Front fork question

The damper rods look like ideal candidates for re-making in stainless steel. Do such things exist?

I have heard that RGM (I think) make or made the rods in Aluminum at one time, but you need to go to bronze damper caps to avoid galling. That will lighten the un-sprung weight some more. They sell Aluminum damper bodies.



I couldn't find the Alloy rods so maybe they don't make them anymore or there were issues. Not sure.


They got the steel ones for sure.
Cheers,
Tom

CanukNortonNut said:

Here is an article PDF of how Andover does it:

Andover Norton Technical Database

Click to expand...

The part at the end where he says he only uses Belray 20wt is not a good recommendation. The regular Belray has a viscosity index of 106 which is a low number and means that the oil changes it's viscosity greatly when it heats up, the same as cheap oil does. Belray used to make Belray HVI fork oil which has excellent thermal properties but has been discontinued in the heavier weights. There's a lot better fork oil out there than Belray. According to the test chart, the standard belray is not even middle of the pack.

Here's the beray spec's from their own website. 109 VI That's kind of low thermal stability compared to Red line, Silkolene RSF, the old belray HVI, and many of the other fork oils made for racing.



So, the way you chose is you go to the list and the viscosity @ 40 degrees is the first column and it roughly corresponds with the brand weights as listed on the left, but one brand's 10wt might be heavier than another brand's 15wt. So, the weights only reference lighter and heavier within each brand...

The next thing to look at is the Viscosity Index (VI) which is the 3rd or 4th column. (3rd is claimed VI and 4th is tested VI) the higher the number, the more stable the fork oil viscosity is. If you are riding hard, a higher VI fork oil is good insurance against damper fade to maintain crisp handling. If you don't care about handling performance choice of fork oil probably doesn't matter.

Anyway, here's the list below find the range of the oil viscosity you want, then check out which brands in that general viscosity range have high numbers in columns 3 and 4. Those oils are the best because they change viscosity less when they heat up than oils with low numbers....



Like most stuff, it's all the same for your everyday putting around. It only really makes a difference when you want higher performance.

I Installed the Fauth Fork mod years ago and it has been great. It totally eliminated topping out and, with the recommended ATF as fork oil, provided a huge improvement over the stock setup. I was so impressed with it that for a few rides after installing it I actually rode out LOOKING for bumps!

o0norton0o said:

The part at the end where he says he only uses Belray 20wt is not a good recommendation. The regular Belray has a viscosity index of 106 which is a low number and means that the oil changes it's viscosity greatly when it heats up, the same as cheap oil does. Belray used to make Belray HVI fork oil which has excellent thermal properties but has been discontinued in the heavier weights. There's a lot better fork oil out there than Belray. According to the test chart, the standard belray is not even middle of the pack.

Here's the beray spec's from their own website. 109 VI That's kind of low thermal stability compared to Red line, Silkolene RSF, the old belray HVI, and many of the other fork oils made for racing.

View attachment 120702

So, the way you chose is you go to the list and the viscosity @ 40 degrees is the first column and it roughly corresponds with the brand weights as listed on the left, but one brand's 10wt might be heavier than another brand's 15wt. So, the weights only reference lighter and heavier within each brand...

The next thing to look at is the Viscosity Index (VI) which is the 3rd or 4th column. (3rd is claimed VI and 4th is tested VI) the higher the number, the more stable the fork oil viscosity is. If you are riding hard, a higher VI fork oil is good insurance against damper fade to maintain crisp handling. If you don't care about handling performance choice of fork oil probably doesn't matter.

Anyway, here's the list below find the range of the oil viscosity you want, then check out which brands in that general viscosity range have high numbers in columns 3 and 4. Those oils are the best because they change viscosity less when they heat up than oils with low numbers....

View attachment 120701

Like more stuff, it's all the same for your everyday putting around. It only really makes a difference when you want higher performance.

Click to expand...

Thanks for posting that.

"What I don't understand is, if 10w fork oil is recommended by a manufacturer, according to that chart the range can be any where between the mid 30's to the mid 40's (1st column) depending on the brand. So even if I choose the most consistent oil on the list, do I look for the bottle labeled 10w or use the chart to find the "best" reported 10 weight under column 1.
Probably a non-issue for the average rider but it just brings up an interesting topic.

