Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: Muroman on 09 July 2018, 08:02:05

Title: Understeer
Post by: Muroman on 09 July 2018, 08:02:05
Hellou, how to kill understeer?

Last winter I changed new Bilstein B8 shocks on front, LSD diff, front wishbone bushes and rear subframe(only the big bushes) bushes to poly bushes.

And now as the summer came the car feels much better but there also came this massive understeering....

Also the car has Stock springs front and back and also stock rear air shocks.
Title: Re: Understeer
Post by: Doctor Gollum on 09 July 2018, 09:32:50
Swap the B8s and vertical bushes out :y
Title: Re: Understeer
Post by: Muroman on 09 July 2018, 14:26:30
Is there other ways, as I hoped for something that could be done by tools. Maybe camber and toes?

Which shocks you suggest? And which bushes?
Title: Re: Understeer
Post by: Doctor Gollum on 09 July 2018, 14:35:54
Standard GM vertical bushes, Sachs shocks with Pedders HD Monaro top mounts. Basically you need to soften the front end slightly to stop it washing out of the corners ;)

What toe/camber are you running? And what wheels/tyres?

Full poly set up should be ZERO TOE with 1°10' camber.

Check this first and report back :y
Title: Re: Understeer
Post by: Muroman on 09 July 2018, 16:06:18
I have those Elite Intra Alloys 7.5inch wide, tires Kumho 235/45 17'

I have ~2mm toe in as it helped with the car going straight on these shi**y roads that we have in Finland. It was pulling left or right on roads that have bad trails. So I guess I can't fix this if there isn't another way to stop the car jumping from another lane to other  :-\

Camber was hard to measure but the most approx measure was a little over 1°
Title: Re: Understeer
Post by: Doctor Gollum on 09 July 2018, 16:23:54
Those tyres won't be helping.

Mine was on 245/40/18 Goodyear Eagle Assym 2s with Irmscher Stila wheels, Sachs shocks, Plod springs all round, Pedders rear subframe bushes and solid diff mounts, Rear self levelling, Pedders top mounts, Powerflex front bushes and Powerflex Black Sierra bushes as the vertical bush. Geometry was set as zero toe and camber as above.

I don't recall it understeering much, but zero toe does make it a touch vague straight ahead ( this is an insurmountable side effect of having a recirculating ball steering box as there's always a dead spot unless you are turning), but it used to turn in crisply. I enjoyed driving that car hard.

My Elite had B4s with Pedders top mounts, Irmscher springs all round, Powerflex front bushes with standard vertical bushes, Pedders rear subframe bushes and solid diff mounts, and Irmscher rear shocks with the same wheels/tyres.

That had standard toe/camber and handled as well, but felt different because it was lowered and due to the vertical bushes being stock, the front end was a bit more forgiving...
Title: Re: Understeer
Post by: Muroman on 09 July 2018, 17:17:42
Okay that is good reference  :y

I think my camber is close to the default but I'll start by re-adjusting those and try to see what that does. If no help, then toe adjust and if it still stays bad I'll do something else
Title: Re: Understeer
Post by: TheBoy on 09 July 2018, 18:13:03
All Omegas suffer high speed understeer, presumably by design.

I made my beloved Silver Bullet more pointy by using Irmscher springs at the front and stock at rear, all set up to WIM's default Omega settings.  TBE was set the same until recently, when the front went back to stock due to excessive bumper wear.  With TBE lowered all round on Irmscher kit, it understeered the same as stock.
Title: Re: Understeer
Post by: Migv6 le Frog Fan on 09 July 2018, 18:21:54
You would be hard pushed to buy a car these days which doesn't have built in understeer as a design feature. It became standard when most cars were being driven by people who know nothing about driving.
Worth trying to design it back out though, with above suggestions.
Title: Re: Understeer
Post by: Muroman on 09 July 2018, 21:01:05
About the tyres, what kind of tyres would help?

