|   Should I change to heavier oil or heavier springs? | cheetos316
Feb 23, 2002 7:16 AM | | My Z1 is too soft for my taste. It bottomed out on a 3 footer!!! I'm thinking that I should get a heavier spring but the mechanic at the shop told me to just get a heavier oil. What difference is there with going with the heavier oil rather than the spring? Would it be possible to run a soft spring in one leg and a heavy spring in the other leg? Also, which should be cheaper?
Thanks |
| First, get a new mechanic | NCN
Feb 23, 2002 7:40 AM | | There are three things you can try. A heavier spring will take more energy to bottom out overall. Heavier oil will give you more compression damping, making your Z1 less responsive to small hits and possibly curing any problems you're having with bobbing. You probably won't notice much difference with the heavier oil on the big type of hits that made you bottom out. Adding some additional oil (raising the height about 5 mm) will make your Z1's spring rate ramp up more rapidly at the end of the travel; that's what I'd try first. And any "mechanic" who knows Marzocchis should know that, which is why you probably don't want to listen to the fellow you spoke to at the shop.
You can check out recommended settings for your fork and weight at Marzocchi's web site. Also, no problem running different springs in each leg.
Good luck!
NCN |
| agreed | sledneck
Feb 24, 2002 5:58 AM | | that's a good order -spring change, new sag adjustment, check your oil weights, check your oil heights. I don't know about 5mm increments though, you can tell the diff between 1mm changes, you either bottom out or you don't. |
| DO NOT use a soft and a firm spring, it's okay to... | Squash
Feb 23, 2002 12:05 PM | | use a soft/medium combination or a medium/firm combination, but a soft/firm is too much variance between the two legs. First thing to check is your oil level like NCN stated. I'd also try and find a new mechanic. The dope doesn't know what he's talking about. The only time you should go to heavier oil is if you need more damping performance. Heavier oil will have little effect on how easily the fork bottoms out. It would be easier to make a specific recommendation if we knew how much you weighed. The only thing that I can tell you right now is to check the oil level according to the manual. If it's too low or at the lower setting then add more oil up to the maximum recommended. If the fork still bottoms too easily then get the heavier springs. Just don't go more than one level above your current springs if you plan on mixing rates between legs.
Good Dirt |
| I will take a chance and disagree with squash | Gary
Feb 23, 2002 3:24 PM | | I have made a mistake and disagreed with squash before, and received the brunt of his " I am never wrong analysis", but here goes anyway; increasing your oil viscosity (weight) will keep you from bottoming out so quickly. The bike shop mechanic wasn't a "dope" for suggesting this. Forcing heavier oil thru a fixed orifice will slow down the rate of compression. Hence, you may not bottom out as easily. The springs work in concert with the oil. If the spring weight is correct and not too soft, the oil viscosity will make a big difference. Squash, I am all yours. |
| unless you've got position sensitive compression damping | Jm
Feb 23, 2002 5:23 PM | | raising the oil level in the compression leg is not the way to keep a fork from bottoming.
3 things keep forks from bottoming
Position sensitive compression damping(rare, only on a few high end DH forks)
Heavy enough springs/Progressive springs
Air-spring, caused by oil height(marzocchi forks).
Trying to keep the fork from bottoming any other way is not going to result in a plush/consistant feeling fork. |
| No way. | Dougal
Feb 24, 2002 5:05 PM | | Position sensitive damping has nothing to do with bottomout, unless you're talking about anti bottoming cones which use hydraulic lock to stop the clank.
Compression damping across the range of stroke sucks a whole lot of energy out of the impact and slows the fork enough to stop the impact. The damping handles most of the energy, the springs take bugger all.
Raising the oil height can be a fast way to overstress a fork and seals.
ROckshox is a prime culprit of a company with the progressive philosophy, using the spring curve instead of the damper to suck up big hits.
The result is a harsh fork with not much midstroke and inconsistent rebound across the stroke. Basically a fork that isn't consistent or plush. Ride a Psylo and you'll see what I mean.
Dougal.8m.com |
| heh, how ironic | Jm
Feb 24, 2002 6:00 PM | | you claim that rockshox is the main culprit of the progressive-philosophy is kinda funny, considering that manitou has used OVERLY progressive spring stacks with elastomers mixed in for such a long time, and that they use rubber or some other kind of rubberized plastic at the bottom to keep them from bottoming out! Manitou is the one that can't keep their forks from bottoming without some sort of progressive spring stack!
