Narrower tires? Wouldn't WIDER be better?

[ChrisB]

The IndyStar article (http://www.indystar.com/articles/8/101544-6878-037.htmlIndy) about the engine reduction also says: Reducing the width of the Firestone tires is being discussed.

Someone enlighten me... wouldn't wider tires make the cars more stable? The way I understand it: narrower tires = less drag = higher straightaway speeds, but with less grip = lower cornering speeds. This means there will be an even bigger differential between the straightaway speeds and what they need to slow to on the corners. Also, less mechanical grip means there will be more temptation to crank in even MORE aero.

Wider tires, on the other hand, will have more more drag and slow the cars on the straights, but give the drivers more grip in the turns. By having more mechanical grip under them, the drivers will have more confidence about what they're doing in the turns. There will also be less temptation to crank in the wing to get back what they would have lost with narrower tires.

A problem with so much reliance on aero grip is that it's so suseptable to loss (turbulence) when following another car closely behind as well as during small amounts of oversteer when the wings aren't perfectly perpendicular to the airflow. Mechanical/tire grip isn't as suseptable to fluctuations in the airstream.

A few of us have already discussed on the CART forums that it would probably be better to increase tire width/grip on those cars to facilitate passing. I found an article in RACER circa '97 when F1 was making plans to go to the grooved tires for '98. This was essentially the same thing as reducing the widths... the grooves take away from the area of the contact patch. The article has an interesting quote from Goodyear's F1 sales manager at the time Cal Lint, who said that they recommended to the FIA for "a wide, flat tire that would give you plenty of grip in the corners for passing maneuvers, but would slow you down on the straights because of the increased aerodynamic drag" (exact quote). The FIA ignored this recommendation and went with the grooved tires which nobody likes still to this day.

For discussion purposes, as best I can tell, the widths of the current IRL/CART tires are F:10" R:14.5" whereas during the F5000/F1 era in the mid/late 70's they were F:10.5" R:16.2" Wouldn't it be better to go to widths like THAT to give the drivers more mechanical grip to work with, and less reliance on aero?

[cart7]

I would think that trying to crank in more downforce into narrower tires would create quite a wear problem which would necessitate the need for more pitstops. Granted, the earl will probably solve that problem with more debris yellows. I can already hear race control already..

I know we haven't reached the fuel window yet but how are everybody's tires? Do we need a debris yellow yet?

[nissan gtp]

oddly enough, maybe wide grooved tires are the way to go on ovals...

wide=aero drag = somewhat less speed (but complicates air flow around and behind the car --- need chassis areo limits/rules too)

grooves= less grip = slower in corners

[Peter Olivola]

This "wide is stable, narrow is less stable" myth needs debunking.

Lateral stability is not a funtion of tire width. It's a function of chassis design, aerodynamics and tire performance characteristics but not including overall adhesion.

If all the above are done correctly, the only thing reducing overall adhesion accomplishes is to move the cornering speed down. It does absolutely nothing to change the fundamental cornering stability of the package.

If the tire manufacturers are okay with narrower tires that means they are confident they can produce appropriate performance characteristics. Otherwise they would be considering their alternatives. Even thought it wasn't Goodyear's fault, they suffered for several years as a result of the transition to radial tires at Indy. The entire industry is all too aware of the problem it would create if the tires became the subject of accusations about safety related issues.

What will change is the speed differential between straights and corners. That puts an increased burden on chassis dynamic behavior. Once a car is at or near maximum lateral acceleration (cornering limit) the package is actually more stable than when it's going in a stright line. The transition from straight to lateral max is where stability is an issue and that has nothing to do with the width of the tires and everything to do with the chassis, suspension geometry, springs, shocks, sway bars and aerodynamics package.

Whether wide or narrow, the tires can not be pushed past their limits. Speed is only one factor in defining those limits. A chassis that does not transition smoothly enough will create spikes in tire loading and wide tires are more suceptibe to this problem than narrower tires. So, it's actually more accurate to say that making tires wider makes the package inherently more unstable in transition.

[ChrisB]

The transition from straight to lateral max is where stability is an issue and that has nothing to do with the width of the tires

How can it not? Going to narrower tires will increases the speed differential between straights and corners. (which in turn increases the burden on dynamic chassis behavior... which in turn increases the likelihood that if they don't get the setup just right, they'll go into the wall)

A chassis that does not transition smoothly enough will create spikes in tire loading and wide tires are more suceptibe to this problem than narrower tires.

