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GT40 Tech - Chassis,Brakes,Tires,&Wheels Chassis and Handling.

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Old 6th March 2018, 09:02 PM   #1
70gsconvt
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Rear tire size question and 2"/4" flares......

I was looking at RCR's web site and saw that you can order your body with no flares, 2" flares, or 4" flares.

It seems that, if going with 15" wheels, the front tire size is pretty fixed at a 225 wide tire. I was just wondering what the different tire sizes that'll fit with the stock body and the two flares.

It seems that Coker is one of the only choices to get the old school wide tires. I'm guessing RCR can help source them from somewhere also for buyers.
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Old 6th March 2018, 09:34 PM   #2
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Re: Rear tire size question and 2"/4" flares......

Try avon tires...
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Old 6th March 2018, 10:06 PM   #3
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Re: Rear tire size question and 2"/4" flares......

Well I'll be, there they are. Avon tires at Frisby Performance Tire north of Chicago. Thanks.

Now just gotta see if the $1000 for flares is money well spent.
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Old 7th March 2018, 11:20 AM   #4
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Re: Rear tire size question and 2"/4" flares......

Hey Phillip,
If you go 15" or 17" you're pretty much limited to 24.5" overall diameter front tire (24.7" if you're lucky), with the RCR. Can't speak for other makes...

That usually corresponds to a 205/60-15 Avon CR6ZZ Radial or a 225/50-17 tire for most applications.

If you go Avons, budget for rear tires (~$500 each) every 6-10k miles but well worth it. I think the ride quality and track performance is the best that you can get out of a 15 incher.
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Old 7th March 2018, 07:50 PM   #5
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Re: Rear tire size question and 2"/4" flares......

You can get BF Goodrich in the typical GT40 front and rear sizes.....225 and 295. They're fine for the street but not track. If you have a street set of tires/wheels and also a track set then the Goodrichs can be economical rubber for street driving.
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Old 7th March 2018, 07:56 PM   #6
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Re: Rear tire size question and 2"/4" flares......

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Originally Posted by Cliffbeer2 View Post
You can get BF Goodrich in the typical GT40 front and rear sizes.....225 and 295. They're fine for the street but not track.
No, they are NOT fine! The TAs only work on heavier cars like 60's muscle cars. On a 2400# car they are hockey pucks. If you are spending the cash for a GT40 go all the way and get some real tires, the Avons. Of course if you don't value your ass, then by all means do the Goodrich's.

It never fails to amuse me that guys will spend thousands for an extra 50 HP, but not an extra $1000 to be able to actually USE the HP!!!!
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Old 7th March 2018, 09:20 PM   #7
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Thumbs down Re: Rear tire size question and 2"/4" flares......

I'm with Rick Muck- Mark on this one.

BFG TA radials are harder than a hockey puck! I tried to use them on a 67 Mustang and a S 10 truck. In a light rain I would slide through traffic lights.
Bad tires. Bad

Great looking tire and I see a lot of cars on BJ with them. They must not drive their cars.

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Old 7th March 2018, 10:37 PM   #8
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Re: Rear tire size question and 2"/4" flares......

Don't worry, I would never consider "regular" street tires. The Avon's are $$$, but if I'm spending $70-80K, I'm not gonna scrimp on the tires.

I'm still wondering what size tires go on the rear with and without the flares. Is it 295 with no flares, 315 with the 2" flare and 345's with the 4" flare??
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Old 8th March 2018, 08:36 AM   #9
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Smile Re: Rear tire size question and 2"/4" flares......

I have 2" flare with 315 and they look correct
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Old 8th March 2018, 03:27 PM   #10
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Re: Rear tire size question and 2"/4" flares......

Tyre/wheel sizes all differ from what offset you will run, which uprights, suspension arms, which chassis etc. I have 295 avons on one MK2 which I have shortened the initial track to squeeze my tyres inside the arches. On my Mk1 with 2" arches I have same 295s, and it works ok with ally uprights on these Southern GTs. All 6 peg knock on one piece rims RBM/Halibrands. I would measure up everything and see what wheels will fit. For sure 4" Gulf arches, approx 80" across the arches will need some wider wheels, like 14" I'd recon. But it all depends on offset and uprights setup.

Link to measuring the rims/ offset etc
Alloy Wheel Technical - Image Wheels

Good luck
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Old 9th March 2018, 02:01 AM   #11
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Re: Rear tire size question and 2"/4" flares......

Same results as Dwight with the 315's.

