Suspension moaning

[Corsara]

What's clear is clear---190lb with no gear is way too heavy for the two OEM weaklinks in the forks of my bike. While having the forks completely serviced and parts replaced sometime in the summer is definitely in the plans, I want to salvage any opportunity to have a somewhat good time at the track between now and then.

At my last track day the forks were completely bottoming out under braking, so the plan for the next track day is to dial in more compression and increase the preload. So I had my wife help with measuring the sag, only to find out the front is completely out of whack, it was apparently standing at 39mm sag at the last track day. With preload all in, sag is 32 mm.

So, as it stands now---front sag is 32 mm, rear is 28 mm. I've read somewhere it's good the front preload to be between 25-30 mm, which is impossible to achieve without changing the springs in my case. But I wonder if there are negative consequences of using all available preload? It's probably give-or-take, so I need to decide if bottoming is worse than ____ (please fill in the blank). Just to clarify, rising the front in my case is not a problem, because it had to go up anyway due to the taller rear race tire to restore the geometry.

 

[gs500f]

Do the best you can. Grab some new springs, and on an off weekend swap them. It shouldn't take u more than 4 hours to do it properly. That includes taking the forks off the bike. If ur in a pinch, pull the caps off and just siphon some oil out and swap the springs, the refill with oil.

I just changed my oil with the siphon method and it took no more than 45 mins from start to finish including clean up.

 

[triggerhappy]

But I wonder if there are negative consequences of using all available preload?

Nope, thats what it's there for. I have mine pretty well full wack and that is how it was set by Kyle at Windmill Motorsports.

 

[Corsara]

Do the best you can. Grab some new springs, and on an off weekend swap them. It shouldn't take u more than 4 hours to do it properly. That includes taking the forks off the bike. If ur in a pinch, pull the caps off and just siphon some oil out and swap the springs, the refill with oil.

I just changed my oil with the siphon method and it took no more than 45 mins from start to finish including clean up.

I've changed the springs myself on normal forks before, but not on inverted. It seems more daunting than just pulling the caps off and swapping the springs, at the very least I need to manufacture some tools to compress and hold the spring..

 

[Corsara]

Nope, thats what it's there for. I have mine pretty well full wack and that it how it was set by Kyle at Windmill Motorsports.

I'm very glad to hear!

 

[gs500f]

I've changed the springs myself on normal forks before, but not on inverted. It seems more daunting than just pulling the caps off and swapping the springs, at the very least I need to manufacture some tools to compress and hold the spring..

My apologies. I've never done inverted forks. Disregard my previous statement lol

 

[Corsara]

My apologies. I've never done inverted forks. Disregard my previous statement lol

No problem I actually had to google images of 2002 zx6r (as listed in your signature) to see if you meant normal or inverted forks

 

[YellowDuck]

32 mm is not an unusual front sag number at all, even for track use. However, to achieve that, you probably now have zero bike-only sag, which is a pretty good clue that the springs are too light (which you already knew). Having the proper sag in no way guarantees that you won't still bottom the forks under braking if the spring rate is wrong.

 

[doozerdave]

32 mm is not an unusual front sag number at all, even for track use. However, to achieve that, you probably now have zero bike-only sag, which is a pretty good clue that the springs are too light (which you already knew). Having the proper sag in no way guarantees that you won't still bottom the forks under braking if the spring rate is wrong.

What he said. You need a small amount of sag with just the bike weight, and the proper sag with you on it. FYI, on my SV, John Sharrard wanted 38mm front and 25mm rear. 4mm rear with just the bike, I don't know about the front, but I have 0.95's in it. If you have to compensate for spring rate with compression damping then it's definitely the wrong spring rate. You'll end up making the comp damping too stiff and not have proper small bump compliance mid-corner, sort of the same deal as bottoming out.

 

[murf]

What's clear is clear---190lb with no gear is way too heavy for the two OEM weaklinks in the forks of my bike. While having the forks completely serviced and parts replaced sometime in the summer is definitely in the plans, I want to salvage any opportunity to have a somewhat good time at the track between now and then.

At my last track day the forks were completely bottoming out under braking, so the plan for the next track day is to dial in more compression and increase the preload. So I had my wife help with measuring the sag, only to find out the front is completely out of whack, it was apparently standing at 39mm sag at the last track day. With preload all in, sag is 32 mm.

So, as it stands now---front sag is 32 mm, rear is 28 mm. I've read somewhere it's good the front preload to be between 25-30 mm, which is impossible to achieve without changing the springs in my case. But I wonder if there are negative consequences of using all available preload? It's probably give-or-take, so I need to decide if bottoming is worse than ____ (please fill in the blank). Just to clarify, rising the front in my case is not a problem, because it had to go up anyway due to the taller rear race tire to restore the geometry.

Just try it out and see how it is. Was the bottoming out causing you problems?

