Guest captain nemo Posted November 9, 2003 Share Posted November 9, 2003 Guzzisti, I am enjoying these thoughts on suspension. I am always open to learn and apply. I went out yesterday and found that my measurement on my rear spring was incorrect. I had measured the spring with WHEEL ON THE GROUND and found the length of my spring to be 150mm. BUT, when I lifted the back end, the REAL spring length was 154mm. Consequently, I tightened the spring up considerably to a real measured length of 151mm. (the greatest amount of preloading recommended by the manual). OK, I set the bike down and noticed the rear end is more 'jacked up.' Also, it didn't seem to sink as much when I sat on it. I could hardly detect squatting. However, with the help of my girlfriend, I once again measured the height with me sitting on the bike in riding position - AND, I find that the total sag is one and 7/8 inches (48mm). This is only slightly tighter than it was before. As Lex says, this again indicates a soft spring. However, I really cannot image a tighter spring on this Guzzi. Also, I have never experienced bottoming out. Are others here telling me that their total sag is less than this? I mean, I know that I have seen articles on things like Suzuki SV1000 or Aprilia having a total sag of, say, an inch and a quarter adjusted for a real squid. But, is this correct for the Guzzi? I don't think so. Link to comment Share on other sites More sharing options...
Murray Posted November 9, 2003 Share Posted November 9, 2003 I have around 38mm for the rear on the 1100 sport and around 40mm for the front. Whilst the spring might not bottom out doesn't lean its correct. A lot of guys say this it doesn't bottom out so it must be ok. Until your ride with a correctly set up springs you won't realise there is a better ok. Link to comment Share on other sites More sharing options...
Baldini Posted November 9, 2003 Share Posted November 9, 2003 ...About 30- 35mm sag on Scura rear...I think... KB, Wales Link to comment Share on other sites More sharing options...
Mike Stewart Posted November 10, 2003 Share Posted November 10, 2003 ...About 30- 35mm sag on Scura rear...I think... KB, Wales Agreed, , 1 7/8" is alot of sag for the rear suspension. What is your body weight? The max I will run in the rear is 1.5" and have gone down to 1" of sag with rider. What is your static sag with out rider? Both sag measurements are needed to tell if your spring is the correct weight. It is also better to error on a slightly soft spring than to error toward a heaver spring rate. Don't ask me how I know! Mike Link to comment Share on other sites More sharing options...
Mike Stewart Posted November 10, 2003 Share Posted November 10, 2003 I found this method of suspension tuning on the Factory Pro site, just another wrench to throw in to get everyone confused! Basic rules for suspension tuning A primary issue with springs, front and rear, is to simply spring the ends so that when you push down on the footpegs (where most of your weight is when you aggressively corner). Both ends of the bike NEED to go up and down exactly evenly, both in travel and rate. That's without damping! General order: Select a rear spring that will just bottom out over your harshest bump that you are riding on with "normal" sag. Soften it up till it just bottoms out, then tighten preload 1/4. Check the sag and see if it's in general range of 35mm to 20mm. That's with no compression damping. Select front fork springs that allow the front end and the rear end to travel equally and evenly when you bounce on the footpegs (helps to have someone hold the bike upright). That's after you have set the rear spring as in the above step. That's with no compression damping. Rear rebound: Use just barely enough to prevent wallowing in high speed sweepers. Front rebound: Use just enough rebound to keep the front end from wallowing and drifting wide when exiting low speed corners at full throttle. Compression damping: The goal is to use as little as possible. Use the proper, perhaps heavier than stock spring to do the major work during non-braking mode riding. Use compression damping to trim if necessary and only if required. Excessive dive under braking: Use increased oil level to firm the front end under hard braking. 5mm is a significant change in modern forks. Goals are to always use the softest rear spring that works within "sag" range limit. Use just enough rebound damping to control the springs. Use as little compression damping as possible and only when required. Not everybody has a supply of alternate fork and shock springs, so you will probably have to improvise and use a bit of extra preload or a bit more compression damping to compensate for too soft of a spring. All in all, there is nothing like heeling a bike over in a 120mph sweeper with a sharp edged bump in the middle of it and knowing that you can back of just a bit over the bump, get bounced in the air and calmly land heeled over, in control, straight and unperturbed and remain at highest possible speed with no fuss or muss. That just doesn't happen if the springs aren't perfectly matched! Cheers! Marc Remember! These are hints only. You are responsible for whatever you do with this information. If you use this information and it helps your application, contact Factory Pro with results. Thanks, Marc Mike -------------------------------------------------------------------------------- Link to comment Share on other sites More sharing options...
