Robs S/C GT86 Project

[rob275 1817]

Fitted the Cusco headlight adjuster on Sunday but I haven't actually been out at night to see if it makes any difference yet.

Made it roughly 10mm shorter as was suggested for a 30mm drop but i'm sure its better than it was. Quite a fiddly crusade on my driveway and I got covered in sand in the process, my worst nightmare. This is why I never work on my car. 

[Mark@Abbey M/S 235]

Just a rear bar upgrade is what I advise everyone seems pretty happy with this set up. Stay away from anything to big on the rear bar as it makes the car too stiff on the rear lifts an inside rear wheel loosing grip

calms the turn in under-steer but isnt too stiff to cause the car to lift a rear wheel , running without an uprated front bar helps front grip as running a larger bar will cause the grip to be removed from the inner front wheel when the car tries to roll.

 

[Ade 517]

It depends on the rest of the suspension though. A 16mm bar worked nicely on the back of a stock gt86, but when you start adding stiffer bushes and different coilovers with very different wheel frequencies, it becomes a bit of trial and error. 

General rules. If car understeers; add more rear roll stiffness, if car oversteers; add more front roll stiffness. 

Adding camber can affect balance but it should be set to give the best grip and tyre temperature across the tread then evaluate the balance of the car and adjust roll stiffness as necessary. 

 

 

[rob275 1817]

Mine currently understeers a tad so perhaps worth trying a rear bar

[Ade 517]

1 minute ago, rob275 said:

Mine currently understeers a tad so perhaps worth trying a rear bar

Whats your front camber?

6kg front and back right?

[rob275 1817]

Just now, Ade said:

Whats your front camber?

6kg front and back right?

I have the same spring rates as @Lauren my front camber I don't actually know what it is at the moment I was going to get it on Marks hunter before the trackday in Feb but ran out of time and never got round to it lol.

My initial setup was -1.5deg iirc

[Ade 517]

I actually felt like mine understeered less than Lauren's but to be sure I've have to drive it.. I've got -2.7 up front so that might be the reason.

[Lauren 2259]

I think you'd have to drive it Ade. I certainly couldn't tell from your's as the grip dominated really. FWIW having driven cars with a 6/6kg setup tend to understeer more than the 5/6kg setup. 

Rob you should definitely go 2 degrees negative up front. 

[Ade 517]

I think you'd have to drive it Ade. I certainly couldn't tell from your's as the grip dominated really. FWIW having driven cars with a 6/6kg setup tend to understeer more than the 5/6kg setup. 

Rob you should definitely go 2 degrees negative up front. 

Spring rate affects balance but running lots of camber up front (I run -2.7) also adds grip which makes it more neutral. I mean stock gt86 was pretty bad but I find the ohlins with lots of camber more balanced. It'll certainly understeer if you push too hard and don't use the brakes to keep weight over the front.

[Lauren 2259]

Sure, though balance is what we are talking about. And yes camber certainly makes a difference, but it's how you drive it of course. Go in too fast and put on too much steering and the laws of physics tend to apply, so it's a lot about technique as well of course. The stock car certainly understeers more, which is likely due to the lack of negative camber on the front. You can drive around this to minimise this and it is worth learning how to do it which requires work on trail braking. A car with more negative camber suffers far less and so it is easier to minimise understeer, but trail braking will always be required, because as you say, it's about getting the weight over the front and unloading the rear to help the car rotate. 

[Mark@Abbey M/S 235]

rear toe/camber also makes a difference to understeer as well we have found.

A lot of camber on the front makes a car not nice on our bad roads, a rear bar stops the understeer but allows a reasonable amount of front camber to be run that doesn't make the car tram line to much.

[Ade 517]

20 minutes ago, Mark@Abbey M/S said:

rear toe/camber also makes a difference to understeer as well we have found.

