Rider and static sag?

[Maha]

Bike is currently at Factory settings and is fine with me at 88kgs.

Rear
Unloaded = 355mm
Loaded = 340mm
Rider/Gear = 312mm
Rider Sag = 43mm/Static Sag = 15mm

Front
Unloaded = 495mm
Loaded = 460mm
Rider/Gear = 450mm
Rider Sag = 45mm/Static Sag = 35mm


In a few weeks I will increase the normal weight by about 85-90kgs (for a weekend) by adding a pillion and full panniers/Top box (may not need the top box)
Question: Any idea on preload front and rear adjustment, to accommodate the extra weight?

[kinger]

I just wind the rear preload and ride a bit more conservatively.
It's worked fine for years, including across the Canadian prairies and through the Rockies.
You'd do well to set your suspension to suit yourself first. You've not measured the full travel figures, easily done with tyraps on fork legs and pistons.
Don't forget to lower headlight beam when pillioned up.

[Robert Taylor]

Bike is currently at Factory settings and is fine with me at 88kgs.

Rear
Unloaded = 355mm
Loaded = 340mm
Rider/Gear = 312mm
Rider Sag = 43mm/Static Sag = 15mm

Front
Unloaded = 495mm
Loaded = 460mm
Rider/Gear = 450mm
Rider Sag = 45mm/Static Sag = 35mm


In a few weeks I will increase the normal weight by about 85-90kgs (for a weekend) by adding a pillion and full panniers/Top box (may not need the top box)
Question: Any idea on preload front and rear adjustment, to accommodate the extra weight?

The bike is a GSX1250? Unloaded figures are ''wheel in air'', fully extended?

[Maha]

The bike is a GSX1250? Unloaded figures are ''wheel in air'', fully extended?

Correct, bike was on the centre stand.

[Robert Taylor]

Correct, bike was on the centre stand.

Ok, excellent. Rider sag figures you are looking for with a road going bike are around 36-42 rear and 35 -45 front. We always set rider sag first and foremost and then measure ''resultant'' free sag afterwards. That resultant figure is indicative of whether the spring rate is ''in the zone. Don't regard the suggested figures as absolute gospel, its what works for you that really counts.
If you have a setup that works really well for you solo then get the feel for how much bend there is in your knees when you are sitting on the bike feet on ground on a flat surface. When you add a passenger and extra baggage etc readjust preload so that when you are all sitting on the bike the bend in your knees is exactly the same. You are then merely restoring static loaded ride height to the same as solo. No need for laborious re-measuring!

[Robert Taylor]

Correct, bike was on the centre stand.

Suffice to say also ( irrespective that I sell suspension! ) that the tiny rear shock on that bike is going to struggle with all that extra load you have rattled off

[Maha]

Ok, excellent. Rider sag figures you are looking for with a road going bike are around 36-42 rear and 35 -45 front. We always set rider sag first and foremost and then measure ''resultant'' free sag afterwards. That resultant figure is indicative of whether the spring rate is ''in the zone. Don't regard the suggested figures as absolute gospel, its what works for you that really counts.
If you have a setup that works really well for you solo then get the feel for how much bend there is in your knees when you are sitting on the bike feet on ground on a flat surface. When you add a passenger and extra baggage etc readjust preload so that when you are all sitting on the bike the bend in your knees is exactly the same. You are then merely restoring static loaded ride height to the same as solo. No need for laborious re-measuring!

Brilliant, thank you for that Robert.


Suffice to say also ( irrespective that I sell suspension! ) that the tiny rear shock on that bike is going to struggle with all that extra load you have rattled off

Went for a full days ride two-up not so long ago, seemed to handle things fine, I must admit though, not with the panniers/top box. I will increase the rear preload a click, current measurement is just on, or a tad firm it would seem?

[nzspokes]

Just for giggles I checked my fork sag today, static 15mm and rider sag 35mm.

Yup bored at lunch time.

[LankyBastard]

Just for reference, i'll be in the same boat with Becca on the back, and i'll have my rear preload at max. And even then the tiger's handling can be best described as boat like :(

Good thing Robert is going to sort me out in early September, cant wait!!

