Harsh Cer Forks.
- Thread starter Vince
- Start date
Shajota
Hero member
- Location
- Whitsundays Qld
All good, got em Vince. Found some industrial rust loosener that I acquired from somewhere, sprayed it around the top and pushed ball in and sprayed from below as well. Got some good leverage with a stilson on the screwdriver and they cracked. All good, nothing damaged..........Now just to work out best settings fro emulators and air gap and go again...................Vince said:
My Cerianis are at 2 1/2 turns of preload with the blue spring and 2 holes in the plate on the emulator, 15wt at 130mm springs and emulators out and fully compressed.
After doing The Thunderbolts bumpy way a couple of weeks back I am going to try 3 holes in the plate. I am pretty heavy though. The 3 holes will be about the end of my experimenting as that's about all I can do. If 3 doesn't work it's easy to maybe solder up the last hole.
It's great on reasonable roads but in real crappy roads, I still get some thumping through the bars on municipal small bumps.
After doing The Thunderbolts bumpy way a couple of weeks back I am going to try 3 holes in the plate. I am pretty heavy though. The 3 holes will be about the end of my experimenting as that's about all I can do. If 3 doesn't work it's easy to maybe solder up the last hole.
It's great on reasonable roads but in real crappy roads, I still get some thumping through the bars on municipal small bumps.
Did nothing except re read
http://www.racetech.com/page/title/Emulators-How%20They%20Work
Seems the holes are low-speed compression and I need to work on high-speed compression, big square edged bumps, that's emulator spring preload. I think I made the mistake of using the same preload I had on the original to stiff spring, 2 and a bit turns and I think I need more preload now it has the softer spring. Would be a good test to try this before Sundays breaky run to the bloody bumpy Wisemans Ferry area. MUST PULL FINGER OUT.
http://www.racetech.com/page/title/Emulators-How%20They%20Work
Seems the holes are low-speed compression and I need to work on high-speed compression, big square edged bumps, that's emulator spring preload. I think I made the mistake of using the same preload I had on the original to stiff spring, 2 and a bit turns and I think I need more preload now it has the softer spring. Would be a good test to try this before Sundays breaky run to the bloody bumpy Wisemans Ferry area. MUST PULL FINGER OUT.
Call me literal, we had a discussion about fork setup at the last club night and it got to sag versus spring preload. According to xxx, unnamed person, Terry Hays told him that all you need to do with the correct rated springs fitted was at add 10mm of preload and not to worry about sag measurements. So as an experiment I just did that. I had 10mm of washers stacked to get the 1/3 sag measurement. The less literal bit about this post is, I thought 10mm preload didnt include the fork cap screwing into the leg that adds 20mm of preload from said cap. So its quite a bit more compliant now. Be interesting to see if it reduces the kick I was getting on square edged big bumps on Sundays ride. Rebuilt Icon shocks fitted as well.I love to see what happens with any change for myself.
Tried a couple of things on this Sunday ride, not the bumpiest road out of Sydney but it had enough to test what I had done. Last club night the discussion went to fork preload as one of the blokes had been doing his think on this. From the suspension bloke we both have used the latest thing is forget sag dimensions, just use 10mm spring preload so I gave it a go but did a sag measure to see what would happen. So with 10mm preload, that does NOT include the fork screw cap BTW
I got 47mm of sag. With my usual number of washers packing the spring,5. I got 36mm of sag. So it makes a fair bit of difference. I took a quick spin around the block with the lesser preload and didnt like the result, I have longer shocks and the forks through the trees and with this bigger sag it felt a far bit twitchier. The next experiment was after lots of thought as to what I was trying to dial out. On really big bumps the bike kicks hard and on smaller bumps into corners, I would get this small bouncing feeling through the bars. I am thinking I don't have enough rebound damping to absorb the spring effects, so I tried some 20 wt fork oil at my usual 130mm fork fully compressed and springs and emulators out and I really liked the result. Much reduced kicking of big bumps and no bounce that I could detect. There is an effect called packing where the fork reacts to a bump and doesn't return fast enough to deal with the next bump resulting in the fork freezing, didnt have this happen. Using heavier oil is the only way to slow rebound damping but it affects compression damping as well, I am at 3 turns of preload on the emulator and that's now too hard so its back to 2 1/2 turns and I will see what that does. This is a good result to me in this search for a compliant and working well for me fork. BTW I am a fat bastard at 125kg so this might not work for other applications.
After the emulator adjustment, I will try the reduced to 10mm preload again on a longer ride to check its effect
I got 47mm of sag. With my usual number of washers packing the spring,5. I got 36mm of sag. So it makes a fair bit of difference. I took a quick spin around the block with the lesser preload and didnt like the result, I have longer shocks and the forks through the trees and with this bigger sag it felt a far bit twitchier. The next experiment was after lots of thought as to what I was trying to dial out. On really big bumps the bike kicks hard and on smaller bumps into corners, I would get this small bouncing feeling through the bars. I am thinking I don't have enough rebound damping to absorb the spring effects, so I tried some 20 wt fork oil at my usual 130mm fork fully compressed and springs and emulators out and I really liked the result. Much reduced kicking of big bumps and no bounce that I could detect. There is an effect called packing where the fork reacts to a bump and doesn't return fast enough to deal with the next bump resulting in the fork freezing, didnt have this happen. Using heavier oil is the only way to slow rebound damping but it affects compression damping as well, I am at 3 turns of preload on the emulator and that's now too hard so its back to 2 1/2 turns and I will see what that does. This is a good result to me in this search for a compliant and working well for me fork. BTW I am a fat bastard at 125kg so this might not work for other applications.
