![]() |
Register | FAQ | Members List | Calendar | Today's Posts | Search | Contact | ![]() |
![]() |
|
![]() |
![]() |
Registered
Members: 639 | Total Threads: 50,828 | Total Posts: 518,560 Currently Active Users: 843 (0 active members) Please welcome our newest member, JodyG219 |
![]() |
|
![]() |
|
Thread Tools | Display Modes |
|
![]() |
#1 | |
Registered User
Join Date: Jan 2017
Location: Milton Keynes
Bike: M1100evo
Posts: 233
|
Quote:
What does it matter what the bike suspension does without a rider on it?! Why is it even relevant? That's what I still don't get. |
|
![]() |
![]() |
![]() |
#2 | |
Gold Member
Join Date: Mar 2004
Location: lincoln
Bike: No Bike Yet!
Posts: 876
|
Quote:
Simples really, if you have no static sag your bike will top out with a Bang in some instances, for example if you hit a small crest at speed, your suspension will top out, not good. |
|
![]() |
![]() |
![]() |
#3 | |
Registered User
Join Date: Aug 2011
Location: Southampton
Bike: M1100evo
Posts: 2,465
|
Quote:
I'm often accused of being a windbag - here's the proof! ![]() |
|
![]() |
![]() |
![]() |
#4 |
Gold Member
Join Date: Mar 2004
Location: lincoln
Bike: No Bike Yet!
Posts: 876
|
|
![]() |
![]() |
![]() |
#5 | |
Registered User
Join Date: Jan 2017
Location: Milton Keynes
Bike: M1100evo
Posts: 233
|
Quote:
One of the reasons for setting 'sag' is so that with your weight on the bike the forks\shock have enough travel\range to decompress as well as compress. But they can both still technically top out. If preload, and therefore (rider) sag, is set correctly, there will be enough travel in the fork\shock for the suspension to move up and down, then compression\rebound damping controls the rate at which that happens. If all that is setup properly (in combination with the correct spring) then top out\bottom out shouldn't happen, but none of that really has anything to do with static sag. As far as I can tell anyway. |
|
![]() |
![]() |
![]() |
#6 | |
Gold Member
Join Date: Mar 2004
Location: lincoln
Bike: No Bike Yet!
Posts: 876
|
Quote:
Sorry Bob, but having been involved in racing myself and helping others with bike setups, builds etc, you NEED static sag, it suspends the weight of the bike before the rider gets on. If you have no static sag on the front of the bike it will be nose high, will not corner correctly etc etc, really it will just run you off the road. Don’t take my word for it give Maxton, K-Tech, Ohlins, Wilbers etc a ring and ask them. |
|
![]() |
![]() |
![]() |
#7 | |
Registered User
Join Date: Jan 2017
Location: Milton Keynes
Bike: M1100evo
Posts: 233
|
Quote:
As per one of my last posts, I think what's happening here is that people are hanging on to snippets of information they've got about elements of suspension setup without necessarily considering the role they play in the overall setup, or the effects that other parts of the setup have on them. It was just a question though (about why people think static sag is relevant). It'll be interesting to get the views of all those people you mention, but no doubt there will be differences of opinion from them too. EDIT: Plus it's important to note when we're discussing this, I refer to 'static sag' as the amount the bike suspension sinks under its own weight with no rider, and 'rider sag' as the amount it sinks with you on it. I get the impression that the terminology is being mixed up. Last edited by Uncle Bob; 20-06-2019 at 11:41 AM.. |
|
![]() |
![]() |
![]() |
#8 | ||||
Registered User
Join Date: Aug 2011
Location: Southampton
Bike: M1100evo
Posts: 2,465
|
I'm in no way (and certainly wouldn't profess to be) a suspension expert. I rely on proven experts like the two I've quoted above if I want to know anything. So a few words on their qualifications...
Niall Mackenzie is a successful former racer with 7 500GP podiums and 3 BSB championships. He has a wealth of experience on a wide range of machines under a wide range of conditions. Tony Foale is a professional engineer, Bachelor of Technology and Master of Engineering Science. Sometimes, when a person is an acknowledged expert on something, people say "Oh, he wrote the book on that". Well, when it comes to motorcycle suspension and chassis design, Tony Foale actually DID write the book on that! (Check out his website https://motochassis.com/ there's a lot of useful information and interesting articles there.) When people with that experience and those qualifications say the same thing, I tend to believe them. Quote:
• (on the rear shock), under heavy braking when all weight is transferred to the front • (at both ends), going over a rise in the road like a hump-back bridge • (at both ends), dropping into a hollow or pothole Quote:
Better to minimize the topping-out by setting the correct sag than masking the problem with excessive damping. Quote:
"• The static loaded position of the suspension is closer to the rebound stops, and so there is less suspension movement available before topping-out. So that occurs more often." Quote:
While suspension experts like the one Mossleymonster visited will no doubt be able to set the correct dynamic sag without also checking the static sag, the fact that they haven't checked it doesn't mean there isn't any or that it's not important to the overall set-up. I would still recommend that the home twiddler, without the experts' training and experience, still checks both figures to ensure that the final set-up is correct. |
||||
![]() |
![]() |
![]() |
#9 | |
Guest
Posts: n/a
|
Quote:
|
|
![]() |
![]() |
#10 | ||
Registered User
Join Date: Aug 2011
Location: Southampton
Bike: M1100evo
Posts: 2,465
|
Quote:
Quote:
With insufficient static sag (my words): "• The static loaded position of the suspension is closer to the rebound stops, and so there is less suspension movement available before topping-out. So that occurs more often. • The preload force means that when the suspension does top-out, it does so in a harder fashion." Niall Mackenzie describes what that feels like to the rider and his experience tallies exactly with the recorded behaviour of the wheel in those circumstances as shown in Tony Foale's graph. As I mentioned when I was describing my own experience, it's quite possible to set your dynamic sag within the recommended range and yet still have no or minimal static sag so I always now check the two and make sure they are both within their recommended ranges. I would add that the same amount of factory set preload that gave me zero static sag on the Öhlins DU737 with the 115N/mm spring, gave the perfect static sag with a 105N/mm spring. Not sure I can add any more so I hope that helps. |
||
![]() |
![]() |
![]() |
#11 | |
Registered User
Join Date: Nov 2017
Location: Barnsley
Bike: M1100s
Posts: 238
|
Quote:
__________________
Always remember. Your home is at risk if you set fire to it. |
|
![]() |
![]() |
![]() |
#12 | |
Registered User
Join Date: Jan 2017
Location: Milton Keynes
Bike: M1100evo
Posts: 233
|
Quote:
As for the second point, it's kind of true, but that's what rebound damping is supposed to control. Reading this thread it seems that emphasis is perhaps being put on certain elements of suspension setup and not considering the combined effects of the actual equipment and how it's setup as a whole. |
|
![]() |
![]() |
![]() |
#13 |
Gold Member
Join Date: Mar 2004
Location: lincoln
Bike: No Bike Yet!
Posts: 876
|
Sorry, but I disagree completely, if you have no static sag you are compromising the bikes ability to use it’s suspension safely, believe me, you do not want your bikes suspension topping out when the suspension goes light when you are at speed etc.
|
![]() |
![]() |
![]() |
#14 |
Registered User
Join Date: Jan 2017
Location: Milton Keynes
Bike: M1100evo
Posts: 233
|
Having no static sag does not mean your bike will definitely top out, unless the bike is riding itself around. Is it?
|
![]() |
![]() |
![]() |
|
|