jmac wrote:
l18-b110 - I keep squeezing the other things in because it is important. Hell I didn't even mention that the wider the tyre the less camber it tends to 'like' - which can be indicative of things.

jmac wrote:

Of course f1 (or anyone else) is running the widest tyres they can (or what they must run) - you're mis-interpreting what I'm getting at. The reason to run wider tyres is not because they grip better 'per se' - if that's the case I welcome you to get some bob jane australian all rounder tread put on some 265 width tyres, and I'll bring some toyo ra1s around to compare. What I am saying is the _reason_ for the widest tyre possible in a racing situation is to give the opportunity to run the stickiest compound possible, but still get enough tyre life to finish enouh laps between pitstops (or the sprint race distance or whatever). It's not just the width.

jmac wrote:

If you wouldn't mind (and I ask this sincerely, not as a smartalec) - do you happen to have pyrometer readings for the tread - possibly - outer and inner edges and centre region - for the tyres you ran that had the big difference before and after. It'd be interesting to see the spread of temp - both from before and after different tyres, but also to know what temps they ran across the width of the tread, it might be enlightening (to me, if no-one else)


What I was trying to get at, and I'll re-state it (and I know you've said that you would go along with this, and as such we are both sort of talking about two slightly different but related tangents) tread compound is the big deal. It's (relatively) hard to overheat tyres on the street, in most parts of this country, and I can't speak for elsewhere, you'd probably end up getting arrested if you drove hard enough and long enough to overwhelm the tyres. Brake pads - well it'd be relatively hard to overcook a1rms with a bit of touring on twisty roads, but certainly possible on a circuit.

jmac wrote:
I'm DEFINITELY not advocating running 155 width tyres or anything. I hope I haven't come across like that. Perhaps I'll restate it better thusly - width isn't 'all that' I'm not saying run bicycle tyres, but find the specific brands in the wider sizes that have a good track record, it will make or break the deal. There's (unfortunately) seemingly no shortage of tyres available that are 'big' that are also very mediocre as far as grip is concerned.

the same thing applies to brake pads. 'larger' pads, which wrap further around the disc, don't stop better, unless you are reaching the temp limits of the smaller pads. (*if the pad material is the same). The same is true of brake shoe width. IF you are getting them quite hot, then sure, wider is better, but for single stops (or a handful of multiple stops) it won't change things. NOW bigger diameter discs, same pads, definitely improve things, because then they get more leverage.

and one more thing - that's a wicked machine mate.

D wrote:
I want a better picture of this V8Z any chance we can have a few more uploaded to perv on?

Rallytwit wrote:
At the risk of over simplification: fit the widest stickiest tires you can for pure grip. The too much power for a light car kinda doesn't really hold water for me.................Brabham BT45 (I think) F1 car, 1200lbs and 1200 horsepower in qualifying trim didn't have this issue becuase it features massive slicks that were up to temp, a street car is not going to have heat in the tires at a level you get at the track...................which brings me to why I don't get the whole street racing thing. Dirty tarmac cold tires etc.................what's the point.

Now you can optimize the suspension and run the best tire possible. There are all sorts of things you can do with damper setting and suspension geometry and tire pressures etc to get more out of a car etc. The notion that a light car can have to much power is silly..........................focus on getting the power to the ground, if you don't want to run the best set up for this, then yes wheel spin is going to be a by product.

Tom

unfamilia wrote:
And none of them really effective in our country for speeds below 110kmh- not really practical here- but neither is an awd system either

jmac wrote:

On wet surfaces - I'll have to beg to differ. wider is _not_ always better. The problem is that the wider the tyre, the greater the volume of water it has to shift out of the way, and the further it has to shift it, so the tyre can grip. So once you go beyond a certain width (and it's a lot narrower than what would be 'useful' on a dry tyre overall) the tyre will actually be MORE likely to aquaplane.

You also have to look at the unsprung weight. That can (admittedly) be an advantage in some places, not always, but it's possible. It also depends on how much of an excess of power there is. I remember a website did a very tongue in cheek 'before and after' writeup where they kept modifying things on a car, a stock low-performance import of some description, and ran it down the 1/4mile. One of the first things they did was to remove the big diameter bling wheels and tyres and re-fit the stockers, and despite the stockers being less grippy, the motor just wasn't that powerful (it was running 18 seconds or so iirc) and they improved the time by a few tenths just with the stock wheels/tyres.

Back on the original topic though - when I mentioned suspension setup being vital, it is possible to get a good combination that is reasonable off the line and also through corners. And it _is_ possible (if the suspension geometry/particulars happen to cross over a certain point) to actually be too low for cornering to be optimal.

Last but not least - you could also look at (relatively simple) stuff like having different boost/timing curves that are switchable based on what gear you are in. In some drag racing, they have different timing curves for each gear, not so much as traction control (which is the way I'm suggesting it for helping traction) but rather the fact that the engine is cooler off the line, so more timing is safe/desirable, but toward the end of the 1/4mile with heat soak, chamber and piston surface temps are higher and less timing is both more optimal for power, but also necessary to avoid engine damage.

tappet wrote:
CA18 powered datto picking the wheels up in a huge way on a 205 radial and H patteren and still running a 10.4

choppedsprings wrote:
or you could just buy a factory 4wd sunny.otherwise known as nissan GTiR

jmac wrote:

believe it or not, tread width isn't the big deal here. It's friction co-efficient of the tyre tread compound (apart from chassis/suspension tweaks to maximise downforce/grip)

Here's the deal - IF (and it's a big if) the tread compound is identical - then a 235 will provide exactly the same grip as a 195 width tyre. The reason is simple enough. Grip is a result of teh combination of 2 things - downforce and friction co-efficient. If you have the same tread compound, but halve the width, then there is double the 'load' on each square cm of tread, so it basically has the same grip.

Obviously you can get to a thin enough tyre where it'll just overheat too quickly. And it'll also wear out quicker (since at half the width, it'll have half as much tread area to wear down). Since thinner tyres will experience that, very generally, the tyre makers run harder compounds in thinner tyres, and can 'get away with' softer compounds on wider tyres and still have acceptable tyre life.

So in general, wider tyres 'might' grip more, but it's only because they were made with softer grippier tread, not just due ot the width all by itself.

The reason I mention this is pretty simple - it is probably now obvious - it's not so much a matter of finding 'a' tyre in 225 or 195 or whatever the widest width is, the REAL trick is to look at each individual tyre in the sizes that will fit, and find the ones with the stickiest tread compound.

Now, even people who compete in short sprint races can overcook their tyres, so you have to try and find a balance between tyre life, the traction you need, and how long they will be good for 'thrashing' around before they start to go off a little due to overheating. As a good example - this is why the smaller cars (relatively speaking) tend to do so well compared to the big ones in Improved Production - the tyre sizes are too narrow (relatively) for the bigger cars and they overheat after a couple of laps, so the drivers have to nurse them a lot more. They can't 'really' use grippier compounds, because the tyres/compound are a regulated item.

But on a streeter, you can find a happy medium (if you are willing to go through tyres perhaps every 5-10,000km)

jmac wrote:


so as bad as it sounds, often the loss of traction is just as much to do with a car being 'too low' and ending up with undesirable suspension geometry as a result.

steve1991 wrote:
Just mini tub it!!!!