handling problems
07-30-2005 | 01:58 AM
#1
Thread Starter
Member
Squid
Joined: Mar 2005
Posts: 33
From: beaux arts, wa
handling problems
Hi, I'm still a n00b, still learning to ride, but still alive and with no close-calls. I've got some questions about the handling I should expect.
The bike has 25K miles. I've spent the past few months commuting on it, more figure eights in the parking lot, and short rides in the twisties that somehow keep meandering into long rides. Gone close to 2500 miles. Having a fine time, but I sort of wish it didn't have so much power, seems like I only get to accelerate for brief moments and then I'm going too fast. I'd like a chance to relish reving the motor up, there's just no point reving above 6k, except when I'm particularly angry with the neighbors.
Anyway, the bike is fine for the freeway, stable and comfy, but the front end feels really vague and sort of bendy when I turn more aggresively, especially if the corner has any significant bumps. I've tried jacking up the preload to reduce the sag, but the forks don't seem to like that at all, it gets sort of chattery. The bike seems to handle best with almost 2 lines showing.
The woozy feeling is most pronounced below 45mph where I'm doing most of my tight cornering, and below about 20mph the front wheel feels like it wants to flop way over into the corner, I have to hold it back with my inside hand, which is a little scary sometimes. Also, with some bumps the front wheel feels like its misaligned, like the two stanchions are rebounding at a different rate. I've tried adjusting the rebound separately, but that makes the fork worse. I've also can provoke huge brake dive, which I look at as a measure of how smooth and controlled I can be with the brake and accelerator.
I rode a friends new cbr600rr, it was too small and uncomfortable, that seat and square-edge tank hits me in the wrong way, but I loved the handling. Its rough on the hands on a rough road, but overall its just so gentle and stable and tight in the corners.
My rear tire is a new Pilot Sport, the front is a dunlop 207, with a bunch of wear along both edges like scalloped scrapes. No idea how old it is, the main tred is hardly worn. Anyone with a strong recommendation that I should replace it?
I'm 200# without my riding gear, so I realize that the stock springs are pretty weak for me. I'm hoping with proper springs I can set the front and rear sag to something reasonable and the forks will start behaving.
I've ordered 0.9kg springs to replace the stock ones, but have not ordered gold valves. I intend to swap the springs when they arrive next week.
Does it sound like something is bent?
Should I also replace the fork seals?
Can someone recommend what weight of fork oil to use?
Thanks.
The bike has 25K miles. I've spent the past few months commuting on it, more figure eights in the parking lot, and short rides in the twisties that somehow keep meandering into long rides. Gone close to 2500 miles. Having a fine time, but I sort of wish it didn't have so much power, seems like I only get to accelerate for brief moments and then I'm going too fast. I'd like a chance to relish reving the motor up, there's just no point reving above 6k, except when I'm particularly angry with the neighbors.
Anyway, the bike is fine for the freeway, stable and comfy, but the front end feels really vague and sort of bendy when I turn more aggresively, especially if the corner has any significant bumps. I've tried jacking up the preload to reduce the sag, but the forks don't seem to like that at all, it gets sort of chattery. The bike seems to handle best with almost 2 lines showing.
The woozy feeling is most pronounced below 45mph where I'm doing most of my tight cornering, and below about 20mph the front wheel feels like it wants to flop way over into the corner, I have to hold it back with my inside hand, which is a little scary sometimes. Also, with some bumps the front wheel feels like its misaligned, like the two stanchions are rebounding at a different rate. I've tried adjusting the rebound separately, but that makes the fork worse. I've also can provoke huge brake dive, which I look at as a measure of how smooth and controlled I can be with the brake and accelerator.
I rode a friends new cbr600rr, it was too small and uncomfortable, that seat and square-edge tank hits me in the wrong way, but I loved the handling. Its rough on the hands on a rough road, but overall its just so gentle and stable and tight in the corners.
My rear tire is a new Pilot Sport, the front is a dunlop 207, with a bunch of wear along both edges like scalloped scrapes. No idea how old it is, the main tred is hardly worn. Anyone with a strong recommendation that I should replace it?