[Gremlin]

Just for reference, i'll be in the same boat with Becca on the back, and i'll have my rear preload at max. And even then the tiger's handling can be best described as boat like :(

Good thing Robert is going to sort me out in early September, cant wait!!
Get a BMW... push a button, suspension adjustments made :bleh:

[Robert Taylor]

Just for giggles I checked my fork sag today, static 15mm and rider sag 35mm.

Yup bored at lunch time.

Those in theory are not good figures. If you reset your front rider sag to say 40-45mm range it would be interesting to see what your ''resultant'' free sag is. It depends of course on the bike but very often riders will set the front sag ''tight'' to try and minimise an initial tendency for the front end to drop through its stroke. Very often the issue is poor spring rate choice or the low speed compression damping control is very weak.

[Robert Taylor]

Get a BMW... push a button, suspension adjustments made :bleh:

How is the Ohlins mechatronic suspension working for you?

[nzspokes]

Those in theory are not good figures. If you reset your front rider sag to say 40-45mm range it would be interesting to see what your ''resultant'' free sag is. It depends of course on the bike but very often riders will set the front sag ''tight'' to try and minimise an initial tendency for the front end to drop through its stroke. Very often the issue is poor spring rate choice or the low speed compression damping control is very weak.

Well its adjusted half way through its preload so I can adjust the preload off a bit and check both sags. What should the free sag be?

[LankyBastard]

Get a BMW... push a button, suspension adjustments made :bleh:

I nearly did, took the latest water cooled GS out and thought it was brilliant. The only issue was the $18k needed to trade up :weep:

New suspension for the Tiger is waaaaaay cheaper :drool:

[nzspokes]

Those in theory are not good figures. If you reset your front rider sag to say 40-45mm range it would be interesting to see what your ''resultant'' free sag is. It depends of course on the bike but very often riders will set the front sag ''tight'' to try and minimise an initial tendency for the front end to drop through its stroke. Very often the issue is poor spring rate choice or the low speed compression damping control is very weak.

Adjusters all the way out result in 36mm sag and 18mm free.

[Gremlin]

How is the Ohlins mechatronic suspension working for you?
Perfick. Read about some issues guys are having in the USA, Ohlins recalled the product and stuff, but bar that initial issue, where I had to re-plug the OEM gear, it hasn't missed a beat. I've done about 18,000km since we fitted it, 1 up, 2 up, with or without luggage and loving having good suspension while keeping the riding modes. Even had a technicial official comment about how well the bike handled during one event, when we were doing a final check before opening the roads and doing up to 100kph in 50kph residential areas.

I would have done more kilometres if it wasn't for Felix (that you know) bloody riding on the other side of the world and leaving me to do all the work. :oi-grr:

[Robert Taylor]

Well its adjusted half way through its preload so I can adjust the preload off a bit and check both sags. What should the free sag be?

25-30mm range. BUT, this assumes that the low speed damping is up to the task in providing at least adequate dynamic ride height control. If the fork works ''better'' with a lesser figure it arguably proves that you are adding more spring preload as a ''fudge'' to compensate for a damping issue. As with anything there are so many variables

[Robert Taylor]

Perfick. Read about some issues guys are having in the USA, Ohlins recalled the product and stuff, but bar that initial issue, where I had to re-plug the OEM gear, it hasn't missed a beat. I've done about 18,000km since we fitted it, 1 up, 2 up, with or without luggage and loving having good suspension while keeping the riding modes. Even had a technicial official comment about how well the bike handled during one event, when we were doing a final check before opening the roads and doing up to 100kph in 50kph residential areas.

I would have done more kilometres if it wasn't for Felix (that you know) bloody riding on the other side of the world and leaving me to do all the work. :oi-grr:

Great news! If there ever are any issues / minor niggles etc please don't hesitate to let me know

[nzspokes]

25-30mm range. BUT, this assumes that the low speed damping is up to the task in providing at least adequate dynamic ride height control. If the fork works ''better'' with a lesser figure it arguably proves that you are adding more spring preload as a ''fudge'' to compensate for a damping issue. As with anything there are so many variables

Cheers. Its close enough for me. It will change anyway when I put a stronger spring in the back.

