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Suspension Set Up


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#1 Guest_GuyGraham_*

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Posted 16 August 2009 - 05:12 pm

Basic Suspension set up

First you’ve got to set your springs up
You can’t compensate for too soft or too hard springs with more or less damping
More or less preload will not make the springs harder / softer, they will only raise or lower the bike but it does have an effect on the feel of the suspension though (in reality, if you add 20mm of preload, the last 20mm of travel will be stiffer as it will require more force and hence why it feels it has made the suspension firmer)

The way to check if you have the correct strength springs is by measuring ‘sag’
A heavier rider will require stronger springs and vice versa a lighter rider will require weaker springs on the same bike
Motorcycle manufacturers have got a hard time and at best can only choose compromise for an average weight rider. If you’re not the same as the average weight rider they have chosen then the springs will be wrong, and the springs have a fairly narrow range rider weight that they will be correct for.

Sag

Terminology

Static sag – how much the suspension compresses with just the weight of the bike from fully extended (ie with the wheels off the ground)
Rider or dynamic sag – how much the suspension compresses with the weight of the bike and rider aboard
Loaded sag – is merely a calculation of rider sag minus the static sag to see how much the weight of the rider is compressing the springs


Front


Best method is to put a ty-rap around the fork stanchion

Measuring Static sag
Lift front wheel off the ground, and push the aforementioned ty-rap down to the dust seal on the top of the fork slider (for right way up forks on like on the TDM)
Gently lower the bike onto its wheels without it bouncing, then lift the wheel off the ground again
Measure distance from dust seal to bottom edge of ty-rap

Measuring Dynamic sag
Same as Static but this time with you sat on the bike – again do not bounce the suspension

Calculate the loaded sag by subtracting the static from the dynamic

Figures you are aiming for are (these are based upon sports bike suspension (120mm suspension travel), but as the TDM has a slightly longer suspension travel these may be a bit on the hard side

Static Sag 15-20mm
Dynamic sag 30–35mm
Loaded sag 10-20mm
So the MkII TDM850 front suspension travel is 150mm, so the following is probably a better starting point

Static sag you want is 60 – 70% of the dynamic sag
TDM850 MkII = 22.5 to 31.5mm
Actual Dynamic sag you want is 25 – 30% of full suspension travel
TDM850 MkII = 37.5 – 45mm

Actual Loaded sag range = 6.5 – 22.5mm

Rear

You will need a helper to do the rear
To do the rear you need to measure (with a tape measure) from the rear spindle or edge of swingarm (it doesn’t really matter) to a point on the rear of the bike, vertically upwards
If necessary, a piece of masking tape with a cross marked on it, stuck the tail piece will suffice. It must be vertical else you will get false readings

Do the sag measurements as per front above

Figures you are aiming for are
Static Sag 5-10mm
Dynamic sag 30–35mm
Loaded sag 20-30mm

Again, these are based upon sports bikes with shorter suspension travel than the TDM

MkII TDM850 has 144mm of rear suspension travel, so the following may be a better place to start

Actual static sag you want is 15 – 25% of the dynamic sag
TDM850 MkII = 5.5 to 11mm
Actual Dynamic sag you want is 25 – 30% of full suspension travel
TDM850 MkII = 36 – 43mm

Actual Loaded sag range = 25 – 37.5mm

What to do if you can’t get the Sag figures correct

If you can’t get the sag figure correct using the preload adjustment provided then the spring rates are incorrect for the bike / rider weight combination & different springs are required

Spring Rate OK - Static, Dynamic and Loaded sag within acceptable range.

Spring Rate too soft - 1) Loaded Sag too much or
2) Static OK but too much Dynamic Sag or
3) Dynamic Sag OK, but too little or no Static Sag

Spring Rate too hard –1)Loaded Sag not enough,
2) Static sag OK but Dynamic Sag not enough or
3) Dynamic Sag OK, but too much Static Sag


Damping

Its important to realize that there are no right and wrong damping settings
What works for you may not work for someone else
Damping must match the spring & preload settings.
Stiffer springs / more preload, will require more rebound damping and vice versa

Compression damping
This controls how fast the suspension compresses such as under braking and when hitting a bump
There are two type of compression damping, Hi speed and Lo speed, but this relates to the speed of suspension movement, not the speed of the bike, but this is too really getting technical, so don’t worry about it at the moment

Rebound damping
This control how fast the suspension returns back after being compressed from hitting a bump or after braking


Setting the damping

Front Compression
Usually a screw at the bottom of forks adjusts the compression damping – MkII 850 doesn’t have one, so ignore this

Front rebound
Screw at the top of the forks, in the cap – winding in the adjuster adds rebound damping
Best way to initially set rebound is to push up and down on forks. Forks should return promptly to original height but not overshoot

Rear compression
Adjuster usually on the remote reservoir.
TDM850 doesn’t have this so don’t worry about it

Rear rebound
Usually an adjuster at the bottom of the shock
On the TDM, turn adjuster knob anti clockwise when looking down on bike to add more damping
Rebound adjuster also affects the compression damping slightly on the TDM (cheap shock!)


