Spring Rates on Harrison

[T.L.]

Hi guys,

I am looking at my springs as they are a bit soft as I have tyre hitting guard on a few occasions and they are wound up to a point where I don't want to take them higher.

I have a Harrison with a LS3 in it, so would appreciate any advice from those with alloy blocks.

At the moment I think they are 200 or 250 but need to get sometime to get wheels off to confirm this.

Cheers

[muzzza]

My Harrison ( 107 ) has LS2.......QA1 shocs with 350 lb at front and 300 lb at rear. It is fine on hotmix or motorway surfaces, but is pretty hard on country roads ( around Beerwah QLD ). I have changed spring perches so I can re-jig simple brackets to change ride height. Have a couple of pics ( very average - old camera ) in my gallery if that helps.

[Pecal]

I'm using Warwick's recommendation, 300lb front and 250lb rear and for me they're a good compromise between comfort and being reasonably compliant and good road handling. The only disappointment is the AVO's, they would work much better if they kept the oil inside and not on the road..

Peter

[sambo]

Lawrence haven't you got the custom IRS on yours? Others with the Nissan suspension are probably only good for a ballpark on the rear. Eg, different spring/arm lengths and angles.

[Kimbo]

I have Harrison No. 6 and use 400lb front and 375lb rear with double adjustable QA1's. The springs are fine for the road (slightly hard) but on the race track the tyres still hit the guards.

Kim

[Merv and Sharon]

Originally Posted by Pecal

I'm using Warwick's recommendation, 300lb front and 250lb rear and for me they're a good compromise between comfort and being reasonably compliant and good road handling. The only disappointment is the AVO's, they would work much better if they kept the oil inside and not on the road..

Peter

Same here. Great ride, but I ditched the AVOs (they all leaked and then after re-building leaked again). Now QA1 double adjustable all round. I did put longer shocks at the rear than standard and this gave better travel from compression to full droop. The angle on the rears is near vertical so you don't need a high spring rate. Having the correct wheels helps with avoiding rubbing on the guards. Never had the problem.

[T.L.]

Originally Posted by sambo

Lawrence haven't you got the custom IRS on yours? Others with the Nissan suspension are probably only good for a ballpark on the rear. Eg, different spring/arm lengths and angles.

Yes, I have the Mustang/Thunderbird rear end, but that end seems to be okay, just need longer springs.

It's the front that seems a bit soft as I'm pretty sure that when I went over a low part in the road while I had a go-pro on it hit the sump. Shows up on the video footage where the tyres hit the guard though, just need to get underneath the car and have a look.

Also reckon that my speedo is out as it only takes a few seconds to spin it to 100!!!.

I will be, hopefully today, getting the wheels off and at least getting the spring rate, I will go from there, but 300-350 might be good for the front and I might wait and see for the rear.

Cheers and thanks guys.

[sambo]

TL, what about damping? Assuming you have adjustable shocks, have you tried increasing the compression settings? I only need to move my QA1s a few clicks and the car feel completely different over bumps.

[T.L.]

I put the car 2ft in the air today and took the wheels off.

Found I have 275lb springs all around the car, and also a big petrol leak!!. Leak fixed and while I was there I would the R down a bit and the C up a bit. Still need longer springs as there is about 4" of thread showing underneath the spring and at some stage in the compression of a spring, it looses its ability to do it's job correctly.

Might head for some 14" 300lb on the front, the rears might stay at 275 but move to 12", so I need to move the fronts onto the rears and get a new set for the fronts.

Also gave me an opportunity to have a look for any loose bolts and put some locking wire onto the knock ones.

[Merv and Sharon]

The QA1s need to be experimented with. I finished with C3 and R5 all round for a nice ride and balanced handling on the road.

[muzzza]

TL There are a swag of reasons why you should never have the same spring rates front and rear. Spring length does not change ride height. If you wish to raise the car, you can use stiffer springs, longer shocks, or lower your upper spring mounts. Crazy amounts of spring pre-load is not an option. QA1 make 1" and 2" shock extensions as an alternative to purchasing longer shocks.
I am using 17" QA1 DD shocks and 10" springs on the rear of my car and 15" QA1 DD shocks and 10" springs at the front. I have also dropped front upper spring mounts about 10mm giving about 15mm extra height at wheel ( 18" rim )

[T.L.]

Originally Posted by muzzza

TL There are a swag of reasons why you should never have the same spring rates front and rear. Spring length does not change ride height. If you wish to raise the car, you can use stiffer springs, longer shocks, or lower your upper spring mounts. Crazy amounts of spring pre-load is not an option. QA1 make 1" and 2" shock extensions as an alternative to purchasing longer shocks.
I am using 17" QA1 DD shocks and 10" springs on the rear of my car and 15" QA1 DD shocks and 10" springs at the front. I have also dropped front upper spring mounts about 10mm giving about 15mm extra height at wheel ( 18" rim )

Thanks for that information.

At the moment I have 'crazy amounts of spring pre-load' so want to reduce that way back. I'll have to dig out the paperwork on what length shocks they are.

Car seemed to take the road bumps a bit better with the new settings, just need more time on the roads.

Found out that the ABS didn't work so I'll need to look into that as well.

[sambo]

Originally Posted by Merv and Sharon

The QA1s need to be experimented with. I finished with C3 and R5 all round for a nice ride and balanced handling on the road.

This is very similar to what I have - compression is 4 though. If what I read is correct, compression damping controls the movement of unsprung weight and rebound controls the sprung weight - ie, the weight of the car. Hence why you typically want more rebound damping.

[sambo]

TL, I was under my car yesterday and had a look at the rear springs - 12" 250lb. If I back off the compression setting on my QA1s, it gets bouncy very quickly. Tighten it up a notch or two and it goes rock hard. It's almost like the damper has too much control over the spring rate, so I'm toying with going to 300lb.

I have another issue where the left hand rear side of the car is 35mm higher than the right, as measured vertically through the centre of the axle to the underside of the wheel arch - similar measurements across the rear-most point of the doors also. The coil spring retainers are wound up equally on both sides (30mm from the start of the shocker "thread") and the front end is pretty much even. To have such a difference is a bit of a concern so I'm going to swap the coilovers/springs and hopefully this will show me whether the springs are evenly rated. I don't want to wind one side up further than the other for obvious reasons. This is assuming my chassis is true and square.

Fun and games!

[sambo]

Well I fixed the above issue tonight so I'm finally able to stand the rear wheels up with about -0.5 deg camber and the 275s now tuck up nicely inside the guards thanks to narrower track (roughly 10mm each side). It was a bit of an investment fitting adjustable arms all round but it allows you to remove just about all of the preload on the QA1s. I lowered the rear another 8mm, compression set to 3 and rebound to 6 and I now reckon 250lb springs are spot on with the R33 rear end.

[leroy17]

Am I right in that this was achieved with the adjustable lower arms that you had (blue colour) and the upper arms.

10mm is a good amount.

You know we all love photos.

[sambo]

Leroy, adjustable upper and lower control arms, traction rods and toe arms.

Here's one being prepared for a track car.