Help figuring out which bush MOT advisory

[Breezy_Pete]

Something to bear in mind if replacing OE versions with either Cupra or the various poly-bush varieties is that the central hexagon hole that the wishbone spigot goes through isn't actually central on the OE ones, it's about 3mm inboard or outboard of centre, I forget which. That's why the OE types and their direct equivalents have a correct orientation, but the others can be fitted any way round (I think, as long as you have flats of the hex top and bottom?) because the hole is central  (Anyone got one to hand to check this?).  You can see this off-centreness of the OE hole reasonably clearly in my second photo above.

 

Upshot is that going from an off-centre type to a central type will surely throw the wheel alignment out, so neglecting to get the toe set up afterwards would be costly on tyres, almost certainly in my opinion. Replacing like-for-like is less likely to stuff up the alignment, though still wise to have it checked.

Edited 27 September, 2016 by Wino

[StevesTruck]

Aye that sounds about right.  Have a gander at it and see if you can any damage to it.  Most of the cost for changing it will be labour.  OEM part will be less than £20 I suspect, less than a £10 for non oem one.  Might as well get them both done and fit the cupra or meyle hd ones.  Powerflex ones are dearer to buy but simpler to fit (threaded rod and big washers anyone?) but they are too solid for me and my fat ass.

 

It was getting dark and I was in a rush, so mine went in with a bit of silicon spray, a lump of wood and a rubber mallet   Nowt wrong with how you did it though. 

[rum4mo]

Wino, did you not mean your first picture - as that one shows the front of the bush with the "end" of the spigot hole recessed?

Come to think about this, that could be the reason why after my local proper VAG indie fitted the O/S (Cupra) bush "back to front" to my wife's 2002 Polo, then carried out a complete four wheel realignment - only for me to notice next day that the O/S was wrong, VAG indie's comment when phoned was "I'd doubt it but if you buy another (Cupra) bush we will sort it"! That car, within days, then got a new full set of Michelin Pilot Exaltos, ran maybe 8500miles, went for its next MOT at my local VW dealer and failed for the outside edges of the (newish) front tyres being nearly bald!  I can't say why I did not notice that especially as I had the wheels off to clean up the brakes!  When the VW dealer completed the MOT they carried out another four wheel realignment, so that car continued until it was 13 years old with normal tyre wear.

[Breezy_Pete]

I'm referring to the orientation of the bush 'around the hex'. If the hexagon is central with respect to the outer diameter of the bush, you'll get a different wishbone angle than if it's offset like the OEM bush.

 

Does this make sense?:

 

Edited 27 September, 2016 by Wino

[rum4mo]

Yup, but your posting did make me think a bit more about why I suddenly needed another bit of alignment after paying for one 9 months earlier - so thanks for that even if it makes no difference as that was about 8 years ago, ie, I can see that when I went back to that VAG indie, they probably only did the bare minimum to sort things out as they were paying for the time, so no alignment check second time round!

 

Edit:- I'd always considered that a rotational error when fitting the bush would only produce a bit of unwanted lift or droop of that TCA side of the car, until the rubber element gave in and sheared a bit.

Edited 27 September, 2016 by rum4mo

[Breezy_Pete]

If the spigot of the wishbone is 3mm inboard or outboard of where it used to be (with the different style bush), then the balljoint will be about 3mm further forward or aft of where it was, as the arms of the wishbone are approximately the same length, approx at right-angles, and can pivot around the front bush.

With the tie-rod fixing the back of the bearing-housing in a fixed-length arc from the inner BJ at the rack , this will toe in/out the wheel accordingly.

Edited 27 September, 2016 by Wino

[rum4mo]

Ah, now I see that I did not look at your second picture properly or read your previous posting properly - sorry!  So these original bushes, which I've never actually handled a new one off, need to be fitted in one orientation on one side and 180 degrees away from that on the other side, I have only ever looked at a torn bush of the original pattern.

[Breezy_Pete]

Yup. And if you change from OE to a type where the hex is central, the wishbone angle (in the horizontal plane) will change. Without looking in detail at the geometry I don't know know how big an effect this might have on the toe though.