I'm 200# without my riding gear, so I realize that the stock springs are pretty weak for me. I'm hoping with proper springs I can set the front and rear sag to something reasonable and the forks will start behaving.
I've ordered 0.9kg springs to replace the stock ones, but have not ordered gold valves. I intend to swap the springs when they arrive next week.
Does it sound like something is bent?
Should I also replace the fork seals?
Can someone recommend what weight of fork oil to use?
Thanks.
07-30-2005 | 08:50 AM
#2
Senior Member
Back Marker
Joined: Dec 2004
Posts: 147
From: Los Angeles, California, Canyons = SMM's, ACH,
It sounds like your on the right track getting the proper weight springs put in.
After you've got the old springe out and before you put the new ones in, slip the front axel into the forks without the wheel on.
The axel should slip in easily and you should be able to turn the axel by hand.
If not adjust the triple clamp till you can.
Then move the forks thru they're travel and check for sticksion.
Springs and Mobil 1 ATF@ 155mm work pretty well.
Without valveing.
I ran like that for a long time before I did the valving.
~Jeffers
After you've got the old springe out and before you put the new ones in, slip the front axel into the forks without the wheel on.
The axel should slip in easily and you should be able to turn the axel by hand.
If not adjust the triple clamp till you can.
Then move the forks thru they're travel and check for sticksion.
Springs and Mobil 1 ATF@ 155mm work pretty well.
Without valveing.
I ran like that for a long time before I did the valving.
~Jeffers
07-30-2005 | 11:58 AM
#3
Senior Member
SuperSport
Joined: Mar 2005
Posts: 758
From: Laurel, MD
Tire or tire pressure. You may have another problem, but I'd bet on one or both of these.
Get the springs. It's the single best mod you can do. Don't get the gold valves unless you can identify a particular improvement (beyond this) that you need to make in the handling.
Get the springs. It's the single best mod you can do. Don't get the gold valves unless you can identify a particular improvement (beyond this) that you need to make in the handling.
08-01-2005 | 02:22 PM
#4
Thread Starter
Member
Squid
Joined: Mar 2005
Posts: 33
From: beaux arts, wa
Re: handling problems
Ok, tires makes sense. I just found this recent thread that has some bad things to say about the dunlop 207 that I have on the front, something about a triangular profile causing it to flop into corners and makes the bike twitchy. Twitchy tire and over soft springs might account for the woozyness I feel today.
https://www.superhawkforum.com/viewtopic.php?t=1242
I'll see how the spring change goes. Then look at replacing the front tire.
https://www.superhawkforum.com/viewtopic.php?t=1242
I'll see how the spring change goes. Then look at replacing the front tire.
08-03-2005 | 06:31 PM
#6
Member
Squid
Joined: Jul 2004
Posts: 48
Re: handling problems
Definitly replace that front tire. As I was reading your post, I was thinking, how old is this guys front tire? Sounds like a front tire prob. Then when I got the bottom where you mention the tires, Aha!
Everyone is always amazed how new tires, espcially the front, can make it feel like a different bike (same with all bikes, not just VTR).
The next step would be the fork springs (which you already ordered, good).
Replace the springs and fork oil (Mobil 1 ATF is good, fully synthetic and very tightly controlled viscosity, which is the big problem normally with using tranny fluid in forks, cheap stuff varies wildly in viscosity, even from one can to the next of same brand). As was mentioned above, fill level to 155 mm from top of fork.
The advice about the axle is good too. You want to make sure the forks are at the same exact height, so there is no binding. Its like 'blueprinting' your fork setup. When you're reassembling, install one fork at the height you want and tighten it down, get the other one close to this height, then install the axle without the wheel. With the 2nd fork only slightly tightened on only the top triple clamp (bottom clamp totally loose), tap the fork up or down slightly until the axle spins freely. You now have the two legs perfect to each other (at the axle, which is where it counts). Tighten them up, install the wheel, go ride...
Everyone is always amazed how new tires, espcially the front, can make it feel like a different bike (same with all bikes, not just VTR).
The next step would be the fork springs (which you already ordered, good).