Less pressure could help too, but that makes the tire wear more on the middle?
Title: Re: Understeer
Post by: Doctor Gollum on 09 July 2018, 21:13:46
My ex plod was always run at fully loaded pressures... 42/48 iirc.

If it did understeer, then it was not enough to cause concern when pressing on, regardless of dry, rain or snow ;)
Title: Re: Understeer
Post by: Nick W on 10 July 2018, 00:13:36
About the tyres, what kind of tyres would help?

Less pressure could help too, but that makes the tire wear more on the middle?


over inflating them does that.
Over 20k miles from budget tyres is easy from a properly maintained car.
Title: Re: Understeer
Post by: Raeturbo on 10 July 2018, 00:27:03
https://speed.academy/how-to-fix-understeer-or-oversteer-suspension-handling-setup-tuning/

There you go have a read of this.
Title: Re: Understeer
Post by: biggriffin on 10 July 2018, 08:11:14
https://speed.academy/how-to-fix-understeer-or-oversteer-suspension-handling-setup-tuning/

There you go have a read of this.


Don't confuse people.

You need to soften the front,

Tyre pressures rears 35, front 30,-32,
Check geometry

But are you saying it's understeering, because your trying to get the barge to behave like a sports car.
Title: Re: Understeer
Post by: Raeturbo on 10 July 2018, 08:31:25
Once he understands what’s happening and when, he will have a better chance of correcting it.
Knowledge is a wonderful thing.
Title: Re: Understeer
Post by: Raeturbo on 10 July 2018, 08:42:55
My first move would be to get rid of the toe in and set neutral. Is the camber adjustable on these cars?
Title: Re: Understeer
Post by: Doctor Gollum on 10 July 2018, 08:53:00
Zero toe is what WIM suggested for mine when it had vertical poly bushes. Rest of settings remain unchanged from Omega recommended  :y
Title: Re: Understeer
Post by: Migv6 le Frog Fan on 10 July 2018, 13:18:01
Yes, camber is adjustable.  :y
Title: Re: Understeer
Post by: Raeturbo on 10 July 2018, 14:27:51
Good maybe a little more camber then too, and as said adjust tyre pressures. I would think those tweaks will make a nice difference
Title: Re: Understeer
Post by: TheBoy on 10 July 2018, 18:15:37
My ex plod was always run at fully loaded pressures... 42/48 iirc.

If it did understeer, then it was not enough to cause concern when pressing on, regardless of dry, rain or snow ;)
Errr, your white estate? That understeered like, well, and Omega.  On the plus side, because you used pretty crap tyres that were pumped up to 10m psi, it just slid all over the place, partially hiding it into a drift...   ...or did when I drove it at Wycombe.  "Pressing on" wasn't really possible I found.
Title: Re: Understeer
Post by: Doctor Gollum on 10 July 2018, 22:18:41
I never found that with it ??? Certainly never felt like it was about to let go. Sure the estates do wallow a bit when pressing on which might explain your impression :-\

I honestly thought that set up was a vast improvement on bushes... It was a bit trial and error though, but if it didn't corner properly, then I would have tried summat else.

Don't forget that I used it as a taxi with that set up :y

Title: Re: Understeer
Post by: Muroman on 11 July 2018, 07:48:01
Front 42, rear 44 psi.

I'm a race driver but I somehow think Omega is more complex than a tubural frame racing car, maybe the basics are the same but I believe we have exact Omega experts here :)

It will turn in sharp with high speed but once in corner it starts to understeer. It will also understeer when low speed and full throttle.

I'll get a better angle meter today or tomorrow so then we will have some results  :y
Title: Re: Understeer
Post by: ajsphead on 11 July 2018, 08:17:19
If it's any help, I get very little understeer from mine relative to the big barge heavy engine it'll never be a sports car principle. Camber and toe as DG has said, Eibach -30s and Bilstein B4s with polybushes 32 psi front 34 rear on standard size 17" tyres.

