What tires should i get
Thread Starter
Heel & Toe
Joined: Apr 2014
Posts: 24
Likes: 0
What tires should i get
Hey so I have a 1976 c3 454 big block that's been rebuilt so probably a little larger. When I'm cruising down the highway at 60 mph - ish i'm at 3k rpm. I feel as though this is slightly too high because the engine is roaring and in town i only ever keep it at 1700ish. Should I upsize my tires to reach a target of about 2700 rpm? Sometimes traffic runs at 70-75 mph and i'm having to push the engine in the 3.5k and its really roaring and I feel like I'm eating more gas than I need to. There seems to be plenty space left and could fit a tire considerably larger.
Question: What will this affect?
Is this beneficial?
Is it already good the way it is?
Question: What will this affect?
Is this beneficial?
Is it already good the way it is?
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
Hey so I have a 1976 c3 454 big block that's been rebuilt so probably a little larger. When I'm cruising down the highway at 60 mph - ish i'm at 3k rpm. I feel as though this is slightly too high because the engine is roaring and in town i only ever keep it at 1700ish. Should I upsize my tires to reach a target of about 2700 rpm? Sometimes traffic runs at 70-75 mph and i'm having to push the engine in the 3.5k and its really roaring and I feel like I'm eating more gas than I need to. There seems to be plenty space left and could fit a tire considerably larger.
Question: What will this affect?
Is this beneficial?
Is it already good the way it is?
Question: What will this affect?
Is this beneficial?
Is it already good the way it is?
Unless you want to go larger rims that is what to expect.
Good luck.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
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Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Cruise RPM all comes down to your final drive ratio (FDR). Assuming 27" tires, if you're turning ~3000 at 60 and have a 1:1 top gear, you apparently have a 4:11 out back. If you want to get that RPM down below 2700 it's time to consider changing the rear ratio out to a 3.55:1 (my personal favorite), or if ~2500 RPM is more to your liking perhaps a 3.36:1.
Drifting
Joined: Apr 2005
Posts: 1,918
Likes: 451
From: Central NJ
Tires wont make much difference.
If you want to cruise 70-75 mph and few hundred rpm's under 3K you are looking at 3:06 gears.
Your BBC probably likes it lower in the rpm range anyways.
I came up with the 3:06's using this:
http://www.wallaceracing.com/gear-speed.php
If you want to cruise 70-75 mph and few hundred rpm's under 3K you are looking at 3:06 gears.
Your BBC probably likes it lower in the rpm range anyways.
I came up with the 3:06's using this:
http://www.wallaceracing.com/gear-speed.php
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Well theirs two questions you have to ask yourself.
1) what speed do you cruise at (truthfully)
2) what rpm do like your engine running at?
I liked my 427 BB at 2800 rpm at 70mph. A 3:08 rear got me close.
1) what speed do you cruise at (truthfully)
2) what rpm do like your engine running at?
I liked my 427 BB at 2800 rpm at 70mph. A 3:08 rear got me close.
Thread Starter
Heel & Toe
Joined: Apr 2014
Posts: 24
Likes: 0
My current rear tires are 255 60 15 so i think upping it to 275 60 15 will give about
275/255 = 1.078 = 8% more diameter which will reduce to if my math is correct ( 3000/108 ) * 100 = 2777
I think that's just enough for me to be comfortable in.
275/255 = 1.078 = 8% more diameter which will reduce to if my math is correct ( 3000/108 ) * 100 = 2777
I think that's just enough for me to be comfortable in.
Drifting
Joined: Apr 2005
Posts: 1,918
Likes: 451
From: Central NJ
Post up your results after you get the tires.
Melting Slicks
Joined: Jun 2006
Posts: 2,071
Likes: 147
From: S Nevada
There are calculators online, but unless I missed it, you never mentioned what transmission is installed. 1 of the easiest ways to determine how fast you are going is a gps. Today's handheld units are extremely accurate. If you don't own 1, I'm sure someone you know does. You can test your speedometer accuracy and see if you even need a change. The speedometer gears in a Muncie transmission are color coded for identification, probably the same for a turbo 400.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Given that you're still contemplating 275s, I'll share that the reason I expressed a vote against doing so is that putting that tire on an 8" rim will necessarily result in reduced sidewall stability and noticeably affect your car's handling characteristics. Not saying that you can't do it, just that IMCO you'll be better off if you don't.
In any event, I'd verify your speedo before taking any drastic measures...
Last edited by TheSkunkWorks; Jul 7, 2014 at 03:15 PM.