Not sure what will actually be “settled”…will the bushes actually be fitted and bolted up in a wishbone to test…or is it just a comparison for stiffness…Steve
My initial plan was to make a new test fixture representing a dummy wishbone, to compare radial stiffness of the four bushes I currently have. That translates directly to cornering stiffness on the car.
I’m also interested in looking at their behaviour in twist, as occurs with vertical suspension travel. I’d like to know how much travel can occur before the harder PU bushes slip, and whether we can take that information back to the new suspension on Peter’s modified car. That starts from the idea that slip is undesirable from at least a noise and wear perspective, possibly also negative for ride quality if it shows as a “stick-slip-stick” effect.
I realise this has diminishing interest for reasonable people. Thanks for visiting.
Hi Clive iv sent you a PM…but as iv mentioned not all PU bushes are designed to operate in the same way…some of the stiffer PU are designed to slip…you actually apply silicone grease to aid this…so there is no “twist”…not for a road going E type in my opinion…Steve
Thanks Steve, understood. I’ll test as many setups as possible and publish all the results here.
An obscure question to those with adjustable Gaz rear dampers - has anyone ever run them with the two units on one side adjusted differently?
That would normally be a pointless question because you’d expect the pair to balance out in the middle, so might as well set them the same.
But I noticed the minimum setting (light blue line) has very low rebound forces in the low velocity region which typically covers roll and ride comfort - the area shown by the red oval. Although that looks a bit useless in itself, it offers the chance to offset the very sharp change of direction given by the mid and maximum force settings - in contrast, they could feel very abrupt or “tuggy” on small bumps and swells (dark blue and black lines in the red oval).
If you set one unit near minimum and the other significantly higher, you could get the desired total force with a more gentle transition (in the red oval) as the combination has a more gentle change of shape - rounding off the sharp corner. This is shown by the green line and might translate to a more relaxed ride feel.
This is absolute conjecture as we’re planning the teardown of these units. It’s a long shot, I wouldn’t go to a lot of effort to check the idea but I think it could be easily tried with a tweak on the control knobs if someone is working in that area?
Teardown results soon.
Clive,. I’ll give it a shot. Right now I’m at 5 in the front and 8 on all rears.
Shorter Clive: I see about 20 hours of track testing.
After the month of road work? Can’t rush these things
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Thanks Tom.
Your click settings are similar to others I’ve seen mentioned here, it seems rear adjustment is typically significantly higher than front. That’s interesting as our testing says clicks and forces are comparable front to rear, yet I can’t think of many factors influencing rear damping to be 3x higher than front.
- damper lever ratios are very similar
- front and rear axle loads are in the same range, maybe 20% higher at the rear?
- rear wheel rates are slightly higher, depending which figures you trust?
- against that, the front ARB is stiffer than the rear
I don’t see anything there that accounts for a rear:front damping ratio of more than 300%. Possibly some additional rear damping needed to take account of the 6 metal link and driveshaft joints each side at the rear, compared with rubber bushes with their own inherent damping. Would that account for a large increase in rear damping?
What happens if you increase the front damping to a more conventional ratio?
I will definitely try that. My experience so far was to start at 3 and work my way up.
My thinking is that the lever ratio has a bigger effect than anticipated. It reduces the velocity on the way in and it reduces the force on the way back out. I don’t think you can square the lever ratio like we do with springs because the dampers are not linear.
Short version of my list so far:
IRS mounts
More front damping
7/8 in front stab bar
Max front caster
Agreed, I used the straight ratios of the lever lengths, adjusted by the spring angle. It’s all a massive approximation anyway, a bit of curiosity while I’m waiting for some bits of steel to make test holders for the front LCA bushings. I might suggest that for your evaluation list if the results look good.
Well the steel for the bushing tests arrived today. 2 x 2 inch section, I thought I was ordering just enough to house a pair of bushings but somehow one end of our close-knit supplier-customer equation got the mm and cm crossed. My first indication was the delivery man angling up the drive this morning on an ever decreasing radius with almost a yard of carefully bubble wrapped steel threatening his structural integrity.
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That’s why we have machine shops… 
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Is that your sunset/my sunrise?
Sunset, as it happened
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Sunrise looking at mount buffalo and the great alpine area from Glenrowan……… seems sunrise around the world is just as beautiful everywhere …. My step son wakes up to these every day!
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Beautiful, thanks Danny. In the distant past I went on drive trips in that direction from the (GM) Holden Proving Ground at Lang Lang - Yarra Ranges, Lake Eildon, I don’t think we ever actually went as far as Glenrowan. Lovely country.
One of many memory points was taking a group of Chinese engineers into a bar in one of the remote hill towns. It was like a Clint Eastwood western, not a sound as the door swung shut behind us.
Friendly cultural exchange followed once we established a common language (beer).
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