533 replies to this topic

[JimmyJamJerusalem]

typically, you need ~40/60 bump/rebound somewhat surprised at the stroke lengths too? (thinking about it, that sounds like that includes the rubber(s)?)

 

Ah ok, I did't know that.

 

I did include the rubber yeah. 

 

They sent me two closed measurements; one with the bump rubber touching and one with the bump rubber compressed.  Not sure what the relevance of that was so used the 'bump stop compressed value'.....

 

With that in mind then to achieve the -15mm from standard ride height we'd aim for the wishbone to be at 368.9mm split the stroke 60:40 and the shock limits are ideally 416.9mm and 336.9mm

 

So looking at the NTR they are 5.4mm away from the optimum droop position and have 5mm extra bump than required.  Now yeah that could be perfect but I don't think that's much of an issue by the looks but this gives 64.8mm droop 15mm less than a Quantum at the wheel so not exactly night and day.....

 

 

 

That said I believe there is more stroke lurking past the bump rubbers so although the 2012 spec onwards sounds ok there is defo an opportunity to improve the old spec NTR40's. 

 

Alex measured an open length of his 'old' 40's at 395mm which would only give around 45-50mm droop so yeah I can see why in this case what Simon found was alarming!!! 

 

What we need to do now is have people measure their own open lengths so we can see what's out there then we can come up with a solution that will suit anybody with an old spec shock but we need to see if people have 395mm open lengths or longer.

 

Can anybody wit concerns about this contact me and we will see what we can do

[Exmantaa]

This looks promising.

 

Small note to this; do we know/measured the shock length @ "standard ride height"? Or is it an assumption that stock height is halfway in between the wishbone min/max angles?

[cnrandall]

For old dampers suggest fitting +10mm rod and an adjustable bottom eye (which ends up circa 8mm longer than a normal one IIRC). 

[siztenboots]

I would have thought a lot of the affected shocks are due a service anyway, so discuss replacement parts with Nitron

[techieboy]

So exactly what am I supposed to be measuring? Mine have certainly mullered some upper wishbones in their time. I spoke to Pete at Nitron years ago and he said it was the first they'd heard but they'd built them to specs supplied by JT originally. Not sure whether the suggested bigger bump stops were fitted when they were rebuilt via Cornering Force but I did ask Simon to check with them about revised stops and longer rods.

[siztenboots]

I'm not sure making the lower rod section will work, its the damper body that needs to be offset ( guessing that what the +5mm fix is )

[JohnTurbo]

Longer rod would need the extra bump stop im guessing. Im on 395. When I fitted them I was instantly stunned and certain Id wound up with s1 shocks. It looks 'low' when the wheels are hanging in the air. Ive been moaning about them being too short ever since. If id bought them new theyd have gone back by return. Its kinda amazing its only now this has sort of come out. - That said there were references on the forum to length going back years when I looked. Actually it handles great but I cant drive it sensibly on the roads! Jimmy im all in for being helpful, and appreciate any assistance we can get. Its no fun being too short.

[alexb]

Measuring? Full open length from middle of the top eye to middle of bottom eye. Perhaps your dampers are like mine 395 mm full open, 310 full closed (taking some bumpstop compression into account). The 310 means that you potentially can hit the topside of the subframe. I say potentially, as it will depend on other things. I don't have a problem with it, as I drive like a senior citizen.

 

About shock length and ride height (really trying hard to get the th and ht right). When I measured, 373 mm of shock length corresponded with 125 mm ride height. I did most measurements a couple of times, but allow for some millimeters variance here and there. It'll never be exact anyhow. From that point 40% bump and 60% droop. With the 80 mm total available travel (with mine it's actually closer to 85 mm, but that also depends on how compressed a compressed bumpstop is) that means 32 mm down and 48 up. Or 341 mm full closed and 421 full open. Again, give and take some mm here and there.

 

My available droop now is about 40 mm, see pictures (guess it actually looks more due to the shadows)

 

On the ground at about 125mm ride height

 

In the air full droop

 

And yes, I have funny wheels and tires (as it influences ride height: 235/40/18: 643 mm diameter measured)

 

As Randy remarked, would be great to have adjustable eyes

[techieboy]

Measuring? Full open length from middle of the top eye to middle of bottom eye.

If, as this thread seems to say, mm's are critical, I'm not sure measuring to a subjective point in mid-air of the eyes is really going to help.

[chris_uk]

That looks like less droop than my gaz monos.

[CHILL Gone DUTCH]

The latest Gaz pro have huge droop qualitys And they are 10 times better than the old Gaz pros

[Mike (Cliffie)]

The latest Gaz pro have huge droop qualitys And they are 10 times better than the old Gaz pros

Thanks Chill, we worked really hard on getting them right this time.

[CHILL Gone DUTCH]

The latest Gaz pro have huge droop qualitys And they are 10 times better than the old Gaz pros

Thanks Chill, we worked really hard on getting them right this time.

The confidence they gave me from the first lap was spot on, I do think there's more to come from these but I didn't get chance to mess with settings. I decided not to do a geo until I had tried them out on my old setup so I had a like for like comparison,

Edited by CHILL Gone DUTCH, 24 July 2013 - 01:35 PM.

[JimmyJamJerusalem]

 

Measuring? Full open length from middle of the top eye to middle of bottom eye.

If, as this thread seems to say, mm's are critical, I'm not sure measuring to a subjective point in mid-air of the eyes is really going to help.

 

 

 

Yeah it is a pain in the ass to measure right as parallax error can throw you out. 

