Truck tire sizes and general recommendations.

Discussion in 'Off Topic [BG]' started by two fingers, Jul 21, 2017.

  1. Don't forget a wheel alignment to get your new tyres properly on the road.

    For only occasional off tarmac and snow use you might be ok to use a highway tyre but carry chains just in case.
     
  2. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois
    It might be the easiest but it's the least acceptable of all the options.

    You never want to increase the aspect ratio of a tire to larger than stock because it makes a dramatic difference in cornering ability.

    His stock tires are 70, which are already mediocre for handling. Going to a 75 tire will result in his truck more noticeably plowing around turns and he'll have less traction because of it.

    One could argue that the actual amount of degraded handling performance is negligible but I would reject that argument when it comes to trading performance and safety for a minor cosmetic change.

    Increasing either the tread width or the wheel diameter (or both), while maintaining the same aspect ratio, will provide the desired "taller" tire size without harming performance.
     
    two fingers likes this.
  3. Both of these tires are 70's but they are different widths. In metric ratings the width of the tire is the first number and the second number is the size of the sidewall as a percentage of the width. The one on the left is a 315 70 17 and the one on the right is actually a 285 70 17. As far as problems go with tire sizes it really comes down to the exact vehicle you are working on. For instance a 285 70 17 may not rub on the front end of a 2010 chevy 1500, but sometimes they do. One big reason is that there are different trims on the valences underneath another is that tires adhere to the same loose set of measuring rules that flat screen tv's do, where as long as its close it qualifies.
     

    Attached Files:

    two fingers likes this.
  4. also, most full size trucks notice no real performance change when going from a 32 to a 33.
    Going with a taller wheel will only make the tires cost more and ride worse especially if you get a proper e rated tire. Additionally most of the time the backspacing on aftermarket wheels is such that it pushes the tires out from the vehicle.
    There are really a ton of variables that can only be answered by starting with what truck you own.
     
    two fingers likes this.
  5. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois
    Yes.

    I'm doing some tire shuffling this weekend because I'm putting some autocross tires on my Merkur XR4ti and I've had to do some homework (mostly asking around the enthusiast forums).

    Stock Merkur tires are 195/60/15. I went with the Hankook Ventus S4 tires in 225/45/15 because I want to go in the opposite direction the OP in this thread does - I want a smaller tire so I can get crisper acceleration and a shorter, stiffer sidewall for better handling. In this case, the difference in circumference is 5.2%, which is quite a bit. The difference in going from 60's to 45's is enormous when it comes to handling.

    Coincidentally, I can use the tires that are stock on the Merkur to upgrade my older Mercedes 450SEL, which currently has the ridiculously obsolete 205/70/14 tires on steel rims. I have a set of Wolfrace 15" wheels which will take the set of 195/60/15's. This is also a switch to a smaller tire but in this case, only 4.2%. this is okay, because the Mercedes is a 3 speed automatic that is quite anemic in town but really wakes up at highway speeds. Smaller tires will really help acceleration and the shorter sidewall ratio will give me better cornering ability.

    Both of these vehicles are older cars that are designed for small wheels, and going bigger than 15's on either isn't practical without modifications to the wheel wells.



    Here's a better tire size calculator:
    Tire Size Calculator - Discount Tire Direct
     
    Last edited: Jul 21, 2017
  6. Mike N

    Mike N Missing the old TB Staff Member Supporting Member

    Jan 28, 2001
    Spencerport, New York
    Rim width will be the real factor in going from a 265 to a 285. Have someone measure your stock wheel width and see if it's wide enough for a 285.

    I really don't think you're changing size to the point that speedo or transmission shift points will be an issue.

    Fwiw, I would prefer an LT tire versus a P tire.
     
  7. hondo4life

    hondo4life

    Feb 29, 2016
    SC
    I like stock sized tires in most cases.
    I put wider tires on my econo car because the OE pizza cutters were a joke, and my truck went from P225 to LT245 because it is just a beater for playing in the woods.
     
  8. bolophonic

    bolophonic

    Dec 10, 2009
    Durham, NC
    I asked my mechanic about putting bigger tires on my Tacoma for aesthetic reasons the last time I bought a set and he kind of rolled his eyes at the request. I trust him implicitly, so I accepted his explanation that the safety and handling trade-offs were not worth it for a more aggressive looking truck.
     
    two fingers likes this.
  9. It's hard to find trustworthy mechanics so I understand you trusting him implicitly but he steered you wrong (pun intended). There are several ways to accommodate fitting a larger tire on a Tacoma and when done right the ride quality is either the same or drastically improved. There are about a million ways to look at how vehicle dynamics will change in theory but until you've done it a whole bunch of times it's hard to give first hand experience, the problem lies in trying to find a shop that has done it a whole bunch of times that isn't just trying to push a product on you.
     
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  10. two fingers

    two fingers Opinionated blowhard. But not mad about it. Inactive

    Feb 7, 2005
    Eastern NC USA
    So, this update will be hilarious to some of you.... after I quit being angry at myself it was funny to me anyway.

    A neighbor/friend had recommended an online place to buy tires. He and I had been talking about his tires the day before. Clearly, the size of his tires got stuck in my head. All this time I was doing the math and having a conversation with you guys about tires that fit HIS truck (a 2010 full size Toyota) not MINE. I spent quite a bit of time with online tire size calculators and the whole bit. :poop:

    Short version of the resolution is this. The stock size of tire on MY truck was actually 265/65/18. :wacky: I had already placed the order for the incorrect size at Discount Tires Direct. It dawned on me what I had done so I called and put a hold on the order. I was driving another vehicle at the time and needed to get home and confirm my tire size. They actually set it up to call ME back.. They were extremely helpful at rescuing me from my stupid self.

    After a discussion with the customer service guy there I wound up getting a 275/65/18 Yokohama Geolander A/T G015. It is only slightly taller and even less of a difference in width. It gets great ratings on the highway, great noise ratings, and "meh" off road ratings. Perfect for the reality of my lifestyle. I so rarely get off road it's not worth having mud tires that are great for off roading but noisy. Having priced the same tire here locally I saved quite a bit of money. Even after paying my mechanic to install and balance them I will save over $150 and get a $30 rebate Visa gift card. Their customer service and web site are both great.

    The tires should be on my doorstep Wednesday and installed by Thursday afternoon.

    Thanks for the help everyone. Sorry for the confusion. :banghead:

    :D
     
    BasturdBlaster likes this.
  11. It may work differently in your world but you might get a surprise how much your mechanic charges for fitting and balancing, compared with the discount rates at the tyre shops when they sell you the tyres.
     
  12. two fingers

    two fingers Opinionated blowhard. But not mad about it. Inactive

    Feb 7, 2005
    Eastern NC USA
    Thanks for the heads up. But I already got a quote from them as well. We're all set. And, yes, it's a bit more than what installation would be if I had bought the rubber from them. But with as much as I saved overall I'm OK with that.
     
  13. hondo4life

    hondo4life

    Feb 29, 2016
    SC
    Good choice of tire, and about 10 mm width and tiny bit of sidewall is not a big deal. Discount Tire is really good. I have ordered many tires from "direct", and often take my cars to their shops even though I have my own tire machines at work.
     
    two fingers likes this.