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ActionDan

Car too firm/skittish/struggling for grip.

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That's about what hot pressure I had I beleive, 30-32.

 

I'm in Albury/Wodonga (NSW/VIC Border)

 

After a bit more reading and discussion, this is my plan.

 

- Raise ride height front and rear to get LCAs flat when stationary and improve roll centres. As I understand it, this will cost me camber front and rear, So I'll do this first and see what camber I end up with and decide if bushes/slotting subframe mounts is needed to get me back to where it was, I may actually back the camber off up front.

- Get caster arms, aim for 7.5-8, pending clearance which should help dynamic camber up front.

- Make a call on rear camber amount pending changes to camber after ride height change and balance that with ability to put power down.

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Hard race caster arms that have the big rubber bushing are the best. I had rosejointed rods and they wore out pretty quickly due to daily driving. track car might be OK.

 

I have about 7 degrees caster thanks to the adjustable arms. running MCA blue coilovers at 6/4 on the softest setting. running 1 deg camber on the front and around 2.5 on the rear with a tiny bit of toe in.

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Why would you back camber off in the front? Riddle me that! Also how is the rake on ya vehicle? Hub to guard measurements? On my s15 I found having the rear 5mm low worked best for neutral handling. Can u tell us what your hub to guard measurements are on your car?

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What size tyres are you running? I'm not asking questions cause I like typing lol

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Why would you back camber off in the front? Riddle me that! Also how is the rake on ya vehicle? Hub to guard measurements? On my s15 I found having the rear 5mm low worked best for neutral handling. Can u tell us what your hub to guard measurements are on your car?

 

I did have them, some like 350-345mm or so sounds right in my head but I'd have to double check.

 

It was suggested by someone far more knowledgeable than me that 2.5 would be enough for these tyres if caster was also set properly.

 

 

What size tyres are you running? I'm not asking questions cause I like typing lol

 

235/45/17

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Double check n let me know. I'd lean more on around 3 degs in the front with castor no more than 8 but not less than 7.5.

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Car is on stands right now. Will buy castor arms and aligning gear in the next few weeks and sort that then look at the calendar for a track day.

 

Might get those skyline rear calipers and rotors on too.

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dont forget you need the drum hand brake (if you run a handbrake)

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I'll just buy the hydro kit from holfords, cheap enough, or go without hand brake as I'm not into motorkhana.

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What kind of diff are you running?

 

Looks at times in the video like it may even be single wheeling.

Otherwise it seems you are also driving reasonably aggressive, 8/6kg spring rates are fine

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Standard viscous diff and yes it sounds like it's open wheeling. That doesn't account for the front end wear though.

 

As for aggressive, do you mean shitty lines and nput? I am certainly not a skilled driver. Heel/toe double clutching is the only remotely "race" thing I can do, the rest is all hack work :)

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As for springs, I've had 2 comments.

 

MCA told me they never run spring rates that high in S chassis and stick with stock swaybars. Pedders in Bendigo who campaign an 86 in the GT series run 10/6 in their car and it goes well (an would be similar weight).

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Are you going to listen to the guys that built a S13 that can beat evos at WTAC or the guys who campaign a hairdressers car and tell your grandma she needs new headlight fluid when she goes in for a pink slip?

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LOL

 

I should add that MCA followed it up by saying I should definitely buy a set of his coilovers as a satrting point etc. Not surprising given they're in business to make money though.

 

Drummond Motorsport, who make shocks for tarmac and gravel rally cars - http://www.dmshocks.com/ - Said he was far less concerend about spring rates and said don't do anything til you fix the roll centre either by raising the car up or putting RCAs in it.

 

I started removing the LCA and caster arms last night so they can be replaced. I'll do the subframe bushes in the rear also and see where that gets me LCA parallel wise.

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Im pretty happy with my MCA blues, I wasnt struggling for grip at Wakefield on street tyres. only had a few skids when I was getting back on the gas too early.

 

same springs as he suggested.

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No doubt the product is good, but I'm not looking to replace the shocks right now, they'd be lucky to have done 5000ks.

 

If I need to I'll replace the springs with lower rate.

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I guess this raises an interesting point of discussion. You're going to great lengths to correct a problem that I have never experienced on my car, yet both cars are the same (give or take)

 

perhaps im not driving at the limit as much, or you are driving over it?

 

I often wonder how much someones advice on parts and setup is clouded by their driving ability (for good or bad) and how you can correctly determine whats best for your own setup.

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Completely agree, to be honest it's all guess work.

 

I'm a a very average driver by all accounts and a very average mechanic (I say that because I built/developed/tuned/aligned this car).

 

I could probs hand this car over to someone with half a clue, watch them change a few settings then go out and drive it properly and kill my lap times.

 

All that said, every time I mod something I learn something new, this time it's been about castor and roll centres.

 

Part of me also thinks I am asking too much of these tyres sometimes and that I "might" be ready for something a little better, but before I drop dollars on that I want to get the alignment back to being kind on rubber.

Edited by ActionDan

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I'll wade in to this and give another opinion...

 

With shocks etc, you get what you paid for. I understand not everyone can afford the good stuff, but some cheaper stuff is better than others.

