Setting up two way adjustable shockers??

[Al Weyman]

Hi guys, looking for a bit of advice here as I think I may have been going in the wrong direction but speaking to a fellow competitor who was following me at the weekend the rear end of my car seems set up all wrong and I cannot also get it to hook up and when I accellerate out of a hairpin for example the rear wheels just light up in a cloud of tyre smoke.

The car in question is my 3rd Gen Camaro IROC-Z, its front engine rear wheel drive and I have done a Steve Spohn Racing coil over conversion on the back with QA1 double adjustable shocks. http://www.spohn.net/shop/1982-1992-...le-Shocks.html

When I asked them for initial settings they told me 2/3rds 1/3rd bounce/rebound but according to a friend of mine thats what you want on front for anti-dive but the opposite on the back as you need to induce some squat!!!

If this is the case and obviously I will try it at the track but testing time is limited for me, but does this theory make sense as the car feels rock solid on the back and in honesty despite spending a great deal of money on the kit I think it handles worse than it did with the standard IROC springs cut down and the standard Bilstein shocks the car comes with (it is a performance handling package on the IROC). Any advice would be appreciated to get something out of this potentially quick car as with close on 475bhp + I should be lapping Snetterton 300 quicker than 2:26 even with an old git behind the wheel!

[phoenix]

I don't think you can expect to get the best setup without some testing. The normal approach would be to start off with bump and rebound at the softest settings, then increase bump incrementally until the driver feels (or the stopwatch shows) it is too hard, than back off to the previous setting. After the bump has been set, use the same incremental approach to setting rebound.

The damper will have a basic bump/rebound ratio which could be anything from 1:1 (bump and rebound damping equal) to 5:1 (bump five times stiffer than rebound) so the settings you were given initially would be obtained with equal clicks on bump and rebound adjusters if the base ratio is 2:1 (bump/rebound) - so I think what you were told about initial settings could be a red herring.

As you don't have the opportunity to test, I would suggest you try it next time out with bump and rebound backed right off. This should give the grippiest possible rear end and you may find the car has more understeer than previously. Have one or two guys in the pit lane (who you have shown exactly what to do) ready to quickly adjust the bump settings a few clicks up during qualifying then go out and try again. If you can make two stops in qualifying, so much the better. If not, and you feel the bump could be incresaed some more, add another couple of clicks for the race. If it was too much, you will only find out in the race of course, but you will know for next time!

I would suggest you leave the rebound on minimum until such time as you feel the bump setting is right, then use the same method during the following qualifying/race to adjust the rebound.

[Al Weyman]

Ok i will try something along those lines although I do remember backing them right off at Thruxton last year and the back end just stepped out around church or the corner after causing me to have a high speed off, may of course been oil or something on the track who knows. You can see what happens here: http://www.youtube.com/watch?v=el_9_G7afwA Note how the car is bouncing up and down as compared to here with the dampers set at 2/3rds 1/3rd: http://www.youtube.com/watch?v=Gp0qkLNcYBg

[proutyc]

Phoenix is on the money with how to work your way to the best setup.

I believe the dbl adj QA1 are 24 clicks. I'd recommend doing in 4-5 click movements. This way you find the piont quickly then you can work back and fine tune. This way you could do the bump in one practise session.

When we started we went the wrong way even though I'd been told the above we went about trying to control the rebound thinking that was our cause. When we threw that away and did as we should we ended up seeing over 1sec improvement on on previous best just with the quick bump adjustment. We're now over 3 seconds faster as fine tuned the damper which then enabled us to increase spring rate too.

the way i try to explain to mates I race with over here is that bump was most important for us as too lower bump control just meant we got wheel movement(spring compression) but very limited force actively pushing the tyre into the pavement.

We race total different cars and fight different issues. I gather part of your issue is that the car is under tyred for the engine torque available. I'd also suggest that loss of traction could be both too hard or too soft (damper or spring). This is why its best to work through the above mentioned.

I do the same for finding my optimum spring rate, we're lucky that generally the split doesn't change much front to rear (100lbs).

Hope this makes a little sense.

[Al Weyman]

Thanks for the post. Yes it does make some sense and I do suspect I may be over the top on spring rates. I was experimenting last night and backing off the shockers definitely made it softer on the back so not all down to the springs and there is a lot of weight on the rear of the car with the original glass hatch. I also researched that rebound on a standard shock will always be more than bounce. With the QA1's if you back everything right off are they balanced at more or less zero resistance or is there still more resistance on rebound? I guess a call to Spohn Racing or QA would answer that.

