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86 brat with 3" lift over size tires questions


nicksubaru
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So ive been trying and trying to figure out what would be the best tire size with what i have to work with. Im looking for an all terrain tire. I have a set of m/t Toyota 6-lug 15x8" wheels and a 3" lift on my brat. So far i know i dont want to go over 27" tire for drivetrain. As of now i have the stock ea81 in it. But i have an ej22 and an ea82 5 speed dual range that will go in it eventually. Ideas? Im in California if that makes a difference

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I would look up the peek torque rpm for your engine and your peek hp rpms that should give you a good idea were your powerband is so if peek torque is oh say 3200 rpm and peek hp is im guessing 3800 then your powerband starts somewere around 3k and starts to fall off around 3800 and 4k so you want to be in that range at highway speeds if you cruze at 65 them your rpms should be close to peek torque rpms thats were your engine is most efficiant you can then look up a tire/rpm calculator and get the rpms for each tire size your looking at i use the 1:1 final drive just to make life easyer but the ea82 duel range dosent run a 1:1 gear 4th and 5th gears are both overdriven so that will through you off a bit and also not good for us with limited gear ratio selections and big tires as it lowers the rpms to much to keep the engine in its powerband thats the right way to figure out what tire size.to run but there is a less mathie way just start with small tires and if you think the rig has more in it move up a size see how it feels keep doing that till you find something your happy with and role with it i just sold my parts car it has 195/65/15 on it and i couldent tell the diffe4ance betweeen them and stock the 225/70/15s did bog me down a bit the 235/75/15s are hell on a stock motor but still functional there isent alot of differance between a ea81 and a ea82 in the torque department so you should be able to run the same size as your loyale the lighter ea81 should make up for the little bit of torque differances

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My loyale still has the 13" wheels on it. This will be my first 6 lug swap to 15" wheels on any older suba. So i might just go with the 225/70r15. I cant just keep buying tires after tires. So once i buy them ill be stuck with them for a while. That's why i posted on here my questions lol

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It realy comes down to what you can live with if i do some mathie like type.stuff your original tire size is about 22" say you run a 27" tall tire thats ruffly a 4.5 % increse in tire size a 30" tire is ruffly 36% increse in tire size so my thinking is 36% less avaliable torque to the wheels and thats gona hurt your hyway speeds 4.5% dosent sound like much it shouldent hurt your drivability to much so its up to you what is a aceptable loss of power and what looks or works for you there isent a real clear cut answer by my best ruff guesstamating i basicly base everything off of tbe tire size persentage so basicly if you incress your tire size by 10% i would.guess a 10% powerloss and a 10% drop in mileage 10% loss of.breaking power 10% incress in rotating mass at the wheels and 10% drop in rpms that is.bassed on absalutly nothing but my wacked out thinking its just a easy way of guesstemating tire size so if you can figure out were your powerband is and your cruz rpms with your cerant set up you can use the tire size persentage # and calulate your rpm drop and if your rpms are still in your powerband your good if your rpms.go to low at cruzing speed your gona lug the engine and wont be able to hold speed with out downnshifting

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