ITC Damping on TE 510

[SA63]

I have a recently completed te510 which is starting well and behaving like it should BUT... the rear shocks are terrible..

The shocks werent leaking damping seemed ok, so I regassed and resprung (heavier)and put them on
I used at short circuit/ flat track and its apparent there is almost zero rebound. Pushing on the shocks static they bounce back almost straight away. Damn scary the back end pogoing..

Further to this I borrowed 2 more pairs (unrestored) tried original white springs, all seem to have very little rebound.

I am keen to get them revalved (going to happen)but thought id throw it in here for comment on what others have done,

Even my dirty flogged out, never touched mexican mulhollands on my 77 maico have more more rebound!

 

[scoott]

Every ITC I have rode have been woefully underdamped for rebound, especially if you run the stiffest yellow spring. Even the white springs are underdamped. I have revalved 4 sets, each a little stiffer on rebound and compression. They are getting better, but more of both for the next set I revalve. ( I have lots of spare sets, so I revalve an old set and move the last revalved set to another bike.

I have an 83 500cr, 84 500 wr, 83 250 xc, 84-86 dual shock 510. ( 86 motor in an 84 chassis). All were woefully underdamped, although the 84 510 chassis had the stiffest valving, don't know if it was stock or revalved by someone. Still wasn't enough.

 

[SA63]

Ah ok, so its not just me!
Yes compression could be better but wasnt as bad as the rebound, at least it can be found.
So have you used different washer/ shims to alter the damping?

 

[scoott]

Shims and the heaviest springs are still available from Ohlins.I have been following the Ohlins chart to stiffen the damping in stages with thicker shims.

 

[SA63]

I want to use the bike next weekend so wont touch anything now, but I have had a look at a manual with a shim listing. i dont quite get it,
but would stab a guess at using :
two holes in compression washer (if standard is 3) ,and 0.25 or 0.3mm thick in relevant shim size on rebound?
Itd be great if you could put me in the ballpark so I can try and get it right first time around.

 

[scoott]

I think I went from 2 bleeds to one. Look at each stack ( compression and rebound ) and thicken the shims top to bottom. ( make all .20's before starting at the small end with .25's and making the whole stack .25's before going to .30's, etc.

 

[SA63]

thanks scoott, I need to pull them down.. but after this weekends racing!!

 

[pcnsd]

Immediate Terrain Control or Instant Terrible Crash. Everyone had their own opinion about them. But whether you loved or hated them they were the headwaters of the multistage valving used in every performance shock today.
I have worked one or two of the Ohlins twin shocks and will offer what I have learned and gathered for the ITC and shock valving in general. I don't have the stock valving for your bike, but I do have the valving from a 84 CR500 which should be similar.

Compression:
Valve plate x .2mm x 2 holes
21mm x .2mm
Valve plate x .25mm
27mm x .25mm
24mm x .25mm
18mm x .15mm
27mm x .3mm

Rebound:
Valve plate x .2mm
27mm x .25mm
24mm x .25mm
21mm x .25mm
18mm x .3mm
14mm x .3mm
14mm x .3mm
14mm x .3mm

Shock oil = 10wt (Maxima heavy racing shock fluid is good and half the price of Ohlins which is good too.)

N2 @ 180 psi (Don't use air ever! The high partial pressures of oxygen causes the oil to oxidize rapidly and the smaller O2 molecules ensure migration from the gas reservoir into the oil.)

Bottom of float piston to bottom of reservoir = 60mm

The stock valving above is not a bad stack to start with. You may find all you need is fresh oil, a purge of the gas in the oil chamber and N2.
Do not go over .2mm on the valve plates or less than 2 bypass holes. It will be too stiff. I have only known one person who was happy with .25mm valve plates and he is fast, weighs 260# and is sprung to match. The general advice above regarding starting with the smaller diameter shims is mostly correct. A better overview maybe to know that the shock acts based primarily on shaft speed. The bypass holes act at the lowest speed and effect both compression and rebound. The valve plates act at the slowest speeds at which the valve plate begin to open and as the stack diameter reduces it effects a higher shaft speed. Please note the 3 stage compression valve stack listed above. Each separate stack is set to act at a different speed range. You will not effect H/S damping by making changes to the low speed circuit. Shaft position damp sensing is based on the amount of oil used and N2 pressure. As the shaft displaces oil into the reservoir it raises the N2 pressure which raises the effective damping rate.

