Handling Challenges

[GraemeI 41]

Hi All, back again for some insights, wisdom and possible abusive commentary

I had some challenges with a wayward rear end when I got the car back in August 2017, which didn't feel right, so ended up with adjustable LCA's new PS4's and a good alignment job, and whilst that improved it a lot, I always felt like it was still way to eager to step out unpredictably, or just very early - for what is essentially quite a low torque output.  Much forum reading and talking to people suggested tail happy was a normal character trait, so I chose to live with it.

Today, I went out to CAT Driver training and did half a day with Colin Hoad, and the short version is he didn't even want to do the handling circuit at high speed in my car after testing on the skid pad, as it is too flighty at the rear.  You can push the back out on demand even when doing push on understeer with just 5% more throttle!  In Colin's words, he said that isn't even possible in a 600bhp Ferrari 488 with all the traction turned off, so it shouldn't be happening in a GT86!!

So, with that background out the way, I am looking to go get the car's geo set up again, but was wondering if it was worth doing something with the suspension at the same time (or just before), as it's going to get very expensive to keep re-doing these things   Colin's comment was the car is pretty sorted apart from the rear end, so no (other) weird suspension or handling traits, but I am looking to get a slightly more compliant ride for road use and be able to stiffen it up for the occasional TSS or track day, which I can't do with the current setup.

What I don't want to do is mess things up even more, so struggling with leaving as is or putting some Flex A's or similar in, then getting the geo dialled in?

What do you vastly more experienced people think? 

[Lauren 2259]

Just put more toe in at the rear. That'll make it more stable. 0.15 seconds toe in at the rear is slightly more than the book states but it's what my car has due to the LCA being fitted with stock track ends. It makes it neutral even at high speeds in the dry. 

[Church 209]

Can you post printout or at least numbers of your current alignment? At least front and rear camber and toe?

(and yes, as Lauren mentioned, it's common for RWD cars alignment to gain more stability with slight toe-in in rear. (helped me some time ago vs stock alignment too for similar goal of more stability and to allow quicker open throttle going out of curves). Worth not going too overboard with that though, as toe affects more badly tire wear, then eg. camber)

[Lauren 2259]

Here's mine: 

7 July 2017 Geo setup GT86 by Lauren Blighton, on Flickr

[GraemeI 41]

3 minutes ago, Church said:

Can you post printout or at least numbers of your current alignment? At least front and rear camber and toe?

In theory, yes, but this is me you're talking to

[GraemeI 41]

I tried to get more camber on the front, but they ran out of adjustment on the camber bolts and then tried to balance front to rear, so they kept the rear lower as well. 

My original request was for 1.5-2 degrees front and 1.5-1.75 rear, but as you can see, that didn't happen. 

They also had some fun trying to line up the front and rear and left to right - as it wasn't completely lined up - this also contributed to not being able to adjust the camber as much.  See below for this:

 

[Lauren 2259]

If I'm reading it right and it's a bloody nightmare the 'actual', which I guess is what you actually have after they've done it means you've got toe out on the rear and it's not even equalised. Take it somewhere else next time. 

[GraemeI 41]

8 minutes ago, Lauren said:

Here's mine: 

7 July 2017 Geo setup GT86 by Lauren Blighton, on Flickr

Good grief - the -3.37 must have been fun with tyres beforehand   Looks good now!

I also found out today that my driving style also massively affects how the car should be setup.  Apparently I trail brake quite a lot, so need to set up for default understeer (not my favourite!!), so it's neutral pushing towards slightly oversteer'y' at and near the limits (much better for track, but I won't be doing that on the road, so am torn a little )

[GraemeI 41]

6 minutes ago, Lauren said:

If I'm reading it right and it's a bloody nightmare the 'actual', which I guess is what you actually have after they've done it means you've got toe out on the rear and it's not even equalised. Take it somewhere else next time. 

It's 0.05 and 0.03 on the rear, which sounds minimal, but compared to your -0.15, it's a large multiple out!

I have been recommended to see Chris Franklin at Center Gravity as they tune the car to your driving characteristics by testing it beforehand and also checking all components etc before even trying to check the geo.  Anyone else heard of, or used them?

 

[Lauren 2259]

The before was after it had a fully polybush kit and SPA rear lower arms fitted. I never drove it like that, it's just how it was before they set it up, so the car never went on the road like that!

Honestly my setup doesn't oversteer quite like I hope it would, but it's a very fast neutral setup, which most would prefer. I would like 0.05 on the rear toe in really, maybe 0.10 would be the sweet spot, but I'd need to fit aftermarket longer track rod ends to achieve this. 

