, aren't we talking about different lean angles given speed AND line are constant?

Speed through the corners and lines through the corners were the same.

[Motu]

So tire profile is out of the equation.
.

It's the CG over the contact patch that determins the lean angle - so the 1400 will have the CG higher and so require less angle of lean.

[Ixion]

I think you're right, intuitively. Weight up high means less lean needed. But that conflicts with the "choppers need less lean angle" theory?

[Edbear]

Ah! You guys get so comlimicated overlymuch! It'sall 'bout STYLE, Darlinks!:sunny:

Sumtimes I leans a lot, sumtimes I leans a little but most times I make it 'round ze bends anyways...!:yes:

[idb]

It's the CG over the contact patch that determins the lean angle - so the 1400 will have the CG higher and so require less angle of lean.

Which is also affected by tyre profile.
The fatter the tyre, the further the bike has to be leaned as the contact patch moves further away from the centreline of the bike.

[Ixion]

Just to complicate matters - is it the static CoG we are talking about here or the dynamic centripetal centre of mass ?

[Motu]

Which is also affected by tyre profile.
The fatter the tyre, the further the bike has to be leaned as the contact patch moves further away from the centreline of the bike.

As the contact patch moves inward,the CG has to follow,the higher the CG the less it has to move.The opposite is the case with narrow section tyres,with narrow section tyres a lower CG gives less lean.Total confusion eh?

If no one comes up with the diagram to explain,I'll scan my Tony Foales book tonight....after Dr Who.

[07fatboy]

This is all too confusing for me...too many big words

[idb]

...with narrow section tyres a lower CG gives less lean.....


I don't follow that statement at all.
I can understand that less lean is needed for narrow section tyres given the same height of CoG but I can't understand why that would reverse the actual effect of the height of CoG on lean.

[MacD]

The Engineers on the site might be interested in this research group (http://www3.imperial.ac.uk/controlandpower/research/portfoliopartnership/projects/motorcycles)at Imperial College, London.

Somebody has even produced a GSXR1000 (http://www3.imperial.ac.uk/controlandpower/research/portfoliopartnership/projects/motorcycles/programs) simulation.

I'm sure the answer to the original question is in there somewhere! Who wants to find it? ;)

[Back Fire]

I would pin it down to your insane ability to hang off the bike like a monkey... a monkey that can make a tank move faaarkin fast mind you...

[MacD]

If no one comes up with the diagram to explain,I'll scan my Tony Foales book tonight....after Dr Who.

Motu, did you know Tony Foale has a website (http://www.tonyfoale.com/) (mainly as a promo for his book)?

However you can download some of his older articles, the one on camber thrust (http://www.tonyfoale.com/Articles/Tyres/TYRES.htm) is probably the most applicable to the question.

As for Dr Who, I enjoyed the Cybermen last week, definitely the second most scary adversaries after the Daleks! :niceone:

[Motu]

Thanks for that,a lot of that stuff is out of his chassis design book,but the illustration I want is not there....and I can't scan it because it has to go through my wife's computer and she's busy working on it.Fig2.31 is the one I want.

''... shows how the contact patch moves away from the centre plane of the wheel or steering axis as the machine is banked,giving rise to the following side effects:

a) A greater angle of lean is necessary to balance centrifugal force;this may involve a higher centre of gravity to restore cornering clearance.''

[Ixion]

Motu, did you know Tony Foale has a website (http://www.tonyfoale.com/) (mainly as a promo for his book)?

However you can download some of his older articles, the one on camber thrust (http://www.tonyfoale.com/Articles/Tyres/TYRES.htm) is probably the most applicable to the question.

As for Dr Who, I enjoyed the Cybermen last week, definitely the second most scary adversaries after the Daleks! :niceone:

Well, I read that and understood it (I think). But I don't see how it answers the original question.

Or the subsequent question. Does a crusier, with a very low CoG and very wide tyres need less lean angle for the same corner speed and radius than a tourer with a high CoG and skinny tyres?

EDIT. this is a very interesting thread

[Motu]

Or the subsequent question. Does a crusier, with a very low CoG and very wide tyres need less lean angle for the same corner speed and radius than a tourer with a high CoG and skinny tyres?


Jeez,I can't even think that through,it's like tomato sauce on apple crumble.I can't imagine how those chops with the phaaaat back tyres and skinny front tyres go around a corner,the contact patches would be 150mm out of line,and the CG would be inside the contact patch - you'd have to countersteer them to buggery.