I only get low speed full throttle oversteer, never understeer and gradual mid corner application of throttle causes the front to slightly tighten unless you are doing stupid speeds relative to the turn in point. I'd suggest softening it off but getting rid of the standard springs as they are designed for all round comfort and if old are probably knackered.
Title: Re: Understeer
Post by: Kevin Wood on 11 July 2018, 09:38:42
I'm a race driver but I somehow think Omega is more complex than a tubural frame racing car, maybe the basics are the same but I believe we have exact Omega experts here :)...

The thing is, the Omega is no double wishbone setup. Once the suspension starts moving in a dynamic scenario, the angles probably bear little resemblance to what you've achieved with a static setup because the mcpherson strut arrangement is compromised. In addition, the monocoque is probably a bit more flexible than a sports car's spaceframe and you have big, flexible bushes supporting the suspension components. The principles that you apply to setting up a race car probably don't apply, at least not in the same way, so a bit of trial and error is needed, and you probably need to think more about how the suspension moves when loaded up than how it's set up in a static sense.

I've always found mine (standard MV6 LSC setup) to handle pretty neutral but then I don't really find it a fun car to be driving right on the limit (I have a Westfield for that).
Title: Re: Understeer
Post by: Doctor Gollum on 11 July 2018, 10:10:23
Perspective is a wonderful thing  ;)

Leave the camber. Adjusting that will have little more effect than killing tyres. That said once you zero the toe, camber will need adjusting again as the geometry is three dimensional...
Title: Re: Understeer
Post by: henryd on 11 July 2018, 10:33:19
Front 42, rear 44 psi.

I'm a race driver but I somehow think Omega is more complex than a tubural frame racing car, maybe the basics are the same but I believe we have exact Omega experts here :)

It will turn in sharp with high speed but once in corner it starts to understeer. It will also understeer when low speed and full throttle.

I'll get a better angle meter today or tomorrow so then we will have some results  :y

Another thing is mass,the omega is heavy and will behave/react differently to a lightly loaded racer
Title: Re: Understeer
Post by: Muroman on 11 July 2018, 16:22:53
Okay so I don't know what had I measured but I had 11mm toe in... Well changed that to 2mm toe in. Tested and it was better but then I changed camber from 1.1 degree to 2.2 degree. Now it goes good. Ofcourse you can make it understeer but now the understeer is correctable with throttle.

And also tested toe out but that made the car jump around on the trails so changed that back.

I'm happy for now but I could buy new suspension parts, might even need to give up with the self leveling.
Title: Re: Understeer
Post by: Nick W on 11 July 2018, 16:36:16
Okay so I don't know what had I measured but I had 11mm toe in... Well changed that to 2mm toe in. Tested and it was better but then I changed camber from 1.1 degree to 2.2 degree. Now it goes good. Ofcourse you can make it understeer but now the understeer is correctable with throttle.

And also tested toe out but that made the car jump around on the trails so changed that back.

I'm happy for now but I could buy new suspension parts, might even need to give up with the self leveling.


If you've really set the camber to 2.2°, you'll be buying tyres on a monthly basis!


1.1° of negative camber at ride height is what you want, and you ought to measure it more precisely.
Title: Re: Understeer
Post by: Doctor Gollum on 11 July 2018, 16:49:23
Okay so I don't know what had I measured but I had 11mm toe in... Well changed that to 2mm toe in. Tested and it was better but then I changed camber from 1.1 degree to 2.2 degree. Now it goes good. Ofcourse you can make it understeer but now the understeer is correctable with throttle.

And also tested toe out but that made the car jump around on the trails so changed that back.

I'm happy for now but I could buy new suspension parts, might even need to give up with the self leveling.


If you've really set the camber to 2.2°, you'll be buying tyres on a monthly basis!