I am a trail braking queen, but I like to really rotate the rear and I absolutely loathe any understeer at all. I'm happy with the car being really pointy and a bit loose at the rear. As it is at the moment it doesn't understeer at all and is very pointy, but it's still pretty stable at the rear. In the wet it's a bit more lively but you'd expect that. 

Toe and thrust angle is far more critical to get equalised than camber is. Castor is even less relevant, stock settings are fine for that. If you want to get 2 degrees of negative camber at the front you'll need coilovers or pillowball top mounts (which are what coilovers tend to have of course). Adjustable rear lower arms and longer track rod ends are needed for the rear. If that's what you want to do. 

But honestly, getting the car square and getting some toe in on the rear will basically sort your problems, so there is no need to spend any money to make an appreciable difference. 

 

[Deacon 1357]

7 minutes ago, GraemeI said:

It's 0.05 and 0.03 on the rear, which sounds minimal, but compared to your -0.15, it's a large multiple out!

I have been recommended to see Chris Franklin at Center Gravity as they tune the car to your driving characteristics by testing it beforehand and also checking all components etc before even trying to check the geo.  Anyone else heard of, or used them?

 

I've used Chris for a previous car. He's very good but also very pricey. What you do get with Centre Gravity as you said is that Chris takes your car out with you before he does any work to see how it is, then discusses what you want to get from the car to inform his set up.  Wheels in Motion that you used are also supposed to be very good too though but I'd imagine do either what the machine says or what you ask for rather than the whole experience you get from CG. 

Maybe worth having a chat with Rogue Motorsport too (speak to Matt and tell him Jeff recommended him). They race 86's and can do any necessary alignment work too. 

[GraemeI 41]

Thanks Lauren, all makes perfect sense.

I despise understeer too, but when the car gets loose at the rear at less than 55mph on a simple chicane and lets go like someone dropped oil on the back tyres, it's not a lot of fun, so I need to sort that out for sure.  If Colin hadn't basically refused to run the handling course today, I could have written it off to me either being a chicken or inexperienced with the car, but when someone who does it for a living tells me it's bad, I try to listen

I also take on board your comments on not needing to spend any money on it - that is always a good starting point! 

I do still want to address my compliance issues on the road (want it slightly more cushioned basically) and also the ability to stiffen it up a bit more on track, so that is what led me to think about some coil-overs (with said pillow-ball top mounts ).  Already have the adjustable LCA's, but not track rods yet.

My biggest concern is that I just don't know if they will be better or worse than my current setup, so reluctant to drop that much money on them to find out afterwards!

My rating of the stock car suspension (12-16) was a bit chattery on medium speed corrugated roads, and a bit harsh on bumps. The newer 17 model fixed most of this, but still slightly harsh on unexpected bumps.  My car (with 1kg per corner lighter wheels) and the Eibach Pro-Kit springs has no chatter and not very harsh on unexpected bumps either as they are progressive rate springs so just wind up a bit more, but with the lighter wheels it doesn't jar as much.

So, my idea was possibly lighter wheels (money and availability issues!) with the Flex A's and maybe marginally softer spring rates (Lauren's spring rate ftw!) and then see if that gives me what I want.  But back to just not knowing the outcome!  Argh!!  Who said modifying cars was a good idea!!!???

 

[Lauren 2259]

Well, there's only one way to find out! I'd honestly say just get your geo sorted as it sounds like it's a liability at the moment, then sleep on it and see what you want to do in terms of further mods like coilovers. Mine is extensively modified when it comes to suspension but I've done it one step at a time (well sort of!). 

[GraemeI 41]

6 minutes ago, Deacon said:

I've used Chris for a previous car. He's very good but also very pricey. What you do get with Centre Gravity as you said is that Chris takes your car out with you before he does any work to see how it is, then discusses what you want to get from the car to inform his set up.  Wheels in Motion that you used are also supposed to be very good too though but I'd imagine do either what the machine says or what you ask for rather than the whole experience you get from CG. 

Maybe worth having a chat with Rogue Motorsport too (speak to Matt and tell him Jeff recommended him). They race 86's and can do any necessary alignment work too. 

Cheers Jeff, sounds about right.  I always expect 'very good' to come with 'pricey'   Colin was the same!

Guys at Wheels in Motion knew their stuff, but as you say, didn't ask any of those sorts of questions or anything, so you get a mix of what you want with some best practice 'don't mess with the basics' thrown in

May well give Rogue a call too - seen them in the 750MC Sports Specials with the Xenon a few times

[Deacon 1357]

7 minutes ago, GraemeI said:

Cheers Jeff, sounds about right.  I always expect 'very good' to come with 'pricey'   Colin was the same!

