Suspension sag on 2016 bike - these look weird

[Mike5100 2,061]

Please note these measurements relate to the latest model 2016 NC750X which has the new Showa dual bending valve forks and a pre-load adjustable rear shock.

 

Spent some time with an assistant today and read several websites describing how to measure the front and rear sag settings taking into account stiction.  I am 82kg and put an 8kg weight in the not tank to allow for my normal riding gear.

Front dynamic (rider)  sag is 71mm measured along the fork stanchion.  Maximum travel according to the workshop manual is 137mm (but it's possible that it is 152mm).  Either way, that amount of rider sag seems way too high.

 

Rear rider sag with preload on the 3rd notch up is 54mm (total possible travel according to the manual is 150mm).  This seems OK-ish.

 

However I get a MUCH improved ride if I wind the preload up to maximum.  Under those conditions the rider sag is reduced to 33mm.

 

 

(For those still reading this, the front static sag was 57mm and the rear 24mm (which dropped to 4mm when I wound up the preload to max)

 

 

Mike

[larryblag 14,236]

Hang on Mike - still reading...

[Guest Mac750]

I dunno , I have lots of sag, it's an age thing.

I put my rear suspension on the softest setting and now the bike feels ansome and a lot better through the bends, but on the default setting my eyes rattled every time I hit a bump and the seat felt like it was thumping my kidneys.

[Guest Hati]

Ballpark for sag is up to 30% rear and up to 25% front for street use, 10% less for track work. This is percentage of your total travel available. Many sites just declare a millimetre value, usually 25 to 30, which may or may not work as suspension travel is different for most bikes.

 

It sounds like you definitely need some more preload up front. More then 50% sag is just wrong. Extra spacers in the tubes perhaps?

 

Preload just moves the working range of the suspension into the (hopefully) correct range, so it doesn't top out or bottom out under the usual load. If you can't get that right, you may need to look at replacing the springs.

[Mike5100 2,061]

Ballpark for sag is up to 30% rear and up to 25% front for street use, 10% less for track work. This is percentage of your total travel available. Many sites just declare a millimetre value, usually 25 to 30, which may or may not work as suspension travel is different for most bikes.

 

It sounds like you definitely need some more preload up front. More then 50% sag is just wrong. Extra spacers in the tubes perhaps?

 

Preload just moves the working range of the suspension into the (hopefully) correct range, so it doesn't top out or bottom out under the usual load. If you can't get that right, you may need to look at replacing the springs.

Suspension front and rear is being replaced tomorrow Hati.

The huge amount of rider sag on the front makes me wonder if the spring is compressing so far that it's operating predominantly in the 'progressive' zone - ie the tightly wound section in the lower half of the spring? (and hence giving a harsh and jittery ride)

Also - is it possible that by jacking up the rear I am putting the front springs more into their working range - which is why I'm getting an improved ride with the rear pre-load on setting 7?

Mike

[Tex 36,817]

Be sure to tell us all about your fancy new suspenders, Mike.. 

[Guest Hati]

The huge amount of rider sag on the front makes me wonder if the spring is compressing so far that it's operating predominantly in the 'progressive' zone - ie the tightly wound section in the lower half of the spring? (and hence giving a harsh and jittery ride)

 

 

I think it is possible, but without measuring the spring on its own, can only be a guess. I am not a big fan of progressive springs. My Matris cartridges came with linear springs and I am very happy with them. What surprises me is that the factory springs are so weak that they give the bike with just the rider (assuming it is just you) such a huge sag.

 

Also - is it possible that by jacking up the rear I am putting the front springs more into their working range - which is why I'm getting an improved ride with the rear pre-load on setting 7?

 

You would really have to pay attention to each end on its own and try to work out if just the rear improved or both. If it's both, you effectively added some preload to the front too, but I suspect it's just a rear.

[SteveThackery 3,090]

I dunno , I have lots of sag, it's an age thing.

I put my rear suspension on the softest setting and now the bike feels ansome and a lot better through the bends, but on the default setting my eyes rattled every time I hit a bump and the seat felt like it was thumping my kidneys.

 

The rear suspension doesn't have a "softest" setting.  By raising or lowering the bottom of the spring, all you are doing is raising or lowering the top of the spring when you are sat on it.  In other words, you are adjusting the ride height.  It has a "lowest" setting and a "highest", not softest and hardest.

 

There is nothing in raising or lowering the ride height that can affect the harshness of the ride, UNLESS the suspension is actually bottoming or topping out at the extremes of adjustment, and that is most unlikely.  

 

A softer ride can only be achieved by fitting a softer spring, not by raising or lowering the existing spring.  

[Mike5100 2,061]

The rear suspension doesn't have a "softest" setting. By raising or lowering the bottom of the spring, all you are doing is raising or lowering the top of the spring when you are sat on it. In other words, you are adjusting the ride height. It has a "lowest" setting and a "highest", not softest and hardest.

There is nothing in raising or lowering the ride height that can affect the harshness of the ride, UNLESS the suspension is actually bottoming or topping out at the extremes of adjustment, and that is most unlikely.

