pokeyjoe
High Miler
What's good for rear sag? I'm used to something in the low thirties for a sport bike, but this is certainly a different animal. 40mm? 35?
-
Ciao Guest - You’ve landed at the ultimate Guzzi site. NEW FORUM REGISTRATIONS REQUIRE EMAIL ACTIVATION - CHECK YOUR SPAM FOLDER - Use the CONTACT above if you need help. New to the forum? For all new members, we require ONE post in the Introductions section at the bottom, in order to post in most of the other sections. ALWAYS TRY A SEARCH BEFORE STARTING A NEW TOPIC - Most questions you may have, have likely been already answered. DON'T BE A DRIVE-BY POSTER: As a common courtesy, check back in and reply within 24 hours, or your post will be deleted. Note there's decades of heavily experienced Guzzi professionals on this site, all whom happily give endless amounts of their VALUABLE time for free; BE COURTEOUS AND RESPECTFUL!
-
There is ZERO tolerance on personal attacks and ANY HYPERLINKS to PRODUCT(S) or other competing website(s), including personal pages, social media or other Forums. This ALSO INCLUDES ECU DIAGnostic software, questions and mapping. We work very hard to offer commercially supported products and to keep info relevant here. First offense is a note, second is a warning, third time will get you banned from the site. We don't have the time to chase repeat (and ignorant) offenders. This is NOT a social media platform; It's an ad-free, privately funded website, in small help with user donations. Be sure to see the GTM STORE link above; ALL product purchases help support the site, or you can upgrade your Forum profile or DONATE via the link above.
-
Be sure to see the GTM STORE link also above for our 700+ product inventory, including OEM parts and many of our 100% Made-in-SoCal-USA GTM products and engine kits. In SoCal? Click the SERVICE tab above for the best in service, tires, tuning and installation of our products or custom work, and don't miss our GT MotoCycles® (not) art on the BUILDS tab above. WE'RE HERE ONLINE ONLY - NO PHONE CALLS MADE OR RECEIVED - DO NOT EMAIL AND ASK QUESTIONS OR ASK TO CALL YOU.
-
Like the new V100, GuzziTech is full throttle into the future! We're now running on an all-new server and we've updated our Forum software. The visual differences are obvious, but hopefully you'll notice the super-fast speed. If you notice any glitches or have any issues, please post on the Site Support section at the bottom. If you haven't yet, please upgrade your account which is covered in the Site Support section or via the DONATE tab above, which gives you full site access including the DOWNLOADS section. We really appreciate every $ and your support to keep this site ad-free. Create an account, sign in, upgrade your account, and enjoy. See you on the road in 2024.
Suspension Settings Question
- Thread starter pokeyjoe
- Start date
I run about the same sag with rider on board on street bikes as I do on racebikes. The difference is the sag with out the rider on board, on my racebikes there is slightly MORE sag under just the weight of the bike as the springs are stiffer then they are on a street bike so it requires less preload to achieve proper sag with rider on board.
As to what your actual numbers are, personally I shoot for around 25 - 30 mm of race sag (sag with the rider on board) and around 5 - 10 mm free sag (sag under just the weight of the bike).
The most important part of your sag is that you maintain a BALANCE between the front and the rear. If you can not adjust the front sag (no preload adjustment) then your rear sag is dictated to a large degree by what your front sag is. The balance between the two determines the actual geometry of the bike when you are riding it, regardless of what the intended geometry of the bike is.
The other often mis-understood thing about sag is, unless you have a progressive spring, adding sag (removing preload) does not make a spring softer and reducing sag (adding preload) does not make a spring stiffer. The spring rate is what it is and sag is really setting the ride height.
As to what your actual numbers are, personally I shoot for around 25 - 30 mm of race sag (sag with the rider on board) and around 5 - 10 mm free sag (sag under just the weight of the bike).
The most important part of your sag is that you maintain a BALANCE between the front and the rear. If you can not adjust the front sag (no preload adjustment) then your rear sag is dictated to a large degree by what your front sag is. The balance between the two determines the actual geometry of the bike when you are riding it, regardless of what the intended geometry of the bike is.
