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Thread: Need Help - Tire Travel vs. Fender Lip

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    Need Help - Tire Travel vs. Fender Lip

    Crazy or not, I have embarked on the same journey to build the same great car as you, the Factory Five Roadster. I now have a 1998 SVT Cobra in the garage that I am preparing for the kit. There is a wealth of knowledge on here. I highly respect your opinions. I am looking forward to this and am glad it is a well trodden path.

    One particular thing that I cannot compromise on this car is the relationship of tire to wheel well. It surprises me to see so many pictures on the FF company website that have tire sidewalls meeting up vertically with the lip of the fenders. Because the fender tapers in, there is no room for the wheel travel into the fender. As a result, they make the ride height with space between the top of tire and wheel well. They also must have severe limits set up in suspension travel. I do not want that. I want the tire to be able to travel in the fender for functional reasons and also aesthetic. I do not want to end up in a situation where I bought avset of FF wheels or other brand and they not fit perfectly. If you look at vintage examples of this car, you will see that the tire nearly always tucks in a bit and there appears to be plenty of room for travel in the fender. This is the look I want, but with 17 or 18" wheels.

    Here are good fender to tire relationships:

    Attachment 73873

    Attachment 73874

    Attachment 73875

    FullSizeRender(5).jpg

    FullSizeRender(6).jpg

    FullSizeRender.jpg

    What I do not want:

    FullSizeRender(3)b.jpg

    FullSizeRenderb.jpg

    FullSizeRender(4)b.jpg

    FullSizeRender(2)b.jpg

    Please provide any advice on ensuring that I do not end up with a wheel and tire combination that end up interfering with the wheel well lips. The FF company cars do this and it concerns me that their off the shelf wheels will do it as well.
    Last edited by Connedale; 09-20-2017 at 08:30 AM.

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    Senior Member CraigS's Avatar
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    If you will have a solid rear axle the tire does travel straight up when you go over a 2 wheel bump. If the car is rolling in a turn or you go over a one wheel bump the tire moves in slightly as it goes up. On my MkII w/ the stock fenders it would hit occassionally w/ a full tank and a passenger but it never hit running an autocross. If you have IRS the front and rear tires move in slightly as they go up no matter the type of bump. As you research this be sure to look only at MkIV cars as the fenders front and rear are very different from previous Mks. The only comments I have seen and experienced re; MkIV fenders is that the front is tight just ahead of the tire when you steer fully left or right. I have not seen any complaints about tires hitting fenders over bumps. Look at EdwardB's build thread. He has a lot of pics. These are the specs for the FFR halibrand replica wheels. Backspace and width are the critical #s to use to compare to other wheels.
    Wheel Set Part Number: 14865
    Front Wheel Size (Diameter x width): 17"x 9"
    Rear Wheel Size (Diameter x width): 17"x 10.5"
    Front Wheel Backspace: 6.00" (24mm Offset)
    Rear Wheel Backspace: 6.7" (27mm
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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    Senior Member edwardb's Avatar
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    I can't give you specific answers (not sure what those would be...) but maybe can give you some additional things to think about. First, the suspension may not move as much as you think. I can't cite specific numbers because I just don't know. But it's not multiple inches each way. When you say "tuck into the wheel wells" that suggests to me anyway you think the suspension has more travel than it really does. Don't get me wrong, if the tires are outside the fender lips and close, they will hit. But they don't have to be tucked way inside to not hit. Second, for the rear suspension it does make a difference which suspension you're planning. Solid axle builds (3-link, 4-link) are more limited than the IRS. This is because of the very short driveshaft and the need to not exceed U-joint angles. This is one of the reasons IRS is a little more comfortable ride. Third, ride height makes a big difference. The relationship of the body to the chassis is fixed. But you can adjust the relationship of the wheels/tires to the body with ride height. Generally the 4-inch range from the chassis tubes is used. A little lower in the front and slightly higher in the back maybe. But that's the range. Fourth, tire pressure affects this a little. My experience is many don't understand how soft these tires need to be run. Guys are used to the 30+ in their DD's, and don't realize these cars should be in the low 20's. Fifth, alignment will matter as well. Finally, the wheels (offset, etc.) and tires you choose will matter. All of these factors go into how the wheels/tires sit in the openings. With so many variables, it's no surprise you can find many different examples of how these look.

