850G fork issue

[Guest]

Hey there, I'm tha proud new owner of a 81 850G, my first road bike. So I'm changing a couple of small things to suit me and bring maintenance up to spec. The front end is quite harsh, I feel all the imperfections in the road surface banging through the hands. The forks seem fine under braking and through normal stoke movement. There is progressive springs (468mm long) already installed and the shop just replaced fork oil with 250cc of 10w. I'm approx 78kg fully kitted. Apart from some general negativity about progressive springs the only other possible issue I can find iz that 250cc may be too much oil as progressive springs require less oil than standard springs....is this correct? Been playing with tyre pressures to try and help. I'm learning so any info/help is much appreciated guys. Thanks

[Dogma]

I suppose it's possible that different springs use more space than others. That's one reason why the preferred method of setting the fork oil level involves measuring the height from the top of the fork tube. Check a service manual for the procedure, they can be downloaded for free from Bass Cliff's site. 250cc doesn't seem like much, but I don't have a reference handy to check. I don't think it's catastrophically overfilled though. That would be the way to unnecessary harshness with that oil.

Two other things can lead to a harsh front end: stiction, which it sounds like you don't have, and the nature of the stock fork. The stock damper rod forks have a progressive damping rate. The faster they compress, the harder they resist compression. That means that bigger bumps are transmitted to the frame even more than small bumps. You can mitigate this with lighter oil, but 5w would feel out of control, probably even dangerous. The fix is to change the nature of the fork's damping, which means installing cartridge emulators.

I installed Race tech emulators and Sonic straight rate springs this year, and it completely transformed the bike's front end. It's compliant over bumps, but fully under control in corners and under braking. Cost was roughly $250 US to do both.

[alke46]

I am in the process of rebuilding my forks and I found each one was carrying approximately 225ml of oil. Not sure what the proper amount is though. Just checked and the SM states 241cc.

[bwringer]

The amount of oil is completely irrelevant, other than it helps to know approximately how much you will need to have on hand.

What's crucial is the oil level. Moreover, the oil levels in each fork must be exactly the same.

You cannot just measure out a certain amount, dump that in, and call it good.

[alke46]

Right, and in my case I recall seeing the level measurement at 140mm.