Tire Load Ratings in Relation to Overall Grip and Width

[Nismo_Freak]

An often debated topic. I'd like to hear everyones perspective on the following:

Which setup would yeild better DRY TRACK performance. Adverse conditions are not a possibility... we are assuming 76 deg. ambients with a track surface temp of 83 degs.

Take my car as the testing vehicle.

Static Weight - 2580 lbs.

If there is any other info you need on the setup then feel free to ask.

Two Choices:

235/45/17 94Y255/40/17 94Y

vs.

255/40/17 94Y275/40/17 98Y

Ceteris Paribus, but tire pressure can be modulated.

Those tires, in terms of forward, lateral, and negative acceleration performance.

Which would be the superior setup, and why.

I have my opinions but I would like to hear others.

[Q45tech]

Hard to be specific with just tire sizes. The higher the load index [from reputable brand] in the same brand model design tire, the lower the slip angle for the same applied load.

Usually a 10% higher load index will allow 5% [or better] improvement [decrease] in slip angle.

Tires are lab speced at applied load vs. slip angles generated.

I would suggest you study Pacejka and his equations.

The strongest tire [load index] should ALWAYS be on the heaviest end contrary to what oem does [to create understeer and frontal washout to protect passenger cars with untrained drivers]. The front tires [on FWD and RWD] limit the achievable G forces possible.........only exception is rear engined cars.

http://www.racer.nl/reference/pacejka.h ... hi...c.pdf

[Nismo_Freak]

Very interesting... I am a little behind in my physics (I'm a chemical engineering student), but I can hack it with a refresher.

There are a ton of aspects I have very little knowledge about and it's annoying me, I must learn it all! The more knowledge I have, the better I can make my car perform with my budget.

[IvoryJ30t]

lets take a front engine rwd car with a curb weight of 3500 lbs.

with 255/50-17 101W [treadwear 340] tires at all four corners, would the increase in cornering capacity outweigh the increased rolling resistance?

how radically would the cars handling characteristics change if the original tires were 215/60-15 93H?

[Nismo_Freak]

I typed out a long post but hit delete like an idiot... don't care to type it out again.

DOH!

[Q45tech]

Impossible to compare apples to orages: a H rated tire and a W rated tire.Impossible to compare 44psi and 51 psi tires.

What one can say IF both tires were the same speed rating and same brand and same sidewall and tread construction:

The roughly > 27% larger load capacity [at max inflation on the same tire brand and construction] would decrease the slip angle at the exact same load by a few degrees. 1.5-2.0 degrees

To be exacting we would need graphs from testing each tire at the exact inflation pressure you propose: Slip Angle vs. Lateral Load

http://www.insideracingtechnol...2.htm

[IvoryJ30t]

very nice explanation with the link.

im still learning when it comes to suspension modification.

electronics/computers and engines take up all my time.