Guys at Wheels in Motion knew their stuff, but as you say, didn't ask any of those sorts of questions or anything, so you get a mix of what you want with some best practice 'don't mess with the basics' thrown in

May well give Rogue a call too - seen them in the 750MC Sports Specials with the Xenon a few times

As an idea the last quote I had from CG a couple of years back was £600.

Where abouts are you based @GraemeI? 

[Varelco 211]

Any changes to the suspension other the LCAs? Springs anti roll bars etc?

[Church 209]

2 hours ago, GraemeI said:

My original request was for 1.5-2 degrees front and 1.5-1.75 rear, but as you can see, that didn't happen.

With single set of camberbolts -1.5 is about max (at stock height. lowering adds some -0.2 more). With camberbolts in both holes total front camber ~ -2.2 to -2.3 (-2.5 if lowered). If you add eccentric powerflex front lca bushing in addition to camberbolts in both strut lower mountholes, total front camber can be upped to -3 degrees. For more then that (or if one doesn't use PF bushings, or has just one set of camberbolts) - one needs top camberplates or slotted strut mounts.

BTW, adding extra camber in front won't eliminate extra oversteer. To change grip bias for less oversteery, it would be rather opposite, with added grip rear (in this case - more negative camber, to compensate tire flex in curve on track due side-Gs) or reduces grip in front. I'd rather use some toe-in in rear for more rear stability ..

.. BUT! If i interpret your printout right (more used to printouts with rear axle alignments placed below ), Rear axle > Toe > left 0dg05' right 0dg03' total 0dg0.8'already is slight toe in? (positive values were toe-in, negative toe-out, right?) so imho it should already be better of stock's 0 toe in rear aswell. And even with everything stock my car seemed a bit less oversteery, vs what you describe, that even 5% extra throttle after understeer could make it snap oversteer, i needed to shift grip to front much more for oversteer with throttle in long curves for rear grip loss. And you say that competent driver also observed that excessive oversteer. I'm slightly at loss here. :/ Yes, even more toe-in should add stability, but imho it shouldn't be that bad as you describe even with toe-in you have now. Another way for quick add of rear grip even without redoing alignment would be lessening air pressure in rear tires. But still, imho it shouldn't be as bad.

As Varelco asked - do you have changes to different stiffness roll bars or to any other suspension bits, except alignment? Car is still NA? Tire pressures are even? No suspension bits had been worn/bent?

[KevinA 695]

Some good advice here, I tried 0 toe on the rear and it was way to lively and prevented me getting on the gas early. Adding some toe in soon gave a better balance, I don't mind a little understeer as you can use the throttle to balance your grip levels.

Not the easiest of problems to get right, after all we are playing with road cars on track 

[GraemeI 41]

7 hours ago, Deacon said:

As an idea the last quote I had from CG a couple of years back was £600.

Where abouts are you based @GraemeI? 

*sucks in breath sharply* Good grief, that woke me up!

I am in Wendover, Buckinghamshire, just South East of Aylesbury.

 

6 hours ago, Varelco said:

Any changes to the suspension other the LCAs? Springs anti roll bars etc?

Only changes (that I know of!) are lowering springs which were already on the car with the camber bolts and then the LCA's which I got fitted when I saw how far out my rear camber was.  That was done prior to the print out above - you can see in the one below how bad the camber was shot on the rear - one positive and one negative, not to mention the ridiculous toe on the rear!

5 hours ago, Church said:

.. BUT! If i interpret your printout right (more used to printouts with rear axle alignments placed below ), Rear axle > Toe > left 0dg05' right 0dg03' total 0dg0.8'already is slight toe in? (positive values were toe-in, negative toe-out, right?) so imho it should already be better of stock's 0 toe in rear aswell. And even with everything stock my car seemed a bit less oversteery, vs what you describe, that even 5% extra throttle after understeer could make it snap oversteer, i needed to shift grip to front much more for oversteer with throttle in long curves for rear grip loss. And you say that competent driver also observed that excessive oversteer. I'm slightly at loss here. :/ Yes, even more toe-in should add stability, but imho it shouldn't be that bad as you describe even with toe-in you have now. Another way for quick add of rear grip even without redoing alignment would be lessening air pressure in rear tires. But still, imho it shouldn't be as bad.

As Varelco asked - do you have changes to different stiffness roll bars or to any other suspension bits, except alignment? Car is still NA? Tire pressures are even? No suspension bits had been worn/bent?

As far as I know you are correct - i.e. positive is toe in and negative is toe out? That suggests I have slight toe in, which is what the guys said when they did it - the idea was to give some more rear stability with a little toe in.  If that isn't it, then something else must be wrong.  I wonder if the rear end took a hit at some point to make the camber and toe go so far out in the first place?