[sinfull]

Cheers. Its close enough for me. It will change anyway when I put a stronger spring in the back.

I do like this topic of conversation ! The science of tyres and suspension intrigues me, of course just having classics and an old evo massey ferguson now, with no clickers etc, makes it very interesting getting things right lol
After having some RT fettling of the masseys bottom and playing with emulators up front i probably have (arguably) one of the better handling masseys in the group !

[Maha]

Suffice to say also ( irrespective that I sell suspension! ) that the tiny rear shock on that bike is going to struggle with all that extra load you have rattled off

You may have a point Robert, I can reach the rear shock with the C spanner at a stretch, but it leaves no room for preload adjustment of said shock. Conclusion is, the rear shock is set at (and will stay at) the factory setting.
We had a reasonably horror time on the road in cold wet conditions yesterday loaded and two up, one major slip and about 5 tweaks, one small slip on Saturday in dry/cold conditions. I am changing the tyres that were put on in March and reverting back to PR3's. The reason I say this is because, I have loaded a CB1300 up with a double pack/two tank bags and two-up riding for a week, one day in cold bleak conditions and not once the bike give me cause for concern.

It's my opinion (after thinking on it) that the suspension possibly played a part in the weekends mishaps, but the tyres should have acted way better than they did. The two components have to work well together.

[Robert Taylor]

You may have a point Robert, I can reach the rear shock with the C spanner at a stretch, but it leaves no room for preload adjustment of said shock. Conclusion is, the rear shock is set at (and will stay at) the factory setting.
We had a reasonably horror time on the road in cold wet conditions yesterday loaded and two up, one major slip and about 5 tweaks, one small slip on Saturday in dry/cold conditions. I am changing the tyres that were put on in March and reverting back to PR3's. The reason I say this is because, I have loaded a CB1300 up with a double pack/two tank bags and two-up riding for a week, one day in cold bleak conditions and not once the bike give me cause for concern.

It's my opinion (after thinking on it) that the suspension possibly played a part in the weekends mishaps, but the tyres should have acted way better than they did. The two components have to work well together.

Yes of course access is a big issue with many suspension units, and so often they are left well alone if only to avoid skinning ones knuckles!!!! And it cannot be underestimated just how important careful selection of those black round things is.

The problem is that if you don't adjust spring preload ( and often spring choice rate ) for two up riding with a lot of luggage displaced rearwards there are two real negatives that happen. 1) Because the bike is now riding so low in the rear it ''lazes out'' the steering geometry and takes weight off the front. This destroys contact feel in the front end ( the front end no longer ''talks'' to the rider ) and you also lose mechanical grip. not so good on damp roads. 2) Especially if the rear end has a reasonably progressive linkage it means that straight away at static fully loaded ride height the rear end is already sitting at the more accelerative / aggressive part of the link curve ratio. That means a harsh ride and the passenger will not thank you for that! As a link gets deeper into its stroke it moves the shock shaft further and therefore faster for any given unit distance movement of rear axle movement. As damping is velocity dependent it means that you end up with more damping than you need.

So, if nothing else springing the bike firmer ( a stronger spring ) for such loading scenarios will actually make it both more compliant ( because at ride height it will be working in the more supple part of link movement ) and give it the bottom out / ''g'' out resistance it would otherwise lack. A firmer rate spring correctly chosen will require a lot less preload than a soft spring. This shows quite clearly on a spring force curve graph, mapping spring rate against spring preload. Less initial force but more end force


As a short cut to the laborious / tedious act of measuring sag ( requiring at least 3 people to do so properly) we suggest that the rider gets a feel for how much bend there is in his / her knees when sitting on the bike solo on a flat surface, both feet on the ground ( with usual riding footwear on ) You merely have to achieve that same degree of bend in your knees when you add passenger and all your worldly goods! So you are maintaining exactly the same static ride height.

There is always a common misconception that if you add spring preload or a firmer spring to restore ride height with a passenger and baggage that you also have to slow down the rebound to compensate. Consider though that because you are adding weight to the back of the bike there is more weight resisting return to static ride height. So, to a degree it all compensates.