dlaing

Do they make impact hex bits in metric? Torx impact bits might be even better if you can find them.

Now that Ratchet has seen the light, I believe that a consensus can be reached here is my black magic target sag number calculator for your typical Guzzi V11 with 80kg or 175# sport touring rider. Believe it or not, I paid respect to group think and bent the numbers towards those numbers of Brian and Ratchet, believers of 15/30% front and rear. And I cut the modifier for rider weight in half of what I expect would be the accurate modifier. I am losing my individuality by compromising!!! REAR Sachs 10mm unladen 8.3% 30mm laden 25% FRONT 20mm unladen 16.7% 35mm laden 29.2% MODIFIERS (all are rough guesses or opinions...what is your's) *Racing, subtract 1 to 5 mm from laden sag. *Touring, add 1 to 5 mm to laden sag. *Frequent two up, subtract 1 to 6 mm from rear laden sag, and subtract about half of that from front sag. Note: this is assuming sag is measured without passenger. *Ohlins, add 5mm to rear laden sag. *Progressive springs, add 2mm to laden sag and subtract 1mm from unladen sag. *Short legs, add laden and unladen sag at a ratio of maybe 4mm additional laden for every 5mm additional unladen. (because shock needs to be firmer as travel decreases) *Rider weight greater than 80kg, add 1mm rear laden sag for each additional 20kg, and 1mm front laden sag for each additional 40kg *Rider weight less than 80kg, subtract 1mm rear laden sag for every 20kg less than 80kg and subtract 1mm front laden sag for every 40kg. *Personal preference, (no sag nazis here) add or subtract whatever you want to laden and or unladen sag numbers.

So that means you are at about REAR 8mm 7% unladen 29mm 24% laden 21 17% difference FRONT 28mm 42mm 14mm difference I think you are beginning to see the light But I think that is too little preload in the front. I think if you try Docc's numbers you will be pleasantly surprised. Just don't ride like him or me.

No, you are messing them up defending Ratchet's misleading notion that ideal sag numbers don't vary relative to rider weight or more precisely the ratio of bike to rider weight. I have proved it mathematically but you are too dense to get it. Do I need to take it to a more absurd level? Ok let us make the rider really light and put a 2.34489796kg remote controlled robot with camera onboard in place of the rider. Q. How much is that going to deflect the spring? A. not much. Q. if it deflects the spring not much, how soft of a spring are you going to need to get the 1kg to deflect the spring 18mm? A. really phreaking soft. Q. If the spring is really phreakin' soft, how is the bike going to handle? A. like crap. Q. What would the proper sag numbers be for a set up like this? A. Probably for the rear about 25%unladen and 25.1%laden sag. The front maybe 30%unladen and 30.1% laden. Sorry but the 15/30% would make the bike handle like crap. Because of the excessive preload, it would be harsh ride yet it would bottom out because the spring is too darn soft. Q. Do you understand yet? A. Not much chance as you are programmed by group think. I'll admit following your guidelines, it will be a lot better than it was when the bike shipped for 90% of riders. I hope if Forrest ever gets a V11 he'll set the sag properly, whatever properly is... Glad I gave the warning about possible diatribe.

How did I miss that. I thought Ratchet meant just that. I guess I totally missed it when he wrote that the rider weight would determine unladen sag. Of course it is the bike weight!!!! Must have been a typo by Ratchet.

