Suspension Overhaul - now feels worse!

[Jamieboy]

Hi Folks,

1150 GS Adv. I fairly recently sent OE front and rear shocks to a well known suspension outfit to be rebuilt. Rear feels much nicer, smoother and more plush - very pleased with that.

However, the front feels (to me) worse than it did before. I'm not au fait with suspension terminology - but my feeling is that it could be over-damped...? Seems not to have enough 'give' for lower forces - i.e. tiny road imperfections - so you feel these as knocks/judders through the handlebars quite a bit. Most noticeable when on a closed throttle and the bike is engine-breaking.

It feels ok over speed bumps and larger ripples, and under breaking (presumably all situations when there is higher force going through the shock) - it is just extremely sensitive to what must be tiny imperfections on what looks to the eye like a decent enough road surface. Basically means that I feel no confidence in the front as I don't have 'feel' (although I'm not exactly Rossi).

My mate thinks that I'm just being over sensitive and I was just used to the sloppyness of the shock as it was - but I'm not so sure. I've noticed great improvement in the rear after all.

I really have at best a loose hold on the concept of how the shock would have been overhauled - do people who know more think it is possible that it could have been put back together wrong, causing something like this?

Alternatively - can anyone suggest anything else which it might be? (I had the ball joint replaced in the meantime, thinking that could be it - to no avail).

Thanks all.

 

[Comfy Old Boots]

Well firstly, good to hear there is an improvement in the rear. I'm seriously considering getting mine done.

With regard to the front, how much preload have you got on it? Perhaps reduce the preload and see what happens?

 

[Jamieboy]

Thanks for the thought Boots. It's on the second lowest preload setting (as it was for the last 5 years). I did try reducing to lowest setting but the issue seemsed to still remain, plus steering was more vague so I put it back.

 

[Comfy Old Boots]

I'd contact the company who refurbed it and have a chat. They would be the best people to help you with this...

 

[monkeyboy]

The shock has probably been buggered for a while and now it's as it should be. What are your tyre pressures? Have you considered dropping the front a few psi to see what effect that has? also drop a little preload off.

 

[Bobbin-Man]

Have you set the pre-load on the rear too soft?

 

[Jamieboy]

Hmmm, never thought about rear preload having an affect on the front?

I do have rear preload low (nearly as low as it goes) as i'm quite light (prob 12 stone in riding gear). Would that have an affect?

 

[DING-DONG]

Id say you need to set the sag for the rear as it does sound its too soft, google setting up suspension sag.

 

[Bobbin-Man]

Yes. I'm not much heavier than you and to get the front of the bike to work properly I need the rear pre-load / compression set a little firmer than I'd like. Fitting Hyperpro springs front and rear has been a big help.

 

[monkeyboy]

How does the rear pre-load effect the feel through the bars of hitting a bump with the front wheel - even before the rear wheel has hit it? I'm genuinely interested.

 

[Bobbin-Man]

Because increasing the pre-load on the rear will effectively reduce the pre-load on the front, same with the compression adjustment. Try to imagine it as an extreme scenario ... stiffen the the rear as much as you can so it's virtually solid - the front will bounce around. By contrast soften it to it's minimum and the front will be very stiff. In reality setting up the suspension is a much more black art to get it right but in simplistic terms this is what's happening

Due to my fairly low weight (by other tosser standards) my bike feels it's best with laden panniers and the rear stiffened to suit.

 

[Deleted account 211025001]

Or to put it more simply; decreasing sag at the rear (by increasing the preload) lifts the rear a tadge and loads the front more.

Not only will it allow the front suspension to work better but usually makes the steering more positive.

Andres

 

[Slipperyeel]

The only way to service the front is for a hole to be drilled into it, a valve is fitted and then with the new oil air is added. Otherwise the unit is not really serviceable bar changing the spring. It should be possible to see the valve. I don't know if it's possible but maybe there's too much air in there?

Alternatively, bite the bullet and get a Wilburs/Ohlins/Niton etc. I did this and very happy I did

As for the other comments about rear affecting the front. Definitely possible but not sure if your symptoms fit?

