Coil-over shock settings

[Merv and Sharon]

I know that many have double adjustable shock with coil overs and also that the settings used vary according to driving purpose/s, spring ratings and so on.

But, I was wondering what range of settings, front and rear, are being used for street purposes on double (compression and rebound) adjustable shocks? It might be a useful guide. I have the fronts pretty right with equal rebound and compression in a the mid range of the QA1s adjustments (18), I feel but it seems too 'bouncy' at the rear.

[Tenrocca]

Merv - Mine are only single adjustable but have them at 4 clicks off full soft on the street - full hard on the track. I suspect it would be hard to make comparisons between models though, as spring rates, shock mount angles and mounting points would all come into play. Too soft on the back.... turn em to hard till it your arse tells you if it feels alright.

[Merv and Sharon]

Thanks Andrew. Yeah, there are so many variables but you also have the same King keeper springs, do they have an effect on your rear setting?

[Tenrocca]

Not at all - they are permanently compressed. Only time they extend is when jacking up or getting airborne on one of my frequent off's on the track

[Merv and Sharon]

I may have to compress mine more. Will check them when the car is down off the hoist again. You are getting full value from those track outings!

[Ron61]

I ran mine at 4 clicks off soft on the street but it varied from track to track as to where I ran them. I also made sure that the springs matched the type of driving I was going to be doing. Remember the rear end is going to be lighter than the front normally and I had my car balanced at 51 front 49 rear. Also used the scales to make sure each corner was set right before and after a hard run. And the weight of the car has to be considered if you are going for the optimum set up. It is really hard to give a set up that will work for all drivers. You have some good suggestions on where to start and then you will need to work it out to suit your style of driving.

Ron

[Merv and Sharon]

Thanks Ron. It is rather difficult up this way to get the individual wheel weights done. I have tried quite a few places, but no luck so far. I was particularly interested to see if others have used different settings for compression - versus - rebound, or just the same settings for each.

[Gav]

I have double adjustable AVO's on mine.
The fronts generally for the track are set with the bounce hard(one click off full) and the rebound about mid way.
The rears re the opposite, the bounce is set at about mid way and the rebound just off full.
The idea being to allow the nose to lift and the arse to drop to allow maximum weight transfer to the rear tyres. Then under braking you want to limit the transfer to the front.
Works for me.

On the street I just back off the bump on the front and leave the rears as they are.

[FUNFER2]

I did the same as Ron.

Think about scaling the car on all four corners, it's well worth it !
I thought my setup was real close, boy,..... was I wrong.

I started off just wanting to replace the coil overs and lower the rear ride height, then included getting new heim joint's on the rear, so I borrowed a friends electronic weigh scales. Man, each corner was way different. I made a threaded rod strut tool with heims that mounts to the shock mounts to get the height I wanted, then measured what length of springs I needed. Worked great. Even with a BB, the percentage now is 48%-51%.

For fun and as a test, I may take the cockpit adjustable,....shocks of our sprint car and hook them up to the cobra. That way, no matter what person I have with me or what road condition I'm driving on, I can adjust the shocks on the fly, without stopping the car.



__________________
Thanks,
Kevin

[Merv and Sharon]

Thanks Ron and Gav. I must get the wheel/corner weights done and modify adjustments accordingly. Even the local Pedders could not do it. Gav that is very sensible advice and I will be giving it a try soon.

[Merv and Sharon]

Thinking I will also go back to the 250lb rear springs.

[Merv and Sharon]

Thanks for the PM Rog. The spring rate calculator is useful and I have ordered some 250lb 12" springs.

[DaveW]

Folks,
Are bump stops recomended on coil over shocks,
just got my QA1's, mounted to chassis to check clearance and it dawned on me that nothing stops it thumping into the end, unless the spring binds before getting through the full stroke,

Also, got 12" springs for the rears, had to compress them 15mm for the spring seat to clear the lower arm, i.e. need 11.5" springs for a perfect fit,
is there a ratio of compression to vehicle lift,
Not sure if i'm thinking this through correctly, but if the springs are rated at 400Lb/In, and ive compressed it say 1/2", what does this mean in terms of ride height?, rear end will weigh about 580kg when finished.





Dave

[Merv and Sharon]

Dave I have 12", 250 lb QA1 rears and the DD501 12" shocks. I found that the 300lb was too bouncy and that I needed the crank up the Rebound damping a fair bit to reduce that. I also was made up some small collars from when I had 10" 300lb springs. That helped to make sure that it all stayed together on full droop. However, with the 12" springs, mine are pretty much like yours, with some degree of preload.

The rule of thumb that I was given was that the shock should be able to move within at least 60% of its travel. Mine do that. The only bump stop I can see is the small "o" ring! My old AVOs had a bump stop but far less travel than the QA1s. The cars sits well at present with all heights (from the wheel arch centre - unreliable) equal. I plan to wheel/corner weights soon and adjust accordingly.

[Krait]

Merv,

You can't use the wheel arches as a point of measure, instead measure from the ground to the frame rails. Having the nose should be slightly lower than the rear appears to work best also.

Cheers

[Merv and Sharon]

I know Geoff it is only a rough guide. I also check shock travel and height from the chassis edges. Wheel weighting will help!

[DaveW]

Merv, i think the reason the spring rates are high on the CR is the leveridge action on the shock, the angle is about 27deg off the verticle at ride height, spring compression is about 2.5" to the wheel movement of about 3.8". so a ratio of 1.5 Plus a fair distance from wheel to pivot point.



I plugged the dimensions into the spring rate calculator that was floating around here awhie ago, and came up with an ideal rate of 381 front, 406 rear, almost the same calc as Toperformance in Vic suggested to me of 375/400, so thats what i ordered, at $37 each from Summit, it wont be too big a hit if im out of the ball park.

My main concern was how far the car lifts for each mm of spring tension, must be calculatable.

Dave

[Merv and Sharon]

Yes Dave I can see now that the CR has quite a different set up from the Nissan rear. That angle and the distance involved would change things a lot. I altered the upper perches for my shocks to make them even more vertical than they were before. They are relatively upright. I was also able to modify the lower shock mount to get reasonable clearance.

[Merv and Sharon]

Initially I used some 2cm upper spacers with the 10" springs to reduce the amount of adjustment I had to use on the shock absorber adjustable collar. These fit under the upper bearing mount of the QA1