After the emulator adjustment, I will try the reduced to 10mm preload again on a longer ride to check its effect
Its been a while so here are my latest changes. The last stuff I did had me a bit confused as to what weight fork oil I was at. Notes, not me. The last 2 rides I was back to feeling pulses through the bars from small square edged hits so I must have gone back to 15 wt as that allowed this to happen. So today I changed back to 20wt again and just to add to the confusion I also changed the oil level from what I have always used. That was 130mm, springs and emulators out and the fork fully bottomed. Now it's 160mm. I noticed some stichion when moving the fork to bleed the air out, so will try a light rub of 20 wt fork oil on the stanchions to maybe lube the seals and dust wipes a bit.I checked what full travel is and it came out at 125mm, with the old oil level I am using 95mm of travel so it will be interesting to see what happens with an air gap that was 130mm and now is 160mm.
D
Davo
Guest
Old adage - never change more than one thing at a time when problem solving. (banghead)
Yes, usually. But. I had tried the 20 wt before and found an improvement in damping control over 15wt. According to the experts, air gap only affects the bottoming resistance and achieving full travel. So it will be reasonable to expect some data. Before the change, it was behaving just like when it had 15wt in it. Suck it and see works for me.
Tippie
Hero member
- Location
- Dr?bak, Norway
Very interesting Vince. It?ll be good to hear the change with more air space. Enclosed air being a non linear spring, you could well have been running into some serious resistance there. From my experience less air gap causes resistance to bottoming, just as your experts say, as you are effectively introducing another spring. I still just go with keeping the oil comfortably over the dampers, and just the one spring to work with.
I was also surprised at what effect 20 wt had, it took away all the small bouncing and pulses I was getting through the bars on your typical bike friendly backroads around Sydney and we have some shockers,pun slipped out.Its noticeably more comfy than the recommended from Race tech 15wt. It's going to be a while till I try the new air gap, rear wheel issues need fixing.
Finally got a chance to do a quick 5-minute spin around the block and waste another day of my log book rego.
So I changed the fork oil hight from my usual 130mm springs and emulators out and fully compressed to 160mm, I expected to use more fork travel.Thats hitting all the crap around including big speed bumps and hydrant covers as hard as I could. With 130mm of airgap I was using 95mm of fork travel, and with 160mm I am now using 95mm of fork travel. Yep exactly the same travel, with the forks completely bottomed that shows 125mm available. I find this very surprising. I really expected there would be a difference with different oil hights. The action with the 20wt oil is fantastic.No shocks through the bars even on big potholes and a nice firm yet responsive action. Be good to know why that final 30mm travel doesn't come into play but I am very happy with what I have.
So I changed the fork oil hight from my usual 130mm springs and emulators out and fully compressed to 160mm, I expected to use more fork travel.Thats hitting all the crap around including big speed bumps and hydrant covers as hard as I could. With 130mm of airgap I was using 95mm of fork travel, and with 160mm I am now using 95mm of fork travel. Yep exactly the same travel, with the forks completely bottomed that shows 125mm available. I find this very surprising. I really expected there would be a difference with different oil hights. The action with the 20wt oil is fantastic.No shocks through the bars even on big potholes and a nice firm yet responsive action. Be good to know why that final 30mm travel doesn't come into play but I am very happy with what I have.
helicopterjim
Hero member
- Location
- near Lone Butte, BC, Canada
Interesting that you are having best results with 20 wt oil. I've been talking to Sports motorcycles about their kit and the say to start with 5 wt. and if you need to go past 10 wt. then you have other problems. Mind you .... their valves may look the same but they have both rebound and compression adjustment. Apples and oranges i suppose.
My bet is it's down to the size of the holes, my Dirtbike uses 5wt and all modern suspension tries to use the lightest oil they can as it moves faster and easier.They want control of tiny movements, be great to achieve that but not on my budget. I am really surprised that in my case 20 wt works so well but that's with exactly my situation, size of holes and body weight. Getting no change after 30mm of change in fork oil hight does also surprise me. There are apparently noticeable changes with 5mm but not to me.
Lately, I have spat the dummy about how horrible the 38mm Marzocchi forks are,std were 35mm but not on this Pantah. So I finally finished this round of mods. I had the fork bottoms Hard Anodised as per the Race tech recommendations, fitted SKF green fork seals and dust wipers. I finally heard back from the US Race Teck bunch and got some advice from Matt their Vintage suspension bloke. He said I should try and extra 2 high-speed damping holes bringing it to 4 holes each emulator, the max you can do, extend the air gap 20mm to 160mm making sure when the fork is extended the emulator is completely covered by oil and that's where its at now. I did a quick spin around the block between freezing cold showers and its considerably better. You couldn't pick it doing the fork bounce trick but the front end now sticks well on bumps, I was confident to push it hard on bends. The only issue is its still only using 80mm of front travel.
That's hitting big speed bumps very hard. Has anyone else tried the cable tie on the fork trick and measured how much travel they use. Maybe that's all its got but they do move to 130mm when its bottomed and the springs are out doing the fork oil level.
That's hitting big speed bumps very hard. Has anyone else tried the cable tie on the fork trick and measured how much travel they use. Maybe that's all its got but they do move to 130mm when its bottomed and the springs are out doing the fork oil level.