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Good video as always Charles! If I may though...I would recommend anyone to get this:

Fork Oil Level Tool | Motion Pro

It's used for measuring the level fluid in the forks, and it's much more accurate than trying to measure the volume of the fluid you took out and measure the same amount to put back in. Plus you'll know exactly what the level is in each fork, so you can set them equal to each other (mine were not quite equal from when they were serviced by someone else before). The amount specified in manuals is usually just what they're set at from the factory, and it's a good recommendation, but one might want to put more or less to change the air spring in the forks, and I'm not sure how Showa does it, but a lot of times you'll see specifications in terms of fluid height level, not volume. I know Ohlins does this from what I remember when I did mine. Of course you'll know volume too, because the motion pro tool uses a syringe.
 
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Discussion Starter · #3 ·
Thanks Rub!

I was going to buy one of those tools a few years ago when I started doing my own fork oil changes, but the 848 does not list fluid height specifications, only volume (439cc in my case with the 848). I wasn't really sure how much was in there until I renewed my fork seals last year, and it was very close to 439cc (the black line on my measuring container in the video), which is the recommended amount in the user's manual.

I wanted a little more support for one of the 'bumpy' tracks that I ride, and I suppose I could have added more oil, but I opted to use a higher viscosity fork oil which worked out well for me. I might go ahead and buy one of these tools, though, because I want to tinker a little more with the suspension in between the 'bumpy' and smooth tracks that I ride. I'm fairly certain that I could remove a few cc's for the smoother tracks, and this tool would make that task a lot easier!
 

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Yep, you sure can. You can suck up however much you want, and add however much without dumping all the fluid out. Plus if you know you have 439cc like the manual says, you can measure your "baseline" so you'll know the height from now on and adjust from there.
 

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Damnit Rub now I need Charles to update the video with this device 🙃

Great video Charles I now feel I can tackle this over the winter.


I'm a bit of a bull in a china shop, your videos slow me down for the details! Gives me the confidence I need.
 

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Damnit Rub now I need Charles to update the video with this device 🙃

Great video Charles I now feel I can tackle this over the winter.


I'm a bit of a bull in a china shop, your videos slow me down for the details! Gives me the confidence I need.
There already are multiple videos showing how to perform basic servicing of the forks, in which the motion pro device is used. How do you think I figured out how to do all of that?? :eek:
 
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There already are multiple videos showing how to perform basic servicing of the forks, in which the motion pro device is used. How do you think I figured out how to do all of that?? :eek:

I find Charles videos superior and its specific to my bike 👍
 
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I agree. When I learned, this wasn't available, so I had to find other sources. Luckily found 3 good ones pertaining to the same Ohlins forks I have, two of which were from STG and Dave Moss.
 
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Discussion Starter · #10 ·
I agree. When I learned, this wasn't available, so I had to find other sources. Luckily found 3 good ones pertaining to the same Ohlins forks I have, two of which were from STG and Dave Moss.
Can't go wrong with STG or Dave Moss... they both have some excellent videos, and Dave for sure is more knowledgeable than I am when it comes to suspension. And the last time I checked, STG had the best price on Ohlins fork fluid with free shipping (that's where I buy mine!)

I'm now more curious about how my 848 will respond to the removal (or addition) of a few cc of fluid. At Nelson ledges, the bumpiest track that I ride, I'll leave it at 439cc--I already know for the 23 cST this is the right amount for that track. I'll experiment at PittRace, MidOhio and NYST, all of which are much smoother and in better condition than Nelson's.
 

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Can't go wrong with STG or Dave Moss... they both have some excellent videos, and Dave for sure is more knowledgeable than I am when it comes to suspension. And the last time I checked, STG had the best price on Ohlins fork fluid with free shipping (that's where I buy mine!)