But with wider tires, the differential between straight and cornering speeds is smaller in the first place... thus reducing the chance that it won't transition smoothly and create those spikes in the first place.



the only thing reducing overall adhesion accomplishes is to move the cornering speed down.

Who says making the tires narrower will reduce overall adhesion? ...if they take away some tire grip, won't the teams try to get the cornering grip back by cranking in more wing?

[Peter Olivola]

Increasing the speed differential will require more straight line braking. The time differntial in this scenario between straight and max lateral loading with wide vs. narrower tires is less an issue than the transition stability differential between wide and narrower tires.

Narrower tires are inherently more compliant than an equivalent but wider tire. Going down in tire width won't be the same problem as going up. If the chassis is stable with wider tires it will be more stable with narrower tires as long as the team doesn't do anything stupidly radical with the set up.

Your first point is arguing for making the cars easier to drive and set up as a justification for using wider tires. You can't have it both ways. Either this is glorified Formula Fords at Dover or its a top open wheel series that requires talent from both drivers and teams. Getting set ups wrong is not about inherent stability it's about skill and hasn't that been the primary knock on the IRL sleds all along?

Reductions in downforce are also part of the package. I don't see teams junking their timing based decisions on set ups. If more downforce produces better lap times they'll use it but it opens up the possibility that a driver who can handle it will opt for less downforce and less drag. The last year where that was a deciding factor in the championship and the Indy 500 victory was 1995. You remember 1995, don't you, Chris?


Originally posted by ChrisB
The transition from straight to lateral max is where stability is an issue and that has nothing to do with the width of the tires

How can it not? Going to narrower tires will increases the speed differential between straights and corners. (which in turn increases the burden on dynamic chassis behavior... which in turn increases the likelihood that if they don't get the setup just right, they'll go into the wall)

A chassis that does not transition smoothly enough will create spikes in tire loading and wide tires are more suceptibe to this problem than narrower tires.

But with wider tires, the differential between straight and cornering speeds is smaller in the first place... thus reducing the chance that it won't transition smoothly and create those spikes in the first place.



the only thing reducing overall adhesion accomplishes is to move the cornering speed down.

Who says making the tires narrower will reduce overall adhesion? ...if they take away some tire grip, won't the teams try to get the cornering grip back by cranking in more wing?

[ChrisB]

(it's the weekend... so lets pick this up again :) )

Pete.. remember the RCCA? The club outta LI than ran older FF's? One of the things they did to help keep costs down was to spec a very hard tire... so that each participant could probably get a whole season out of just one set.

Now consider that tire grip can come from either the patch size and/or the compound. Concievably a narrower tire with a soft compound could have the same grip as a wider tire with a hard compound. (in fact the current F1 tires are slightly narrower than Champ/Indy tires, but have more grip because they're softer)

How about going to the widest tire possible and then matching it with an appropriate hard compound.... this way we'd get about the same grip as now, but less marbles and longer wear, and the extra width would still be good for creating some aero drag to keep speeds in check on the straights.

[Peter Olivola]

That kind of hard compound works on underpowered cars (two types of race cars, underpowered and overpowered.) The tire manufacturers don't seem to think it's viable for overpowered cars. It would be very difficult to force them to produce a tire they don't want to produce. Beyond that, the combination of sidewall characteristics, inflation pressures and compound characteristics are part of the tunable suspension. Cars are designed to the tires. That kind of radical change would necessitate a lot of redesign and/or testing and set up changes.

One other characteristic tire difference between CART and Formula Ford. The FF tire is a cantilevered design developed to optimise performance when used with narrow rims. That's not possible with the section ratios of significantly wider tires.


Originally posted by ChrisB
(it's the weekend... so lets pick this up again :) )

Pete.. remember the RCCA? The club outta LI than ran older FF's? One of the things they did to help keep costs down was to spec a very hard tire... so that each participant could probably get a whole season out of just one set.

Now consider that tire grip can come from either the patch size and/or the compound. Concievably a narrower tire with a soft compound could have the same grip as a wider tire with a hard compound. (in fact the current F1 tires are slightly narrower than Champ/Indy tires, but have more grip because they're softer)

How about going to the widest tire possible and then matching it with an appropriate hard compound.... this way we'd get about the same grip as now, but less marbles and longer wear, and the extra width would still be good for creating some aero drag to keep speeds in check on the straights.