Anyone stuck an aftermarket shock in a DR650?

[Monstaman]

Thinking of looking outside the square a bit here and getting something with separate compression and rebound damping , remote reservoir etc maybe allowing a bigger choice.

Just an idea, see if anyone has the lowdown rather than reinvent the wheel.

[Bass]

Yep. I have and it's a common farkle as the standard rear really is underdamped in rebound - especially with a load on (e.g. luggage)
Ohlins front and rear in my case.
Seem to recall that the DR650 thread in the Aussie forum on ADVrider has buckets of info, although it's a huge thread and you may have to spend some time to find what you need.

[NordieBoy]

First try the cheaper way of filling the shock with 10w oil and recharging the reservoir to 150psi.
Cogent in the states also refurbish your old shock with adjustable guts.

[Monstaman]

Yep. I have and it's a common farkle as the standard rear really is underdamped in rebound - especially with a load on (e.g. luggage)
Ohlins front and rear in my case.
Seem to recall that the DR650 thread in the Aussie forum on ADVrider has buckets of info, although it's a huge thread and you may have to spend some time to find what you need.

Yes already waded through about 200 pages but nothing specific for what I wonna know unfortunately, some great info but no what I am after.

First try the cheaper way of filling the shock with 10w oil and recharging the reservoir to 150psi.
Cogent in the states also refurbish your old shock with adjustable guts.

Cheaper sounds better, how hard is it to do Nordie?, can Wanaka DR Engineering (my shed) do it or is is a Robert job?

[Squiggles]

Some put DRZ shocks in....

I'd like an ohlins plz

[Monstaman]

Sent an e to Gogent in the US, see what they say.

Having sold my MHe I have permission to 'upgrade' a few bits and pieces.

[NordieBoy]

Cheaper sounds better, how hard is it to do Nordie?, can Wanaka DR Engineering (my shed) do it or is is a Robert job?

I did mine.


And it still works.

[NordieBoy]

Sent an e to Gogent in the US, see what they say.

Having sold my MHe I have permission to 'upgrade' a few bits and pieces.

Cogent (Rick) will need your shock so that limits things...

But...
You could send him my spare shock and use yours in the meantime and gimme your old one when your new one arrives...

Or gimme your new one and keep using your old one...

[zeRax]

lol fran.

id probably go with a drz400e shock, cheap option, id check out the thumpertalk forums, lots of good seperate specific stuff in the dr forum there, no doubt find something, i thought about it, but im happy enough with the suspension, after all i weigh as much as a bag of peas

[Monstaman]

I did mine.


And it still works.

Do instructions come with this?, I am pretty good in my man space with all sorts of engineering goodies and oddities and knowledge from being an engine re conditioner and landrover owner (x5 over the years).

Cogent (Rick) will need your shock so that limits things...

But...
You could send him my spare shock and use yours in the meantime and gimme your old one when your new one arrives...

Or gimme your new one and keep using your old one...

I may as well just pay you direct and save myself all the bollies with NZ post

Will see what the e says from Cogent and if I choose that path I might take you up on that offer.

lol fran.

id probably go with a drz400e shock, cheap option, id check out the thumpertalk forums, lots of good seperate specific stuff in the dr forum there, no doubt find something, i thought about it, but im happy enough with the suspension, after all i weigh as much as a bag of peas

Another option which is cool, I am 74 kg so spring rate is pretty well ok for me, just need the rebound to act more sensibly, we are away to Mavoras next week with Toddy and we are two up so that will be interesting, already screwed the spring preload to near max which has worsened the rebound

[Bass]

First try the cheaper way of filling the shock with 10w oil and recharging the reservoir to 150psi.
Cogent in the states also refurbish your old shock with adjustable guts.

I am interested in the theory behind this.
What viscosity is the standard oil in the shock and what is the standard reservoir pressure setting, please?
I have a near new standard shock in a corner downstairs and adjusting the viscosity to get the desired rebound damping (not externally adjustable) and then setting compression accordingly seems like a really good idea for starters.

