Triumphrat

dharmabum · 06-11-2006, 12:46 PM

I am having a fork seal replaced (hopefully just the seal), as well as new springs. The tech asked me if I have heard about any other preferences out there in the Bonneville Forum Land on fluid weight? He said changing the weight from factory suggested to something else might improve things. Any suggestions out there? I stumbled on one thread that suggested a good synthetic 20w. Any suggestions of what and a why would be appreciated.

oldsport · 06-11-2006, 06:33 PM

I've stayed with the suggested weight - I think it's 10w? Others say they've gone with 15 and 20w.

Kevin Cameron, tuner extrodinair points out problems with increased viscosity in his book, "Superbike Performance Handbook". When the fork is expected to rapidly respond, the heavier oil may not return quickly enough and can cavitate. The fork can actually lock briefly.

His suggestion for increasing dampening is to experiment with blocking some of the dampening holes in the fork rod. I used this approach years ago by plugging a couple of the holes using epoxy and then redrilling a hole with a smaller diameter. It didn't really make any difference riding around at near legal speeds.

Sheepdog · 06-12-2006, 06:38 AM

I also continue to use the 10wt oil, with great success. My biggest problem with the stock front end was the non-progressive springing and the excessive sag. Once a good aftermarket spring was installed (I use the Ikons), I was pleased with the performance of the forks.

dharmabum · 06-12-2006, 02:01 PM

That's excellent. Thanks for the input.

oldsport · 06-12-2006, 02:33 PM

I too have aftermarket progressive fork springs. I also replaced the shocks with Progressive 412s.