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3.9 seconds quicker at SMSP after large increase to Spring Rate - Vid in post.

25GTV

By 25GTV,
in Motorsport

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25GTV Experienced

25GTV

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Hi guys, I spent days researching spring rates for skylines (particularly GTT R34s) the general info was that 8/6kg setups were too stiff for the road and many said even too stiff for track...  

My car felt way too soft on the track and still too much body roll after doing a larger front swaybar.

I went from 8/5kg to 14/8kg and the car felt amazing and no where near too stiff on track.  The car was also lowered 20mm when the springs were changed.

Result was a 1.547 around Gardner Circuit at SMSP which is still slow.  If you watch my vids, the car is very slidy which is fun but slow and rear grip is the next step.

 

https://youtu.be/PjyTZ4dOq0M

 

Basic info:

Front Tyres 235 Zestine 07R

Rear Tyres Chinese 265s

220rwkw 12 psi

Locked Diff

Drift knuckles (ex drift car)

Shockworks coilovers

Whiteline 24mm F swaybar

Ext front LCAs, basic adj rear arms.

Stock brakes

Bucket Seat, Half Cage and still has climate control.

 

 

Edited by 25GTV
Trying to embed yt vid.
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hattori hanzo Community Regular

hattori hanzo

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went from 8/6 to MCA Red 13/10 (IIRC) and dropped a similar amount of time around barbagallo 

stops the weight transferring diagonally across and understeering  

set the ride height to the correct spec from mca website also makes a world of difference, it is a little higher than you would first suspect 

 

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25GTV Experienced

25GTV

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168km/h on the gps into Turn 1.  Still not completely confident turning it in and I roll off the throttle after the finish line then coast turn 1.

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Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

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18 minutes ago, 25GTV said:

168km/h on the gps into Turn 1.  Still not completely confident turning it in and I roll off the throttle after the finish line then coast turn 1.

wow that's pretty good!

I'm still a massive chicken shit and the fastest I've been was about 140km/h

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25GTV Experienced

25GTV

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31 minutes ago, Dose Pipe Sutututu said:

wow that's pretty good!

I'm still a massive chicken shit and the fastest I've been was about 140km/h

It's a bit scary...  Especially with a locked diff and zero aero.

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Duncan Grand Master

Duncan

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Hi mate, glad you are enjoying your time at the track and looking to get your times down.

In my experience you will have more fun and way more lap time success changing things in the following order:

1. check wheel alignment

2. r spec tyres on spare set of rims

3. sway bars (stiffer springs are not the best way to reduce roll as they act in all compression conditions not just roll)

4. shocks and springs (lighter than you have)

5. mechanical diff

6. better pads and discs

7. replace sure all bushes, ball joints, rod ends etc 

8. more power

At the moment it is pretty clear from the video that it understeers mid corner (need more front end grip) and oversteers hugely under power on exit (needs more rear grip). Good tyres will make 200% difference to both of those and you won't really notice the effect of any change until you start with some grip.

Yes (comparably) stiff springs can be OK for track only use, as long as you stay off the ripple strips etc because they compromise the amount of time your tyres spend on the ground over bumps.

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25GTV Experienced

25GTV

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You're probably right Duncan, thanks for the info.  Unfortunately the car budget has very little funds available, so...  

I have in the garage a spare s15 Helcial diff that I believe I can swap the centre and run s15 shafts.

Also, I can add some camber and toe in the rear for free.

The front tyres will have to wait for additional funds...

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Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

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Anti roll bars are very hot topic, I'm personally not a fan of the super stiff setup. From my personal experience, I prefer upping the spring rate (I'm planning to myself, especially for SMSP).

Since Matt's car already understeers, I would not be adding a front ARB, however introducing a rear should aid in it clocking better, however with a slight compromise as the car would snap oversteer much easier.

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GTSBoy Grand Master

GTSBoy

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7 minutes ago, Dose Pipe Sutututu said:

Since Matt's car already understeers, I would not be adding a front ARB

He has massive front spring rate AND a 24mm bar. It has a lot of roll stiffness in the front. It's really no wonder it wants to mid-corner understeer.

I suspect fixing the rear will come down more to getting rid of the welded diff and looking to the wheel alignment, and possibly bump steer geometry.

Plus tyres. The reason the V8 Supercars can get away with spooled diffs is the massively sticky slicks. Just watch how slidey they get on corner exit when the tyres go off.

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GTSBoy Grand Master

GTSBoy

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1 minute ago, Dose Pipe Sutututu said:

I would set it on the softest setting to aid front end grip, waits for everyone to flame me for saying that LOL

If keeping the big springs, I would drop to a 22mm, or something. Maybe even a stocker.

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Komdotkom Rising Star

Komdotkom

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Wow, your mid corner grip is terrible.

Put some toe on the back, get some cheap track tyres like AR1's and ditch the locker. If the car is super low you might want to consider changing the sub frame bushes to solids or zero height units at the back and raising the rear, same ride height but your rear geo will be closer to standard giving you better camber and toe curves.

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Duncan Grand Master

Duncan

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I urge you not to make any further setup changes until you put some proper tyres on it. There is no point trying to improve on a flawed foundation, you will likely find it handles totally differently (strengths/weaknesses) with new tyres.

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25GTV Experienced

25GTV

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The mid corner understeer is probably majority linked to the Drift Knuckle geomerty (extra lock knuckles).  In general they destroy everything whilst giving big lock.

I will say it is great fun to drive like this, predictable when the low grip limit is pushed.

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Kinkstaah Grand Master

Kinkstaah

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I mean, I didn't drive your car and I am no expert track driver myself, but watching the video makes me think that car handles like an absolute uncontrollable bucket of shit.

I know you've drifted it, but if my 34 sedan started behaving like that it would have ended up on it's roof about five times trying to go around a corner with my hamfisted driving. That exit onto the main straight should absolutely not be a mission like that, in any car ever. It's not only rear grip being the issue there. This is an alarming set of tyres at the very least as mentioned.

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