Wheel size differences resulting in changes to handling characteristics?

[180fan]

Alrighty guys, I've done a search but couldn't find conclusive info on this matter.

I've a question as to the effects to the handling characteristics of wider and larger diameter wheels. The dimension that would probably change the most is the width of the wheel but wonder about what changing the diameter would do. I see cars running 17's in the front and 18's in the rear and not exactly sure why they do that instead of keeping 17's consistant at all 4 corners.

Any help with clarification on the matter is greatly appreciated.

[chmercer]

when you run 18s, you can lower the car to almost fully cover the tire, with 17s if you try to pull that, the wheel well looks funny sized, and the car will be scraping everywhere.

people also run 18/17 stagger because they arent man enough to roll 19/18.

[eddiec]

most race cars have big wheels to clear big brakes or thats the class rules. drifters do it for the bling. i think for performance the best bet is to run the smallest diameter but moderate width you can fin find. smallest diameter is less rotational weight and helps improve gear ratio.

[chmercer]

not entirely true. a lot of good tires dont come in small diameter sizes. so you have to run at least like a 16" wheel to find tires that dont suck.

but yea in the 80s they would run bigger diameter wheels in the rear for enduro races because it was thought that it would last longer since there was "more tire". nowadays im pretty sure its just rice to run a stagger.

[SmithSR]

a lot of good tires do come in smaller sizes. AO32R, RA1, Pilot Sport Cup, Azenis Sport 215 and RT-615 are all competition tires and are all available in 16", in diameters and widths ideal for easy hassle-free fitment to the 240sx.

A tuna sandwich says chmercer uses the term "a lot of good tires" that don't come in small sizes, to point out that the AO48 does not yet come in smaller sizes. Neova? Doesn't fit the description anyway..

[180fan]

Well the setup I was planning on running is 17x9 +17 (F) and 18x9.5 +25 (R). My main concern was that with the wider width tire up front, it might make the steering feel heavier (am I thinking about it right? more width would make it harder to get it to get the tire to change direction wouldn't it?), with the tires in the rear, that it may seem to drag a bit when I'm going through a turn for the same reason as above. Am I thinking about it the right way?

The diameter for the rear was for the fact that the Work wheels I'm looking at aren't available in the 17x9.5 that I was looking for hence the bump up to 18 to get the width I was originally looking to get.

[eddiec]

a wider width tire up front will add grip to that end, which will add understeer.

[chmercer]

a lot of good tires do come in smaller sizes. AO32R, RA1, Pilot Sport Cup, Azenis Sport 215 and RT-615 are all competition tires and are all available in 16", in diameters and widths ideal for easy hassle-free fitment to the 240sx.

huh? thats what I said, you have to run at least a 16" wheel to get good tires.. maybe im misunderstanding you. hrm.

a wider wheel up front will indeed make the steering feel heavier. however i would say the effect is negligible. If you have power steering then it wont be hard to get the wheels going, and if you dont, ive heard of plenty of people running 9" wide in the front on manual, and they dont seem to complain. dunno.

eddiec - how do you figure that more grip on the front will add understeer? thats backwards.

180 - if you want the wheels, get them. the effects on handling are going to be pretty mild going from a 17 to an 18. personally i would worry more about the price increase from a 17 to an 18 inch tire more than i would the handling. also your car better have some power, because putting 18s on the drive axle of an NA ka24 car does make it noticeabley (sp?) slower.

[eddiec]

thats backwards..

yeah it was too early this morning. adding grip to the front (ie. wider contact patch) will correspondingly decrease grip in the rear which promotes the oft-enjoyed oversteer.

[180fan]

Ah good stuff. Fun time with new wheels it is...that is after I finish my rebuild lol

[Nismo_Freak]

yeah it was too early this morning. adding grip to the front (ie. wider contact patch) will correspondingly decrease grip in the rear which promotes the oft-enjoyed oversteer.

It doesn't decrease rear grip, it exceeds it.

[Nismo_Freak]

Larger diameter = more contact volume, cooler and more consistant tire temperatures, greater corner exit acceleration (in some cases), as well as the benefit of a higher load index in some instances.

[Nismo_Freak]

a wider wheel up front will indeed make the steering feel heavier. however i would say the effect is negligible. If you have power steering then it wont be hard to get the wheels going, and if you dont, ive heard of plenty of people running 9" wide in the front on manual, and they dont seem to complain. dunno.

But how many of those people are running true 9" wide tires?

Mr. Boso

[Q45tech]

"a wider width tire up front will add grip to that end, which will add understeer."

What you want on front is a higher load index [stronger tire] so that the slip angles will not be a steep. Oem front tires are always marginal in load index to create faster slip angles vs load. This is what creates the designed in understeer........the front tires wash out faster than the less loaded rear tires.

Then you fix the under/over steer ratios with sway bar adjustments to decrease the rear's natural advantage due to lower rear weight.

[chmercer]

But how many of those people are running true 9" wide tires?

Mr. Boso

whats a 9" wide tire? ill run my 265 on my 12" wide wheels kthx

[Nismo_Freak]

whats a 9" wide tire? ill run my 265 on my 12" wide wheels kthx

My 255's fit the 9" wheel with a square profile.