Bending Radius Arms? Yes/No?

[Cloggy_NZ]

Probably one for the engineers on here....
I know the LTSA etc. frown on this practice, but is it safe to heat and bend forged radius arms if done properly?
Recently lifted my Disco about 65mm and this has resulted in the front arms entering the chassis bushes at an angle.
I figured if it was done properly the average WOF inspector would not even notice a small corrective bend right at the end of the arms where it enters the bush.
So, is it safe to do and what would be the proper heat up and cool down procedure?

At the same time some castor correction would help as well. Rather than muck around with correction bushes (I would like to keep stock rubber bushes for ease of sourcing spares) I was thinking of slotting the mounting holes in the swivel ball housing. This would allow me to rotate the complete swivel ball relative to the diff housing and set the desired castor.
A good idea or one just asking for problems?

[KiwiBacon]

The rangie radius arms are quite soft so there's little risk of strain hardening and the associated cracking. Heating while bending won't hurt them as they're already soft, provided you heat a great enough area to not get all the deformation in one small zone.

Personally I'd be happy with a dye crack test of the bent area. I actually have a set here which have been done (not on my vehicle at the mo) and show no ill effects, they were bent about 200mm back from the rearmost bush. Whether they'd even be spotted by a certifier is up for debate.

[Ralfie]

Check out this web site.
http://home.off-road.com/~highrange/

He went through this process a few years ago and reports how he got on under the list of modifications for his Range Rover.
Basically all was OK but he had to get them checked out by specialists before the inspectors would pass them.

As for the swivels again see
http://www.lrautomotive.com.au/57.html

They re drill and slot the swivel housings to correct caster.

[Cloggy_NZ]

Thanks for those links Ralfie,
I had seen the Rangie one before but had forgotten about it. Never seen the LRautomotive site, but this site looks very interesting.
Cheers

[wjw]

We were going to bend my radius arms for my lift, but on speaking to the certifier, he said your not allowed to anymore, so got some of those bushes with the hole offset instead

[91Rangie]

Like WJW said your not allowed to modify orginal parts you must fabricate new ones
You saw my ones and for the price and piece of mind why not?

[KiwiBacon]

Like WJW said your not allowed to modify orginal parts you must fabricate new ones
You saw my ones and for the price and piece of mind why not?

That's a very dumb rule.
Might be time to pull the certification from mechanics and put it in the hands of engineers.

[Cloggy_NZ]

Thanks guys,
Bending the radius arms is not to get the castor right. Merely trying to correct the loads on the suspension to chassis bushes. Currently the bush is loaded as if the suspension is on full droop, and that is with the car sitting level on hard ground.
Went and saw a local engineer today for a bit of advice re this as well. And although strictly speaking you are not allowed to modify suspension components in this case he reckoned it is a safe modification. He has bent, rebent, cut and welded many a suspension arm without any failures. The material they are made out off lends itself to a bit of remodelling provided they are allowed to cool slowly. Wrap them in insulation to retain the heat for as long as possible after heating and bending.
So I might give that a go on a set of spare arms I have got, then give them a good trashing off-road to put them to the test.

For correcting the caster I could fit some of those correction bushes, but they are expensive compared to stock ones. Also talked to the engineer re slotting the swivel balls. Again a costly exercise and he reckoned a simple and effective way is to just cut through the radius arm mounts on one side of the diff, rotate the diff until correct castor is obtained and reweld the bracket together. I quite like this idea as it is cheap ( I am Dutch after all ) and I can do it myself. Strictly speaking I guess this would also be frowned upon by the LTSA and certifiers. But again, if done properly and soundly welded then there is nothing wrong with it.

I guess the rules can be seen as dumb in some respects but they can't cater for every eventuality. The rules need to be clear and concise, black or white. They can't cover the grey area in between hence to make it simple, they just outlaw any modifications made to any suspension components. Even though some modifications can be quite safely executed with a bit of thought and due care.

[KiwiBacon]

I guess the rules can be seen as dumb in some respects but they can't cater for every eventuality. The rules need to be clear and concise, black or white. They can't cover the grey area in between hence to make it simple, they just outlaw any modifications made to any suspension components. Even though some modifications can be quite safely executed with a bit of thought and due care.

I thought the only hard and fast rule was that it needed to be deemed safe by a certifier. After all the only way rules can cover every eventuality is a blanket ban on modifications.
In other countries (like Aussie) you need to find an engineer willing to sign it off. No engineers certificate then no driving on the road. That turns every situation into either black (no cert) or white (certified safe).
That's the way it works in NZ for heavy vehicles, but passenger vehicles are still done by the Hot Rod Association.

But I do notice the old "vehicle in service requirements" on the LTSA website is now a dead link.

This appears to be the new one, but I haven't found the significant differences yet.
http://www.landtransport.govt.nz/certif ... ion-v3.pdf

[wjw]

Just remember if you do it and don't get it certified your insurance may not cover you. If you bend that radius arms, you will not be covered as you are no longer allowed to do it.

Go talk to a certifier about what your going to do, could save you alot of money in the long run.