1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

315?75R16,s without gear change ?

Discussion in '80-Series Tech' started by MTNRAT, Jul 2, 2003.

  1. MTNRAT

    MTNRAT

    Messages:
    1,181
    Likes Received:
    18
    Joined:
    Mar 27, 2003
    Location:
    Fernie B.C.
    What are peoples experiences/opinions on running 315/75R16,s without changing their R&P gears? Will having a superchrger make a difference?
    Thanks,
    Sean.
     
  2. MTNRAT

    MTNRAT

    Messages:
    1,181
    Likes Received:
    18
    Joined:
    Mar 27, 2003
    Location:
    Fernie B.C.
    Anyone?
    Sean.
     
  3. CruisinGA

    CruisinGA

    Messages:
    6,163
    Likes Received:
    8
    Joined:
    Mar 27, 2003
    Location:
    Georgia Tech
    Check a later thread about OME lift-Junk specifically says that 315's with stock gears are a no go.
     
  4. MTNRAT

    MTNRAT

    Messages:
    1,181
    Likes Received:
    18
    Joined:
    Mar 27, 2003
    Location:
    Fernie B.C.
    Thanks. I just read that.
    Regards,
    Sean
     
  5. Junk

    Junk

    Messages:
    6,185
    Likes Received:
    23
    Joined:
    Dec 13, 2002
    Location:
    buggerville nj
    Rat - I'd say if you're running 315's on street than no, but if you're 31-33 on street and 315 for trail only, then you'd be ok. Otherwise you'll just have some big butt tires and will feel worse than if you were driving a down and out 3fe. :eek: :D
     
  6. landtank

    landtank SILVER Star

    Messages:
    18,421
    Likes Received:
    601
    Joined:
    Mar 27, 2003
    Location:
    Groveland MA
    I'm going to disagre with Junk. I ran 315s for almost 2 years with stock gearing. There was loss of performance yes but no where near what Junk is describing. I was still able to tow my 3500 lb camping trailer through the white mountains! Kept it in power mode, overdrive off and allert to hill climbs ahead. I now have the 4.88s in and the difference is remarkable of course. If your final goal would be to eventually do both tires and gears then go for it even if tires is all you can do now. If your not a power junky you probably won't notice it any way.

    BTW: a friend who drives Range Rovers though I had alot of power when he drove it with just the tires! It's all perseption :D.
     
  7. T Y L E R

    T Y L E R

    Messages:
    2,598
    Likes Received:
    2
    Joined:
    Mar 27, 2003
    Junk , bite me dude ! :-*

    MTNRAT ,

    I have a suggestion ... go for the 315 , but wire up a Truspeed recallibrator . The results may be a useful compromise for you .

    Right up front , you're going to have to accept some power loss off the line . However , some time after first your 80 will respond a lot better ...... I'm being vague here because I am still not sure why some of the time my 80 flies out of first gear , and other times it sort of lacks .

    Gut impression : My 80 is still a blast to drive . If I did regear , and/or add a SC , I probably kill someone and end up in jail *L*

    As always you won't 'really' know until you either test drive a quiver of different 80's , or you try some mod out yourself .

    Quite a few acceptable variations between the 'Poser' and 'Crawler' poles . All in one's perspective ...

    Tyler ( *checking breathing apparatus and climbing into flame resistant suit* )
     
  8. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

    Messages:
    20,564
    Likes Received:
    2,891
    Joined:
    Mar 27, 2003
    Location:
    Surrounded by Cruisers from all over the world
    Tyler,

    I'm so glad you are back!

    now, about that tea holder, details please.
     
  9. T Y L E R

    T Y L E R

    Messages:
    2,598
    Likes Received:
    2
    Joined:
    Mar 27, 2003
    Yeah , yeah ... ::)

    You and Beo just won't be happy until ya'll make me reverse engineer that brief phrase into a 'real' product , will ya ?

    'T'
     
  10. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

    Messages:
    20,564
    Likes Received:
    2,891
    Joined:
    Mar 27, 2003
    Location:
    Surrounded by Cruisers from all over the world
    Tyler,


    Sir, are you implying that your tea holder exists only in your sig line? Say it aint so....... :'( . An admission like that may require me to rescind my sig statement regarding ballancing. ::)
     
  11. T Y L E R

    T Y L E R

    Messages:
    2,598
    Likes Received:
    2
    Joined:
    Mar 27, 2003
    Oh , hell no .... *pausing* ... but hey , if the 'pin head' fits ...

