Handling & Suspension 2004-2008

Taffy · Nov 9, 2010

we have a fundamental disagreement here then over what happens.

if the rear wheel spindle is below the three point line then you get the wheel driving into the ground by lifting the seat. this in no way can be described as squat but anti-squat yes. the opposite to what your saying. I don't believe the sprocket size has a bearing although i may be wrong. it's simply where the three axis are.

regards

Taffy

Taffy · Nov 9, 2010

I've now read the article and the one thing it doesn't tell you is the ORDER of all those changes. the sprocket sizes for instance mean half of phuq all. but even a numpty can work out by default that a 55t rear is going to cause more force than a 35t simply due to gearing and power applied. all in all though gears do little.

the real difference is where the three axis are with you sat on it. you have to remember that opening the throttle causes anti-squat popup and that changes the shape of the bike and if you aren't a top rider it leaves you trying to be 'delicate'.

I've got to chase this through as I say and I must firstly get more free valve on the rear compression to get squat leaving the corner. up until now the rear wheel has been fighting it: anti-squat from the rear wheel versus as it happens a shock with the comp screws closed.

I'm a great believer in 'doing what it needs next'.

for instance, all I've done is set the sag at 102mm. now the range is between 85-100 on the 2001-2003s and it's 90-105 on the 2004-2008s. I felt that the suspension was 'nice at that. one ring off the preload and it hurt! one ring on and the bike was great but no squat and impossible to ride as I was always facing the outside ropes. follow that weed?

so it could be that if I use my eccentric bush in the shock to lower the ride height but add it back by putting one ring on the preload that I'm happy! who says 7mm was enough? who says 7mm up at the front and 2mm down at the back aren't enough?

I have the original magazine scan of that bike and if you or Damon want to read it again I'll send it but it was in the archives of the old site. so you see I hadn't jacked the rear yet the bike was far, far better! imagine if I HAD jacked it to a race sag of say 90mm what it would have been?

one other thing Damon (Bushie)
I'm not quite sure why you think I want weight on the front? I don't read all you write and I'm sure you don't read fully sometimes what I do but I had one real problem and that was that I couldn't get the front down! It would not dip for corners!

so I drilled those BV pistons, dropped the clamps, lowered oil levels: I DID EVERYTHING! so I don't actually want weight on the front. infact I want the opposite in a way! I have to jam the rear wheel forward to get a balanced chassis but end up with a bike 2" shorter than a WR450..........50 friggin mm!

then when I went to 18mm Yokes I got "dip"! now I can't stop the friggin thing "dipping" on slow LSC stuff. however ride height in general is now excellent. all this stuff I've kept in my pocket...

I'M A DARK HORSE YOU KNOW!
A MAN OF FEW WORDS!
A MAN OF GRAVITAS (not gravel arse!) :lol: :lol: :lol:

tomorrow I'm preparing two shocks for the next ride to go with the one on the bike. anyone have a spare DCC????? I have FC/MX shock with only MCC?????

anyway, we'll see!

regards

Taffy

bushmechanic · Nov 9, 2010

one other thing Bushie
I'm not quite sure why you think I want weight on the front? I don't read all you write and I'm sure you don't read fully sometimes what I do but I had one real problem and that was that I couldn't get the front down! It would not dip for corners!

:dontknow: did I write that more than once ? was mostly you and then weed wasn't it ? youve often written you want more weight on the front

popup said:
the swing arm angle by 2mm.sounds about 2 parts of f all.
by doing that you are puting more weight on the rear wheel,by shifting the top of the motor back.(which is what i like & the opposite to what you want? i thought you were trying to put more weight on the front?[/quote]

Taffy said:

what do you define as squat?

as I leave the corner with the preload jacked the bike lifts the seat under acceleration which is great for grip when bolt upright but tell me how you deal with that when fully cranked over? you call it anti-squat? it never 'squated' anyway?