Let us plug into your equation Sumo Sammy 250Kg rider and Willie Shoemaker 50Kg rider and assume h bike weighs 250Kg. First Willie Shoemaker Let R = 50kg (assuming weight is directly over axle for simplictity) Let G = 125kg (half of 250kg assuming 50/50 weight split for simplicity) Let R + G = combined rider and Guzzi weight 175kg Let A = unladen sag, measurement in mm of Guzzi only. A varies inversely with spring rate and directly with load. Let B = laden sag, measurement in mm of Guzzi and rider. B varies inversely with spring rate and directly with load. Now then. R 50kg determines A (in mm) If the spring deflects 18mm we can assume the spring at the rear is about 100kg/18mm or since 18 goes into 100 5.555555555555 times the required spring would be 5.5kg/mm (the swing arm is at about a 2:1 ratio, so 50kg must be doubled to obtain the estimated THEORETICAL spring rate at the rear. At the front it would be halved to 25kg/18mm since there are two fork springs.) R + G 175kg determines B (in mm) (here is Ratchet's mistake. The weight alone does not determine the laden sag here. The weight and the preload determine the laden sag of a given spring, but to humor the three people are actually reading this far, the 175kg would deflect the 5.5kg/mm spring about 64mm if no preload was added. If you add preload you would need ~28mm of preload to bring it to the magic 36mm. Looking at Sumo Sammy Let R = 250kg (assuming weight is directly over axle for simplictity) Let G = 125kg (half of 250kg assuming 50/50 weight split for simplicity) Let R + G = combined rider and Guzzi weight 375kg Let A = unladen sag, measurement in mm of Guzzi only. A varies inversely with spring rate and directly with load. Let B = laden sag, measurement in mm of Guzzi and rider. B varies inversely with spring rate and directly with load. Now then. R 250kg determines A (in mm) If the spring deflects 18mm we can assume the spring at the rear is about 500kg/18mm or since 18 goes into 500 ~28 times the required spring would be 28kg/mm (the swing arm is at about a 2:1 ratio, so 250kg must be doubled to obtain the estimated THEORETICAL spring rate at the rear. At the front it would be halved to 125kg/18mm since there are two fork springs.) R + G 375kg determines B (in mm)the 375kg would deflect the 28kg/mm spring about 27mm if no preload was added. If you add preload you would need ~9mm of preload to bring it to the magic 36mm. So one has 9mm and the other 28mm of preload but it is all theoretical. Still it proves you are not getting the same resulting 'ride' following the 15/30% rule. Although Ratchet and Company will deny it to the grave. I am about twice Willie Shoemaker's weight and probably have about 30mm of preload and it is not bad. In the real, non-theoretical world, I suspect a very light rider following the 15/30% rule would end up with too much pre-load, and the Sumo Sammys too firm of a spring. YMMV but I'll continue recommending what the experts suggest, modified by rider weight and preferences.

Who is making excuses? Few of us are out racing. But alot of us are trying to help people better set up their V11s. Why don't you go tell slow kitty to forget all about why the Guzzi handles like crap and to go learn to ride? Would that be a responsible thing to do?

Not completely true. It may be a case of splitting hairs, but there is some progressiveness even when using straight rate springs. But generally we can ignore it. My measurements could be a little off but here is what I got when I installed my Penske with 550# spring ~8 turns preload: unladen 21mm laden 50mm difference 29mm (the effect of only the rider's weight) I then added ~10 more turns of preload and got: unladen ~5.5mm laden ~31.3mm difference 25.8mm I suspect the change in difference between 29 and 25.8mm is due mostly to the gas in the shock. Again predictability goes out the window FWIW Penske recommends laden sag between 7/8" and 1-1/6" (22.2mm and 29.6mm) So, by there recommendation I should add preload or get a firmer spring to reduce sag at least ~1.7mm to get within their range. But I don't want to reduce unladen sag at all. 5.5mm is small enough! I am pretty sure the HyperPro rising rate spring would improve the ride and better match the front. ...someday.

It is a good clear article, and the coverage on how to measure and correct for errors due to stiction is excellent. But it over-simplifies the process by not discussing unladen sag at the front. And like all of the expert writings, it does not go in deep into variations of bikes and riders and preferences. They suggest 25-30mm laden front and rear. And they suggest 5mm unladen rear. So, these experts suggest ~ 4%/22-25% not 15%/30% at the rear. Wrong. Preload does much more than that. It F's up your ride if too much or too little and it F's up Ratchet's math as he tries to determine proper spring rate for people all over the globe.

I am glad you brought up optimal preload. I have not read anything at all clear on that. We do know that too much preload is a very common and often bad problem. But what is too much? The Willie Shoemaker example I gave would be too much. The Sumo Sammy example would be too little. Perhaps it is all much ado about nothing and all of us 150-250# riders will be fine within any of the experts ranges. Certainly bikes ship well out of those ranges and at the very least it is an easy improvement.

Nice clear way of laying it out. The only problem is that you are misleading when you said, "Let A = unladen sag, measurement in mm of Guzzi only. A varies inversely with spring rate and directly with load." By adding preload one can make unladen sag equal 0mm, or by completely removing preload one can make it sag as much as the bike's weight forces it. So if you are relying on the A to calculate B-A=D, you are going to get a BAD result Excellent point! I suspect Ratchet will soon see the light and realize that his "A" measurement is distorted by the preload, and that he is misleading Sumo Sammy and Willie Shoemaker. But Ratchet is not alone in misleading. Most sag guides are an over-simplification. Luckily most of the time the over simplifications work well enough. I just think we can go better that simply saying everybody should set both front and rear to 15/30% ±5mm difference between laden and unladen.

