1. Ash_Whole

    Ash_Whole Member

    Messages:
    9
    Likes Received:
    1
    Joined:
    Aug 28, 2020
    Location:
    Vancouver BC
    is this tire too small to work properly in a Volare?

    245/60/15 fit better? or what about 255/60/15.

    stock suspension, with the stock cop rally wheels
     
  2. Camtron

    Camtron Well-Known Member

    Messages:
    575
    Likes Received:
    226
    Joined:
    Apr 25, 2019
    Location:
    Here
    I have 245/60/15 on my Fifth Ave. it helped out the 2.94 gear ratio a little bit and hooks up well enough for low Hp cars..but it does leave a bit of space in the wheel wells (especially after removing the chrome trim)...I’ll be going 255/60/15 for the next set.
    Otherwise I haven’t had an issue with handling or ride quality.

    363A035C-0937-4FD8-A25A-0DFB14EBF448.jpeg
     
    MoparDan likes this.
  3. Duke5A

    Duke5A Well-Known Member

    Messages:
    916
    Likes Received:
    383
    Joined:
    Apr 6, 2018
    Location:
    Michigan
    Factory tires are like 205-70-15. I wouldn't use anything smaller than a 60 series myself.
     
    toolmanmike and MoparDan like this.
  4. Ash_Whole

    Ash_Whole Member

    Messages:
    9
    Likes Received:
    1
    Joined:
    Aug 28, 2020
    Location:
    Vancouver BC
    what is the largest the front will fit?
     
  5. Duke5A

    Duke5A Well-Known Member

    Messages:
    916
    Likes Received:
    383
    Joined:
    Apr 6, 2018
    Location:
    Michigan
    235-60-15 fits without any issue. I've got larger on the front of my car, but I also have 300# torsion bars.

    275-60-15 fits in the back without any rubbing either.
     
  6. Hayzoos

    Hayzoos Active Member

    Messages:
    35
    Likes Received:
    8
    Joined:
    Aug 9, 2020
    Location:
    Revloc, PA
    This is so much easier to answer in flotation sizes like I would put on the Jeep I used to have. 32x10.5 simple 32" tall by 10.5" wide and rim size doesn't matter.

    Pmetric gets tedious doing the math. But here we go, first number is width in mm, divide by 24.5 for inches, second number is sector ratio as a percentage so 60 means 60% which means multiply the width by .6 for the side wall height from rim to tread so double that and add the rim size of 15" for overall tire height. I'll do the math on the sizes mentioned.
    Duke5A says 275-60-15 on rear which is 11.22" wide by 28.47" tall and 235-60-15 up front which is 9.59" wide by 26.51" tall.
    also the 205-70-15 factory (civilian) is 8.37" wide by 26.71" and the police 215-70-15 is 8.78" wide by 27.29" tall.
    For reference your sizes are 245-40-15 are 10.0" wide by 23" tall and 245-60-15 is 10.0" wide by 27.0" tall and 255-60-15 is 10.41" wide by 27.49" tall.
    The police wheels are heavier and slightly wider. But you may need to go even wider going to at least 10" wide tires.
    Tire fitment is not as simple as how wide or how tall. Just as important is where the inside corner clears which is both a tall and wide factor. Front is more complicated by the steering arc, lock to lock is the most constrained. You need to also consider wheel offset/backspacing and possibly factor in new wheels to fit wider tires. Knowing the actual sizes you can measure on what you have mounted now for the additional. You have to think three dimensionally though. Don't forget to consider suspension up travel. If what you want still don't fit then it's time for a lift kit, (oh, wait that was the Jeep ;-)

    I have fitted the police size. Funny thing is my speedo and odometer is dead on now. That's another thing to consider when changing size, speedo/odometer reading will change. Fix by changing out the speedo driven gear to the correct tooth count. The correct tooth count depends on both tire height (actual height at typical load and pressure) and rearend gear ratio.

    *******incorrect calculations above due to wrong conversion factor. It should be 25.4 not 24.5 as later replies state. I made a post below with math based on correct factor. Thanks to Camtron and kkritsilas for identifying my error.
     