My spare set of 315/30-17s rear wheels/tires fit in a +2" RCR rear hip with no issues. You'll need to lower the suspension a bit compared to the 295/50-15 Avons due to the smaller overall diameter of the 17's. I think you've already seen the thread and pics on my For Sale Ad...
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Old 22nd March 2018, 03:11 PM   #12
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Re: Rear tire size question and 2"/4" flares......

Quote:
Originally Posted by Mark IV View Post
No, they are NOT fine! The TAs only work on heavier cars like 60's muscle cars. On a 2400# car they are hockey pucks. If you are spending the cash for a GT40 go all the way and get some real tires, the Avons. Of course if you don't value your ass, then by all means do the Goodrich's.

It never fails to amuse me that guys will spend thousands for an extra 50 HP, but not an extra $1000 to be able to actually USE the HP!!!!
No, Rick, they are completely fine for street driving. And no, it's not a matter of not caring or being thoughtless. On the contrary.

And no, you shouldn't "USE the HP!!!!" on the street. That's dangerous to you, and more importantly others on the street.
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Old 22nd March 2018, 07:48 PM   #13
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Re: Rear tire size question and 2"/4" flares......

Quote:
Originally Posted by Cliffbeer2 View Post
No, Rick, they are completely fine for street driving. And no, it's not a matter of not caring or being thoughtless. On the contrary.

And no, you shouldn't "USE the HP!!!!" on the street. That's dangerous to you, and more importantly others on the street.
And so when you get to the "place" you can use your power, what do you do then? Jack it up and change tires? I stand by my statement that BFG TAs are not for a car under 32-3400#

And if you are not going to "use the power" why do you have it? Like you only carry a pistol to "look good", you would never use it?
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Old 23rd March 2018, 05:08 AM   #14
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Re: Rear tire size question and 2"/4" flares......

Fight nice guys, fight nice.
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Old 23rd March 2018, 06:50 AM   #15
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Re: Rear tire size question and 2"/4" flares......

Quote:
Originally Posted by 70gsconvt View Post
Fight nice guys, fight nice.
Not a fight, a difference of opinion! I respect Cliff and his opinion.....it's just that mine is correct!!!
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Old 23rd March 2018, 11:47 AM   #16
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Re: Rear tire size question and 2"/4" flares......

Are you my wife in disguise????
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Old 23rd March 2018, 02:03 PM   #17
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Re: Rear tire size question and 2"/4" flares......

I have a CAV GT40 MKI Std body and I'm running AVONs and love them!

Frt: 225/60R/15
Rear: 295/50R/15

I was running Mickey Thompson Radials prior to the AVONs and had Goodyear Billboards on my last Cobra and neither can compare to these AVONs. They ride and handle outstanding and have great traction also. A lot of the GT40s vintage racing are using AVONs.

Vid2 2 11 17 - YouTube
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Old 23rd March 2018, 05:55 PM   #18
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Re: Rear tire size question and 2"/4" flares......

I have avons...a friend of mine runs bfg's with 400 + hp in his gt40.. He said he has no issues.. I went with the avons for the higher speed rating (don't tell my wife) of course i always obey the law
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Old 23rd March 2018, 08:06 PM   #19
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Re: Rear tire size question and 2"/4" flares......

Quote:
Originally Posted by gsharapa View Post
I have a CAV GT40 MKI Std body and I'm running AVONs and love them!

Frt: 225/60R/15
Rear: 295/50R/15

I was running Mickey Thompson Radials prior to the AVONs and had Goodyear Billboards on my last Cobra and neither can compare to these AVONs. They ride and handle outstanding and have great traction also. A lot of the GT40s vintage racing are using AVONs.

Vid2 2 11 17 - YouTube
Awesome looking car Gary. Does your car have any rear quarter extensions? Or does the 295 tire fit in the stock fender well? That may be wide enough for me. But I'd have to see an ass end shot of the car to be sure.

And Walter, I'm glad to see you're a "Keeper of the Speed".
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Old 23rd March 2018, 10:26 PM   #20
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Re: Rear tire size question and 2"/4" flares......

FWIW, I don't see why you should cheap out on tires after investing all the time and money into a GT-40, only to lose control of the car or lock up wheels prematurely due to traction/instability issues. The Avons work great all around on the track and on the street.

A different perspective for you to help you decide. The following video was taken by MHNCO as he followed me down the highway last fall. The car has the +2" rear fender with the standard Avon CR6ZZ 295/50R-15 rear and 225/60R-15 fronts.

At the time this video was taken my rear track is 71 3/4" (camber @ -1.1) and front track is 69 3/8" (camber @ -1.8). There is no tire rub at these settings.

MHNCO and Cobrajet
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