A lot of camber on the front makes a car not nice on our bad roads, a rear bar stops the understeer but allows a reasonable amount of front camber to be run that doesn't make the car tram line to much.

I havent had an issue tram lining getting worse with added negative camber. I had camber set to 0degrees, -2degress, -2.5degress and -2.7degrees. Difference between 0 and -2.5 was minimal. 

I dont do a lot of road miles, but inside wear will likely be an issue if you do.

Not arguing adding camber is a the better option, just pointing out that a 6kg/6kg setup with lots of camber up front doesn't under steer as much as a setup with low front camber - its obvious really. 0deg up front was worse than stock in terms of balance. 

There are two trains of thought regarding suspension. The old school English way which is soft springs and big bars and the modern approach which uses springs to control roll stiffness. Both have pros and cons:

Roll bars reduce wheel independence  which means you get reduced loading on the opposite side over bumps. Worse case would result in wheel hop. 

Stiff springs wear out dampers quicker due to the higher requirement for damping, make the ride stiff, reduce droop travel ect.

 

One thing people never consider when adding or reducing spring rates is the effect it has on the bump and rebound travel. Putting softer springs at one end without appropriately increasing preload will reduce the available bump. The effect could be riding the hard bumpstops in corner which is effectively adding roll stiffness to the front and making understeer worse than a slightly stiffer spring.  

I'm not saying thats the case for Laurens setup of course.

The bumpstops are often an integral part of suspension design. Here an illustation for how the bumpstops are used on the ohlins road and track coilover for the MX5

In corners its resting on the bumpstops. Adding a softer spring here without additional preload would mean it hits the bumpstop sooner effectively adding roll stiffness and negate the desired effect of a softer spring. 

Its a complicated subject and very much a trial and error. I liked the stock setup with 16mm roll bars to be honest but there was a little wheel hop on the bigger bumps. Lot of different opinions on the forum, mine being one of them. 

There is a reason chassis engineers exist and good ones are paid very well. 

 

[Mark@Abbey M/S 235]

I don't know what I bother sometime's Ade.

I can drive pretty well, been around race cars for a long time proper race cars as well , listened to a lot of engineers talking about stuff , spent sometime building dampers.

I was only just adding my 1 pence worth what we have found that works and doesn't on a GT86 most people don't what to know why it works just want something that works.

1st thing on a GT86 I feel is go and have some tuition your then understand how the car works and what it is telling you.

Thanks

 

(sorry Rob for hi jacking your thread)

 

 

 

[S18 RSG 429]

At the end of the day, an opinion is just that, an opinion. No opinion (without definitive proof through testing) carries more weight than any other, because there are far too many factors to consider. The main factor being that everybody drives differently. What works for one person might cause too much understeer for someone else, or might be too stiff for someone else. It's all about finding what works for you.

Let's be honest, if there was one setup that showed up as the "best" through thorough testing, I'm sure we'd all gravitate towards that.

Fact is, nobody on here, traders included, has even scratched the surface when it comes to testing setups for this car, which is why there are so many opinions being thrown around. There is no concrete evidence proving one way or the other.

My background in engineering qualifies me to understand the theory behind how suspension works, but at the same time, I'm not hugely experienced setting up car suspension, so my input will be purely theory based, but here goes:

With regards to which ARB/spring rate/alignment setup is best, you guys need to remember that all aspects being mentioned have a direct impact on each other. Running a lot of negative camber at the front, for example, may suit stock ARB's as you're getting your turn in response and under/oversteer balance through alignment, whereas running a low amount of negative camber may benefit from a thicker rear bar to aid the reduction of understeer that way. Same thing with spring rates. Running an equal F/R spring rate may benefit from a thicker rear ARB, whereas running higher rear spring rate may be better suited to the stock ARB's.

This kind of discussion requires far too many caveats for there to be any reasonable conclusion. It's best discussed on a case-by-case basis, rather than a general blanket statement.

