Modern trailing arms for the 914?, 986 carriers/calipers/e-brake, more adjustability, more tire? Options

[horizontally-opposed]

I've been reviewing past discussions on these (links below) off and on, having test fit a 215/60R15 Pirelli P6000 on a 911R wheel into both rear fenders of my narrow-body 914. It seems doable, but it's going to take some massaging on the outer fender, custom spacers, and—maybe—narrowed trailing arms. Which got me to thinking about the current state of the 914 trailing arm, which is the same it's been since 1970.

Basically, those heavy, non-adjustable steel trailing arms are one of the very few things on the 914 that hasn't been addressed or evolved by the aftermarket.

I'm running PMB-rebuilt trailing arms with PMB-rebuilt calipers, and can redo them again with reinforcements and/or some reshaping, but I wonder how hard would it be to do blade-type trailing arms of similar strength with less weight and/or more adjustment. Could a 911 spring plate, or a triangulated or otherwise reinforced version of it, be adapted? Looking at the basic design of the 914 arm, it doesn't look all that complicated, but I'm no engineer.

EDIT: Possible use of a machined 986 wheel carrier, an aluminum casting by Brembo that incorporates the 986 e-brake and 986 four-piston caliper mounts, comes up later—a very interesting idea from @Chris914n6, particularly as the castings are available for $100-200ea used or new from Porsche. Bolting that carrier to a new steel trailing arm with a lower damper mount seems viable to me, but here to learn.

The custom work to narrow factory 914 trailing arms looks extensive, but has been done by both @914timo and @sixnotfour as well as, it looks like, Rich Johnson. I could see doing it in the process of moving to 911 e-brakes and 986 2.5 brakes, maybe, but I wonder if a group buy might attract a 914 vendor we all want to support?

Relevant threads:

http://www.914world.com/bbs2/index.php?sho...p;#entry1247827

http://www.914world.com/bbs2/index.php?sho...ailing&st=0

http://www.914world.com/bbs2/index.php?sho...238144&st=0

http://www.914world.com/bbs2/index.php?sho...234391&st=0

[Mark Henry]

I'll look through the links later, interesting.

One issue is the 215/60R15 tires, your choice beyond sucks, best tire you can do is a very short list of all season and winter tires.

Now do this and fit in 17x7" rims and you might have a winner.

[horizontally-opposed]

Test fit of 215/60R15 in stock rear fenders:

[horizontally-opposed]

And on a 911R wheel with stacked washers to optimize spacing.

The wheel/tire fit into both fenders so that the car could be safely lowered, but the fenders would need a bit of rolling/pull before the wheels were spaced further out. It's been done with regular 15x7 Fuchs and Cookie Cutters, but the 911R wheel will provide better offset.

[horizontally-opposed]

Interference!

[eeyore]

If you want to go off into the weeds for ideas, look at the rear suspension bits for the Audi/VW MQB platform (e.g. Tiguan 4motion, Q3 or Q5?)

They have a blade type rear suspension with transverse links for camber and toe control.

[gms]

I have always thought it would be great if someone made trailing arms out of cast aluminum like the later 911s

[Chris914n6]

I have a 225/50-16 stuffed in the rear. I ran out of room between the sheet metal way before the arm could be an issue.

2nd thing... why would I ever want an oversized 215/60-15 with huge sidewall bulge?

[horizontally-opposed]

I have always thought it would be great if someone made trailing arms out of cast aluminum like the later 911s

This. Or carbon fiber if it makes sense, at this point.

I have a 225/50-16 stuffed in the rear. I ran out of room between the sheet metal way before the arm could be an issue.

2nd thing... why would I ever want an oversized 215/60-15 with huge sidewall bulge?

On factory 16x7s, right? I have seen it done a few times. I'm more interested in getting the tire inboard on a 911R-style wheel, as I want to stay with 15s and the "narrow body" look.

185/70R15 or 195/65R15 front and 215/60R15 are the correct spec with the right overall diameter for a lot of Porsches—from the 1973 911 Carrera RS through Carrera 3.2s and 944s of the late 1980s. Good setup, several performance tires available, and period correct looks. There's a lot to like about factory tire sizes—and now there are some good wheel choices as well, ready to mount for similar or less money than "normal" Fuchs that need to be restored and a lot less than previously unobtanium 911R wheels.

https://tremotorsports.com/exterior/fuch-st...deep-6-7-wheels

[SirAndy]

From the looks of it, even if you did use slimmer trailing arms, you don't have *any* space left for the tire to move as the suspension loads.