Click to expand...

squat is the compression of the rear suspension under acceleration or simply when you apply power. it makes no difference if the bike is fully cranked over or not in my conditions I can apply WOT mid corner with the inside bar end kissing the sand. I also have steering geometry that still works sensationally with the swingarm fully extended.

I have a paddle trye with bolts, tons of grip, 100kgs bike and 68kg rider and 70+HP = plenty of acceleration
so compared to you Taffy its is little wonder I need more anti squat right ?

this is the clincher though Taffy.... if you have more anti squat you can have a plusher rear for breaking bumps

steve · Nov 9, 2010

Fantastic discussion.

IMHO, sprocket size does matter. You don't have to change the gearing, but by going up or down at both ends to keep the gearing the same you change the leverage that the chain pull has around the swing arm pivot.

BMW is the latest to try to eliminate it all together with the 450, and now Husky have inherited it. Bimota's SB2 did it years ago http://www.bimota-enthusiasts.com/models/sb2/sb2.htm

Others have tried it using a range of idler pulleys around the swingarm pivot. It seems fine tuning the 3 axes is the way to go, and using sprockets adds to the equation.

Steve

bushmechanic · Nov 9, 2010

popup said:
ok, good article.it only makes sense really when you have a good think about it.
dunno bloke,but i think you have it wrong? :?
if you are having traction problems on exceleration,that is not enough rear wheel loading.
high swing arm angle works against squatting of the rear(less rear wheel loading).
lower the swingarm angle so it pulls closer to the horizontal plane,that way,there is less anti-squat.(more traction)
if you have too much squat when accelerating out of corners,the bike will keep on running too wide.
high seat height & high c.o.g of the motorcycle will increase the squat(more rear wheel loading) but increases all rolling chassis movements (same for braking,it loads up the front suspension more,more than a bike with lower c.o.g)
obvoiusly there are better ways to make a bike squat for more rear wheel loading & traction.
large rear sprocket & small front will increase the anti-squatt of high swingarm angle.it will keep wanting to pull the end of the swingarm downwards(anti-squat).
too stiff in rear spring or too much comp on the rear also adds to anti-squat(less traction)
forks that are up through the triple clamps too far,takes weight off the rear making it harder to squat & hook up.
my bike sitting staticly on the ground has about 320-325mm ground clearance 420-425mm to centre of front sprocket,of course i have lowered the bike.
with swingarm angle flatter than stocko & both fuel tanks adding more weight to the rear of course, i have no problems with traction coming out of corners.heaps more traction than stocko & much more fun.
like the article says,under power with the suspension deeper in the stroke, with the swingarm beyond the horizontal,the power is working negitively with the suspension,trying to bottom it out.thats where the rising rate link & progressive spring can counteract that.
the way i see it in theory,with my swingarm angle so close to the horizontal.the best thing i can do is have a progressive rear spring & a small back sprocket & a large front one.correct?
correct me if i'm wrong,i'm sure you will.
..weed..

hey weed

im not sure how you get more traction with the s arm pivot lowered, I got the weight transfer concept and sure the weight is back with a flatter swingarm but when the wheel is fully extended its extended less so over bigger bumps it will have less chance of touching the ground as often and the chain pull/anti squat is reduced so as a percentage of the accel force you get less force pushing the wheel into the ground and less traction.

maybe it comes down to how much acceleration you're getting as to how much traction you need ? on a flatter harder surface perhaps its more citical to have the weight back and down ? accel chop here quickly becomes 2 ft rollers and the sand is like powder so the more down-force the better to keep the wheel following the ground and throwing as much dirt as possible out the back

Ive lowered a few bikes other than mine by shortening the shock, with flatter swingarm angles they allways have less traction and don't turn in as nice under brakes they are mostly for hardpack MX though.

perhpaps we're thinking too much

I tried a few different angles sprocket sizes etc and have a good setup, both you and taffy have completely different setups again but we are all getting what we need so .....

what id really like to see is how a 50mm swingarm extension will work on one of the new bikes. one of the problems mentioned with the new chassis is fore/aft pitch and yaw, a longer swingarm and broader chain pull moment window (see article) might help

Davo · Nov 9, 2010

bushmechanic said:
perhpaps we're thinking too much

Need you Bushie, Weed and Steve to organise an 2011 Oz Force ride, Handling and Suspension can be one of the topics discussed after dinner drinks.
Force Ride should coincide with Azza's ride so we can cheer him on somewhere, or cheer him accross the finish line.