A softer ride can only be achieved by fitting a softer spring, not by raising or lowering the existing spring.

I wondered whether raising the ride height only at the back changed the distribution of load so that more weight is now applied to the forks?

Mike

[Guest Mac750]

It's all above me, all I know is my shock was set at the third setting and it rattled my eyes out over every bump and road undulation. So I changed the spring setting to the lowest setting and now the bike floats over bumps and undulations, it feels like it has more bite coming out of corners and is a whole lot softer on my backside. It's a new bike so the rear shock absorber is not yet worn or tired and is working as it was designed to do. So the argument that adjusting the shock spring length will not make the ride softer my be correct but I definitely feel the difference, the ride is a lot better.

[Mike5100 2,061]

It's all above me, all I know is my shock was set at the third setting and it rattled my eyes out over every bump and road undulation. So I changed the spring setting to the lowest setting and now the bike floats over bumps and undulations, it feels like it has more bite coming out of corners and is a whole lot softer on my backside. It's a new bike so the rear shock absorber is not yet worn or tired and is working as it was designed to do. So the argument that adjusting the shock spring length will not make the ride softer my be correct but I definitely feel the difference, the ride is a lot better.

Well either neither of us know what we are doing Mac, or one of us has a faulty rear shock, because my experience is the opposite of yours - if I wind the preload to maximum (the opposite of what you have done), I get a much smoother softer ride.

And in Mac's defence .... surely getting the pre-load adjusted correctly makes the spring work in its proper range so it helps stop it topping out or bottoming out - either of those two occurrences would surely make the ride 'harder' (or certainly more unpleasant), so in that sense doesn't correct pre-load adjustment make the ride 'softer'?

Mike

[trisaki 2,029]

I use 30 mm front and 15 mm rear static sag on my bike rides lovely

[embee 7,288]

.... surely getting the pre-load adjusted correctly makes the spring work in its proper range so it helps stop it topping out or bottoming out - either of those two occurrences would surely make the ride 'harder' (or certainly more unpleasant), so in that sense doesn't correct pre-load adjustment make the ride 'softer'?

Mike

As Steve says, the spring itself is a constant item, adjusting anything doesn't change the spring characteristics. It will sit at whatever length matches the load it has to carry. Adjusting the preload setting on the shock simply alters the length between the mounting points on the shock at which the spring reaches the load required. My measurement of the Integra 700 spring shows it is perfectly linear, there is no rising rate section. The 750 springs look to be the same from pics (equally wound coils).

 

However the shock can top out if the preload is too high because it has a fixed maximum length, or can bottom out if preload is too low. I don't know if the shock has varying characteristics through its stroke, it's possible.

 

It has a rubber bump stop fitted round the shaft which starts to compress when the shock nears full compression, it starts around 2/3 or 3/4 of the full travel. The shape of the rubber (cone like) makes it a very steeply rising rate, if you ride with the suspension reaching the bump stop regularly it will feel harsh. Similarly if it is regularly topping out it will feel unpleasant and it will also seriously compromise the tyre grip.

 

As std a bike will have a compromise spring, a guess at what most folk will find acceptable depending on the weight carried. I must admit I'm a bit confused by Honda's philosophy on NC suspension specs.

[Mike5100 2,061]

So the new suspension is fitted front and back (wilbers 641 and Racetech gold valve emulators with K-tech linear springs)).

Rider sag is now 35mm at the front and 55mm at the rear   (previously 71mm and 54mm with Honda OEM suspension).

The bike sits higher - well it's an inch and a half higher at the front.

But despite the £1000 spend it hasn't achieved what I hoped for.  I will post further thoughts in the other thread.

Mike

[Guest Hati]

You may just need to spend the money with a suspension specialist to set you up properly. Like Murray said elsewhere, there is a lot of fiddling involved and it has to be consistent too otherwise you won't get anywhere. I'm in similar shoes as you, insofar as I just changed to the best available Matris setup that consists of F15K cartridges and  M46KF shock, replacing the rubbish Hyperpro streetbox kit. I am now balancing my expectations against the reality of motorcycle suspension with a lot of methodical setup work, research and collaboration with the suspension shop I got it all from. If you don't want to get your head around the theory of it, it's probably best to get the shop to set it up for you.

[Mike5100 2,061]

You may just need to spend the money with a suspension specialist to set you up properly. Like Murray said elsewhere, there is a lot of fiddling involved and it has to be consistent too otherwise you won't get anywhere. I'm in similar shoes as you, insofar as I just changed to the best available Matris setup that consists of F15K cartridges and  M46KF shock, replacing the rubbish Hyperpro streetbox kit. I am now balancing my expectations against the reality of motorcycle suspension with a lot of methodical setup work, research and collaboration with the suspension shop I got it all from. If you don't want to get your head around the theory of it, it's probably best to get the shop to set it up for you.

I have paid the suspension shop to install and set it up for me Hati.  They may be expecting me to return to get it tweaked so I will contact them tomorrow to ask.

Mike

[Guest Hati]

They may be expecting me to return to get it tweaked so I will contact them tomorrow to ask.

