DR650 static sag

[Crisis management]

While on this topic, what symptoms was it that pushed you out on to the Mangere bridge with cardboard and scissors?

I found the wind pressure on my chest a bit of a pain after a couple of hundred Kms so decided to experiment with a small screen, or as hairy arse below states, something about piddly little biceps....

[QUOTE=tri boy;1373397...or that Ian's piddly little biceps couldn't hold a teaspoon of sugar in a stable manner, let alone a motorcycle handlebar[/QUOTE]

You'll keep, boy, you'll keep.

How's it go, revenge is a dish best served cold?

[Ocean1]

Again I fail to comprehend, which is not all surprising and almost commonplace.
Why would this adjustment influence front end grip?

I can see that changing the rake influences the lean angle that the wheel adopts as it turns, but we are still talking miniscule changes.

It's complicated, (which is one way of saying I don't know) and there's more to it than the effect the simple geometry changes make. It's partly related to how modern dirt bikes work, and the need to weight the front wheel and the outside peg. If you don't get this technique right, (and I'm an expert at getting it not quite right) then you risk putting too much lateral force on the front.

Whether the theory is valid or not it helps me to imagine I'm forcing the front tyre into the ground, as opposed to simply leaning it in like you might on the road, which produces more sideways force. More rake and trail exacerbate the tendency, that's all, and because I learned on bikes that were a bit less radically optimised for MX style handling my style isn't quite right, and my reactions sometimes get me into trouble.

There is some insight to be gained by imagining an extreme case like a tradional chopper. Huge rake and trail. Imagine that leaned over in sub-optimal conditions, the steering required to turn it in is way more than that needed on a dirt bike. The tendency for the front to slide out is higher, and yet there's less weight on the front end to hold it.

[Bass]

You'll keep, boy, you'll keep.

How's it go, revenge is a dish best served cold?

I think that may be exactly what we are seeing - something to do with U-boats as I recall

[NordieBoy]

Any idea why?

It's a tiny change to the steering angle after all.

Moving the forks 3mm in the clamps of my XR250 makes a noticeable difference in the handling.

[ducatijim]

Well, while I claim to be an engineer, I never claimed to be a good one and I kinda thought that Mr Suzuki was pretty likely to be better than me.



P.S. It's also why Mr Suzuki makes quads for cow cockys isn't it?

If your 'Mr Suzuki' , engineer extrordinaire, could so badly fuck-up the design and building of the DR's so-called seat, wot makes you think he could get something as complicated as a sidestand correct???

Quads? short-arses??....u fucken try carrying 2x portable fence reels, 20kg of pigtails and the newborn calf all on your 2 wheeler at once.....if you can, then you are truely a better man than I.

[Bass]

If your 'Mr Suzuki' , engineer extrordinaire, could so badly fuck-up the design and building of the DR's so-called seat, wot makes you think he could get something as complicated as a sidestand correct???

Quads? short-arses??....u fucken try carrying 2x portable fence reels, 20kg of pigtails and the newborn calf all on your 2 wheeler at once.....if you can, then you are truely a better man than I.

You are getting a bit off topic there, aren't you mate?

Anyway, I seem to remember you doing all of that on a Honda 90 and that was built for short arses too.

PD here we come.

[Bass]

Moving the forks 3mm in the clamps of my XR250 makes a noticeable difference in the handling.

I can't even get close to understanding why.

[warewolf]

I can't even get close to understanding why.

Why wouldn't it? We are talking about subtle differences here.

A couple of turns of preload, a click or two of damping adjustment, a couple of psi in the tyres, position of the rear axle in the chain adjusters, etc etc. All very minor things that can make a big difference.

[Transalper]

I'm sorry, not sure i picked up all the things under descusdsion here while skimming the thread...
re side stand length, you guys do know don't you that they supply two side stand lengths, one for standard ride height and a shorter one for when the bike is set to the lowered position.

[cooneyr]

Call me a nOOB but - ride the damn things for a good year or so till your actually getting to the point pushing the limits of the stock bike, then figure out what is wrong and deal with it. You need to establish a base line and if your skills wrt a particular bike are still improving significantly your not going to be able to do this.

I know this isnt going to help you Bass but others tend to spend to much time farkling and not enough time riding if you ask me (I know ya didnt ). My speed and confidence on the DR has improved significantly over the past year and I've not changed a thing (OK got the forks serviced - seals and oil replaced). I don't even remotely consider myself ready for major changes such as ohlins (not that I'd ever do that anyway). Might do a stiffer shock spring and shock rebound revalve middle of the year but not sure I need it yet.

Cheers R

[Bass]

Why wouldn't it? We are talking about subtle differences here.

A couple of turns of preload, a click or two of damping adjustment, a couple of psi in the tyres, position of the rear axle in the chain adjusters, etc etc. All very minor things that can make a big difference.

So I believe - I'm just trying to get my head around the physics, geometry and mathematics of why. So far, the things I am being told, it seems to me that the result is out of all proportion to the size of the adjustment.

[Bass]

I'm sorry, not sure i picked up all the things under descusdsion here while skimming the thread...
re side stand length, you guys do know don't you that they supply two side stand lengths, one for standard ride height and a shorter one for when the bike is set to the lowered position.

Yep, DJ's bike has been fed the lowering kit - that's what a bit of the earlier banter was all about (short arse references etc)

[Bass]

Call me a nOOB but - ride the damn things for a good year or so till your actually getting to the point pushing the limits of the stock bike, then figure out what is wrong and deal with it. You need to establish a base line and if your skills wrt a particular bike are still improving significantly your not going to be able to do this.

I know this isnt going to help you Bass but others tend to spend to much time farkling and not enough time riding if you ask me (I know ya didnt ). My speed and confidence on the DR has improved significantly over the past year and I've not changed a thing (OK got the forks serviced - seals and oil replaced). I don't even remotely consider myself ready for major changes such as ohlins (not that I'd ever do that anyway). Might do a stiffer shock spring and shock rebound revalve middle of the year but not sure I need it yet.

Cheers R

I don't disagree. However Jamie and I are off to OZ for 2 months later this year and will do around 18,000 km, mostly on 4WD tracks and heavily loaded. The standard rig just won't hack it and so the mod's have to happen regardless of my experience (or lack of it).

[warewolf]

So I believe - I'm just trying to get my head around the physics, geometry and mathematics of why. So far, the things I am being told, it seems to me that the result is out of all proportion to the size of the adjustment.

Maybe I can explain it geometrically...

If the result curve is plotted, at some point there is a 'knee' where for small inputs there is a dramatic difference in output. Bikes are set up at that knee. The further a particular setting (or range of adjustment) is from that knee, the less effect it will have, and vice-versa.

Consider a conical needle valve. At closed or nearly so, the size of the opening increases greatly as the needle is backed out, therefore so does the flow through the valve. Typically after a few turns, there is very little difference in response as the size of the opening goes from essentially 'infinite' to 'infinite plus some small increment = infinite'. In this particular example, some of the reason is that the orifice of the valve becomes the limiting factor, not the opening around the needle point. (Thanks RT.)

Zat what you were asking?

[Ocean1]

Maybe I can explain it geometrically...

S'not geometry, that's hydraulics.

And you're saying he needs a bigger orifice?