The bike needs to be supported and you need be able to support AND move the swingarm so that the bolt can be removed and then re-inserted. Also, you don't want the rear dropping down and damaging the shaft. The tire can stay on. I had to remove my airbox to remove the shock. It may be easier to remove just the lower shock bolt and then remove the spring, if that is possible?????????

For simplicities sake magic numbers are a good idea, but it also good to know how to adjust the recommended numbers. Regarding the front to back issue, I think it an appealing concept to make the front sag match the rear, but my experience and the experience of experts suggest that free sag should be greater in the front, and the difference between laden and unladen should be less in the front. From http://www.peterverdonedesigns.com/springs.htm http://www.propilotsuspension.com/setuptips.htm Front 35-48mm laden 25-30mm unladen Rear 30-40mm laden 5-10mm unladen Traxxion http://www.traxxion.com/technical.forkspr.install.shtml Front 35mm laden 20mm unladen Could not find rear recommendation except for Max mentioning 10mm unladen in the traxxion forum Unfortunately Race Tech does not cover front free sag. http://www.race-tech.com/SubMenu.asp?cMenu...1&showPage= Bike Type Front % Front mm Rear % Rear mm Rear Free Sag mm Street Bikes 28-33% 30-35mm 28-33% 30-35mm 0-5mm Road Race Bikes 23-27% 25-30mm 23-27% 25-30mm 0-5mm

Rider only sag is the difference between the sag without rider and with rider. It is as simple as that. Relying on a rider only sag of 18mm you are completely ignoring bike weight and compensating for it with pre-load. This is a mistake. You should get the proper spring, and not compensate for the wrong spring with pre-load. Every expert agrees about this but you dare to disagree. Using your strategy, if we take Sumo Sammy and Willie Shoemaker, Sumo Sammy will have no preload and a harsh spring and Willie Shoemaker will have too much preload and will bottom out frequently. Following my struggles of measuring without and assistant, my fork measurement was done by you. (eternal gratitude ) The rear spring of my Penske's sag was measured by my wife, multiple ways and times to ensure accuracy....with a plastic caliper!!!!

Willie Shoemaker's weight plus half the bike's weight is 175kg Sumo Sammy's weight plus half the bikes weight is 375kg Without preload, 175kg will deflect Willie Shoemaker's 5.5 kg/mm spring 64mm Without preload, 375kg will deflect Sumo Sammy's 27.8 kg/mm spring 27mm Following the 18mm rider only sag rule, Willie Shoemaker is under sprung and Sumo Sammy is over sprung. Most of us on this forum are riding bikes of the same weight and our weights are not that different, but a different rider only sag will be required for our various weights. OK, now I am late for work

You are not getting it. You suggested that 18mm rider only sag produce the same ride for any rider weight. This is not true. FWIW preload does have an effect on rider only sag, but that has little relevance t this argument. What is relevant is that for all intensive purposes rider only sag is the best measurent to indicate whether or not a spring is firm enough as deflection is proportional to rider weight. But it is not proportional to bike weight unless you had no preload. Let me see if I can help you understand this. For simplicities sake we will use non-real world extreme number: Bike wet weight 250 kg Rider 1 Willie Shoemaker weight 50 kg Rider 2 Sumo Sammy, weight 250 kg Sitting over the rear axle for simplicity's sake To get an 18mm rider only deflection Willie Shoemaker would need a spring rate of 100kg/18mm and since 18 goes into 100 5.555555555555 times the required spring would be 5.5kg/mm To get an 18mm rider only deflection Sumo Sammy would need a spring rate of 500kg/18mm and since 18 goes into 500 27.77777777778 times the required spring would be 27.8kg/mm Now this would be all well and fine, but the spring must also support the bike's weight. Ideally the bike weight also would have an ideal deflection, MEASURED WITHOUT PRELOAD. If you select the spring rate based on rider weight, only one rider's weight will be the perfect match for the bike. More math to come...I have to get to work

That translates into 18mm unladen and 36mm laden with an 18mm rider only. Probably just about what Ratchet recommends. Maybe you guys have the numbers right. I would bottom too much with 15/30% sag at the rear. I measure sag sitting in my "normal" 75% rearward position in the saddle, but when I ride I sometimes slide back, and more often, not by choice, slide forward. When slid forward, I would not be surprised if sag numbers approach the balanced front and rear numbers that you guys use. Still I find the front to be too soft. But setting the fork fluid higher could fix that without reducing my sag. I do think a progressive spring in the shock would better match front forks air spring.

Yes, but you will notice I also said I would go firmer and more progressive at the rear. This would balance better with the front. Travel is relevant. I believe it should translate proportionately, so 120mm to 136mm is the same ratio as 18mm to 20.4mm, a difference of 2.4mm. But yah, certainly I am not going to lose sleep over 2mm, but the math is simple. 120mm divided by your magic 18 equals 6.66666666666666. (Is Ratchet guided by Satanic voices in his head? Just Kidding! ) Sounds good to me! Perfection is never obtained. The pinnacle is subjective. There are many excellent suspension options out there.

10mm rider only sag might be brutal using Marzocchi shocks and factory recommended compression settings

Excellent question! I don't know if I have a good answer. Here is an attempt, but if someone else could help answer, please do! The progressive action of the air spring does help negate the need for less rider only sag in the front than the back. The front needs less rider only sag because of what happens when the weight shifts forward to the front during breaking. During acceleration the weight is also shifted to the rear, but for complex yet obvious reasons any bottoming of rear suspension during acceleration is less critical to stability than bottoming of forks during braking. I was thinking relative to how it came when purchased. As far as making the bike handle better, I think it is possible the front cannot go too low, within the limits of fender and wheel risking contact. As for the rear, again, I am not sure it can go too high, although I would not push it because of shaft angles. For me, I am happy with it being higher in the rear than how it was when I bought it and lower in the front. I have not gone lower in front because I have a problem of sliding forward too much in the Corbin saddle. Ergonomics trumps handling Based on my limited amateur road riding experience and Ohlins specs and general sag recommendations from various experts. By saying, "more sag in the forks" I meant and should have said, unladen sag. Yes we are discussing rider only sag, but it all interacts, and is all important.

The spring rate should match the needs of the combined weight of bike and rider. Selecting a spring with an 18mm deflection from rider weight is only matching the rider's weight and not the bike's Selecting a spring based on bike and rider combined sag also does not match the bike and rider's combined weight because the preload throws the numbers off. So, using a fixed target does not work perfectly.

Ratchet Replied I warned there would be diatribe!

From SlowKitty's thread on how his or her bike handles, I thought the points that Ratchet brought up are important and deserve there own thread before it distracts from helping slowkitty find a solution. I replied in that thread: From my experience, the 18mm target sounds like a good target for the rear with a Sachs shock. I think lighter rider may need less and heavier riders more because of the ratio of the bike to rider weight, but it is not a big difference. I think the front springs should provide less sag difference than the rear spring because of the need for the front suspension to handle bottoming. Ohlins suggests Without rider: Rear: Road and Track 5-10 mm Front: Road and Track 25-30 mm With rider: Rear: Road and Track 30-40 mm Front: Road and Track 35-48 mm Notice they recommend more difference in the rear, but then again the rear wheel travel is about 140mm. Other experts generally recommend firmer springs and less sag than Ohlins does, and I agree with them, up to a point. I think if you take the tighter Ohlins numbers you would be doing very well: Without rider: Rear: Road and Track 10 mm Front: Road and Track 25-30 mm With rider: Rear: Road and Track 30 mm Front: Road and Track 35 mm For a difference of about Rear: 20 mm Front: 5-10 mm What you set your sag to should also take into consideration geometry. I find that a high rear and a low front make the bike handle better. Some of that can be adjusted by moving the triple clamps down the forks, but more sag in the forks than at the rear is a good thing. My front is 26mm/36mm with a difference of 10mm. I think I need a stiffer spring up front, so I guess for my front the 18mm±5 does not meet my needs, and I need a little less than 10mm difference. But my rear is 6mm/31mm for a difference of 25mm. I think I need a stiffer, but more importantly a more progressive rear spring. Probably 8mm/28mm would be about ideal for me. But my Penske rear suspension is probably about 136mm of travel as opposed to the 120mm Sachs. If I was using the Sachs, 18mm rear would be just about perfect.

Did you lower the triple clamps down the forks yet? You will want to make sure you have atleast 130mm of travel clearance above the fender from the fully extended. To make measuring easy, take 130 and subtract bike only sag, and make sure you have that much room between the fender and what it will hit if you lower the front too much. Increasing preload in the rear might also help. But knowing your sag is really step number one. (After ensuring that nothing is busted or out of alignment and that the shaft is aligned correctly as Pete recommended checking)