 

 I am sure they are. The one constant I found during my research into suspension was that it's subjective. People feel things differently so no two "perfect" setups are the same. It's quite normal, don't be disheartened by the difficulty of it

[embee 7,288]

Indeed it is subjective, and there is also a language aspect, exactly what do you mean by plush, or knobbly, or soggy, or harsh?

 

I think as Mike has suggested in his other thread, the folk doing the work for him may well be race/track oriented, and what he means by comfort they would think was wallowy. Plush is what you're after.

 

I think the most common error is to start with damper setting way too hard, possibly in the belief that it improves handling, but it doesn't really and just makes it nasty to live with. At least the expensive items have adjusters so damping can be tweaked easily, just keep a note of what you've done so you can see the trend and where you want to be.

[Mike5100 2,061]

Yes -that language thing.  I described the new showa suspension on the 2016 as jittery and jiggly but I haven't seen other people use those terms - especially not suspension specialists or suspension websites.

Mind you I now think I know what feeling the front suspension 'wanting to fold' means.  Twice on the ride back when I went over catseyes as I was slightly banked over I got a weird sensation and I was wondering how to describe it to the specialist - then that term that I have seen in motorcycle journalist reports suddenly came into my mind.  And I then began to wonder if, with it now riding 36mm higher at the front than it was (but the same as it was at the back), has it shifted the load distribution.  However, I have to bear in mind that I have a habit of adding 2 and 2 and making 5.

Mike

[Guest Mac750]

Hi Mike,

I noted my Honda 2016 stock set up was jittery also, so backed it off from Three to One on the rear end and it was comfortable and smooth. However yesterday I went through an empty roundabout junction which has a noteable dip in the middle ( floods in winter) and the rear end bottomed out so I may tweek it up one. All this is subjective, I had an MZ which had two settings pillion and not pillion it took me thousands of miles and was fine.

My K750s on the other hand was pants until I threw the rear shock away and bought a KSS ( something like that ) and transformed the bike.

From your description it sounds like you have a perminant fat pillion or loads of luggage on, The front end is high and with you sat on it the rear end is lower.

This will make the front end feel light or vague yes ? you could try dropping the front forks through the yokes a little? .

This will make the steering a little sharper. I have noticed the 750x is slow to turn in and needs a good hint at what you want it to do, but given its design that's not a surprise. Dropping the forks through slightly may work. You can always put them back to stock again. I have had some real rusty nails in the past and so the suspension has to be falling off before I notice it much, so any suggestion is given with good intentions but little practical knowledge

[Mike5100 2,061]

The rear suspension doesn't have a "softest" setting.  By raising or lowering the bottom of the spring, all you are doing is raising or lowering the top of the spring when you are sat on it.  In other words, you are adjusting the ride height.  It has a "lowest" setting and a "highest", not softest and hardest.

 

There is nothing in raising or lowering the ride height that can affect the harshness of the ride, UNLESS the suspension is actually bottoming or topping out at the extremes of adjustment, and that is most unlikely.  

 

A softer ride can only be achieved by fitting a softer spring, not by raising or lowering the existing spring.  

This isn't aimed at you Steve as there are plenty of other posters on here who bash anyone round the head who suggest that altering pre-load affects softness of ride.  But I found it interesting tonight that I have found two specialist suspension websites at least who fall into the same trap (if that's what it is).

Here's a quote from Hagon's site:

"Hagon Twin Shocks with 3 position preload adjusters are supplied set at their softest setting"

and

Turn the HYDRAULIC PUMP HANDLE clockwise to increase the spring pre-load for heavier riders or luggage.

Turn clockwise to harden and anti-clockwise to soften the ride."

 

and here are the guys from Progressive Suspension in a video (at about 45 seconds in) saying that they like to run softer or firmer preload 

https://www.youtube.com/watch?v=2DO-qJj95tE

Mike

[djsb 492]

I'm still about a quarter of the way through Race techs motorcycle suspension bible by Thede and Parks and it's a good read. I'm still trying to understand it all even though I have a background in engineering.

[Guest phantom309]

well on my 700x i was happy with the handling, didn't adjust it at all even with pillion...most bikes / scooters i have i normally just stiffen the rear shock up one possition from stock.. the burgman 650 i have now i have done this to, it was bit harsh two up on standard,  an it rides so much smoother when you hit bumps an holds the road very nicely ..

[Mike5100 2,061]

So I have 54mm of rider sag at the back (and this equates to about 34% of travel (as per Honda manual) and I only have 35mm of rider sag at the front (25% of supposed travel but my guess is that the actual cushion stroke travel is 150mm rather than 137m and it's really only 23% of travel.

Question is - will it work like this.

To my uneducated mind it's going to mean the front riding quite a bit higher than was intended.  In order to increase rider sag at the front I guess I would need to get smaller preload spacers made and strip the forks.

It would be easier to jack up the back until I got to somewhere similar.  Would that be a sensible thing to do?

Mike

[Guest Hati]

Yes, it will work and yes either front or back solution you spoke of will work too. You would want to match the front and back as close as practicable to keep the intended "angle of attack". Unless you go racing, it will not effect the handling a great deal.