Does anyone have a base line starter setting I can try with the set up I have described. I was thinking maybe starting 5 clicks for bounce 10 clicks for rebound and going from there.

[phoenix]

I would imagine that the rebound damping on your shocks is at least twice (and probably more) the bump damping as standard - without adjusting anything I mean - so I would suggest that as a base setting you leave the rebound setting on the lowest setting and only play with the bump setting. Setting the rebound so much higher than the bump as a starting point will cause you big problems I believe.

I would certainly suggest you get the base damping rates - or at least the base bump/rebound damping ratio - from QA. In fact, they should be able to provide you with figures for bump and rebound for each of the 24 settings available.

As you are suffering poor traction I think it highly likely that you have too much rebound damping, which is causing the inside tyre to be unloaded by the stiff rebound damping preventing the wheel from drooping fast enough.

[Al Weyman]

Funny enough thats how I figured it as well the rebound causeing the wheel to hang and loose traction and to be honest thats what it feels like. It gets halway around the hairpin at Hamilton for example then just kicks out instead of biting and letting me control it in the throttle. At Mallory I can lay down 50 yards of rubber coming out the hairpin and at Donington turning on to the main straight instead of booting it I actually have to feather the throttle till it grips and watch the Toyota Supra in my class just pull away.

[proutyc]

As mentioned above. Pull all the rebound out and work from there

Friend ran these shocks a while ago and I'll see if I can find the shock graphs that QA1 had.

On my car now I almost have 1:1 bump rebound (works for my car, higher downforce light sportscar). We used to try tuning with rebound and ended up the wriong way. took me ages to believe the other way was better. lap times tell the story..... Tyres also look better as you a forcing them into the track surface

Good luck

[andy robinson]

Al, a day testing will transform your car, as you can go out after every adjustment & will be able to feel which directon you need to go.
My car is similar weight & basic layout & im 400 lbs rear spring & 750 front
Im running the car really soft on the rear & hardish on the front which gives it better drive off the corner & to stop the understeer have added bucket loads of castor & camber to give it turn in

[Al Weyman]

I rechecked last night and definitely had them 16 out of 24 clicks bounce and 8 out of 24 rebound the opposite of what it should be so that may be why it felt so wrong. I did go to the Snett 300 pre season t test but lost the gear sychros so that was a waste of time and money and thats what seems to happen I always end up having some problem and dont get round to sorting the settings out. The question I guess I am really asing is what am I looking for when people say it feels right?

[phoenix]

Originally Posted by Al Weyman

16 out of 24 clicks bounce and 8 out of 24 rebound the opposite of what it should be

Al, there is no way you, I or anybody else knows at this stage what the settings should be. Guess and you will probably guess wrong - with 24 setting for both bump and rebound there is just one chance in 576 that you have guessed the right combination!

[phoenix]

Tseting:

Losing the gear synchros at a test is probably better than losing them at the beginning of a race weekend, don't you think?

Of course you need a car that will run problem free for a day to do the testing - but you won't have to drive at 10/10the the whole day to find what doesn't work and arrive at settings which do.

If you start off with rebound at setting one and bump at setting one and just drive the car a few laps, you will get a feel for how the car is. Then adjust the bump settings maybe 3 at a time until the car starts to feel too hard - by which I mean the rear will bang and crash over track irregularities, as what the tyre runs over is transmitted directly into the chassis by the dampers rather than being absorbed by the springs. As you stiffen up the bump you may also get to a point where the car has noticeably more power oversteer than you had with the previous setting. Then you will know/feel the bump is too hard, so back it of 1, 2, or 3 clicks and try it again until it feels nice again.

It is not so easy for a driver to feel the effect of damper rebound settings, unless they are way too soft in which case the car will tend to bounce after a bump. Because of this it's not so easy to describe what 'feelings' you are looking for, but really all you need to do is get to the point that ther rear doesn't bounce after a bump in the track - i.e. the car settles immediately after the bump - and you will be pretty close to optimum.

My advice is to go slowly in adding more rebound damping. If you add too much, the car will get loose at the rear and get wheelspin/poor traction (so maybe oversteer) coming out of corners. After a long corner, like Coram, you may find the chassis slow to roll back to horizontal because of too much rebound damping. Then turning left into Murray with the outside rear spring still 'held' in compression by the damper, the left rear would be lifted clean off the track as the car rolls to the right.

Having invested your hard-earned into the new hardware, I definitely think it is worth the time, effort and money of testing to get the best out of it. Just my opinion, of course.......

