Thought Experiment, Hypothetical Tire Rule

So let's say you are a factory racing team wanting to participate in, let's say, touring car racing. You are obviously all about going as fast as possible, but the evil rule makers throw this at you:

Rule 1: No body part may be lower than the bottom of the wheel.

Rule 2: All tires must have an aspect ratio of 60 or above.

Rule 3: Tire width is free.

Basically, you can have your car .5 inches off the ground and get the awesome aero that entails, but you would need to run a tire the width of a space saver spare or you can run 355 steam rollers on a monster truck. What do you do?

Cheat. That's how pro racing works, right?

More specifically, pull a Ferrari- remember the rear F1 wings that would bend down at high speed reducing drag? I'd do that with ride height. High downforce at higher speed to push a softly sprung car down closer to the ground. Sure it might scrape a lot, but who cares?

This is bench racing. It doesn't have to make sense!

Big tires, lot of aero work on the underbody to mitigate drag.

Rufledt wrote: Cheat. That's how pro racing works, right? More specifically, pull a Ferrari- remember the rear F1 wings that would bend down at high speed reducing drag? I'd do that with ride height. High downforce at higher speed to push a softly sprung car down closer to the ground. Sure it might scrape a lot, but who cares? This is bench racing. It doesn't have to make sense!

That would get you into all sorts of very interesting and practical engineering problems. An OEM would need to figure out how to get high down force from a high ride height without murdering drag. This seems useful for regular cars that need to be stable and efficient on the highway but also speed bump safe. You'd also have to figure out how to get the car to handle well on a soft suspension, which is something every single OEM wants to do on every single model.

BrokenYugo wrote: Big tires, lot of aero work on the underbody to mitigate drag.

That sounds like a very interesting and distinctive race car.

In reply to DaewooOfDeath:

I never said it makes sense, just that's what I'd do. That and invest in a bunch of skid plates for all the scraping it's going to do, and start a judge-bribing fund.

Rufledt wrote: In reply to DaewooOfDeath: I never said it makes sense, just that's what I'd do. That and invest in a bunch of skid plates for all the scraping it's going to do, and start a judge-bribing fund.

I think it's a great idea. I think it would result in a very interesting race car with practical applications to regular street cars, particularly the bribery.

Do you think that was VW's mistake? They got the cheating down pretty well on the engineering side, but they left out the bribery! Maybe next time...

DaewooOfDeath wrote:

BrokenYugo wrote: Big tires, lot of aero work on the underbody to mitigate drag.

That sounds like a very interesting and distinctive race car.

It was...

DaewooOfDeath wrote:

Rufledt wrote: Cheat. That's how pro racing works, right? More specifically, pull a Ferrari- remember the rear F1 wings that would bend down at high speed reducing drag? I'd do that with ride height. High downforce at higher speed to push a softly sprung car down closer to the ground. Sure it might scrape a lot, but who cares? This is bench racing. It doesn't have to make sense!

That would get you into all sorts of very interesting and practical engineering problems. An OEM would need to figure out how to get high down force from a high ride height without murdering drag. This seems useful for regular cars that need to be stable and efficient on the highway but also speed bump safe. You'd also have to figure out how to get the car to handle well on a soft suspension, which is something every single OEM wants to do on every single model.

Re-invent the current paradigm of suspension geometry to get to roll centers up to the CG height, so you can get more conering G out of less tire and lower the CG as much as possible. Use a 205/60 on big high-speed tracks to get the bodywork low enough for aero to be effective on long straights and big sweepers (you've got aero to increase traction, remember) and 245/60 on short, tight tracks for maximum grip on slow to medium speed corners.

Rufledt wrote: Cheat. That's how pro racing works, right? More specifically, pull a Ferrari- remember the rear F1 wings that would bend down at high speed reducing drag? I'd do that with ride height. High downforce at higher speed to push a softly sprung car down closer to the ground. Sure it might scrape a lot, but who cares? This is bench racing. It doesn't have to make sense!

