Front Subframe Strengthening

[Alan_M 66 1 Cars]

I was always under the impression that given the size of the box section on the front subframe that strengthening it either by welding or the addition of a lower strut brace was worthless.

 

Now I find on Ebay at the AB Motorsport shop, they sell a strengthening kit.

 

AB Motorsport Subframe Strengthening kit

 

Has any of the rally/race guys on here had any experience of this kit, or even the results of welding up the subframe and the addition of the lower strut brace?

 

I've heard the OMP lower strut brace is a bit pants, and something a bit meatier is required.

[swordfish210 20]

You can buy seam welded subframes from X-Sport. awhen i'v got my subframe out and it's been bead blasted i'm going to seam weld it just for the hell of it . As for the strut brace i als thought the OMP one looked a bit weedy so i'm going to make a much chunkyer one and test it myself to see if tit makes any difference

[Rippthrough 98]

Consider you may be putting over half a tonne of force on that box section, plus shock loads, and that it's only spot welded, so it can twist on the welds.

Now consider how much difference there is when your tracking is changed by just 1mm.....

 

 

Doesn't need much flex to make a difference, seam welding with gussets would be the best way but a beefy lower brace works well.

Edited December 28, 2007 by Rippthrough

[Dan Ingram 1]

Apologies if I sound a bit think but what exactly is meant by seam welding the subframe ?? Do you just weld up any joints that haven't been done already or is there a lot more to it?? I'm only asking because I have mine off at the moment and have a welder so I may as well do it while I can.

[jonnie205 1]

i think for a rally car or high spec race car where massive loads are being put through a subframe only designed for road use then yes its worth doing along with the other strengthening plates in the kit. The plates and seam welding are only as good as the fabricator fitting them, bad welds can weaken the structure by givin the metal a point loading if only the slightest hole or weak area is created by too much heat or a contaminated weld

[Baz 421]

You weld the seams of where the 2 pieces of metal join.

 

The existing ones are just a small spot weld as Rippthrough said. I'm going to stitch weld all round the seams, about an inch at a time, then leaving an inch or two between each, this should be enough, but not doing too much in one place at once, leaving time for cooling, you don't want to stress one area too much with too much heat.

 

The added gussets that i presume would come with that kit might be a good idea too.

[Dan Ingram 1]

I think i'll do that then. Seems daft not to while its off the car

[Baz 421]

Yes, agreeing with Jonnie's points, i don't think it's all that worth it on just a light used tarmac/track toy tbh. I'd spend the time on the strut top, engine bay and rear beam mounting points strengthening instead.

[Rippthrough 98]

Get some weld through primer down beforehand though to protect the backside of the steel, I mount mine on a flat jig to stop the metal distorting, it's also a good idea to work from the centre outwards stitch welding on alternate sides to keep the heat concentration down.

Edited December 28, 2007 by Rippthrough

[Dan Ingram 1]

How does weld through primer protect the backside of the metal?

[Rippthrough 98]

How does weld through primer protect the backside of the metal?

 

On the weld itself, otherwise they tend to rust from inside out, last thing you want in a seam weld is some rust appearing, they crack then.

[Dan Ingram 1]

Ah I see, excellent thanks

[JamesLumley 4]

I've always used a std suframe on the rally car but with the new build I'm having a strengthened frame made. Once you stiffen up the shell the load is transferred elsewhere and ultimately something has to break - bottom arm balljoint/ track rod end/subframe etc.

 

Ideally this wants to be the driveshaft as they are easy to change, relatively cheap and don't cause much damage when they give way.

 

Some good advice above as to what needs doing, I'll post some pics when mine is back from the fabricators.

 

Oh and I'd say pretty pointless on a road car, there are other things to better spend money on first

[Miles 331 1 Cars]

I seem welded mine as it cost nothing to do, But the brace I think does help a little as the front of the Wishbones are out on there own really.

Not sure if it fit's thou on S16 or GTi6 engine's

[jackherer 543]

I seem welded mine as it cost nothing to do, But the brace I think does help a little as the front of the Wishbones are out on there own really.

Not sure if it fit's thou on S16 or GTi6 engine's

 

The brace (just) fits with an S16.

[Alan_M 66 1 Cars]

Just bringing this up again,

 

So is the OMP type lower brace worthwhile even though its weedy?

 

And when you say is doesn' fit Gti6/S16 lumps, what about Mi's with GTi6 sumps (like mine)?

[Dan Ingram 1]

I'm sure it must help even though its not very noticeable. The rear of the subframe already has a brace on it so I'm sure the front one will help. I've got one on mine and I've added some extra welds as well I've no idea if I'll notice it or not, looks good though

 

[Rippthrough 98]

I certainly noticed with mine, as did the others, but mines a bit beefier.