And yes i know what you mean about the pyslo, but it felt better than the Black. |
| heh, how ironic | Dougal
Feb 24, 2002 9:37 PM | | Take a look inside a current Psylo or Judy. The spring stacks in the psylos are straight from the RST parts bin, an elastomer core inside the coil spring.
Makes for a really bouncy feeling fork and rebound way faster near the bottom of the stroke than it should be.
The stock manitou stacks are progressive but not to the point of the current RS crop. My DC came stock needing 40mm of compression from about 6 inches of MCU (the other 80mm of compression come from the coilspring), pretty much linear while riding. I think the three stage stack I've got there at the moment is more progressive than it was originally.
Back in 97 the manitous were very progressive (most people couldn't get full travel) and had a good lump of compression damping to boot. They've been backing off ever since, now the Blacks have linear springs.
The 01 judy XC was probably the worst example, starts feeling like a ballpoint pen spring in there then 40mm later it'd hold up a corner of my range rover.
Dougal.8m.com |
| yes they are better now, in fact | Jm
Feb 25, 2002 9:15 AM | | old Judys actually had ajustable compression damping, not rebound, so they have done like a 180 almost.
Compression is important, but on nearly every fork ive tried that had the feature, increasing the damping made it much more harsh. |
| Your not wrong, but without his weight it's not... | Squash
Feb 23, 2002 9:12 PM | | possible to answer whether or not he should go to heavier oil. The reason I recommended against it is that 90% of Zocch bottoming problems are related to oil level or spring rate. The very last thing that you try with a Zocch is an increase in oil weight. Going to heavier oil can lead to a bad case of compression spike, even if the compression damping is adjustable. So you tell me if his Wrench knows what he's talking about when it comes to Marzocchi's. That's besides, you're post was just begging for a reply. So show me where I'm wrong here please.
Good Dirt |
| yes you're right (but so is Squash) | Dougal
Feb 24, 2002 4:52 PM | | Thicker oil will give you more compression damping and can stop a bottomout problem.
The problem here is lack of information about the rider. If he already has say 20-25% sag and bottoms out it could be due to not enough oil or not enough damping.
If the rider had say 1/3 sag then it's definately the springs that need attention but overall in an impact the springs account for bugger all of the energy, the damper handles most of it and compression damping is far more critical than most people (and most companies thanks Rockshox) give it credit.
Dougal.8m.com |
| I agree with squash on several points | Jm
Feb 23, 2002 5:32 PM | | First, altering oil weight usually has little effect on bottom out. The one fork that it does make a difference(and I have ridden dozens upon dozens of different models) is a Boxxer, it has a sort of progressive damping, where the oil ports are aranged vertically so with more stroke, you get more damping, it also has a bottom-out cone type damper, which makes the last .5" heavily damped, another kind of position-damping.
However, this is not indicitive of any XC forks or most other forks.
In 99% of forks, increasing the oil weight will not help keep it from bottoming, OR if it does(by restricting the flow) it will make the fork feel very harsh and pack up all the time. You do not want this because the fork won't be doing what it is designed to do, which is absorb bumps.
Another point, by using very different spring lengths in each leg you put different forces on each of the cartridges. One of marzocchis claims to fame is that they run dual dampers and coil springs in each leg, to provide roughly the same force on each damper, for consistancy. This doesn't mean that running very different spring rates can't work(like Manitous that use one spring in one leg), however; marzocchi claims that their system is optimal and provides the best preformance. For this reason, it's best if you are going to use different springs in each leg, then use only the next size up or down, not two sizes.
