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Old 07-07-06, 10:22 AM   #1
gspen
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Default Front & rear suspension settings

I'm about to fit a tank bag & tail pack and would like to know the recommended front and rear suspension settings. I'm average weight (11st) but have experienced occasional bottoming out of the front forks even without the extra luggage.
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Old 07-07-06, 10:39 AM   #2
Blue_SV650S
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Hiya, you didn’t mention which model you had. If you have an early curvy like mine there are no bits to twiddle (except rear preload I suppose). So you are kinda stuck with what you have unless you start putting new oil, springs etc in.

A cheaper alternative is to raise the oil level in the forks (reduce air-gap). As it is a sealed system, the air in the forks kinda works as a pneumatic spring. When the forks go down (the nose of the bike dives) you are effectively compressing the air in the forks, the less air you have to start with, the more compressed it becomes as the movement is the same. This compressed air is obviously going to have the effect of trying to extend the forks, you are therefore in this manner increasing spring (pneumatic) strength at the top of the fork travel range, which is probably the effect you are after??!

Make sense?
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Old 07-07-06, 11:10 AM   #3
gspen
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[quote="Blue_SV650S"]Hiya, you didn’t mention which model you had. quote]

Thanks for your soultion, but sorry, I should have metioned it was a new model with the adjustable front forks. I've not had this option on a bike before so am pretty clueless as to what the settings mean.
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Old 08-07-06, 07:23 AM   #4
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Not much mate. Not 100% where 11stone fits in but if thats more than 70kg your fork springs are too light. What you are aiming for is a difference of 25-30mm in ride height difference from the bike sitting under its own weight to you being on it with both feet up. Handy to have another person or two to do this!

That said, once you've set this up right you really shouldn't need to worry about any other changes just because you've put on a tank bag and rack.
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Old 08-07-06, 09:15 AM   #5
21QUEST
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Quote:
Originally Posted by PeterM
Not much mate. Not 100% where 11stone fits in but if thats more than 70kg your fork springs are too light. What you are aiming for is a difference of 25-30mm in ride height difference from the bike sitting under its own weight to you being on it with both feet up. Handy to have another person or two to do this!

That said, once you've set this up right you really shouldn't need to worry about any other changes just because you've put on a tank bag and rack.
PeterM , can you please clarify that as from how I read the above that is seriously wrong.

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Blue, mate, having read a lot of your stuff I'd say 'in your head' is unknown territory for most of us
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Old 09-07-06, 12:06 AM   #6
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Okay.

You sit the bike vertical on its tyres and measure from the ground to a fixed point on the bike near the line with the axle, front and rear.

From there have somebody hold the bike vertical and climb on board, assume the normal riding position. Have a 3rd person re-measure from the ground to those points.

There should be the 25mm difference between these two measurements.

This is simply referred to as setting the sag, I have never come across anyone who breaks it up into 'bike' and 'rider' sag as the only one that matters is with the rider on board. Logically this is because the weight of the bike is a constant but the rider weight changes and the suspension needs to be set up to compensate for this.
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Old 09-07-06, 12:43 AM   #7
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http://www.gostar-racing.com/club/mo...0YOUR%20WEIGHT

check it out.
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Old 09-07-06, 12:51 AM   #8
21QUEST
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Quote:
Originally Posted by PeterM
Okay.

You sit the bike vertical on its tyres and measure from the ground to a fixed point on the bike near the line with the axle, front and rear.

From there have somebody hold the bike vertical and climb on board, assume the normal riding position. Have a 3rd person re-measure from the ground to those points.

There should be the 25mm difference between these two measurements.

This is simply referred to as setting the sag, I have never come across anyone who breaks it up into 'bike' and 'rider' sag as the only one that matters is with the rider on board. Logically this is because the weight of the bike is a constant but the rider weight changes and the suspension needs to be set up to compensate for this.
Wrong again.

