Handling & Suspension 2004-2008

It's a suspension issue.

I think I'll just tape it and call it good.

I shouldn't be looking at that thing any way.

I seems like the only time I look at it is when I going 80mph or when I hit a steep boulder section.

It defenitly needs tape.

bushie

after respoking the rear, new rimlocks and a new HD tube: the rear is ready to go with a one tooth taller gearing at 49 x 14. this would have pushed the rear wheel back but i have removed a link and it has infact come forwards 10mm.

wheelbase is now 1450 which is 25mm shorter than standard. the rear flap was removed and an old knackered one put in that has been cut off to stop 2" over the swingarm. ride height sag of 102 instead of 97. as the jetting is crisp I hope the bike will pull well and 'rock' both back and forwards under acceleration and braking.

suspension wise I have got rid of the basevalve pistons that had the three holes in them and bought two more and drilled just 1 x 1.15mm in each and swopped the stacks over. that's all I've done up front and the rear is as described above.

regards

Taffy

handling with the wheel forward and just a 1450 wheelbase - 40mm less than standard and a massive 50mm/2" less than the WR yams.

but the bike is now well balanced and excellent over table tops etc. it dips nicely under braking, hooks up nice and squats accelerating out of corners. I have both shock and forks that are travelling too far but I'm working on it!

tests now will centre on
fork height - for tracking into corners
from that if it doesn't tie with acceleration squat i will use this eccentric heim.
then we are into different engine mounts and swing arm lugs in the back of....

regards

Taffy

after several tests I made some improvements to the handling.

to recap I found that I couldn't get the bike to drop into corners with the standard 22s, a change to 18s changed this and it drops in so well and quickly that I was able to up the gearing by two rear teeth.

well having found the right rear sag for REAR steering on exit - to be 103mm (or so) I had to set the front. this is for loam and harder soils, moist but not sand for sure.

the forks are the original 2002s and as such are 5mm shorter than later bikes. where the WP factory added that 5mm I don't know: upper or lower leg? the legs were held at an imaginary 3rd line (the factory leave you with 2) and so i raised the clamps to line one and after many suspension changes and tests I still couldn't make my mind up! each line is 2mm apart so I raised the clamps 4mm.

gearing makes a big difference, if a track has a single rut in a long arc, you must match the bikes gearing and revs to that arc. this is bloody hard but at the end of the day sometimes the bike would understeer and sometimes over steer. I tried lowering the forks one last time and the result was similar but this time I had to run a taller gear or definately fall in. that is HARD!!!

this brings me to two conclusions:
1) I have always geared the bike for 2nd gear on slow corners with a huge gap to third that come courtesy of the enduro WR gearbox. this makes you always struggle. so I'm going to go back to low gearing and try and use 3rd gear for slow/medium corers whilst 2nd becomes a hairpin gear and there will always be a 4th gear corner somewhere. it's going to be hard to learn because I KNOW second gear, its like a friend to me.

2) that because I'm under and over steering so much the answer may be to go to a 19mm or 20mm set of TCs. 20s are cheaper as they are halfway twixt the two used so far. I think I have too much steering at the moment.

19s???? anyone ever seen them?

we continue

regards

Taffy

Taffy,

I think you need a 650, then the gearing issues go away, just need a dab of clutch perhaps and its in the sweet spot.

Steve

I think one year of the new engine has 19s

well my new one has the code 18-20 on it and the way to go is 22s they say. which I have sat here of course!

and I have a 400 that needs 20s........ :!: :!:

cool

so the 18-20s are 19s with the 1mm offset

hmm so if you can organise a zero offset stem you have 19 as well :wink:

yep! and I have the engineer for the job! does 4-10 hours a week for me.

regards

Taffy

Just bought a set of SMR TCs for a Katoom. 18/20 offset. and as you say...I can go straight down the middle for 19s!

testing will continue apace this weekend.

regards

Taffy

Ok, I have to cover a little of the suspension here as they overlap but essentially I had to work the forks hard before I could even think about the handling.

but if you read to the bottom you'll see I've discovered a great bit of info....

I put the adjustable SMR560 clamps on at 20mm and also changed the gearing to 13 x 49 (and not 14 x 49) which extended the wheelbase by around 7-8mm if all added up. 1458 then... with slightly more weight going on the front.

also I've been running 45mm of handlebar lift and I decided to go to 25mm with the new bars so this will also have added to the front.

the forks were through by just the two lines. I also have to confess that I have the problem of a weak rear stanbdard damper which requires the closing of the LSC to help support the shock over chop and pretty much everything to be honest!

this affects the rear squat leaving corners and I was having real trouble with the bike climbing over ruts.

so I spent the first part of the day setting the suspension for RIDE and then loosened the rear LSC by 18 clicks and got that nice squat back.

so the 20s allowed the bike to drop into the corner and didn't need over or under correcting when holding a berm. on accelerating initially it was everywhere and lifted up so you'd close the throttle etc but at least the actual use of the steering was RELAXED again.