Guest captain nemo Posted November 10, 2003 Share Posted November 10, 2003 Are you Marc or Mike Stewart? I see you live in Oakland. I used to live in Marin County. --Oh, by the way, is that you pulling a wheelie? Can you tell us how you go about it? Thanks for all of these excellent observations. I will think about them. I've tweaked the spring a bit more so that it is 149mm suspended length. My TOTAL sag now is as tight as it possibly can be - one inch 3/4 inches (44mm). The STOCK spring just cannot be any tighter than this. I wonder at these low low readings I am hearing about here. Just to let you know, I jack up the back end so that the rear tire just breaks surface - I then take a measurement at the rear reflector on the rear fender. Then I set the bike down and sit on it in driving position. My girlfriend measures again the bottom of the rear reflector. When you consider how stretched out the rear suspension is when the tire is off the ground - and then consider the bike plus the rider on that suspension, it is a wonder to me that this reading can be much tighter than my inch and 3/4!!! Really? Is everyone measuring in this way? I don't know if I would want to ride a bike with a tighter spring unless I was on a race track. Link to comment Share on other sites More sharing options...
Guest Brian Robson Posted November 10, 2003 Share Posted November 10, 2003 120 mph in a fast sweeper hitting a sharp edged bump, being lifted into the air and then carrying on with no fuss or muss! Is the sun still yellow in that world? If you are aiming to set up suspension with that in mind good bloody luck, and if you are going to do that on a Moto Guzzi you have cojones the size of water melons, and for Pete's sake videotape the evidence, I could do with a good laugh! Link to comment Share on other sites More sharing options...
Mike Stewart Posted November 10, 2003 Share Posted November 10, 2003 120 mph in a fast sweeper hitting a sharp edged bump, being lifted into the air and then carrying on with no fuss or muss!Is the sun still yellow in that world? If you are aiming to set up suspension with that in mind good bloody luck, and if you are going to do that on a Moto Guzzi you have cojones the size of water melons, and for Pete's sake videotape the evidence, I could do with a good laugh! Yep, Big Cojones! Mike Link to comment Share on other sites More sharing options...
Guest Brian Robson Posted November 10, 2003 Share Posted November 10, 2003 Saves wear on the tyres though....massive respect Link to comment Share on other sites More sharing options...
Baldini Posted November 10, 2003 Share Posted November 10, 2003 "...BBBOOIIIINNNGGGGG!!!! ...Mike realised he'd gone too hard on the suspension settings just as he approached the Woodland section..." Let us know next time you're over KB, Wales Link to comment Share on other sites More sharing options...
Guest captain nemo Posted November 10, 2003 Share Posted November 10, 2003 ...About 30- 35mm sag on Scura rear...I think... KB, Wales Agreed, , 1 7/8" is alot of sag for the rear suspension. What is your body weight? The max I will run in the rear is 1.5" and have gone down to 1" of sag with rider. What is your static sag with out rider? Both sag measurements are needed to tell if your spring is the correct weight. It is also better to error on a slightly soft spring than to error toward a heaver spring rate. Don't ask me how I know! Mike Yes I think it is better to be soft. Otherwise you could be 'ejected' when you least expect it!! I am 165 lbs. Since my Guzz has only 13k on it, I have to think this spring rate is what was intended by the engineers. I have it tweaked all the way - even that seems plenty harsh to me. One inch of sag is like a 'hard tail' with iron rods for shocks. I don't get it. Once again, I ask if my method of checking sag is the same as yours? Especially where I jack up the rear end just until the rear tire breaks surface - then take a measurement. Then of course with the bike on ground and rider in place. Note difference in measurements. If the stock V11 spring is this far out of 'correct' wouldn't it be considered a matter of recall? Link to comment Share on other sites More sharing options...