Okay lets go with rider sag. What you are looking for the the difference between the measurements of the suspension unloaded(topped out) and the suspension loaded(rider)

Front : USD> measure the distance from the dust seal to the bottom of the stanchions . For RWU forks(sv etc)> measure from the dust seal to the bottom of the bottom yoke.

Rear vertical measurement from the axle to anywhere above say seat unit subframe etc.

Now plunk the rider on board and take measurement at same points. Difference is your rider sag.

As an aside it is agueable that bike sag is more important than rider sag . Think about it

Cheers
Ben
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Old 09-07-06, 08:10 AM   #9
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Quote:
Originally Posted by 21QUEST
Quote:
Originally Posted by PeterM
Okay.

You sit the bike vertical on its tyres and measure from the ground to a fixed point on the bike near the line with the axle, front and rear.

From there have somebody hold the bike vertical and climb on board, assume the normal riding position. Have a 3rd person re-measure from the ground to those points.

There should be the 25mm difference between these two measurements.

This is simply referred to as setting the sag, I have never come across anyone who breaks it up into 'bike' and 'rider' sag as the only one that matters is with the rider on board. Logically this is because the weight of the bike is a constant but the rider weight changes and the suspension needs to be set up to compensate for this.
Wrong again. Oh really?

Okay lets go with rider sag. What you are looking for the the difference between the measurements of the suspension unloaded(topped out) and the suspension loaded(rider)

Front : USD> measure the distance from the dust seal to the bottom of the stanchions . For RWU forks(sv etc)> measure from the dust seal to the bottom of the bottom yoke.

Rear vertical measurement from the axle to anywhere above say seat unit subframe etc.

Now plunk the rider on board and take measurement at same points. Difference is your rider sag.

As an aside it is agueable that bike sag is more important than rider sag . Think about it

Cheers
Ben
Firstly, thanks to bikeageboy for putting that link up, now I understand what you are all on about when referring to static and rider sag. Us simple Australians by and large don't bother about getting sag set until you have the correct weight springs installed in the first place.

Silly me, I thought that we might use the collective research that has already been put into spring rates by suspension companies and have at least worked out whether we have springs of an adequate rate in our bike or whether different ones are required. This MUST be your starting point. Like jetting, if your mains are wrong you are wasting your time doing anything else.

Funnily enough, reading through that link confirmed the measurements that I listed in the first post, assuming the correct spring rate is fitted. Therefore I'm not really sure why there has been the huge carry-on and to say that what I posted was "dangerous" is farcical.

GSPEN - according to the racetech website, for normal street riding you would be looking at 0.745kg/mm springs, stock are 0.706 kg/mm. The softest springs listed by them are 0.8 kg/mm but perhaps another manufacturer has a softer one.
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Old 09-07-06, 10:06 AM   #10
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Quote:
Originally Posted by PeterM
Funnily enough, reading through that link confirmed the measurements that I listed in the first post, assuming the correct spring rate is fitted. Therefore I'm not really sure why there has been the huge carry-on and to say that what I posted was "dangerous" is farcical.
Yes you're right in that it confirms the amount of rider sag to set for. However, your method of measurement (included below cause this is getting confusing!) does not give rider sag, or static sag for that matter. It gives the difference between the two. That could, potentially, be dangerous as all you are doing is trying to set some degree of sag at some point in the suspension travel. Your reference, which is the static sag, could be anything. It is extremely unlikely to be an issue (and won't be if you already have the correct spring rate) but if you are only going to set rider sag then you should still do it with reference to the UNLOADED suspension length. That is the standard method of measurement, as the article bears out.

Quote:
Originally Posted by PeterM
You sit the bike vertical on its tyres and measure from the ground to a fixed point on the bike near the line with the axle, front and rear.

From there have somebody hold the bike vertical and climb on board, assume the normal riding position. Have a 3rd person re-measure from the ground to those points.

There should be the 25mm difference between these two measurements.
As for the rest of your disagreements with 21Quest... I'm keeping out of it! :lol
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