Fork oil
Fork oil is a hydraulic oil and lubricant that is used in telescopic forks of two-wheelers, such as bicycle suspension forks and motorcycle forks . Like motor oil , it is available in mineral oil-based , fully synthetic and partially synthetic form as well as in various viscosities .
The fork oil is used to lubricate bearing bushes, guides and springs and, in the case of forks with open cartridge systems, also as working fluid for the oil-hydraulic shock absorber (s) . The damping effect of such a telescopic fork can be influenced by the viscosity of the fork oil that is filled in. It is available in viscosities from SAE 2.5 to SAE 30. In the case of forks with closed cartridge dampers, the fork oil filling only needs to lubricate the sliding components, as the damper inserts have a separate, sealed oil filling.
The oil filling of modern telescopic forks is located in the interior of the individual fork legs, designed as a closed reservoir. The oil chamber (and possibly also the pressure chamber in the case of air-assisted suspensions ) is sealed to the outside by a shaft sealing ring that works as a mechanical seal between the telescopic components. As the fork oil ages and is also affected by abrasion and dirt and moisture brought in by the sliding sealing rings, the fork oil must be changed regularly according to the manufacturer's specifications. Often there are small drain plugs for maintenance at the bottom of the fork near the axle clamp . If there are no such drain plugs and the oil cannot be drained through the screw connection of the damper piston rod or spring push rod (as is the case with many bicycle forks), the fork legs must be removed from the triple clamps to change the oil (motorcycle) or the bicycle must be turned upside down and the oil will be poured out through the top plugs. As a rule, these plugs are also used for filling with fresh oil. The filling quantities are specified by the manufacturer and are in the range of up to a few hundred milliliters, often in different quantities on the left and right due to the different functions of the bars.
Since the amount of fork oil filled in is decisive for how large the volume of air between the oil level and the sealing plug in the individual tubes is, when filling the fork tubes with fresh oil, you have to work exactly according to specifications, as this air cushion - usually one from the designer intended - has an impact on the spring rate of the fork.
Up until the 2000s, automatic transmission oil ("ATF") was also often used as a fork oil filling in motorcycles . B. on many Honda models.
Not all telescopic forks have a closed oil bath and require fork oil fillings; Simple moped and moped telescopic forks are often only greased, as is the case with older elastomer bicycle forks.
Individual evidence
- ↑ Example: Bicycle care products at www.hanseline.de, accessed on June 29, 2014.
- ↑ a b Repair instructions Ducati M 600/750/900 Monster from year of construction 1993 , 3rd edition, bucheli Verlag, 2009, ISBN 978-3716819487 .
- ↑ Example: Castrol fork oil 10W mineral 500 ml at www.louis.de, accessed on June 29, 2014.
- ↑ Example: Putoline HPX 10, front wheel fork oil, synthetic, 1 liter ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. at www.brands4bikes.de, accessed on June 29, 2014.
- ↑ Example: Motul Fork Oil Expert heavy fork oil ( Memento of the original from March 9, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. on www.quad-company.de
- ↑ Comparison table of fork oils at www.goede-motorsport.de, accessed on June 29, 2014 (PDF).
- ↑ Gabelöl - Motorrad-Gabelöl Fork Oil on www.10w-40.eu, accessed on June 29, 2014.
- ↑ Change fork oil , article on motorradonline.de , accessed on June 9, 2016
