Sierra front end/RUF

[steve125]

My Sierra was originally owned by Qld Rail and has extra 'bits' added to the front shackle bracket. I guess these were for a high rail attachment.

My question is could this be modified into a RUF?

You could almost mount the shackle in the hole that is there without a bushing/rubber but that probably wouldn't be the best. Could you drill out the hole enough, without weakening the extension, and fit a smaller size bushing?

Or should I weld another bracket halfway along the extension?

Or should I just cut it off and start again?

I'm interested in RUF but it's not essential that I have them, I don't really have the fabrication skills or equipment to do a real RUF chassis extension, so I thought modifying the existing high rail extension might be an easy way to get RUF.

[dank]

looks pretty strong Steve. You could potentially just bolt the shackle through the front whole and hope for the best. It looks like it may be strong enough. you could brace it which would be an easy job. premade RUF is cool!

[neofitou]

it does look pretty solid to me, but maybe not actually that stong with some leverage? is it solid or is it a crush tube welded in?

All the RUF ive seen extend the chasis then atach the mount, looks like you might be able to just extend the chasis and then weld it to your nice big bar there.
We could then cut out the hole there and weld in a tube for the bush. Easy!

I will be doing mine in september when my wife is away.
I should have a nice mig welder once my tax return hits, but I am still waiting, might have to give them a call tomorrow. really want those 6.5s.

[gwagensteve]

I don't think using those brackets is a great way of achieving RUF. They don't look especially strongly attached to me, and putting the shackle load all on that little extension might lead to failure.

I'm going to assume the hole in the box section is as set-through crush tube. Putting a bolt straight through that and using it as the shackle mount isn't advisable. It will wear quickly, fill up with scale and rust ( and might actually jam solid) and all the twist associated with articulation will be being borne by the spring bush, which will have a short life. The shackles will also be under more load and be more likely to wear/fail.

Drilling out the box section and fitting a tube of the correct diameter to accept a suspension bush is the preferable idea, but that's a welding/cutting job as the new tube would need to be welded in place, and then the strength of the connection of the box to the factory shackle mount becomes critical (as I've stated above)

I'd cut it off and start again.

Be aware too that "full" RUF ( i.e using the stock rear spring hanger) requires shock mounts to be fabricated the bumpstops moved forward, and the brake line brackets relocated due to the amount the axle is moved forward. It's a fair fabrication quite apart from the extension.

Steve.

[steve125]

The extension is 40mm solid bar so it's quite strong in itself.

I agree the connection to the chassis would be a weak point so I would add a brace like dan said.

If it can be braced, then how to attach the shackle?

The existing hole at the front of the extension is about 80mm from the centre of the current shackle. I was thinking if the hole was enlarged to at least 20mm, a small bush could be fitted. Not sure how to drill/bore out the hole to 20mm though.

A second option would be to weld a bracket underneath the extension or would this place the shackle too low?

[neofitou]

As it is solid and not crush tubes, I think perhaps cut them of and turn them around and reposition for the existing mount is at the front and in the right spot, extending the chassis to brace it and welding it all up.

You should find out first what height the mount should be at not just the distance forward, neither of my suspension books discuss front leafs funny enough, the only disadvantage I can see of it turning out too low would be decreased caster angle which would make it more twitchy (like my extended shackles do..) experience over book smarts will privale here I think.

My welder is on the way, happy for you to use it and I can also be right neibourghly and lend you a hand if you want it too. Good prac for doing mine in sept.

[greyghost]

turning out too low would be decreased caster angle

other way,
the lower the car's front springs sit the MORE castor, and the better it handles

[gwagensteve]

I think Neo means if the shackle hanger was mounted too low (i.e lower than stock) if would lead to less caster, which is correct.

Setting the car up so it "sits" lower will increase caster improving handling, so you are both right....

Steve125 - I'm even more concerned that that's solid bar. You'd have to bore a large hole in it to take a stock spring bush (approx. 30mm) and that's going to be almost impossible. Using a smaller bush is possible but it will hurt articulation, and you'll have to find something custom.

In any case, as a shackle hanger, it's going to be compromised. For RUF, the hanger only needs to come forward between 30 and 50mm, depending on where you want to set your bumpstops. That's going to put the bush pretty close to through the middle of the weld between the bar and the existing hanger. To put the bush totally on the bar will move the shackle forward too far, (60mm or so?) and a very long shackle would be required, maybe 125mm or so, to get the spring to clear the bar on full compression.

Personally, I think the compromises involved in this setup are excessive considering there's plenty of fab work in the rest of the RUF conversion, it's not worth the small perceived saving by using this bar.

Steve.

[neofitou]

turning out too low would be decreased caster angle

other way,
the lower the car's front springs sit the MORE castor, and the better it handles

um yeah. thats why i shouldnt try thinking after midnight.

[neofitou]

and why I should have un-set daylight savings time in my profile casue it was actually only 11:28pm.