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Thread: Tire size

  1. #1
    FEP Member javdog's Avatar
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    Default Tire size

    Hey guys I came across a great deal on 4 new [h=BF Goodrich 245/60/15 would these fit either my 84GT350 or my 86GT? ]2[/h]Thanks for any help.

  2. #2

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    I had 235/60's on ten holes with the 10" spindle. There was less then a fingers width between the tire and strut.

    They should work okay on the rears though.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

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    FEP Super Member erratic50's Avatar
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    I would not go any bigger than a 235/60 on a 15" rim up front. Even those rub slightly due to height.

    They should clear in back. Bear in mind that at 85 with 235/60/15's the car is actually going 92. With a 245 your going around 94-95 when the speedometer says 85.

    Whats humorous to me is how far off an odometer can get in not much time when the tire size vs rear gear vs trans gear is not spot on. A 235 is about 8% more miles traveled than shown on the odometer. That's about 800 miles every 10K, 8000 every 100K. So I guess I'm even closer to 1/2 million miles than I give my car credit for.....

    my experience is gas mileage with mile correction factored in usually goes up a little too if it's highway driven miles. Down slightly if it's city.

    But hey, a 2.73 car with a 2.95:1 1st gear T5 and 245/60's will have a good shot at hitting 60 in 1st.

  4. #4

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    I had a non-h.o. motor and a 3.35 1st gear with 275/60's (slightly over 28" tall). It added nearly a 10% overdrive of I remeber correctly.

    Even still, 35mph in first was all the car wanted, I took it to 40 or 45mph a few times, pretty sure that's what valve float feels like. This was with scrappy non h.o. cam and e6 heads and about 200k miles.

    Shifting to 2nd I could spin half way through (one wheel peel) if I shifted at 35mph and dumped the clutch when I shifted.

    Bet it was pretty funny watching me spin through 1st and half way through second, while still taking about 10 seconds, probably more, to hit 60.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

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    FEP Super Member erratic50's Avatar
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    Lol. Yea, spinning ain't winning.

    I love making the old pushrod V8's run R's. So simple to add the parts needed on the HO cammed cars and they are like a different car from 4500-6250 when done. No reason to shift if you can make it scream..... spintron data is out there if you look for it.

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    FEP Super Member gr79's Avatar
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    My Ranger 2.3/5s 3.45 would spin 275/60/15 in 1st no problem.
    They are huge looking.
    Went with 245/60/15 all around. Perfect Splash type look on 2000 era Ranger chrome 15x7 rims.
    Nice sidewall bulge, wide footprint, wheel well gap. Not too tall, not too short.
    Not happy T/A is only brand made in that size. Overpriced for old school construction..

    Car- 215/60/15 Firestone on turbines. Are close to 79 trx dia. Great all weather bite.
    225/60/15 with front with rack limiters ok. Close to later 220 trx dia.
    Larger makes the car look fat.
    past owned daily driven many memorable times with all
    1967 Mustang 'verti Sports Sprint 289 Holley 4vC4 2.79 lime gold blk vinyl (6/70-4/73) 100k
    1970 VW 113 Beetle modded 1650 5200 2v 4sp Hurst 4.13 grn blk leathette (1973-1977) 200k
    1975 VW 1303 S Beetle LaGrande 1600 EFI 4sp Hurst 3.88 lime grn tan cloth (1977-1980) 90k
    1985 LTD LX 5.0 CFI HO AOD 3.27 gray gray (1987-1990) 75k
    1986 Ranger XL 2wd 7' bed 114 wb 2.3 EFI 5 sp 3.45 gray burgundy cloth (1990-1994) 180k
    current owned now weekly driven totally enjoyed
    1979 Mustang Cobra 61R 2.3T Holley 2305 2v '92 T5 Hurst 3.45 black orange decals (7/80- )
    1993 Ranger XLT R103 2wd 7' bed 114 wb 2.3 EFI 5sp Hurst 3.45 calypso green gray (3/94- )

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    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by javdog View Post
    Hey guys I came across a great deal on 4 new [h=BF Goodrich 245/60/15 would these fit either my 84GT350 or my 86GT? ]2[/h]Thanks for any help.
    I did a lot of work when I looked at fitting up a four wheel drive system to my Fox.

