Dropping the rear of the radius arm to correct caster on a 80 series 24v manual

Has anyone corrected caster after a lift by using/fabricating brackets to drop the rear of the radius arm of a 24v manual 80?

If you have, any possibility of some photos?

Any idea how much it has to be dropped per degree?

Man-A-Fre make them for an auto but say that they don't fit a manual.

You really only drop the rear of the RA for lifts in the 6" region. Typically you are only correcting 2 degrees or so which is fine up to a 5" lift. This is all done by changing the front mounting points. What ARE you planning?

Chris said:

What ARE you planning?

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I've already done it and have 2 degree bushes in but it's not enough. Right now my caster is -1 degree so I need another three degrees of correction.

Other than that being a completely gorgeous 80, how does it show castor correction needed? You have a real stink-bug lift issue going on for sure, but it looks like the rear that needs some attention. You said the rear of the radius arms. Since castor is related to the front, I presumed you meant the rear mount of the front arm. Looks to me like there is something wrong with the rear spring. The front looks fine. I genuinely wouldn't have used bushes. I'd have used plates to correct the effects of front end lift. Adding correction more to the front won't cure that. Rotating the front axle won't counter what is going on there.

Exactly what have you done? Where did you buy a brand new 80 from? I won't be able to sleep now. Have you got one in blue as well?

Ill try and upload some photos of the plates I have on mine later.

80 looks nice

Crikey that lift has made a big difference to the caster angle.

Nice looking rear bumper / carrier too.

Looks almost like you have different spring sets back and front. The rear lift is huge. Anything you do with castor won't change that.

The mighty Monty looking superb there Garfeildus

Mine has only 110mm (4" + a bit) lift and I'm using CC bushes, up on the front mount and down on the rear, but I don't know how many degrees.

How does the front prop look when sighting up to the diff flange? Is the diff flange noticeably at an angle to the approach line of the shaft?

The lift on the rear of the truck looks similar to mine.... Meaning the relative distance from top of rear chassis rail to the top of the tyre (mine are only 33").

Chris said:

Nice looking rear bumper / carrier too.

Looks almost like you have different spring sets back and front. The rear lift is huge. Anything you do with castor won't change that.

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Excuse me, but aren't we mixing things here?

Castor correction is needed to keep the relative position of the front axle as stock as possible to the front propshaft angle.

Lifting the rear suspension (or lowering it for that matter) has no effect whatsoever on the castor angle of the front axle, it just alters the position of the back of the truck to the road.

Longer springs on the front (or suspension lift) rotates the top of the front axle forwards, relative to the front propshaft, so correction is needed to rotate it back again to an acceptable angle to the propshaft. Nothing to do with the back of the truck at all.

JMHO.

The caster angle is set rigid with these axles and with the front radius arm. Anything that alters the angle of that arm to the horizontal will also alter the caster angle. If you raise the rear the chassis will rotate around the front axle axis and lift the rear of the arm and slightly alter the castor.

The question is with the caster correction "what are you correcting it to?" as the original figure in the workshop manual is irrelevant with lift. Unless I've missed a chapter on recommended Toyota 80 lifts and caster angles.

If the car corners OK and the steering returns the caster is doing it's job.

http://www.motor.org.uk/documentlibrary/Sep 09/TT _ Sept 09.pdf

The above read is very good.

Don't read wiki it's bollocks.

Thank you all for the comments/compliments. I bought Monty about 15 months ago in Liverpool just before I sold Rommel back to the UK. It's a 1997 GX 24v manual with the crappiest driver's seat my arse has ever encountered and am still on the lookout for a beige leather driver's seat (@karl, have you come across anything yet?) I have a build thread on lcoc.ie.


@Chris - yes, of course I meant the back of the front radius arms. The springs are a matched set of slinky progressive springs (+400kg) from Australia.

The picture was taken two minutes after it was put back on it's wheels after the suspension was fitted and the axles removed, blasted and painted. The chassis and floor derusted and schultz'd. It has settled down maybe by 20mm at this stage. As it sits in the photo there is absolutely nothing in the back except the bumper. The bumper was made by a very skilled fabricator in Wexford who is a fantastic interpreter of ideas. He made two to our exact requirements. Photos available if anyone wants them.

I brought it to be tracked after the above job (new ball joints also) and the readout shows the caster at -1 degree. I would much prefer a bolt on solution (for the back of the front arms) rather than the washer mod (on the front of the front). Hence my original question.