Hope this helps.
Regards,
PC

 

[SA63]

Great info - thankyou, a good bench mark. makes me keen to rip them apart..!!
I understand the ohlins the ohlins oil is 7.5wt, so I guess the 10 wt will slow things down a little

 

[SA63]

i did a quick rebuild on a borrowed pair with 10wt oil- damping needs changing, will go with thicker shims..

 

[pcnsd]

i did a quick rebuild on a borrowed pair with 10wt oil- damping needs changing, will go with thicker shims..

Are these from another 510 or ITC mount?
What are your static sag and race sag measurements?
Did you record the C&R shim stacks for future reference? Care to share?
Where in the shocks application do you feel is the area of concern, be specific as possible please. (Compression/rebound, On what type(s) of obstacle(s), Rider skill level)

Regards,
PC

 

[husqyhamm]

510TE has ITC with valving setup code HA0995. Same as WR500.

500/10TC/TX has HA0505 which is same as 500CR/XC.

Within next few months I'll be stripping original, unopened HA0995, HA0505, HA0507 and catalogue shimming stacks before the party with regards to oil viscosities and shimming alterations start.

 

[SA63]

the shocks I did the quick rebuild (oil & gas) had the cr500 damping as listed previously.
I used 10wt oil as suggested, but didnt like the result. These were some I borrowed. I would prefer more rebound. Compression was ok but I think id still up it a little.
I also tried the 8.5 mm dia yellow spring (good) and a 10 mm spring (too hard)
The riding was natural terrain mx with some step up jumps etc. As chopped as youd expect from maybe 180 bikes racing on it.

Next is to rebuild my own and reshim.

On question I have is on what no. shim can you say is the transition from low to high speed compression and rebound damping?

 

[SA63]

On sag on 8.5 mm spring I had 25 mm static sag, 100mm sag on bike and with 10mm spring I had 20 and 80.
I changed springs using 2 screwdrivers for spring compression so the springs were tensioned on around clip position 4 or 5 from top . Currently have a spring compressor under construction, cut and drilled, but not welded up..When done Ill compress the 8.5 dia springs more to try.

Skill level- intermediate to quicker but not faaast (running 3rd to 5th of 20-25) kind of running in no mans land. the quick ones are gone..

Bouncy/ unbalanced feeling. I was also riding a 81 Maico that day with good suspension, which is what Id like to get it closer to.

 

[pcnsd]

Try this on your next rebuild.

Compression:
Valve plate x .2mm x 2 holes
21mm x .2mm (This is the end of the slow speed stack)
Valve plate x .25mm (On these secondary valve plates, hole number is irrelevant if you don't have the straight plates)
27mm x .25mm
24mm x .25mm
18mm x .20mm (This is the end of the mid speed stack)
Valve plate x .25mm
27mm x .25mm (This is the end of the high speed stack)


Rebound:
Valve plate x .2mm
27mm x .25mm
24mm x .25mm
21mm x .30mm
18mm x .30mm
18mm x .30mm
14mm x .30mm
14mm x .30mm

Engineering is the art of achieving the best compromise for a given set of criterion (Olde saying)
What you should be looking for is to use all or almost all the available suspension at each speed range and have enough rebound damping to eliminate the common rebound issues (side dancing in the whoops, rear high off of jumps) keep in mind a 4 stroke has serious engine braking compared to a 2 stroke and if you chop the throttle before leaving a jump it will pull the front down.
If you get it right, it should seem soft (Plush) all over, but you should rarely bottom hard and you will not fatigue as quickly (The big plus)

Regards,
PC

 

[SA63]

thanks for the info. I believe I can get pretty close to that using a donor pair for a few shims, and ill test this weekend at another grass track event before doing the final proper rebuild, (seal head etc)
So you suggest using a 3rd valve plate on compression rather than the 18mm shim?Ok Ill do it..

Have you any comment on the aluminium spacers that is between the shim stack and rubber bumper? I understand this is a feature on the WR/TE to limit height, and removing it will allow more extension on the shock thereby sharpening up the steering.

The two pairs Ive pulled apart have differnt thicknessspacers. roughly 8 mm and 12 mm on the second set(didnt measure). Im inclined to use the 8mm or turn up a thinner pair, maybe 6mm.

I guess where I am looking for more stability is flat corners, thats where its a bit bouncy mostly. jumps arent too bad. The 510 has great handling and jumping manners compared to some similar era 4 strokes (hasnt got the dead weight feel!)

I am running 15wt oil in the forks. I first tried motor oil as it recomended elsewhere in the forum, but found it way too stiff (terrible actually) the forks are pretty good but I feel a bit of "lock" on big hits. Pretty simple damping rods!! Anyhow maybe later Ill try the emulators which I have in the Maico. Just want the front and back feeling balanced.