I'm now more curious about how my 848 will respond to the removal (or addition) of a few cc of fluid. At Nelson ledges, the bumpiest track that I ride, I'll leave it at 439cc--I already know for the 23 cST this is the right amount for that track. I'll experiment at PittRace, MidOhio and NYST, all of which are much smoother and in better condition than Nelson's.
Think of it as another preload feature. A fork is essentially a closed pressure vessel system. The 2 fluids inside are the oil and air. Oil is pretty close to incompressible, but air is obviously not. So the more oil you put in, the less air you have in, which gives it the same effect as adding more preload, because less air means less stuff to compress. Think of an empty syringe where you plug the needle hole and then push the plunger in. You'll notice it goes in a bit then it will go back, because you just compressed the air inside, but then it pushed it back just like a spring. Now set the plunger at like 5 ml, and then 50 ml, and see the difference...which one goes farther? It's a great thing to have when you're pretty much on the edge, like my bike was. I was pretty close to being maxed out on my preload, but every now and then I was still bottoming out the forks in a particular turn (or two). Rather than buying new stiffer springs, I added 10 or 20 cc of fluid in each fork and that solved that problem. Then it was pretty much perfect, and I could brake harder without worrying about the forks bottoming.

There's probably more science behind this, especially once you add temperature into the equation...but I'm no expert, so I'll just stick to the basics that I know for now :)...but all in all, regarding what you said, I doubt you'll notice any difference due to the track surface. Preload is not really something you adjust because of the bumpiness of the surface. You'll need to play around with compression and rebound to make it feel better on more or less bumpy tracks.
 
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A lower oil level translates to a less progressive stroke. All forks come with way too much oil in them.This keeps the show room bike from sacking out under a heavy, ham-fisted rider, and still reasonably cushy for little people. I use a higher oil level at tracks with a lot of heavy braking. And a lower level at more flowey venues. That said, im always at least10 to15 mm lower than oe recommendations. But don't just start lowering your oil level to get the linear travel untill you are on the proper springs, with correct preload, lest you blow through the travel on the brakes and bottom out and crash.(ask me how i know this)... As far as viscosity, in the showa you can get more responsive clickers with thicker oil, but i would be cautious. And in the fgrt or any other aftermarket ohlins you dont want to deviate from the Ohlins spec stuff. Fork oil level is basic suspension tuning 101. The more you experiment, the more you will learn about this.
 

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So with the exception of the preload statement, every thing rub says is spot on. More science or not, he did what every race team in the world would do, sacking out on the brakes, rase oil level (assuming that everything else is ok). But as every married man knows, you gotta give to get. So Rubbish is not blowing through the stroke on the brakes now, but too much oil won't let the fork get all buttery deep in the stroke while on the edge of the tire, where you need to keep the bumps out of the chassis. This is the compromise. If you're not sacking out on the brakes, and not skipping over the bumps in the turn, then don't worry about the oil level. If anything, raising the oil level for a bumpy track will merely make the fork more harsh.
The only bike i know of (that can be obtained by mortals) with an adjustable progression rate in the rear is the panigale. And it only has 2 settings; way to much, and not quite as bad. The fork on every motorcycle made has an infinite progression adjustment range with the oil level, so racers can dial it in to get the best feel and most feedback possible.
 

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That's why the recommendation is usually to go in increments of 10cc or so when adding or removing. Little changes at a time.

But why do you say with the "exception of the preload statement..."? It really it sort of a preload feature. Just like when you crank up the preload, it takes a greater force to compress the forks to a certain level, adding more oil has the same effect. You'll need a greater force to compress them to that same level. Try it out for shits and giggles and fill 'em both all the way up...see what happens ;) (just don't go out on track with them full :D)
 

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Preload is essentially a fine tuning of your spring weight. Cranking in an ass ton of preload to keep the front from sacking out will have an effect on the entire stroke. It will make the fork more harsh overall, make it difficult to get the front compressed for your turn in, and make it want to come up too soon when you transition off the brake at the apex. Leaving you to play stump the stars with your compression and rebound clickers to try to overcome, causing unnecessary compromises elsewhere on the track.
Whereas a change to the oil level will only effectively change the bottom third of the stroke. Ok, imagine you like the front everywhere on the track, but it bottoms at hard braking points. So rase the oil level like 10 mmor so, and bam, the fork still feels good everywhere but no longer bottoms at those spots. There goes a half a second from your lap. Or, suppose the fork works well, but some bigass bumps are putting you wide or rattling the chassis in the middle of that fast turn. Suck out some oil, and it will make it more plush at that lower part of the stroke you are in when folded into the turn.
 

