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[feeutfo]

I went the first time because the tyres were wearing,,,,,,, bought new tyres, wishbones, droplinks, steering idler + 4 dampers & springs & noticed the new tyres were wearing on the outside after a few thousand miles
Went back & explained the situation. They did it again but this time the steering wheel wasn't straight,,, really annoying
The tyres are now nearly knackered on the outside but have about 5mm tread across the rest.
Waste of £120

Ime...I think fitting new springs can cause the outside wear on the front. Springs take a time to settle to their specific ride hight. How long? who knows, but I guess about a month should see most of the settling done.
Reason it causes outer edge wear is the omega is very sensative to ride hight because it affects the camber setting, increasing camber as the ride hight lowers. Excessive camber causes INSIDE edge wear. But here's the thing, as i understand it, when camber increases this affects the toe setting, causing toe in UNLESS the track rods are shortened to retrieve correct toe setting again.

Think along the lines of, if the top of the wheels lean in, then the steering tie rods have to be shortened as well, because they are rearward of the front axle point, leaning the wheel top in means the wheel also must toe in as well, it has to.

This is why wim deal with the omegas front settings in order of caster(subrame position, this must be correct first as altering it will cock up camber and toe, but not relevant to this issue) then camber(because leaning the wheel in affects track rod length, they need to be shortened) then last of all toe once caster and camber are correct.

Toe in has caused your outside edger wear, resulted from springs settling as they do, which increased camber which in turn caused excessive toe in. So I guess there "may" have been inside edge wear from excess camber, although probably not massive, along with outside edger wear caused by excess toe(front wheels like this / ^ \ when viewed from above arrow showing forward direction)

Hope I've explained that clearly. Understanding it us one thing, conveying it to others is quite another. 

[feeutfo]

This also explains bump steer on the omega. A bump decreases ride hight, ride hight alters camber(not the setting but naturally as the wheel rises) which in ceases toe which feeds back to the steering wheel. As I understand it...?

[feeutfo]

This also explains bump steer on the omega. A bump decreases ride hight, ride hight alters camber(not the setting but naturally as the wheel rises) which causes toe in which feeds back to the steering wheel. As I understand it...?

[Kevin Wood]

Bump steer is down to the track rod not following the same arc as the wishbone(s) as the suspension undulates, or so I thought? Thus the relative length of the track rod changes, directly altering the toe?

[feeutfo]

Yeah, so we're saying, if the suspension was re assembled with out the spring, and moved up and down by hand, we would see camber variation to positive at the bottom of the stroke with toe out?, to negative at the top of the stroke with toe in, due to the fixed length of the track rod....

Or to put it another way track rod needs go be telescopic to maintain toe setting, not that you'd ever want that of course, just another way of looking at it...?

As I understand it..?

[aaronjb]

You're right, I believe, Chris.

The proper fix isn't telescopic rod ends, mind, it's correct suspension design at the factory of course I imagine on a production car the whole thing is a big barrel of compromises due to packaging/space/budget/etc (otherwise there'd be no McPherson strut cars at all, I reckon..)

[feeutfo]

Wondering how desirable toe In during bump is? Maybe during cornering. But bump steer, definitely not. Or at least I find it excessive personally, I also wonder if some feel might be lost if eradicated completely...?

Is the stub axle steering joint at the same hight at the steering knuckle? I'd go look but...mines bent and not here anyway. Pfff. 

[TheBoy]

If the tie rod is exactly parallel with the suspension arms when travelling in a straight line, there should be no bumpsteer.

No idea how close Omega is to that...

[Kevin Wood]

If the tie rod is exactly parallel with the suspension arms when travelling in a straight line, there should be no bumpsteer.

No idea how close Omega is to that...

Yep, so it's the vertical location of the rack/crossmember relative to the wishbone pivot point that's critical, along with the length of the wishbone against the length of the track rod from its inboard ball joint.

But you will still get some toe variation simply because the upright doesn't pivot on 2 equal length wishbones but a wishbone on the bottom and a strut at the top. You'll hopefully get a just a manageable amount around the "normal" range of suspension movement. If you lower it YMMV.

[TheBoy]

If the tie rod is exactly parallel with the suspension arms when travelling in a straight line, there should be no bumpsteer.

No idea how close Omega is to that...

Yep, so it's the vertical location of the rack/crossmember relative to the wishbone pivot point that's critical, along with the length of the wishbone against the length of the track rod from its inboard ball joint.

But you will still get some toe variation simply because the upright doesn't pivot on 2 equal length wishbones but a wishbone on the bottom and a strut at the top. You'll hopefully get a just a manageable amount around the "normal" range of suspension movement. If you lower it YMMV.

Although camber on its own (and with a MacPherson strut, its all over the place anyway) will lead to pushes and pulls on the road, so toe bump steer is probably only a small part of it anyway 

[Kevin Wood]

Yep, and, of course, we're assuming the body of the car is rigid.

[TheBoy]

Yep, and, of course, we're assuming the body of the car is rigid.

Indeed -though to me, the Omega does seem pretty good in that respect.  Mind you, with 1.7t on metal, it blooming well should be

[feeutfo]

The relationship between bump steer and natural camber and toe deflection are one and the same ime.

During previous ponderings under the car, the inner track rod ball joint and wb pivot appear to align. So to speak.

Stub axle pivot points, I may get a closer look at those in the coming weeks. (Sigh)

[Omega 37]

I will have to take it back,,,,,,, its all very complicated
The front springs/dampers were replaced after my 2nd visit.

[gstylebaby]

Just bought two sets of drop links from buypartsbuy and hope to have the same result as o.p thanks for the tip fella.