Subframe Modifications For Your Track Car

[Simon-S14]

As many of you know. when you lower your nissan excessivly at the rear strange things happen to the geometrys.. also the driveshafts run at bad angles leaking to breakages and the handling of the car starts to go backwards. Most ppl will tell you to raise the car.. but wheres the fun in that! Anyway what you CAN do is correct the roll centre at the rear by raising the subframe up into the body by half an inch and effectibly flush mounting it. this way you can have a lowered car and correct the roll centre back to where nissan intended (somewhat).

If your running the traditional style alloy cradle bushes or pineapples on top of the subframe all round you have actually made things WORSE by lowering the subframe. sure in the case of alloy cradle locks its only 10mm but still.. its not an improvement.

I'll show you what i did by myself in my garage. pretty much done for a total cost of $120. that was to pay for the new bushes. everything else i did myself.

THE PROCESS

Start by ripping out the entire subframe.. with diff, arms and everything still attached.. all i took off was calipers and left them attached to brake lines to save bleeding brakes. i cable tied these in place.

Once the rear cradle is out... strip it down bare. remove everything til its just a bare cradle.. then go give it a wash with soapy water, degreaser and leave it in the sun to dry. then chuck it on the bench to start work,

Start with bracing the subframe... its a good idea to do this while its out as they are reknown for cracking the lower control arm mounts when tracked. I went a little over the top and bracked areas where i saw fit... do what you want in this area.

In this pic i braced the toe arm mounts together, cusco make a toe arm brace.. but why pay money when some steel and welding can do it for nothing. It has also created a new jacking point more rearward of the car for me. this is 50mmX6mm flat bar btw.

middle re-enforcement

here i have used a small amount of flat and encased the mount for the rear LCA.

and otherside

I chose to weld these triangle sections in... its not a known weak spot on the subframe but i had the materials, time and thought why not.

Both sides

Next up is getting the stock rubber bushes out... this is a prick of a job and there are several ways to do it... the easiest and messiest way is to use an oxy and melt the rubber out and then an air saw to cut the sleve on the side to allow it to fall out after some taps... I chose to press them out using a simple garage 20t press and this still required the use of a hammer and chisel.

Next up... i threw some paint on it to stop exposed area's rusting. up to you

Also got some new Cazman arms to replace my shitty china spec shit.

Got some Subframe bushes machined up. this is a design that me and a mate came up with and seems to be good so far. they will allow the subframe to travel up into the body by around 35-40mm.

They then install into the subframe.. designed to be a snug fit not a press fit. they will tap in with a block of wood to protect the alloy and a hammer.

they only go in one way

Now you can bolt it in. the shot here shows it test fitted but i find it easier to re-assy the cradle with all the diff/arms and hubs before refitting. Pics show bare cradle so you et the idea of clearances.

Watch the handbrake cables... they do have the potential to be crushed if your not routing them correctly. may have to bend a bracket here and there to make sure they clear

Nice and close... can fit a sheet of paper between the pick up and mount haha

So there you have it kids.. an easy mod you can do at home. Subframe bushes can be had for around $150 so if your handy its not an expensive exercise at all to stiffen up the rear end and increase the handling of your car.

this can be carried out on any Nissan IRS rear end.. for what its worth this is a S14 cradle.

Article by Simon Michelmore

2010

[Curmi]

thats a great write up but useless, unless you are prepared to strip the whole rear of the car..well done anyway ,i am about to do alloy subframe bushes those ones you made look awesome

[Simon-S14]

not really that useles... any one could do it.. even for a street car if you coulfd put up with the harshness

[08yannch]

4 the mentally slow such as myself what ar the benefits of a mod such as this and also how much harsher will the ride be after this. im guessing this is not 4 the daily driver

[Simon-S14]

its explained at the start of the article what it mainly does. correcting roll centres and stiffeing up the cradle.

yes the ride will be harsh, track or for the brave only

[32_Dave]

f u c king unreal article bro, i have done all these mods minus jacking point good idea.

and its unreal i recomend this for all lowered cars.