[Ade 517]

40 minutes ago, S18 RSG said:

At the end of the day, an opinion are just that, an opinion. No opinion (without definitive proof through testing) carries more weight than any other, because there are far too many factors to consider. The main factor being that everybody drives differently. What works for one person might cause too much understeer for someone else, or might be too stiff for someone else. It's all about finding what works for you.

Let's be honest, if there was one setup that showed up as the "best" through thorough testing, I'm sure we'd all gravitate towards that.

Fact is, nobody on here, traders included, has even scratched the surface when it comes to testing setups for this car, which is why there are so many opinions being thrown around. There is no concrete evidence proving one way or the other.

My background in engineering qualifies me to understand the theory behind how suspension works, but at the same time, I'm not hugely experienced setting up car suspension, so my input will be purely theory based, but here goes:

With regards to which ARB/spring rate/alignment setup is best, you guys need to remember that all aspects being mentioned have a direct impact on each other. Running a lot of negative camber at the front, for example, may suit stock ARB's as you're getting your turn in response and under/oversteer balance through alignment, whereas running a low amount of negative camber may benefit from a thicker rear bar to aid the reduction of understeer that way. Same thing with spring rates. Running an equal F/R spring rate may benefit from a thicker rear ARB, whereas running higher rear spring rate may be better suited to the stock ARB's.

This kind of discussion requires far too many caveats for there to be any reasonable conclusion. It's best discussed on a case-by-case basis, rather than a general blanket statement.

Exactly. Everything effects everything! Wasnt trying to start a great debate. Your pretty happy with your roll bar setup and that all that matters!

P.s. Sorry Rob

[KevinA 695]

Totally agree !! Everybody drives differently and likes various aspects of good handling.

But good debate none the less  

[S18 RSG 429]

4 minutes ago, KevinA said:

Totally agree !! Everybody drives differently and likes various aspects of good handling.

But good debate none the less  

There's nothing I like more than a good debate. Especially a mature debate

[rob275 1817]

Can I haz my build thread back?  

Headlights are a lot better now, had a chat with Charlie @CGR Automotive and think he's got everything he needs from me with regards to the replacement exhaust now so should happen soon. 

Once that's all sorted i'll take everything that's been said above and try some bits out! 

[Special K 442]

On 13/10/2016 at 10:25 AM, Ade said:

I havent had an issue tram lining getting worse with added negative camber. I had camber set to 0degrees, -2degress, -2.5degress and -2.7degrees. Difference between 0 and -2.5 was minimal. 

I dont do a lot of road miles, but inside wear will likely be an issue if you do.

Not arguing adding camber is a the better option, just pointing out that a 6kg/6kg setup with lots of camber up front doesn't under steer as much as a setup with low front camber - its obvious really. 0deg up front was worse than stock in terms of balance. 

There are two trains of thought regarding suspension. The old school English way which is soft springs and big bars and the modern approach which uses springs to control roll stiffness. Both have pros and cons:

Roll bars reduce wheel independence  which means you get reduced loading on the opposite side over bumps. Worse case would result in wheel hop. 

Stiff springs wear out dampers quicker due to the higher requirement for damping, make the ride stiff, reduce droop travel ect.

 

One thing people never consider when adding or reducing spring rates is the effect it has on the bump and rebound travel. Putting softer springs at one end without appropriately increasing preload will reduce the available bump. The effect could be riding the hard bumpstops in corner which is effectively adding roll stiffness to the front and making understeer worse than a slightly stiffer spring.  

I'm not saying thats the case for Laurens setup of course.

The bumpstops are often an integral part of suspension design. Here an illustation for how the bumpstops are used on the ohlins road and track coilover for the MX5

In corners its resting on the bumpstops. Adding a softer spring here without additional preload would mean it hits the bumpstop sooner effectively adding roll stiffness and negate the desired effect of a softer spring. 