 

The majority of cheaper stuff i have run across the shock dyno have terrible damping rates that are not matched to the spring rates or the cars they are sold for. In a lot of cases they have the same valving front and rear, and in many cases same between completely different cars. Obviously much cheaper to just have a couple of valve setups to choose from rather than actually develop something to suit.

 

Generally they also have 32 clicks of no or very little adjustment.

 

But back to your car...

 

In my experience those spring rates are too firm for your setup. If you were running better tyres or possible some aero, no problem. But on road tyres, with little to no aero they are too stiff. Especially in a flexy S13.

 

I would be looking at 5/4 or 6/4 if you are planning on getting some better tyres.

 

When i was running my original S14 i ended up on 7/5 running 255 proper semis all round. This was good for 1:06 at wakefield with no aero and only 200rwkw. But this was only part of a good package.

 

As far as swaybars go, i prefer more over less (especially when combined with lower spring rates). On my S14 i actually drilled another hole in the swaybars to get a stiffer setting. Then both front and rear bars were on full hard.

 

As for alignment, only real way to tell on this is by doing tyre temps at the track. But i would definitely be putting new castor rods in. Chances are your original ones are stuffed and is part of the reason why your car feels nervous in the front. Especially after you added the swaybars as this would be putting more load through the bushes.

 

Your current settings probably aren't that far off the mark but i would think a little more camber all round (-3 front, -1.5 to -2 rear) with a touch more toe out on the front (max 3mm total) should be about the mark.

 

But once again you should be using temps to dial in optimum camber. If you go to a proper semi you will need increase neg camber all round as well.

 

Might find the RS-R need a little more pressure to be happy as well.

 

As for roll centres, honestly its one of the most overhyped areas of setting cars up and is one of the last things i look at to gain speed. Dont get me wrong, it is important, but the cost vs benefit of correctly measuring and setting up perfect geometry is not great.

 

You will gain a lot more for a lot less by getting the rest of the setup right.

 

On my old S14 i ran standard geometry. On our S14 time attack car we are still running standard geometry. Haven't even raised the subframe. This car is in the 1:02's at wakefield (with plenty more to come) and 1:35 at SMSP.

 

But both cars are setup at a sensible ride height. Its only when you go too low that things really start to get bad.

 

If you want to get in touch outside of forum land drop me an email at jonathon.mckinnon@bilstein.com.au

 

Cheers.

  • Upvote 1

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Much appreciate the response.

 

I'll see how I go with these changes and look at where to go from there. Perhaps springs are the next step, I don't really want to fork out 2-3k for new shocks.

 

I don't doubt my shocks are cheap, but I can tell you there's a notable difference in how the car feels between damper settings.

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I just looked at the MCA blue, didn't realise they were $1500... I wonder what I could get for these BC's....

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As for roll centres, honestly its one of the most overhyped areas of setting cars up and is one of the last things i look at to gain speed. Dont get me wrong, it is important, but the cost vs benefit of correctly measuring and setting up perfect geometry is not great.

 

Good to know. I haven't seen resources quantifying the difference and I assumed RC correction was a big deal. By the sounds of it, it's more of an optimisation.

Edited by Skepticism

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MCA seemed to think it mattered and given I needed new ball joints anyway, it made sense to get those arms with new inner bushes and the RCAs already fitted (plus the Caster arms as a package).

 

My point is not to disagree, but to point out there's a few ways to skin this particular suspension cat.

Edited by ActionDan

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Im not saying that roll centres do not matter. On the contrary they are important, but the average punter will (generally) not be at a level where less than optimum roll centres will be stopping them from going quicker.

 

It is also very easy to make matters worse when just throwing components at a car. I.e. by introducing bad bump steer by changing LCA angles without addressing steering arms etc. Or by only changing one end of the car, or one end more than the other.

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I'll be changing the rear end with subframe bushes and changing ride height if required to get LCA's parallel all round.

 

I'll look at t the tie rod angle and buy the correcting mis-aligningment kit if need be, that's why I'm doing the front end first. If I need the alignment kit for tie rods, will buy at the same time as the subframe bushes.

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Thoughts on me buying 4kg rear springs and putting the current 6kg rear springs in the front? Do the lengths work.

Edited by ActionDan

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it doesnt mean shit if your valving isnt matched.

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So why would companies sell alternative springs if you wan't swap them without changing the entire valving of the shock, essentially meaning new shocks.

 

Are we talking F1 level discussion here as in it will not give me the 11/10ths of performance or will it "work" but not be ideal?

 

There's a diff between working "well enough" and no this is a terrible mistake.

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Don't mess with roll centre shit, your running crap bc's roll centre adjustments shouldn't even be mentioned. Remember Murray is the master behind Mca not josh. Regardless of this, who put your suspension in the car? Did you set bump and droop travel on installation? Read up on this on the Mca website, also Mac will tell u to leave roll centre shit alone. You can't run before you walk.

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Too late. Everyone agreed that arms at parallel is a good thing, that's not "messing with" something if the plain version is simply that parallel is a good thing. If the RCA's aren't long enough I'll also raise the ride height to get LCAs parallel.

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