Rallyarmor mud flaps for MME Rally

highland58 · Jun 10, 2025

I installed these mudflaps on my 25 Rally, they are supersized specifically for the Rally edition. Mark Boris generously gave these to me, he bought them for his GT, but decided they were too large for the GT. They were easy to install, I did not take off the rear wheels as I should have, but I did get them on despite that. These are the flaps as shown on the Rallyarmor site, the size difference is significant.

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally 1749590224921-93

The ground clearance was good on the rear, and the width gives plenty of coverage.
The ground clearance on the front is minimal however.

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally 1749590331968-h0

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally 1749593214650-ov

One of the mounting bolts goes in behind and underneath.

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally 1749593391825-hz

Since I did not take off the wheel, I had to use a right angle screwdiver.
The instructions say to use an icepick type tool in the inserts, I used a roofing nail instead.

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally 1749591251137-re

The fronts were easier with the wheel turned. There are two clips along with the screws and bolt.

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally 1749591075588-s

The flaps are flexible, so hopefully will stand up to impacts and snow pack.
The rear hatch seems to stay cleaner with these deflecting the spray.
Overall, I am quite happy with the looks and functionality, but I'm tempted to trim the front flats an inch shorter.

Here is another view of the flaps:

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally 1749591701872-r8

Tosh · Jun 10, 2025

Talk about Mud Flaps, that girl's got em!

Seriously - very nice! I'll look into that for my pony

spartan · Jun 11, 2025

Nice writeup, thanks! The Rally Armor mud flaps really complete the look.

roamtheworld · Jun 11, 2025

Nice write-up and addition to your Rally!
These are very popular in the Subie world, and I'm providing a link to the product just to complete the post for those interested in purchasing.
https://www.rallyarmor.com/product_...ion-black-mud-flap-metallic-black-logo-p-4050

markboris · Jun 12, 2025

Great write up and photos Dave. Glad they are being put to good use!

Mach-Lee · Jun 13, 2025

FYI these will likely affect the aero and highway efficiency because they stick out so far (acts like a spoiler), but that might be less important for a Rally owner.

markboris · Jun 13, 2025

Mach-Lee said:
FYI these will likely affect the aero and highway efficiency because they stick out so far (acts like a spoiler), but that might be less important for a Rally owner.

Lee, not sure if you mean stick out as in protrude from the side or hang down to low. If protrude from the side, they don’t any more than most other mud flaps like the AOSK‘s. I checked as I had both. However they definitely hang down much lower than regular mud flaps.

Mach-Lee · Jun 13, 2025

markboris said:
Lee, not sure if you mean stick out as in protrude from the side or hang down to low. If protrude from the side, they don’t any more than most other mud flaps like the AOSK‘s. I checked as I had both. However they definitely hang down much lower than regular mud flaps.

Anything that sticks out more than a 1/4" past the factory fenders will have a pronounced effect on the airflow leaving the wheel wells at higher speeds. This area is carefully shaped to control wheel wake turbulence. Even the AOSK mud flaps will cause a drag penalty. Range loss with regular splash guards will be relatively small, perhaps only 1%, but will be proportional to how much the flaps stick out to the side and under the car. Rally-style mud flaps might be as much as 5% range loss at 75 MPH. Which is probably why they're not included in the Rally package.

markboris · Jun 13, 2025

Mach-Lee said:
Anything that sticks out more than a 1/4" past the factory fenders will have a pronounced effect on the airflow leaving the wheel wells at higher speeds. This area is carefully shaped to control wheel wake turbulence. Even the AOSK mud flaps will cause a drag penalty. Range loss with regular splash guards will be relatively small, perhaps only 1%, but will be proportional to how much the flaps stick out to the side and under the car. Rally-style mud flaps might be as much as 5% range loss at 75 MPH. Which is probably why they're not included in the Rally package.

Ok so since these Rally mud flaps don’t stick out any further than the AOSK flaps, there shouldn’t be much more of a range penalty. However they do hang down below quite a bit further. That will also cause range loss too?

On another subject but having to do with range loss and wake turbulence, since I have my custom wheels always made with an offset that keeps them flush with the wheel well opening rather than inset like the OEM wheels are, is than why I rarely see any loss in range with my aftermarket wheel/tire setups?

HuntingPudel · Jun 13, 2025

markboris said:
Ok so since these Rally mud flaps don’t stick out any further than the AOSK flaps, there shouldn’t be much more of a range penalty. However they do hang down below quite a bit further. That will also cause range loss too?

On another subject but having to do with range loss and wake turbulence, since I have my custom wheels always made with an offset that keeps them flush with the wheel well opening rather than inset like the OEM wheels are, is than why I rarely see any loss in range with my aftermarket wheel/tire setups?

