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Stuffed (new) Front Bushes

djr81
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Beer Baron Grand Master

Beer Baron

Posted
Posted

yeah you can cut a standard upper arm in half and shorten it. but you would need some good measuring skills, and some good cutting, and some good welding, otherwise it's prone to go bad. but i guess if you did the cut and shut job and used the offset bushes then you could dial out whatever error you had in manufacture.

djr81 Grand Master

djr81

Posted
  • Author
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yeah you can cut a standard upper arm in half and shorten it. but you would need some good measuring skills, and some good cutting, and some good welding, otherwise it's prone to go bad. but i guess if you did the cut and shut job and used the offset bushes then you could dial out whatever error you had in manufacture.

First up - thanks to all for their input - this has turned out to be a rather illuminating thread - somewhat better than the usual "which BOV is the sickest sounding" :)

It is not just the length of the arm that the accuracy of manufacture is important for. You need the two bush housings to be parallel & also there is an offset built into the upper arm that makes the outside of the arm forward of the rear of the arm - so that needs to be accurate as well.

A few other things (Mostly my opinion about stuff):

1. The Whiteline caster kit gives you compliance but not adjustability. This is why I am running a rod. Maybe if I could weld a thread up to the fat arsed offset bush & link it to the turnbuckle on the caster rod...

2. Early R32 GT-R's run very little caster & the different models carry different amounts (more on the later ones). Also GTS-T's are different to GT-R's, so please be careful when talking caster as it is model specific. The whiteline track setting for caster on an R32 R is only about 2 degrees (from memory).

3. Bump compliance should be about maintaining tyre adhesion, rather than avoiding suspension geometry issues. Unfortunately, in this case the caster needs to be reduced to prevent the top bush from shitting itself. Probably less of an issue with Whiteline rods as they have more compliance. My ride height of 350mm front should be enough to not to have to worry about it.

4. For my ten cents worth using upper arms with a sliding, bolted interface is a recipe for pain & suffering. I would hate to think what would have happened in my case if I had have been using such things. :rofl:

5. The combination of a big yump (bump that goes down) in the right hand corner of one of the local tracks will pretty much always put the front suspension on the bump stop. Combined with a reasonable amount of lock & you have a heavily loaded suspension. So it would pay people to have a think about their local track & decide if their circumstance is similar. Less caster or a compliance bush instead of a rose joint may be needed...

Beer Baron Grand Master

Beer Baron

Posted
Posted

all i know is i love caster... haha

i may try one of the dog bone looking upper arms around. apparantly they can twist in the middle so that takes away a little of the load being applied buy the shorter caster rods.

djr81 Grand Master

djr81

Posted
  • Author
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all i know is i love caster... haha

i may try one of the dog bone looking upper arms around. apparantly they can twist in the middle so that takes away a little of the load being applied buy the shorter caster rods.

The other thing to be a little careful is with too much caster the front of the tyre can (& will) rub on the guard liner. Not earth shattering, but just something to be aware of.

With more caster the inclination (kpi???) of the upright changes, ie the bottom moves forward. With more negative camber the top outer link effectively moves forward thereby partly cancelling each other out. So you get a longer wheelbase for your money. Mmmm, LWB GT-R, just like a Fairlane, really. :D

Beer Baron Grand Master

Beer Baron

Posted
Posted

yes, my front tyre is very close to guard liner now running 245/45/17 semis. actually it may be 245/40 cant remember. so cant really run much more caster.

yeah LWB GTR sounds like a go... haha.

whitesky Contributor

whitesky

Posted
Posted

Hey DJr81,

nasty job on those bushes. I've been reading a few posts tonight and came across you a few times, we all seem to be attempting to dial out the understeer on our 32 GTR's.

I'm running these midori style upper arms now on mine, but havent been able to get the full amount of neg i wanted ( only 3 deg neg full wound in). It all helps but i was hoping for more adjustability.

post-23000-1147871142.jpg

Saw you at Barbagellos at xmas sprint ( i was still running road tires as only just got the thing licensed week before) hence my 1.03 eek.

