For those of you just entering 1:8 scale racing. Just a little story about shock-fluids.

In the beginning of the 80's cars were equipped with small shock absorbers 1/4 of the current size. The shock fluid used was normally a kind of transmission oil. 
These oils always changed in viscosity (thickness) during use and temperature and a stable shock oil was not there. Therefore all kinds of products were tried. 
Even STP oil was used, you then had to warm up your shocks before racing with a hair dryer before you could use them.
Fortunenatly silicone oil was introduced in the mid 80's.
This type of oil has an better constant viscosity over a wider temperature range then other fluids but still is not complete temperature stable!

The thickness of the oil is officially rated in Centi Stokes "Cts".
Centi Poise (nowadays called Pascal per second) is the result of the Centistokes value magnified with the density of the oil.
Normally for silicone oil this value is 0.9875 = almost 1.0

An other known and used American rating is WEIGHT "WT". 
This WT or W rating is a non world standard and is introduced by Associated and not comparable between brands using this W or WT rating.

Thanks to Casper who found this remark on the net about SAE WT:

"Correct measures of viscosity are centi-stokes, N/m^2, or poises, depending on how you define it.
SAE WT is not really a measure of viscosity. The SAE scale was designed for classifying motor oils. For example SAE 30/40 means that the viscoity is one value (30) at one temperature and an equivalent (40) at the engine running temperature. When the number has WT after it this means "winter" so that the oil will have a particular value at I think 0 degrees Celsius.
The main problem with using the SAE scale oil is that each SAE band can encompass a large variation in viscosity. For example one manufacturers SAE 5 can be anothers SAE 10 and both are within limits. Using the SAE scale oil is best only to compare one manufacturer. "

Concerning Cts the thinner the oil (fluid) the lower the number, the ticker the oil the higher the number. 
For normal shock absorber use, this rate may vary between 100 Cts until 900 Cts.
Nowadays we use O-ring sealed diffs, so we can use silicone oil in the diffs instead of thick grease. 
For diffs the rate may vary between 1.000 Cts (loose) up to even 500.000 Cts (very, very, stiff).

Some USA based companies still are using the "WT" weight rating, where Japanese and European companies use the better linear industry standard Centi Stokes or Centi Poise rating. 
A lot off people think that the ratings between the "WT" and "Cts/Cps" ratings are linear but this isn't the case.

If there is a factory that can provide oil for testing we can arrange this to see if the product reaches the specification claimed or convert to Cts!

Which manufacturer use which rating?
Which manufacturers you can use same rating oil?
Only manufacturers using Cts as rating are using a world standard and can be mixed used.
Other ratings like W and WT differ from brand from brand as WT or W is not a world standard!

shock oil
Brand bottle values label rating linear values in Cts
Kyosho  100 - 900 numbers yes
Mugen 100 - 900 numbers yes
Associated 10 - 80 WT no
Losi 10 - 100 WT no
Orion 10/100 - 80/800 numbers no
Xray 100 - 900 numbers yes
GS-Racing USA 20 - 60 WT no
GS-Racing Europe 200 - 900 Cts yes
Crono ? ? ?
Serpent 20 - 50 W no
Thunder Tiger ? ? ?
Trinity ? ? ?

 

differential oil
Brand bottle values label rating linear values in Cts
Kyosho  1.000 - 60.000 numbers yes
Mugen 1.000 - 60.000 numbers yes
Associated not available not available not available
Losi not available not available not available
Orion not available not available not available
Xray 1.000 - 60.000 numbers no
GS-Racing USA 1.000 - 50.000 Centipoise Cts yes
GS-Racing Europe 1.000 - 50.000 Centipoise Cts yes
Crono ? ? ?
Serpent not available not available not available
Thunder Tiger ? ? ?
Trinity not available not available not available

If you have better information let us know

For shock absorber use, this is the comparison table when using LOSI,  ASSOCIATED and SERPENT some others silicone oil rated in "WT" "W" or are not labeled with a rating but just a number like 30/300

unofficial conversion values provided by Gene Hickerson USA
Cts Losi WT Associated WT
100 10 7.5
150 15 12.5
200 20 17.5
275 25 22.5
300 27.5 25
350 30 27.5
400 32.5 30
425 35 32.5
450 37.5 35
500 40 37.5

The 50 Cts steps between "Cts" rating are linear, where the 5 "WT" steps used in the "WT" rating are progressive compared to the real thickness of the oil.