Every little bump in the road will make the inside of the tire rub. What you show in the pic below is not nearly enough clearance to deal with camber changes as the suspension moves.

(IMG:style_emoticons/default/popcorn[1].gif)


(IMG:http://www.914world.com/bbs2/uploads/post-2058-1611686462.jpg)

[horizontally-opposed]

From the looks of it, even if you did use slimmer trailing arms, you don't have *any* space left for the tire to move as the suspension loads.

Precisely my point above re: dynamic clearance. I know a 215 or 225 can be snuck into the fender, though. Plenty of people have done it.

Tire is going to have to come out, which means more spacer. That may alleviate the need for a relocated brake line or a narrowed trailing arm somewhat, but I am not sure that it would help enough given 914timo's experiences.

[914forme]

I ran 225 on 15s never 16s, spacers where used for inner clearance. Fenders ended up being mildly flared to do it.

LOL these where Hoosiers A7 so they tend to run a bit wider than the numbers on the sidewalls. Rule of thumb in NASA racing is the Hoosier run 20 over the number posted on the sidewall.

Would prefer to do a carbon fiber arms if redesigning an arm, but lets be real, if going to all that, change it from a trailing arm to something a bit better. Not going to say what the would be but for me I have had my dream setup for a long time.

Then I hit the easy button and bought a Boxster. Now I can run 285 out back, and 255s up front. Problems solved. All that is missing is an LSD and more power just like the 914, one of two of these items will be solved shortly. The other will be solved when the right car pops up on coparts (IMG:style_emoticons/default/shades.gif)

[mskala]

I'm not sure of your goal, here. Is your desire wide tires? Or
60-series tires (balloons)? Or do you really just want 911R rims?
Or do you love fabricating stuff just to say you did it?

So my comments may or may not be helpful. On my -6, I can
run Hoosier A7 205/45/16 on a 7.5" rim. It does not have flares.
The fender lips were flattened and pulled on a bit, and I am
using about 2 degrees negative camber. They have rubbed the
paint off the inner fender over time. I needed to get the spacers
right, and I have them in 3mm increments.

Before I had hoosiers, I video taped my suspension with other
racy tires, and like Andy said, they move a lot under side loads.
If you have good paint you don't want to destroy, give yourself
1/2" on each side. The 914 is great if you have plastic bushings,
since you can disconnect the shock and move the arm up and
down as far as you want to check the static fit.

In my opinion, you will never be able to fit the tires you're showing
without fender work.

I don't understand what the trailing arm width has to do with
fitting tires, the stock ones will accept a wide wheel in the location
it needs to be.

Rather than fabricate arms for no reason, you can just get some
Fuchs and have them widened on the inside, and use appropriate
spacers. That has to be cheaper and easier than custom arms,
and probably nobody will will be able to tell.

[mepstein]

Pete - I don't think you will get wider tires on the car without messing with your fenders in some fashion. In addition, the higher aspect ratio tires will always move more side to side and need more room to keep them off the fender. Ive seen a couple 914's and 911's burn through the paint on the fender from tires that "just fit".

[horizontally-opposed]

^ Several people have narrowed the trailing arms. I've had 205/60s and 205/55s in my stock rear fenders over the years with no issue. Others have gone up to 225/50R16 or 225/50R15 in stock fenders "with a bit of work." That work has varied. There are a number of threads.

215/60s are hardly "balloons," as that's the factory aspect ratio/overall diameter for all 15-inch applications. I happen to love the bulging sidewall with 215/60—but it's a matter of taste as 50- or 45-series rubber looks incorrect on these old cars. Again, a matter of taste/preference.

Agree on dynamic clearance, and well aware of that phenomenon, but feel that can be dealt with on the fender side and a wheel spacer. Trailing arm/brake line clearance was a bigger problem when I did the test fit, so it would be good to address it.

Trailing arm question came after reviewing threads of others' experiences in sneaking more rubber into a narrow body car. Many of them narrowed the trailing arms, particularly with wheels that tuck the tire inward with the 911R offset (my preference), which I believe is preferable as an offset to a standard 15x7 Fuchs—both technically and visually.