Replace the springs and fork oil (Mobil 1 ATF is good, fully synthetic and very tightly controlled viscosity, which is the big problem normally with using tranny fluid in forks, cheap stuff varies wildly in viscosity, even from one can to the next of same brand). As was mentioned above, fill level to 155 mm from top of fork.
The advice about the axle is good too. You want to make sure the forks are at the same exact height, so there is no binding. Its like 'blueprinting' your fork setup. When you're reassembling, install one fork at the height you want and tighten it down, get the other one close to this height, then install the axle without the wheel. With the 2nd fork only slightly tightened on only the top triple clamp (bottom clamp totally loose), tap the fork up or down slightly until the axle spins freely. You now have the two legs perfect to each other (at the axle, which is where it counts). Tighten them up, install the wheel, go ride...
08-06-2005 | 04:59 PM
#7
Thread Starter
Member
Squid
Joined: Mar 2005
Posts: 33
From: beaux arts, wa
Re: handling problems
Tire is at 32 pounds in the front, 35 in the back. Too low? Whats a good starting point?
I put the springs in, didn't do anything about the oil yet, I'm still looking for the mobile 1 synthetic.
I cut the spacer so the combined length was the same as before. Preload is the same, rebound is up to 2.5 turns from full out, much more difficult to judge rebound because the forks don't compress 2+ inches from my body weight.
Took it for a quick, careful ride, knowing the forks are too high now.
Wow. Amazing. Before cornering was a very careful 3d balancing act, the bike was so sensitive to throttle that it was all wiggly if I didn't accelerate perfectly. Bike is very controlled now, not so disturbed by bumps. Went through a clover leaf and comfortably leaned deeper than ever before. Very nice! I'm not noticing the forks being wiggly any more. The bike was just so wrong before. Its getting there.
Bike needs more bar pressure to turn because of the raised forks, its sort of like a chopper now.
My hands are a little sore over rough roads now. Fork is not so plush.
Thanks much for the advice. This is really great. How did folks live before the internet?
Here is what is remaining then:
- remove wheel, reset fork heights so axle spins freely
- get mobile 1 atf, set level to 155mm
- install new tire (another pilot sport? yeah...)
I put the springs in, didn't do anything about the oil yet, I'm still looking for the mobile 1 synthetic.
I cut the spacer so the combined length was the same as before. Preload is the same, rebound is up to 2.5 turns from full out, much more difficult to judge rebound because the forks don't compress 2+ inches from my body weight.
Took it for a quick, careful ride, knowing the forks are too high now.
Wow. Amazing. Before cornering was a very careful 3d balancing act, the bike was so sensitive to throttle that it was all wiggly if I didn't accelerate perfectly. Bike is very controlled now, not so disturbed by bumps. Went through a clover leaf and comfortably leaned deeper than ever before. Very nice! I'm not noticing the forks being wiggly any more. The bike was just so wrong before. Its getting there.
Bike needs more bar pressure to turn because of the raised forks, its sort of like a chopper now.
My hands are a little sore over rough roads now. Fork is not so plush.
Thanks much for the advice. This is really great. How did folks live before the internet?
Here is what is remaining then:
- remove wheel, reset fork heights so axle spins freely
- get mobile 1 atf, set level to 155mm
- install new tire (another pilot sport? yeah...)
08-06-2005 | 07:29 PM
#9
Senior Member
MotoGP
Joined: Jan 2005
Posts: 3,844
From: Gainesville FLA.
Re: handling problems
Air pressure is not that bad, when I go to the track I dip into the twenties. If you like the way it feels keep it all though the lower you go the more they wear and you'll have lower gas mileage.
08-07-2005 | 12:05 AM
#10
Thread Starter
Member
Squid
Joined: Mar 2005
Posts: 33
From: beaux arts, wa
Re: handling problems
Oh man. Maybe I should have left it alone. I'm gunna be a serious menace if this gets any easier. Its quite the temptation to pick up the pace. At least before it was a huge challange to ride smoothly, lots of satisfaction while only speeding a little coming out of the hairpins. And you knew right away when you messed up.
Downside was that emergency braking was compromised. Now there is a little dive under hard braking, but I can see the suspension sucking up the bumps.
