what is installed preload on a fork spring and how do we measure it?
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- čas přidán 23. 07. 2011
- home.php#!/da... we take a Kawasaki 636 fork and remove the internals in one piece to show you how preload works and what the range is for this particular fork.
You sir are the kind of guy that makes CZcams awesome!! Wealth of free quality information with no added BS. My only regret is not watching these videos sooner
Thanks for the kind words. My hope is that the information here is used and then you "Pay it forward" with local riders and friends to help me with my mission of saving a life every day through education. That starts with a conversation of "Are your settings stock? Why?"
Thanking you Dave,really helpful videos.I was unsure of changing oil in my Grom's Usd's.After watching a few of your vids its easy.I drained the stock oil(5w?) and replaced it with the same quanity in 20w.Works great with the spacer mod also.
Nice work!!!!!
you are awesome, I learn alot from your you and your videos, make my track days better and more safety I have zx10r 2005 really hard to ride at my first days and then after see your videos I'm able to set up my suspension not at 100% but alot better thanks (Sorry for my English)
Good work, keep working on it and make sure that you record your changes as that information is very important :)
Not necessarily higher by that much! Sit on the bike and have someone measure the bars to the ground, then remeasure after the fork preload change with the forks in exactly the same position. The relationship between installed preload and height is not a linear one.
Hi dave aprisiate to excellent vids and wanted to ask a pesifid question about the preload settings I've set them at a good starting point and the bike rides very well but at high speeds the front feels like its bouncing on the top of the road so I've droped the forks 2mm which makes this problem better but now the rear keeps spinning when driving out the turns can you advise away of further adjusting the rear
Holds the spring under tension rather than allow it to flop around inside, and pre-tensions the top out spring in the cartridge. That measured tension then also helps with adding preload to set sag and help with brake dive.
Put the forks back and add rebound damping to the front forks. They are topping out so you need to make sure that stops happening via the rebound adjuster.
the rebound screws need to be reset, so check he owners manual to see how many turns/clicks there should be. Take it all the way to the left, and then go back clockwise to the correct number of clicks and turns.
Very interesting Dave. I have a DRZ400E and I cant find any information on what the fork pre-load should be, even as a ball park. If the rear is around 100 mm of sag what should I be looking at for the front?
33-35% is the general rule for all so for the front 120-130mm is a good starting point
Hello, I have a Trek Marlin 7 2018, and on my forks i have a lock option and a preload option, that goes + and -, but what happens if it is all the way on + or -?
Reduced or more travel, so testing is always fun. Turn comp all the way in and see how much travel you lose, and then take it all out and see how close you get to bottom out at 100mm of total travel.
Hi Dave,
Just got a new softer spring for my Showa BPF (Honda CBR1000RR 2012). Original spring is 230mm, 10,1N/mm, and new spring is 235mm, 9,5N/mm (K-Tech). So it will add 5mm installed preload. I don't know the original installed preload. Preload adjuster spans 16mm (64 clicks). I assume some of the installed preload will be taken up by the top out spring. Am I okay will this new spring length?
Absolutely okay, you will need less preload on the adjuster. Set static sag to 12mm when the shock is cold and start from there :)
It should not be noticeable if static sag is set correctly and matched with rebound damping.
Hello sir, I have a Harley Davidson and swapped out my stock front fork tubes with+2 tubes and patriot genesis springs along with pre load adjusters. RWD shock in the rear as well. I’ve seen others cut the spacer flush with the top of the fork tube and some about half an inch above. Which would you recommend? Thank you.
Prior to rebuilding the forks, check the OEM spring and spacer length and compare to what you are upgrading with. Also measure the amount of threads that screw into the cap. If you have over an inch of threads to screw in, cut the spacer flush with the top of the tube when fully extended.
Dave Moss Tuning I will try doing that tonight. Thanks again.
Hi Dave, question, does this numbers/info apply to a progressive springs ? ( on a dual sport bike ). Thank you !!! Great videos and info. !
Thank you! Yes, the information applies to both linear and progressive. In general, progressive springs can take up to 20mm of preload via the spacer but in so doing, the oil viscosity must be able to control the energy release.
@@catalystreactionsbw Got it. thanks so much Dave !!
Dave, you indicate in this video that you want to keep the same "length". However, the racetech springs to replace the OEM springs are much longer. they say to cut the spacer. does having "more" coils of spring change anything? or by cutting the spacer, is it effectively just accounting for the extra length and doesn't change the functionality of the system? Thank you! --Justin
When you calculate the OEM spring & spacer length, replacement springs normally require the spacer to be cut and sometimes that means new holes for the spring compressor. I choose to check the OEM installed preload and note the amount and correct spacer length for the 10-15mm I prefer.
Hi Dave! Question: I am thinking of replacing my OEM front fork springs for my 2016 Kawasaki Concours 14 for a stiffer spring. OEM is 1.2kg/mm and I am thinking of replacing with a 1.3kg/mm (Racetech recommended for my weight and riding style a 1.36kg/mm, I can't find that anywhere). Anyways, eom length is 244mm uninstalled free length, the replacement will be 250mm. I heard I just need to modify the preload spacer to accommodate the 6mm difference. If I do that, wont I need to move the holes in the spacer too? What purpose do those holes serve? Thanks so much in advance! 💯👊
The holes in the spacer are for the fork spring compressor. at 6mm longer for the new spring, that changes the installed preload slightly but not by much so it might not be necessary to trim the spacer. You will need to change oil viscosity to manage the new rate as stock damping will be quickly overpowered by this rate.
