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Ideal tire size and gear ratio. What do you think?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by FOURFOURMAG, Mar 16, 2003.

  1. FOURFOURMAG

    FOURFOURMAG Registered Member

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    I am a new blazer owner, I just got a '74. I have a healthy 350, th400, np205, front d60, rear 14 bolt, all of which are going into the blazer. This is going to be a wheeler and summertime cruiser. Will see mud, trails, and maybe some mud drag races plus driving around town and to the trail.

    I cant decide what size tires I want to run, and I need to figure it out so I can order gears. On one hand I want to get some 39.5's or 42's but on the other hand some 37s or 36's might be more practicle. I am going to have stout running gear no matter what tire I choose.

    What do you think is the ideal tires size and what gear ratio would you run with it.

    -Mark
     
  2. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    well i am not sure as I can give you my experience and a friends.....

    I used to have 33's with 3.73's... and a turbo 400 trans... never had a problem with mud or trails.. truck seemed to always have power... but when i went to a smc465 trans and 4.56's I saw a whole new world... i got better gas mileage ( more average city highway ) and TONS OF POWER AND CONTROL!!!!!
    Now i am runnin 40's and i was told 4.56's are good.. truck has been of the road since 1997... /forums/images/graemlins/frown.gif


    a friend of mine has a ford f250 with 44's and 5.13's... he always had the truck go through NJ inspection without a problem.. ( inspection for high rise vehicles ).. with the new lift law he put 38's on, took his body lift off and said the 5.13's were killin him.. so he went with 4.56's and has his power and highway use.....

    well that is my .02
     
  3. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    assuming you're not going to have a doubler or some other gear reduction, for 39.5s or 42s, I'd say 4.88s would prolly make the most sense. I have 4.56s and run 35s on road, 39.5s offroad. At some point i will prolly get an atlas or klune or something to get a good crawl ratio for my bigger meats, but for now 4.56s have served me well. On the other hand, the TH400 doesnt have OD... so the lower gears get, the higher your rpms r gonna be on the highway. <shrug> there is a rpm-tiresize-gear calculator thing somewhere are here that would help a lot...

    j
     
  4. JDBlazer454

    JDBlazer454 1/2 ton status

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    From experience I have run 35's with a 4.10 gear behind a 400 small block with decent power. 38's with 4.10's same motor with lots of power loss. 39.5's with 5.13's behind a big block with lots of luck and was just about perfect power to driveable ratio. 44's with 5.13 behind a big block is fine in 4lo offroading but being such a big tire wasn't very driveable (44's have a mind of their own on pavement). With your setup my suggestion (its just my opinion) 38's are big enough to be wheelable but yet still streetable and comfortable for everyday use and for gearing I have seen 4.56's used with that tire size powered by a small block with good results. Hope this helps.
     

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