I also note that MM has commented that increasing the preload has worsened the rebound and i am wondering just what he means by this.
I presume he means that he has a passenger on the back and has increased the preload to keep the ride height in the correct place. That would mean that for any given shock position, the spring compression load has increased and so the rebound damping effect has diminished - i.e. the normal situation when adding a passenger.
However, I was wondering about the effect on damping of increasing the preload without adding a passenger. Let me see if I can explain what I am getting at.

The DR has a rising rate linkage and so the further the shock is extended then the less is the wheel movement relative to shock movement.
Under compression, when we hit a bump, the terrain has most control of the rate at which the the wheel rises and the shock compresses. Conversely, it is the spring/shock combination that has control of how quickly it extends again after the bump. Therefore, since increasing the preload with no extra weight on the bike increases the ride height, because of the variable rate linkage it should also decrease the effect of compression damping but increase the effect of rebound damping.

This of course completely ignores the effect on overall ride and the risks of the shock "topping out". However, I was wondering whether it might be a way to gain some small improvement in a setup like the DR which is chronically underdamped in rebound - i.e. ignore the normal setup guidelines and set the ride height a bit higher than would otherwise be the case.

My gut feel is that the improvement would be too small to be noticeable.

[Monstaman]

I also note that MM has commented that increasing the preload has worsened the rebound and i am wondering just what he means by this.

Heya Bass

All this means is that my damping is screwed right in to max and tightening the spring preload for MM and Mrs MM for two up at Mavoras has made the shock rebound to fast and allowing it to top out.

Saving grace is that two up we won't be going warp facter 2 anyway.

Keen on Nordies idea thos, appeals to me.

[warewolf]

I also note that MM has commented that increasing the preload has worsened the rebound and i am wondering just what he means by this.

In simple terms, with more spring preload, the spring is exerting more force when rebounding so the rebound damping effect is reduced. Even without any extra load, rebound will be worse with increased preload.

Say you had an 8.0kg/mm spring. Normal preload might be 10mm = 8.0 x 10 = 80kg spring force at rest. Increase the preload to 15mm = 8.0 x 15 = 120kg force at rest. On rebound the spring is pushing an extra 50% or 40kgf against the rebound damping at top-out, and increasingly more as the suspension moves through the stroke due to the exponential curve of the rising rate.

The rising rate curve is fairly flat in the initial parts of travel, particularly around the 10% travel position for ideal static sag, even as far along as the 33% rider sag. So at rest the effects would probably be negligible. However, it's the effects a long way in to the travel that could be the make-or-break. I can't come up with a clear answer - maybe you should ask the question in the suspension forum and get an answer from RT?

[Bass]

In simple terms, with more spring preload, the spring is exerting more force when rebounding so the rebound damping effect is reduced. Even without any extra load, rebound will be worse with increased preload.

Sorry but this is incorrect and this is an argument (discussion) that I have had many times.
"Preload" is a complete misnomer. It does not change the load at all - it just changes the distance between the top of the spring and the top shock mount.
The swingarm and so the bottom of the shock also, are free to move. Therefore, all that happens when you increase the preload setting is that the swingarm moves down and the ride height increases. This is appropriate if you are putting more load on the bike, which then brings your ride height (rider sag) back to the original setting.
However, with no change in weight on the bike the spring force and so also the spring length according to Hookes law, are unchanged.
You have to change the spring length to change the load that it is exerting, but how can you change the length when the bottom end is free to move?
Take a tape measure out and check this if you doubt what I am saying.

I agree with your comments about the linkage curve and its effects however. I didn't know the curve shape and so this is good information.

[NordieBoy]

You have to change the spring length to change the load that it is exerting, but how can you change the length when the bottom end is free to move?

Because the bottom of the shock is a set length from the top. It's only free to move to that point.











WARNING!
Waffling and thinking out loud follows...



5kg/mm spring.

5kg pressure to move 1st mm.
10Kg = 2mm.
15kg = 3mm.
50kg = 10mm.

Preloading the spring by compressing it say 10mm means it's putting 50kg of force into trying to expand.

Preloading 1mm means 5kg of expansion force.

The preload changes the startpoint.

Sit 90kg on the spring and both will compress to the same length (slack-18mm).

Remove the weight (over a bump) and the 1mm preloaded spring will push back with a force of 90kg diminishing to 5kg.
The 10mm preloaded spring will push back with 90kg diminishing to 50kg.