18" on rear


Wwabbit

GT Owner
Mar 21, 2012
1,259
Knoxville, TN
Want to run a particular wet tire on the rear but it's only available as an 18". I'm still working through what that does to the final gear ratios, etc. but maybe someone here has some direct experience with that. It does have a 27" OD so it's pretty close for ABS considerations. Any comments?
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,197
Our OEM rears are just about 29" in diameter - not 27". I think you'll be hard pressed to find something like that in an 18. Then you'll need a wheel with the righ hub centricity, offset and width. I wish you luck!
 

Xcentric

GT Owner
Mark II Lifetime
Jul 9, 2012
5,213
Myakka City, Florida
Gives you a 3.60 ratio. Caliper clearance?
 

RALPHIE

GT Owner
Mar 1, 2007
7,278
Caliper clearance should be OK, since the front and rear calipers are the same, and the rear rotor is smaller than the front - the front wheels are 18", but always good to check, as you will be using a different wheel. Backspacing (or offset) should be checked for an appropriately sized wheel.
 

cobra498

GT Owner
Jul 14, 2010
310
Central Ca;ifornia
Make sure that the front revs per mile are at least 60 more than rear revs per mile or you will be having ABS issues, if you track the car in the rain.
 

Wwabbit

GT Owner
Mar 21, 2012
1,259
Knoxville, TN
Make sure that the front revs per mile are at least 60 more than rear revs per mile or you will be having ABS issues, if you track the car in the rain.

Got it. Thanks.
 

Ed Sims

GT Owner
Mark IV Lifetime
Apr 7, 2006
7,853
NorCal
http://www.ccwheel.com

CC Wheel makes an 18" rear for our GTs that will give you, depending on your tire selection, the same OD as stock. I ran a Goodyear G19 slick with their C14 wheel. Bolt on with plenty of clearance & same offset. Huge weight savings. Do a search on this forum for photos that I posted or look at my GT on the CCW website.

Ed
 

Ed Sims

GT Owner
Mark IV Lifetime
Apr 7, 2006
7,853
NorCal
Make sure that the front revs per mile are at least 60 more than rear revs per mile or you will be having ABS issues, if you track the car in the rain.

You can adjust via a SCT Tuner for different wheel/tire ODs so speedo, ABS, etc will be just fine.

Ed
 

roketman

GT Owner
Mark IV Lifetime
Oct 24, 2005
8,007
ma.
The pre production cars ran on 18’s
 

cobra498

GT Owner
Jul 14, 2010
310
Central Ca;ifornia
Speedo will be fine, ABS will not, I set diameter and still got an ABS light after about 2 hard track laps. The car then went into limp home mode and I had to reflash the tune to get another two laps. You would need to change the tone wheels to get the ABS to work with off size diameters or install a Bosch race system.
 

ultrasportracing

GT Owner
Aug 31, 2011
490
Perth Western Australia
If you want to track the car with different sizes from standard, couldn`t you just pull the ABS relay.
 

roketman

GT Owner
Mark IV Lifetime
Oct 24, 2005
8,007
ma.
If you want to track the car with different sizes from standard, couldn`t you just pull the ABS relay.
Great idea! The only problem is than is that John would have to relearn threshold braking!
LOL!
 

cobra498

GT Owner
Jul 14, 2010
310
Central Ca;ifornia
The CAN-BUS will be looking for proper ABS operation, if does not get the proper information the ECU will "protect" you and not allow full output so you will not have ABS or HP.
 
My dear Ford GT 2005/2006 aficionados,

i wanted to go with racing tires on Formula one tracks, like Red Bull Ring in Austria, Hockenheim GP Circuit, and Spa-Francorchamps, and the most wanted Nuerburgring "Nordschleife".

Here how i solved my problem:

i had good contacts with Juergen Alzen, which is competing with a Ford GT in GT3 class only on the "Nordschleife" and he said to me, all racing tires which he could provide to me, are max. in the rear 18 ".
So he said, you must get a set made for you, from a well known racingwheel supplier.
As my street wheels are from BBS, i suggested BBS-racing wheels.
He mentioned, you know that will cost you some money, they are certainly not cheap.
I said, that a quality wheel has its price.
Told him, please do order 2 rear wheels for me. We measured all measurements of the standard 19 " & the forged OEM-BBS wheels and have given that info to BBS.

They were able to provide these wheels quite quick, but i have the bill in switzerland, and i live now in spain.
I can provide here Juergen Alzens contacts, e-mail, phone & fax nrs.

Juergen Alzen Motorsport website: www.juergen-alzen-motorsport.de
Gewerbepark 12
D-57518 Betzdorf
Germany

e-mail:
j.alzen@t-online.de

phone: ++492741 97 23 97
fax: ++492741 97 23 94

mobile: ++49171 6 24 62 71 ATTENTION: often not in use, while he is racing,testing, or flying his Robinson R 44 helicopter

Remember: office hours in germany are different than the USA: mo to fr 9 a.m. to 16 p.m. but take into consideration that there is a 6 hours difference to standard eastern time of the US. (Example 2 p.m. in germany is 8 a.m. in NEW YORK)

Hope for the forum that Juergen can help, for owners which would like to use 18" gearwheels to put race compound tyres (SLICKS) for track use.

SINCE I USE THEM ONLY ON RACETRACKS, I NEVER HAD ANY ABS PROBLEMS, EVEN IN SPA, WHERE YOU REACH SPEEDS UP TO 160 MPH AND MORE WITH RACINGTIRES !!!!

sincerely yours

FelixIbizaSwitzerland
 

fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
11,504
Belleville, IL
Why did you just not go with Hoosiers? They are custom fit for the GT and resolves the wheel problem.