FYI - Large wheel clearance and upper wishbone orientation

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HarryMann
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FYI - Large wheel clearance and upper wishbone orientation

Post by HarryMann »

Extracted from Syncro-Doublecabs forum

Kudos to Dennis Haynes for putting his finger on why I'm not having front tire clearance issues on the current van, unlike my last.

Dennis mentioned that the upper control arms can be installed 'backwards'. One arm fits either side, BUT the mounting for the upper ball joint is off center by around 3/4 inch. So you can install the arms with offsets forward or rearward.

Rearward puts the centre of the ball joint close to the shock bolt, forwards is well ahead of it.

Dennis said that his initial setting of the drag link for correct castor is about 11 threads up for the nut. I have a couple of threads showing, and the upper arms are both offset towards the front.

So the whole setup is biased forwards almost 1.5 inches forward, which is pretty much what my fender lip clearance is on this van. I'm guessing this was a factory setup since both sides look untouched from new (ie rusted in place now) I looked in Bentley and didn't see any mention of which way to install the upper arms, but I suspect mine are incorrectly done.
However it looks like the castor setting was done properly. So I'm happy with this abundant clearance for big tires.

Since the arms are symmetric top-bottom, and are intended to used either way up, depending on which side they are on, I can't see a problem with this installation. So I'm keeping it this way, and anyone contemplating putting big tires on may want to set the arms up with the offsets forward and redo the castor/drag link. I can't see any problems with this setup, but any advice is welcome.

So skip measuring the drag link like I suggested, just peek over your tire and see if the ball joint is ahead or in line with the shock bolt.

Tx again Dennis, Tim

I would imagine that whilst castor can be corrected on the radius arm bush positioning nuts, king-pin inclination angle and possibly scrub-radius might be affected by this. Main thing si they're the same either side though!

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Russel
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Post by Russel »

If u install the top wishbone the wrong way round u will have interference
between the drive shaft and ure damper(shokey)

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toomanytoys
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Post by toomanytoys »

Well my last production 1992 model has them installed towards the front and I dont have driveshaft clearance issues.. I know it has never been appart either so is factory!
maybe there is a slight difference in some parts for these later models, I have the cast steel lower arms too?

Russel
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Post by Russel »

Facing towards the front is the factory fitment and standard for all modles.
Early and late suspension has no geometric differences.
When turning the uper wishbone to face the rear is when u get interference.I know this because i have done lots of experiments on the front suspension of syncros,now resulting in being able to fit 235 85 16's

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Post by HarryMann »

Sherlock Haynes and co. now say that they got that wrong I believe, but good to air this subject ? Thanksall...

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