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I have my suspension set up and it feels great but I it dives hard under braking. Can I just increase the high speed compression? I want to keep the feel but make it duce less when I rack the brakes. I almost bottom out under braking but in corners I only compress it 2/3 of the way. I only weight 150 in gear
 

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Discussion Starter · #3 ·
Sag is set.
 

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Sounds like a preload issue to me if you're using all the fork travel while on the binders.

How much travel are you using? You got a ziptie on the fork leg?
 

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I have my suspension set up and it feels great but I it dives hard under braking. Can I just increase the high speed compression? I want to keep the feel but make it duce less when I rack the brakes. I almost bottom out under braking but in corners I only compress it 2/3 of the way. I only weight 150 in gear
Then you need your suspension "reset" to accommodate your braking skills. ;)
The fast guys use the brakes to settle the front end before turning. Given the same entry speeds, there is very little chance you can use all the stoke of the suspension without the brakes unless its sprung really soft.
I believe there is a pov video of Simon Crafar riding a stock gsxr with some suspension/tires on it that shows exactly how the forks act under heavy acceleration & braking. Even he (a former WSB/GP rider) doesn't use all the stroke.
You can test this on a vacant street. Accelerate to 100 then back to zero as hard as possible (without crashing). You can do it a couple times so the fork oil has a chance to get up to temp. Reset your preload or spring rate from there.
 

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Discussion Starter · #6 ·
Sounds like a preload issue to me if you're using all the fork travel while on the binders.

How much travel are you using? You got a ziptie on the fork leg?
I have a zip tie and it sits about a inch maybe a tad less from the bottom. I have video of my forks working and in turns i only use the top half of the stroke.

Then you need your suspension "reset" to accommodate your braking skills. ;)
The fast guys use the brakes to settle the front end before turning. Given the same entry speeds, there is very little chance you can use all the stoke of the suspension without the brakes unless its sprung really soft.
I believe there is a pov video of Simon Crafar riding a stock gsxr with some suspension/tires on it that shows exactly how the forks act under heavy acceleration & braking. Even he (a former WSB/GP rider) doesn't use all the stroke.
You can test this on a vacant street. Accelerate to 100 then back to zero as hard as possible (without crashing). You can do it a couple times so the fork oil has a chance to get up to temp. Reset your preload or spring rate from there.
I understand braking and trailing into the turn to keeps the forks compressed so it just flows thru the turn. I just don't know how to fix it. I don't have a suspension guy close, I've always done my own work on things.
I'm 150 lb in gear with complete stock suspension except fluid. I was thinking the high speed compression adjuster would help with how hard it dives. It could be my fault I grab the brakes hard! I've had the rear tire lift up a few times lol so maybe i'm doing it wrong.
 

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all that.. and oil level is what controls bottoming. Springs are what keep the bike working in a particular area of the stroke, but even with 1.0 fork springs, (comes with .925 or .90 i think) you can bottom forks under hard braking with low oil level. Add 5mm at a time. this will keep the compression/rebound the same, and will have nearly exact feel you have now but will keep fork from bottoming once you have the level right.
 

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I understand braking and trailing into the turn to keeps the forks compressed so it just flows thru the turn. I just don't know how to fix it. I don't have a suspension guy close, I've always done my own work on things.
I'm 150 lb in gear with complete stock suspension except fluid. I was thinking the high speed compression adjuster would help with how hard it dives. It could be my fault I grab the brakes hard! I've had the rear tire lift up a few times lol so maybe i'm doing it wrong.
What melka suggested is probably the easiest thing to do without major changes/disassembly. Just write yourself a tech note to measure how much oil comes out of the forks next service.
 

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Discussion Starter · #9 ·
Alright thanks. To be honest I have no idea what the oil level is. I drained it into a ratio rite and poured that much back in. a heavier oil would slow things down all over right?
 

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Alright thanks. To be honest I have no idea what the oil level is. I drained it into a ratio rite and poured that much back in. a heavier oil would slow things down all over right?
of course it would.. but why would you do that when you haven't ran out of adjustment on the adjuster knobs. or more importantly, added oil to solve the bottoming issue first. I thought you like the way the bike feels otherwise?

keep in mind that what you pour out, is NOT the same oil volume that is going back in if you dismantled the forks and cleaned everything. even swapping fork springs out you loose 1ml or so if you don't let em drip awhile..
 

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Discussion Starter · #11 ·
of course it would.. but why would you do that when you haven't ran out of adjustment on the adjuster knobs. or more importantly, added oil to solve the bottoming issue first. I thought you like the way the bike feels otherwise?

keep in mind that what you pour out, is NOT the same oil volume that is going back in if you dismantled the forks and cleaned everything. even swapping fork springs out you loose 1ml or so if you don't let em drip awhile..
I don't plan to add a heavier oil I was just making sure what I thought was right.
When I drained them I didn't disassemble I just slid the upper tube down and hung them upside down over night while they drained. I used almost a liter between both forks if I remember right.
I plan to add fluid and see how that goes. I think a spring wouldn't help because it'swhere it needs to be in turns. a spring rate change would change that too correct?
 

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I don't plan to add a heavier oil I was just making sure what I thought was right.
When I drained them I didn't disassemble I just slid the upper tube down and hung them upside down over night while they drained. I used almost a liter between both forks if I remember right.
I plan to add fluid and see how that goes. I think a spring wouldn't help because it'swhere it needs to be in turns. a spring rate change would change that too correct?
would likely increase spring rate for tracks with a lot of heavy braking, or where the bike is loaded in fast sweeping turns, or a tack like barber where the bike is gonna "g-out" compressing suspension due to the corners that rise in elevation..
to make heavier springs work, pace needs to increase, not just being a heavier rider (which you are not).
i don't know what the volume of oil is (i'm sure the manual would show that but i have never had OEM forks), but if you are SURE you are bottoming forks i would add some oil level. no more than 10mm to start. It's way easier to add oil, it's hard to take it out.
 

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I'm really enjoying the methodology behind your approach, Greg. Are you sure you aren't becoming a suspension guy on the side? :flex:
 

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I'm really enjoying the methodology behind your approach, Greg. Are you sure you aren't becoming a suspension guy on the side? :flex:
lol.. i know just enough to get OTHERS in trouble Dan :)

seriously though, working with some good tuners and paying attention on track to changes being "better or worse" has given me some background. Still have never cracked open a set of forks myself though ! so don't "retire" or anything from this forum.. ;)
 

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lol.. i know just enough to get OTHERS in trouble Dan :)

seriously though, working with some good tuners and paying attention on track to changes being "better or worse" has given me some background. Still have never cracked open a set of forks myself though ! so don't "retire" or anything from this forum.. ;)
I'll bring a set for rebuild to the next race weekend. We can rebuild over a beer :cheers.

I've long believed that when you demand performance from a machine, the more understanding you have about the machine, the better you can perform. You are proof. That's the reason I spend so much time on Forums trying to get people to learn.

Often on brake dive I try to differentiate between distance traveled and speed traveled. While both high speed damping and oil level changes can alter the dive, it's better to understand which is the true problem. Too fast: add a small amount of high speed compression damping. Too far: add to the oil level as you indicated. And of course, keep as many notes as possible. I'm learning a lot of things to add to trackday/race setup sheets from Dave M. Love the amount of info he shares. Can't wait for his books. :fact
 
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