Lastly, if you are getting correct sag on the Z1(the most important part of tuning spring weight) then you need higher oil height to keep it from bottoming, this is usually why Marzocchis bottom, because the user has not added enough oil to keep it from bottoming for their ride style. Consult the owners manual, or call marzocchi to ask what is the max oil that you can put in it. It makes a big difference. |
| I agree with squash on several points | Gary
Feb 23, 2002 5:49 PM | | I would agree with you that the fork will feel harsh with heavier oil. I was just addressing question of stopping bottoming out problem. Of course, if you use a heavier spring, you don't think it will be a harsher ride? With a heavy spring, how do you get proper sag? I ran progressive springs in my motorcycle and they were supposed to stop bottoming out on big bumps. Worked marginally. Newton's Law (I think), once a body is in motion, it tends to stay in motion. I had to go to heavier oil on the motorcycle, with the resultant trade-off in small bump compliance. Am I wrong? |
| it is all about tuning for his weight | Jm
Feb 23, 2002 6:16 PM | | For one Marzocchi forks can't be tuned like a boxxer, with a compression side and rebound side, so you can't tune one without affecting the other, at least somewhat. Now the boxxer is a bit of a b*tch to set up, and doesn't have as much "range" as other forks, but enough about that;
If you are riding with proper sag on a marzocchi, and you are still bottoming it, then you need more oil volume, which makes it progressive because of the air spring on top. Marzocchis are designed to run this way. Heavier oil is used to control rebound, and for heavier riders, you obviously need heavier oil, however it is not commonly used to keep the fork from bottoming, but the opposite, to keep it from extending too fast.
On other forks, if you are running the correct amount of sag, and you are still bottoming, most likely you need heavier springs, you might loose out on some of the plusher initial travel, BUT it is still going to be a supple smoooth ride. If you increased the oil weight, to slow down compression, then the fork would become harsh. It would not react well to small hits, and it would "spike" on larger ones, where it would not compress fast enough to absorb the hit.
This is how most current Mountain Bike technology works. Hopefully in the future by turning up compression damping we could controll progressiveness to some extent as well, but with current technology from most manufacturers, when you increase compression damping you make the fork more harsh, because it operates over the entire range of travel. |
| No your not wrong, for motorcycle forks..(nm) | Squash
Feb 23, 2002 9:03 PM | | . |
| wtf? | sledneck
Feb 24, 2002 5:51 AM | | What does that mean? Where do you think mtb forks came from, specifically, the marz ones you are debating? Of course he's right. Unfortunately we don't live in a marz-perfect world where despite only having the one spring to work with, we all fit into the centre of the spring rate categories with no shades of grey, and not have to compromise any other aspects of tuning to get the ride we like because of it. But it does work for most. |
| Simply this, while bike forks are based loosely on... | Squash
Feb 24, 2002 7:18 AM | | motor cycle forks. Moto forks are designed for heavier, faster, powered vehicles. They are also more technilogically advanced, just pull apart a bike fork and a moto fork side by side. There's quite a difference there. It's about like comparing automobile shocks to bike forks. While they all work on the same principles, they react differently to the same conditions. It's like comparing coil springs to leaf springs. They do the same job just diffently. What works for one doesn't always hold for the other.
Good Dirt |
| it is simply this; | Jm
Feb 24, 2002 9:23 AM | | most mx forks have speed sensitive damping AND position sensitive damping, so they can easily be tuned not to bottom, but;
mountain bike forks do not have position sensitive damping. So if you try and keep a mountain bike from bottoming by using heavier compression oil, it will affect the entire compression stroke, which means it will take more force to even get the fork moving, and it will be much harsher. Since mountain bike forks lack the technology of mx forks, they can't be tuned to do the same things. Marzocchi knows this and uses a clever way to control compression, their "air-spring". |
| What is this much harsher? | Gary
Feb 24, 2002 2:17 PM | | I can understand what you are saying. But you keep saying fork will be "much harsher" with heavier oil. Come on now, if you have to go from 5wt. to 7.5wt. or 7.5wt. to 10wt., which is all it might take to keep fork from bottoming, it isn't going to be much "harsher". You make it sound like it would be unrideable. I am sure from your experience, you have ridden an oversprung and under damped fork. It isn't a lot of fun. Perhaps from original question, he had correct spring and oil was way to light. Couldn't that be the case? |
| the point your missing is... | zedro
Feb 24, 2002 2:45 PM | | the first thing to do is to increase the oil height. Nothing was mentionned about the damping characteristics, so it goes to the bottom of the list.
I've owned both a z1 and JrT with the same damper units (although i modified the JrTs valve shim). Oil height is everything on these forks. If that doesnt work, then you can increase the weight of the oil although it may not do the trick (and theres no point going beyond 10wt for a medium/heavy spring setup). Ideally you'd want to increase one spring weight first, then change your damping accordingly.