Since the mud flaps are already in the aerodynamic shadow of the tire, they won't cause much more range loss than the AOSK flaps. Because the gap near the lower tip of the mud flap is greater than the gap at the upper end of the mud flap, there will be extra drag but it's not as pronounced as it would be with a narrower wheel and tire setup. Your wheels (like mine) will have a much more pronounced affect on drag than the mud flaps. ??

highland58 · Jun 13, 2025

Thank you for the interesting info on the extra drag. For somebody that does a lot of road trips, they probably should not pick the Rally, as it has the lowest range for an AWD extended range MME even without mud flaps. It's still far better than any ICE vehicle though, such as my F-150, so I have no regrets

.

spartan · Jun 13, 2025

I feel like a range hit of a couple miles from the mud flaps would be negligible compared to other factors like driving style, cold weather, a strong headwind... I personally don't think that would be enough to deter me from getting them.

Mach-Lee · Jun 13, 2025

markboris said:
Ok so since these Rally mud flaps don’t stick out any further than the AOSK flaps, there shouldn’t be much more of a range penalty. However they do hang down below quite a bit further. That will also cause range loss too?

On another subject but having to do with range loss and wake turbulence, since I have my custom wheels always made with an offset that keeps them flush with the wheel well opening rather than inset like the OEM wheels are, is than why I rarely see any loss in range with my aftermarket wheel/tire setups?

I'll try to draw:

The big flaps stick out several inches and will create a wake and low pressure zone behind them because the flow past the wheel can't smoothly transition to the body. Keep in mind the air flowing under the car inboard of the tires is blocked from reaching the rear diffuser smoothly as well.

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally maxresdefault-3

Wheels sticking out to being flush or further will be a significant aero penalty because they are no longer sheltered by the wheel arch and the flow will become very turbulent along the sides of the car since most of the air will hit the wheel. This is compounded by an open wheel face that will let a lot of air into the barrel of the wheel. So yes, the combination of open face wheels and them sticking out past the air curtains designed into the aero features will cause most of your loss, the flow would already be so messed up the mud flaps wouldn't matter much compared to a stock car.

Ford Mustang Mach-E Rallyarmor mud flaps for MME Rally figure-6-82-cs.jpg?q=50&fit=crop&w=1140&h=&dpr=1

The air curtains (ducts in front bumper) and the exact flushness of the tires are designed to work together to push air around the spinning wheel smoothly and improve flow attachment to the panels behind. If the wheels stick out any more than stock, the benefit of the air curtain is almost completely negated since the flow out of the duct would just hit the tire tread instead of being able to slide past the tire shoulder as intended.

I estimate around 2–4% range loss on the highway, up to 5–6% in more demanding or windy conditions, and near-zero impact in city driving, where aero matters less.

markboris · Jun 13, 2025

Mach-Lee said:
I'll try to draw:

The big flaps stick out several inches and will create a wake and low pressure zone behind them because the flow past the wheel can't smoothly transition to the body. Keep in mind the air flowing under the car inboard of the tires is blocked from reaching the rear diffuser smoothly as well.

Wheels sticking out to being flush or further will be a significant aero penalty because they are no longer sheltered by the wheel arch and the flow will become very turbulent along the sides of the car since most of the air will hit the wheel. This is compounded by an open wheel face that will let a lot of air into the barrel of the wheel. So yes, the combination of open face wheels and them sticking out past the air curtains designed into the aero features will cause most of your loss, the flow would already be so messed up the mud flaps wouldn't matter much compared to a stock car.

The air curtains (ducts in front bumper) and the exact flushness of the tires are designed to work together to push air around the spinning wheel smoothly and improve flow attachment to the panels behind. If the wheels stick out any more than stock, the benefit of the air curtain is almost completely negated since the flow out of the duct would just hit the tire tread instead of being able to slide past the tire shoulder as intended.

I estimate around 2–4% range loss on the highway, up to 5–6% in more demanding or windy conditions, and near-zero impact in city driving, where aero matters less.

Got it now Lee. Thanks for the through explanation. ?

ipca204 · Jun 16, 2025

Mach-Lee said:
Anything that sticks out more than a 1/4" past the factory fenders will have a pronounced effect on the airflow leaving the wheel wells at higher speeds. This area is carefully shaped to control wheel wake turbulence. Even the AOSK mud flaps will cause a drag penalty. Range loss with regular splash guards will be relatively small, perhaps only 1%, but will be proportional to how much the flaps stick out to the side and under the car. Rally-style mud flaps might be as much as 5% range loss at 75 MPH. Which is probably why they're not included in the Rally package.

or they are not included because they are ugly as sin...

Rallyarmor mud flaps for MME Rally

highland58

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Tosh

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spartan

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roamtheworld

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markboris

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Mach-Lee

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markboris

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Mach-Lee

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HuntingPudel

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highland58

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