switching to 16x 7,8's help w tire choice

[sch2046]

I am putting 7 and 8's on my 1980 sc, I see some people have to roll their front fenders, I am not sure what this entails and if I want to mess with that. Are there certain tires w a performance bent that will fit without rolling my fenders? looking at 205/55 and 225/50.
thanks

[Shaun @ Tru6]

Have you lowered your car? If you haven't, or lowered it within the "normal" range, all 205/225 combos will fit without rolling fenders. And you can comfortably put 245s on the rear with 8s.

There are a lot of great tires on the market right now but they have all gotten very pricey

[sch2046]

The car has been dropped to sport driving/auto cross, it is not stock. Is rolling a fender a job an average garage geek can do?

[Shaun @ Tru6]

I think measurements and a pic or two would help. I've rolled a few fenders, the only hard part is not cracking the paint. I used a beam of wood and the lowest setting on a heat gun to soften the paint. There are roller like from Eastwood too instead of a soft piece of pine.

If it's an autocross car you probably have a lot of negative camber so any 205s/225s you may be fine.

What wheels and tires are on it now?

[Otter74]

My car is lowered a fair bit (photo for reference) on 205/225 tires on 7s/8s and, as indicated by others, there are no issues in the front. I do get rubbing on the left *rear* fender in very hard right corners but this is abnormal and as yet unexplained

[Bill Verburg]

Originally Posted by sch2046

I am putting 7 and 8's on my 1980 sc, I see some people have to roll their front fenders, I am not sure what this entails and if I want to mess with that. Are there certain tires w a performance bent that will fit without rolling my fenders? looking at 205/55 and 225/50.
thanks

Some hard #s would be helpful but
there are several factors that will determine how a tire fits

• ride height metric -b
• wheel width and ET, a Fuchs 7is ET23.3
• nominal and actual tire spec, 205/55 x16 can be anywhere from 211 to 218mm wide w/ varying amounts of shoulder blockiness
• tire OD, 205/55 can vary from 24.8 to 25" od
• alignment spec

here's how to measure b, right behind the front tire, center of t-bar perpendicular to ground


If performance is the goal w/ 7 & 8 x16 Fuchs I'd go w/ 205/50 & 225/45, somewhat easier to fit and way superior dynamic behavior

[A930Rocket]

If you were closer, I’d give you my like new Eastwood fender roller.

[Shaun @ Tru6]

Originally Posted by Otter74

My car is lowered a fair bit (photo for reference) on 205/225 tires on 7s/8s and, as indicated by others, there are no issues in the front. I do get rubbing on the left *rear* fender in very hard right corners but this is abnormal and as yet unexplained

Maybe your weight is causing the rub? Or perhaps more likely, worn spring plate and/or trailing arm bushings with some Targa flex?

My lowered 84 with 255s never rubbed with 22/29 bars and ER bearings. But it did twist a lot. Really miss this car.

[PopsRacer]

I’m driving an 88 carrera with 7’s & 8x16’s. Stock sized Conti Extreme Contact tires. The only rubbing I ever got was in the passenger side wheel well and only when I was doing drills on the skidpad and spinning out kinda hard. That took some expert alignment work to sort but now it doesn’t happen. The car is a bit below euro height using stock torsion bars. Camber-wise I’m running -1 deg in front and 1.5 deg in the rear as a compromise between street driving and auto-x. As you you can see in the pics, I did not roll my fender lips. gd lk!

[Bill Verburg]

Rubbing in back w/ 225s is because the ET is wrong

8ET 10.6 Fuchs will have a ton of room w/ 225
9 ET15 will still have lots of room w/ ET15
9.5 ET19 will have zero extra room w/ 275, a little room w/ 255

tire od and ride height and alignment become increasingly critical as the widths increase, and the ETs diverge from Fuchs

[Otter74]

Originally Posted by Shaun @ Tru6

Maybe your weight is causing the rub? Or perhaps more likely, worn spring plate and/or trailing arm bushings with some Targa flex?

