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Maximum Wheel and Tire Width Fitment Guide for the FD

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Old 09-07-23, 05:25 PM
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Originally Posted by Djseto
His suspension settings were pretty money for track days so I guess I gotta ping @Howard Coleman to see if changing caster will affect handling adversely from his suggestions.
It will improve handling and self steering, but make the steering heavier.
Old 09-07-23, 10:00 PM
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Stock alignment caster is 6 degrees.

You can get an FD down to 4 degrees with stock adjustments (as little as possible), but why?

I prefer the handling from higjer caster.

Stronger self centering of the steering wheel
high speed straight line stability
higher outside tire camber on tight (lowspeed) turns

I even prefer the "disadvantages" of high caster

Higher steering effort (stock FD is a bit overboosted for me)
Rear inside wheel weight jacking causing rotation (oversteer bias) on turn in.
Old 09-08-23, 12:20 AM
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So I looked at my alignment report from when I last had the car aligned and it was set at 6 degrees.

so based on this, I likely can’t mess with caster. Is my tire size just not good upfront? Too much sidewall?
Old 09-08-23, 11:33 AM
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6 degrees caster sounds good.

Maybe its just the angle of the picture that made ot look like you had more room behind the tire in the wheel well.

Yes, your tire height is right on the edge of "too tall" at 25.3".

I had some minor rubbing on the front inside wheel well and the rear outside (though I had OEM mud flaps) with 25.3" tall 265/35-18 595RS-Rs

Stock tire height is 24.8" tall and Mazda didnt give wheel wells much room for taller tires.
Old 09-08-23, 02:24 PM
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Originally Posted by Valkyrie
Details on clearance, rubbing, fender modifications, suspension etc?

You managed to fit 285s under stock fenders?

@Valkyrie Front fenders are rolled and rears are stock.
I’m about a 1/2” lower than stock on Tein Flex coilovers.
Definitely not slammed, no issues with speed bumps and such.
Also, no rubbing with quick hits around town but I haven’t track the car either.
I love the meaty square look, extremely happy with this setup.


Steve

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Last edited by estevan62274; 09-08-23 at 02:29 PM.
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Old 09-08-23, 07:29 PM
  #656  
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Originally Posted by Djseto
Need some guidance on tire sizing so as to not rub my fender liners. I used the TireRacks tool to put the following on my FD years ago:

Front: Enkei RPF1 18x8 +35mm with Michelin Pilot 4s 235/40/18
Rear: Enkei RPF1 18x9.5 +45mm with Michelin Pilot 4s 265/35/18

When I set up the car for the track days per @Howard Coleman tire/suspension setup thread, I had to set my ride height to 26" as 25" was definitely going to rub.
Over the years, I've rubbed through fender liners, especially after track days. I'm tired of replacing Fender liners, so I'm trying to figure out what the right size tire is that keeps an 18" rim size, keeps my ride height, but does not eat liners.

Attached are some photos and yes, I know I need the triangle pieces under my bumper to keep the fender from flopping around. Even with those pieces, when turning the wheel, my current tires rub. I have a replacement set but I won't wanna put those on until I know my fenders are safe from harm.

I don't understand offsets or tire sizing to know what fits. I think the TireRack calculator assumed OEM suspension when giving me sizes vs my Ohlins setup because I doubt they would recommend anything that would rub. It's only an issue up front so I assume I could keep my rears as is even if change the front? Any help would be much appreciated.


If you've got spares ready to go, just cut this section out of the fender liner. I am pretty sure lots of people do this for better brake and oil cooling. This whole section of my liners are missing...

Otherwise, poke two holes in the liner where it is rubbing and use a zip tie or two to give yourself clearance.


For ***** and giggles, you could even try putting your rears on your front to see how they fit...

A 255/35 might actually fit better since its slightly shorter.
Old 02-07-24, 11:15 AM
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Anyone running HRE's "F1 Fitment" on a stock bodied FD ?

F: 8.5 X 18 +34 (235/40)
R: 10 X 18 +40 (275/35)

Seems a bit aggressive but they claim they have scanned the wheel well and it is a safe no rub fitment.

Would love to hear feedback from anyone running this setup or something very similar.
Old 02-07-24, 10:02 PM
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F: 8.5 X 18 +34 (235/40)
R: 10 X 18 +40 (275/35)
Front will require max negative camber when using stock unrolled fenders.

Rear will require around -2 to -2.5 deg negative camber with stock unrolled fender arches.

Its not an ideal or aggressive fitment width wise- just kind of the wrong offsets, wrong rear tire height and big stagger for no reason.

18x10 +50 front and rear (CCW stock fender FD spec) is a better 26 year old rule of thumb that has withstood the test of time to include Mazda Motorsports selling this size for the FD recently.

255/35-18 on 18x10 +50 will fit up front a little easier as tire shoulder is more inward from wheel offset.

The slight strech will provide direct steering feel while stock offset will eliminate trammeling and bumpsteer you get from lower offsets.


Old 02-09-24, 11:15 AM
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Originally Posted by BLUE TII
Front will require max negative camber when using stock unrolled fenders.

Rear will require around -2 to -2.5 deg negative camber with stock unrolled fender arches.

Its not an ideal or aggressive fitment width wise- just kind of the wrong offsets, wrong rear tire height and big stagger for no reason.

18x10 +50 front and rear (CCW stock fender FD spec) is a better 26 year old rule of thumb that has withstood the test of time to include Mazda Motorsports selling this size for the FD recently.

255/35-18 on 18x10 +50 will fit up front a little easier as tire shoulder is more inward from wheel offset.

The slight strech will provide direct steering feel while stock offset will eliminate trammeling and bumpsteer you get from lower offsets.

@BLUE TII - thank you for the reply, you seem you know things so I hope you don't mind if I ask a few follow-up questions:

I'd still like to go with a staggered set-up:

What about (F) 18 x 8.5 + 38 (235/40) - would this be safer and not require max negative camber ?

If the rears are 18 x 10 + 50, what size tire would you suggest ?

Thank you.

Old 02-09-24, 04:27 PM
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The 18x8.5 +38 with same 235/40-18 moves the tire in 4mm, so you could run ~0.75 degrees less camber.

So, probably need around -1.7 degrees front camber at 24.5" to top of fender arch ride height with a completely stock front fender.

Mind you, it wont look flush at all- but if you bring the tire out further to make it look better it will catch the fender lip when turning tight up hill and crease the fender.

18x10 +50 you can run 255/35-18 to 295/30-18. Plenty of pics of 7s with this size wheel to browse.
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