    Last edited: Sep 11, 2020
    Duke5A likes this.
  7. Duke5A

    Duke5A Well-Known Member

    Messages:
    916
    Likes Received:
    383
    Joined:
    Apr 6, 2018
    Location:
    Michigan
    I agree, the numbers are stupid. The sizes I listed though I've personally used on my 5A and my Dad is using those same size tires on his coupe as well.

    Go too tall or wide in the front and you'll rub the torsion bar and K frame at full lock. I was doing this with 255-45-18, so I stepped back down to 245-40-18.
     
  8. Camtron

    Camtron Well-Known Member

    Messages:
    575
    Likes Received:
    226
    Joined:
    Apr 25, 2019
    Location:
    Here
    245/60 definitely isn’t a 27” x 10” tire. It’s a little over 26.5” tall and a little over 9.5” wide.
    In fact, non of those number posted above are accurate as I check them.
    A 275/60 is 28” x 10.8”...not 28.47” x 11.22”...and so on and so forth.
    Anyway, take what’s on the internet as a grain of salt. Even what gets posted here.
    Factory tires were 205/75/15 on stock M bodies (27” x 8”) and what’s recommended as the minimum tire size for “standard load”.

    Tire Size Comparison, here’s a nifty calculator with visual comparison of sizes.
    As well, my factory door sticker.

    image.jpg
     
  9. kkritsilas

    kkritsilas Well-Known Member

    Messages:
    1,863
    Likes Received:
    367
    Joined:
    Jun 21, 2012
    Location:
    Calgary, Alberta, Canada
    Hayzoo's correction factor for metric to Imperial (inches) is incorrect. It is not 24.5, it is 25.4.

    Also, the section width and aspect ratios are approximate. You can have 245/60 tires from a range of manufacturers, and the section width (not the same as the tread width) can vary slightly, as can the actual sidewall height, and by extension, so will the tire's overall height.

    i use Tire Rack's tire finder and dimensions when looking at tires.
     
  10. Hayzoos

    Hayzoos Active Member

    Messages:
    35
    Likes Received:
    8
    Joined:
    Aug 9, 2020
    Location:
    Revloc, PA
    Sorry everybody, I did get the conversion factor wrong. It is in fact 25.4mm/in.
    Here is the math redone with the correct factor.
    Duke5A says 275-60-15 on rear which is 10.82" wide by 27.99" tall and 235-60-15 up front which is 9.25" wide by 26.10" tall.
    also the 205-70-15 factory (civilian) is 8.07" wide by 26.30" and the police 215-70-15 is 8.46" wide by 26.85" tall.
    For reference your sizes are 245-40-15 are 9.65" wide by 22.72" tall and 245-60-15 is 9.65" wide by 26.57" tall and 255-60-15 is 10.04" wide by 27.05" tall.
     
  11. AJ/FormS

    AJ/FormS Well-Known Member

    Messages:
    1,183
    Likes Received:
    265
    Joined:
    Apr 26, 2016
    Location:
    On the Circle of the earth, Southern Man,Canada
    Furthermore;
    The real-life section-width will only match the spec when the tire is mounted on a rim that is 70% of the branded size.
    Furthemore, all numbers are rounded to the nearest 5mm.