    Fords blue print for the 79-90 Mustang and 79-90 Capri were 236/60 15 only if the 91-93 5.0 front gaurds and Inner guards are used. See all the evdience below. That's 26.1 inches unloaded or 663 mm maximum, and 245/60 15's are too big at 26.575" or 675 mm. The early cars, its about 25.3 inches or 643 mm max wheel diameter, with 230/55 390's at the front. The trial fitted 26.1" 663 mm tall 235/60 15 Pirellis weren't proceded with, so the early cars won't take them unless you do tin work at the front.

    Now, you can fit them, but it'll require 1991-1993 5.0 guards, and the removal of the Poly Ethylene inner wheel house at the front.

    At the back, BFG 295/50 15's fit at the back if dilligent work is done with air assist springs. HissinCobra

    I think things top out at 27.6 inches tall or 701 mm with the last Fox birds and thats up to 295/50 16's, or 27.6".

    15's are 26.6" or 676 mm tall unloaded with sedan tire carcas thickness. LT tires are thicker, and loaded tire diameters are smaller, and worn or shaved tires can loose up to 1.4" of tire hieght worn down to still legal treaddepth.

    You can at the back go nuts, but the front is limited to 643 daimeter and 245 wide on early cars without mofication. Aft, you can go to almost 28.5" tall slicks on a Fox Stang and Jack Roush it on air springs at the back.

    Like HissingCobra.


    The tire was the factory WS6 BE GoodRich TransAm Firebird tire option on the earlier wide wheels, my mate has them on the back of his 1980 TAFB 4.9 Turbo







    So if the financial incentive is enough, then you might just get away with 245/60 15's front and rear if you do the later front gaurd mods, and drop the inner wheel house liners.






    Mustang Marty's 1979 Green Mustang Coupe 5.0 showed the 245 width and about 651 mm diameter 245/50-16 tire problem,


    Quote Originally Posted by Mustang Marty View Post
    That is exactly the issue. With the wheel toed in like it is now (no adjustments have been made yet) I can just get my fingers between the tire and extension. In the pic below, you can see the rub mark made when the car had the 245/50-16 tires on it. On a level surface they would rub every time I made a turn. On an uneven surface, such as pulling out of my driveway, they rubbed at around one full turn of the steering wheel. The 225's that I have/had installed only rubbed with excessive body roll, as in taking a hard turn at an intersection. It does look like I could trim it back an inch or so to eliminate the rubbing at this point. I was afraid that the edge would catch the tread an damage the part. In the search for these 10+ years ago there are no reproductions and most of the ones that I found looked like they were damaged by tire contact.




    I'm sure the alignment is all wonky at them moment and once I get it a rough alignment it should be better. Right now visually, the tire is really toed in and has a ton of positive camber.

    Other Mustangs that I have owned seemed to also have a tramlining issue when I've had 245's installed. I would like to avoid it as much as possible since the freeways here are full of ruts.


    and BMW Rider solved it using the basic idea from the 1991-1993 Mustangs.

    http://vb.foureyedpride.com/showthre...86#post1768886







    Specialty Foxes were all designed around what I think were Gotti rims and 235/60 15 Pirelli P6's or Pirelli Cinturato CN36'S or P7's back in the day. This had an unloaded wheel diameter of 26.1 inches. At the last moments before production, Ford got a very sharp price from Michelin and got a 1980 Jaguar XJS HE style forged wheel casting made at a greatly reduced price.

    The front wheel arch dimensions were kept back when the TRX's at 220/55 390 initally got selected. Potential snow chain use, and the extensive use of the 190/65HR390 tire in Ford of Europes 1978-1985 Granada 2.8 Injections brought a further downgrade for the 1979 release of the Mustang and Capri. Ford had major problems with front tire covering for the proposed Japanese MIT transport regulations for wheel covering, so they kept the wheels well covered.

