Ture aspect raito question

[Roadracer350]

Quick question. I ran up on some 305/660-18 Pirelli slicks. What would the height be? 40,35,30? I can't find a formula to convert. Priced good I'm just not sure if these will work right with 3:90-4:10 gears for the short track here in Oklahoma.

 

[DTL]

Pirelli measures overall height, not aspect. That's a 26" tall tire.

 

[Roadracer350]

So that's going to be more like a 35 then?

 

[SoundGuyDave]

660 is the overall height in mm, so using 25.4 as the conversion, that gives us nearly dead-on 26" height. Less the 18" of rim, leaves us with 8" of tire, or 4" of sidewall. 305mm is 12", so 4" is 33.3%, thus an effective aspect ratio of 33... Closer to 35 than 30, but not really either, really.

 

[Roadracer350]

Thanks guys. I think I may pass in them. With the short point n shoot track here and using 3:90-4:10 rear gears I'm thinking these may be a tad to short on the sidewall height. Or an I wrong?

 

[steveespo]

I have Pirelli 685 tall and 660 tall slicks. 685's are stock tire height I use them at high speed tracks with long straights(Pocono, Watkins Glen, VIR)
and use the 660's at Lime Rock, Summit Shenandoah, NJMP to shorten my gearing. About at 2 mph difference or 200 rpm across the gear range. Oh, I run 3.55 gears so the 660's make the car act like I'm running 3.73, seems perfect to me.
Steve

 

[neema]

I wish all tires used that standard of measure