After twins and singles all my life,the CB750 came as a hell of a shock when I got it in 1985 - it handled fine,but if I hit a bump mid turn the bike would rip the bars out of my hands and stand up,I was getting scared of it! I couldn't use my usualy ploy of lower wider bars,but finaly figured it out.The higher CoG than I was used to was tossing the bike out of the turn,so I started to toss the bike deeper into the turn,or drop a cheek and get to the inside....destroyed my Ago style.The same style of bike I had been riding,the same tyres - but it definetly needed more angle of lean than the XS1.

[Fishy]

I would pin it down to your insane ability to hang off the bike like a monkey... a monkey that can make a tank move faaarkin fast mind you...

Neither of us were hanging off.

[McJim]

a) A greater angle of lean is necessary to balance centrifugal force;this may involve a higher centre of gravity to restore cornering clearance.''

Bugger! I got my arse kicked for using that terminology on this thread.

[Lou Girardin]

Elliot-ness has probably got it. Were you both using identical lines?
A classic racing line requires less lean angle than someone who turns in late and squares off the corner.

[Motu]

Bugger! I got my arse kicked for using that terminology on this thread.

Direct quote from Tony Foales,they can't touch me on that one!

[McJim]

Direct quote from Tony Foales,they can't touch me on that one!

Yeah but wait till they have a go at Tony Foale :rofl:

[Ixion]

It's not just the height of the CoG, its also the offset sideways. Velos were reckoned good handling because of their very narrow engine design. The early fours were reckoned poor handlers because of the width of the engine putting weight to far outboard. I think this is probably particulaly significant on bump steer, the overhanging weight becomes a pendulum if you hit a bump when leaning.

And what about those slip angles and the SIZE of the contact patch? Since the front and rear weels follow different paths and both are describing a circle (whilst the wheels are rigidly fixed in the frame, ie we are not talking hub centre steering) the tyres MUST have to distort to allow the wheels to "follow" each other. So if the contact patch is very large (and distortion resistant) do you need more lean (a greater alpha angle, steeper sides to the invisible cone) to compensate?

[Fishy]

Were you both using identical lines?

Lines were the same, speed was the same.

[sAsLEX]

Yeah but wait till they have a go at Tony Foale :rofl:

Tony Foale is wrong there. But he is writing for layman like you who like the word and find comfort in its simplicity, rather than pure physics.

[MacD]

I think it may be something to do with slip angle as well. Variation in slip angle seems to be the reason that you need to lean a bike more as you increase speed for a constant radius corner. I did have a good site bookmarked previously but I can't find it at present. It was a comparison of cornering on a sportsbike using different riding styles/angles of lean. I think it was relevant to the lean angle question.

The issue of centrifugal force is debatable. As you said yourself sAsLEX it depends on your frame of reference. While it may not be a very rigorous use of terminology, it is still a useful concept, particularly if the bike (accelerating around the corner) is your reference. Although Wiki is a debatable source at times it does seem to cover the issue (http://en.wikipedia.org/wiki/Centrifugal)relatively well.

[Motu]

Tony Foale is wrong there. But he is writing for layman like you who like the word and find comfort in its simplicity, rather than pure physics.

The difference between a theoretical engineer and a practical engineer.

The smartest guy I have ever come across in automotive engineering couldn't pronounce half the words he tried to teach us - but he wasn't teaching us the correct terminology,he was teaching us to understand the principles of how and why.If you know how something works...words just become that,words.

[Jantar]

In a turn the tyres are providing the required centripedal force that makes the bike change direction. There is a countering centrifugal reaction (which can also be correctly termed centrifugal force) that would needs to be overcome by leaning the bike so that the combined vectors of gravity and centrifugal force act through the centerline connecting the contact patches of both tyres.

There can not be a centripedal force without an associated centrifugal force. So in this argument Tony Foale is correct and Wikipedia is out.

However back to the original question, the bike with the longer wheelbase, narrower tyre profile and higher CoG will require less lean angle for the same line through the bend at the same speed.

[Lou Girardin]

Lines were the same, speed was the same.

Well, it sounds like you're a lot porkier than Paul and have to get all that mass low enough to get around.:yes:

[Fishy]

Well, it sounds like you're a lot porkier than Paul and have to get all that mass low enough to get around.:yes:

Must be all my protein shakes and creatine.