Bike is now so stable in turns. Its really comfortable. The little bumps are not absorbed, but the big ones are sucked right up so they aren't a distraction.
Downside was that emergency braking was compromised. Now there is a little dive under hard braking, but I can see the suspension sucking up the bumps.
Bike is now so stable in turns. Its really comfortable. The little bumps are not absorbed, but the big ones are sucked right up so they aren't a distraction.
08-08-2005 | 09:47 AM
#12
Thread Starter
Member
Squid
Joined: Mar 2005
Posts: 33
From: beaux arts, wa
Re: handling problems
Thanks, youre totally right. Keep reminding me. I'm finding myself with quite a bit more control than I'm used to, I think I miss all that thrilling "feedback".
The available grip is really astounding. I'd no idea this spring change could have such a dramatic effect.
Changed the fork oil yesterday, the old oil was at 150mm, was totally opaque and dark grey, and appeared thicker than the new mobile 1 (7w?). Does that match any new fork oil? Or was the stuff just super old?
I'm not noticing much of a difference with the new oil, but probably because the bike feels so totally different from before.
I haven't raised the forks yet, I'm not sure how much and am worried about steeping the effective head angle. I'll more carefully measure the sag and stiction I'm seeing, then ask how much I should raise the forks.
I wish I'd measured the old heights.
The available grip is really astounding. I'd no idea this spring change could have such a dramatic effect.
Changed the fork oil yesterday, the old oil was at 150mm, was totally opaque and dark grey, and appeared thicker than the new mobile 1 (7w?). Does that match any new fork oil? Or was the stuff just super old?
I'm not noticing much of a difference with the new oil, but probably because the bike feels so totally different from before.
I haven't raised the forks yet, I'm not sure how much and am worried about steeping the effective head angle. I'll more carefully measure the sag and stiction I'm seeing, then ask how much I should raise the forks.
I wish I'd measured the old heights.
02-07-2006 | 11:47 PM
#13
Thread Starter
Member
Squid
Joined: Mar 2005
Posts: 33
From: beaux arts, wa
Re: handling problems
Resurrecting this thread to keep the info in one place.
I just had the front tire replaced with a pilot power. The mechanic was like: "Whew! That front tire is toast! Somebody melted it at a trackday."
I don't know what my other bike-riding friends were thinking. Anyway, I've now got a Pilot Power on the front and the bike is wonderful, plush, the front tire now feels like its got a round profile and nothing wierd happens in the front when I lean it over.
Braking is really good, the limits are quite a bit higher than the dunlop which would start to skip and chatter without making much noise. The new tire is very mellow and competent and grips really well.
Probably the springs made a bigger difference than the tire, the bike was tough to ride with the forks diving, the tire is like sugar on top.
Thanks all for the help.
I just had the front tire replaced with a pilot power. The mechanic was like: "Whew! That front tire is toast! Somebody melted it at a trackday."
I don't know what my other bike-riding friends were thinking. Anyway, I've now got a Pilot Power on the front and the bike is wonderful, plush, the front tire now feels like its got a round profile and nothing wierd happens in the front when I lean it over.
Braking is really good, the limits are quite a bit higher than the dunlop which would start to skip and chatter without making much noise. The new tire is very mellow and competent and grips really well.
Probably the springs made a bigger difference than the tire, the bike was tough to ride with the forks diving, the tire is like sugar on top.
Thanks all for the help.
02-08-2006 | 09:06 AM
#14
Senior Member
SuperBike
Joined: Dec 2005
Posts: 1,689
From: South Lake Tahoe, CA, USA
Sounds like you're making good progress. I don't see any mention of setting front end sag. The lines on the adjuster are really irrelevant, excepta as a comparative reference. You changed the springs, so the preload height adjustment from before is not valid. And at 200# you had excessive sag even with the adjusters all the way in with the stock springs.
I'm going off the top of my head here, because I don't have the numbers in front of me. But I believe the spring preload should be set so the bike sags 25-28mm below full extension with you on the bike, suited up.
Be careful out there!
I'm going off the top of my head here, because I don't have the numbers in front of me. But I believe the spring preload should be set so the bike sags 25-28mm below full extension with you on the bike, suited up.
