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changing tires?...power problems?

Discussion in 'References' started by oldsnowman, Nov 5, 2008.

  1. oldsnowman

    oldsnowman Member

    this info is for anyone out there who is thinking about changing there tires on there mini's.
    www.1010tires.com has a tech section that has a tire size calculator that will give you;
    overall height
    rev's per mile
    section with
    speed change
    and much more...
    you just put in stock tire size 145 80 12 and scroll down and put in the size you are look at.
    this calculator will tell you when the tire size you pick is too big compared to stock.
    too big of tire will cause power problems
     
  2. jtpc

    jtpc Member

    Thanks, I'm changing my wheels/tires so I'll be back to stock size.
    I am just not getting the power & fuel economy I am looking for with the change in size.
     
  3. jtpc

    jtpc Member

    Just got my wheels changed out today. And wow, what a difference! I can actually get up to 105+kph!
    It cruises great at 85-90kph (55+mph) with no problem.
    And the issues with climbing hills are gone.

    (I recommend keeping with wheels/tires that are close to factory. I learned this by experience)
     

    Attached Files:

    Last edited: Feb 8, 2009
  4. oldsnowman

    oldsnowman Member

    glad i could help...power is important with these little truck and keeping with 3% of stock will really make a difference :D
     
  5. JetBoy

    JetBoy New Member

    Weber here. Just put new wheels and tires on my '94 MiniMtz. Wheels are MB-5X 764M4503MSM35 and the tires are Kumho Power Star 758 175/65 R14 82H. Handles much better than th e stock 12s. Primarily using the MiniMtx as a toy on the road. On the hiway at 105k she handles great and the engine is not as wrapped up in 5th gear as she was with the 12s. On that subject, anybody know of a small tachometer for the 660cc? Weber out
     
  6. Timetripper

    Timetripper Moderator

    Just do a "Search" for "tachometer" - lots of threads/ posts about this already
     
  7. slimbad

    slimbad Member

    tachometer

    JetBoy,

    Out of the 24 threads you find when searching for "tachometer" this prob answers your question best:

    http://www.minitrucktalk.com/showthread.php?t=2486

    later, slim

    Mods, reckon this thread could be merged into the tach sticky??? Tks, slim
     
  8. Windmill

    Windmill Member

    Typed up a difference between tire sizes. Between 12 and 13 there is a 95 lower rpm with the 13" I guess that is at idle. My question for you smart people, with acceleration will that 95 stay the same or increase? Will I have lower rpm's at 25,40 or at 55?
     
  9. rayallen

    rayallen Member

    Windmill....The rpm drop will be the same. You will loose top end power with larger tires.
     
  10. oldsnowman

    oldsnowman Member

    i got my tach from canadian tire...works great and was only $45.00. its small i think 2 5/8", check my pic's there a picture in there.
    HTH...wyatt


     
  11. oldsnowman

    oldsnowman Member

    i think what you are asking is will the rpm stay the same at speed with bigger tires...no, the pm will be slower with bigger tires putting more load on the engine to pull the truck. go to 1010tires.com and you check your rev's per mile and you will see that changing to a tire taller then stock is not a good plan if you plan to drive the hyways. i am putting 14" wheels (check my pic's) on my truck and i found 165/55-14" tires. the 14's are 21.2" tall and the stock tires are 21.13" tall, this is going to look good with out over loading the engine at hyway speeds. right now my truck rev's ar 6500 rpm at 100kph, and remember these engines make all there horse power high up on the tach...so let her spin!!:D:D


     
  12. Windmill

    Windmill Member

    Tells you what I know. I thought with it running at lower rpm's that it would get better gas mileage.
     
  13. MiniBrutes

    MiniBrutes Gold Supporting Member

    Theory is correct windmill, but the reality isnt. If the engines were more powerful this would likely be correct, however due to the limited power, you are working the engine harder, thus burning more fuel.

    The thing you have to keep in mind is the powerplant you are dealing with. This thing doesnt have 400 ft/lb of torque at 2500RPM. It NEEDS the revs to make power. Most small engines work this way, from little tiny R/C cars and planes, to motorcycles. Heck, they have some of those model engines get max power over 20,000 or 30,000 RPM. I read somewhere once of a little guy that did about 110,000 RPM.

    Makes our 7000-8000 rpm look like childs play.
     
  14. Windmill

    Windmill Member

    I am glad someone post this. I would have made a bad mistake.
     
  15. MiniBrutes

    MiniBrutes Gold Supporting Member

    Your time would be better spent on lightening up the truck and aerodynamics. Drag and headwind are 2 of your biggest enemies.

    I wouldnt doubt that some rather simple aerodynamic modifications could make a big difference for use at max speeds. I remember taping up the hood gaps and other parts of the car for doing top-speed runs. simply reducing that drag made a few mph difference.
     
    Last edited: Feb 10, 2009
  16. Mighty Milt

    Mighty Milt Moderator

    No2 :eek: that'll make it faster... for a while :D
     
  17. o8k

    o8k Member

    Great thread! I always use the 10% rule. Never go more than that in diameter without adding power AND beefing up axles, drive lines etc.
     
  18. Little Dumper

    Little Dumper Member

    So what you are saying is, the guys that are lucky enough to have an overdrive trans in their mini's are getting worse gas mileage on the highway that the guys with 4sp trannies?

    I have been doing a ton of reading on here and have yet to find someone with a 5sp saying that they get better mileage by driving around in 4th gear.

    One thing you have to remember with going to a bigger tire is that the factory recomended tire pressures are totaly out the door now, you need to run the pressure that best suits the load. Regardless though, if you run the tires at the max pressure rating (45psi if that is what it is) then you will totaly negate the added rolling resistance. It will only give you a bit more dynamic gearing much like adding an overdrive.

    Even with no change to mileage or power it would be nice to actually use 1st gear while driving in everyday traffic. After a test drive in a Carry a little while back I can see why alot of you will start off in 2nd gear. 1st is for stump-pulling.



    Jon.
     
  19. MiniBrutes

    MiniBrutes Gold Supporting Member

    User guide says 1st gear to 20KMH, 2nd to 40, 3rd to 60kmh and 4th over.

    This is for acceleration. Once at cruise, shift up a gear.

    (Want to cruise at 50KMh? 1 to 20, 2 to 40, 3 to 50, 4-cruise at 50. )

    I used 1st gear every day. It is there to use, not decoration. But starting in 2nd, you are simply harder on your truck / clutch etc. Stump pulling is EL for the 5 speeds and 4low on the 4 speeds.

    5 speed truck will not get you any better fuel economy from my experience.

    Use your 1st gear
     
  20. fupabox

    fupabox Active Member

    Even with my bigger tires 1st is only used with a load or steep hill..the biggest advantages to larger tires are availability,slightly lower rpm and noise,and ride..stock 12s don't like potholes very much
     

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