bigjohnsd
2021 BMW R1250GSA
10W Fork Oil makes a significant difference. I believe that it provides a greater range of adjustment on compression and rebound over the stock oil especially for someone of my #255 size.
Suspension Tuning - It's a Process!
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redneckj
Well-known member
<blockquote class='ipsBlockquote'data-author="bigjohnsd" data-cid="1340326" data-time="1475160256"><p>
The Avon folks also advocate the 10% pressure rise rule for Tire pressure as well. Cold pressure should be set at whatever pressure it takes to achieve a 10% rise in hot pressure. So 38 cold would end up at 42 hot.</p></blockquote>
I will find out if 42lbs cold tire pressure will still be 42 lbs hot after doing the nitrogen swap. I'll know tomorrow.
The Avon folks also advocate the 10% pressure rise rule for Tire pressure as well. Cold pressure should be set at whatever pressure it takes to achieve a 10% rise in hot pressure. So 38 cold would end up at 42 hot.</p></blockquote>
I will find out if 42lbs cold tire pressure will still be 42 lbs hot after doing the nitrogen swap. I'll know tomorrow.
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MCRIDER007
Well-known member
Be sure to check the hot air pressure out on the highway as quickly as possible because the temperatures and pressures will start to go down as soon as you slow down and/or stop. Air pressures are a back door way to achieve desired tire temperatures, pure nitrogen has some advantages over the 78% version I put in my tires but the tires are going to take longer to reach hot operating temperatures. Try taking readings after 10, 20, and 30 minutes and see if there is any differences in pressures.
HaulinAshe
Well-known member
Less preload up front means the front sits lower in relation to the rear. That results in quicker turn-in. Getting ride height balanced between front-rear is one of the most critical adjustments to make. That's why it all starts with spring rates and preload.<blockquote class='ipsBlockquote'data-author="MCRIDER007" data-cid="1339223" data-time="1474648485"><p><blockquote class='ipsBlockquote'data-author="Pterodactyl" data-cid="1339208" data-time="1474640736"><p>So, John, care to share any info on how you are adjusted these days? Out relevant characteristics are somewhat similar.</p></blockquote>
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My question also. Not much you can do to the shock since there isn't any preload/height adjustment and John didn't have much damping adjustment left on his well used shock, so I would guess that he lowered the height on the forks for some quicker steering and then played with the fork's damping to compensate for the 10 wt. oil John installed after the Ruben run.</p></blockquote>
I'll check and record the dampening settings when I get home. The front has less preload etc than when I arrived. The rear is still on hard. I don't know what the front and rear dampening settings ended up at. I rode, he twiddle. I rode again. Got to say that it worked well between Thunderhill and Calistoga
and again down CA 1 on Thursday. I'm more confident, it's less tiring and it stays settled in the corners better than it did, especially if there are mid corner bumps.
redneckj
Well-known member
So I left Hillsboro, OR after work heading back to WA. I double checked my cold "air" pressure on the front and rear T30 EVO's. 42lbs rear and 41lbs front. I did the nitrogen swap the other day and wanted to see if the tire pressures would raise as much they did with air. I rode about a hour. Highway speeds, some hard cornering, yada yada yada. Anyways, I pulled over and checked the tires pressure. 44 lbs rear and 41lbs front. The rear pressure only came up 2 lbs and the front was exactly the same.
MCRIDER007
Well-known member
It's hard to draw conclusions from a single test unless you had established a baseline using the same tire guage and determined the starting cold pressures to achieve a 10 percent increase in hot pressures (this can be a challenge with the variation and inconsistency in tire gauges). If you don't have a base line for comparison, try starting with cold pressures of 37/40 on your next ride and see what happens.
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redneckj
Well-known member
My base line was as follows. Tires sat for 7 hours before I left. They were cold. I measured the pressure before I left with my pressure guage and then measured the tires about a hour later after I rode the bike with the same pressure gauge. . Not rocket science.
Well I've always run my tires with an 80% nitrogen mix myself, and that's seemed to have worked out okay...
wheatonFJR
...
But, but,.....Well I've always run my tires with an 80% nitrogen mix myself, and that's seemed to have worked out okay...
...never mind.
RaYzerman19
Go Wings!
My general method which my fork rebuild victims seem to find useful....... others may chime in......... Rear shock on Soft (this shock has a decent spring). Front preload two or three lines showing..... these are progressive springs, just add preload until you feel fork dive upon braking is not excessive. For damping settings, it likely came with all 12 clicks out, which is very little damping..... Damping is more your preference, no one rule, but as a starting point, dial in all then back out 8 clicks as a starting point. As you ride in various conditions, you will adjust (read up on suspension tuning) and may end up at something less than 8. E.g., adjust fork rebound to 6 and go ride, dial it in by two clicks at a time to see noticeable difference, back out as needed. Then do fork compression damping same method, then rear shock rebound same method, riding in between each individual adjustment. Ride the same route each time, same bumps and hollows. Don't adjust 3 things at a time, you won't know what did what necessarily. So after all this, you have it roughly set.... with additional riding experience you can tweak one click here or there.
The idea is to have the preload correct and using the least amount of damping for your weight and preference that still keeps the suspension in control.
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bergmen
Well-known member
I sure wish it was easier to change the fork oil on these bikes, both for maintenance and increased performance/experimentation.
