Tire size info

[bmacd]

On my explorer, i have my stock wheels and plan to keep them stock (unless you guys can post a hot deal for some flashy rims). The tires say: P235/75R15. What tire sizes will fit? I was reading a "hot deal" here on AT and was wondering if i'm bound to stick to my original tire size.

-=bmacd=-

 

[Evadman]

4 wheeler had an article on what would fit what vehicle. I will see if I can find it.

 

[BCYL]

In case you dont know, here's how to read those numbers on your tires:

235mm is the width of your tires,
75 is the ratio,
and 15 is the diameter of your wheel (in inches).

Since you are not getting new wheels, the last number (15) will not change...

However you can probably fit wider tires (maybe 245, even 255) tires on your stock wheels... but with wider tires, you will need to get thinner tires (ie. decrease the 2nd number), or else your speedo will be messed up...

 

[helloedchen]

Originally posted by: bmacd
On my explorer, i have my stock wheels and plan to keep them stock (unless you guys can post a hot deal for some flashy rims). The tires say: P235/75R15. What tire sizes will fit? I was reading a "hot deal" here on AT and was wondering if i'm bound to stick to my original tire size.

-=bmacd=-

P = passenger
235 = width of threads in mm
75 = aspect ratio
R = radial
15 = diameter, in.

u can add about 5-15mm to the width and it'll still fit your rim i think. it really depends on what you have. consult your manual. i run 195/55 15inchers, but i just got myself a 205/50. still fits fine, and with more grip on the road.

 

[luv2chill]

I'd stick with the 235/75s. I just bought four new Michelin LTX M/S tires for my explorer and it's a much better ride than with the smaller tires that were on there before. I highly recommend the LTX M/S by the way. It also has the net consensus as being the best tire for explorers.

l2c

 

[Howard]

but with wider tires, you will need to get thinner tires (ie. decrease the 2nd number), or else your speedo will be messed up...

No.

 

[BCYL]

Originally posted by: luv2chill
I'd stick with the 235/75s. I just bought four new Michelin LTX M/S tires for my explorer and it's a much better ride than with the smaller tires that were on there before. I highly recommend the LTX M/S by the way. It also has the net consensus as being the best tire for explorers.

l2c

Which means it won't flip

 

[Fandu]

Well you don't have to stay with your stock tire size at all, but you'll probably want to stay as close as possible. The more you change the circumference of the tire, the farther off your speedometer will be. There are several 'rules' to follow. Generally these days people want to go to a lower profile, and wider tire to increase performance. If you don't want to change the rim size through, you go what's called 'Plus Zero'. You can increase the tread width by 10mm, and decrease the profile ratio by 5. So your 235/75R15 could be a 245/70R15 and the overall outer size of the tire will be pretty close (+-1%). Alternativly, you can also increase the rim size. If you increase it by 1" 'Plus One', When you need to decrease the profile ratio by 10. And so on.

 

[BCYL]

Originally posted by: Yucky

but with wider tires, you will need to get thinner tires (ie. decrease the 2nd number), or else your speedo will be messed up...

No.

Can you provide the reasoning behind your comment?

 

[luv2chill]

Originally posted by: BCYL

Originally posted by: luv2chill
I'd stick with the 235/75s. I just bought four new Michelin LTX M/S tires for my explorer and it's a much better ride than with the smaller tires that were on there before. I highly recommend the LTX M/S by the way. It also has the net consensus as being the best tire for explorers.

l2c

Which means it won't flip

LOL... True!!

l2c

 

[Howard]

If you increase the width of the tread, the circumference of the tire will not change. Sure, with a little more rotational mass you slow down a bit, but your speedometer will retain its accuracy, since IIRC it reads the rotation speed of the wheels and converts it into speed. However, if you increase the size of the rims, you will have to decrease the aspect ratio proportionately in order to retain the circumferential length.