NASCAR does that. Really soft springs so the car gets sucked down onto its bumpstops and gigundous sway bars.

WildScotsRacing wrote: Re-invent the current paradigm of suspension geometry to get to roll centers up to the CG height, so you can get more conering G out of less tire and lower the CG as much as possible.

That would result in an incredibly unstable vehicle near the limits, since small changes roll center movement would translate to dramatic changes in the roll couple. And if the roll couple changed signs, you find yourself in a '61 Corvair.

Two strategies. First, and it will be fun until it's banned, would be to run more than one tire per wheel.

Second, and probably more to the sprit of this exercise, would be to steal from be BMW i3.

To get "BMW handling" out of skinny tires, they added diameter, enlarging the contact patch fore and aft. That's why the summer tires on the front of an i3 are 155/60 R20.

Guide: BMW i3 Wheels and Tires – All you need to know

Not exactly what I had in mind, but, yeah, that'll do it.

Rufledt wrote: Cheat. That's how pro racing works, right? More specifically, pull a Ferrari- remember the rear F1 wings that would bend down at high speed reducing drag? I'd do that with ride height. High downforce at higher speed to push a softly sprung car down closer to the ground. Sure it might scrape a lot, but who cares? This is bench racing. It doesn't have to make sense!

Sounds like a job for dual-rate springs! The softer set fully compresses with downforce, then the harder set are the ones you actually want to drive on.

I have a car in a simulator that has a ton of downforce and very hard springs, but the downforce still eats up most of the suspension travel, and it sometimes hits the bump stops. It still handles well though. You could even choose bump stops that are decent to drive on at the limit, that's how a lot of modern cars work.

My "frame" would look a lot like an undertray!

Easy answer is build custom wheels that have plastic edges that wrap around the tire only showing the bottom inch of rubber. Then your aero can go as low at you want.

Stampie wrote: Easy answer is build custom wheels that have plastic edges that wrap around the tire only showing the bottom inch of rubber. Then your aero can go as low at you want.

The the rule gets changed to something like no part of the bodywork may touch the ground if a tire is deflated...

As long as I win that first race I'm good.

Found the double tire wheels. Popular Science 1984.

http://www.popsci.com/archive-viewer?id=lgAAAAAAMBAJ&pg=100

Update:

Stampie wrote: Easy answer is build custom wheels that have plastic edges that wrap around the tire only showing the bottom inch of rubber. Then your aero can go as low at you want.

That's what I said, cheat.

What about Tweels? Since they can adapt to terrain, would they count as body panels? I don't know about speed or efficiency with them, but a variable size wheel/tire could maybe help with the control aspect. They also look to minimize the sidewall almost completely, so you could ride with much lower body.

EDIT: i guess they don't meet the aspect ratio clause. I fail again.

In replay to stampy about the custom wheels only showing a little rubber, what about white wall rims?

Rufledt wrote:

Stampie wrote: Easy answer is build custom wheels that have plastic edges that wrap around the tire only showing the bottom inch of rubber. Then your aero can go as low at you want.

That's what I said, cheat.

It's not cheating, its interpretation of rules.

Build 2-piece wheels that work like a centrifugal clutch of sorts. Static and at low-speed, they would be narrow - so you'd have a wide tire pinched onto the narrow rim. Then at speed the halves of each wheel would spread apart, allowing the full contact patch of the tire to meet the pavement, while also lowering the ride height.

petegossett wrote: Build 2-piece wheels that work like a centrifugal clutch of sorts. Static and at low-speed, they would be narrow - so you'd have a wide tire pinched onto the narrow rim. Then at speed the halves of each wheel would spread apart, allowing the full contact patch of the tire to meet the pavement, while also lowering the ride height.

I'm not sure of the required engineering to make an air tight seal, but this is freaking genius!!!