Its a matter of tuning your fork properly, over just trying to prevent bottom out (or else why not fill it with grease?) |
| it is simply this; | sledneck
Feb 24, 2002 3:57 PM | | Yep, that's it alright. I'm usually the first to say that compression damping is not a band aid solution for bottom out, and maybe I should have said that right from the beginning. From your example I couldn't argue it any other way, but I was trying to say that it does have a place in mtb, admittedly a very small place, for a couple of reasons. Brake dive, track conditions (f/end feedback and personal preference) and position sensitive damping(tpc+).
BTW I was actually referring to roadbike motorcycle forks, not mx (don't ask why) where compression damping is crucial, but as Squash said, for entirely different reasons.
Personally Jm, I think you just summed up why most people get annoyed at the design limitations to the performance of their forks, and why Manitou developed tpc+. |
| well there is so much more too it as well | Jm
Feb 24, 2002 4:57 PM | | the TPC+ is a step in the right direction, but it works on the first part of the stroke and then stiffens up, rather than stiffening up the end-stroke, but it is definatly a step in the right direction.
Marzocchis air spring idea is a good solution I think as well.
Foes new F1-XL Curnutt fork should have some kind of position sensitive damping as well.
One important thing though, heavier oil IS used for heavier rides, but not to tune compression, that was one thing that was a key point, heavier oil IS good for heavier riders, its just that most forks do not feel much different, if at all, with heavier oil, in COMPRESSION, because most forks do not have any real kind of compression cartridge.
Anyhow, like I said, there is much more to this whole fork-design thing, hopefully companies are moving in the right direction. |
| well there is so much more too it as well | Gary
Feb 24, 2002 5:13 PM | | My responses were based on my X-vert Super with TPC where heavier oil did make a difference because I have compression damping. So, are we in agreement that heavier oil will make a difference if you have a fork with adjustable compression damping. Otherwise, I guess I am still confused (my natural state). |
| Not it's not. | Dougal
Feb 24, 2002 5:12 PM | | Compression damping is crucial to not only the feel but providing chassis control, preventing bottomout, maximising traction AND keeping the tire in contact.
This is on all vehicles from radio controlled cars on and up.
Try riding a fork or rear shock with the compression damper disabled sometime, it really really sucks badly.
The ride wallows and wobbles, relies heavily on the bottomout bumpers, blows through it's travel and is alarmingly unstable, especially when you get up in the travel.
Manitous Black and FOX's vanilla forks are the way it should be, a close to linear spring curve with the damper controlling the entire stroke.
Manitous TPC+ is a feel orientated upgrade, it does nothing for performance but it does enhance the feel of the fork on very small impacts. I've run my fork with and without TPC+, the difference is only noticable at low to medium speeds and it is minor.
Compression damping is not a band aid solution, it is the best and only real solution.
Dougal.8m.com |
| Jeez, you mean I was right?-nm | Gary
Feb 24, 2002 5:16 PM | | |
| I don't know what shocks dougal has ridden, but | Jm
Feb 24, 2002 5:55 PM | | nearly every one that I have owned and used got more harsh if the compression damping was increased, through oil weight or increasing the damper setting. The only ones that I have that would resist bottoming or not get overly harsh were my boxxer, that is it. Using countless other rockshoxs, manitous, marzocchis and others, they all get more harsh with more compression damping.
Heavier oil helps control the rebound better for heavier riders, most times it doesn't affect compression damping, and if it does, it usually makes it harsher with 95% of forks. |
| That's because RS doesn't have a decent damper. | Dougal
Feb 24, 2002 9:43 PM | | Up until recently RS hasn't had a decent fork damper.
The boxxer and every other hydracoil fork are modified orifice dampers. Simply take the cheapest and crustiest oil damper from a motorbike fork and add a blowoff spring in there.
It's only the pure damper in the psylo SL's which has potential but I haven't been able to ride or wrench one yet to judge.
The dampers RS has used up to now have very little low speed damping (lets the fork float and wallow over smooth undulations) and lots of high speed damping (harsh and spiking over bumps and impacts).
The shim stacked dampers which manitou and now FOX (and the cartridge equipped marzocchis) are using (and every decent rear shock uses) can achieve a linear damping rate across the speed range, they can control the low speed movements without being harsh over impacts and can be tuned for more or less damping almost anywhere in the impact speed range to remove any harshness.
Dougal.8m.com |
| hold on a second | Jm
Feb 25, 2002 9:30 AM | | you are saying that the boxxer damper is just the same as a hydracoil? No way, now the low-speed rebound and low speed compression are orofices if i remember correctly, but apart from that it has seperate high speed rebound and compression circuts, that can be be tuned independantly.