Taffy · Nov 10, 2010

seems popup is thinking that the weight transfer back under hard acceleration takes priority but infact the anti-squat completely runs the show. also as has been said, the more anti squat you run the more viscious it becomes. the mild zone is with the three axis lined up.

sorry bushie but these bikes don't handle with severe anti-squat no matter how much help you think you get. it's good for a straight line drag. that's it.

anti squat becomes SQUAT under hard engine breaking and far from following the braking bumps it would rather be heading up to the 3AL where the effect is gone. your bike has specific needs whereas I'm simply trying to make mine go round an enduro/MX track as fast as possible in all conditions except soft sand.

regards

Taffy

bushmechanic · Nov 10, 2010

Taffy said:
seems popup is thinking that the weight transfer back under hard acceleration takes priority but infact the anti-squat completely runs the show. also as has been said, the more anti squat you run the more viscious it becomes. the mild zone is with the three axis lined up.

sorry bushie but these bikes don't handle with severe anti-squat no matter how much help you think you get. it's good for a straight line drag. that's it.

anti squat becomes SQUAT under hard engine breaking and far from following the braking bumps it would rather be heading up to the 3AL where the effect is gone. your bike has specific needs whereas I'm simply trying to make mine go round an enduro/MX track as fast as possible in all conditions except soft sand.

regards

Taffy

sorry bushie these bikes don't handle with severe anti-squat no matter how much help you think you get

Taffy old son I think you're missing the point.

squat is directly related to the degree of acceleration and it matters not if you are in a straight line or accelerating mid corner.

depending on the acceleration and acceleration alone you need a certain amount of anti squat to combat the acceleration induced squat

in fact combating the squat during cornering is far more important than combating the squat in a straight line. Ive never had an issue with straight line squat because the steering isn't as important in a straight line drag but during cornering you need the swingarm geometry to work against the squat so the rear doesn't bottom out with the power on..... if the back doesn't hold up with the power on you loose corner speed.

anti squat becomes SQUAT under hard engine breaking and far from following the braking bumps it would rather be heading up to the 3AL where the effect is gone

this is 100% wrong, engine braking or braking same thing the swingarm tries to fully extend, its called brake jack, if it doesn't have enough you get the rear swapping side to side.

ive done the testing on it

your bike has specific needs whereas I'm simply trying to make mine go round an enduro/MX track

simply eh? doesn't sound like it

my bike has the same needs as your bike just in different amounts.... not rocket science that bit.

popup · Nov 10, 2010

bushmechanic said:
[

hey weed

im not sure how you get more traction with the s arm pivot lowered, I got the weight transfer concept and sure the weight is back with a flatter swingarm but when the wheel is fully extended its extended less so over bigger bumps it will have less chance of touching the ground as often and the chain pull/anti squat is reduced so as a percentage of the accel force you get less force pushing the wheel into the ground and less traction.

maybe it comes down to how much acceleration you're getting as to how much traction you need ? on a flatter harder surface perhaps its more citical to have the weight back and down ? accel chop here quickly becomes 2 ft rollers and the sand is like powder so the more down-force the better to keep the wheel following the ground and throwing as much dirt as possible out the back

what it comes down to bushy,is the different riding we do.
bush/woods/forestry riding that i do, is completely different to your mx track.
of course accelerating out of a flat gravelly corner with a front heavy bike or a bike set up with increased anti-squat
is useless for what i do.the rear end would be going from side to side like clothes on a clothes line in a 40 knot breeze.i need the rear to squat a little more ,bite in & find traction.i know it works for me.

i can see now why you want so much anti-squat accelerating over rollers etc,the rear would blow through too quick ,blog & then the rebound would throw ya. you really need a link for what you are doing.

popup
if the g/box axle is below the line through the middle of the other two it will make the bike stand up at the rear leaving a corner. far from helping it destroys your line. if all three are in a row it is neutral and if the g/box axle (centre point) was ever above the other two it would actually pull the rear wheel up under the seat when accelerating.
hey taffy ,i have never tried this,but its just another way of adjusting the squat or anti-squat.
good thinking :idea: now i understand what you are doing.
maybe bushy might try that one for more anti-squat?