[GORDON STREETER]

If I have had to do any suspension test/set up for me or anyone else I would make big changes for a start so you could actually feel what's happening.
Fine tuning takes a fair bit of time as although you might "think" you are going the right way it might only be the fact that you are thrashing round the same track for ages and learning the corners better.
It is sometimes better to let someone else who is a similar driver in a similar car to give it a drive round for an opinion.
What I have found over the years is if a car is really bad at handling for a start smallish adjustments at the track won't make it fantastic and major suspension changes will probably need to be done.

[phoenix]

Originally Posted by GORDON STREETER

If I have had to do any suspension test/set up for me or anyone else I would make big changes for a start so you could actually feel what's happening.

Can't argue with that, except this rear suspension package is supposed to be a tried and tested solution, and we don't know the effect of the range of adjustment on the dampers. It's certain that setting one will not mean zero bump or rebound damping - those settings may give all the damping required.

We do know that setting of 16 bump and 8 rebound is not working, so going full soft first and then working towards the 'doesn't work' settings will presumably find what does work - if the 'kit' is any good in the first place. Koni for one suggest steps of 3 clicks at a time initially.

I agree you could try full soft then full hard to find the extremes - you would then know at least whether softer was better than harder - or the reverse.

[Al Weyman]

Thanks for the input guys really useful. I think at my level of expertise I would have been better off buying single adustables not the doubles if I am honest. I have already tried full soft albiet probably accidentily at Thruxton last year, it was noticibly bouncy on the back and thats when I lost it turning into the straight, the back end just slewed away and I was lawn moving at high speed a somewhat frightening experience. So I have also tried it at 16 and 8 and that seemed very hard and skittish so maybe I will start with 4 and 8 and see how we get on. At least I have an idea what to look out for now.

[phoenix]

In your opening post you said "I cannot also get it to hook up and when I accellerate out of a hairpin for example the rear wheels just light up in a cloud of tyre smoke."

And that was with a setting of 8 on the rebound. Having read the all the above I hope you can see that the rebound is TOO STIFF as it is - so please soften it. Try 4 bump 4 rebound, rather than 4/8 as to use the same rebound setting as last time out makes no sense at all.

[Al Weyman]

I hear what you say and it sounds a plan, I was trying it different than last time out which was 16/8 but 8/8 may be a better starting point as you suggest.

[elitemotorsport]

I used to design racing car dampers for a living, in fact at the time around 25% of the F1 grid were using my designs. It occured to me then that there are only a few people in the world who truely understand what goes on inside and how that relates to driving and engineering that car. A black art if ever there was one.

Being from a club racing background prior to my time in F1 etc, i wanted to explain what i new in as usable way as possible so i wrote an article on damper setup for the 750MC club magazine.

I was going to attach it to this post, but, don't know how (first time poster). You can download it from my website though here (there's a link about half way down the home page).

Any more help please don't hestitate to contact me.

D.

[Al Weyman]

I iwll have a look when I get a minute, shame I have to pay to read but if its worth it ......

[elitemotorsport]

If you can tell me how to attach it to this post i'll add it but can't seem to do it.

All the proceeds from the download goes into my daughters account to help her through her Aerospace degree so its feeding a student if that makes you feel better about it!

[Belatti]

I recommend you to take your dampers to a dynamometer and test them. I dont know in England but here in Argentina there are several teams or car builder/shops that can conduct a test for you or you can even go and use the dyno for yourself (of course, paying some usually modest amount of money)

With that test you may find that going from click 2 to 3 wont give you the same force increment that going from 21 to 22 for example. (speed force curve)
You may also find if the damper heats too much and force decreases with it, if it cavitates of has too much histeresis.
In the test you will also discard any other problem regarding the damper (D shape curve) hydraulic functioning, like lack of oil, etc.

[Al Weyman]

Had the car out at donington on Saturday was curtailed by head gasket failure but got a full wet qually in and 5 laps of the race, its seemed a fair bit better with the new settings however the car simply will not hook up coming out of bends. I will give you an example, the righthander that turns in to the main straight I take in third gear as soon as I tounch the throttle exiting the bend it just lights the rear wheels so I try top (4th) same thing in the meantime the field is pulling away then it finally hooks and I pass them all as it has a lot of power only for the same thing to happen coming out the chichane, its totally ruining the competitiveness of the car. It may be nothing to do with the suspension and maybe I should simply lock the diff up but worried the somewhat wimpy axle on the 3rd gen Camaro compared with the earlier models would cry enough! Any suggestions anyone?

BTW please answer here on dedicated post to the problem http://tentenths.com/forum/showthrea...62#post2887962