Dan
Dan
bigjohnsd
2021 BMW R1250GSA
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Cav47
Adventure Seeker
That is a good tutorial John. After my suspension SNAFU, that is who I watched and right away after doing what he suggested, I was very happy and surprised by the results.
As Ray said, fine tuning after riding a while is really key. Also, the fork oil heats up and flows much faster than cold in the garage. Riding in Wisconsin around 40* is certainly different than riding the Dragon in Summer 90+*.
As Ray said, fine tuning after riding a while is really key. Also, the fork oil heats up and flows much faster than cold in the garage. Riding in Wisconsin around 40* is certainly different than riding the Dragon in Summer 90+*.
bigjohnsd
2021 BMW R1250GSA
There are many folks here who are quite knowledgeable in FJR suspension setup, especially the PNW guys.
I have been quite pleased with the advice and assistance I received from Mr. Moss.
He has some kind of a subscription service you can sign up for which gives you access to 100 videos for $9.99, I've learned a lot.
I have been quite pleased with the advice and assistance I received from Mr. Moss.
He has some kind of a subscription service you can sign up for which gives you access to 100 videos for $9.99, I've learned a lot.
It is amazing to me how much misunderstanding and disinformation is out there about suspension. Even this supposed "expert" either doesn't understand it, or (hopefully) is just explaining it wrong.
Changing the preload on a spring, either on the rear shock or on the front forks, does NOT make the spring stiffer. Spring stiffness is purely a function of how the spring was made and will not be changed by adjusting preload. A spring's stiffness will determine how far the suspension will move in reaction to a particular input (bump in the road) absent any damping. That will not change with preload adjustment.
What the spring preload adjustment will do is to change the ride height of that end of the bike, which will result in a variation of the steering angles, and a very small (insignificant really) variation of weight bias front to rear.
Using a heavier 10W suspension oil in your forks will not improve your range of adjustment unless you were previously unable to achieve adequate damping when you cranked the adjusters down to full closed (CW). I've never heard of that being an issue with the thinner stock oil. OTOH, by increasing the viscosity of the oil you will be increasing the damping through the non-adjustable "fast response" circuits of the fork cartridge's valves, which will be detrimental to the fork's ability to follow road contours.
Similarly, the problem with cranking in more (low speed) compression damping to reduce brake dive on the stock forks is that the side-effect is to stiffen the fork's high speed response to inputs too, and so becomes less compliant and harsh.
Changing the preload on a spring, either on the rear shock or on the front forks, does NOT make the spring stiffer. Spring stiffness is purely a function of how the spring was made and will not be changed by adjusting preload. A spring's stiffness will determine how far the suspension will move in reaction to a particular input (bump in the road) absent any damping. That will not change with preload adjustment.
What the spring preload adjustment will do is to change the ride height of that end of the bike, which will result in a variation of the steering angles, and a very small (insignificant really) variation of weight bias front to rear.
Using a heavier 10W suspension oil in your forks will not improve your range of adjustment unless you were previously unable to achieve adequate damping when you cranked the adjusters down to full closed (CW). I've never heard of that being an issue with the thinner stock oil. OTOH, by increasing the viscosity of the oil you will be increasing the damping through the non-adjustable "fast response" circuits of the fork cartridge's valves, which will be detrimental to the fork's ability to follow road contours.
Similarly, the problem with cranking in more (low speed) compression damping to reduce brake dive on the stock forks is that the side-effect is to stiffen the fork's high speed response to inputs too, and so becomes less compliant and harsh.
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bergmen
Well-known member
Adding to the confusion is the rear spring preload setting on the FJR that has "Hard" and "Soft" as the two positions, inferring that it effects ride "harshness" or "softness", rather than sag or ride height.
Dan
Dan
MCRIDER007
Well-known member
The real confusion on the OEM Shock is that the soft and hard position are not preload settings since the shock is actually a dual spring rate system that does give 2 distinct different spring rates which are not adjustable for spring preload.
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Well, yeah. It does add to the confusion, but maybe not in a way you are expecting. The lever is not a preload (ride height) adjustment.
It actually mechanically locks out the softer stage 1 spring, which means that the stiffer stage 2 sporing is in force for the entire stroke of the shock, so in that case the lever actually does change the initial spring rate from soft to a harder spring. I say initial since after XX mm of shock travel (where the soft spring would be coil bound) the rate is then the same.
In on way that is a superior system as you actually do get a stiffer spring to use when two up, which is what you want with a significantly increased load weight. However, the shock damping cannot be perfect for both spring rates, so that is a compromise, unless you fiddle with the adjuster every time you flip the lever.
I see that MCRider beat me to the punchline with fewer words.
It actually mechanically locks out the softer stage 1 spring, which means that the stiffer stage 2 sporing is in force for the entire stroke of the shock, so in that case the lever actually does change the initial spring rate from soft to a harder spring. I say initial since after XX mm of shock travel (where the soft spring would be coil bound) the rate is then the same.
In on way that is a superior system as you actually do get a stiffer spring to use when two up, which is what you want with a significantly increased load weight. However, the shock damping cannot be perfect for both spring rates, so that is a compromise, unless you fiddle with the adjuster every time you flip the lever.
I see that MCRider beat me to the punchline with fewer words.
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