Taffy said:

seems popup is thinking that the weight transfer back under hard acceleration takes priority but infact the anti-squat completely runs the show. also as has been said, the more anti squat you run the more viscious it becomes. the mild zone is with the three axis lined up.

thats too broad a statment for me to agree or disagree.
depends on the bike set up.like we were saying...
soft suspension on a heavy bike with a high c.o.g is completely different to say a light mx bike with firm suspension.
the anti-squat will only "run the show" if you set the bike up that way.
..weed..

Click to expand...

Taffy · Nov 10, 2010

my point is that you gotta understand what takes first priority! what does the most to your bike. transfer of weight is as nothing compared to the 3AL. and sprockets count even less.

and bushie your still wrong! when you close the throttle the sprocket is trying to run up the lower chain so it wants to jump up under the seat! because it can't fight gravity and it also has you sat on it and a spring pushing down it doesn't stand much of a chance but it is trying! it only has one allie and that is weight transfer to the front leaving it dangling with a chance to be mischevious!

it is trying to send the swing arm pivot down to the ground, thats why you get braking bumps otherwise all rear wheels would just drag soil towards the corner but they don't do they!

thats why road racers have a tie rod from the brake caliper to the frame independant of the swing arm. this stops rear wheel judder and bounce. consider the anti squat under braking to be like a cat on a hot tin roof.

regards

Taffy

bushmechanic · Nov 10, 2010

Taffy,

regarding engine braking and jack !

in order of greatest influence

1 swingarm angle
2 chain pull moment

when you work out why it makes absolutely no difference where the output shaft is located vertically unless its on the swingarm (BMW) then we can start to have a dialouge.

as it stands your fundamental understanding of the forces involved is all over the place, moving the output shaft simply moves the front of the chain, same effect can be had from changing sprockets

breaking bumps are a result of resonance.

the force resulting from the swingarm angle is orders of magnitude more significant than the chain pull moment. your swingarm height 460, mine 450... for all we know our bikes may have the exact same anti-squat. :?

and for acceleration

Note that the chain pull always creates an antisquat tendency

Ive tried a flat swingarm angle and tested the effect on braking. your explanation is WAY off for dirtbikes.

heres why: during acceleration the rear is compressed. during braking the front is compressed, for corner entry its nice to have a little dip at the front to help turn in. a tap of the rear brake on corner entry gives the bike a kick up the rear through the shock in turn further compressing the front and helping with turn in. the force is upwards yes but the weight transfer is what counts here. with little to no weight on the rear the brake jack force is simply transmitted through the shock into the frame pitching the bike forward. the steeper the swingarmn arm angle the bigger the upward force. the nett effect of applying the rear brake is a transfer of momentum and an upward force that brings the wheel off the ground thus extending the swingarm.

bushmechanic · Nov 11, 2010

on the off chance anyone is really really struggling for entertainment :wink:

heres my explanation of why our bikes turn in nice with a tap of the rear brake, ie brake jack rather than squat as Taffy insists occours

bushmechanic said:
during acceleration the rear is compressed. during braking the front is compressed, for corner entry its nice to have a little dip at the front to help turn in. a tap of the rear brake on corner entry gives the bike a kick up the rear through the shock in turn further compressing the front and helping with turn in. the force is upwards yes but the weight transfer is what counts here. with little to no weight on the rear the brake jack force is simply transmitted through the shock into the frame pitching the bike forward. the steeper the swingarmn arm angle the bigger the upward force. the nett effect of applying the rear brake is a transfer of momentum and an upward force that brings the wheel off the ground thus extending the swingarm.