Its a complicated subject and very much a trial and error. I liked the stock setup with 16mm roll bars to be honest but there was a little wheel hop on the bigger bumps. Lot of different opinions on the forum, mine being one of them. 

There is a reason chassis engineers exist and good ones are paid very well.

Ade,

I run 2.5neg on all four corners. Road. Track. It is as solid as a rock. I point it and it nails it - I cannot believe you are saying that negative camber on GT86 ".. it makes no difference . ."

You're running Ohlins. Probably the best dampers for reactive suspension you can buy  (according to LFA and others). But they are yesteryear, in my opinion.

It's a pity you haven't tried something a little more proactive, like the Tein EDFC system. Lauren's system is middle-of-the-road (as is mine!!) but neither of us have the roadcraft or the trackcraft to take it to its ultimate.

And EDFC is the way that suspensions have (and will) evolve. Indeed, you only have to review the current supercars to see how it has developed. It is 'standard'  - bollixing about with rollbar diameters is (to my mind) equivalent to cut/shut the chassis by 2cm.

Your theory is excellent - but I believe a little behind the times, as the bumpstops (merely as one example)  were modified by some of us two years ago following a Millbrook test day.

 Adjusting rollbar tension (diameters) is the easiest way to cause grief and distress, in my opinion. We GT86DC owners are not F1 chassis engineers and we cannot simulate the effects. 'Trial and error' < I quote you > costs bent motorcars and bent lives, and is not what I recommend on any club Forum

Mebbe I read this wrong - perhaps you ARE a serious player. In which case perhaps we can meet up at a trackday next year, or at Snet this weekend, and you can evaluate a truly 'set-up' GT86 - err, with knobs on . . 

However . . at the risk of incurring Tein's wrath, can I mention we are looking at a development.

A 'Cortana' version of EDFC. Voice controlled. One of the most exciting projects I have been involved in. 

It will actually recognise ".... OH, NO . . . . FSCK!!!!..."

 

Spec K

[Ade 517]

I said it made hardly no difference to tram lining. I am advocating that a square spring rate setup with plenty of camber up front gives a nice balance in my opinion.

I'm probably going to be at Bedford on the 2nd December.

[Lauren 2259]

22 minutes ago, Special K said:

 

It's a pity you haven't tried something a little more proactive, like the Tein EDFC system. Lauren's system is middle-of-the-road (as is mine!!) but neither of us have the roadcraft or the trackcraft to take it to its ultimate.

Speak for yourself! I think I'm about the only one with EDFC that has taken a lot of time to work it out and more importantly work out what works. To that end I programmed it to my own parameters which many other's have used as a starting point. 

I honestly don't think I can get any more out of it, but that's okay as I'm very happy with how my car handles. There really is nothing to change which is why I haven't added bigger ARB's or even any bracing as such. If it ain't broke..... I have spent many hours trying different setups, at the time I had a really wicked commute with clear roads and I was able to compare and contrast different settings to find a means to get the best out of it. Also I've done over 60K on that suspension. 

There's a reason why, when owners get EDFC I'm inevitably tasked with setting it up. This is because I have spent a lot of time with Yukiko at TEIN and we have had many discussions about setup. Plus I seem to be one of the few that can programme it! 

[Sideways? 33]

Rob, can you do some more building so we can move on from talk of suspension setup...? (thrilling as it is...)

U can haz yo Fred bak bruv, take it!!

Sent from my E6553 using Tapatalk

[Ade 517]

He needs to drop in a v10

[Minion 132]

10 minutes ago, Ade said:

He needs to drop in a v10

Meh, I'd be happy with this...

[rob275 1817]

11 hours ago, Sideways? said:

Rob, can you do some more building so we can move on from talk of suspension setup...? (thrilling as it is...)

U can haz yo Fred bak bruv, take it!!

Sent from my E6553 using Tapatalk

I do have a present arriving next week But @Ade it's not a v10. If Jordans car is anything to go by it'd never get done