 

[Corsara]

What he said. You need a small amount of sag with just the bike weight, and the proper sag with you on it. FYI, on my SV, John Sharrard wanted 38mm front and 25mm rear. 4mm rear with just the bike, I don't know about the front, but I have 0.95's in it. If you have to compensate for spring rate with compression damping then it's definitely the wrong spring rate. You'll end up making the comp damping too stiff and not have proper small bump compliance mid-corner, sort of the same deal as bottoming out.

The stock springs I have now are 0.85, whereas the RaceTech calculator online asks for at least 1.0 kg/mm for my weight. Thanks for pointing out the potential problems for too much compression, I gotta watch that. Obviously I have to make some compromises here and there, it's obviously a "gain here, lose there" kind of situation..

Just try it out and see how it is. Was the bottoming out causing you problems?

Well, I had new race pads at that day, so took a session to bed them in. After that the bite was insane, I've never had so much braking power, and the feeling braking after the straight at TMP, then before turn 2, and again before turn 6 was giving me the impression my front is slipping. Then I put a zip-tie on the forks, and saw it's completely bottoming out. I don't have much experience yet to be sure, but that's how I explained it to myself---it's bottoming out, and either the front is really slipping because losing contact with the surface due to little bumps....or it's just that the feeling of slipping is actually not slipping, but directly feeling the road in the chasis (when bottomed out). For reference, it didn't feel like the rear is out in the air and coming around---all this happening in a completely straight line.

 

[gsxr guy]

The stock springs I have now are 0.85, whereas the RaceTech calculator online asks for at least 1.0 kg/mm for my weight. Thanks for pointing out the potential problems for too much compression, I gotta watch that. Obviously I have to make some compromises here and there, it's obviously a "gain here, lose there" kind of situation..



Well, I had new race pads at that day, so took a session to bed them in. After that the bite was insane, I've never had so much braking power, and the feeling braking after the straight at TMP, then before turn 2, and again before turn 6 was giving me the impression my front is slipping. Then I put a zip-tie on the forks, and saw it's completely bottoming out. I don't have much experience yet to be sure, but that's how I explained it to myself---it's bottoming out, and either the front is really slipping because losing contact with the surface due to little bumps....or it's just that the feeling of slipping is actually not slipping, but directly feeling the road in the chasis (when bottomed out). For reference, it didn't feel like the rear is out in the air and coming around---all this happening in a completely straight line.

35-38 mm is a good #. Only real fast guys need less sag. To keep fork in its sweet spot mid corner. If you're still bottoming on brakes. Add comp. You may have to use heavier fork oil, until you get new springs.

 

[dricked]

What's clear is clear---190lb with no gear is way too heavy for the two OEM weaklinks in the forks of my bike. While having the forks completely serviced and parts replaced sometime in the summer is definitely in the plans, I want to salvage any opportunity to have a somewhat good time at the track between now and then.

At my last track day the forks were completely bottoming out under braking, so the plan for the next track day is to dial in more compression and increase the preload. So I had my wife help with measuring the sag, only to find out the front is completely out of whack, it was apparently standing at 39mm sag at the last track day. With preload all in, sag is 32 mm.

So, as it stands now---front sag is 32 mm, rear is 28 mm. I've read somewhere it's good the front preload to be between 25-30 mm, which is impossible to achieve without changing the springs in my case. But I wonder if there are negative consequences of using all available preload? It's probably give-or-take, so I need to decide if bottoming is worse than ____ (please fill in the blank). Just to clarify, rising the front in my case is not a problem, because it had to go up anyway due to the taller rear race tire to restore the geometry.

My first track bike (07 Gsxr 600) had all oem components and no setup whatsoever and got me to 1:20 my 4th day. If your not destroying your tires just ride the bike untill you can afford to, or have the time to get your suspension done properly. Your bike is not hurting your laptimes. Keep your forks from bottoming though by adding compression like others have said.

 

[smergy]

changing compression to mask springs that are too light may appear to work at first, but will quickly show up in ride quality ( think harsh/skippy ride ). As you improve, you'll find it harder to really squeeze the brakes into 1, without the front dancing around (since it will skip over bumps instead of absorbing them with added compression). I had my front at 43mm working with John Sharrard using stock springs, not quite bottoming but definitely in the low range of travel. The correct spring rate and type is the real solution. We are not talking ohlins cartridge kit type prices here, around the $100-$150 mark all in, plus some fork oil. Sure its a couple bucks, but you probably spent more on many other parts already. A compliant suspension is definitely worth it. I went from 1.04 progressive stock spring to 1.10 linear racetech spring this year as recommended by John (and I'm about roughly the same size as doozerdave who's using a 0.95!, although the SV is a lighter bike), which was a great move. The racetech site will give you a recommendation and Tony from BlueStreak or John can get them for you. Previously I was doing the same as you did, just add more compression to compensate ( in my case it was for initial front nose dive on the brakes, but the same idea ). Going to a heavier linear spring allowed me to soften the compression allowing for much more compliant bump absorption especially into turn 1. Even if you are not there today (although it sounds like your getting close) you will get to a quicker pace and need the correct solution. Since its not (relatively) tons of money (just time), I suggest making the spring swap sooner than later if your going to do it anwyays.