I have some textbooks with detailed vector diagrams of swingarms etc and in a long winded way they describe how certain geometries can give genuine brake jack as opposed to squat. if im bored Ill do some diagrams of the husaberg rear, its irrelevant really becasue everyone has at some stage experienced better turn in by tapping the rear brake.

googling the appropriate terms .. brake jack and instant centre showed up this stuff.

so a link for F+ to read, after that he can change his nic to B-minus

http://www.rotorburn.com/forums/showthr ... xplanation.

popup · Nov 11, 2010

holy $hit bushy,thats way over the top for this country bumpkin :shock:
i'm still trying to get over the last link you sent us.

interesting but confusing.
next ride i will be that comsumed in what the bike is doing under power & under braking,i will probably get lost.

bushy ,at this rate,you will be the cause of the formation of brain tumors amongst us .:twisted:
i will try to add to the conversation when i learn/absorb a bit more,until then, i will say nothing for fear of sounding like a knob shinner 8O
..weed..

bushmechanic · Nov 11, 2010

hey Phark that just ride :twisted:

the main thing to note is that for acceleration it does not matter where the output shaft is vertically ..... only the position of the chain at the top of the front sprocket. making the front sprocket bigger is the same as raising the output shaft

also something perhaps lost in the to and fro dribbling above is that my swingarm pivot is at 450mm! Taffy with his at 460 would have to raise the front of his sprocket about 20mm to reduce anti squat as much as I have by lowering the pivot. He's raised it 2mm so :?

the anti squat is better on my mochine with the sarm at 460 But the COG is too high, I went to 450 as a compromise and tipped the engine forward 60mm at the front, this lowers the COG again and puts the top of the chain at the same height as a 14-13T front and I run a 53T rear so I got some of the anti squat back but not all of it.

Like I said my bike works good, your bike works good, Taffys bike works good we've all used swingarm geometry to get what we want.. thats great isn't it :?

as I see it the point of this stuff is being able to tune your bike to do what you want it to do, generalising and saying these bikes don't work with setup X or Y is rediculous.

Taffy · Nov 13, 2010

bushmechanic said:
Taffy,

regarding engine braking and jack !

in order of greatest influence

1 swingarm angle
2 chain pull moment

when you work out why it makes absolutely no difference where the output shaft is located vertically unless its on the swingarm (BMW) then we can start to have a dialouge.

as it stands your fundamental understanding of the forces involved is all over the place, moving the output shaft simply moves the front of the chain, same effect can be had from changing sprockets

breaking bumps are a result of resonance.

the force resulting from the swingarm angle is orders of magnitude more significant than the chain pull moment. your swingarm height 460, mine 450... for all we know our bikes may have the exact same anti-squat. :?

and for acceleration

Note that the chain pull always creates an antisquat tendency

Click to expand...

Ive tried a flat swingarm angle and tested the effect on braking. your explanation is WAY off for dirtbikes.

heres why: during acceleration the rear is compressed. during braking the front is compressed, for corner entry its nice to have a little dip at the front to help turn in. a tap of the rear brake on corner entry gives the bike a kick up the rear through the shock in turn further compressing the front and helping with turn in. the force is upwards yes but the weight transfer is what counts here. with little to no weight on the rear the brake jack force is simply transmitted through the shock into the frame pitching the bike forward. the steeper the swingarmn arm angle the bigger the upward force. the nett effect of applying the rear brake is a transfer of momentum and an upward force that brings the wheel off the ground thus extending the swingarm.

only about 4 words are right here. I can see Taffy, Bushmechanic, quote and quote again so you got 4 words right.

however as you talk like a k-talk girl and are about to throw your dummy out of the pram bushie I won't speak of it anymore.

you know I'm going to try reducing the travel of this rear shock especially the dangle off of jumps etc. I get the feeling that I'm going to have quite a bit of shock travel that is unused. as hard as I have looked at that photo of the works bike and the so called 'repositioned shock' I don't think they have but to get full shock travel, to get it at a greater SPEED over its full travel: would it not have paid the factory to have shunted the shock back 1cm? same angle just like 1cm back or even 2cm back.