    FWIW, this is my latest build #8674. Stock FF front and rear suspension including the new (2015+) IRS setup. FF 18-inch wheels. 245 fronts, 315 rears. 3-3/4 inch ride height front, just over 4 inch rear. Factory recommended alignment specs including 6+ degrees of caster in the front with power steering. Tire pressure 22 psi front, 24 psi rear. As you can see from these pics, tires are just inside the wheel well lips. 1600 miles now and no issues with rubbing. The side view isn't the best because it's a wide angle lens taken from pretty close. (Sorry about the dumpster in the background...) But the wheels/tires are centered reasonably well in the openings. This is something that's discussed a lot. But I'm OK with how it turned out. Hope this helps a little.



    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread and Video
    Build 5: 35 Hot Rod Truck #138. LS3 and 4L65E auto. Rcvd 01/05/2021. Legal 04/20/2023. Build Thread. Sold 11/9/2023.

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    the suspension on the roadster is super stiff, very little travel more like driving a go cart. I believe ther are 550 lb springs in the front and 450 in the rear.

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    Thanks guys, I appreciate the responses. Just to be clear, I am planning on having the top of the tire higher than the fender lip at rest. I know myself pretty well. If I don't have a plan nailed down before the order, I will end up getting something that does not meet my expectations. I will just try to live with it to move on, but at the back of my mind I will not be satisfied with the result. I need certainty in this. I wish they provided a little too much backspace and provide a wheel space kit with the wheels. That way, you can nail down the position within 1/8".

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    Senior Member edwardb's Avatar
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    Quote Originally Posted by Connedale View Post
    Just to be clear, I am planning on having the top of the tire higher than the fender lip at rest... If I don't have a plan nailed down before the order, I will end up getting something that does not meet my expectations. I will just try to live with it to move on, but at the back of my mind I will not be satisfied with the result...
    You'll be at 3 inches or less ride height and the control arms above their intended roughly horizontal locations. Neither desirable, and pretty big trade-offs for something so subjective IMO. Just saying. Larger diameter tires might help, including the 26.5 you mentioned. The pictures I posted are 25.5 diameter BFG's. Good luck.
    Last edited by edwardb; 09-20-2017 at 09:53 AM. Reason: Corrected tire sizes. My bad.
    Build 1: Mk3 Roadster #5125. Sold 11/08/2014. Build 2: Mk4 Roadster #7750. Sold 04/10/2017. Build Thread
    Build 3: Mk4 Roadster 20th Anniversary #8674. Sold 09/07/2020. Build Thread and Video. Build 4: Gen 3 Type 65 Coupe #59. Gen 3 Coyote. Legal 03/04/2020. Build Thread and Video
    Build 5: 35 Hot Rod Truck #138. LS3 and 4L65E auto. Rcvd 01/05/2021. Legal 04/20/2023. Build Thread. Sold 11/9/2023.

  8. #8

    Steve >> aka: GoDadGo
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    Quote Originally Posted by Connedale View Post
    Regarding the rear wheel versus the rear fender arch issue:

    I have shortened the rear control arms thus shortening the wheelbase by about .70"; however, rear tire clearance had to be given a lot of attention to make this happen because running a 315 width tire "MAY" come in contact the rear cockpit aluminum at full suspension flex.

    I'm running 245/45-17's up front with 285/40-17's out back with wheels that are 17 X 9 and 17 X 10 rims.