For the honda's inverted forks, you need a bunch of special tools. For me, it was 2-S clips (out of the strongest coat hanger hooks I could find), some ratchet straps and a vise (when the tube gets oil all over it, which it will, it becomes hard to hold, be VERY careful wtih the vice, clamp on your axle mounts, not your tubes, you can easily deform them).

The images below may give you an idea for the inverted fork. The 1.10 racetechs took a fair bit of effort to get them to compress enough. Loosen the end caps before you take them off the bike, its can be a pain once the fork is off. If you change the springs, I suggest actually taking the forks completely apart and cleaning every piece if you haven't recently, you might be surprised how much crap is sitting at the bottom of the fork. The forks will function better and you get a chance to inspect each component (I had an ugly surprise of a teflon bushing with the coating just starting to fold over on itself which would have eventually lead to a sticky fork). The first time, this is a good 8 hour job + dry time, since your not sure how things go together, but after that you get quick at it. For a fork seal driver, I recommend a 2" long piece of 2" ABS or PVC pipe, cut lengthwise so you can snap it around the tube

Just some food for thought when your reassembling. Once you've added the oil and are trying to get the air out of the fork, make sure you seal the top of the fork extremely well with your hand as you compress it before putting the caps back on, to get all of the air out. Learned that one the hard way.

 

[Corsara]

Thanks for the help guys. I bought springs from RaceTech before (for my previous bike), and changed them myself, but those were regular forks, not inverted, which kinda seem more complicated to work on. The suggestion about using the ratchet straps is cool, but I'm still not sure if I wanna try and do it myself (mainly when examining the components, I wouldn't know what to look for in terms of damage and wear..).

In all cases, regardless of whether I'll change them myself or have somebody work on them, I'll order a set of springs and some 5W fork oil directly from RaceTech now, only I am not sure what tension springs to get. Their calculator suggests 1.05 kg/mm for my current weight, but they sell 1 kg/mm and 1.10 kg/mm. Maybe I should get the 1 kg/mm since I plan to lose some weight anyway..

 

[smergy]

For me, the honda manual is pretty good at telling you what to for in terms of wear. In this case, one of the parts was clearly starting to wear in correctly. I'm not going to lie, it is a bit of d*cking around the first time, but if your even somewhat mechanically inclined, its not that bad. Get the service manual (if you don't already have it), look over the steps, see what you think.

how much do you weight, how much does your bike weigh and how agressive are you on the track? If your not sure what to get, contact race tech or john sharrard, they will be able to give you solid advice.

 

[Corsara]

I looked at the manual, it seems simple, but then after watching a couple of youtube videos---not so sure anymore.

As for specs, I weight 190 lb without gear, bike is about 430 lb. I don't know how aggressive I am at the track (everybody thinks they're aggressive), but however much it is, I want and plan to be more! We shall see what I'll do. Like it was mentioned in this thread and others, there's some room for improvement before it becomes mandatory to have better than OEM hardware.

 

[YellowDuck]

Thanks for the help guys. I bought springs from RaceTech before (for my previous bike), and changed them myself, but those were regular forks, not inverted, which kinda seem more complicated to work on. The suggestion about using the ratchet straps is cool, but I'm still not sure if I wanna try and do it myself (mainly when examining the components, I wouldn't know what to look for in terms of damage and wear..).

In all cases, regardless of whether I'll change them myself or have somebody work on them, I'll order a set of springs and some 5W fork oil directly from RaceTech now, only I am not sure what tension springs to get. Their calculator suggests 1.05 kg/mm for my current weight, but they sell 1 kg/mm and 1.10 kg/mm. Maybe I should get the 1 kg/mm since I plan to lose some weight anyway..

I don't know what the correct rate is for you, but FYI, when you are between rates there is absolutely no problem putting a 1.0 on one side and a 1.1 on the other. Convention is to put the Lighter spring on the Left.

 

[Corsara]

I don't know what the correct rate is for you, but FYI, when you are between rates there is absolutely no problem putting a 1.0 on one side and a 1.1 on the other. Convention is to put the Lighter spring on the Left.

Interesting! I did not know that, thanks.

 

[Mr.Azim]

I don't know what the correct rate is for you, but FYI, when you are between rates there is absolutely no problem putting a 1.0 on one side and a 1.1 on the other. Convention is to put the Lighter spring on the Left.

Correct. I have a 9.0 and 9.5..... so a 9.25 overall front spring rate.