The other often mis-understood thing about sag is, unless you have a progressive spring, adding sag (removing preload) does not make a spring softer and reducing sag (adding preload) does not make a spring stiffer. The spring rate is what it is and sag is really setting the ride height.
pokeyjoe
High Miler
Thanks for that - it helps. I'll measure my front sag and see if I can get the rear to match.
pokeyjoe
High Miler
Well, looks like I may need some help. The bike only drops 13mm when I sit on it. I'll have to get it up on a jack to check free sag.
Remember that you have to measure the suspension fully extended first, then base your measured sag from there.
Three measurements per end, fully extended, under its own weight, and with you on board. The use those three to calculate free sag and race sag.
Three measurements per end, fully extended, under its own weight, and with you on board. The use those three to calculate free sag and race sag.
oalvarez
Tuned and Synch'ed
pokeyjoe said:
Pokey, you should be able to check the unladen sag measurement by propping up the front then rear via the side stand. of course, you could use a jack if you don't feel comfortable doing it the way i suggest.
see ya,
pokeyjoe
High Miler
Well, thanks for that, but no one in that thread actually measures anything. They talk about their settings, but that's it. And a Griso weighs about 150 lbs. more than a V7. I'll try to measure my free sag this afternoon.Bill Hagan said:
Sorry if I am stating the obvious, but remember Free sag equals the fully extended length (measured with all the weight off the suspension, wheel in the air) minus the length under the weight of the bike. Race sag is the fully extended length mentioned above minus the length under the weight of both you and the bike.
Both key off the fully extended length.
Both key off the fully extended length.
pokeyjoe
High Miler
OK. "Race" sag was/is 43mm in front and 25mm in the rear. Since the rear shocks are adjustable, I managed to get that to 30mm, however I can turn the springs on the shocks with my hands under just the weight of the bike. It's easy. Is that OK? And I need stiffer springs for the front.
Roughly speaking, you should be at 1/3rd total travel... however travel is pretty limited on both ends, so take that with a grain.pokeyjoe said:
Factory specs:
Front total travel: 130mm/5.1 inches, so ideal @43mm/1.7"
Rear total travel: 118mm/4.6 inches, so ideal @39.33mm/1.53"
That said, the fork springs are certainly woefully inadequate and I'm betting the rear springs are as well.
Happy to get you some fork springs if you want.
I have always heard, and it seems to work for me, that your race sag should be around 25% to 30% of total travel. 1/3 is slightly above that but close enough.
As for whether you need stiffer springs, that is another story. To determine if you need stiffer (or softer) springs you need to measure both your free sag and race sag as mentioned already. Then once you have set your race sag and re-measured your free sag (or in the case of your externally non-adjustable forks calculate/extrapolate what it would be if you added the preload required) the differences between the two will tell you if your springs are too stiff, too soft, or just right. If you have the correct amount of race sag but too little free sag then your springs are too soft. If you have the correct amount of race sag but too much free sag then your springs are too stiff.
To extrapolate, just subtract the required amount of preload to get your race sag right to both the race sag measurement and to the free sag measurement. For example, your front race sag you said was 43mm. If your target measurement was 40mm you would need to add 3mm of preload to achieve that. Pretend you did. Now subtract the same 3mm from your free sag. If it is where you want it (usually about 10% of travel, some like more some like less) then your spring rate is good and all you need is to take the forks apart and actually add the preload. If it is too little or too much then your springs are too soft or too stiff as mentioned already.
Remember, if you change to progressive springs then it is a whole new can of worms and what I have said is no longer valid.
You need to calculate both free sag and race sag.
You should never have zero free sag.
As for whether you need stiffer springs, that is another story. To determine if you need stiffer (or softer) springs you need to measure both your free sag and race sag as mentioned already. Then once you have set your race sag and re-measured your free sag (or in the case of your externally non-adjustable forks calculate/extrapolate what it would be if you added the preload required) the differences between the two will tell you if your springs are too stiff, too soft, or just right. If you have the correct amount of race sag but too little free sag then your springs are too soft. If you have the correct amount of race sag but too much free sag then your springs are too stiff.
To extrapolate, just subtract the required amount of preload to get your race sag right to both the race sag measurement and to the free sag measurement. For example, your front race sag you said was 43mm. If your target measurement was 40mm you would need to add 3mm of preload to achieve that. Pretend you did. Now subtract the same 3mm from your free sag. If it is where you want it (usually about 10% of travel, some like more some like less) then your spring rate is good and all you need is to take the forks apart and actually add the preload. If it is too little or too much then your springs are too soft or too stiff as mentioned already.