    In addition while I don't have clearance issues, making this change will require shortening the already short drive shaft of any "Normal" build. Since my build is "Not Normal" custom work and control arms were required.

    Example of a Not A Normal Build:

    https://youtu.be/_wnHDNgnNqs

    https://youtu.be/yL4UmpII9ek

    Finally, my wheels are no longer in production from my vendor of choice, but similar wheels are available at the supplier shown if you are interested in this style wheel:

    https://lmr.com/products/94-04-Musta...ary-Wheels#320

    Good Luck & I'm Sure You'll Figure Things Out!
    Last edited by GoDadGo; 09-20-2017 at 08:24 AM.

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    So with 26.5" tires (same diameter as billboards), I was hoping to easily get the tire in there. Am I mistaken?

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    Steve >> aka: GoDadGo
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    Quote Originally Posted by Connedale View Post
    So with 26.5" tires (same diameter as billboards), I was hoping to easily get the tire in there. Am I mistaken?
    The 285/40-17 Nitto 555's are 25.98" tall and 11.42" wide.
    These are the tallest I could find a 17" tire.

  11. #11
    Out Drivin' Gumball's Avatar
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    Here is my Mk3.1 with Avon CR6ZZ tires - 245 rear and 225 front. Ride height is around 4 3/4 or so, with no issues of bottoming the suspension or tire-to-body contact or rub.

    Later,
    Chris

    "There are no more monsters to fear, and so, we have to build our own."
    Mk3.1 #7074

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    Senior Member wareaglescott's Avatar
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    Seems to me if you are running low enough that the tire is within the lip of the wheel well you are going to run into other issues you are not considering with that low of ride height. Primarily bottoming out because you will be at about 3-3.5" ride height. Also if you want the rears like that I assume you don't want the nose pointing up so a level body is going to have the nose very low and potetnitaly scraping on a very minimal incline as well as a chance of front tire rub during turns will be increased. I don't believe the MK4 body is setup to be run like that. Not saying you couldn't do it but it might take you down the road of some custom fabrication.
    You did say "at rest". Are you considering air suspension or something?
    MK4 #8900 - complete kit - Coyote, TKO600, IRS - Delivered 6/28/16 First Start 10/6/16 Go cart - 10/16/16 Build completed - 4/26/17 - 302 days to build my 302 CI Coyote Cobra - Registered and street legal 5/17/17
    Build Thread http://thefactoryfiveforum.com/showt...e-build-thread
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    Scott, by at rest I mean the natural position of the wheel tire cruising or parked.

    Gumball, I think you basically have what I am looking for. The rear tire appears slightly in the fender. The front tire does not have to do this. It looks right and is common on original cars and backdrafts. I wish I could have the best of both worlds: a Factory Five chassis and Backdraft body.
    Last edited by Connedale; 09-20-2017 at 11:26 AM.

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    Out Drivin' Gumball's Avatar
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    The reason my tires extend a bit more into the wheel wells is that they are a fair bit larger in diameter than the 15" tire sizes recommended by FFR. This allows the look I was going for, while retaining the appropriate ride height, suspension / steering geometry, and ground clearance.
    Later,
    Chris

    "There are no more monsters to fear, and so, we have to build our own."
    Mk3.1 #7074

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    Are those FFR wheels Gumball? I do like the look of your Avons and others with Billboards. It is just a matter of them to work with the new IRS. I would have to go off the script for brakes.

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    Senior Member CraigS's Avatar
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    Don't look at Gumballs car for guidance. It is a a Mk3.1 w/ a completely different body. Look at EdwardBs side picture and see that there is 1 to 1.5 inches top of tire to fender lip. And that is at approx 4 in ride height. To get what you want looks wise, you would need to lower the car at least an inch, or find a tire that is TWO inches larger diameter. And that will create a host of other problems. I think your best bet is to use the standard FFR wheels/tires/ride height and do some fiberglass work.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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    Steve >> aka: GoDadGo
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    Take a look at the following which may give you some good information on wheel fender clearances:

    https://en.wheelsage.org/shelby/cobr...ctures/cme6q1/

    https://youtu.be/FJpASOjJWa8

    This was Carol Shelby's personal car.

