Suspension advice?

[bonio]

For the last couple of years, in the summer, I've noticed something wrong with the bike. Eventually I worked out that the rear shock was playing up. It only happens when I ride all day: it's always fine for the first hour or so, and then ok-ish but by afternoon, the rear of the bike is bouncing around and it won't keep on track when taking a bend. The next day it's fine. I think its worse in warm weather than when it's cold, but I don't ride this bike much in winter, so I can't be sure.

 

I had the rear shock replaced under warranty, and at first it seemed to be fine, but when the first opportunity came to ride all day, the same thing happened. I've adjusted the damping - tweaked it up a smidgen - which has improved things a bit (and any more made it worse) but I still the problem that the suspension gets worse over a long ride. When this happens, I've found I can set things right again by adding more preload during the day, and then it will ride well for another hour before it goes off again.

 

I haven't a clue what's happening. Anyone any ideas? Any ideas on how to fix it?

 

I've got the bike booked into a suspension shop for a set up; if then it still won't ride properly, I am going to take it back to the dealers. 

 

This is on the MV. It comes fitted with a reasonable-quality Sachs shock. It should give a good ride without needing an upgrade. When all is well, the suspension is the best I've ever had on any bike - even the GS with its electronic gizmos. It's just that it won't stay that way all day.

Edited July 21, 2024 by bonio

[husoi]

Sounds like the oil had it's days.

As it heats up becomes more fluid.

It could also be the bushes (if there are some) are in need of replacing.

A softer suspension means less compression inside the absorber.

[Simon Davey]

Following with interest. 

[Gerontious]

when the suspension gets tired on my bike it will be replaced. Personally I set little store on OEM suspension and would rather go for a specialist that's built for my weight and other specs and is fully rebuildable going forward. This isn't a big deal for me as I intend keeping the bike. if you're not then maybe its time to trade it in. if its easily rebuildable then all well and good. but often with OEM this isn't possible. for example some need actual surgery to force rebuild - ability. Like having a valve brazed on. They are sometimes sealed units as standard from the factory - I mean. built to meet a specification set out by the manufacturer.. but also within a strict budget with little thought given to longevity and future serviceability.

 

Which is why there is such a wide market for direct OEM replacements.

Edited July 21, 2024 by Gerontious

[Tinkicker]

The shock is overheating.  Technical term is damper fade...

 

When it goes, I bet it is too hot to touch.  Probably does not happen in the rain.

Edited July 21, 2024 by Tinkicker

[bonio]

Yeah, I've wondered if the shock is overheating and the oil is running thin. I've only ever noticed it get warm, not too hot to touch. Will check again next time I go for a longer ride.

 

 

[bonio]

6 hours ago, Gerontious said:

when the suspension gets tired on my bike it will be replaced. Personally I set little store on OEM suspension and would rather go for a specialist that's built for my weight and other specs and is fully rebuildable going forward. This isn't a big deal for me as I intend keeping the bike. if you're not then maybe its time to trade it in. if its easily rebuildable then all well and good. but often with OEM this isn't possible. for example some need actual surgery to force rebuild - ability. Like having a valve brazed on. They are sometimes sealed units as standard from the factory - I mean. built to meet a specification set out by the manufacturer.. but also within a strict budget with little thought given to longevity and future serviceability.

 

Which is why there is such a wide market for direct OEM replacements.

I upgraded the suspensions on the Tiger, and it transformed the bike. Turned out to be a bad decision, as when I got nicked a few months later, that money just disappeared with the bike. I'd been hoping to avoid doing this with the MV. But perhaps I'll have to bite the bullet. Odd thing was, the suspension used to be top notch; the Tiger's was always on the mediocre to shite spectrum.

[bonio]

6 hours ago, Tinkicker said:

Technical term is damper fade...

Thanks; it's useful to know how to explain things to people.

[Old-codger]

This company isnt far from you Motorbike suspension, Motorcycle Suspension | MCT suspension | Stowmarket

My brother had his ducati shock rebuilt to his requirments ( cant remember if it was showa or Ohlins) by this company and said it was a terrific job.

[bonio]

Cheers @Old-codger. I've already got the bike booked in there for a set up.

If Darren can't set it up right, no-one can. He's a bit of a local legend.