Or you could just have your speedo fixed up if you plan to have big rims and big aspect ratios (the Shaq look ).

 

[Howard]

Can you provide the reasoning behind your comment?



EDIT: If you need a little more convincing, we'll do it your way.

Original tire size: P240/70ZR-16.

Increase width to 280mm.

P280/70ZR-16.

According to you, you must reduce the aspect ratio now. Keep in mind that the current circumference is roughly 125cm.

Let's bring the aspect ratio to 50. Fair enough?

P280/50ZR-16.

Now the circumference is 107cm. Now the speedometer will report speeds way over what is accurate.

 

[Howard]

Wait a minute... What do you mean by tread width? I'm taking it to be the width of the part of the tire that touches the road.

 

[BCYL]

Here are some websites about plus sizing:
Here and here. Just some examples, there's more on the web...

You have to decrease the ratio because the contact patch between the tires and the road is bigger after you increase the width of the tires... This in turn means more fiction...

 

[Fandu]

Yucky:
To find the sidewall height, take the aspect ratio in percent, and multiply by the width in mm.


Those are just rules of thumb I posted above. You can't use those to put monster truck tires on your SUV! Here, try this Tire size calculator, according to it, you could go to 280/60R16 and be pretty close.

 

[Fandu]

Originally posted by: BCYL
Here are some websites about plus sizing:
Here and here. Just some examples, there's more on the web...

You have to decrease the ratio because the contact patch between the tires and the road is bigger after you increase the width of the tires... This in turn means more fiction...

Hu? It has absoutly nothing to do with friction. I don't think you people understand how tire sizing works. You have to decrease the aspect ratio to keep the sidewall height the same. You can find the sidewall height by taking the tire width, and multiplying by the aspect ratio. So in order to keep the same overall diameter, when we increase the tread width, and we have to decrease the aspect ratio.

 

[BCYL]

Yucky:

If you still dont believe me, just go to google.com and search for "plus sizing"... There are TONS of sites that document this...

I am still trying to find a site that does a good job explaining the reasoning behind this... I used to have one bookmarked but I lost it...

 

[Howard]

I understand how to find the sidewall height. That's how I calculated cirumference in one of my posts. Recheck if you want.

But why would widening the contact patch increase the sidewall height? This is very strange.

 

[BCYL]

This should clear things up...

The second number is the aspect ratio. This is a ratio of sidewall height to width. In the example above, the tire is 7.28" wide, multiply that by the aspect ratio to find the height of one sidewall. In this case, 185x0.60=111mm or 7.28"x0.60=4.36".

This example is from a 185/60R14 tire...

If you take a 195/60R14 tire (thus not changing the ratio), the height of one sidewall will become 195x0.60=117mm, compared to the 111mm of the original tire...

 

[Howard]

I am the stupidest man on earth. I totally forgot about aspect ratio.

Sorry guys.

 

[Fandu]

Yucky, watch:

Take a 245/70R15. Now increase the width to 255/70R15.
Sidewall 1: .70 x 245
Sidewall 2: .70 x 255


Obvisouly the sidewall increases height. However, if you decrease the aspect ratio at the same time, say 255/65R15, it's very close to the original.

The aspect ratio is the ratio of the height vs width. So if you keep the aspect ratio the same (70), and increase the width, then the sidewall height also has to increase to keep the aspect ratio. It all works out quite well.

 

[BCYL]

Originally posted by: Yucky
I am the stupidest man on earth. I totally forgot about aspect ratio.

Sorry guys.

Dont worry about it

I forgot the reasoning behind having to decrease the aspect ratio as well

 

[Pacfanweb]

Explorers came with 2 tire sizes, pre 2002.

Standard was 235-75-15.

Optional was 255-70-16.

You can easily go to 255's, just move to 70's.


BTW, the 255 is the measurement from bead to bead. All the way up the side, across the tread, down the other sidewall.

 

[bmacd]

tyvm everybody

-=bmacd=-