My lowered 84 with 255s never rubbed with 22/29 bars and ER bearings. But it did twist a lot. Really miss this car.

Weight, I doubt it. The car is lighter than stock and I didn’t have a lot of weight in it when it rubbed. Bushings are polybronze in the trailing arms and monoballs in the banana arms, and while they make noise occasionally, there isn’t anything in the car’s handling that makes me think they’re abnormally worn. But I’d still peg bushings/bearings as most likely problem origin. Right wheel is a few mm further in from the typical 911 asymmetry. ET is correct, so it’s not a wrong wheel size. It happens very rarely (I’ve rallied it twice this year and it only happened a handful of times, if that) so I’m not really worrying about it.


But back to the OP, they should have no problems.

[wildthing]

RE-71RS on 7s in front I rolled my fenders once while autocrossing. I did bring my bat but no heat gun. Do it at home and you'll be fine.

[PeteKz]

Otter74: Check your rear camber carefully.

I had a similar problem with rubbing on the left rear fender (but not the right) with my Fuchs 16x7's on my narrow body 1973 car. The camber on the right was -0.8 degrees, and on the left it was about -0.4 degrees. Once I got the camber on the left to match the camber on the right, it pulled in the top of the wheel enough that I no longer have rubbing.

Do this before rolling the fender. IME, the tire rubs the inside of the rear fender about 2" above the arch, not at the edge of the arch. If adjusting the camber doesn't solve your problem, then consider other measures.

[Bill Verburg]

Originally Posted by PeteKz

Otter74: Check your rear camber carefully.

I had a similar problem with rubbing on the left rear fender (but not the right) with my Fuchs 16x7's on my narrow body 1973 car. The camber on the right was -0.8 degrees, and on the left it was about -0.4 degrees. Once I got the camber on the left to match the camber on the right, it pulled in the top of the wheel enough that I no longer have rubbing.

Do this before rolling the fender. IME, the tire rubs the inside of the rear fender about 2" above the arch, not at the edge of the arch. If adjusting the camber doesn't solve your problem, then consider other measures.

The OP has an '80 SC, the rear wheel space is very different and much larger than that of a non- SC/Carrera.

an SC/Carrera rear has room from a ~275mm tire, ~122mm f/s and ~153mm b/s, This is not an easy fitment as lots of supporting work is needed but it can be done.

a non SC/Carrera has the same b/s but only ~90mm f/s

yes a 215/60 x15 on a 7ET23.3 hits the wheel arch a couple of inches above the lip, but that's because of the tall tire OD, a n/b can accommodate a 225/50 x16 on a 7ET23.3

[Otter74]

Good point. Car was corner balanced and aligned before I bought it and I’ve never touched it since. Tire wear is consistent left to right but now that I think about it one of the monoballs required service about five years ago and that could have altered the alignment. I’ll check it with my phone.

Originally Posted by PeteKz

Otter74: Check your rear camber carefully.

I had a similar problem with rubbing on the left rear fender (but not the right) with my Fuchs 16x7's on my narrow body 1973 car. The camber on the right was -0.8 degrees, and on the left it was about -0.4 degrees. Once I got the camber on the left to match the camber on the right, it pulled in the top of the wheel enough that I no longer have rubbing.

Do this before rolling the fender. IME, the tire rubs the inside of the rear fender about 2" above the arch, not at the edge of the arch. If adjusting the camber doesn't solve your problem, then consider other measures.

[sch2046]

I will try to upload pictures tomorrow. Thank you all for the help. This is why I love this forum. I am fairly new to air cooled 911's.

[Bill Douglas]

I've got 16 inch by 7"and 8"s on my SC. I did a subtle rolling of the fenders with a baseball bat and sitting on the fender to supply just the right amount of drop. So not terribly scientific. No rubbing at all with 205 and 225 Bridgestone Potenzas.