I need to buy new tires for my 1985 k5 blazer. It's sittin on old 31s right now that need replacing. should i go up to 33s and if i do any suggestions on what to get. Also my dad dad was telling me if i went up on size the gear ratio would change making the truck more sluggish in low end. How would i compensate the gear ratio to make up for the bigger tires? Any help would be nice.

 

you would have to change the gears inside your axles. probably upwards of $1000 or more if you bring it to a shop. probably cheaper to swap axles if you can. i had a 84 k5 blazer that had 273 gears and 35 inch tires when i got it. i bought a set of 373 axles for it and it really helped.

so technically you can put 33s on it. also if the truck is stock those tires are probably going to rub. another k5 i had had 33s and a 2inch body lift and the tires would rub on tight turns

 

No its not stock. Its already got a four inch lift on, so its got plenty of room in it. and i think it was like 310 ratio with the 31s. I was told 373 would be good with the 33 in. like you were saying, I just didnt know how i would go about that. And i can do the work myself, but a little more HP wouldnt hurt either haha.

 

i got two trucks with 373s and 33 inch tires and they work just fine. installing gears is a pretty complicated if youve never done it before. have someone help thats done it before. they have to be set up a very specific way. thats why i just swapped axles. its actually faster and cheaper to do it that way.

 

Put the bigger tires on, if nothing brakes your good, if it does then change it. If your not beating on it to hard, you should be ok. Just my opinion

 

I wouldn't mind either way I did it. I'm trying to learn all the tricks of the trade and after summer ill have college automotive shop to work out of. But nothin beats learnin from your garage

 

My '74 K5 has 3.73's & 33x12.5 MT's and it cruises down the highway just fine. I'm not sure I would want to have an over drive transmission with 3.73's & 33's though.

 

ya. if u dont mind running in higher rpms do 3:73 with 33s. but if u wanna keep the rpms down and mpgs up go with 4:56s and 33s, if u have o/d. ul keep the mpgs up, the rpms down, the low end power and all around good quality or ur truck. not too much wear and tear and heating of the transmission either. but if u dont have o/d then id do what everyone else is saying. personal opinion, with 33s id go at least 4:10. also, what motor and tranny do u have?

 

To Duxtoys I have 305 5:0 motor and the r4700 transmission and if it helps I can find out the transfer case to I just can't remember off the top of my head right now

 

then u have od and plenty of power to turn 4:56 with 33s and keep ur rpms down. but if u have acess to 3:73 easier then go with those. theyd work too. but in my opinion 4:56 would be way better. save u a lot of headache later. if ur gonna do sumthing like that, do it rite the first time.....thats my motto.