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The mkiv Supra Owners Club

Suspension setup 101


Ian C

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OK - I found, after about 4 years, that my shocks are adjustable! :woot:

 

I've had the rears rebuilt, apparently they were all over the place as one was rock hard and the other was buggered etc etc so basically I've got to set the shocks up again from scratch.

 

Now, I know they are about 30-click adjustable, and the guy who rebuilt them ([email protected]) told me to adjust them fully clockwise = maximum stiffness, then back them off to the setting you want. Having done that, my fronts were on 3 out of 30, so uber-stiff! The rears were on like 20 out of 30...

 

Anyway. As I haven't got any experience of this I've set them to 20 all round for now - I can't test it yet as the car is off the road getting the shiny new E-Manage installed but I figured setting them all the same is a good start.

 

My questions are - what happens if you have an imbalanced setup, i.e. fronts stiffer than rears? Or rears stiffer than fronts? Are there any handling advantages to doing this? How far different should they be? Will it e.g. understeer more with stiffer fronts, or be more tail happy with softer rears or what? Fire away :)

 

-Ian

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FWIW IMO after doing a lot of adjusting at the ring, I find too stiff fronts will oversteer big time. There is a fine point where the front settings go from big traction at the rear, to easy and hard to get back oversteer. I always start the other way - soft and build it up as starting hard is dangerous in my experience - big unexpected drifts etc.

If you are on std anti roll bars, chances are your roadholding will start to drop after about 18 of 30 clicks. I find a little soft works better to allow for uneven road surfaces and better off the line traction. I currently use 16 on front and 12 on rears. Hope this helps some, but I expect tastes will differ. While you at it toe out the front a little for more steering feedback.

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FWIW IMO after doing a lot of adjusting at the ring, I find too stiff fronts will oversteer big time. There is a fine point where the front settings go from big traction at the rear, to easy and hard to get back oversteer. I always start the other way - soft and build it up as starting hard is dangerous in my experience - big unexpected drifts etc.

If you are on std anti roll bars, chances are your roadholding will start to drop after about 18 of 30 clicks. I find a little soft works better to allow for uneven road surfaces and better off the line traction. I currently use 16 on front and 12 on rears. Hope this helps some, but I expect tastes will differ. While you at it toe out the front a little for more steering feedback.

 

I'm a little confused by this? Are you saying by increasing front bump stiffness, you increase oversteer? I've not done any suspension testing in the supra but the goes contrary to what is commonly accepted. Decreasing front bump stiffness will increase front grip and shift the balance towards the rear.

 

Either way, Ian, you need to get yourself on the track and have a play mate. Everyone's driving style is different, and dependant on the set-up of your car. What works for someone in their car may not work for you.

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Chief, I'm confused by that too - you've more track experience than me by a long way but I can't comprehend how changing the setup at the front causes the rear to behave differently, unless it's more of a case of "the front now grips more than the rear so I can push harder but when it goes, the back end is now the weakest link"...?

 

Track? Me? I drive Miss Daisy around mate :) The Dussindale roundabouts and the Broadlands business park will be my test ground :devil:

 

And yes, I agree, everyone's setup will be different depending on driving styles etc, I was more after the theory of operation - what usually happens when the fronts are stiffer/the same/softer etc etc...

 

-Ian

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You've got more weight at the front so I'd personally run a harder front, you also want to combat dive under braking which too promotes the use of a harder front...but the harder the front the more prone to sudden and unrecoverable understeer you are. The softer settings usually give you breathing room for mid corner adjustments. I'd run 10 at the front.

 

At the rear your T67 needs about as much mechanical grip as you can get without running so soft that a front wheel lifts. I think you're probably right to start on a 20. Though it needs to be tested at full soft....esp at Santapod ;) :p

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With the Supra I found theory didnt work that well for me, but we gotta remember that suspension is a very personal thing. The front springs are stiffer than the rear, so settings will be your taste according to the roads you drive. My fronts are always stiffer than the rear (my spring rates are 740f and 440r approx). "Theory is only belief and there to be tested" in reference to a given set of circumstances e.g. wheels/tyres/bushes/anti roll bars etc.

I'm with Alex on most of this, but the track is the answer!. When I went above 18 at the front the car got very tail happy on the ring, however with great deal of concentration I was able to do a 8m32sec using the steering carefully to balance the car and have no understeer whatsoever, however Katrin got pretty scared for the first time ever, and i was a little worried myself in case I got a big "unrecoverable" drift. After this I eased the front back. The rear settings were not as crucial as the front I could get away with anything between 10 and 16. Different brands of suspension will vary on settings greatly I suppose click numbers arnt that revelant unless you are using the same as me, HKS hipermax 2.

Track day for you, and it will be worth every penny.

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Damper settings affect TRANSIENT response, not how the car handles once it's taken a set in a corner. Far too much for my typing speeds, I can talk it through on the phone when i am quiet, or buy the Caroll Smith serries of books, which are probably the best, readable, books on car handling written. Tune to Win, Prepare to Win, Engineer to Win and others are in this series, all are worth reading and absorbing.

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Don't say i don't do you any favours. My new race car is on Penske dampers, triple adjustables. Penske do an excellent strip and rebuild and set up manual for them, a lot of the setip stuff will apply to other dampers, so it's worth reading to get a handle on what to do. i have put it on my ftp server at :

 

ftp://ftp.chriswilson.tv/penske/

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Don't say i don't do you any favours. My new race car is on Penske dampers, triple adjustables. Penske do an excellent strip and rebuild and set up manual for them, a lot of the setip stuff will apply to other dampers, so it's worth reading to get a handle on what to do. i have put it on my ftp server at :

 

ftp://ftp.chriswilson.tv/penske/

 

Out of interest Chris, why did you go for Penske? I thought you rated Koni's et al from our European neighbours?

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Not quite sure if you know or not Tony, but Penske are based in the UK.

 

I think that whilst they do have a UK division they are actually a US based company. Don't know much (well anything really!) about their car shocks but in the biking world their shocks are very well respected (right up their with Ohlins W.P wtc).

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Out of interest Chris, why did you go for Penske? I thought you rated Koni's et al from our European neighbours?

They were already on the car, but they are up there with Dynamics, Koni competition, European Ohlins et al, so quite happy to stick with them. The other Zeus has Proflex on it, so it will be interesting to compare them. The Penske have a huge user changeable range of valving available, so I can play and play :) The Penske are triple adjustable, the proflex double adjustable, so yet more knobs to twiddle!

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You twiddle with your knobs, I'll twiddle with Allen ;) Anyway, having only one setting that controls both bump and rebound, that makes it easier for a noob like myself I think. From what I've read and thought about I want:

 

As stiff as possible, BUT:

Not so stiff it skips over bumps

Not so stiff at the rear that the rear tyres skip under heavy braking

Not so stiff at the front that I understeer on turn-in

As slack at the rear as I can get away with to give more grip under acceleration

 

-Ian

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I was looking at the dampers we make in house today. You'd be very suprised at how simple they actually are.

One of my previous employers used to use a fully active susp. car when testing as it enabled instantaneous, and infinite adjustment, and enabled us to test aero loads at specific ride heights. After the test we could then transfer those settings to a hydraulic damper.

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