[RideWithStyles]

Fade is one but the real cause of fade might be because there is no actual control of the flow so it builds up friction as it bounces too much, so heat, so fade.
If the rebound (check compression too) is at 2 clicks out from fully closed (righty righty) try one or even half out, if its almost close /shut it seriously needs service and a better / thicker oil or a re valve or worst case a new aftermarket.

if the preload to too low that will work the spring and the oil big time too, which as you said improved it for a short time but preload doesnt work like you think or might not actually solve it depending on what setting you have it at now and what it actually is doing as people interpret the same thing differently. All the preload main job is keep the springs starting point within a space of its travel allowance- in a basic form for you to understand.

so if you have a ramp preload at 4 of 8, when u sit on the bike it sits/sags 60mm, from its unladen, it’s too low (unless you have a trail or enduro with super long suspension) so you’ll need to take it up a notch for two, you wanna aim for 40mm. Then see what the rebound and comps are at, when cold and you push hard down on the rear of the bike is it slow to return? Like soft foam? Or fast like it pushing as fast or faster than you gave it? If it’s pushing or bouncing then it’s too fast so slow the reboundown by turning it in abit till it doesn’t.
Go for a ride to get it hot and do the same again, doe it return really fast almost like it’s pushing your hand back, then the oil is very goosed and requires a service and better or thicker oil.
 

Sach ain’t bad really, which mv bike is it? 

Edited July 21, 2024 by RideWithStyles

[bonio]

@RideWithStyles Turismo 800.

[RideWithStyles]

Cool, a few pics of your rear tyre will confirm of this problem. Ones like these.

[bonio]

Here you are mate

 

[RideWithStyles]

Most of the time Old cold oil is gives the impression of firm or thicker at first (because the molecules that keep it flowing have broken up but fill the volume) but very quickly turns thinner than new oil at the same moment as the same stuff gets broken down more so can’t control.

Even if it’s warm ambient air temp, is still different to shock heated up in use temp so if its doing it now (not controlling the flow) it’s going to be even more apparent to the point you’ll either got to compromise of having it closed up from cold so it will be hard until it gets warmed up or you have to change it mid ride.

 

Active, semi , manual adjustable including preload on this bike?

Was all the pics after your last ride with after tweeks you did, if so what? And how many miles On these adjustments? how many miles has the tyres done now?

 

In the pics the pressure isnt too low, what you been running it at?
rebound isn’t terrible not the worst I’ve seen but supple as in no2, these design of Pirelli are good at hiding the problem so best way to feel the tyre.

Palm on the centre tread and fingers down the sides, while gently touching rub along the circumference of the tyre.if you go rear (back of the wheel) to front and feel your palm and fingers drop as it goes between onto the next flat section that if so is lower down (pic 1 give a clue) then rub the other way back front to rear and if your hand and fingers catches the ridges which is where the (following part is taller) on the way back the rebound is definitely fast, if you see lips on the back of the tread it’s FAR too fast and excess wear is happening.

Your riding habit is good.

Another thing to note coasting (mid corner) can give lips on the tread 
On the front tyre it’s the reverse. 

Edited July 22, 2024 by RideWithStyles

[bonio]

Thanks for this @RideWithStyles 

Suspension is 100% manual.

The pics were today, so with and without tweaks. The tyres have done about 3000 miles now; not much more than a couple of hundred miles on the latest settings. 

Pressures are 36 psi all round. Book says 38, but I'm only 130 lbs, so I've running them slightly under for the last 1000 miles or so.

I'll take a feel round the tyre like you say. I don't coast round corners, so no confusion there. Will take a few days though as I'm off up to bonnie Scotland for my sister-in-law's funeral. Day up, day there, day back. Three day event.

[bonio]

I wonder if the GT II is too strong a tyre for a bike that's only 191kg dry? I got it initially because TV owners recommend it, and I like the way it rides so this is now the second set I've had.

[RideWithStyles]

Yea the tyre says your riding habit is good and confirms little if no coast.

 

pirelli is a soft to medium strength carcass not a hard one like Dunlops or Bridgestones, the only thing softer is Michelin.

gt2 is a good all round tyre for any type- available on small to cruises if your thinking of is it too strong - it’s not,

this is a CTangel which is a smaller tyre for smaller bikes and “lighter” riders but it’s small granddad which can have the same problem.

 

will be down to five things- size, loading rating, carcass, compound and tread design. This tyres only mildly firm part is tread and most are long lengths which are inherently weak or puckered naturally unlike road 5 and 6s which are stronger.

Id go with the book setting on the rear for now and see if that improves things. if the tyre is getting hot (slightly down on pressure) it will pop or reflex more (feeling like bouncing) as it’s getting hotter? Hence check with your hand. 

 

thing for you to think about is a few things, 1 if This is the factory tyre the book is referred to for its pressure. Nice it says 38front and rear, but for that is the assumption/recommended for who or why? was the test rider lighter or heavier than you? Riding in faster scenery or slow twin stuff? Was that tested in hotter conditions? With or without luggage or pillion? So the book is a guide but really it’s not applicable for everyone. 
 

Edited July 22, 2024 by RideWithStyles