Tire size impact on gearing

[shadango]

I am sort of twitting over what size tires to get for the rear of my ebody fish.

Currently have 235/6015....size would be 26" new....as worn, they are like 25.5 or so.

Considering 275/60/15 so I can get a more beefy look to fill my wheel well...the car is lifted in the back some and will have clearance that way. That tire would be about 28" tall.

But I recently changed from 2.76 gears to 3.54s.

I know going to a bigger tire will in effect take me backwards some.

Looks like going to a 275 would give me an effective rear gear of 3.31

Going with a 255 would give me an effective rear gear of 3.43 but they are only 1/2" bigger sidewall wise and not as wide in the tread.

With the current 235s, RPMs are about 3k at 65 mph give or take. 9Used to be like 2200 RPMs with the 2.76 gears installed and the 235 tires.

According to an online calculator , I would be spinning at 2800 rpms at 65 with the 275 tires and the 3.54 gears.

My question is, will I notice a loss of low end power going with the 275s?

Is that 200 RPM critical do you think?

My engine is a tweaked-up 318 with a cam that is strong up top, just OK on the bottom end. 727 tranny.

 

[shadango]

....Buehler?

..........Buehler?

.............Buehler?

....too lame a question I guess? LOL

 

[abodyjoe]

guess it really depends on the tq the motor puts out. i think you'll notice it some but don't think it will totally kill it..

 

[shadango]

SO finally decided to pull the trigger on the 275s....call the Firestone dealer who originally quoted me for them and the 235s.

He calls the main warehouse and .......they are not available.

<sigh>

He is making some calls to see what he can find.....

...........nothing can be easy. :banghead:

 

[1972DusterPaul]

I have 275/60/15s on the back of my Duster and I went with BFG tires.

I would have prefered to go with the Firestone Indy 500s, but ran into the same problem with my local Firestone dealer.

My stock tire set up (14" ralley wheels) are the Firestones, but I could only find 2 tires locally and had to find the other 2 tires out of my state on my own.

So I figured even if I found the Firestone tires what would happen down the road if I needed to replace one or two tires...if they are that hard to come by now.

I have never been impressed with the traction that BFG tires provided, but they seem to be the only game in town when it comes to raised white lettered street tires unless you go with an off brand.

As far as the effect on gearing...use the 275s for SHOW...and buy another set for GO if that's important to you.

I have 3.91 gears so the taller tires will help a bit on those longer drives I do once in a while.

Paul

SO finally decided to pull the trigger on the 275s....call the Firestone dealer who originally quoted me for them and the 235s.

He calls the main warehouse and .......they are not available.

<sigh>

He is making some calls to see what he can find.....

...........nothing can be easy. :banghead: