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  #11  
Old 07-Jun-2005, 06:29 AM
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DSC Member Shazaam! Shazaam! is offline
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Lighter Springs:

• 58N/mm (331 lbs/in) springs have the Ohlins’ stiffness code -13, rider weight 55-60Kg

• 1091 length spring is not available with Ohlins’ stiffness code -14, rider weight 60-65Kg

• 62N/mm (354 lbs/in) springs have the Ohlins’ stiffness code -15, rider weight 65-70Kg

• 64N/mm (365 lbs/in) springs have the Ohlins’ stiffness code -16, rider weight 70-75Kg


So, Ohlins doesn't make a -14 spring in the 1091mm length. They do make a -13, 58N/mm spring for a rider weight of 55-60 Kg which is too light for you assuming you're wearing 4Kg of gear.

You haven't mentioned the front forks. Have you re-sprung these also, and are you getting full travel? Also remember to set your sag measurements with a half tank of petrol.
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  #12  
Old 07-Jun-2005, 10:53 PM
Bryan996 Bryan996 is offline
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Shazaam, I have ohlins on the front as well and have never had any problems other than it dives on the brakes a little and will therefore then to sit up if running into a corner. They still have the original springs in.

static sag on the front without rider is 26mm, I will check later the value with myself on it when I get some help to measure.

Looks like I have the best option for rear spring as I am just about getting full deflection on the shock. Again the front just about gets full travel to.

thanks again.
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  #13  
Old 07-Jun-2005, 11:55 PM
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DSC Member Shazaam! Shazaam! is offline
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The front static sag should be 30mm, so the front needs softer springs as well.

A mismatch in spring rates front to rear is likely the main cause of your handling difficulties. Every time you hit a bump the bike's fore-aft geometry changes (i.e. CG, steering head inclination, trail, pitch.)

Once you've got the proper springs, then if it bottoms too easily in long dips increase your compression damping 2-4 clicks until it begins to feel harsh over changes in road paving.
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  #14  
Old 07-Jun-2005, 11:58 PM
nathanTX nathanTX is offline
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Shazaam, what is the source of that table showing recommended rider and free sag? Not doubting it or you (hey, you're the resident expert and I'm a newb), but that is a higher front rider sag number than I have normally seen when working with other bikes. I have always been told by people in the know to set front rider sag between 30-40mm. That is based on the calculation of using roughly 1/4 to 1/3 of the available travel. Most Japanese sportbikes run between 110 and 125mm of front travel. Therefore 30-40mm of rider sag. What is the available travel on Ducati forks? Well, I realize that you'll have several variations for Showas, Ohlins, etc. for the various years, but do they have more than 125mm of travel as a rule? If not, what is the reasoning for having 45-50mm of rider sag?
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  #15  
Old 08-Jun-2005, 12:13 AM
nathanTX nathanTX is offline
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add-on: Found the available travel in my handy dandy owner's manual. 127mm of available travel for my 2001 996 bp with the Showas. So, using my experience, I would expect front rider sag of roughly 40mm rather than the listed 45-50. Thoughts?
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  #16  
Old 08-Jun-2005, 02:07 AM
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DSC Member Shazaam! Shazaam! is offline
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The table was taken from an Ohlins Spring Manual.

You’re correct though, the accepted range of values is typically 1/4 to 1/3 of total travel so 32mm to 42mm would be correct for your Showas for the street.

If you preload to get 32mm of sag then the rider’s neutral position is closer to the fully-extended position so you increase the tendency to hit the top bump-stop but the suspension moves less, resists the larger forces generated by the higher speeds, and giving better handling. That’s why this is a good track setting.

With less preload you’ll get 42mm, which softens the ride considerably for rider comfort but increases the tendency to bottom-out on severe bumps. If you want a plush ride without bottoming-out then you shouldn’t buy a sportbike.

In short, when you set sag, you are determining how much suspension travel will be available for bump absorption. The maximum travel is decided by the bike designer, i.e. a lot is needed for off-road bikes, very little for track bikes because of the smoother surfaces they encounter.

So a 996’s stock suspension would bottom-out regularly off-road, but allow too much squat and dive on a typical track - which is why recommended sag values for the track are lower than street values.

That means that a sag value for a given suspension travel can be selected to maximize comfort at the sacrifice of larger suspension movement that limits handling performance. Bryan’s original concern arose from a question of comfort to avoid “kidney shake” so it would be better to err with a higher sag value than a lower one.
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  #17  
Old 08-Jun-2005, 03:00 AM
nathanTX nathanTX is offline
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Great info! I'm sort of the go-to guy in my group when it comes to suspension, so I wanted to be sure my assumptions were correct. Interesting that Ohlins (who one would assume would make outstanding recommendations) would list rider sag on their chart a bit higher. Wonder what their reasoning is??

To contribute to the original question more, Shazaam has supplied fantastic info above. And there is a lot of it! So, Bryan if you're still seeking a remedy yourself, keep the simple ideas in mind first. Sag is the most important because everything else is affected by spring preload and chassis attitude. While many of the numbers listed above are very specific, you don't have to hit those exact numbers. They are a target and getting in the right ballpark will be good enough for most of us mortals. From there, you can fine tune for specific uses, styles, and preferences. But don't sweat it if you are one spring rate away from what the Ohlins chart says is optimum. Take some good sag measurements, and try to keep a balance between front and rear (if you're a little stiff out back, don't let the front be a little soft). But, like many have recommended, at your weight, the only real solution may be a professional rebuild. Too many things start needing to change (when you mess with one thing, another gets thrown out of whack) and the only real way to fix it all is to have someone who really knows what they are doing attack the entire setup.
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  #18  
Old 14-Jul-2005, 04:43 PM
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Mello-Yellow Mello-Yellow is offline
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Mood: When's the sun coming out
How much travel should be left

After the suspension has been setup front and rear (sag set etc)
How much travel should there be left.

After fitting a cable-tie round the front fork and rear shock rod i had 13mm of unused travel on the front and the rear was showing that all the travel had been used up.

how much should i be using.

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