DavidM

We have new tyres on the HSV R8 ... they are Continental SportsContact2. They have now about 1000km so I figured that I'd get the ruller out and measure the actual contact-patch. Interesting results when you compare it to the contact-patch on the OME RE040s on the Zed (Track), and what the S2000 came with:

- ContiSport2 235/40/18 (HSV R8) = 220mm
- RE040 245/45/18 (350Z Track) = 210mm
- RE040 225/45/18 (350Z Track) = 200mm
- S02s 225/50/16 (S2000) = 220mm
- S02s 205/55/16 (S2000) = 200mm

So, as you can see, the 350Z Track tyres are relatively thin ... the 245s are 1cm thinner that the 225s on the S2000 or the 235s on the R8.

I'll measure the contact-patch on my spare rims with R-spec 245s when I'll pull them out on Saturday ... but I'm pretty sure that those are wider than all of the above.

ps. When it will come time to getting new tyres, I'll see if I can find something in the 245 size that has a contact-patch closer to 240mm .... the Zed can certainly use it.

Nathan

David as you are probably aware the contact patch is not just the width of the patch but the area, or put another way. That flat bit on the bottom.
French cars are universaly praised for being good handling cars, but where have you seen a French car with big fat tyres.
Having said that the 235 Conti you measured will have a bigger area than the 245 REO40 as they are both 18"

A good way to check contact patch area is to blue (an oily rag will do) the tread & lower the car on to some cardboard. Then raise the car & measure the contact patch that has been imprinted on the cardboard.
You will be supprised to see how small the forward to aft contact patch width is with wide low profile tyres.
This is why you get so much wheel spin on take off.

DavidM

David as you are probably aware the contact patch is not just the width of the patch but the area, or put another way. That flat bit on the bottom.

Yes, that's right ... it's a rectangular area, not just the width. So the tyre pressures have an effect on it as well. Still, I generally find if that I put a tyre with wider contact path on the the same rims, then the contact-patch increases.

ps. Peter, what size tyres were you guys running on the GTP 350Z? Also what pressures did you have it those? I'm aware that the slicks usually run much lower pressures than road tyres, but I'm still curious.

Nathan

240/680 X 18 Michelin slicks & last time out Hankook Slicks
Cold Pressure 26psi front 28psi rear, rising to 35psi hot.
Most people run too high a pressure on there road tyres, the bigger the tyre the less pressure required. Peter Brock used to recomend 25psi on his signature Brock HDT specials

Z350Lover

iTrader: (2)

So Peter, what tyre pressure do you recommand for the 350z road cars with road tyres? I am not too sure about it myself and am running larger tyres than before... 275/40/18 at the rear.. please advise.

cheers,

richie

Nathan

Correction.
Most people run too low a pressure in there tyres because they are lazy or forget to check the pressures.
But those that check there tyres all the time useually run too high.
I don't own a road registed Z but if I did I would probably run a 275 tyre about 30psi. I drive a 430 Lexus with 255/40 x 19", a car a bit heavier than the Z & I run 32.
The heavier the car the higher the pressure on the same tyre size
You can lower the pressure as the tyre gets bigger.

Formula 1 tyres from memory run 4psi or is it 7 ?
On the track with road tyres you have to raise the pressure a fair bit on 60 or 70 profile tyre as there is a fair bit of sidewall flex but as the profile comes down so does the pressure.

Think of a basketball, the more pressure the higher the bounce
Same thing with tyres.
Light car with big low profile tyres overinflated = bounce. You wont feel it, but the shocks have to work harder to control it

DavidM

I don't own a road registed Z but if I did I would probably run a 275 tyre about 30psi.

I would not run pressures that low on tyres with such a low profile (ie. 50 pr lower). Reason is pot-holes. If you hit a pot-hole while running pressures that low then the tyre will 'squich' enough for the contact to be made withthe actual wheel. This will not only (more than likely) puncture the tyre, but also bucle the weel. My father had bucled 2 wheels like that on his HSV R8, and the guy with the C32 AMG that I know already buckled one on a put-hole.