No one can tell TEAM TWF8 how "WT" OR "W" rating is measured!!!!! If you know it let us know! info@twf8.ws


Serpent oil (04-01-2005)
rating W Cts

20

107
25 207
30 370
35  626
40 1070
45 1449
50 2250


We tested this oil supplied by Serpent Benelux on 04-01-2005 in our labaratory and compared them with a calibration oil.of 100 Cts.

Conclusion:
  Serpent oil is way of linear with Cts rating


Xray silicone oil with Rheometer
09-10-2005

Rating Cts
100 106
150 179
200 248
250 292
300 354
350 381
400 441
450 475
500 542
600 625
700 702
800 799
900 913
1.000 1020
Differential usage  
2.000 2490
3.000 4270
5.000 9000
7.000 10500
10.000 13000
20.000 30000
30.000 39600
60.000 65000

Use the values above for your benefit and as a guideline.
TEAM Xray has improved their oil line values from December 2006 onwards.
They now have a new silicone oil supplier.
Xray oil provided by TEAM Xray Slovakia


Kyosho

rating Cts
250 244
300 302
350 351
400 411
500 506

Use the values above for your benefit and as a guideline.


Associated silicone oil measured with Rheometer
09-10-2005
rating WT on bottle Cts Cts*
10 108 100
15 --* 150
20 208 200
25 286 275
30 373 350
35 454 425
40 525 500
45 - 575
50 707 650
55 - 725
60 725 800
70 960 900
80 1040 1000

Use the values above for your benefit and as a guideline.
* The value 15 Weights we measured was like water thickness and is probably a filling fault at the factory.
Altough the contents was silicone oil it was to thin for the 15 WT specs and can not be used for the shocks.
Associated oils were provided by Kendall Bennet from A-mainhobbies and Tony Penzincka from Tony Screws

*T he cyan colored values collum are provided by Kurt Menger from Team Assosiated R&D and are the values that will be curerntly mentioned on the bottles to give comparising with Cts values. (18-10-2007)


Trinity silicone oil measured with Rheometer
09-10-2005
rating Cts
30 337
35 376
40 505
45 497
50 658
55 568
60 799
70 757
90 974

Use the values above for your benefit and as a guideline.
Trinity oils were provided by Kendall Bennet from A-mainhobbies and Tony Penzincka from Tony Screws


Losi silicone oil measured with Rheometer
15-12-2005
rating Cts
15 110
17.5 158
20 243
22.5 243
25 294
27.5 345
30 381
32.5 397
35 459
37.5 477
40 546
45 657
50 886
60 844
70 970

Use the values above for your benefit and as a guideline.
Losi oils were provided byVolker Gerdes from BUGGY-SPORT.INFO


Currently we are measuring our oils with a RHEOMETER.
A sample of such a machine can be found here

This device is able to measure more accurat regardless the viscosity.

From September 2006 we measure all oils with a RHEOMETER.


SILICONE SHOCK OIL AND TEMPERATURE

Although everybody thinks silicone oil is not affected by temperature, we can wake you up out of that dream. 
When the same test is done @ 10 or @ 30 degrees Celsius we get other values!
Test result from our laboratory provid us with the following fist rule:

Below some examples.

Silicone shock oil measured in Centistokes at various tempratures in Degrees Celsius (Rheometer)
Shock oil temperature Losi 40 Trinity 40 Associated 40
5 754 688 747
10 677 622 685
15 605 555 598
20 539 492 536
25 501 467 502
30 455 420 456
35 409 377 410
40 373 345 375
45 345 320 346
50 319 294 319

To estimate your needed viscosity we made a XLS spreadsheet which you can use for calculating the correct viscosity.
You can download it here.

Team TWF8 special thanks goes to Jacco Koch our Chemicals specialist from The Netherlands for testing the fluids and the pictures.


Click here and see how to mix your silicone shock and diff oils in the right percentages.