OK forum friends, following our shared interest in high performance tires, I would like to know if anyone can quantitatively demonstrate that smaller sidewalls are preferable for high performance driving. The limited research that I have seen shows no performance improvements at all. Not in cornering, not in acceleration, not in braking!

I have observed crazy Mexicanos that sport 21" wheels and micro tire sidewalls, but I have also observed that many Mexicanos like to have suspensions that bounce their cars into the air! Visual preferences aside. Clearly their focus is not performance.

The only "race car" that I observe wearing small sidewall tires is the C5-R. Now, it is a solid performer, don't get me wrong. But what I am really interested in is F-1/NASCAR/Sprint Car et. al. tire selection and performance. THEY ALL RUN THICK SIDEWALLS. What is going on????

Are the giant wheels that everyone seems to desire nothing more than for good looks? Desired simply because everyone else wants the same? Your 29" HRE's may look good, but looks are in the eye of the beholder, such as the 7" mufflers that many rice burners sport. I think they are amusing to view. Yea, I said it friends and countryman, a Joke!

My challenge is for you to justify, with real data not just subjective commentary, the performance attributes of the big wheel/small tire sidewall combo. The gaunlet has been thrown down. Respond in force, if you can!



[Modified by LTD, 1:14 AM 1/25/2002]

 

We talk about rims and wheels on normal cars and we talk about increasing rim diameter by keeping the same outer diameter, and we talk about driving on winding roads across the country, right?
I am in the durability testing business and the fact is: The combo rim/tire get´s much more stiffer, when rim diameter is increased, sidewall of tire decreased. The resullt is a stiffer handling of the car, a harder ride, but also a much bigger force on the car body components in the area of the axle/dampers. So we always do durability testing with the biggest rim that will be offered to the customer.

Or take it this way: the area of the wheel/suspension is a combination of many springs. The sidewall of the tire is one of these "springs". And it´s easy to imagine, that a big sidewall has different spring characteristic than a small one. And this effects cornering.

Frederik

 

Interesting commentary, but I am still confused. How can I claim that I have a "high performance setup" when it is so different from everything that I see running around the track?

 

Here's the short version:

The goal of the tire is to provide good grip and predictable handling. You cannot compare a production-based race car to the purpose built, all-out race cars of F1, Nascar, Sprint Cars.

In our case, our goal is lateral traction. The shorter the sidewall, the less it can laterally flex. As the tire flexes, the angle of the contact patch increases, decreasing traction. The ideal sidewall is non-flexing, always keeping the tire's contact patch parallel with the axle axis. We also want predictable handling. That same lateral flex provides a variable spring rate to our car's lateral movement, resulting in inconsistent feel to the driver, and uneven weight transfer.

Look at production-based race cars, in ANY form of road racing, they all run low-profile rubber, for the reasons I stated.

For some good info, check out http://www.grmotorsports.com

Sam

 

This, along with the rest of his statement, I agree with 100% :cheers:

 

Good Question. There are a few things to keep in mind. First is that most street cars corner better with higher spring rates than the factory provides. As already stated, a shorter sidewall effectively raises "Suspension system" (springs, busings, Sway bar, rim and tire) rate. When you say that NASCAR does not run low profile sidewall tires, keep in mind that the tire size as well as rim size are mandated by the rule book, and not by what works best. Sprint cars need a side wall that will give especially in the dirt or the ruts would upset the car too much. If you look at virtually any of the Road Racing full bodied cars (SCCA, IMSA, American Lemans...) you will se very short sidewall tires. A good reason for this is that they have less possible sidwall flex, which aids in keeping more of the tread in contact with the pavement. Great handling is greatly influenced by tire contact patch. It is not the whole equation but it is a key part.

Plus, who really cares, Low profile tires on 18", 19" and 20" rims look awesome on C5s. (Of course, the last part is just my opinion) [IMG][/IMG]