It's not too different to racing-bikes and the super-low-profile tyres ... they run close to 100psi in the tyres just so they don't cut the tyres on the rim everytime they hit a rock.

Another thing is that with pressures that low you will chew through the sides of the treads (and maybe even side-walls) so quick it's not funny ... I don't think I'd get more than 10,000km out of my tyres with pressures like that .... but it depends how hard you drive (and how manyt pot-holes you hit).

Personally I'd never run anything lower that 35psi, as the tyres/wheels would not last. I run 40psi at the front and 36psi at the back. Though, I'll probably drop the fronts to around 37 - 38psi now that I have camber there.

ps. Most manufacturer 'recomendations' (and I would pressume same goes for Brock and his cars) are aimed at 'comfort' setting and not really for hard driving. Their settings is designed to give you a good ride, do not (usualy) cater for hard driving, let alone pot-holes.

mchapman

iTrader: (1)

The max tyre pressure is 4X psi? Running 40psi is getting close to the max.

Ive seen a photo of a father and son who over filled their tractor tyre. It blew up, tore all their clothes off and killed them.

MR RIZK

iTrader: (7)

I'm in the process of either buying new rims + tyres or replacing the stock tyres for now.

My question is what do you think of running 245/40/18 front and 245/45/18 rear on the oem track wheels?

The 245/40/18 give the same rolling diameter as stock.

Any thoughts ?

Nathan

David
To each his own, but I dont beleive 30psi on a 275/40 section tyre would chew through (and maybe even the sidewalls) no matter how hard it was driven.
I have competed in 5 Targa Tasmania's in a big heavy car, always running in the top 20 & have never run the tyres above 35psi.
Despite giving the tyres an absolute pounding on the best & worst road conditions that Tasmania provides, I have never suffered a tyre or rim problem.
Can't say the same about the car or for that matter the driver.

DavidM

The max tyre pressure is 4X psi? Running 40psi is getting close to the max.

It's more like 50 to 60psi ... depending on the tyres. Some 'driver training' programs recommend that you come in with 50psi in the tyres. I've had 50psi in tyres before on the track/skid-pan and had no problems.

The HSV has been running 45psi for over 2 years, and never has it felt better ... also it's good not to be buckling the wheels anymore. The C32AMG that buckled (and wrote off) a wheel recently was running 32psi at that time .... the wheel/car was only couple of months old.

I was running 40psi in the front tyres of the S2000 for all but the first 6 months. The Zed has had 40psi at the front since I was fiddling with the pressures early on trying to find the best balance ... that is what worked for me and has been running ever since. Bust as Imentioned before, am planning to run a couple psi less in the front now that I have more camber.

To each his own, but I dont beleive 30psi on a 275/40 section tyre would chew through (and maybe even the sidewalls) no matter how hard it was driven.

I'm not disputing you exeprience at all ... I hear a lot of people recommend low'ish presusres. Though, that never works for me, and also seeing 5+ buckled wheels because of low (ie. low 30s) tyre pressures has convinced me that running presses that low on 18" wheels only buckles wheels .... there's always a pothole somewhere. I'd feel pretty safe running those pressures at the track, but not the road.

Besides that, I get way too much side-wall scrubb unless I have at least 35psi in the front. Though, in my R-spec tyres I'm running 32psi all around ... 35psi was a bit too much.

Also (I think) Apsilon's dad has a HSV and he's 'shreaded' a few tyres most likely due to running pressures in the low 30s.

DavidM

I swapped my OME wheels/tyres for my R-spec ones (ie. 245/40/18 RE55s). I measured the contact-patch on these and it is 240mm ... that is a whoping 2cm wider than the OME tyres. Will see if I can find something that wide when it comes time to replace my road-tyres.

I also had a look at my OME tyres, which now have 12,000km on them. The fronts are looking more worn on the shoulders than in the center. And that is with 40psi in them since ~4000km.