with the headstock forwards (and I take it the rear going back the same amount) that would have left room for this. of course they could have made the shock work fuller/faster/harder by jacking it over at an angle - ala katoom - with an extension of the swing arm forwards of the shock mount and before the S/arm pivot? or a higher and further back bolt mount on the swing arm?

regards

Taffy

bushmechanic · Nov 13, 2010

Taffy you rude bas@#$%^rd

draw some force diagrams then you will see whats going on

if you're going to say ive got it all wrong at least make some attempt to show in a logical way where you think I have gone wrong.

I don't mean a full page of Taff dribble I mean a lucid rational argument with pictures or links showing why you think the output shaft location is different to altering sprocket size and why you think this (from the link)

Note that the chain pull always creates an antisquat tendency

is also wrong. you also need to explain why the rear suspension fully extends when you tap the rear brake as you turn in, im not shitting you it actually does.

I am Quite Happy to be wrong.. would just like an explanation of your theory(s) that makes sense. thanks mate

steve · Nov 14, 2010

Taffy said:
free T-shirt (UK FR1) to you Steve if the Aussies win!
regards
Taffy

Ah well, it seems humble pie is the order of the day.

Just found out the result. Been in Vic riding this last weekend, 975 kms in 3 days on the DR down to Dargo and surrounds. They don't have an interest in Rugby down there, so had to wait until I got home to find out.

Congratulations,
Steve

Taffy · Nov 15, 2010

steve said:
Taffy said:

free T-shirt (UK FR1) to you Steve if the Aussies win!
regards
Taffy

Click to expand...

Ah well, it seems humble pie is the order of the day.

Just found out the result. Been in Vic riding this last weekend, 975 kms in 3 days on the DR down to Dargo and surrounds. They don't have an interest in Rugby down there, so had to wait until I got home to find out.

Congratulations,
Steve

I'm so pleased with the way they played, we've been in the dark more or less since we won the world cup. also we are trying to ween ourselves off WW! trenches style drudgery and forward domination before we move the ball. need to take risks more often like the anzacs do.

when we do them they are risks, when the french do them they are 'inspired' when the anzacs do them it's 'natural'! the grass is always greener on the other side as they say!

regards

Taffy

Taffy · Nov 21, 2010

ran with the plates again today and in the first sessions I got dialled in and without the LSC screw bing over 20 out there is no dip on the rear.

first test was on an FC shock I have rebuilt. I put the 85/111 spring across and had trouble fitting the collar. although the shock looks the same length = it isn't! it seems to be shorter.

cocking my leg over the seat was real easy! with the rear down by an unspecified amount with the three axles possibly in the reverse curve it meant that every time i opened the throttle the bike ran straight into the inside rope. talk about over steer!

I should have put the standard plates back on if i'd had them there. I'm now certain that the bike has to have been developed around the Fc with its short shock and not as an FE at all. either that or they were told by the cost cutters that they couldn't have seperate plates for the FE. anyway, i got it to handle by having the forks 13mm through the clamps but without a DCC on the rear shock i had no dip.

also whilst the bike falls into corners lovely, when you go to open the throttle the bike just walks straight out the top of a rut. this could be deemed to be under steer but to me its just a total lack of rear squat. makes a fool out of anyone that...

regards

Taffy

bushmechanic · Nov 21, 2010

also whilst the bike falls into corners lovely, when you go to open the throttle the bike just walks straight out the top of a rut. this could be deemed to be under steer but to me its just a total lack of rear squat. makes a fool out of anyone that...

ahm how can lack of squat make the bike climb out the top of the rut?

a bike with too soft HSC on the comp will climb out the top of the rut becasue the back squats too much.... dial in the HSC on the shock to combat squatting and it tracks perfectly

BTW IF what you want is less anti squat whats to stop you lowering the engine 10mm at the front and shortening the shock to flatten the sarm

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