 

If there are a number of 395 o/l shocks out there (which seems pre 2009) I've got a tidy solution in the pipeline but since 2012 the open length has been much better.  not sure what's in between to be honest which is what we need to find out

 

John - I'm pretty short myself

[techieboy]

(which seems pre 2009)

Think mine are more like 2006/7, so pretty sure I fall into that category. They're still going strong though.

[Scuffers]

Finally, we are getting somewhere!

 

OK, if the stroke is indeed only 80mm then this is where it starts to get hard.

 

80mm is OK, so long as you have the overall lengths such that at static ride you have the damper some 40% into it's stroke, that would give you some ~65mm droop and ~43mm of bump.

 

the issue is that unless you have them made to the right open length for the ride height you intend to run (and as said, wheels/tyres will have an effect here) the likelihood is that your static point is not going to be anywhere near this..

 

(this is why other damper makes have spec'ed their dampers with longer stokes so that they can more easy deal with the typical range of ride height demands without having to have specific spec's for a given height)

 

Personally, I would consider anything less than ~60mm of droop from static ride is going to be too little, if you consider what happens to the cars in a corner, the car does not have to lean much to come to the limit of droop and then start to lift the wheel.

 

for example, this car has 80mm of droop, and this is the point where the damper is 'toped' out:

 

 

Now, obviously in a corner, the loaded side would also be in bump, but it demonstrates the point, it's not much of an angle before you run out of travel

 

now, on a racecar with high spring rates etc, this is actually less of a problem as the higher the rates the less wheel-travel you will get/need, however, on the road, you need pretty much all you can get (which for the Lotus/VX is actually quite limited to start with).

 

I much admit, when I looked at the NTR's, I had assumed that the exposed shaft would be all used in the bump travel, but from what Jimmy has posted, this would appear not to be the case? (as in the damper bottoms out well before the shaft-nut reaches the body?)

 

if the 80mm is correct, then for 99% of VX users out there, I would suggest that as running them lower than ~120mm heights (rear) is pointless/not going to happen, so ideally you want the open length longer so as to set the 80mm window more inline with the ride height being used.

 

(to be honest, this would be a lot easier if they had ~100mm stroke, as this easily covers 99% of usable heights)

 

Edited by Scuffers, 24 July 2013 - 02:01 PM.

[alexb]

Question about droop I was about to ask anyhow, but this is a nice trigger. So now we either have, or will get more droop. That's a good thing from what I hear. But besides droop, you need force, as droop without force is not going to give you any traction. Assuming that the unsprung mass you always have doesn't enable a lot of traction. Now my problem is the dynamic balancing act on 4 or 3 wheels. Take a car with one wheel in the air. You can either say: not enough droop. But can also say: not enough force to keep it down, as that's the reason it's in the air to start with. I do realize that it's a balancing act and with more droop at that corner it might be that weight shifts differently, but I just can't get my head around it. What causes that wheel to lift I mean.

 

BTW, same reasoning as above would mean that using a zero rate spring to close a gap between a loose spring and collar is not a good idea at all (for our cars I mean; with limited wheel articulation), because the zero rate spring is not capable of extending any force in the entire window it operates in. And even high pre-load would not be a good thing, as that corner is not compliant (i.e. spring is not compressing) until it reaches the pre-load force.

[Mike (Cliffie)]

The weight of the wheel brake and hub has to be enough to force the damper down unless your wishbones are siezed.

 

FWD cars are well known for cocking a rear wheel on corners and yes, this is a lack of droop usually coupled with stiff chassis and high bump travel (Mmmm-reminds me of my R5).

[Scuffers]

The weight of the wheel brake and hub has to be enough to force the damper down unless your wishbones are siezed.

 

FWD cars are well known for cocking a rear wheel on corners and yes, this is a lack of droop usually coupled with stiff chassis and high bump travel (Mmmm-reminds me of my R5).

err... no.

 

ignoring the small matter of inertia, gravity is not enough to overcome the rebound damping in any significant way 

 

 

 

Question about droop I was about to ask anyhow, but this is a nice trigger. So now we either have, or will get more droop. That's a good thing from what I hear. But besides droop, you need force, as droop without force is not going to give you any traction. Assuming that the unsprung mass you always have doesn't enable a lot of traction. Now my problem is the dynamic balancing act on 4 or 3 wheels. Take a car with one wheel in the air. You can either say: not enough droop. But can also say: not enough force to keep it down, as that's the reason it's in the air to start with. I do realize that it's a balancing act and with more droop at that corner it might be that weight shifts differently, but I just can't get my head around it. What causes that wheel to lift I mean.

 

BTW, same reasoning as above would mean that using a zero rate spring to close a gap between a loose spring and collar is not a good idea at all (for our cars I mean; with limited wheel articulation), because the zero rate spring is not capable of extending any force in the entire window it operates in. And even high pre-load would not be a good thing, as that corner is not compliant (i.e. spring is not compressing) until it reaches the pre-load force.

 

yes and no.

 

yes, there is no point in having a lot of droop travel if the spring platform is 100% unloaded, this is why people use tender springs (or progressive rate ones)

 

in an ideal world, even at droop limit, you want some significant pre-load on the damper so that it's always pushing the wheel down right up to the point of the damper topping out.

 

a wheel needs some force to the tarmac to get an meaningful grip, and even if you have a torsen LSD, it still needs some wheel torque to work with.

[Bumblebee]

I remember you having the Prima racing r5