9D1BURD

Okay, i have had the polished formula wheels on my bird for some time now.

Someone just asked me how far off my speedo is. I assume it is off some, has anybody else done this who might know?

Am i going faster or slower than it says?

I went from the stock size, to a 16x8 inch wheel with 245/50/16


Any ideas?

pontiacguy1

245-50-R16 tires were the factory size tires that were issued on most third gen cars with 16 inch wheels from the factory. I have a 1992 Firebird, and I put a set of 1985 16X8 inch Trans Am wheels with the same size tires that you have. My speedometer isn't off any at all. Yours could have been changed by someone sometime, though, so verify it by pacing someone at 60 MPH that has a car whose speedo you know is accurate.

My car came with 215-65-R15 tires, which are the same height as the 245-50s when you consider the 1 inch difference in rim size.

Dale

iTrader: (12)

Great, now I know what size I will need to run.

devianb

My speedo is off by a couple of mph. No big deal. I don't even look at the speedometer much. I know how fast I am going without even looking.

zer0321

on my 92 camaro, I originally had 215-65-r15 and I'm now running 245-50-r16, and it seems the speedometer is dead on accurate as far as I can tell (tested it with a friend's car, etc...)

91FIREBIRDGT

I've gone with 18" wheels with 235/45/ZR18's on them and My speedo is dead on accurate. Tested it with one of the CHP things.

KED85

Tested it with one of the CHP things

I assume he then chased you to give you your certificate of authenticity and it cost you $300, too!

Sorry!

Hey Pontiacguy 1
Those tires.
Are they the same size all around, as in how is the front fenderwell interference? Any problems?
I keep cheating with 215-65 up front as I know (swap meets) tires are dirt cheap ($15 usually).
I use slightly wider in the rear (245-60). This last set or "new" rear tires I scored were $20 pair with a great amount of tread.
With 5 cars, brand new tires I really want, kinda take a back seat.

PS THAT STATEMENT also depends on my driving and the roads. It don't rain in California and I can almost drive on bald tires some days out here. Until after Thanksgiving, then it's time to find great tires for winter.
Long hauls, I rent a new car, it's cheaper

89V6FBIRD

Yeah, try driving in the rain with bald tires. It's a fun experience. Goin out to find tires today...

Keoki_Firebird89

yea i've had that experiance recently...
so recently its the reason why i have to fix my car now...
otherwise... in a parking lot... OH BOY!!!

91FIREBIRDGT

by the CHP things I meant the un-maned things that show you what speed ur going when you pass it.

KED85

by the CHP things I meant the un-maned things that show you what speed ur going when you pass it.

I was kidding! So ya know!
Ever hear about the people who stole one of those things!
Eventually found on a road with LOTS OF BLACK TIRE RUBBER AT A STARTING LINE 1/4 Mile Away!

I just examined my rear tires. I got til Summer or later until I install my $20 pair of tires.
It's front ones I mainly worry about!

pontiacguy1

To answer your question: I have Kuhmo Ecsta Supra tires on there. The size is 245-50-R16 all the way around. I bought three of them used with 5K miles on them on this site from a guy who had wrecked his car. I got one brand new one, and ended up with an entire set for about $265 or so. They don't give me any trouble whatsoever on turns or with rubbing or anything. My car is at stock height. Those are the factory size offerings on those rims, so unless you lowered your car, have large offsets in your rims or something like that, they should work fine on any 3rd gen.

I used to have 265-50-R15 tires on 9 inch rims on there, and they rubbed the fenders terribly if you turned really sharp. The rear ones would also hit the fender if you put a bunch of weight in the car. I got rid of those, though. I like the factory size and look better now. I can't rotate them without breaking them off the rims, though. The 85-88 Trans-Am 16 inch wheels have different offsets for the front and the rear, and the tires are directional.

KED85

I used to have 265-50-R15 tires on 9 inch rims on there, and they rubbed the fenders terribly if you turned really sharp. The rear ones would also hit the fender if you put a bunch of weight in the car.

Aftermarket wheels?

I am kinda aware of the factory wheel offerings of the mid 80 years. I knew they were unique.

Seems I could safely go to 245-60-15's all around & it should work well. I have 245-60's in rear on the factory pinwheel design. No problems at all. I may try that after I get front end back to factory issued day one tightness.

Funny I pass by the factory where my wheels were made almost every day now (Superior Industries in Van Nuys).


THANKS FOR THE RESPONSE!

pontiacguy1

The 9 inch rims were ultras with a funny kind of backspacing. They were 9 or either 9.5 inch width, I don't remember which. They looked really good on the car, but I got really annoyed with the rubbing, mainly when turning really sharp to get into a parking space or something like that. I also decided to go with a more factory like appearance. That is why I went with the 16 inch TA wheels. I didn't go with the formula wheels like most do, just because I like the TA wheel looks just a little bit more. Personal preference only.