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#41 Scando

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Posted 02 October 2008 - 06:02 PM

G....remove rear sway bar


I'm not too sure about this one.  I know PZG302 suggested it and I think he's a lot more switched on with car set-up than I am.  Generally a softer front bar and a stiffer rear bar will reduce understeer.  PZG302, is removing the rear bar something you'd suggest to fix chev z's problem or more something you find works well on Z's in general?  I know I got good results going from a 22mm rear bar to a 16mm rear bar but that was to reduce oversteer not understeer.  As you said, it made the car "easier to drive on throttle."

Results may vary, batteries not included, please see your doctor if pain persists.

#42 chev z

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Posted 02 October 2008 - 07:48 PM

My kumho tyres are V70A, I think I would have to set them alight to get them to  96 degrees C.I am afraid I don't know my cars caster, what is usually recommended{ how long is a piece of string], approx.  ball park starting point would help.

#43 DevilZ

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Posted 02 October 2008 - 08:47 PM

My kumho tyres are V70A, I think I would have to set them alight to get them to  96 degrees C.I am afraid I don't know my cars caster, what is usually recommended{ how long is a piece of string], approx.  ball park starting point would help.


Hi......your tires do seem like they could be part of your problem. Here's another racing site:
http://www.vcmc.ca/f...php?t-4538.html
They are saying the correct temperature range for V70 tyres are between 70 - 96 degrees C.
You might have to find tyres with a lower operating temperature or just run straight out radials
in the end. If the semi slicks dont make temperature they are just like using bald tyres.
I'd be looking at getting the right tyres as a starting point before doing any drastic suspension work as
it will be hard to acurately pick out suspension issues while the tyres aren't working right.


#44 Zeddophile

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Posted 02 October 2008 - 08:58 PM

My kumho tyres are V70A, I think I would have to set them alight to get them to  96 degrees C.I am afraid I don't know my cars caster, what is usually recommended{ how long is a piece of string], approx.  ball park starting point would help.


With the alfettas we set up, as much castor as you can get before the shock scrapes on the upper control arm is the idea.  The standard GTV that won the 6 hour a few years ago managed to pull 8 degrees (no idea why it managed so much), my car has about 3.8 degrees and could probably get more.  Not sure if the same theory applies with a Zed.

A...change tyre brand - go lower profile     B....adjust front sway bar to softest position    C....replace king springs with 300lbs alround    D....toe out 2mm    E....run neg. camber to 2.5 to 3 degrees    F....start tyre pressure at 24 psi , work up 2 psi at a time    G....remove rear sway bar       Give me your positive opinions ,or constructive criticism with reasons,  thanks again Steve


A - This may or may not help - I haven't had a look to see what temperature range other tyres are recommended to run at, but your temps do seem a little on the cold side for 5 laps of hard understeer?

B - Its cheap to try, and definitely can't hurt, although I thought you'd tried this?  Although it may bring back the body roll issue, but a hard front swaybar will definitely contribute to understeer.

C - probably a good one to do in conjunction with B, as most of the Zed racers here suggest heavier springs.  Will reduce the bodyroll issue that may arise from softening the swaybar.  The actual spring rate recommended is probably a matter for a calculator and some corner scales though.

D - Not sure?  Alfettas run 1mm toe out, but completely different front suspension setup, and I think toe is much more linked to the vehicle type than any of the other settings.

E - This would be my preferred starting point, going on the temperatures you were seeing across the tyre, and assuming you have standard camber now.  Those figures I think should be an excellent start point for the tyres you use and the intended use of the car.

F - Again, its free, and you will find out what pressures suit you best.  This is actually something you should ideally play with every couple of meetings, or after any setup changes, as you will probably find that your preference will change as your driving develops, and also whenever an alignment setting is changed.

G - I wouldn't bother with this - hard rear swaybars normally cause oversteer.  Considering the rest of your setup, this would be my last area of development.

So in summary, my thoughts would be do E.  Then take it out again with new tyres (which you need anyway now!), and play with B,F and maybe castor and see what happens.  If still having the same issue, continue to C and B.  By this point, I think you'll have a pretty nicely handling car.  Also, I have a suspicion that if you are getting the tyre more evenly on the road (with the camber adjustment), and able to utilise the lateral grip of the tyres better, you will likely generate enough heat to get the tyres into their recommended heat range.

#45 chev z

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Posted 24 December 2008 - 03:20 PM

My apologies to everyone on taking so long to update the suspension situation. Work is interfering with recreation time. Note to self, try and erradicate work.
Since my last post, I have bought and fitted 350LB front king springs and 300LB rear king springs.
Readjusted the front sway bar to softest setting.
Placed the rear medium compound Kumho tyres on the front and refitted old hard semi-slicks to the rear.
With this setup I have completed approx 250km around Winton long and short tracks. The front tyres are wearing very well and the car is certainly more stable and faster around corners. There is definately less understeer.
My intention is to take off lower control arms and rose-joint them. Hopefully be able to adjust camber out to 3 to 4 degrees.
In conjunction with negative camber I intend to set castor 1 degree positive for every camber degree.
I will leave the konis set at fully soft front and fully firm rear at this stage.
Hopefully this setup will be tested in January sometime and I will forward results.
Thanks again we are heading in the right direction even though only in small steps. 