    Although it took a few years for the 220/55 VR 390 to be domiciled back to the Mustang GT and Capri RS....it was initially an 80-82 XR7 Cougar and 80-82 Thunderbird tire.


    On all pre 1991 cars, any greater than stock caster increases and anything more than 230/55 VR 390 present a wheel arch problem on full lock.


    The wheel clearance problems were fixed first on the S cars, the 1983 Thunderbird and XR7 Cougar, and the LSC Mark VII and revised 1986- 1988 Thunderbird and XR7 Cougar's got changes to suit 26.1" (663 mm) tire diameters (unloaded....loaded, thats about 3% less or 25.3 inches or 643 mms).

    The SVO used the reprofiled front apron to clear the wider 225/50 16's, but on those, 225/55 16's and 25.75 inches or 654 mm of tire height JUST clear.

    They used the same 15 x 7 J Gotti rims as the designer clinic 79 Mustang Cobra,



    and looked at the Capri wheel arches reprofiled with the next size up 16 x 7j Gotti BA75's, 1983 picture by a Ford sub contractor.



    before backtracking to a do minimum apron /valance change.

    For the last Foxes, the fender is front cut on 91-93 5.0's to clear the increased castor and 663 mm nominal maximum design wheel size, same as the LSC Mark VII.

    the fenders are shortened



    The extenders or aprons from the valance are shortened like BMW Riders above.








    The clearance problem for wheel diameter is solved by using the LSC VII inner fender Poly Ethylene wheel house insert.

    Once Ford fixed the clearance issues, they progressively moved to 16" rims on SVO's, then rolled out the option on various 5.0's after 1990.

    In fact, the LMR TRX is a knockoff of a stock SVO wheel in TRX form with a stock 16" 7 " wide wheel offset or 36 mm back space wheel, and should be treated the same way as the old Australian Holden V car HDT Commodores were, with 225/50 16's or 235/60 16's or 16″ x 8″ rims or something like the 245/45VR16s like the HDT Director had.

    Going through it all, the Mustang from SVO on started using 1985 Hoden Dealer Team Commodore SS wheel and tire combination of standard Corvette brake package and the Corvette Aero 16" x 7" HDT Aero rims with 225/50/VR16 Bridgestone Potenza tyres . 16″ x 7″ HDT Aero rims with 225/50/16 Pirelli P7 tyres. 16″ x 7″ and 16″ x 8″ Momo star rims were optional


    http://vb.foureyedpride.com/showthre...for-16in-ARE-s


    Sometime before 1978, Ford knew that Renault was going to campagin the A310 V6 Renualt Alpine in Group 4 World Rallye and the possibilty of what became the later Group B classes with Gotti BA75's on Pirelli P7's with 205/50VR15 (front) 7Jx15 with an ET35 offset on three or four stud later 100mm PCD hubs, and either 285/40HR15 at the rear on 10Jx15 ET10 with three or four stud later 100 PCD's, or 235/40 15's.




    French made Gotti 10 slot three piece BA 75 wheels. They were on pre production 1979, the 1980 IMSA GTP/GTO, and the 1983 SVO pre-production car TopGear85 listed above , from 185 littlies to 345 biggies....

    Renaults "Buck Rodgers in the 21st Century" R5 mid engineed turbo complicated the development of the Alpine A310 2.7 and 2.9 V6, but it eventually used the planned Gotti rims too



    The whole Mustang and Capri range was designed around 15 x 7's, with the potential to go 235 at the front, and 285 at the rear.

    I'd go to BFG'S 295/50 15's on 15x10 Gottis.

    The ideal sizes are 235/60 15's, and to clear them, you just use 1991-1993 Guards and modify the front apron to suit.

  8. #8
    FEP Super Member xctasy's Avatar
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    javdog, see above.

