305/55/20 vs. 305/50/20

Sobomaster · #1 03-10-2009, 07:05 PM

Ok, so I've decided I'm definitely getting wider tires with a more aggressive tread.

At first I wanted some Cooper Zeons, but I can't find them anywhere in a 305. Then I decided I'd get some Kumhos, but I also can't find them locally in a 305. So, I'm now looking at Nittos (been working my way up the price ladder slowly). The Nitto Terra Grapplers are $316 for the 305/55/20 but only 265 in the 305/50/20.

My understanding is that the 305/55/20 size is basically the same as stock (275/60/20) and should not throw off my speedometer. If I decide to go with the 305/50/20 size, other than slightly throwing off my speedometer and having less cushioning, is there anything else that will be affected that I'm overlooking? Once I get a superchip I could always adjust the tire size.

Thoughts?

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capsfloyd · #2 03-10-2009, 07:06 PM

check tirerack.com

Doc Fluty · #3 03-10-2009, 07:24 PM

305/55/20 will be .2" taller (6mm) so your speedo will be 0.7% faster - example speedo reads 60 mph, it will actually be 60.4

also your sidewalls will be .1" taller with these tires

so yes the difference will be negligible

the 305/50/20 will be 1" shorter than stock (838 mm v 814 mm = 2.9% smaller). so when your speedo says 60 mph you will actually be going 58.3. and with this your sidewalls will be .5" smaller.. which could be a lil more tough

some things you might be over looking could be tire weight. heavier larger tires might make your brakes react slower. We have already discussed the amount the tire would stick out past the fenders and those problems (not including it is technically illegal in some states). also look at the load rating of the tires.. different load ratings could mena a softer or harder riding tire... also the wear rating for the different tires...

Eh.. sometimes ignorance is bliss... just go with the coolest tread pattern lol

Sobomaster · #4 03-10-2009, 10:38 PM

Thanks for the detailed analysis Doc Fluty.

I considered load ratings and treadwear ratings - both seem pretty good for the Nittos. I briefly thought about the braking - the 305/50/20s will be a little lighter. Also, the tires sticking out past the truck is not an issue in TX - but I remember you had to have mud flaps if that was the case in CA.

bigred3297 · #5 03-11-2009, 12:24 AM

Quote:

Originally Posted by Sobomaster

Thanks for the detailed analysis Doc Fluty.

I considered load ratings and treadwear ratings - both seem pretty good for the Nittos. I briefly thought about the braking - the 305/50/20s will be a little lighter. Also, the tires sticking out past the truck is not an issue in TX - but I remember you had to have mud flaps if that was the case in CA.

You'll be fine in Tx, no such law will affect you there. Nitto's are good tires i highly recommend them from personal experience.

Big_Fishman · #6 03-13-2009, 02:50 PM

Quote:

Originally Posted by Doc Fluty

305/55/20 will be .2" taller (6mm) so your speedo will be 0.7% faster - example speedo reads 60 mph, it will actually be 60.4

I wonder if that throws the odometer off too... Would it add miles faster or slower if the tires were a different size?

Sobomaster · #7 03-13-2009, 03:22 PM

Quote:

Originally Posted by Big_Fishman

I wonder if that throws the odometer off too... Would it add miles faster or slower if the tires were a different size?

Well, a larger tire makes the truck think you are going slower than you actually are, so it adds miles to the odometer at a slower pace.

Since I've decided to go with the 305/50/20, which are 2.9% (let's round to 3%) smaller, then the truck thinks I'm traveling faster than I am, so it will add mileage 3% quicker than in reality. For me this is not too big of a deal since it's only 3% and once superchips comes out with their programmer I can adjust the tire size anyways.

Speaking of which - if you had the programmer you could tell the truck you have much smaller tires than you really do and it would compensate for that, thereby recording mileage at a slower pace than reality (great for someone with a lease?).

Thatmarkguy · #8 03-13-2009, 06:10 PM

Quote:

Originally Posted by Sobomaster

Speaking of which - if you had the programmer you could tell the truck you have much smaller tires than you really do and it would compensate for that, thereby recording mileage at a slower pace than reality (great for someone with a lease?).

That works until you pulled over by the man for going faster than your speedo shows - Doh!

Sobomaster · #9 03-13-2009, 06:16 PM

Quote:

Originally Posted by Thatmarkguy

That works until you pulled over by the man for going faster than your speedo shows - Doh!

Yeah... you'd want to pick a size that is off by an easy amount to calculate - like 10% or 5% or 20%. Would require some thought.

I'm not much of a speeder anymore anyways. Back when I was a kid I sped all of them time. Now it's just ~10 or so over the speed limit. I also traded in my vette, so that helps.

bigpappaholt · #10 04-08-2009, 03:23 PM

http://www.miata.net/garage/tirecalc.html

check this out.