#46 Zedman240®

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Posted 24 December 2008 - 06:34 PM

One quick note on when you increase camber on the front, you may run out of tie rod end length! As you inrease the length of the lower control arm, you have to compensate with tie rod length. There is a fix, just have to find out what it was! D'oh! I think tie rods from a late 260?

#47 chev z

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Posted 21 January 2009 - 09:03 PM

Well I have just three days to fit and adjust camber and castor redesigned lower control arms and castor bar.
I have rose jointed lower control arms .My description of this will probably be crap ,so at a latter date I hope to include some photos.
I decided on filling in the LCA mounting bolt  bush area .
Manufactured a solid bush[?] and pressed it into the LCA transverse bushing space .
Drilled and threaded this solid bushing to accomadate a 5/8'' rose joint .At this stage everything was looking OK.
Someone had mentioned that approx. 10mm was needed for every 1 degree of camber adjustment.
I discovered  I already had 45mm, so V'd out bushing to remove 17mm, hoping to attain 3 degree neg. camber min.The solid bushing was then welded into place.
The existing transverse link mounting bolt bushing was cut and used as spacers either side of the rose joint .
When attempting to find a easy quick fix for my positive castor problem, i.e. lack of + castor, I discovered that a ford XB castor arm is very close in angle and has more length and diameter than the datto . Drilled two new mounting holes and then cut more  thread [original datto diameter size] so as to have a fully adjustable castor arm using the existing tension rod bushings.
Hopefully this has eliminated any weakness that might have occurred if I had cut and welded the castor tension rod.
Finally take the Z to my Goodyear man to set up the desired degrees of camber and castor.

Now only time will tell if this will firstly go together , and with a lot of luck help my Z corner at pace.

Good luck deciphering this.

#48 chev z

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Posted 21 January 2009 - 09:13 PM

Blast, just read previous message.

I will probably need to extend tie rod length.

Perhaps I am being to optimistic about racing at Winton on Monday

#49 chev z

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Posted 24 January 2009 - 02:24 PM

Well considering I am flying pretty much blind when trying to set up the camber and castor , with the guys at Goodyears help [who generously give me a loan of a hoist]  the re-engineered lower control arms and adjustable castor rods went in place without to much of a hassle.
The only real problem being an excess of degrees attained ,4.75neg. camber,So a 12mm slice off  the welded in boss brought the degrees back to 2.8. Hopefully this will be a good starting point.
The ford castor bars fitted really well and  we attained  2 degrees of  + castor,didn't go for 3 degrees due to the fitting of 225  60  15 tyres allround ,guard space was very  limited on the front .
After a brief test drive , I decided to replace front tyres with the original 205 50 15 as  I    "Sliced 20cm of outer tyre edge when coming back thru gutter ".No futher adjustments were made due to time factor.
In the future ,a set of 225 50 15 or 225 55 15  will be tried with more +  castor  degrees .
Plenty of discussion about toe-in opposed to toe-out .In the end procrastination won.We decided on going nuetral [O ]

The most pleasing aspect of this  set up was the tie rods DID NOT have to be altered.

At this stage I am pretty happy with the setup  BUT as they say ' proof is in the eating of the pudding' so MONDAYs  testing will be interesting.



#50 Zedman240®

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Posted 24 January 2009 - 06:04 PM

Good to hear about the tie rods. I just mentioned it because I had that issue when I adjusted my lower arms to get 3' of camber on the front wheels. The adjustment on the tie rods was just on the limit of being comfortable. All that's left now is run around the track and feel what it needs!

#51 NZeder

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Posted 24 January 2009 - 06:42 PM

The tierod length issue - get some 280zx non power steering tie rods they are 10mm longer than the 240/260z units. However the catch with this is they are only RHT (Right hand thread) and the stock 240/260z racks have a LHT and RHT. I am trying to find a supplier for the inner tierod/rack end as Nissan only have the LHS (Left Hand Side) units which must be purchased with a new outer also. But these are the LHT = ahh no good.

I need to do something for my zed as when it was on the road last time the setup was such that the tierod ends were only just on the rack - dangerous so I am hoping to get 2 x RHT on the end of my rack so I can use the 280zx longer tie rods.

As the rack ends are proving hard if not impossible to find - I am thinking that I might look at changing racks so a unit that parts are available for - but I want a non powered unit :( which does not leave much choice in the front mount rack space that is narrow enough for the S30 chassis.

Enough of rank about the S30 racks. So I must say good new on the tie rods so you can sleep easy not like me....I keep thinking there has to be a solution to the inner rack end supply issues.

#52 chev z

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Posted 26 January 2009 - 08:56 PM

Just a very quick update.
A successful first up trial,in extremely hot conditions that tested both car and driver, we achieved a reduction of 2.7 sec per lap on my previous times.
Consistently lapped in the  1min 47's of the Winton long track.
The larger diameter tyres were a handicap ,just lost to much  acceleration,they also altered the gearing thru corners.Will try set up with 50's, this will give a more accurate evaluation of where I'm at .
Front tyre wear was good and the car definately turned in easier

Of course one thing leads to another .