Finally, trailing arm question is prompted by the idea of paying for a second round of work on my trailing arms. By the time you narrow a pair, adapt 911 e-brakes, add new bearings, etc, one begins to wonder if you want the same old boat anchor—and if you're alone. Curious if Dave Darling remembers who built/offered/canceled the blade type arms with camber/toe adjustment at the rear of the arms. Unsprung weight is always nice to get rid of, too—and I know several people building 914s that might be able to justify a better option for the rear arms. Perhaps the economics/demand is different now than it was then—but the hours involved in reworking old trailing arms may help offset the cost of something better.

The right design should have merit regardless of what wheels are used. If it provides more tire clearance on the inside, well, that's a boon.

[horizontally-opposed]

Pete - I don't think you will get wider tires on the car without messing with your fenders in some fashion. In addition, the higher aspect ratio tires will always move more side to side and need more room to keep them off the fender. Ive seen a couple 914's and 911's burn through the paint on the fender from tires that "just fit".

^ Totally agree. This project, if it happens, will require a mix of things to sneak them in. But it's been done before.

[Chris914n6]

I have a 225/50-16 stuffed in the rear. I ran out of room between the sheet metal way before the arm could be an issue.

2nd thing... why would I ever want an oversized 215/60-15 with huge sidewall bulge?

On factory 16x7s, right? I have seen it done a few times. I'm more interested in getting the tire inboard on a 911R-style wheel, as I want to stay with 15s and the "narrow body" look.

185/70R15 or 195/65R15 front and 215/60R15 are the correct spec with the right overall diameter for a lot of Porsches—from the 1973 911 Carrera RS through Carrera 3.2s and 944s of the late 1980s. Good setup, several performance tires available, and period correct looks. There's a lot to like about factory tire sizes—and now there are some good wheel choices as well, ready to mount for similar or less money than "normal" Fuchs that need to be restored and a lot less than previously unobtanium 911R wheels.

https://tremotorsports.com/exterior/fuch-st...deep-6-7-wheels

Stock wheels & tires, for a Boxster (IMG:style_emoticons/default/biggrin.gif)
With spacers I think I ended up at Fuchs 911 offset and a bit of camber and rolled the fender.

I think I test fit a 215/60 on a 7x15 cookie from the 944 set I bought. Billowing sidewalls. Might as well call them pillow tires for a sleepy drive (IMG:style_emoticons/default/laugh.gif)

Found it. Silver cookie is a 6". I recall the 7" rubbed or was otherwise not worth using for donuts.

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611718641.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611718642.2.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611718642.3.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611718642.4.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-431-1611718642.5.jpg)

For comparison wide 205/55 on a 7x16 911 Fuch spec. Basically the same as my Boxsters.

[horizontally-opposed]

Silver cookie setup looks good to me. (IMG:style_emoticons/default/chowtime.gif)

As for pillows…  (IMG:style_emoticons/default/biggrin.gif) yeah maybe for all-seasons. But 185/70 front & 215/60R15 rear was standard for a 1973 Carrera RS while 195/65 front & 215/60R15 rear is standard for a 911 SC and Carrera 3.2. So that's a pretty attractive "maximum" setup for a narrow-body 914 with 200-250 hp—and Avon CR6ZZ are available in those sizes and were available from Roger Kraus Racing in three compounds last time I bought a set of 185/70s. Pirelli P6000 and CN36 are available in those sizes, too—and the revisions might accept 225/50R15 rears as well, which opens the door to Toyo RA1s and other interesting options if the car ever sees a track again.

It's going to take some work, but others have done it—on both narrow 914s as well as narrow early 911s—and whatever the work…it's a lot less work than GT flares and painting both sides of the car. Figure it can be pulled for now, and perhaps redone to a higher standard with the next paint job. Need to put some more miles and rock chips on this one first. (IMG:style_emoticons/default/smile.gif)

[Chris914n6]

I have a set of 225/50-15 on Fuchs I've been wanting to trial fit. Will be at least a week before it stops being cold and wet.

Also, I can spin my 225s in 2nd with 200hp, so 215 isn't going to change anything from 205.

So really, that's alot of work for 1/2" just because Porsche did it on the bigger 911 & 944 in the 80s.

[mskala]

I wasn't trying to judge what you're doing, whatever you want it's great.

Note one other thing; maybe you already know, but a wider wheel makes
the section width of the tire wider also. The 911R 7" rim is 49mm offset
and Fuchs 6" rim is 36mm offset, so the outside of the rim will be in
the same plane when mounted. So there is no benefit to using 911R rims
(if the tire will mount safely, which 225 or less will.)