Tire size help - best fit for 302/nv3550/3.50

[Millercorey]

Title pretty much says it. Prior owner put 33s on and they look pretty much new, but I know there's a science/art to pairing drivetrain components. This will be 99.999% street cruiser. Original 302 was just rebuilt, I chose to retain the original 2bbl carb, and we just finished up dropping the Nv3550 in there. Has original 3.50 gear ratio.

I like the look of the rig with the tires and the 2" BL, but I think it would be more suited to my driving with smaller tires. The tires look pretty much new, so if going down a few tire sizes won't make much difference I'd probably just keep them on their. If the smaller tires improve the overall driving experience, then I'd be more interested in swapping them out.

Thoughts?

 

[661buster1963]

Most folks with od transmissions have regeared away from 3.50 be able to use od. The 3.50 gearset is already a highway friendly gearset with a highway friendly transmission and as much as I love the 289/302 the torque curve is pretty high rpm range relatiely speaking. If 3.50 is the gear set you want, a smaller tire (the smaller the better) will put some pep in the step of your ride, otherwise 4.56, 4.88 or at least 4.11 will help run the 33's efficiently. At freeway speeds in od today your engine is likely below 2000 rpm. Just my 2 cents

 

[DirtDonk]

Agree. I think you're looking at a more original 28-ish inch size tire or no more than 31's for sure.
Luckily some tires are smaller than their number suggest, but that also means you should double check your current 33's with a tape measure top to bottom while the vehicle sits on the ground.
My "31" inch BFG's for instance are 29.5" tall on the ground. That's the effective, or rolling diameter of the tire. Your 33's could be anywhere from 31 to 32.5 inches or so, depending on the brand and model.

The only way to make that 3.50 and 33" tire combination work with an overdrive transmission would be maybe a full EFI setup with an automatic trans.
You are driving it now, correct? What are your feelings on how well it takes off from a stop? What about putting it into 5th gear? Can you cruise along now at 65mph in overdrive? How far do you have to downshift to go up a hill?

Your satisfaction with how it runs now will dictate how far you have to go to get where you want to be. If you're happy, then you can leave it. If you're thinking it needs a little bit, go with 31's. If it's a real dog in most conditions, go down to a 28 or a 235/70/15 or something similar.
Will never look as cool with the tiny tires as it does with the larger ones of course, but looks and performance are not always compatible.

Good luck.

Paul

 

[Millercorey]

Haven't driven it much since we finished the engine and tranny. Definitely think it feels a little underpowered or sluggish, but again it's a brick and not a sports car so I try to temper my expectations.

Still have to finalize the exhaust install, put in the new 23 gallon tank, redo Floorplan, Yada Yada over the winter, so I don't plan on it driving for another few months. Didn't plan on changing the gearing or getting new tires anytime soon, but obviously I want to enjoy the driving experience.

 

[Broncobowsher]

For the gearing, about a 27" tire.

If you want a taller tire, get some gears. It will fix the under powered feel. Gears will need to match tire size.

 

[Millercorey]

Also kind of a dumb question, but keeping the 3.50 and going to a smaller size tire will be more fuel efficient than going up to 4.11, right? Obviously none of us are too concerned with mpg, but if I can not spend the money on switching the gear ratio and it's effectively a positive in the fuel dept, then that seems like a good thing if this is mostly just a cruiser.

 

[sykanr0ng]

It will look strange with 2 inch body lift (suspension lift?) and tiny little tires though.

 

[blubuckaroo]

Well Millercorey, if you're planning on keeping the 3.50 gears, there is still some good news. The NV3550 is still the perfect tranny for you.

The NV3550 has a way lower 1st and 2nd gear than either a factory three speed or the C4. You're going to notice better performance in those gears than you did before. Even with the 3.50 gears.

Stock three speed has 2.99 1st and 1.77 2nd gear.
C4 has 2.46 1st and 1.46 2nd.
NV3550 has 4.01 1st and 2.32 2nd.

I do agree that someday you will most likely go to lower differential gears, but in the mean time, you can still enjoy the tranny as a big improvement in drivability over what you had before.

Here's a good calculator to help you to decide.
https://www.yukongear.com/calc_rpm.aspx

I think you may even be able to get by with 30" tires. That and the .78 overdrive of the NV3550 would put the RPM just over 1800 @ 60 MPH.
That's right in the maximum torque range for a stock 302.
Sure, a bit more RPM might be better, but you'll need to try it out yourself.
Keep us posted!