    That means;
    that a 275/60-15 might have a measured section of between 271 and 279 on the 70% rim which is .7 x275=192.5, which is 7.56, rounds down to a 7.5" rim.
    OK so 271 is 10.67 and 279 is 10.98; giving a section range of 10.67 to 10.98 on a 7.5" rim..........
    The sidewall height will then be; 60% of that, so 6.40 to 6.59. Multiplied by two and adding 15, I get a height of; 27.8 to 28.18.............
    What's it mean?
    Well, the manufacturer mounted his tire on a 7.5" rim, and measured it. If the section fell between 271 and 279; it got branded 275. And if the sidewall height fell between 6.50 and 6.59, then it got branded 60%.
    You would think.
    No that's not exactly right, because the aspect-ratio of 60% is not an exact number, but rather, just rounded to the nearest 5 like 50,55,60,65 etc.
    So that 60% number on the tire could be anywhere in the range of 56% to 64%
    Sheesh.............
    Ok but no streeter in their right mind installs a 275/60 on a 7.5rim. That is just the spec rim.
    More than likely, you will install it on an 85% rim, which is 9.20. And there ain't no 9.20 rim that I have ever seen, so that will round up to a 10", or down to likely an 8.5". I ran them on 8.4s no problem.
    Ok but on an 8.5 rim, that baby is no longer a 275. The sidewalls will move larger, perhaps, I'm guessing one-half the difference from 7.5 to 8.5 which is .5 x1.0= 1/2 inch, which is ~13mm.... so the tire becomes 271 to 279 plus 13= 284 to 292.........
    Ok now, even tho the tire is the exact same tire, the aspect RATIO is a RATIO, so now, that number has to reflect the new section width, so:
    The height of the sidewall does not physically change , so is still 6.40 to 6.59 which is 162 to 167 , making the new aspect ratio; 162 to 167/284 to 292, lol. And the range there is now;AVERAGED to 164.5/288=57% .......
    So now, we started as branded 275/60-15, on a 7.5,
    which on an 8.5 might actually measure as a 292/57-15 AVERAGE. The mounted tire might measure +/- 4.999 mm in any direction!
    Ain't it grand.................
    But it gets worse;
    Because the height is ethereal, and it gets multiplied by 3.1416 to get your tire roll-out, your tire roll-out will affect your speed-O by the variance or +/- 15.67mm..... On the 292/57-15, the roll out is, 88.296 inches +/- .617 inches...... which is 87.68 to 88.91 or 1.23 inches from min to max. or 1.41% or, ~1mph @65 mph.
    EDIT
    OOps I noticed that some of my math is off a tad, not enough to be meaningful, so I'm not gonna redo it; The point is all the same; Until you install a tire on your chosen rim, and MEASURE it; all bets are off.
     
    Last edited: Oct 10, 2020
  12. AJ/FormS

    AJ/FormS Well-Known Member

    Messages:
    1,183
    Likes Received:
    265
    Joined:
    Apr 26, 2016
    Location:
    On the Circle of the earth, Southern Man,Canada
    Another thing worth mentioning is;
    a 40 series tire has a very short sidewall. The rim runs very close to the road. And you gotta protect the tire with additional pressure.
    IDK what your roads are like in Vancouver, but here in Manitoba, the only place I could imagine running a 40 is on certain hiways in certain stretches. Any place else, they would rattle my kidney stones right down the chute, which pain I am doing my utmost to never again experience. no lol.

    The taller your sidewalls, the plusher the ride. There is a reason Grandpa rides on 75s
     
  13. Ash_Whole

    Ash_Whole Member

    Messages:
    9
    Likes Received:
    1
    Joined:
    Aug 28, 2020
    Location:
    Vancouver BC
    thanks. i just want to put the largest tire that can fit, dont really care about sidewall/ratio/width.
     
  14. AJ/FormS

    AJ/FormS Well-Known Member

    Messages:
    1,183
    Likes Received:
    265
    Joined:
    Apr 26, 2016
    Location:
    On the Circle of the earth, Southern Man,Canada
    Well, looking at my 1980 Volare, I think I could put a 29/30 incher in there at about 13/14 section width. I might have to push the axle back a tad.
     
  15. Kramer79

    Kramer79 Member

    Messages:
    21
    Likes Received:
    2
    Joined:
    Dec 29, 2020
    Location:
    Connecticut
    Great tire comments, I may go 235 70 15 on the back and 215 70 15 (or 75) on the front. Unless my urge for a mud tire on the back stays - then I guess 215/75/15 all around. 235/75/15’s would not fit the rear I’m guessing...
     
  16. Ash_Whole

    Ash_Whole Member

    Messages:
    9
    Likes Received:
    1
    Joined:
    Aug 28, 2020
    Location:
    Vancouver BC
    as a small update, the 255/60/15 fit front and back with the cop wheels
     
  17. Kramer79

    Kramer79 Member

    Messages:
    21
    Likes Received:
    2
    Joined:
    Dec 29, 2020
    Location:
    Connecticut
    Thanks, the cop ones were 8 vs 7 wide? I have the stock steelies ...
     
  18. 80mirada

    80mirada Well-Known Member

    Messages:
    1,247
    Likes Received:
    378
    Joined:
    Sep 3, 2012
    Location:
    Wisconsin, Fort Atkinson
    Police wheels are 15x7, standard wheels were 15x6. Early Ramchargers, Super Coupes and Kit Cars were 15x8