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MG MGF Technical - As car lowers does the tracking toe out more ?
|As the car lowers due to hydrogas unit settleing over the year does the tracking toe-out as the car gets lower?|
|Dave, according to 'bump steer' figures published by John Englaro on this board, quite the opposite occurs: on suspension compression, the toe angle tends towards increased 'toe-IN'. I think that these figures are accurate and seem to fit the slight changes in chassis handling characteristics I've noticed on my own car with the recent very cold weather.|
|Rob, I don't quite understand. Mine is def toe'ing out and the dealer blames it on the lower height. It didn't pass tech control until they put it in 4x4 mode and tracking was satisfactory for regulation.|
Anything else I can do to get those wheels back inwards, or should I just keep paying new front tyres every 4000 miles?
|Dirk, I didn't understand the comments that your dealership made either. I think that they have made an error in that what they have told you: they probably meant the camber angle of the wheel. As the car is lowered, the camber becomes more negative- and this certainly can lead to inner edge tyre wear. However, the camber angle changes are comparatively mild and do NOT lead to the tyre wear patterns seen on the front wheels. Many cars run more than 0 degrees 1 minute negative camber without problems.|
(Definition of terms and concepts, see: http://ourworld.compuserve.com/homepages/robmidgleybell/mgf_suspension.htm )
Dealerships often do just pump up the suspension as a 'knee-jerk' reflex to tyre wear that displays a worrying lack of understanding of the problem. In fact, the front tyre wear issue has another solution that DOES involve the toe-angle that you will often find Tony, Matt, Alan and I frequently writing about: set the front toe-angle from the standard setting to 0 degrees 5 minutes toe-IN. I thought you had already tried this?
If this is so why when my car get's lower do the test readings show more toe out when I have the tracking adjusted. ? In my experience this has been the case. Something does not make sence here, it's not logical cap'n
Not that I'm saying you are wrong, but I'm sure we have at least one vital part of the puzzle missing. One thing for sure they are not all the same because many Fs don't have a problem with tyre wear even with the original Rover settings as far as I know.
If what you say is true then it may explain the problem also. If the wheels tend to toe in at normal height and more so if lower, it could be that the dealers have been getting it wrong. Maybe people are wearing tyres down because the car is too high. It comes into the dealer high and they keep it high because they believe it will solve any tyre wear problems and save them hastle. Every time you take the car in they pump it up just to make sure. With the car going up and down all the time who could tell the difference.
Maybe on the wrongly jigged cars like mine it behaves differently having a different camber on each side.
I know there is a lot less difference in the handling between hard acceleration and crusing speed these days. This is no doubt down to the polly bushes.
Surly it depends to some extent how the front wheels are aligned as to which direction they will move under load.
I think the only people who could really answer this are the members of the suspension design team for the F.
Somewhere I smell a really big cockup on someones part. I just wish MG Rover would be more open about it and tell us what is really going on so we can make sensible decisions instead of having to stab in the dark and rely on confused dealers.
|If I remember correctly (and I'm quite sure I do) the toe angle at the front tends towards Toe OUT at the front and stays nearly constant at the rear. It is common practice to design the bump steer on the front like that in order to reduce lift off oversteer. We had a thread about this a while ago, maybe you can find something in the archives.|
|Looks like some misunderstandings|
As Nikolaj mentioned.
Definately the Toe angles get more toe OUT at the front if the car dives (or -xx minutes). -5 minutes per app. 10mm hight loss. (not straight (linear) over the complete hight change rate)
Tyres will rub at the inner side if the angles consumption reach more then app 15 to 20 minutes and more toe OUT.
At the rear happens nearly nothing related to the toe angle change.
Guess you mixed it with any other angles. ?
>Surly it depends to some extent how the front wheels are aligned as to which direction they will move under load.
Nope, 'she' makes the legs wide in any way at the front, seen from above. Direction is fixed, but the quantity depends on load. :-)
>Mine is def toe'ing out and the dealer blames it on the lower height.
... the first time your dealer found the right issue just from the beginning :)
Guess I need to finish this document(s) at any time
|Dieter, so if the car tends towards toe out why the hell did Rover recomend a toe out setting on the front wheels. They must have known how flexible the suspension was when they designed it, especially when parts started to wear. It was almost guarenteed that the front tyres would start to wear unevenly and after a while some handling problems were bound to occur.|
I must admit I got the tyres wearing down unevenly even when it was in 4x4 mode also, that's why I had to change the tracking, nothing else worked, maybe height has very little to do with the problem after all.
That reminds me, now my new shocks have settled in I need to get my tracking adjusted, just getting a little wobble off the steering wheel now, I'm going for the same setting.
|Ah my error- look at the Archive thread "Suspension Geometry Design"|
The rear suspension toes-IN on compression, unless equipped with compliance washers where the toe-angle changes become practically nill.
The front suspension, as you all quite correctly point out, toes-OUT on compression.
Tony- I don't really understand the reasoning for the front standard toe angle because as you rightly say it only exacerbates toe angle changes associated with acceleration and suspension drive with braking. It does however promote understeer, and this is the only reason that I can see for the geometry that we have. Incidently a second reason may be more pragmatic- it is a Metro front subframe- a FWD car, and toe-OUT on the front wheels is common on FWD cars to compensate for the toe-in caused by the torque loads transfered by the road wheels...
Back to Dirk's dealers comments- they still don't track (excuse the pun). Toe angles are readily changed by adjustments to the track control arms... still reckon that the dealer was talking about camber.
|When will Rover understand that the F is not a Metro? :-)|
This thread was discussed between 13/03/2001 and 14/03/2001
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