 

[husqyhamm]

PC, I'd like to try your shimming setup on a next rebuild. Did you use the 10wt Maxima oil with it?

SA, the spacers you mention does exactly what you said, it reduces HA0995 shaft travel and shock eye to eye length. Reducing spacer thickness will increase length and travel. MY CR and TX twinshockers run 340mm travel, thats nearly 14". Just remember the TE like WR had forks with less travel to go with the shorter shocks though they have same actual length from acle to top of fork. I use 10wt Belray forkoil and am happy with allround performance insofar as those forks can go. Best change i did to the TE was to use the upright barmounts from 85-87 singleshockers.

The TE are brilliant allround machines.

 

[SA63]

I have always used 10wt in the maicos, but the damping holes are a fair bit bigger in the husky,hence thought heavier wt oil would be good.
When I rebuilt the bike I used the straight barmounts. didnt take to the the layback style.(never even tried them)
I modified the fork caps too, so as to be able to get them higher in the triple clamps. the plastic inserts were broken anyhow
I machined out the internal thread, fitted a recessed aluminium spacer, tigged it and tapped it for the air valves. I found out later the later model huskies (with straight mounts)have a similar set up.
yeah the husky is great, slightly off topic, not the easyist starter but dicking around with the dellorto and learning the technique got it to about 4 kicks when cold. fine when warm..
So where in sa are you? I lived there from 8-16yr old, learnt to ride around jhb, I used to watch mates race as juniors mx at syringa!

 

[pcnsd]

About suspension oil weight:
Most of the oils you see are listed by oil wt. (SAE) All things are not equal in this case. If you look at a viscosity chart for oils, the viscosity window for any grade over 10wt is quite large. It is possible for oils of the same viscosity to be legitimately listed as 7.5, 10, even 15wt. What and why they call it is a marketing decision made by the companies. Look for a listing of the SUS (Saybolt Universal Seconds) viscosity index if you can find it. This will list the viscosity range you will find in the bottles. It is a more honest indicator of viscosity.
I recommended two shock oils (Ohlins & Maxima heavy). I have used these in the past and had predictable results, but you may need to find something else in your locale. Suspension fluids only please.

Pay attention to the shim thickness in the 2nd post, they have changed also. All the other basic setup info is in my first post. A pair of digital calipers is important for measuring the shims.

Regarding the aluminum shaft spacer, you can leave it out, many do including myself, but it will not make a big difference in rear travel or suspension height. 59" between axles works out to about 1 degree of steering angle change per inch of suspension height change. This is cumulative in its effect. Lower the front .5" and raise the back .5" = 1 degree of change.
I run the fork tubes on my 81 430CR, 25mm out the top of the clamp. The tire rubs lightly on the fender/frame pinch point at full travel. Don't set yours by what I did. Check it and make sure your wheel will turn when fully compressed or over the bars you will go.

Regarding the 40 mm Husqvarna forks, they were never great, but can be made acceptable if you are a tolerant sort. I use 15-wt fork oil in this case. I also have the Race-tech emulators installed. They are backed off on compression slightly from the recommended setting. The fork have always been harsh in the mid to end stroke for me. (Before and after the emulators) It is particularly noticeable when I change from my modern bike. I also tried motor oils of various denominations in years past including 20-50wt. All with the results you experienced. 15 wt oil and oil level set to prevent prevalent hard bottoming is as close as I have come to being.... just OK.

Regards
PC

 

[SA63]

So.. i have reshimmed and rebuilt the second pair shocks without the spacer.

They feel different in the work shop pushing down on the seat, with noticable rebound now. compression still feels minimal, but will try it on the track.(Sunday)

It is similar to my ohlins suspended maico now when pushing on the seat..
Still very different to my modern bike though! (ktm 09 exc 250)(xcw) the ktm feels very hard by comparison(stock as rock)

I have another problem from taking out the 13mm shock spacer. With the length of the shock now increased, the spring is effectively shorter so on max tension on clip position I have more sag (120mm) To get back to 100mm I need a external spacer on the spring now!
So taking out the spacer hasnt lifted the height of the back of the bike, but effectively the it is sitting lower in the stroke now.

What have you done regarding this PC? and what would you recomend for the sag for the husky?

In the seconfd pair of shocks one of the negative springs was broken, and the shim supplier said they arent available now and to leave them out anyhow - so I did, and with a bigger bump stop , probably is fine - any comment?

I have the forks about 12mm out from the top of the triple clamps which is fine for cornering. the 4stroke always seems to get good front end bite compared to a 2t.