1.1° of negative camber at ride height is what you want, and you ought to measure it more precisely.
And set toe to zero... ::)
Title: Re: Understeer
Post by: TheBoy on 11 July 2018, 18:16:49
It will turn in sharp with high speed but once in corner it starts to understeer. It will also understeer when low speed and full throttle.
Exactly my experience, and cured vastly improved by front springs (only) as I suggested above, but it can make the back a bit skittish under my idea of heavy braking at my idea of high speed if you have and steering angle on.
Title: Re: Understeer
Post by: TheBoy on 11 July 2018, 18:20:17
I never found that with it ??? Certainly never felt like it was about to let go. Sure the estates do wallow a bit when pressing on which might explain your impression :-\
Up til that time, I regularly drove a lot of Omegas, many estates as well, though not so many now.  And that Terbs reprobate probably won't get in the car with me ever again, despite it being a reasonably gentle ride ;D

I think I commented at the time, the suspension felt solid, but that car was unable to grip the road, ruining the effect.
Title: Re: Understeer
Post by: Muroman on 11 July 2018, 19:49:37
I mean 2.2 degree negative camber and it is now measured very precisely. I got to rethink if they really wear so fast  :-X  ::)

That 2mm toe in is must have at finnish roads with 235 wide tyres so can't be without it
Title: Re: Understeer
Post by: Raeturbo on 11 July 2018, 21:22:52
No road needs that much toe in surely????
Title: Re: Understeer
Post by: Raeturbo on 11 July 2018, 21:24:57
Camber would be choice adjustment for roads , hence the name.
Title: Re: Understeer
Post by: Doctor Gollum on 11 July 2018, 23:54:12
1°10 is perfect Omega camber.

Zero toe is required because poly vertical bushes significantly alter the way the wishbone behaves during turns.
Title: Re: Understeer
Post by: Raeturbo on 12 July 2018, 12:31:46
Agreed and even that’s considered ‘sporty’ by some for a comfy type car.
Title: Re: Understeer
Post by: Muroman on 12 October 2018, 06:47:25
Just to update on car, I changed toe in 0.2mm, camber still 2.2 degree and lifted the rear a bit.
This made the car somehow unstable on corner exit but the understeer stayed pretty much away. (Maybe the higher rear)

Then lowered the car back on where it was and changed the rear tyres to thinner 205. This made the car oversteer very much but as winter is coming it's okay :)

Maybe could change the camber to 1.1 degree for winter roads. I think the 0.2mm toe in is all around good.

I lower and lift the rear by adjusting the small joint that measures the rear height. I made it adjustable with threaded rod.
Title: Re: Understeer
Post by: Doctor Gollum on 12 October 2018, 08:10:16
Do you have the Polish poly vertical bushes in the front wishbones?

If so, try zero toe at the front... Advice given by Wheels In Motion when I was experimenting with mine ;)

Title: Re: Understeer
Post by: Muroman on 12 October 2018, 13:44:57
Does omega change toe when braking or accelerating? Because my race car does go toe out when braking hard and by that I mean front going down.

I have those vertical polys.
Title: Re: Understeer
Post by: Doctor Gollum on 12 October 2018, 16:30:31
1. Only if the geometry is screwed up or the front bushes are shot... Powerflex bushes all but stop this.

2. Set Toe to zero. With those bushes there should be no movement fore/aft as the weight transfers so you don't need toe to compensate :y
Title: Re: Understeer
Post by: Muroman on 19 November 2018, 05:57:44
Camber 1.2 degree.
Toe is now 0, on scale +-0.05mm.

It is understeering again  ::) But yes the front tires are shot from the inside side, so I'll drive the winter with this setup.

Couldn't get to 1.1 degree camber on the right side of the car, anyone know why? I mean I have the adjustment on limit.
Title: Re: Understeer
Post by: Doctor Gollum on 19 November 2018, 06:24:03
Manufacturing tolerance of pattern parts...

Basically, use a suitable file to slightly extend the oval slot on the top strut/hub bolt ;)

Once the tyres have started to wear in a particular way, they will continue to wear unevenly even if the cause has been addressed.

Tweak the camber adjustment, fit new tyres and report back after a few k:s ;)