I dropped the clamps to 3 lines showing as the rear was so low and this helped a little and the bike tracked well again. but I could still feel that if I opened the throttle hard, that the bike changed its geometry.

SO, THEN....
I finally decided to change the engine position. It all stems from this photo of an old works bike from 2005/6.


If you look closely the engine belly is parallel to the frame unlike all production bikes. So I had engine plates made a few months ago and have been waiting for the right moment. and yesterday was the right moment. I have lifted the engine about 7mm at the front which is 2mm at the gearbox sprocket.

what a difference!

as i left the corners under power the bike just steered straight ahead, no throttle/seat/body movement, just open the throttle! the rear shock just holds still and you get on with riding! remember that when cranked over a bike that changes shape is changing its steering.

work on the rear shock will facilitate good suspension AND good dip at the rear when exiting corners and I can't wait! next time I'll concentrate on tidying up:
rear wheel forwards with one extra tooth on the rear = change the balance and wheelbase
the sag rear for best suspension
best fork height for steering
best LSC (rear) for dip exiting corners

get all that lot sorted and see what comes out of the pot.

BTW, no riding next week as we will be getting shifaced in a pub as we watch Englands glorious win over the Aussies at the old rugby union. of course if the totally unrealistic happens and England lose I may well be perfectly sober and ride (as if....)

regards

Taffy

altering chain pull moment :thumbup: :thumbup: nice innit?

if you ever get too much then its possible to have the shock set up so soft it still corners nice but then it wallows with the power off

GMD came up with a special chain tensioner system to optimise the chain/engine geometry that lowered lap times considerably on the sbks but the Jap factory at the time wasn't interested because it "in theory increases friction"

Taffy said:

Englands glorious win over the Aussies at the old rugby union

regards

Taffy

Click to expand...

In your dreams Taffy :twisted: :twisted:

sorry lads,i'm not really getting this swingarm angle stuff.
:? taffys leaning the motor back & raising 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?
bushy ,i still don't quite understatnd how you are increasing your swingarm angle,if you went from 460mm stocko to 450mm now? dunno must be missing something?
the end of the swing arm can't change height because of the wheel.haven't you now got a flatter swingarm angle than before?
..weed..

450 is the minimum that works for me. I prefer 460 but I want the bike low as well.


I have run it at 430 on the first modded frame and it sucked. the steering head angle was nicer and I got the trail increase I needed but the seat was too low at the back and the swingarm angle screwed up the traction on accel, the rear wrould not hold up nice with the power on (too much squat) and comming into corners the rear would swap just like it was packing, a tap of the rear brake on corner entry also did nothing with the swingarm pivot at 430mm (no brake jack)

sometimes chain pull moment is called anti squat,

this came up from a quick search

http://www.sportrider.com/tech/146_0404 ... index.html

hey Taffy If I read it right you just raised the sprocket 2mm ? so the swingarm angle is unchanged right?

thats right. I'm getting my three ducks in a row. the big difference in just 7 laps of a MX track was LEAVING the corner under hard acceleration. the bike just sat dead still................

I'm so you used to yawing and going onto opposite lock, straying out of the rut so on and so forth.

I have also had eccentric crankcase shoulders made so i can lower the rear directly.

I have the original photo from the magazine of that bike and there is no phucking way that that SA pivot axle has been mowed. no way!

even thought the front is up 7mm I can't see whether the case is now parallel due to the weekends mud. when I get it cleaned I'll have a look. I can jack the engine again at the front by 4 to the power of (just under) 1 or I can go straight to the engine shoulders which are (just under) 1 to the power of 4. they are 2mm eccentric so that'll be about a 1.4mm drop!

the weather is turning fast here but luckily the track I choose to practice at drains well.

I have checked and double checked the angle of the shock in the photo and again - no way is that shock at a different angle - no way!!!!

so I think what has happened is that they have worked out the best angle of the three axis and when they got it the shock was too long or too short and all they have done is stuck the small top heim in an eccentric housing in the bottom and lowered/raised the shock. YOU CAN'T LOWER AND RAISE YOUR RIDE HEIGHT WITH THE SPRING PRELOAD.

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.

I have known these facts all along but I have to get the suspension right first. I'm close and that's why I'm starting to make chassis changes and started this thread. It's like a helix and I'm working my way to the centre.

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

regards

Taffy

Taffy said:

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.

Click to expand...

so Taffy wanted less anti squat

with the paddle grip and acceleration from all the grunty horses I need more chain pull moment than I had with the swingarm pivot at 430mm

he also wants steeper forks, more weight on the front and a tiny amount of trail 8O so we've set our bikes up almost polar opposites! what a crackup

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?

what I've done is to neutralise it by hopefully putting all three in a row.

regards

Taffy

You two being confuseing is getting old.

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..