 

[monkeyboy]

I hear what you're saying about the rear. I'm just skeptical. Just imagine you turned the bike upside down. Twat the wheel with a big weight and it would damp it ok by the sounds of it. A little knock and it's too hard. The reaction at the bars to hittin a bump is virtually instant and is a direct force back up through the forks isn't it. At that point, the bike isn't rotating about it's axis and I think that before the rear damper gets involved. I can't imagine lifting the rear 1 or 2 degrees will make much difference in this situation. In my simple mind it sounds like the front it just a little too hard - probably due to compression damping.

Having said all that - I only have o-level physics and I do software so WTF do I know

 

[Bobbin-Man]

I hear what you're saying about the rear. I'm just skeptical. Just imagine you turned the bike upside down. Twat the wheel with a big weight and it would damp it ok by the sounds of it. A little knock and it's too hard. The reaction at the bars to hittin a bump is virtually instant and is a direct force back up through the forks isn't it. At that point, the bike isn't rotating about it's axis and I think that before the rear damper gets involved. I can't imagine lifting the rear 1 or 2 degrees will make much difference in this situation. In my simple mind it sounds like the front it just a little too hard - probably due to compression damping.

Having said all that - I only have o-level physics and I do software so WTF do I know

It's not about changes to geometry but sprung weight. If you increase the pre-load on the rear you increase the force that the rear of the bike places on the shock. Because there's no change in bike/rider mass the force applied by the bike to the front spring will therefore reduce, ie. the pre-load at the front will be less. Does that make sense?

 

[monkeyboy]

It's not about changes to geometry but sprung weight. If you increase the pre-load on the rear you increase the force that the rear of the bike places on the shock. Because there's no change in bike/rider mass the force applied by the bike to the front spring will therefore reduce, ie. the pre-load at the front will be less. Does that make sense?

Nope i think that's called magic. The weight distribution of the bike is the same isn't it? Say 50 50 for the sake of argument. Preload is relative to the sprung weight (the 50%) so putting more preload doesn't mean the weight distribution of the bike changes does it? It doesn't mean the front is now (say) 45% of the weight - so the front preload is still relative to 50% of the weight.

Perhaps I should stop and accept you know lots more about this than I do!

 

[Deleted account 200123001]

Could the shock be over pressurised giving it a too higher rebound?

 

[Bobbin-Man]

The weight distribution of the bike is the same isn't it? Say 50 50 for the sake of argument. Preload is relative to the sprung weight (the 50%) so putting more preload doesn't mean the weight distribution of the bike changes does it? It doesn't mean the front is now (say) 45% of the weight - so the front preload is still relative to 50% of the weight.

Yes, the weight distribution changes as you adjust the preload. I can't find anything on the net relating to bikes, maybe I'm searching using the wrong terminology, but if you Google "corner weighting a car" there's loads of info that'll help understand what's happening. The same applies to a bike, albeit with only 2 wheels.

 

[monkeyboy]

Yes, the weight distribution changes as you adjust the preload. I can't find anything on the net relating to bikes, maybe I'm searching using the wrong terminology, but if you Google "corner weighting a car" there's loads of info that'll help understand what's happening. The same applies to a bike, albeit with only 2 wheels.

I did and..

"The only way to change the static weight distribution percentages is to physically move weight around"

Which sounds correct. And then it talks about changing pre-load to adjust cross weight percentages which I can completely understand because there are 2 other diametrically opposed wheels to take the weight and around which the car can diagonally rotate/balance. Effectively if you let the tyres down on two opposing wheels then the others would take extra weight - I can understand that. It's not the same with a bike though. It's like trying to change the front/rear weigh distribution on a car and you can only do that by physically moving weight around. I guess that's why bikes typically have a remote preload for the rear only - as that's where you add extra weight with pillions and luggage.

So I can understand it with cars as there are 4 wheels, but I can't see it's the same with bikes. But that probably just means I'm stupid - not right

 

[patzx12]

I like soft suspension.
The way i set up my suspension is:
Everything on full soft, lowest preloads.
start riding and stiffen up as required reacting to what the bike is doing.