Ok - with regard to dirt on the road - well definitely that throws out the usual equations. They only apply in dry contact with clean (or predominantly clean) surfaces.

This dirt road stuff (or dusty road even) is actually very important. not so much for a performance car launching hard, but in general. Early ABS systems are close to life threatening on dirt roads. The problem there is that to improve traction on loose surfaces, you actually want blocky or chunky tyres that cause a 'buildup' of gravel in front of the tyres (for braking) or behind them for acceleration.

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.

Have you ever watched formula one when it rains to the point the cars aquaplane? They are basically just 'floating' in whatever direction inertia leads them, and worse still, as they slow down, there's less and less aero downforce, and then they are totally adrift (no bull) I can't remember which year it was, I think it _might_ have been the year Raikkonnen won the championship, or possibly the year after, and there was a huge downpour during one race, wiping out a good portion of the front end of the field as they all floated helplessly into one another, or the barriers/sand traps etc.

But back to real cars which are heavy enough to push the water out of the tread at reasonable speeds. What you need is two things - very generously sized gaps between each tread block, and the 'horizontal' gaps angled forward so they help push the water out, and lastly, the edges of each tread block need to be as 'sharp' at 90 degree angles as possible, so it can cut and push the water. curves/rounded edges will encourage it to aqua plane. Additionally, you want the tyre pressures higher for wet roads than for dry (even though most will think it is the other way around, trust me, it is well proven that higher pressures make the tread blocks more rigid and help them to push the water out.

On dry ground, you tend to want larger blocks of tread, less grooves, to make the tread more stable and consistent, to enable downforce from the car/suspension to actually maximise mechanical 'grip' at the tyre tread to road surface contact point. Whilst you want 'wider' 'longer' blocks of tread, you actually want LESS tread depth, as that leads to less deformation (the bad sort, not the good, gripping perfectly to the undulations sort). To this end, in racing classes that specify a treaded tyre, especially a specific brand of tyre, the racers all get the tread buffed down to minimal levels. They grip a _lot_ better like that in the dry (and are much worse in the wet) - and that's understandably the reason you'll find that any class of racing that demands a control tyre also regulates minimum tread depth (usually they specify it either has to have at least xmm of tread depth either at the start of the race meeting, or after the last race.


what I'm trying to get at with regard to tread compound being better than width (within sane limits) is that it really is the main thing. Yes, larger wider tyres often have a tread compound that is softer - a good thing for performance to be sure. BUT THE BIG DEAL is that even AMONST THE WIDER TYRES there's still a HUGE variation from tyre brand/specific model to one another. Basically I'm suggesting that finding 'the right' tyre is going to be the go, not specifically the precise size of the tyre.


L18_b110 - without more info it'd be hard to explain why the wider tyre (if they were truly the same compound exactly) were light years ahead of one just a little bit narrower, but I could make some guesses (and that's all they'd be without seeing it in person, and knowing more about the setup). It could be something as simple as shock setting being more suited to one size than the other (as they would transfer weight/alter contact patch differently for different sized tyres) You could even look at difference in track width from the wider tyres, and whether weight transfer during cornering or accleration (or whatever) differed with wider tyres. I'd also wonder as to the relative difference coming from the fact they were newer (even if the same compound when manufactured). Tyres don't stay the same with the passage of time, and even if they are very well stored, each race use will affect them.

I understand what you are saying about ipra control tyres being softer in smaller compounds (I didn't actually know that) but if anything, that makes it worse, because the bigger cars can't (afaict) stop their tyres going off anyway due to overheating (which does mean that width and overall thermal mass is important, but is getting off tangent a little). I just don't think that width is the be all end all on the street. The sort of tyres that people would 'love' on the street, wouldn't last more than a lap or two on the track, it's horses for courses. you could make the same argument about brake pads. a1rm pads have an almost cult following for a good all round high temperature range pad for the street or limited sprints (or maybe hillclimbs, for an all rounder, not a purpose built competition machine)

I'd go further about tread compound being vital - and put forward a few categories where there are soft and hard treads, and at least one set of each must be run during the race. The cars aren't always faster on the softer treads, long term. They overheat and go off, on some tracks (and I realise hard and soft are relative terms and the actual two compounds vary from race to race/track to track) whereas on others the soft compounds are 'ideal' and produce best and most consistent lap times, and they just can't get enough heat into the harder compounds.