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Preload is essentially a fine tuning of your spring weight. Cranking in an ass ton of preload to keep the front from sacking out will have an effect on the entire stroke. It will make the fork more harsh overall, make it difficult to get the front compressed for your turn in, and make it want to come up too soon when you transition off the brake at the apex. Leaving you to play stump the stars with your compression and rebound clickers to try to overcome, causing unnecessary compromises elsewhere on the track.
Whereas a change to the oil level will only effectively change the bottom third of the stroke. Ok, imagine you like the front everywhere on the track, but it bottoms at hard braking points. So rase the oil level like 10 mmor so, and bam, the fork still feels good everywhere but no longer bottoms at those spots. There goes a half a second from your lap. Or, suppose the fork works well, but some bigass bumps are putting you wide or rattling the chassis in the middle of that fast turn. Suck out some oil, and it will make it more plush at that lower part of the stroke you are in when folded into the turn.
Agreed! I think my mind was thinking the same exact thing but I wasn't able to put it down in writing as clear as you. But yeah, that's where I was trying to get to with my explanation :)
 

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Yeah, its the terminology.
When i was little, my dad would set up the bikes. He knew basic things to do when something wasn't right. However, he usually didn't share much. There wasn't much point, as we were just little punks. So i had to figure things out on my own as an adult. And, for a long time, i was just riding a shit setup. I just pushed till i would crash. When you get to the point where something the bike does keeps you from faster lap times, it pays huge to pick the brain of a good chassis guy. Also, trying different setups, good or bad, will go a long way towards personal knowledge. If you keep notes its easy to undo something that doesn't work
 

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Hey rub, not to digress, but i bought a sprinter van last week. And ive been working to make a race track RV out of it. So perhaps in the spring (we really don't have seasons here) im planning to embark on a race track tour of the US. Track days only. Some clubs let you do their practice days even if you dont have a license with them
 

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Discussion Starter · #19 ·
Preload is essentially a fine tuning of your spring weight. Cranking in an ass ton of preload to keep the front from sacking out will have an effect on the entire stroke. It will make the fork more harsh overall, make it difficult to get the front compressed for your turn in, and make it want to come up too soon when you transition off the brake at the apex. Leaving you to play stump the stars with your compression and rebound clickers to try to overcome, causing unnecessary compromises elsewhere on the track.
Whereas a change to the oil level will only effectively change the bottom third of the stroke. Ok, imagine you like the front everywhere on the track, but it bottoms at hard braking points. So rase the oil level like 10 mmor so, and bam, the fork still feels good everywhere but no longer bottoms at those spots. There goes a half a second from your lap. Or, suppose the fork works well, but some bigass bumps are putting you wide or rattling the chassis in the middle of that fast turn. Suck out some oil, and it will make it more plush at that lower part of the stroke you are in when folded into the turn.
Good info here, Ductard; I really feel that I've hit a sweet spot with these stock Showa forks. My preload is ALL of the way out. In getting there, every turn or two to test the feel on the track felt better and better until I ended up with no preload at all. This was in conjunction with a final drive change (15/41, which resulted in a longer swingarm distance and lower center of gravity). I believe that change also shifted some of the weight bias to the front, and somehow I ended up with a setup that feels really good. I'm not a racer, and not a track record holder, so I don't believe I'll be able to out ride the capability of these forks any time soon.

Hey rub, not to digress, but i bought a sprinter van last week. And ive been working to make a race track RV out of it. So perhaps in the spring (we really don't have seasons here) im planning to embark on a race track tour of the US. Track days only. Some clubs let you do their practice days even if you dont have a license with them
If you make it to Ohio, schedule a stop at the Mid-Ohio Sports Car Course, it's a great track, and it would be a pleasure to show you around!
 

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Hey rub, not to digress, but i bought a sprinter van last week. And ive been working to make a race track RV out of it. So perhaps in the spring (we really don't have seasons here) im planning to embark on a race track tour of the US. Track days only. Some clubs let you do their practice days even if you dont have a license with them
That sounds like an awesome road trip! Wish I had the time and money to do something like that :)

If you come by the middle of the country, I would certainly recommend MPH (Motorsports Park Hastings, in Hastings NE). I will guarantee you that so long as it's dry, you will have a blast, and if you're there on a Saturday you'll enjoy a great free dinner with our local Trackaddix family.
 
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