mmorris

I just replaced the 225's on my 01 Sport with 215's which the sticker on the door says is the correct size. Using a GPS, I notice that now the speedo shows 4 mph faster than our actual speed. Someone said in an earlier post that some Sports had 225's as original equipment. My question; What advantage do 225's have over 215's that the company would use them over 215's? My previous experience with other vehicles is that the narrower the tires the BETTER the traction in snow and mud. Do the 225's offer more stability on the highway, braking power, or what?
I do notice that the "grabbing" when the wheel is cranked fully to one side when starting forward from a stop has ceased since putting the 215's on.

Potatowalker

going from 225 to 215, you've changed the diameter of the tire, not the width. With a larger diameter the wheel takes longer to make a full rotation and v/v which is why it throws the speedo off. The factory spec sheet I got from chrysler for my 99 sport VIN lists it as coming stock with 225x75R15 tires.

With stock gears you will likely get slightly better mpg with 225s (and cruise on the HWY at a slightly lower RPM) unless your towing a horse trailer or something. Also since they have a slightly larger footprint, 225s will roll smoother than 215s by a small amount, on things like washboard gravel and pot-holes.

Potatowalker

As far as snow tires go, having been a ski bum since '99 i've had plenty of time to experiment with tires for snow. I too have heard that a skinny tire will get better traction in snow/mud and I actually believed it enough to try a set of skinny Wintermasters for my Ford Ranger when I had that. I did not find them any better at all, except maybe at slow speeds in deep powder. The only difference I found in those tires was the rubber compound was softer and had more siping. Those are two of the more important things to look for in a snow tire. The other major thing to look for is the actual tread pattern. Some mud tires are awesome at accelerating and braking in snow, but terrible at holding a turn - no lateral stability. Mickey Thompson MTZs fall in that category in my experience. For snow, I look for a tire that has as much bite from side-to-side as it does front and back, a soft rubber compound and lots of siping. The MTs had nothing but angled tread blocks with no siping that just made the front end slide in turns even going slow. they were awesome on slickrock though. The Goodyear wrangler Duratracs that I have in a 31x10.5x15 are by far the best snow tire I've ever had. They have square blocks on the edges and angled ones in the center so they roll smooth and quiet on pavement but dig and churn like mad in anything soft. The Duratracs are better than BFG ATs even, which are my second choice for mud/snow.

Firestorm500

Potatowalker:

"going from 225 to 215, you've changed the diameter of the tire, not the width."

No, that's wrong. Both dimensions change.

A P215/75R15 is shorter AND narrower than a P225/75R15, assuming they are both the same brand.

There can be variance between brands, which we are not addressing here.

jakbob

Yup. For example a 225/75r15 has a 225mm width, and 75% of that is the sidewall.

Potatowalker

True, thank you for correcting! I gotta stop posting when I'm not fully awake! Since he never mentioned the other number I think I was trying to just give general info, but definitely forgot to mention that one is a percentage of the other.

MACherokee

http://tire-size-conversion.com/tire-size-comparison/

concealer404

FWIW, it took putting 235/75-15s on my Sport to get the speedo to match a GPS.

jakbob

That is the stock tire size... so it would make sense that putting stock wheels back on with the stock speedo gear, would correct then speed.

concealer404

Very strange. I guess i never bothered looking at the sticker on the truck, but TireRack seemed to think that a 215/75-15 is stock size.

Firestorm500

The vehicle is the correct source. Don't take TRs word for anything.

jedijeb

My 85 xj was 215 stock with 225 optional which the original owner had moved up to before parking it. Now it has 235 on it, need to check to see how much the speedo is off now.

Definitely consult the owners manual and door sticker(if it is still there) to be sure what size was stock.