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.

i have to agree wider tyres in the wet are not as good

Heres a good link describing how some of the following components can increase downforce and help "increase" front tyres grip while others can assist with aerodynamics.

Front Wing
Carnards
Front Splitter/Air Dam
Rear Diffuser
Chassis/Under Body
Side Skirts
Vortex Generators
Rear Wing
Spoilers
DRS/ Drag Reduction System

http://www.rapid-racer.com/aerodynamic-upgrades.php

one of the issues will be custom making these parts as they are not off the shelf items.I.e the underbody.But items like rear spoilers are widely available.

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

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

its obvious that different types, brands and models of tyres offer different amounts of grip. No one's arguing that. But as per my example of the exact same tyre, you get the more grip from the wider widths. Thats removing all those variable you keep trying to squeeze in.

I'm not saying he shouldn't try to choose the tyre that offers the best trade off between grip and life for his purpose, just that he should also use the widest one he can fit because that will offfer better grip. If your argument was true, we could all save alot of money and buy the narrowest of the good tyres as it offers exactly the same amount of grip as the wider ones. Its nonsense.

you're so bogged down in theory you're confusing yourself.

Ever noticed how F1 cars don't use skinny tyres? they would if they produced the same grip, because they'd be lighter and offer less drag, bother of which would dramticaly increase performance. But the fact is they can't get the same grip from a narrow tyre.

Ever notice how top fuel and other big bhp drag cars don't use skinny rear tyres? They would if they could get the same grip beacue narrower tyres would also give less aero drag, making them faster in the top end. And because wheels and tyres are flywheels - you waste energy turning heavier ones. But they don't because they need the big tyres to get the grip they need.

Which is one of the reasons why your example of the low powered car went faster with the stockies rather than the large diametre tyres. smaller, presumably lighter stock wheels and tyres waster less energy that can then be used to accellerate the car. They'd also have less rolling resistance, And also lower the gearing, meaning better accelleration. And yet another being because it simply didn't need the extra grip of the bigger tyres.

And on the same basis the cars and examples given of f1 and top fuelers are at the other extreme of the power scale where they want maximum grip for their intended purpose. 300hp shouldn't need to go to these extremes but in a light car with more power than originally designed for traction will be an issue no mater what

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

Quote:

I think you took that statement to a bit extreme. Im not saying at all that bigger is always better and yes you are correct eventually too big of a tire will slow down your ride IF AND ONLY IF you didnt need them to begin with. whats the point of slapping on a 275 if you car has full traction at 225. but if your cars only get traction with 275 then it would be optimal to run it.


and in regards to wet surface. I dont know squat about f1 cars or what not but its not something I want to use for comparison since its way to much power and way to wide tires.

im basically saying on your average tire I would rather have 255 tires on the rain vs 215 or 195. were talking streets.

this is what im talking about and dont forget were still talking datsun 1200 here so I dont see anyone putting 275 all around on this thing.

I have to say the wider the tyre is not always right no matter the compound if it doesnt suit the right
application. Ive experienced better handling on narrower tyres than wider on certain suspension setups and then wider tyres suiting others.
It all depends on the conditions and if there is dust or dirt into the equation then he might even need rallye tyres!
Formula one and drag cars are nothing like dirty roads or
a dirty backstreet drivers doing illegal drag racing!
Should we really be helping this? is the real matter!!!!

There are too many variables and a bit of research helps.
Its good if you can find your best combo or tyre and suspension
and when you do, it might just not suit somebody else`s driving style or feel.
As long as its what you prefer nothing else matters.