Symptoms of incorrect damping (these are simplified as it can be quite complex)

Front Compression
Too much –front end feels harsh and solid
Too little – front dives too much under braking or when hitting bumps. Front end has a mushy and semi-vague feeling, and may bottom out upon impacts/bumps in road.

Front Rebound
Too much – front feels harsh (forks pack down as they can’t recover fast enough)
Too little – front feels like it wants to wash out, on corner entry

Rear Compression
Too much – rear feels harsh or solid over bumps
Too little – shock bottoms out on relatively small bumps (do not add more compression to compensate for soft springs)

Rear Rebound
Too little – rear end wallows in the corners (rises up and down)
Too much – rear feels harsh as it packs down.
Press down on rear of bike – suspension should return promptly to original position without overshooting.



The TDM850 can be set up for solo and pillion use with good results

Forks
15wt oil to level as per the manual (note this is measured without the springs fitted)
Std springs are very soft, but addition of 25mm preload spacer (inside the forks, between the spring and the fork cap) works quite well
With this, the preload adjuster comes back into range and you should be able to get the sag within the acceptable range
For two up use the front settings don’t really need adjusting once set, when swapping from solo to two-up


Rear Shock
Spring preload – I actually increased the spring preload by means of the collars on the bottom of the shock – shock needs to come out really, but can be achieved in situ with a hammer and an old screwdriver

For solo
Use rear spring in S position – rebound damping adjuster 7-8 out clicks out from fully in

Two-up use
Use spring in H position - damping adjuster fully in / 1 click out depending on how the compression damping feels (maybe too harsh compression damping on max)

Edited by GuyGraham, 16 August 2009 - 05:12 pm.


#2 TonyDevil

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Posted 16 August 2009 - 07:23 pm

thanks GG, moved to KB
"Never argue with an idiot. They just bring you down to their level and beat you with experience"
My TDM :
Black 1991 850 MK1, 160k+ miles(ish, best guess really, gave up trying to keep count after 3rd set of clocks and 3rd engine), PilotRoad2 tyres, custom stubby exhaust system, bluespot calipers & goodridge braided hoses with dunlopads, maxton forks, Ohlins shock, kedo handguards, stainless TDM grill, Scottoiler with lubetube & dual nozzle thingy, Givi Wingrack2 with E45 & 2xE36s, renntec crash bars, Autocom with blueteeth & PMR radio, TomTom Rider2, Optimate IIIsp, Bagster tank cover, anti-dazzle coating
to fit : led spotlights, heated grips, new braided lines and rear caliper that actually has bleed nipples
Silver-ish 2003 900, 70k miles, PilotRoad3 front tyre (new@65k) & PR2 rear(new at 69k), Renthal 755 bars with KTM handguards, oxford unheated grips, power commander 3usb, scorpion titanium exhausts, standard screen with vario winglet thingy, stainless grill, oem centre stand, bagster tank cover, givi monokey topplate mounted on grabrail with V46 topbox, Givi PL pannier rails with E21s, crash bungs, mirror extender thingys, Halfords Advanced Laser Blue brillance bulbs, 21w led spotlights, touring scottoiler with leehenty dual nozzle, Autocom with blueteeth & PMR radio, TomTom Rider3 Urban, winter style anti-dazzle coating
to fit : led brake light strip, replacement heated grips

current rides : TDM850 3vd/mk1=tourer&scratcher, TRX850=weekend twisty toy, TDM900=commuter, Z750 hardtail=project
gone but not forgotton : XTZ750=overland touring toy, GS500e, GS125

If you don't like my answers you should cease asking stupid questions!

#3 hawkman

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Posted 18 September 2009 - 12:44 am

Do you know the standard rebound setting for 1992 TDM850? Front and rear...
How many clicks out from full hard setting?


#4 tdm850rider

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Posted 18 September 2009 - 02:12 pm

QUOTE(hawkman @ Thu 17th Sep 2009, 08:44 PM) <{POST_SNAPBACK}>
Do you know the standard rebound setting for 1992 TDM850? Front and rear...
How many clicks out from full hard setting?


