Hello everyone,New to the forum. I wanted to upgrade to my tires to 245/40-19 on my J30. Would the front wheels rub? Needed some help. Thanks.

The J30 uses 215-65-15 stock iirc...

in which case, the 245-40-19 OD is 26.7in vs 26.0 in.. Basically the speedo will be just slightly off (hardly noticeable) but they wont rub..... youll be good to go!

THats a good tire size to run.....

Thanks!

be sure to post some pics when you have the wheels and tires on!

I just picked up some wheels, and they have the following tire size on them:

Nitto 555's: 225/35/20

I was just wondering if my speedometer is off? Seems to be close, I can't notice a difference - but figured you could do the math.

Thanks.

Killer Croc wrote: I wanted to upgrade to my tires to 245/40-19 on my J30. Would the front wheels rub?

It all depend on the offset of the wheel you are going to you, less on the size of the tire.

1993TanJ30 wrote:I was just wondering if my speedometer is off? Seems to be close, I can't notice a difference - but figured you could do the math.

you can find out what you want from there http://www.miata.net/garage/tirecalc.htmlBTW would anyone want to see how the Murano 18x7.5 wheel w/225/40/18 tire look on a J? I'll do a swap before i put a for sell sign on my Max.

NismoChi wrote:you can find out what you want from there http://www.miata.net/garage/tirecalc.html

Welcome to NICO!

One thing my nitpicky self will tell you is that those speedometer error calculators are approximations. Depending on the tire brand and model, the sidewall flex, the amount of tread, section width, etc., there are differences in rolling diameter that actually have quite a bit of effect on the actual result - even if the tire size is "identical"!

Instead of using such simplistic tire calculators, it is better to get the actual manufacturers "revolutions/mile" info for the specific tire (available at Tire Rack) and do a way more superior job of calculating the speedo reading. Yes, the effect is surprisingly "large" - compared to the delta in speedometer reading that is!

Z

szhosain wrote:Welcome to NICO!

One thing my nitpicky self will tell you is that those speedometer error calculators are approximations. Depending on the tire brand and model, the sidewall flex, the amount of tread, section width, etc., there are differences in rolling diameter that actually have quite a bit of effect on the actual result - even if the tire size is "identical"!

Instead of using such simplistic tire calculators, it is better to get the actual manufacturers "revolutions/mile" info for the specific tire (available at Tire Rack) and do a way more superior job of calculating the speedo reading. Yes, the effect is surprisingly "large" - compared to the delta in speedometer reading that is!

Z

I agree, but do you think the differrence is really that significant?

elwesso wrote:I agree, but do you think the differrence is really that significant?

Depends on you! I did say I was nitpicky!

The point is that you can usually mostly ignore these minor speedo errors, but if you are thinking about them enough to go use a calculator, then do the job right! If you are going to rely on the results, that is!

For example, let's look at the following set of 245/45-18 tires (for use on a G35, for example.) The stock tire size is different, so all of these are off very slightly. Not by a lot, but slightly.

If you went by the calculators, they would all be off the same amount. Real-world results, using the revs/mile, (which takes all the tire issues into account) shows otherwise ... I wish I could use tables in these posts!.

Sometimes, even the same exact model of tire has differences depending on which load index you get! for example, the XL extra-load versions have stiffer sidewalls and, thus, lower revs/mile and higher speedo error (albeit less than the difference between brands/models!)

Tire Diameter Revs/mile ErrorPercent ActualAt60mph ActualAt80mphAvon Tech M550 A/S 26.7 778 -2.1% 61.3 81.7BF Goodrich g-Force T/A KDW-2 26.8 777 -2.3% 61.4 81.9Bridgestone Potenza RE050 26.6 783 -1.5% 60.9 81.2Bridgestone Potenza RE050A 26.7 780 -1.9% 61.2 81.5Bridgestone Potenza RE050A 26.6 783 -1.5% 60.9 81.2Bridgestone Potenza S-03 Pole Position 26.7 780 -1.9% 61.2 81.5Bridgestone Potenza RE040 26.7 780 -1.9% 61.2 81.5Bridgestone Turanza ER33 26.8 777 -2.3% 61.4 81.9Continental ContiExtremeContact 26.7 791 -0.5% 60.3 80.4Continental ContiProContact 26.7 782 -1.6% 61.0 81.3Continental ContiSportContact 26.7 781 -1.8% 61.1 81.4Continental ContiSportContact 2 26.7 781 -1.8% 61.1 81.4Continental ContiTouringContact CH95 27.0 772 -2.9% 61.8 82.4Dunlop SP Sport 8000 26.7 779 -2.0% 61.2 81.6Dunlop SP Sport 9000 26.7 780 -1.9% 61.2 81.5Dunlop Winter Sport M3 26.7 779 -2.0% 61.2 81.6Falken Azenis ST115 26.7 774 -2.6% 61.6 82.2Falken Beta FK-451 26.5 785 -1.3% 60.8 81.0Goodyear Eagle F1 Supercar EMT 786 -1.1% 60.7 80.9Goodyear Eagle RS-A 26.6 786 -1.1% 60.7 80.9Michelin Pilot Alpin PA2 26.7 780 -1.9% 61.2 81.5Michelin Pilot HX MXM4 26.9 775 -2.5% 61.5 82.1Michelin Pilot Sport 26.8 780 -1.9% 61.2 81.5Michelin Pilot Sport 26.8 775 -2.5% 61.5 82.1Michelin Pilot Sport A/S 26.7 779 -2.0% 61.2 81.6Pirelli PZero Rosso Asimmetrico 26.7 780 -1.9% 61.2 81.5Pirelli PZero Rosso Direzionale 26.7 780 -1.9% 61.2 81.5Pirelli PZero System Direzionale 26.7 775 -2.5% 61.5 82.1Pirelli P6000 26.7 779 -2.0% 61.2 81.6Pirelli Winter 210 SnowSport 26.8 775 -2.5% 61.5 82.1Toyo Proxes T1-S 26.7 777 -2.3% 61.4 81.9Yokohama AVS ES100 26.7 777 -2.3% 61.4 81.9

As you can see, at an indicated 60mph, the actual speed ranges from 60.3 to 61.8 mph. At an indicated 80mph, the actual speed ranges from 80.4 to 82.4 mph.

Yes, this is not a large amount of error, but it is different from what the calculators would say is a fixed error for all 245/45-18 tires!

Is this significant? Depends on you and how nitpicky you want to be!

Z

I wonder if theres a way we could have certain things disable the thing that eliminates tabs.....

You could always make the table in excel and then attach it as a picture...