    *[glow=red,2,300]RUNNING LIKE HELL!![/glow]*

    Tylerrrrrr
     
  12. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

    Messages:
    20,564
    Likes Received:
    2,891
    Joined:
    Mar 27, 2003
    Location:
    Surrounded by Cruisers from all over the world
    After you,.... tossing beach rocks and kicking pine cones........... :p
     
  13. cruiser99

    cruiser99

    Messages:
    273
    Likes Received:
    2
    Joined:
    Jun 11, 2003
    Location:
    Vail, Arizona
    If I can add something to the discussion,

    I Have a 100 series and after I added the 315 the driving experience did change noticeably.

    Gas mileage went up by 2 mpg

    In addition to the fact that my truck is fully “accessoriesed”, when fully loaded, the truck will not hold cruise speed at the slightest suggestion of incline. It will down shift to 3rd and stay there “forever”.

    Of road, with all the obvious benefits of big tires, there is a noticeably lost in torque and this directly effect how smoothness of the power delivery. It took some time to get used to.

    Reliability and breakage is yet to be seen.

    Just my observation
     
  14. Photoman

    Photoman SILVER Star

    Messages:
    1,145
    Media:
    41
    Likes Received:
    47
    Joined:
    Mar 28, 2003
    C-99,
    Is your speedometer adjusted for the tire size? If not it can affect the odometer readings and hence the gas mileage figures or did you use a GPS?. In flat country I could see gas mileage possibly increasing with larger tires but in hilly country I would think it would decrease as you have to run the rpm's up in a lower gear to pull the taller tire.
    Bill
     
  15. MTNRAT

    MTNRAT

    Messages:
    1,181
    Likes Received:
    18
    Joined:
    Mar 27, 2003
    Location:
    Fernie B.C.
    Here is the gist of my dilemma. I have yokohama geolander AT+11,s in a 285/75R16, and I am a little nervous about using them for the rubicon trail, even though they worked well on the rock in Moab. They only have 15000 miles on them. So I figured that some MTR,s might be in order and stay with the same size and sell the yokos. Then I figured why not go with 315,s because my longterm (within a year or so) would be to regear and get 315,s anyway I THINK??. So if I get 315,s now I would not have to buy two sets of tires, (the 285,s and then the 315,s). Or should I just run my yokos on the rubicon and wait for the 315,s till I regear. My head hurts just thinking about it.
    I do have a supercharger so I figure I would still have enough power.
    Thanks for the help so far.
    Sean
     
  16. landtank

    landtank SILVER Star

    Messages:
    18,421
    Likes Received:
    601
    Joined:
    Mar 27, 2003
    Location:
    Groveland MA
    I still say put them on! Your supercharged so it should have enough power.
     
  17. cruiserdan

    cruiserdan SupportingVendor Emeritus Supporting Vendor Moderator

    Messages:
    20,564
    Likes Received:
    2,891
    Joined:
    Mar 27, 2003
    Location:
    Surrounded by Cruisers from all over the world
    The blower will over-come 315's easily. You will still feel a difference though. Remember that it is important to correct the speedometer readings in order for the various electronic components to function correctly. Overall drivability is improved.
     
  18. cruiser99

    cruiser99

    Messages:
    273
    Likes Received:
    2
    Joined:
    Jun 11, 2003
    Location:
    Vail, Arizona
    Jim thanks for the comment.
    You are correct about the need to make odometer correction for the calculation of the gas mileage. I have a difference of 12% between the speedometer and the GPS readout the stock one reads slower. The numbers I mentioned earlier take this into account. The reason the mileage goes up is; more rotating mass to keep spinning, greater lolling resistance due to more rubber flexing and higher aero drag, much higher. Also, without getting too technical, the motor is not working at its most efficient rpm range, but this is kind of hard to understand. (Took me a while)
    Doron.
     
  19. shocker

    shocker

    Messages:
    1,185
    Likes Received:
    1
    Joined:
    Apr 10, 2003
    Location:
    Kansas City, MO
    Do you mean to say that your gas mileage went down and not up? ??? i.e. it was 15mpg, now it's 13mpg.

    I think Bill's confusion (and mine, and ???.....) stemmed from the fact that we thought you meant that your gas mileage improved 2 mpg, i.e. was 15, now 17.
     
  20. Jim_Phillips

    Jim_Phillips

    Messages:
    723
    Likes Received:
    1
    Joined:
    Mar 27, 2003
    Location:
    Ingerland
    My rekoning is that you would expect MPG to go down purely on the basis that your speedo is out. If your speedo is callibrated to the original tyres - 260x70x16 (at least that's what they are in the UK) and you then change to 315x75x16 -you are changing from a 30.3 to a 34.6 inch tyre. That's a difference of nearly 12.5% in the diameter.

    In other words, your wheel travels 12.5% further to register 1 revolution. Or another way of looking at it is that your odo will read 13.14 miles when you have in fact travelled 15 miles. Do your MPG calculations again and then add 12.5 %.

    I think I'm right, aren't I??

    Jim