To answer your other questions, yes car still NA, tyre pressures even, and nothing worn, bent or broken that anyone has found so far.....

We first felt it with a 30mph rapid lane change which sent the rear TC mental.  

Very odd, and it's a mystery!!  Lovely! 

[GraemeI 41]

1 hour ago, KevinA said:

Some good advice here, I tried 0 toe on the rear and it was way to lively and prevented me getting on the gas early. Adding some toe in soon gave a better balance, I don't mind a little understeer as you can use the throttle to balance your grip levels.

Not the easiest of problems to get right, after all we are playing with road cars on track 

You're not kidding Kevin! Mind you, right now, I can't even get the road car to behave on the road!!!  In it's current state, just the slightest provocation of lift, throttle or even gear change sets it off

How much toe did you put in to stabilise things?  More than happy to balance on the throttle  

[Church 209]

Graemel: you can increase toe-in in rear, to eg. -0.2dg total, try lesser tire pressures in rear, try softer rollbar rear, try something like this, but imho still there is something wrong, that should be fixed. Just that my "remote diagnostic" skills and suspension knowledge are too low to find out what  can be wrong. Just knowing that for others even stock, or with alignment you have, car shouldn't be that traction-less in rear, and neutral margin between understeer plow and rear traction loss usually is much wider. About the last mad idea, that maybe something wrong with diff, that eases loosing traction in rear, but i doubt it. One can try to diagnose at dealership, but i somewhat pessimistically doubt their competency on handling at extremes or diagnosing mundane problems (except if with subsequent 'replace everything one-by-one untill fixed') or brushing problem off in general 'driving normally on roads it's ok', 'we don't endorse track abuse'.

In this case i'd ask someone that knows better :). Be it visiting some well spoken of performance suspension shop (eg. mentioned Chris@CG), or eg. asking on this thread or PMing Racecomp Engineering directly with describing experienced, symptoms, tell current alignment numbers and ask for advise/what to check.

Of course from high probability reasons i could have included wrong driving inputs, but cited Colin Hoad's experiences during CAT training probably strikes that out. But you still can go to some meat/track day and ask other twin owner to check or have a go in other twin.

[Church 209]

Oh. Last guess is if really misinterpret, and said toe settings ARE toe-out, like Lauren said (but imho he also may have erred with "If I'm reading it right and it's a bloody nightmare the 'actual', which I guess is what you actually have after they've done it means you've got toe out on the rear and it's not even equalised."), then i'd completely understand such behaviour of rear tending to step-out (btw, one of valid tuning ways for underpowered NA specialised drift setups, to intentionally reduce rear traction/ease of drifting. Not needed for high power forced induction driftmachines though. But i doubt it :/)

Well, one can always check by bringing car to another shop with other alignment machine, but it's still more $$ and probably wasted, due me thinking that it's not the case, and it actually being toe-in.

Oh. And last-last guess is miscalibrated alignment rig in shop you've been to. But that's also among lesser possibilities.

[Lauren 2259]

- = toe in + = toe out. He's got toe out on the rear. Works the same as camber i.e., - = negative camber + = positive camber. 

[Church 209]

Hmm, some googling.

"The toe angle identifies the direction of the tires compared to the centerline of the vehicle"

"Positive toe, or toe in, is the front of the wheel pointing towards the centerline of the vehicle."

"Toe is a measurement of how much the front and/or rear wheels are turned in or out from a straight-ahead position. When the wheels are turned in, toe is positive (+). When the wheels are turned out, toe is negative (-)."

"The toe angle identifies the exact direction the tires are pointed compared to the centerline of the vehicle when viewed from directly above. Toe is expressed in either degrees or fractions-of-an-inch, and an axle is said to have positive toe-in when imaginary lines running through the centerlines of the tires intersect in front of the vehicle and have negative toe-out when they diverge."

"Toe-In (Positive Toe) exists where the distance of the front of both rear wheels on the common rear axle is closer together than the rear of the same rear wheels.

Toe-Out (Negative Toe) exists when the distance between the front of both rear wheels on the common rear axle is farther apart than the rear of the same rear wheels."

=============

Hmm, though on some other printouts with schematics, i see angles between centerline and wheel drawn in opposite for front and rear. Angle from above for front wheels, and from below for rears. Damn, it's confusing. SO WHICH IS IT?!!

[Lauren 2259]

 I didn't use google, I used to set up geommetry on Elises and Exiges many, many years ago. Google seems to make it a tad confusing. 

Just to add, instability at the rear is caused by toe out, not toe in.