dlaing Posted November 10, 2003 Share Posted November 10, 2003 If the stock V11 spring is this far out of 'correct' wouldn't it be considered a matter of recall? I don't think it should be a matter of recall, but in your case a matter of warranty. Your measurement technique is fine, unless your tire pressure is way too low. I think something may be wrong with your spring. But let us be sure that we have all the facts correct. You weigh 165lbs and not 165Kg. You ride all the way forward in the seat. You dialed the pre-load till you ran out of thread and not just to the point where you reached some magic number of 149mm of spring length. I weigh about 220 lbs in riding gear and sit all the way back in the seat. I still have the ability to add more pre-load. I have zero bike only sag and about 1.5 inches of rider sag, giving a total of 1.5 inches of total sag. I need a heavier spring because I should not be at zero bike only sag in order to get the other sag correct. I still bottom out frequently. Reducing sag with pre-load should not bike feel harsher until you reach the zero bike only sag point. And even then I am not sure. Having too much sag could cause bottoming and thus a harsh ride. But you say you are not bottoming out. I am really suprised that you cannot reduce the sag beyond 1.75inches. You probably need to lube the threads for the pre-load rings and be sure you loosen the lock ring. At your weight, I guess I am not suprised that you are not bottoming out. I would check your bike only sag and your compression setting. Try setting your compression damping to the softest setting and see if you still bottom out on the biggest bump you face. If you do bottom out, then you need to reduce sag. If not, forget about it. The large sag number and unknown spring rate work fine for you. Unless you are at zero bike only sag, in which case you need a heavier spring. Maybe you do have a White Power shock??? Link to comment Share on other sites More sharing options...
Guest captain nemo Posted November 10, 2003 Share Posted November 10, 2003 DLaing, When I say I have the rear spring 'tweaked all the way' I do not mean that I have used up all the threads for the collars. Far from it. But what I mean is that when the rear tire is off the ground, the actual length of the spring from collar to collar is 149mm which is slightly longer than the manual recommends (151mm). This means to me that I have injected the maximum amount of preload for the spring. Now, I don't consider what my compression is set at for these sag measurements as I didn't think they were related. I will say that even though I have an inch and 3/4 long sag, the spring seems very tight and strong. Not weak and 'bungie' in any sense. As it is, it feels like it will eject me right off it is so strong. There is no way it will bottom - even when I hit a speed bump at 30 mph. Again it does make me wonder if I have a WP because I am not having any of the symptoms you all speak of at such a sag amount. I'm sure that if I kept tightening the spring collars that I could obtain a one inch sag or whatever I liked. Maybe the manual did not have my actual spring in mind. But I would say that if I set my bike at an inch and a quater sag, it would be well suited for the most extreme thrashing on the track - probably with my girlfriend on the back. The mystery continues..... Link to comment Share on other sites More sharing options...
Kiwi Dave Posted November 10, 2003 Share Posted November 10, 2003 I will say that even though I have an inch and 3/4 long sag, the spring seems very tight and strong. Not weak and 'bungie' in any sense. As it is, it feels like it will eject me right off it is so strong As I understand the mechanics, changing the preload doesn't alter the rate of the spring, only the amount of sag and therefore the available range of the shock absorber before it bottoms out (assuming the coils of the spring don't bind first). By swapping the spring for one with a greater rate will allow you to reduce the preload because the sag will be less, and it will not jack the rear up so much which should make for slightly slower steering. All this is in my mind, I'm yet to experiment with different springs, the only adjustment I've done is to reduce the preload (yet to bottom out) Link to comment Share on other sites More sharing options...
Baldini Posted November 11, 2003 Share Posted November 11, 2003 Captain Nemo, Everything I've heard or read says that sag should be about 30 - 33% of total suspension travel (travel between topping out & bottoming out). Whatever shock you're running. But...each to his own... KB, Wales Link to comment Share on other sites More sharing options...
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