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    Senior Member phileas_fogg's Avatar
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    Quote Originally Posted by CraigS View Post
    I think your best bet is to use the standard FFR wheels/tires/ride height and do some fiberglass work.
    Exactly.


    John
    MK IV Roadster #8631
    Ford 302, Holley Terminator EFI, T5z, 3.55 Rear End, IRS, 17” Halibrand Replicas (9” front, 10.5” rear), Nitto 555 G2’s (275/40ZR17 front, 315/35ZR17 rear), Fast Freddie’s Power Steering, F5 Wilwood Brakes, FFMetal’s Firewall Forward, Forte’s Hydraulic Clutch & Throttle Linkage
    https://www.ffcars.com/threads/phile.../#post-4776313

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    Member Frank Messina's Avatar
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    Is using the pin drive width suspension pieces an option for you? That would bring things in about 2.5 inches a side and that would allow you to put the wheels where you want them. Just a thought.
    Frank
    FFR 4440 - V8, Manual Trans, Htr, WSW, IRS. I wouldn't change a thing.

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    Unfortunately, pin width takes away the IRS option. I am going to have to do custom backspace. I think the best plan is to build and get on the pavement with donor wheels and temporarily mounted body. Then, I can measure exactly and order what I want.

    275/40R18 gets me 26.7 tire diameter. What do you think?
    Last edited by Connedale; 09-21-2017 at 06:27 PM. Reason: Edited tire size. Thanks GoDadGo!

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    Steve >> aka: GoDadGo
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    Quote Originally Posted by Connedale View Post
    Unfortunately, pin width takes away the IRS option. I am going to have to do custom backspace. I think the best plan is to build and get on the pavement with donor wheels and temporarily mounted body. Then, I can measure exactly and order what I want.

    275/45R18 gets me 26.7 tire diameter. What do you think?
    http://www.oewheelsllc.com/Wheel-Sin...inch/year/2003

    I'm running a tire that is 25.9" (285/40-17) on the rear so I don't see an issue with it, but I think you mean 275/40-18 not 275/45-18.
    Last edited by GoDadGo; 09-21-2017 at 05:58 PM.

  22. #22
    Senior Member CraigS's Avatar
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    275-40/18 might work for you at 26.7. Most of the 275-45s are 27.? so I would be concerned that won't work. The 26.7 OD combined w/ maybe a 3.5 inch ride height might be just what you are looking for. There are also 265-40s at 26.0 OD for the front. Good thing is these tires will also be fine on the standard FFR 18 Halibrand wheels...ooops I just noticed that the 18 in rears are 11 width. You could get four 9 inch and both the sizes would fit. Or some of the Mustang aftermarket wheels in 18 are a 9 front and 10 rear. This looks real good;
    https://www.americanmuscle.com/anthr...8x9-18x10.html Scroll to the specs and note it is 7.2 back space which is .4 more than the usual 17 x10.5 and it's .5 in narrower so the outer lip would be .9 in further inside the fender.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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    275/40/18 gets me 10.8 width tire. The specs on these Nittos say this tire size is good for 9-11” rim width. I should be good with the FFR rims if the offset works out.
    Non-FFR plan B:
    With these American Racing VN427s I can custom order my offset and do 11” width. I don’t have to pay for powder coat either since I can order black with polished nock-offs

  24. #24
    Senior Member CraigS's Avatar
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    WOW, I didn't look at the rim specs for the 275/40/18 and never would have expected to see 11 wheel width as OK. They also have a 305 w/ a 26.4 OD as an option for you. Also a 265/40 for the front but that may be too much OD so there are 245/40s as an option too. Looks like things will work out for you after all.
    FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.

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