The rears are looking much more 2nd-hand, and are more worn in the center. Odd as they are running 36psi. Looks like I should try couple psi less in the back if I want the rear tyres to last anywhere close to another 12,000km.

ps. I'm running 33/31psi (front/back) in my R-spec tyres, but they can't be compare to road tyres as even with these pressures the car feels like it's had it's suspension stiffened 2x (ie. rough ride).

KY350

David - my rears are also worn in the centre and I have kept the pressures between 35-40psi. Do you corner aggresively on the streets, as I cannot imagine why your front shoulders are so worn with the pressures you are running.

My fronts have a weird wear pattern. The drivers side front shows wear on the inside shoulder block, but not very much on the outside - looks like the feathering problem that causes uneven tyre wear and the tyre noise is now very intrusive around 40 +/- 10km/h and 70 +/- 10km/hr.

The passanger side front tyre shows wear mostly at the 2 lateral shoulder block patterns, but this tyre is worn more than the drivers side front tyre?????

My alignmemt might be all out????

I'm still waiting for my new tyre order from Tempe Tyres to arrive. They have quoted me $30 for an alignment and said that they can provide me with a printout of the alignment specs (I will give them the alignmnet specs to match up to). Has anyone ever used this mob before for alignment??? Alternatively can someone in Sydney recommend a store that they trust for accurate alignmnet that can give me a printout of the alignment specs post alignmnet?

Nathan

KY350
No one can give you an accurate alignment with regards to camber & caster, as like a large majority of cars today there is no way to adjust these. Hence the $30 fee
All that can be altered is the toe setting. So your stuck with how the car was built unless you invest in some adjustable upper arms.

Nathan

The rears are looking much more 2nd-hand, and are more worn in the center. Odd as they are running 36psi. Looks like I should try couple psi less in the back if I want the rear tyres to last anywhere close to another 12,000km.

Not odd at all David.
As I said before most enthusiest drivers run too much pressure. Now my recomendation of 30psi on a 275/40 tyre is getting closer to what you are going to try on a 245 (210).

kY350 What brand did you settle on?

MR RIZK

iTrader: (7)

I have tried many wheel aligners and it is funny how much difference there is between all the machines. Just ask them when they last calibrated their equipment. They always look at you puzzled and say it was done last week.

One instance I asked this question and got that exact answer then I proceeded to point out that one of my rear tyres was visibly at least 2 deg more camber than the other. I mentioned that their unit must be out of calibration and his response was that the alignment is out because you have camber pins? WTF ? and you can imagine the rest of the story.

I personally stay away from digital aligners and only go to Heathmans on Princess Highway as their machine is still the old fashioned mechanical type. It *may* not be 100% but least it is the same every time.


My 2c any way

KY350

Hmmm - it appears that wheel alignment is definately not a science, with all the variability between systems - very frustrating!

Rizk - thanks for the response and suggestion. From your post, I take it that you prefer the older mechanical aligner as this would not need calibration.

Peter - you say that camber and castor cannot be altered. If that is the case, then why does Nissan have a serivce bulletin outlining the minimum and maximum paramaters for same? (I have it saved in my computer, but don't know how to attach images). I'm not saying that I don't believe you (I'm in no doubt that you know more about the 350 than all / most Nissan service techs), I'm just confused. Also, do you do aligmnets at your workshop?

Peter - I always thought that the lower the profile tyre, the higher the tyre pressures. Fo example, standard Falcons / Magnas with 15" wheels (and high profiles) indicate tyre pressures around 28psi. My 350 with 17" wheels and lower profile tyres indicate a pressure of 35psi as appropriate. So, I would extrapolate that info to mean that a wider 275 width and associated lower 40 profile tyre would need a higher pressure still, but you state that the pressure should be lower???? Can you elaborate any as to why?