Be careful out there!
02-08-2006 | 09:30 AM
#15
Thread Starter
Member
Squid
Joined: Mar 2005
Posts: 33
From: beaux arts, wa
Re: handling problems
Right, I should have mentioned that. I reset the sag to 25mm when I installed the springs. The new springs are waaay stiffer than the old. Before the preload was almost all the way in and had too much dive, now the posts stick way out. With the preload back where it was the forks would probably not move when I sat on the bike.
For rebound, I set it so it wouldn't bounce on rebound, but after riding a while I loosened it a tiny bit more.
I also followed Oppenheimer's "blueprinting" advice.
With the new front tire the bike feels really nice. I am thinking of raising the fork tubes a little bit, but I'll wait until I am used to these new tires. I've had the new springs for almost six months and I don't think I like the raised front chopper feeling that they gave me. I understand that a small change goes a long way.
On my last few rides I am more aware than ever of the rear suspension working, it seems kind of uncontrolled compared to the front. The front feels so planted.
For rebound, I set it so it wouldn't bounce on rebound, but after riding a while I loosened it a tiny bit more.
I also followed Oppenheimer's "blueprinting" advice.
With the new front tire the bike feels really nice. I am thinking of raising the fork tubes a little bit, but I'll wait until I am used to these new tires. I've had the new springs for almost six months and I don't think I like the raised front chopper feeling that they gave me. I understand that a small change goes a long way.
On my last few rides I am more aware than ever of the rear suspension working, it seems kind of uncontrolled compared to the front. The front feels so planted.
02-08-2006 | 11:12 AM
#16
Senior Member
SuperBike
Joined: Dec 2005
Posts: 1,689
From: South Lake Tahoe, CA, USA
The "preload' adjustment doesn't change the amount of compression in the spring. The spring has a "rate" measured in kgs/mm. So if you are sitting on the bike and the suspension sags 25mm. If you screw the adjuster in 5mm, the sag will then be 20mm.
The length of the spring hasn't changed, you've only raised the height the bike sits at with that amount of weight on it. The weight of the front end is sitting on the springs through the preload adjuster.
It is a common misconception that preload changes the amount of spring compression or suspension stiffness.
The length of the spring hasn't changed, you've only raised the height the bike sits at with that amount of weight on it. The weight of the front end is sitting on the springs through the preload adjuster.
It is a common misconception that preload changes the amount of spring compression or suspension stiffness.
02-08-2006 | 03:43 PM
#17
Slacker
Superstock
Superstock
Joined: Jun 2005
Posts: 489
From: San Antonio, TX
Re: handling problems
In response to your idea or raising the forks in order to compensate for the stiffer springs, instead you might want to think about going the route of installing a spacer above the rear shock (if your legs are long enough).
This will take away that "chopper like feeling" without sacrificing ground clearance. OR, if you have enough pesos, you might wanna spring for an aftermarket rear shock with adjustable ride height, to complement your new fork springs.
This will take away that "chopper like feeling" without sacrificing ground clearance. OR, if you have enough pesos, you might wanna spring for an aftermarket rear shock with adjustable ride height, to complement your new fork springs.
02-08-2006 | 04:01 PM
#18
Senior Member
SuperSport
Joined: Mar 2005
Posts: 758
From: Laurel, MD
The "preload' adjustment doesn't change the amount of compression in the spring. The spring has a "rate" measured in kgs/mm. So if you are sitting on the bike and the suspension sags 25mm. If you screw the adjuster in 5mm, the sag will then be 20mm.
The length of the spring hasn't changed, you've only raised the height the bike sits at with that amount of weight on it. The weight of the front end is sitting on the springs through the preload adjuster.
It is a common misconception that preload changes the amount of spring compression or suspension stiffness.
The length of the spring hasn't changed, you've only raised the height the bike sits at with that amount of weight on it. The weight of the front end is sitting on the springs through the preload adjuster.
It is a common misconception that preload changes the amount of spring compression or suspension stiffness.