@@catalystreactionsbw thanks once again Dave! I have no idea what fork oil is in it (I'm the second owner and everything is stock and the last owner told me he never changed the fork oil). The manual says KHL 15-10, which doesn't say what weight it is. So... I am gonna say it is 5wt and maybe I should be using 10?... I am 220lbs. Any words of wisdom?
@@ManCalledHorse I used 10w to the stock volume in my stock C14 forks and that worked well for the most part with general touring. I drained then for 24 hours with a simple oil change to make sure I got as much debris out as possible (24,000 miles).
@@catalystreactionsbw that is great to know! I watch all your videos and learn so much. If I do a lot of canyon carving, 10w should still be good? I live in San Diego and hit the Twisties as much as I can 🙂
@@ManCalledHorse Yes, 10w would be my choice.
Hi Dave love the video. Just had fitted new KTECH 10N springs to my Suzuki GSXR 1000 2004 forks. Rider sag with all preload out 38mm. The spacer was cut by 5mm as new springs turned out to be 5mm longer than OEM. At this setting zip tie ended up at 34mm from bottom out. Changing spring seemed to affect how much rebound I needed and I ended up with compression damping fully out.
Given that required installed preload may be lower for stronger spring do you think I ought to have spacer shortened further to give me some useful adjustability back? You hinted at range between 8 and 15mm giving a degree of option?
did you ever get the answer to this ?
Hi Dave, I have a 21 year old Montesa Cota 315r.
Even when I add full pre load, I still get a lot of slack when I pull up on the handle bars. 30mm approx'
Would this be normal? or have the springs collapsed over time?
Kind Regards, Dave K.
Static sag on forks is 25-35mm, so your number is normal. You can increase spacer length by 5-8mm with washers or make a new spacer. Springs were very soft back then. How old is the fork oil?
@@catalystreactionsbw Hi again Dave, thank you so much for your prompt reply sir. Very much appreciate your help.
I have owned the bike for only a few months and the only service history I have suggests that the fork oil is more than 10 years old.
Regards, Dave K.
@@davekelly7184 probably 15w fork oil to start to the volume in the manual. If there is no manual, start with oil height at 140mm. If it bounces around with 15w go straight to 30w.
@@catalystreactionsbw The bike will be out of action for a new clutch soon so that will be an ideal time for me to change the fork oil.
When you say oil height, is that the length of exposed suspension travel at rest?
Once again, thank you for your help and advice. Dave K.
@@davekelly7184 Fork collapsed, no spring or spacer, measure from the top of the fork down to the oil.
how is it when the preload adjuster itself is removed, you can get it back
Not sure what you are asking. Preload via the manual adjuster adds more stress on the spring on top of installed preload. The preload adjuster is in the cap, so if the cap is removed, the second measurement shows the installed preload.
what does the preload acturly do?
It sets pressure on the spring to hold into the coil over unit when no vehicle weight is on it. That is the only thing it does
@@phoenix21studios You responded 9 years after he asked that question.
My guy got married, had kids, sold his motorcycle to buy a station wagon, sold his station wagon to by a crossover and is now considering an electric vehicle.
If the preload is maxed compressing the spring does that mean the spring is incorrect even if settings are within range.
If preload is maxxed out, it can mean oil level is too low, compression settings are too soft or the front is carrying too much weight. If oil level, settings are geometry are correct, installed preload needs to be measured (video on that topic) to see if the math is correct internally. If the math is correct, then are you dealing with a linear or progressive spring. In each case, if the math is right a stiffer spring is required
Dave Moss Tuning thank you for responding do fast !!
I have been getting a wavy type of oscillating feeling riding the bike hard at the track? I'm getting better, faster it happens with acceleration especially when on a banked or uphill turn coming out onto any straight away say Thunderbolt NJMP any ideas? I am assuming that the suspension shop I am going to is correct with setting my bike up math stuff...(although I don't like that the preload is maxed out) racetech springs .95 gold valve kit front Nitron track shock rear. Fairly new tires power cup evos, I switched my bike with Glen Goldman at a TPM track day and he experienced the same so it's not me screwing up with body positioning. I am 162 pounds without gear.
The shock is too stiff or too soft, or the tire pressure is too low. Start with more and then less preload, then more of less compression, then more tire pressure last
I'm sure you were an andrenaline junkie... You are more technical than the most show off bikers with youtube views today
Unfortunately no, I was more focused on mastering challenges and in turn gaining the knowledge how to do so for future challenges
Do u have any info on harley-davidson dyna suspension set up
At this point we have no Harley Videos. I do have generic information regarding ergonomics, pressures, fork oil and geometry as well as shock preload tuning.
@@catalystreactionsbw iv just installed yss piggyback shock an racetech springs hold valves 2 inch taller dampening rod's. I'm very keen on any info or help
@@diesel5460 set sag at 35-40mm for the forks and 30-35mm for the shock. Assess fork and shock travel used to see how close or far away from bottom out you are. Once the oil is hot after 30 minutes or so, set rebound as best you can.
@@catalystreactionsbw thank u for your help appreciate it
So if you add preload, the fork will extend... now I'm cofused. I though when you add more preload you add more pressure on the spring.
Common confusion. Th fork is two pieces. Bolted tube in the triple clamp and moving tube. When you add tension to the spring, it resists travel more and in doing so it can push harder on th moving part. That reduces static sag and makes the forks longer as there is more stress pushing down on the moving part. Does that help?
@@catalystreactionsbw Thank you so much. It makes sence know 👍🏻
@@Striple A lot of people see a tensioned spring as shorter so the forks MUST be shorter by default so now you can help others who are confused too :)
@@catalystreactionsbw Haha we'll do.👍🏻
So PreLoad is basically like the seat pressure of a valve spring @ installed height?🤣
Great analogy, yes.
I can’t tell if ur American or English lmao
Englican :)