Finally, to answer your question, I went with Goodyear F1 GS D3 tyres all around. My choices in rubber selection were limited due to no other manufaturer making an exact matching OEM size tyre except for the original Bridgestones and Goodyear.
If I went with any other manufacturer, I would have had to have gone with a lower profile (45) and wider tyres. I didn't think that would be a wise option as my wheels would be at the minimum width to accept a wider rubber, meaning more tyre buldge which I was not keen on.
The Goodyears cost a little more than the OEM Potenzas, hence my determination to get an accurate alignment done to ensure reasonable tyre life, considering that I cannot rotate the tyres.
Oh - and of course, the reports on the quality(dry grip/ wet grip / handling / noise / treadwear / price) of the GS D3's were far superior to Potenzas (and all other brands except for Michelin PS2 which are too damn expensive and not made in my wheel size anyway)- time and miles will tell if these were accurate reports.

DavidM

Not odd at all David. As I said before most enthusiest drivers run too much pressure. Now my recomendation of 30psi on a 275/40 tyre is getting closer to what you are going to try on a 245 (210).

Yep, I'm going to give 32psi in the rear a go, and take it from there. I'm a lot less worried about buckling a rear that front wheel as most of the the occurences that I mentioned happened at the front. Not all, but most as my father did shread a rear tyre (and stuffed the rim) on the HSV when he was running 36psi in the rear ... mind you, he was 'cruising' at around 200kph.

David - my rears are also worn in the centre and I have kept the pressures between 35-40psi. Do you corner aggresively on the streets, as I cannot imagine why your front shoulders are so worn with the pressures you are running.

I'd concider myself a reasonably agressive driver (in terms of cornering, not attitude ;-), but I'd say that most of the time I drive with the traffic, and hence very composed. But I'd say that I do have an 'agressive' steer every week or two ... how hard do I drive then is hard to say as it's all relative, but I'd say 8/10th on my scale.

Nathan

MR RIZK & KY350
There has never been a wheel alignment machine that does a wheel alignment.
Be it a fancy digital machine with a TV screen & printer, a Servex aligner like Heasmans use or strings & ruler like race teams use.
All this equipment does is take a measurement, it is then up to the opperater to manually make adjustments where possible & then use the equipment to recheck the measurements.

KY 350:
We use a hand held camber guage & primitive way of measuring toe ( that is 100% accurate ) It is then up to me to make the nesesary adjustments.
With regards to your tyre pressure question, I will give a long winded genralisation.
Tyre pressure recomendations are set by the manufacturer in consultation with the tyre maker & have allways had a load rating as well as a speed rating. It used to be in so many Lb's @ ?? Psi.
It is now a load index # Eg: 79T on a 165/70 13 to say 93W on a 245/40 18
Now lets take a paticular Brand & Pattern, a 245/40 18 has a load index of 93 = 650kg . A 275/40 18 has a load index of 99 = 775kg despite being of identicle construction.
The difference is the amount of area for air & therefor a larger load cap. When you see a tyre of the same size with a higher load index you can bet money that it will have a stiffer sidewall construction & therefore a stiffer ride.
This is why Davids R spec tyres ride harder

Lets look at a roadworks machine or tractor as an extreme example. Tyres higher than the machine, huge air capacity but only about 5psi & filled with water to keep them on the ground. If the tyre pressures were raised they would bounce off the road despite there huge weight. Same with Formula cars's but this time it's the low weight in relation to tyre air capacity.
David was spot on as to why the higher psi recomendations on low profile tyres. Rim Damage.
But a 275 would be no more susceptible to rim damage @ 30 than a 235 @ 35.
Well thats my theory anyhow & I'm willing to dig the pothole so you can bring your car,s over check it out if you like. Why I,ll even lend you a trolly jack & air gun to change the wrecked wheels

KY350

Now Peter, you're quite a few years older than me, so I would not want you to aggrivate your back digging a pot hole just for my sake!

Thanks for the explanation on the pressures.

WRT toe adjustments, I might just bring the car over to your workshop when the new wheels are mounted.