02-08-2006 | 04:08 PM
#19
Senior Member
SuperBike
Joined: Dec 2005
Posts: 1,689
From: South Lake Tahoe, CA, USA
You have the same load on the spring. How can you compress it further without topping out on the suspension? You simply push the bike further up in the suspension travel. That's the common misconception I'm referring to.
02-08-2006 | 04:22 PM
#20
Member
Squid
Joined: Jan 2006
Posts: 93
From: Tucson
Re: handling problems
I didn't see anybody point to the fact that you had two different models and manufacturer's tires on the front and the rear. According to the tire manufacturers you are supposed to run the same model tire on the front and the rear. Mixing them up is a no no.
02-09-2006 | 08:51 AM
#22
Senior Member
SuperBike
Joined: Dec 2005
Posts: 1,689
From: South Lake Tahoe, CA, USA
Just to make sure my explanation is clear, for those of you interested:
The weight of the bike and rider are suspended on top of the springs. This is the static load on the suspension. This load causes a fixed deflection of the springs. The fact that there is static sag says that it is this static load that is determining the length of the springs.
If the suspension did not sag with the weight of the bike and rider, and the suspension were topped out, then increasing "preload" would shorten the springs. But again since it is sagging the static load must determine the spring length.
Therefore, changing the "preload" does not change the load on the springs and load on the springs is the only determining factor for the loaded length of a given spring.
If preload were able to change the spring length, which it could only do if it were attached below the spring and pulling down on the top, then increasing preload would shorten the spring and the bike would sit lower.
"Preload" can only set where the bike sits in the suspension travel for a given load. It can't change the load on the springs.
If you still are not convinced, try changing the preload adjustment on your rear shock and compare spring length before and after the adjustment.
The weight of the bike and rider are suspended on top of the springs. This is the static load on the suspension. This load causes a fixed deflection of the springs. The fact that there is static sag says that it is this static load that is determining the length of the springs.
If the suspension did not sag with the weight of the bike and rider, and the suspension were topped out, then increasing "preload" would shorten the springs. But again since it is sagging the static load must determine the spring length.
Therefore, changing the "preload" does not change the load on the springs and load on the springs is the only determining factor for the loaded length of a given spring.
If preload were able to change the spring length, which it could only do if it were attached below the spring and pulling down on the top, then increasing preload would shorten the spring and the bike would sit lower.
"Preload" can only set where the bike sits in the suspension travel for a given load. It can't change the load on the springs.
If you still are not convinced, try changing the preload adjustment on your rear shock and compare spring length before and after the adjustment.
02-09-2006 | 10:17 AM
#23
Senior Member
SuperSport
Joined: Nov 2005
Posts: 547
You are right RCVTR,
Preload adjusters do not change the spring length at all. In fact, they are labeled S (soft) and H (hard) because all they adjust is the rigidity of the bike under load. I'm not familiar with the internals of VTR forks, but the preload adjuster makes the active portion (overall effective length) of the fork tube longer or shorter. This changes the effect of the gas/air in the fork tube, to make the travel of the suspension happen faster (Soft) or slower (Hard).
Changing the spring length really wouldn't be very helpful, even with progressive springs, as you would be prone to bottoming out your springs, and that's unsafe (not to mention painful). Like hitting a speedbump except it feels like you ran over a curb!
Preload adjusters do not change the spring length at all. In fact, they are labeled S (soft) and H (hard) because all they adjust is the rigidity of the bike under load. I'm not familiar with the internals of VTR forks, but the preload adjuster makes the active portion (overall effective length) of the fork tube longer or shorter. This changes the effect of the gas/air in the fork tube, to make the travel of the suspension happen faster (Soft) or slower (Hard).
Changing the spring length really wouldn't be very helpful, even with progressive springs, as you would be prone to bottoming out your springs, and that's unsafe (not to mention painful). Like hitting a speedbump except it feels like you ran over a curb!
