Tire size question

Omathisen · #1 (**permalink**) 12-14-2009, 07:23 PM

I have been looking for new tires for my 16 inch wheels for some time, but got side-tracked with work. Meanwhile, I did get Goodyears 245/50ZR16 for the front and have new Goodrich 295/50R16s (S rated are OK for street, also considering how light the car is) for the rear. The tire diameter is 27.6. My question is will they fit?
I am also considering Goodyear rain or intermediate tires that translate from inches to metric to 305/38-16 or 305/48-16 with diameters of 25.1 and 26.3.
Mickey Thompson also has what they call an ET street radial tire - 295/50R16 that they say is a soft compound for superior traction on the strip, but also for excellent ride on the street. The diameter is 27.7.
Any opinions.
My present and old rears are Goodrich transam rain tires 275/50R16 with a 26.8 diameter. They have lasted for 10 years and 7,000 miles and still look fine.
OMathisen
427 ERA (#425 SII)

RICK LAKE · #2 (**permalink**) 12-15-2009, 04:17 AM

Omathisen Era fixed my body for clearance on 335/35R17" Pilots for the car. 245/40R17" in the fronts. I have chassis # 428. Springs and shocks where changed to handle the better performance these tires give over the 15" BFG I started with. I have no rubbing issues with the car. I do sit low to the ground. 4.1/2" is clearance at each corner of the frame behind the front tires and ahead of the rear ones. As long has there is no excessive play in the front rotor bearings or A arms bushings. I get no rub. The same applys for the rearend and the out board housing have little hub play. I do recomend many coats of undercoating to portect the paint from getting stars in it. Snake skin works good too. about 3/8" thick. Rick L.

strictlypersonl · #3 (**permalink**) 12-15-2009, 04:31 AM

The 245-50-16 size should fit nicely in the front, but there is a high probability that the 295-50-16 size will rub in the back (both on the splash panel behind the seats and the diagonal tube at the top). The diameter is the critical dimension.

Omathisen · #4 (**permalink**) 12-15-2009, 07:15 PM

Hi,
Thanks. However, I am surprised since the diameter of the 275/50 is 26.8 inches and the 295/50 is 27.6 - or a matter of only 0.8 inches - and the wheel wells seem spacious to me.
Do you see any problems running a slightly different size in the back, that is a 275 45 (Hoosier) or a 265 45? If I go to 45 in the back should I also run 45 in the front (where I have 245/50).
The Goodyear rain tires are 305/38 - diameter 23.1 which is much smaller - and a section width of 11.5, and 305/46 with a 26.3 inch diameter, but with a 14.1-inch section width and a thread width of 12.4.
I want to the car to perform well; looks are secondary.
I am trying to do this while keeping my 16 inch wheels which I happen to like.
OMathisen

strictlypersonl · #5 (**permalink**) 12-16-2009, 05:38 AM

The 295/50-15 tires that we recommend are theoretically 26.6" in diameter, and they were pretty tight on the early cars. I think we made some changes around chassis 550 to increase the clearance, especially for wider tires.

But, there was some variation between cars, so I would advise you to put the car at ride height and check your current clearance, taking into account that the tire might travel 3" up and 1/2" forward.

Within your choices, I think that the 305/46 might be the best fit. But you didn't hear it from me.

Omathisen · #6 (**permalink**) 12-17-2009, 08:41 AM

Thanks.
But the plot may be thickening again. The 305 46 tires have a diameter of 26.3 and a tread with of 12.4, which should be fine, but a section width of 14.2, according to the Goodyear specs. Before I proceed, is there enough room for 14.2 inches?
OMathisen

strictlypersonl · #7 (**permalink**) 12-17-2009, 11:22 AM

I don't understand how those tires are sized. 335/35-17 tires (link here) on a 12" rim have 12.6" tread width.

At any rate, the above 17" tires will fit, although the backspacing requirements are different. I would have to know your wheel offsets to give you a more educated guess. Definitely won't fit an undercar exhaust.

Omathisen · #8 (**permalink**) 12-17-2009, 06:56 PM

Hi,
According to Goodyear these are production and GT rain tires. The dimensions given are 27.0x12.0-16 which translates into 305-46-16. According to the specs given, the recommended rim width is 12.0, overall diameter 26.3, section width 14.2, tread width 12.4 and weight 22.5.
They are called G-18 Eagle and F-1 Eagle and cost $336 each and are in Goodyear's catalog on a page designated Eagle Sports Car Special - Rain.
They are available for full wet conditions or intermediate, which was my plan.
All I know. But I will call them and verify specs.
OMathisen

Omathisen · #9 (**permalink**) 12-26-2009, 02:59 PM

Decided to go with the 275-45 Hoosiers in the back and the Goodyear Eagle 245-50 in the front. Will see how that works. Alternatively, I will give up on my 16 inch rims, and go to 17.
Also enjoyed those Christmas pictures. Very tempting to get another one. . .
OMathisen

Cobra 29 · #10 (**permalink**) 12-26-2009, 04:35 PM

I also have 16" rims front and rear. The only WIDE rears that I have found in a performance tire are the Goodyear Trans Am Rain tires. The size is 27 by 12 by 16. My classis number is ERA454.

Omathisen · #11 (**permalink**) 12-30-2009, 06:24 PM

Hi,
Do you have the Goodyears on the car? I am asking because they 27-12-16"should" fit, but I was concerned with the listed section width at 14.2 inches.
OMathisen

Cobra 29 · #12 (**permalink**) 01-02-2010, 07:52 PM

Wheel backspacing is critical. There is only 3/4 to 1" space betwwen the front inside edge of the tire and the area of the car at the back of the seat area. I would post pictures if I knew how.