I have discovered that in these conditions my brake fluid boils or rotors/ brake pads decide to stop working which leads to interesting exits here and there.Definitely makes driving more exciting, no interesting, no less predictable ....no make that NERVE racking.

But the best result of all, is that the re-engineered parts held together


#53 Zedman240®

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Posted 26 January 2009 - 10:29 PM

Funny you should mention about the brakes...at the last MSCA event we had a club member who is obviously getting better driving around the circuit with R spec rubber and a 3 ltr engine, discovered what "brake fade" is! As you set up your car and find it works better, you tend to push it harder and then you find the limit of the stock brakes...

#54 xa1973

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Posted 30 January 2009 - 10:58 AM

The focus of circuit chassis tuning is to remove the compliance from the vehicle, and instead make the shock absorbers and springs do the work of controlling the body.
With this in mind, every litle bit of rubber between the body and the tyres needs to be removed and replaced with solid, metal type mounts.
Many conventional bushes should be replaced with rod end or rose joints.
Removing the flexibility of the car gives the driver a more direct link between the steering wheel and the road, in turn delivering better on the limit control and more accurate use of the tyre rubber, which all adds up to more consistant and higher levels of speed, when set up correctly its easy to see how far removed a road car is from a decent circuit weapon.

CIRCUIT SET UP

SHOCK ABSORBERS              COIL OVER PLATFORM ADJUSTABLE
SPRINGS                            SINGLE RATE HEAVY
SWAY BARS                        ADJUSTABLE
BODY STIFFENING                INTEGRATED ROLLCAGE
ARMS                                 ROD END JOINTS
RIDE HEIGHT                       MINIMUM TO AVOID BOTTOMING
FRONT                               4* NEGATIVE CAMBER
REAR                                 2.5* NEGATIVE CAMBER
BALANCE                            NEUTRAL
Adjustment of the roll centre and weight distribution of the car can lead to some serious gains in lap speed, optimal camber settings can really only be determined via tyre wear patterns, a vehicle with toe out will turn into corners better, but have less straight line stability.
As with everything its a comprimise, even purpose built big ticket racers have deficiencies, but the methodoligy remains the same  :)

#55 Lurch ™

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Posted 30 January 2009 - 11:15 AM

Tyre wear patterns = tire temps which can only be determined with a pyrometer immediately after a session.
BUT camber adjustment at the track is a PITA with McPherson struts unless you have slotted towers, otherwise if you adjust the camber at the LCA you will then have to make toe changes...

#56 xa1973

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Posted 30 January 2009 - 12:19 PM

Tyre wear patterns = tire temps which can only be determined with a pyrometer immediately after a session.
BUT camber adjustment at the track is a PITA with McPherson struts unless you have slotted towers, otherwise if you adjust the camber at the LCA you will then have to make toe changes...


Gday Lurch

How was WA, I spent the best part of fifteen years in the Pilbara region, now back home in QLD

Yes, your quite correct in your follow up, my post is a basic setup for the weekend warrior

Cheers

#57 Lurch ™

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Posted 30 January 2009 - 12:27 PM

Hey XA,
WA has been good - pity I got here at the wrong time though :(
I wish I could have gotton a job in the Pilbara, but I guess it wasn't to be...

Not a worry mate - I was just being pedantic! ;D
I guess one has to weigh up how serious one wants to get when doing track work,
BUT tire temps are very important in getting the maximum life out of one's tires...


#58 chev z

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Posted 31 January 2009 - 04:06 PM

I have taken Lurches advice and procured HTX115 brake fluid. It is rated 5.1, this should help with any boiling .Plus have bought some flexiable tubing so I can duct air to the front disc brakes.

If I get time next week,I intend to upgrade the front brakes using the tutorial by Lurch as a guide. After comparing the pros and cons between S13 or Peugot rotors I have decided on the Peugot .Less fabrication and they are already slotted.
The difference in cost being only  approx. $20
Found some  S12W Hilux calipers for $80 each at a FWD wreckers.

My big stumbling block is trying to find a 280zx brake master cylinder ...CAN ANYONE HELP



#59 Lurch ™

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Posted 31 January 2009 - 09:45 PM

Steve, you can buy them new for around $200.
PM Dimitri (Zedman240) for more info.

#60 chev z

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Posted 02 February 2009 - 10:05 AM

Going to Shepparton Tues. , I will try to procure brake master cyl.

A change of plans as of this morn. , the Peugot slotted rotors have been revalued at  $260 a pair as opposed to S13 slotted at $210
Apparently forgot to add slotting cost.
Oh well it has been extremely hot up this way ,so brain malfunction malfunction malfunction[lol] can be forgiven.

I am thinking of using Lucas brake pads,apparently work well,cheap but dirty...two out of three ain't bad.
Any other pad ideas worth considering?




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