02-09-2006 | 10:36 AM
#24
Senior Member
SuperSport
Joined: Sep 2005
Posts: 882
From: Dallas, TX
Re: handling problems
The advice about the axle is good too. You want to make sure the forks are at the same exact height, so there is no binding. Its like 'blueprinting' your fork setup. When you're reassembling, install one fork at the height you want and tighten it down, get the other one close to this height, then install the axle without the wheel. With the 2nd fork only slightly tightened on only the top triple clamp (bottom clamp totally loose), tap the fork up or down slightly until the axle spins freely. You now have the two legs perfect to each other (at the axle, which is where it counts). Tighten them up, install the wheel, go ride...
I need to readjust mine after working on the forks
02-09-2006 | 05:28 PM
#25
Senior Member
SuperBike
Joined: Dec 2005
Posts: 1,689
From: South Lake Tahoe, CA, USA
Loco, you made a good point about the function of the air in the top of the fork. The compression of the air as the fork compresses has a large effect on the progressive stiffness of the front end.
It's what makes the oil level critical, and allows an additional tuning parameter for the front end.
It's what makes the oil level critical, and allows an additional tuning parameter for the front end.
02-09-2006 | 08:35 PM
#26
Senior Member
SuperSport
Joined: Mar 2005
Posts: 758
From: Laurel, MD
Just to make sure my explanation is clear, for those of you interested:
The weight of the bike and rider are suspended on top of the springs. This is the static load on the suspension. This load causes a fixed deflection of the springs. The fact that there is static sag says that it is this static load that is determining the length of the springs.
If the suspension did not sag with the weight of the bike and rider, and the suspension were topped out, then increasing "preload" would shorten the springs. But again since it is sagging the static load must determine the spring length.
Therefore, changing the "preload" does not change the load on the springs and load on the springs is the only determining factor for the loaded length of a given spring.
If preload were able to change the spring length, which it could only do if it were attached below the spring and pulling down on the top, then increasing preload would shorten the spring and the bike would sit lower.
"Preload" can only set where the bike sits in the suspension travel for a given load. It can't change the load on the springs.
If you still are not convinced, try changing the preload adjustment on your rear shock and compare spring length before and after the adjustment.
The weight of the bike and rider are suspended on top of the springs. This is the static load on the suspension. This load causes a fixed deflection of the springs. The fact that there is static sag says that it is this static load that is determining the length of the springs.
If the suspension did not sag with the weight of the bike and rider, and the suspension were topped out, then increasing "preload" would shorten the springs. But again since it is sagging the static load must determine the spring length.
Therefore, changing the "preload" does not change the load on the springs and load on the springs is the only determining factor for the loaded length of a given spring.
If preload were able to change the spring length, which it could only do if it were attached below the spring and pulling down on the top, then increasing preload would shorten the spring and the bike would sit lower.
"Preload" can only set where the bike sits in the suspension travel for a given load. It can't change the load on the springs.
If you still are not convinced, try changing the preload adjustment on your rear shock and compare spring length before and after the adjustment.
02-10-2006 | 01:20 AM
#27
Senior Member
Superstock
Joined: Jan 2006
Posts: 402
From: Florida
You are right RCVTR,
Preload adjusters do not change the spring length at all. In fact, they are labeled S (soft) and H (hard) because all they adjust is the rigidity of the bike under load. I'm not familiar with the internals of VTR forks, but the preload adjuster makes the active portion (overall effective length) of the fork tube longer or shorter. This changes the effect of the gas/air in the fork tube, to make the travel of the suspension happen faster (Soft) or slower (Hard).
Changing the spring length really wouldn't be very helpful, even with progressive springs, as you would be prone to bottoming out your springs, and that's unsafe (not to mention painful). Like hitting a speedbump except it feels like you ran over a curb!
Preload adjusters do not change the spring length at all. In fact, they are labeled S (soft) and H (hard) because all they adjust is the rigidity of the bike under load. I'm not familiar with the internals of VTR forks, but the preload adjuster makes the active portion (overall effective length) of the fork tube longer or shorter. This changes the effect of the gas/air in the fork tube, to make the travel of the suspension happen faster (Soft) or slower (Hard).
Changing the spring length really wouldn't be very helpful, even with progressive springs, as you would be prone to bottoming out your springs, and that's unsafe (not to mention painful). Like hitting a speedbump except it feels like you ran over a curb!