There are a lot of variables in suspension setup,
the settings I use at 145 pounds (easy riding) are not the settings a 200 pound rider needs for spirited riding.

Start with these as a bench-mark and go from there.
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#5 hawkman

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Posted 19 September 2009 - 01:04 pm

QUOTE(tdm850rider @ Fri 18th Sep 2009, 10:12 AM) <{POST_SNAPBACK}>
There are a lot of variables in suspension setup,
the settings I use at 145 pounds (easy riding) are not the settings a 200 pound rider needs for spirited riding.

Start with these as a bench-mark and go from there.



What is your rebound setting for your forks? How many clicks out from fully in?


#6 Kaustic

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Posted 19 September 2009 - 10:13 pm

Just to add from my experience :

I increased the preload on the front, which of course helped with brake dive but I seemed to also be bottoming out the forks when on bumpier town streets, fine on A roads. So I have been looking at getting the fork rebuilt in the belief that the springs where shagged.

Then had a brainwave & checked the damping which was now fully in i.e max rebound damping. Thus on rough rounds the forks were compressing and not rissing again before the next bump. The damper & preload adjuster are a combined assembeled part so rotating the body of the preload adjuster changes the rebound damping set . So next time you change your preload check the damping afterwards !

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Mods (so far) : Heavy duty chain & sprockets, Braided metal hose (front), DL650 handguards, Hyperpro progressive fork springs, Ohlins rear shock & Oxford Heated grips

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#7 tdm850rider

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Posted 20 September 2009 - 10:44 pm

QUOTE(hawkman @ Sat 19th Sep 2009, 09:04 AM) <{POST_SNAPBACK}>
What is your rebound setting for your forks? How many clicks out from fully in?


Good question... I set up my suspension over 16 years ago... can't remember what I had for lunch. munching_out.gif dunno.gif
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#8 jono

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Posted 11 October 2009 - 11:06 am

What kind of effect would tyres have on the suspension?
I have replaced my tyres and the bike seems to be very twitchy and vague suddenly.At higher speeds it also seems to get into a weave,
nothing uncontrollable,but not very comfortable.

I rebuilt the front forks,but the rear is standard,and has done about 43000miles.

Any ideas anyone?


#9 bruiser

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Posted 02 February 2010 - 11:29 am

Hi Guys,

Have been following the suspension set up thread and seem to be stumbling at the first hurdle.
My bike is an 06 900. Have started by setting all suspension to the handbook figures. Next I put a cable tye on the front fork rolled it off the centre stand and got a measurement of 50mm then 60mm with me on it. Around 80kg. the rear figures are 12mm and 30mm. No amount of playing with the preload gets me near your figures, although my model has 133mm of rear travel as oppossed to your 144. The bike was bought second hand from someone who had fitted a lowering kit which has now been returned to standard but does anyone know the correct amount of fork that should be showing above the top yoke, if any?

Grateful for any advice

Thanks

#10 Guest_GuyGraham_*

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Posted 03 February 2010 - 07:36 pm

Bruiser

Your fork springs are too soft to support the weight of the bike
I think the 900 has dual rate / progressive springs - ditch them and get linear rate springs such as K-Tch or RaceTech
The 2002 model has dual rate
6.86 N/mm (0.686 kgf/mm)
9.32 N/mm (0.932 kgf/mm)
Initial rate of 0.686 is way too soft and hence results in the huge amount of static sag
second rate is too hard and is why you only get 10mm of sag when you sit on it
you want something like 0.85kg/mm linear rate springs

your sag figures for the rear suggest the spring is a little hard for your weight
Messing with the preload will only result in both figures going up or down together, the gap between them will stay constant
To change the gap between the 12mm & 30mm requires a different spring rate ie new spring

sorry can't help with the fork protrusion out the top of the yoke
Have you downloaded the WSM?
2002 model has fork top flush with the top yoke

Edited by GuyGraham, 03 February 2010 - 07:39 pm.


#11 bruiser

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Posted 04 February 2010 - 09:53 pm

Thanks for your assessment Guy,

It would seem that the front spring rate initially is too soft and likewise the rear a bit hard. Assuming I fall into the 'average' category, as far as weight is concerned, Mr Yamaha must have intended the bike to be set up this way. Without knowing other owners findings its hard to say but then reading any bike review always throws up the statement 'softly sprung' and of course they no what there talking about! I find it slightly odd that the front should be soft yet the back is hard, why not the same differences? If I launch into new springs there's a good chance that the slightly vague feeling which I attribute to the 18" front will be the next area to play on my mind. So I'm going to enjoy it warts an all. By the way can you recommend a site to download the WSM?

