Author Topic: What oil to use in forks?  (Read 335 times)

0 Members and 1 Guest are viewing this topic.

cee-b

  • Star
  • *
  • Posts: 41
    • View Profile
What oil to use in forks?
« on: 23 May, 2018, 16:07:22 »
What type and weight of oil would you recommend using in front forks please?

I have a C15T with non-standard front forks (I'm not sure what they are I'm afraid).

The previous owner had used 20W50 engine oil, but I feel that isn't giving sufficient damping. I used the bike on a long-distance trial at the w/e; I could feel the fork banging off the stops in extension while riding the trails between sections, so the rebound damping would appear to be insufficient.

From the dents in the mudguard caused by contact with the bottom yoke, the suspension evidently bottomed out as well, though I did take a pretty big 'hit' dropping out of a section into a gully.

I was going to replace the oil with a known weight - which is why I'm asking for advice - make sure the forks are properly bled, and then experiment with gradually increasing the oil quantity

AWJDThumper

  • Empire Star
  • *****
  • Posts: 767
  • Dandy Beagle D14 C15 B40 B40WD B44 B25 B50 A10 A65
    • View Profile
Re: What oil to use in forks?
« Reply #1 on: 23 May, 2018, 18:55:09 »
I use 15W fork oil in my off road bike but it's got fairly sophisticated long travel front suspension. You can vary the viscosity to suit your needs and, as you say, you can vary the quantity of oil to give you some control of the overall spring rate.

cee-b

  • Star
  • *
  • Posts: 41
    • View Profile
Re: What oil to use in forks?
« Reply #2 on: 29 May, 2018, 13:51:15 »
Thanks for the response AWJDT.

It would appear that insufficient quantity of oil was the problem. When I replaced the same amount I'd taken out and exercised the forks, I could hear and feel them cavitating before end of stroke.

I've increased the quantity and will experiment depending on how it rides.

STAR TWIN

  • Royal Star
  • ***
  • Posts: 191
  • A7 A10 B31 WDB40
    • View Profile
    • Strange Sheep
Re: What oil to use in forks?
« Reply #3 on: 29 May, 2018, 14:13:09 »
I use tractor universal 10W-30. Although it's an engine oil, it's also a hydraulic oil. It's great for primary chaincases too and it's cheap.

AWJDThumper

  • Empire Star
  • *****
  • Posts: 767
  • Dandy Beagle D14 C15 B40 B40WD B44 B25 B50 A10 A65
    • View Profile
Re: What oil to use in forks?
« Reply #4 on: 29 May, 2018, 17:27:16 »
Thanks for the response AWJDT.

It would appear that insufficient quantity of oil was the problem. When I replaced the same amount I'd taken out and exercised the forks, I could hear and feel them cavitating before end of stroke.

I've increased the quantity and will experiment depending on how it rides.
It's can be difficult to determine the correct amount of oil or oil depth if you don't know what forks they are. Have you got a picture of them?

cee-b

  • Star
  • *
  • Posts: 41
    • View Profile
Re: What oil to use in forks?
« Reply #5 on: 02 June, 2018, 12:38:03 »
Here are a couple of pics. I'll also start another "does anyone recognise these...?" thread.

Cheers