    A set of 1991-1993 front guards repainted should factored into the price of four 245/60 15's.

    Personally, I'd do it.

    You just have to be carefull to ensure nothing rubs at full droop and lock to lock.


    Be warned that the tires for light SUV's have a 18 mm tread depth and might not be 26.6" or 675 mm tall, could be even bigger, and the front will require more caber and caster to cope with tires that are very tall in the side wall and "gummy".

  9. #9
    FEP Super Member erratic50's Avatar
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    As you increase ride height, roll-center starts to become a concern.

    A 245/60/15 starts to beg for caster/camber plates or X2 balljoints or drop springs or something to get it back down that 1/2"+ lower where factory ride height was.

    Plus without all the measures discussed they will rub like a pig.

    245/45/17's do fit on my 86 but there were a lot of tweaks made to steering settings to get there including spindle to strut adjustments.

  10. #10
    FEP Member javdog's Avatar
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    Thank you guy are all the great info. Unfortunately by the time I got back to the guy the tires were sold.

  11. #11
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by javdog View Post
    Thank you guy are all the great info. Unfortunately by the time I got back to the guy the tires were sold.
    That's fine, I've found the same thing in 15 to 16 inch tires, they drop of the face of the earth, then re-apear like the old 295/50 15's did.

    One thing for you erratic 50 and javdog.

    The Mustang copies 100% the work Jack Talank did with the wheel arch enveopes on the Fox Stang...he basically made it the same as the XA/XB/XC and 1970 Tornio and 1969-1973 Mustangs. That allowed biggies and littlies but also, the front was designed to run less wheel height than the back.

    The result was much like the European Capri, Ford went to tiny height front wheels for a time. It took years for Ford to move up to taller wheels with radical roll center changes.

    Even in this video

    https://www.youtube.com/watch?v=OyJBxznU7cE


    The 6 to 7 hour log distance and short circuit race cars had stock pickup points, biggies and littlies, and they spent more time on making sure they had no bump steer and plenty of guard clearance.

    Today, you can replicate that stunning stance of the Fat Unibody X-shell Fords in any Mustang. I'm using 16" wheels on my planned future Fox, and plan to use the same kind of tall wheels. Its all about finding a way to use the stuff thats on sale, without being too cheap.

    I've got 235/60 16's from my RAV 4 on my Four wheel drive Nissan Stagea, and I've found the height incease reduces crash through, and doesn't hurt hnadling as the width level and peak grip is better too. The power steering is heavier, and in very difficult switchbacks, the steering is more predictable even with the higher roll center. I found the same thing when I swapped to bigger tires on the 81 Mustang.

    Geometery, especially on the pre 1987's, is very poor, but yep, caster plates and later cross members with proper Ackerman are worth it. The audiable tire scrub on tight lock low speed conrnering in urban environs is due to the Mustangs 5" shorter wheel base, and Ford waited 8 long years to fix that. My Michelin TRX's chopped out like crazy over 4 years I had them on. I've seen the same thing down here in our short wheel base 71-78 Chargers, and the Maverick two door Grabber 302 a friend had. With its 5 inch shorter wheel base did the same thing.

    Mass production did eventually improve the breed, so there are solutions and options.

    SUV tires for Specialty Sports cars aren't a good idea, but if you have to use them, then you should attempt to ensure you've got as much castor as you can get, and attempt to camber the wheels without bump steer.

    Steve Ross, a campagner of Triple Weber Chyrsler E48's down here, used to grap some Caterpiller bolts, and camber the wheels like a rallaye car, and then have the tires conical shaved by driving it on the highway for a few thousand miles. The car on race tracks then cornered supperbly.

    People decry differnt wheel diameters and widhts front to back, but it was done on the best Fords and Holdens back in the 70's, and if you do the anti roll bar and spring rate and damper (shockie) combination testing on a parking lot, you can dail a combination in with odd ball tires

    see this, the way all the old V8 Showroom special L34 and GT351's used to play on the rac track with tire sizes we would deam SUV tires today.


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