Answer: Totally equal, you should better pay attention to other things…
A customer recently decided to get his VC professionaly serviced at our workshop, after a failed self repair. He sent us also his already purchased spare parts for the VC along.
The X-Rings from the customer seemed strange to me, because of their blue color. (The VC of the T4-Syncro got also blue X-Rings). However, my expert in sealings assured me that the color is without any relevande and purely optical. The visible injection points means instead a poor quality, while good products have a smooth surface.
But it gets even better: After cleaning with kerosene the customer’s blue quad rings became partly black. The quad rings had just been painted blue, for optical reasons(!).
In the picture above you can see on the left an original quad ring from the T4-Syncro and the cheap and painted one on the right.
I also asked the importer of the cheap quad-ring about the basic rubber material:NBR = Nitrile Butadiene Rubber
NBR can’t be used as a sealing material in contact with silicon fluid in a VC for two reasons:
- NBR shrinks in contact with silicon fluid and gets leaky
- NBR has a maximum temperature of about 100°C – which is to less for a VC with a hump-temperature of 120-135°C
Both requirements are met by FKM (formerly FPM) which is better known under its brand name Viton®.
Conclusion: Better pay attention to other values than the color of quad-rings.