Sydneykid Grand Master

Sydneykid

Posted
Posted

Most of the “retail” camber kits are designed to REMOVE the negative camber that occurs when Skylines are lowered. This is because the “road car market” is far larger than the “race car market” and they are looking at excessive inside tyre wear as the major problem that they need to overcome by adjusting the camber.

Keeping that in mind, the standard R32 style upper control arm is around 190 mm long, centre of the outer bolt to the centre of the inner bolt. Using the off the shelf adjustable, offset, outer bush (Whiteline etc) reduces that to 184 mm. This gives around 2 to 2.5 degrees of negative camber on an R32 with a ride height around 355 mm centre of wheel to guard with around 6.5 degrees of caster on a 2wd and 4.5 degrees on a 4wd.

That is usually enough camber/caster, provided sufficient anti roll is used (larger stabiliser bars), for most circuits. High speed circuits with long sweeping radius curves (eg; Philip Island) need slightly more camber.

So we use the off the shelf adjustable, offset bush (Whiteline etc) in the inner of the upper control arm. That reduces the length to around 180 mm. This gives around 3.0 to 3.5 degrees of negative camber on an R32 with a ride height around 355 mm centre of wheel to guard with around 6.5 degrees of caster on a 2wd and 4.5 degrees on a 4wd.

This 180 mm length seems to have been the minimum that ALL of the R32 camber adjusters have been made to. All of the brands of upper control arms that I have measured (Midori, Noltec, Nismo, Ikeya etc) all stop at 180 mm or longer. So choosing one brand over another to get more negative camber is pretty much a waste of time.

Enough of the theory, let’s get onto the practical stuff……………….

I do a lot of suspension set up clinics and when I hear guys say that they need/run more than 3.5 degrees of negative camber and 6.5 degrees of caster, 99% of the time they have insufficient anti roll. If you don’t have a 30 mm adjustable, solid, front stabiliser bar for 2wd or a 24 mm adjustable, solid, front stabiliser bar for 4wd then the front anti roll is insufficient. If you don’t have a 24 mm adjustable, solid, rear stabiliser bar for both 2wd and 4wd then the rear anti roll is also insufficient.

That’s where I always start, rather than trying for more negative camber which is simply a band aid for the real problem of too much roll.

:thumbsup: cheers :)

djr81 Grand Master

djr81

Posted
  • Author
Posted
Beer Baron, i got mine from Ken at Hyperdrive here in WA. But you can also buy them from UAS.

They are on their website for $495 under product cat, GTR http://sard.com.au/

Hope this helps.

Hey Whitesky - I have a question about those upper arms. Do they allow the inner link to rotate about the lateral (ie left/right) axis? The reason I asked is that if they do they may go some way to reducing the load imposed on the back end of the upper, outer bush that occurs when you wind in caster. Will have to hurt my brain and figure out if that is actually possible...

Didn't see you at the twilight (January) SES round what happened?

By the way don't, under any circumstances listen to Ken's set up advice. I'd hate for you to suffer the burden of going faster than me. :thumbsup:

Beer Baron Grand Master

Beer Baron

Posted
Posted
Hey Whitesky - I have a question about those upper arms. Do they allow the inner link to rotate about the lateral (ie left/right) axis? The reason I asked is that if they do they may go some way to reducing the load imposed on the back end of the upper, outer bush that occurs when you wind in caster. Will have to hurt my brain and figure out if that is actually possible...

the ones i looked at do allow that. that's what i was talking about earlier in the thread. :unsure:

whitesky Contributor

whitesky

Posted
Posted

yes they do allow rotation, they are solid mounted with bearings in each end.

you can adjust them on the car, although thats a bit of a waste of time, as most peeps just max them out and leave them there.

Yes dude, they are on the car, also have bilsteins, Re55's now too. Bigger front bar next and i think its all starting to get there.

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