The S and H settings on top of the forks are in relation to the rebound damping not preload on the springs. It only reflects how fast the suspension will return to its normal state after being compressed, after say, going over a bump.
The preload spacer inside the forks is cut to a predetermined length based on your weight and riding style to bring into range, the ability of the preload adjustments on the fork caps to adjust you sag (I think).
When you turn your preload adjusters in (less lines showing) you are compressing the springs. There is a slight rising affect to the front end as a side affect. Compressing the spring removes some of the springs overall working range. This appears to make the spring a bit "stiffer" however it is just removing some of the "springiness" by PRE-loading it prior to the addition of forces exerted by the road topology. Progressive springs appear to be a throw back to the late 70s and 80s since a properly chosen constant rate spring would give consistent and accurate suspension compression throughout the range of travel. In a perfect world there would be a spring cut for each model bike and rider weight, and there would be no need to have a preload spacer in the fork. The motorcycle would then sit atop the springs and not the spacers over the springs. The preload adjuster would then make the slight adjustments needed for the rider's weight changes and spring aging.
The fork oil wt is being used to assist in damping the suspension movement. Lighter wt less damping, heavier wt fork oil = more damping. Out stock fluid is 8wt.
Air being a heck of a good spring adds, as Jim said, another area of adjustment.
By increasing the fork oil level as I did in forks from our standard 130mm to 120mm, I reduce the amount of compressible air and add a bit more stiffness to the travel since there is less air to squish and more oil (friction) to push against.
When the little holes at the bottom of the cartridge have more oil to push than the holes will allow you may experience a hydraulic lock or increasingly severe harshness. This is not related to the springs or preload or rebound. It is only related to compression damping and on our SH forks that is fixed via the washer/shim stack Honda installed.
To correct compression damping you can;
A. Drill the cartridge holes bigger, and I am not safe with power tools. Then reconfigure the washer/shim stack.
B. Buy new compression valves from some one like Racetech and use their washers/shims/experience to change the damping curve to one that is more progressive and can accommodated the larger amount of fork oil fluid being forced through under fast and heavy suspension compression such as going over a square edged bump at speed.
This is not a perfect explanation but I hope it helps.
Now I will duck behind the counter to avoid the rotten tomatoes I know will be coming my way.
02-10-2006 | 09:11 AM
#29
Senior Member
SuperBike
Joined: Dec 2005
Posts: 1,689
From: South Lake Tahoe, CA, USA
The S and H settings on top of the forks are in relation to the rebound damping not preload on the springs. It only reflects how fast the suspension will return to its normal state after being compressed, after say, going over a bump.
The preload spacer inside the forks is cut to a predetermined length based on your weight and riding style to bring into range, the ability of the preload adjustments on the fork caps to adjust you sag (I think).
When you turn your preload adjusters in (less lines showing) you are compressing the springs. There is a slight rising affect to the front end as a side affect. Compressing the spring removes some of the springs overall working range. This appears to make the spring a bit "stiffer" however it is just removing some of the "springiness" by PRE-loading it prior to the addition of forces exerted by the road topology.
Tuning the attitude of the bike is done with rear ride height and location of the forks in the triple clamps.
I wouldn't change the porting on the damping valves. They are tuned for high speed damping after the shim stack has opened and is no longer effective. Oil weight and tuning the shim stack are the way to control the low-midspeed damping in conjunction with the needle-orifice damping that the screw adjusment provides. Oil weight affects the damping throughtout the entire range of suspension velocities.
02-10-2006 | 11:55 AM
#30
Senior Member
SuperSport
Joined: Nov 2005
Posts: 547
Re: handling problems
"When thinking about preload, you should remember that adjusting preload up of down simply changes the height at which the bike rides. It does not make suspension stiffer or softer. The reason many riders intuitively feel that preload changes adjust stiffness is that a bike with a lot of preload doesn't move as easily when you sit down on it. It takes more pressure to begin to compress the suspension. This is not the same as a stiffer spring! A stiffer spring is made with either thicker wire (a few .001 in wire diameter makes a big difference) or fewer coils."
--Sportbike Performance Handbook, by Kevin Cameron
--Sportbike Performance Handbook, by Kevin Cameron