Remember, if you change to progressive springs then it is a whole new can of worms and what I have said is no longer valid.
You need to calculate both free sag and race sag.
You should never have zero free sag.
pokeyjoe
High Miler
Just to give you the whole picture:
Front
Free sag - 30mm
Race sag - 43mm
Rear
Free sag - 10mm
Race sag - 30mm
If race sag should be 30% of total travel, what should free sag be? Any magic formulas there?
Thanks for all the good input, btw.
Front
Free sag - 30mm
Race sag - 43mm
Rear
Free sag - 10mm
Race sag - 30mm
If race sag should be 30% of total travel, what should free sag be? Any magic formulas there?
Thanks for all the good input, btw.
Street riders are often around 10%. I tend to be closer to 5% but I prefer more spring an less compression dampening.
As mentioned, higher equates to softer spring and less equates to stiffer spring.
As mentioned, higher equates to softer spring and less equates to stiffer spring.
oalvarez
Tuned and Synch'ed
GuzziMoto said:
i always have the most difficulty with the concept bolded/underlined above. the easiest way for me to understand it is to think of the bike being suspended in air.....if the rear spring (for example) is too soft, the measurement between the axle and let's say the rear tail light (unsprung) wouldn't change after being suspended in air....conversely, if the spring is too stiff, that distance would be much greater between those two points (think of the rear of the bike being lifted up on its own by the spring tension).
is that right GuzziMoto?
I don't know about the way you are understanding the concept, if it works for you great, go with it.
The way I remember it is this....
When you add or subtract preload it effects both the race sag ( with the rider on board ) as well as the free sag ( just the weight of the bike ). The relationship between the two is inverted, more preload equals less sag. If you have to add preload to get the race sag where you want it, say you add 5mm of preload to get the race sag from 40mm to 35mm ( this would be the front forks where there is a one to one ratio between preload and sag ). This 5mm of preload will not only reduce the race sag by 5mm but it will reduce the free sag by the same amount. so if you have to add a lot of preload to get the race sag where you want it because your spring(s) is/are too soft then that same preload will decrease your free sag beyond the target value. It could even reduce your free sag to zero which is, as mentioned, very bad.
The opposite is also true, if your spring(s) is/are too stiff then you will end up running very little preload, like the V7 in question, to obtain the desired amount of race sag. This minimal amount of preload, in addition to making the spring loose in the shock, will result in a high amount of free sag. More free sag then you should have when race sag is where it should be means your spring(s) is/are too stiff because you did not need to add enough preload to achieve the desired race sag. That resulted in too much free sag.
The way I remember it is this....
When you add or subtract preload it effects both the race sag ( with the rider on board ) as well as the free sag ( just the weight of the bike ). The relationship between the two is inverted, more preload equals less sag. If you have to add preload to get the race sag where you want it, say you add 5mm of preload to get the race sag from 40mm to 35mm ( this would be the front forks where there is a one to one ratio between preload and sag ). This 5mm of preload will not only reduce the race sag by 5mm but it will reduce the free sag by the same amount. so if you have to add a lot of preload to get the race sag where you want it because your spring(s) is/are too soft then that same preload will decrease your free sag beyond the target value. It could even reduce your free sag to zero which is, as mentioned, very bad.
The opposite is also true, if your spring(s) is/are too stiff then you will end up running very little preload, like the V7 in question, to obtain the desired amount of race sag. This minimal amount of preload, in addition to making the spring loose in the shock, will result in a high amount of free sag. More free sag then you should have when race sag is where it should be means your spring(s) is/are too stiff because you did not need to add enough preload to achieve the desired race sag. That resulted in too much free sag.
oalvarez
Tuned and Synch'ed
GuzziMoto said:
it's funny....i can easily grasp the "spring(s) is/are too soft concept but have more difficulty understanding the converse (above).....having a too stiff spring (no preload needed let's say) and also having too much free sag is less easy for me to understand.
thanks for taking the time to explain it to us.
pokeyjoe
High Miler
I got some springs from Todd and finally made new spacers last night. My new numbers:pokeyjoe said:
Free sag - 15mm
Race sag - 30mm
Nice difference on the ride in to work this morning. No more wallowing all over the place. Sweeping turns (freeway on/off ramps) felt much, much better. I still need to replace the oil with something a little thicker.