[Simon-S14]

cheers mate

further note... measure the steel that your weld in for the toe arm/jacking point brace if you do it.. mine misses the diff backing cover by mere millimeters lol

[Rowdyr32]

As many of you know. when you lower your nissan excessivly at the rear strange things happen to the geometrys.. also the driveshafts run at bad angles leaking to breakages and the handling of the car starts to go backwards. Most ppl will tell you to raise the car.. but wheres the fun in that! Anyway what you CAN do is correct the roll centre at the rear by raising the subframe up into the body by half an inch and effectibly flush mounting it. this way you can have a lowered car and correct the roll centre back to where nissan intended (somewhat).

Just a question. How are you correcting the roll centre of the car by lowering the bodies mass further down towards the ground in relation to the suspension geometry. Most people run their cars higher because you need the mass of the car higher to to apply the weight onto the wheels. Wouldn't you need to run massive roll centre adjusters/spacers on your lower ball joints to now correct your roll centre through suspension geomentry? It just goes against what I have been told.

Possibly you should have raised your lower and upper arm mountig points on the sub frame to correct for the lowering of the centre of gravity. I think I have read one of the track guys (Duncan?) did the same mod as you but rasied his sup mounting points to correct geomentry. Its about the cars mass centre and something to do with an angle through your susp arms to where they land on the ground. Your mod would have pushed it out way beyond the wheels?

Its a really good mod to keep your driveshafts in one piece and its also good to see people out there actually working on their own cars and having a go.

Let me know if I'm completely wrong?

[Simon-S14]

yeah you've got slightly wrong.

Your actually raising the subframe further up into the body not lowering the car down onto it.. the difference is the ride height does not change since the strut length is still the same.

when you lower the car by a fair amount two things happen. the axles have a tendicy to break and the susp arms are all at bad angles. your roll centre is also lowered beyound the factory setting and you induce jacking of the car during cornering. there is more leverage acting on the arms and you end up with more body roll rather then less.

by moving the subframe up all the arms get a little more towards where they should be, as well as the axles. and your roll centre is further up towards where nissan intended.

guys who have pineapples sitting between subframe and chassis are just making things worse by again excessivly lowering the subframe and increasing angles.

cutting and relocating mounts is a painful to go about doing things. and even then wouldnt fully correct the problem.

[32_Dave]

simon post pics of how your LCA now sits with your car lower. mine are pretty well dead flat. also with the front have you re-drilled your LCA / Castor arm up higher to recorect the front?

ps: im not gona add a jacking point in, its all back in the car

on another note... hows ya lock situation. i designed a weld on knuckle (based on a jap brand) which corrects geomatry in the front end and also gives epic lock. im looking at getting some made (not sure on cost yet), if your keen

pics on 32. (17x9.5 + 15) lca lengthened 20mm so -5 offset effective

Edited May 8, 2010 by 32_Dave

[Simon-S14]

nice this is the one thing i wanted to do with my 32 but never did! ive got modded knuckles in my s14 tho... goes pretty good with decent lock

[32_Dave]

here is my rear arms.

subframe riser bushes FTW

[Simon-S14]

nice have you got a pic of your ride height?

looks like stock ride height arm angle in wich case your on a massive winner!

[32_Dave]

i was waiting for that its not epic low, but as it sits its perfect.

again 17 x 9.5 + 15, sorry no pic of the front in this shot. just out of paint in my homebooth

[32_Dave]

and no it doesnt scrub im thinking of pulling them further to make it more street friendly

[Simon-S14]

nice wheel choice... i do like the cst's!

thats roughly where my ride height is also so good to know. looks like a sweet build either way!

[nsmo30tt]

ahhh.. only if I knew it wasnt too long ago I spent an entire weekend taking my rear subframe out to change bushes... annnnyway I was wondering will those solid bushes be ok for a daily street driven car?

[Simon-S14]

after some extensive testing yesterday i can say this is the most awesome mod done to my susp yet.... so much better to drive now!!

and no i wouldnt recommend it for a street car... the NVH levels go through the roof.

It is possible however to raise the subframe but not go the alloy bush route.

[nsmo30tt]

whats the best option to raise the subframe for a street car.. I just have noltec "drift" subframe bushes.. and good bushes or other mods you could recommend for a street car?

[Simon-S14]

you would have to modify some noltec bushes to suit a raised frame... bit of work but doable for sure