I was surprised at the readout. I expected 0 to 1 degree as the slinky supplier said we would need 4 degrees of correction and I have 2 degree bushes in already.

You are right Clive, both your lift and mine look very similar, what springs are you using?

@karl - have you lowered the back of the front arms? If so, is it on a manual? If so, where did you get the brackets? What distance does it need to be lowered to gain one degree of correction.

Interesting, because I have a set of Slinkies on order for mine. Raising the rear does in effect rotate the truck around the front axle but I'd suggest in that way the difference would be almost undetectable and of course it wouldn't affect prop entry angle. The biggest effect of course on caster is spring height. As far as I was made aware, CC plates would be needed with this set up and 4 degrees. Mine will be done with plates at the front. I have already moved the axle forwards 18mm on the rear mount. I think that rear end wise the simple fact is that you aren't loaded. They are 400+ as you say and progressive. It needs an anvil or something in there.

Photos of the rear bumper? Are you kidding? Get them up now!!!!

@Clive, I wasn't mixing anything up mate. I was saying exactly that the difference in height was naff all to do with caster. It'd be my preference to get the vehicle level before I started any corrections.

Chris said:

Interesting, because I have a set of Slinkies on order for mine. Raising the rear does in effect rotate the truck around the front axle but I'd suggest in that way the difference would be almost undetectable and of course it wouldn't affect prop entry angle. The biggest effect of course on caster is spring height. As far as I was made aware, CC plates would be needed with this set up and 4 degrees. Mine will be done with plates at the front. I have already moved the axle forwards 18mm on the rear mount. I think that rear end wise the simple fact is that you aren't loaded. They are 400+ as you say and progressive. It needs an anvil or something in there.

Photos of the rear bumper? Are you kidding? Get them up now!!!!

@Clive, I wasn't mixing anything up mate. I was saying exactly that the difference in height was naff all to do with caster. It'd be my preference to get the vehicle level before I started any corrections.

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Your point is taken Chris. As I said, it was JMO that the subject of the high rear-end was being mixed with the original question about castor correction, and as we agree, there's no connection between the two.

Originally posted by Garfieldus "You are right Clive, both your lift and mine look very similar, what springs are you using?"

This was the OME order for my lift...

You can purchase new arms with the correction in the casting, this saves having offset bushes/plates, if course now I have told you that I cannot remember where I saw them.....was it Slee on MUD?

regards

Dave

http://www.sleeoffroad.com/products/suspension_pieces_arms.htm

There ya go, these are for the 6" lift,

regards

Dave

Dave 2000 said:

You can purchase new arms with the correction in the casting, this saves having offset bushes/plates, if course now I have told you that I cannot remember where I saw them.....was it Slee on MUD?

regards

Dave

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Dave 2000 said:

http://www.sleeoffroad.com/products/suspension_pieces_arms.htm

There ya go, these are for the 6" lift,

regards

Dave

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Thanks Dave. I am aware of all these solutions. But I have to refer to my original questions in post #1 regarding dropping the rear of the front radius arms.

I think the answer to your initial question is that , no, not many people have done that because it's not generally how we correct caster on an 80. If it was a Landie we'd be able to get cranked arms from Tesco. Which would be a nice solution if they did them for the Yota. Typically caster correction plates are used on the front. When you go for a really big lift and I think Karl's was like 6" or something, simply correcting axle rotation isn't enough anymore at that point. As the arm drops, effectively the wheelbase reduces because everything is up on tiptoes. At this point people use drop plates to push the arms forward (rather than intentionally to correct caster which is still done at the axle end) to get that length back. Of course you can correct it by dropping the rear of the hockey stick, but it's just not generally done that way.

I suppose that you have the strength of two mounting points on the axle whereas you only have the one at the back. Now in relation to CC plates, I have only seen plates on the front mounting point but I guess you could also drop the rear bolt point too.

That said, I don't think making rear plates would be very hard and you'd certainly have more room to work. I'd just be worried about stiffness in cornering. With a really big lift you do have to conside the rear too. I know that you can get on vehicle adjustable top arms so that you can jack the rear axle rotation around for better prop angle.

There called Drop Boxes and there are a few companies making and selling them.

I actually made my own on my 70, but mine push the front axle 50mm forwards to stretch the wheel base for stability, to improve the approach angle and to give me more tyre clearance.

http://www.man-a-fre.com/pa/80seriescastercorrection.htm

That's the way.