255/85 R16 Owners Experience

Does anyone have any experience with Cooper Discoverer S/T's (not MAXX)?? I know they can be hard to find, but I saw they were about 10 pounds lighter per tire than the ST MAXX.

 

I chose the ST for that exact reason since im in a 4cyl..Ive gotten about 30k out of 1 set and the second set about 35k. My only complaint is on ice. Siping helped some but still not impressed.

 

Debate is over. Jiust got back from king of the hammers. No one was running 255s. /thread

 

Only 30k?? That seems really low.

 

Not sure what you mean.

 

For some maybe so but I have never ran a tire over 35k even the MS2.

 

Nice rig!

He's just being a ......

 

Ok got it.

 

I may be considering those tire for my next set. Where you running them with stock gears? If so did mpg got a hit?

 

If you add 8% for the mileage difference i lost about 2mpg on stock gearing. It doesnt bother me because i know its a 4cyl and I didnt buy it for speed anyway.

 

I am not concern about speed either lol did you chek your odo with a gps with the stock tire size? Mine is +- 550m off on a 100km trip. And so rolling 110km/h is 104-105 in reality. I may be wrong but with bigger tires I think I would be pretty close to reality

 

From my understanding the 4 banger trucks seem to have inaccurate Speedos. I have a 4 cyl work truck and the Speedo is pretty far off with the stock tires.

 

Never really checked with gps. There was a tire calc on here said difference of 8.5%. I dropped the .5 because i knew the stock dunflops were on the anorexic side for tires.

 

does it seems to be right with compensating with the tire size calculator? Not really sure about this method because tire height and width is not that much the same on paper and in real life

 

Ok. 23 miles to gallon with dunlop 245 75 16.
19 miles gallon cooper st 255 85 16. no calculation adjustment. same rims oem 2nd gen steelies. 35 psi in both.

 

If you do the calculation you will find you are getting better than 19mpg. If you want to really find out what you're really getting.

 

I know that is why i posted without calculation ....because another guy said with the tire calcutaion and difference in tires it wouldnt be" real world"

 

Thanks! I am around 19 now with 265/70/16 (same height as stock but heavier) and a shell and a lot of city driving. I will still consider 255's cause it looks great lol!

 

Calculation may be good too just never tried it... imo, comparing a trip distance on the odi vs a gps would give really good statistics to compare

 

The diameter adjustment is primarily to compare to previous tires and is significant. To claim it doesn't matter in the real word is incorrect. There are many things that do affect your gas mileage like tire tread pattern and tire weight. Tire diameter will obviously affect things like weight and the moment on inertia of a tire, but it wont directly affect your gas mileage. That is why it is important to take the size difference into consideration.

So, according to tiresize.com the difference in circumference between 245/75 r16 and 255/85 r16 is 8.5%. That means that you are going 8.5% faster and further per revolution. This means that your odometer is also 8.5% behind. Which means that if you are doing MPG calcs you are 8.5% off from your real value. So lets do the math:

for 255/85r16 you calculate 19mpg from your odometer. 19+(19*.085)=20.6 Congratulations. You are still getting above 20 MPG with 255's.

This means you lost ~2.5 mpg to tread, weight, rolling resistance...etc. instead of losing 4 mpg. Of course your speedo/od may be off in the real world. But the difference is still gonna be the same-ish. (instead of 23/20.6 it would be 22/~19.6)


TL/DR: GPS is the best way to calculate your gas mileage. But adjusting for tire size is significant and should be accounted for assuming your OD is mostly correct.