A boxxer cartridge is about as close to a hydracoil damped judy or psylo as a Manitou is to a Marzocchi, there is no comparision and the Boxxer cartridge actually visually looks like a marzocchi cartridge, although the boxxer compression leg has oil ports going vertically down the leg for a short distance, from big up top, to small as you get further down. There is also damping internal to the cartridges(high speed) that you can't get at without further breaking the cartridges down.
There may be similer princibles in the hydracoil forks, but the boxxer is many times more complex with seperate circuts and ajustments for different aspects of tuning. The real downfall is that it doesn't have a bigger range of ajustment. |
| Not it's not. | sledneck
Feb 24, 2002 6:41 PM | | I don't know how you took "feel" to mean, I intended it to be general, but it encompasses all of what you said - control. It's not universal, it's a personal thing. Plushness, tyre feedback, wheel response and a sqillion other non-quantifiable aspects of suspension and and preferences all vary from one rider to another as much as tyres. Typically very little compression damping is needed for most of the stroke, I'm not saying none, because that's wrong, but not as much as you would have me believe. I like my forks slowspeed 'soft', but that's just my style formed on the tracks I ride, ok?
If you are referring to compression damping as being vital to controlling bottom out in the majority of forks out there NOW, then it's unfair to ask so much of them. If so are you talking hispeed or lowspeed; if so what bodyweight, spring rate and hences oil weight are you suggesting to tune with?? Cos that's about the only way you can do it. Sorry, I don't really like these types of arguments (this entire thread) because it's so vague with limitless boundaries and could go on til next week.
I think it'd be great with position sens. damping where we can tune the comp-damping at all areas of the stroke (hoperfully independently), especially the end of the stroke and hence bottomout, if that was what you were saying then I agree. But I think most forks out there now are really lacking in more ways than one. I'd really like to hear other people interested in suspension and other engineer's perspectives on this.
PS From what I've just read, you guys say TPC+ generally operates in the slower speed range. Sorry about that, I assumed Manitou was going to make it operate primarily at the speedier end of things. |
| Speed ranges | Dougal
Feb 24, 2002 9:50 PM | | Don't confuse damper speeds with bicycle speeds, they're entirely different.
When people talk about wanting a more supple low speed ride you actually want less high speed damping, because that's where the suppleness comes from.
Ask people who've been riding Romics double shock. The adjustable low speed compression makes a huge difference in bike handling and chassis movements but doesn't change the bump response much at all.
Compression damping is needed and is far more vital than you expect. With no compression damping your fork would bottomout riding through a small pothole, it's there and working, you just don't know it.
Position sensitive damping is a complete waste of time in the context you're talking about, speed sensitive damping however is a must for good performance and makes the difference between a good and average ride.
TPC+ works on the first 40mm of stroke from sag, at speed you've got more things to worry about than a mere 40mm of nice feel in your suspension. It is good for the wow factor though, my fork is far more active than any other I've ridden on the really small stuff.
Dougal.8m.com |
| Speed ranges | sledneck
Feb 24, 2002 11:33 PM | | Dear Dougal, tell us all what you're getting at. Let it out, whatever it is. This is getting annoying trying to piece together your argument in bits and pieces. I think I understand more about susp. than you realise, and I have never confused bicycle speed with wheel 'speed'. Another question, why would you expect on shocks other than the romic you described, that low speed adjustments would affect high speed damping to a great degree anyway? I'm not a shock designer, so I can only deal in high speed and lowspeed for the sake of discussion, which I admit makes for more than a limited understanding. But still, I'm not buying your argument, which IMO, just turned around and went the other way. Whoever said that good damping was strictly position sensitive? Of course it is only going to supplement the inherant ss damping, but make it better, more fine tuned. Just like for bottomout, to assist the spring element and have finer control. It's all basically the same thing. But I'm dropping this, however interestingly it would seem now that the Jnr T you bagged for the last 3 years for having true ss damping, was secretly your ideal fork. |
| re: Should I change to heavier oil or heavier springs? | jrm
Feb 24, 2002 9:12 AM | | Springs for sure... |
| I have heavy springs for $15 | airwreck
Feb 24, 2002 8:59 PM | | I have a pair of heavy springs for $15 plus shipping. They are red and came off a 130mm Marzocchi fork. Actual length of spring is 215mm |
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