#12 Guest_GuyGraham_*

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Posted 10 February 2010 - 12:48 pm

QUOTE(bruiser @ Thu 4th Feb 2010, 09:53 PM) <{POST_SNAPBACK}>
Thanks for your assessment Guy,

It would seem that the front spring rate initially is too soft and likewise the rear a bit hard. Assuming I fall into the 'average' category, as far as weight is concerned, Mr Yamaha must have intended the bike to be set up this way. Without knowing other owners findings its hard to say but then reading any bike review always throws up the statement 'softly sprung' and of course they no what there talking about! I find it slightly odd that the front should be soft yet the back is hard, why not the same differences? If I launch into new springs there's a good chance that the slightly vague feeling which I attribute to the 18" front will be the next area to play on my mind. So I'm going to enjoy it warts an all. By the way can you recommend a site to download the WSM?



I dunno why most jap bikes seem to be too soft up front & too hard at the rear
My SV1000S was exactly the same

To cure the vague feeling on my MkII I had too stiffen the front end with stronger springs and also lower it to get more weight on to it
Have you tried dropping the yokes down the forks to add more weight to the front end?

You can downlaod the WSM from JBX's pages I think

linky

#13 MCBodge

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Posted 06 March 2010 - 08:04 pm

The 0.85 springs are working well on my bike, but I'm still trying to get my rear Hagon right.

I backed off the pre-load by a turn a couple of weeks ago and wound the damping off by 1 whole turn in order to work my way up to the 'correct' level.

Ride was improved, but damping was lacking in corners. I twice increased it by 1/4 turn and then a further 1/8 turn.

This morning I went for a ride in better conditions.

When turning the bike very sharply into a right turn the rear felt as if it compressed a lot (slightly disconcerting!). At the next opportunity I added a further 1/8 turn of damping. This small change did seem to make a positive difference.
Riding at speed along rough 'scratching' roads front and rear seemed relatively in harmony, although the rear 'feels' as if it sags too much.


Currently the front and rear move up and down together:

Front dynamic sag is 43
rear dynamic sag is 40

Although this seems quite balanced I am going to try adding 1/4 turn of pre-load. This will reduce rear sag, increasing the difference between front and rear. Wise or not?

Edited by MCBodge, 06 March 2010 - 08:06 pm.


#14 Glossausage

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Posted 01 October 2010 - 03:22 pm

sorry to hijack, but I thought i saw an item about dogbone ride height adjusters. there are some on ebay which increase by 30mm at rear. I guess this would help turn in, and increase feel at front. It wouldnt let me post a new topic, I dont know why,,, I've been good???

#15 dmmsta

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Posted 03 October 2010 - 11:16 am

QUOTE(Glossausage @ Fri 1st Oct 2010, 04:22 PM) <{POST_SNAPBACK}>
It wouldnt let me post a new topic, I dont know why,,, I've been good???


Don't think you can start a new thread in KB, just update whats already there...the Mod-Squad have to move a thread deemed worthy into KB.
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#16 howie

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Posted 11 April 2013 - 05:44 pm

I have been fiddling with my front suspension since i got the bike the forks seem very harsh no matter what settings from soft to hard, i was thinking of fitting some progressive springs but after reading the above info i'm not sure. 

anybody got the answer. i am about 12stone with my gear!

                                                                                             John



#17 MikC

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Posted 11 April 2013 - 09:12 pm

Have you changed the fork oil? Stripped and cleaned the forks? I put heavier grade oil in and it made a big difference. Progressive springs etc are a good mod, but costly. Do the basic stuff first.

 

Mik


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#18 chrisr

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Posted 11 April 2013 - 10:37 pm

Definitely oil change first, you may have grey watery soup in there like I did. There's a how to in knowledge base. 


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#19 dandywarhol

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Posted 11 April 2013 - 10:52 pm

I have been fiddling with my front suspension since i got the bike the forks seem very harsh no matter what settings from soft to hard, i was thinking of fitting some progressive springs but after reading the above info i'm not sure. 

anybody got the answer. i am about 12stone with my gear!

                                                                                             John

 

The original springs are progressive.

 

The only IMO to get the suspension to work well is to fit Race Tech emulators - day and night/chalk and cheese etc. 


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#20 howie

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Posted 15 April 2013 - 08:24 am

Thanks lads i will go through your list cheapest first!
Anybody know where i can get a 81 yam xt250 cdi/coil, i have lost me spark,Not american fleabay
robbin b'''''ds.
John.                               XT250 spark problem sorted, twas a duff plug cap.

                                      thank you Keith Dixon Yamaha Accrington, top guy.


Edited by howie, 15 April 2013 - 06:56 pm.



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