Which creates more fender clearance: rolling or pulling? | Project Endurance Race Miata

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Update by Tom Suddard to the Mazda Miata project car
Nov 1, 2022 | Mazda, Miata, Konig, Nankang, Good-Win Racing, Fender Rolling, Fender Pulling

Race cars have big fender flares because they look cool, right? Well, not quite. Sure, they look great, but the real point of flares is to make room for bigger tires.

Bigger tires make more grip, and more grip makes race cars faster. That’s why we’d ordered some meat for our LFX-swapped Miata: two sets of 15x10-inch Konig Dekagram wheels from Good-Win Racing wrapped in 245/40R15 Nankang CR-1 tires.

[200-treadwear tire test | Falken RT660 vs. Yokohama A052 vs. Nankang CR-1]

Yeah, these wouldn’t fit under stock NA Miata fenders. But before we broke out the Sawzall, we figured it was worth attempting an aggressive fender roll/pull. Maybe, just maybe, we’d be able to stretch the factory sheet metal over the new wheels and tires.

 

Rolling vs. Pulling
What’s the difference between these two fender-massaging techniques? Both are ways to create more tire clearance, but each goes about it differently.

The goal of rolling is to flatten the horizontal lip inside the edge of the fender up against the vertical inner face of the fender, creating more room for the tire to move.

Pulling a fender, though, doesn’t attempt to shrink the sheet metal. Instead, it stretches it out, pulling the lip of the fender up and out to make more room for the tire. It’s a minor distinction, but knowing when and how to use each technique will help you fit bigger tires with less damage to the car.

 

How Do You Do It?

After installing our new wheels and tires and cycling the suspension, we knew we need to be quite aggressive with our fender treatment.

[10 Common Suspension Problems and How to Cure Them]

So we broke out our fender roller and our heat gun and went to work, starting with the front fenders. Up front, we rolled the OEM undertray mounting tabs as flat as possible, then brought the lip up as much as we could.

From there, we had to do a pretty aggressive fender pull to make room for each tire at full compression. It’s not the most beautiful work we’ve ever done, but it did clear the tire. Success!

In the rear, we had an easier time.

After rolling the OEM pinch weld flat, all it took was a minor pull in a few areas to clear the rear wheels. We stepped back to admire our work: Our fenders would never look straight again, but all four wheels now fit without rubbing.

If there’s one piece of advice we can give, it’s to go slowly and work a little bit at a time. Metal and paint don’t like to move quickly, and you’ll get better results if you work your way up to the intended result.

Wheels and tires installed, we turned back to the other projects. We had a race car to finish.

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David S. Wallens
David S. Wallens Editorial Director
11/1/22 1:34 p.m.

Sort of related, I have seen some pulled/stretched fenders on E46 M3s that looked factory. 

Captdownshift (Forum Supporter)
Captdownshift (Forum Supporter) GRM+ Memberand MegaDork
11/1/22 2:41 p.m.

Props for mentioning the heat gun aspect, if it's overlooked you're going to have a bad time. 

deaconblue
deaconblue New Reader
11/1/22 3:21 p.m.

Used the same rolling tool and a big heat gun on my old FC RX7 front fenders to make room for some 225/45 on SSR 17x8.5" rims (along with some bolt on spacers). Not the most fun project, but it looked cool afterwards.  There are days when I truly miss that car...

Olemiss540
Olemiss540 HalfDork
11/1/22 4:43 p.m.

Cutting.

msterbeau
msterbeau Reader
11/1/22 6:10 p.m.

Tools makers!  Combine the lip roller and an english wheel to make something the takes this a step further and puffs out the fender surface for even more clearance.  :-)

KyAllroad
KyAllroad MegaDork
11/1/22 6:45 p.m.

On my NA CSP build I rolled and pulled the fenders to fit a 275/35-15 A7 on a 9" wheel.   It worked but barely.

 

When the new owners of said car moved up to 10" wheels (same size tire) they HAD to cut the fenders.

RonB001
RonB001 GRM+ Memberand New Reader
11/1/22 7:06 p.m.

I appreciate the article, but need more information about pulling.

 

In my inexperienced head, I'm imagining fingers and biceps, but I'm guessing that isn't exactly the process  ;-)

 

What tools are needed for the pull?  Are any pictures of that process available?

te72
te72 HalfDork
11/2/22 10:30 a.m.
RonB001 said:

I appreciate the article, but need more information about pulling.

 

In my inexperienced head, I'm imagining fingers and biceps, but I'm guessing that isn't exactly the process  ;-)

 

What tools are needed for the pull?  Are any pictures of that process available?

This is how I did the front fenders on my Supra, but it certainly wasn't a pretty job. It works though, and that's all that mattered at the time.

 

Thing about metal though, you stretch it in one spot, it almost certainly shrinks in another spot. The trick is finding out how to get it to do what you're wanting. =)

wspohn
wspohn SuperDork
11/2/22 12:05 p.m.

Taking a fender with a right angle lip and folding it flat (carefully) is sometimes enough to give you clearance that you need. In the old coach built days they used to do fender lips like that, rolled over a length of hard wire (had to watch out for unlike metals setting up for electrolysis though).

One thing that many seem to overlook is when the interference takes place. A slight change in spring rate can fix a too soft ride resulting in interference and on live axle cars a Panhard (or Watt's link) can eliminate fouling.  Of course if you are going for the Hot Wheels look with far more tire than you need for performance purposes, nothing but flares are going to do it.

 

z31maniac
z31maniac MegaDork
11/2/22 1:18 p.m.

Since I can't read the article, the answer seems to be pulling.

Rolling is just that, rolling the inner lip flat against the inside of the fender. 

Pulling is when you're actually changing the outer contour of the fender to create more room. 

JahjahSQC
JahjahSQC New Reader
11/2/22 4:25 p.m.

I never thought about this topic as one versus another. I've always felt it depends on if you care about racing classes because sometimes you can't pull fenders, only roll.

& beyond that, I've always felt it best to start with a roll, then pull only if it's necessary. I have zero hesitation to roll any fender, but I'm super hesitant to start pulling on the metal.

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