Pontiac G8 Forum banner

1 - 20 of 30 Posts

·
Registered
Joined
·
923 Posts
Are they a taller/shorter diameter than stock?
 

·
Premium Member
Joined
·
10,244 Posts
Type in your numbers, bud.

http://www.miata.net/garage/tirecalc.html

To make the camaro rims "fit" a g8 (without rubbing), the standard camaro tires are replaced by lower profile tires.

Thus, it's closer to a 19" stock g8 tire, generally speaking.

Plug in your stock numbers. For example, I have 245-45-18's which are still my stock RS-A's on stock rims. Now find what others are wrapping their camaro rims with, 275-30-20's ring a bell, not sure though.

Using that formula... compared to "stock", your aftermarket tire&rim is causing your speedo to be reading 0.7% too fast. thus, when you're going 60 mph according to your speedo, you're really going 59.4mph.


If you chose to run 275-35-20's on the camaro rims (slightly larger sidewall than the 30-series tire) then it goes the other way. Since the overall tire height is higher with that combination, your speedo is now reading 3.4% too slow. Thus, when you're going 60mph according to your speedo, you're really going 62.0mph. Be careful speeding with this size tire... :judge:

Hope this helps. You can use that miata.net calculator for any combination of tires to compare, it's really the best one out there!

--zep
 

·
Registered
Joined
·
1,343 Posts
Zep
Thanks man! I was just trying to figure this out yesterday!
Appreciate it!
 

·
Registered
Joined
·
46 Posts
My 275-35-20's on my Camaro wheels make it about 2 mph slow at 65 by running side by side with my dad (I wanted to test this when I got them). Zep's info appears spot-on.
 

·
Rim and Tire GOD!!!
Joined
·
102 Posts
My 275-35-20's on my Camaro wheels make it about 2 mph slow at 65 by running side by side with my dad (I wanted to test this when I got them). Zep's info appears spot-on.
ofcourse man. Thats why its a wheel/tire calculator. It will never be wrong. It will tell you correct answer no matter what brand, size, width tire/wheel you have.

I like this one too.
http://www.rimsntires.com/rt_specs.jsp
 

·
Registered
Joined
·
46 Posts
I was not doubting it at all. I was just chiming in with my own personal experience.

The MPH difference is minor but something to keep in mind just in case.
 

·
hasa Member
Joined
·
114 Posts
Due to our sue-happy culture, most factory speedos read a little fast anyway (if you found you were going 1mph faster than the speedo said it would be "unsafe", and you could sue the car maker, but the other way around is "safe"), so going to a rear tire 2% larger may actually CORRECT your speedo. That is exactly what I found when I changed the tires/wheels on my S2000. The slightly larger rear tires just about exactly corrected the speedo. I tested it using GPS before and after.
 

·
Registered
Joined
·
95 Posts
Wouldn't replacing the tire pressure sensor when getting the 20" Camaro rims correct the problem?
 

·
Registered
Joined
·
49 Posts

·
Registered
Joined
·
132 Posts
Wouldn't replacing the tire pressure sensor when getting the 20" Camaro rims correct the problem?
I'll bite...why? I'm guessing because the TPMS system maybe measures the RPM of the sensor and gets MPH from that??? That's the only thing I can think of....really not being a jerk, just interested in the thought process
 

·
Registered
Joined
·
923 Posts
I'll bite...why? I'm guessing because the TPMS system maybe measures the RPM of the sensor and gets MPH from that??? That's the only thing I can think of....really not being a jerk, just interested in the thought process
No, the sensors just "sense" pressure, and relay that info to your car. You could build a pressure chamber out of 6" PVC pipe, put all 4 sensors inside, seal it up, and pressurize it to 35psi, put it in your trunk, and everything would be good.


Just bothers me when the OP never returns back to a thread and answers questions or thanks others for helping them.:slap:
 

·
Registered
Joined
·
12 Posts
With 245/35's up front and 275/35's on the rear, and according to my iphone speedometer, I have found it to be only about 2 mph faster @ 75 mph!
 

·
Registered
Joined
·
3,389 Posts
With 245/35's up front and 275/35's on the rear, and according to my iphone speedometer, I have found it to be only about 2 mph faster @ 75 mph!
Overall diameter changes from 26.7" to 27.6" on that size rear tire. Speed difference SHOULD calculate out to 3.3%, or 62MPH at 60MPH actual.
 

·
Registered
Joined
·
1,662 Posts
Nice calclulators! So I could actually run a 225.60.16 tire for winter tires. This would be a little cheaper than buying 18's and maybe open the door to using steel wheels. The only question that just came to mind is will 16" wheels clear the brakes?
 

·
Registered
Joined
·
3,389 Posts
Nice calclulators! So I could actually run a 225.60.16 tire for winter tires. This would be a little cheaper than buying 18's and maybe open the door to using steel wheels. The only question that just came to mind is will 16" wheels clear the brakes?
No, they won't. Smallest you can go is a 17" wheel.

I run a 225/55/17 during winter on 17x8" wheels
 
1 - 20 of 30 Posts
About this Discussion
29 Replies
24 Participants
Trenton Man
Pontiac G8 Forum
A community for Pontiac G8 owners and enthusiasts, for all the information on your Pontiac G8 sedan, G8 GT, G8 V6, and G8 GXP. Discuss performance, tech, engine specs, body kits and more!
Full Forum Listing
Top