Deets55 said:

Thanks for posting that.

"What I don't understand is, if 10w fork oil is recommended by a manufacturer, according to that chart the range can be any where between the mid 30's to the mid 40's (1st column) depending on the brand. So even if I choose the most consistent oil on the list, do I look for the bottle labeled 10w or use the chart to find the "best" reported 10 weight under column 1.
Probably a non-issue for the average rider but it just brings up an interesting topic.

Click to expand...

Column 1 just arranges the actual viscosities of oil brands. So Elf moto 2.5wt is heavier than Belray's 5wt even though the "wt number" implies that it isn't. That's just variation of how brands use the labeling system of "oil weight" differently, but the system still works within each brand.

The main take away is that if you have a suspension that has fixed orifice dampers like a stock commando. the only adjustment is oil viscosity. In the case of more modern dampers, you have externally adjustable orifices so you can maybe chose 5wt or 7.5wt of a certain brand and then use the adjusters to dial in the settings that work best for you with either oil choice, given that you have more than just oil weight choice as a variable. Regardless of which level of suspension technology you have, the column 3 and 4 tell you how stable your choice of oil's viscosity is between 40 and 100 degrees centigrade. The higher the number the less the viscosity changes, the lower the number the more the viscosity changes...

That brings up whether it matters to the average rider much. IMO, only enough to be in the ball park without needing to overthink it. But,... If you are happy with your stock commando suspension and you get on a commando with modern dampers installed you'll definately notice the difference, but you may not like it more because comfort and high performance are on opposite ends of the spectrum. You may like the soft floaty feel of the stock commando which goes away as you improve the performance.... That was the most interesting thing about all the testing I did. I actually thought I was going to get both a softer ride and better performance at the same time when I did my damper modification. As it turned out I had to chose a point on that scale where I was comfortable with the compromise. Most commandos have an incredibly soft ride compared to mine, but their steering doesn't feel as precise because of that softness. Higher performance only matters when you are pushing the bike hard through the twisties or on a race track. Just putting along down the road, the stock commando suspension's ride is like floating on a cloud. There's nothing wrong with preferring that, if that's the feel you want your sport bike to have.

Lansdown dampeners along with NYC bushing and seal kit have now been expertly installed on my bike by o0norton0o, and what a difference, thanks Frank!
I chose to use Torco RFF 15w Fork oil as well (the old stuff that came out of my forks was horrid brown glop!)

We had a great time doing the work, (OK, I mostly watched despite many attempts to get my hands in there), a mutual friend also from NWNO also stopped by and we all went for a fun test ride through the local forested area afterword.

The results of the dampener swap were incredible. I was not fond of the stock squishy marshmallow bottoming out dampening, that my bike had before, but had been assured it was normal, so I was trying to ignore it. The feel is much more to my liking now, firm and confident feeling. I'm not any kind of a fast rider, the firming up just feels so much all around better to me. It also had to be a good thing to get the NYC bushing and seal kit in there too. I'm feeling pretty good about it all, in fact can't stop thinking about it!

One day I may upgrade to Frank's custom dampeners which do a lot more, but for now I am ecstatic about about the results acchieved from our time last Saturday, and I had a blast too!

Hey Ed, It was a fun day correcting your fork issues and working out the problems to get that beautiful bike going. The oil that came out of your forks was mud and the worst I've ever seen. The person who supposedly serviced your forks recently,...... clearly did not actually do that. It makes me wonder is he actually adjusted your valves properly and timed the ignition correctly as well since your plugs looked a little bit rich. Thanks to Don for his help with the Mikuni. It's always best to troubleshoot parts you have experience with and I never ran a mikuni, so Don's input was great, besides being nice to see him again. I'm sure you'll enjoy what you have now for a while after seeing the fork damper disaster that was removed. It's no wonder that you were getting a clunk with the condition your forks were in. I particularly liked the NYC norton bushings, so this morning I ordered a set for myself.

I hope your bike is running better. At some point in the future, we could do a valve adjustment check, and throw the timing light on your ignition to check both of those, then go for an actual ride through the foothills out my way.