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

[mepstein]

If a custom Wiedman wheel takes two Fuchs, cutting, welding and finishing to make the end product, I'm guessing 300 each wheel, 400 to cut and weld, 300 to finish, 50x2 to ship each way. $1,100 + per wheel - My guess.

Probably about right. Harvey can likely widen my deep sixes without refinishing the fronts, but not sure I want to cut them.

Or one can just buy these, new and ready to go, for $500ea:
https://tremotorsports.com/exterior/fuch-st...deep-6-7-wheels

Selling a set of 15x6 flat Fuchs that are less than perfect would go a long ways or even cover a set of these.

There are also these:
https://www.stoddard.com/91136102011-rpb.html.html

From everything I can see, these are high-quality wheels, made for rallying and circuit racing. $435-500ea seems strong value to me.

It's tough to put fake Fuchs on your car once you have real ones. They look similar in pics but not so good in real life. And most are heavier.

[horizontally-opposed]

It's tough to put fake Fuchs on your car once you have real ones. They look similar in pics but not so good in real life. And most are heavier.

Agree with your logic (as usual), but two things:

1) These aren't like the Fachs of the past, in quality or "almost" appearance—or, for that matter, focus on appearance and cheap cost. The Group 4s, in particular, look very close (probably close enough for me…still mulling having Harvey widen two of my 15x6s—but that brings up other questions).

2) My research indicates they're within a pound of forged Fuchs, and made by companies that supply rally wheels—so they appear to be quite strong. One can argue the merits of new cast 15s vs 50yo forged 15s with unknown # of heat cycles, impacts, etc. til the cows come home. I can see it either way, and it's probably six of one, half a dozen of the other.

Or one can look at it more simply: I'd rather have the tires I'm after on good (or good enough) wheels than be stuck with tires I don't want on real wheels.

[stownsen914]

Still think 986 wheel carrier idea from Chris has legs. Someone has pointed out that it has Weissach Axle geometry, but that's passive/active through the arc and I am not sure it matters if the carrier is literally just a carrier and rigidly attached to a trailing arm. Someone else pointed out that machining off the 986 carrier's strut mount may affect its strength, something that definitely has to be considered, but again the right trailing arm could account for that—and provide a lower mount for the 914's damper—maybe height adjustable for lowered cars?

So everything comes down to the trailing arm ...

I'd actually say it comes down to the trailing arm and also WHERE you attach it to the chassis. The relocation kits I've seen are an improvement over stock, but as far as I know they still assume a stock trailing arm. If you're building a custom arm anyway, there is a lot of improvement to be made by moving the pickup points around (not just moving them upward). It would need to be modeled to do it right. There are a few suspension analysis programs out there. I used susprog, but I believe there are others. Some of the changes that gave me the results I wanted were not intuitive at all. And of course there would be a lot of cutting and welding involved once you design it.

Scott

[rick 918-S]

I have a question. Does anyone think we are pushing our suspension and chassis design in spirited street driving beyond the design limits?

I have never added chassis stiffeners or even anti-roll control to my Alien. (IMG:style_emoticons/default/assimilate.gif) I drive the hell out of it. I have to admit the torque kills the traction. I can throttle steer the car even with 255/50/16's on 9's on the rear. Maybe it's all the years of winter driving or something. (IMG:style_emoticons/default/screwy.gif)

I guess I am wondering out load about the amount of re-engineering of a really good stock design. I am of the mind that on a narrow body car the design allows for a manageable spirited driving experience. Even on track day.

When I did the 7 of 9 (IMG:style_emoticons/default/alien_2.gif) I never felt I needed to do anything other than be sure I was in the right gear to stay in the torque zone. (narrow, factory anti-roll, 2.0 FI. Lightened flywheel) The lightened flywheel allowed for faster spin up but killed the inertia.

I agree it would be nice to have a low cost solution to trailing arm clearance. But my seat of the pants tells me we are discussing an option that would provide very little benefit for a cost well beyond a set of custom wheels.

I am all in for a low cost nip/tuck on the trailing arm though. Simple 914 solution to increase the foot print without the Rube Goldberg approach to modification for the sake of saying we did something.

I understand the desire for wanting more. The conversation started out as the need for tire clearance. I am wondering with the right compound on track day if the narrowed stock arm would be enough. Lets face it. I am not sure a redesigned trailing arm will stop the throttle lift spin condition when corning too hot. LOL! I think that is a bigger problem.. (IMG:style_emoticons/default/happy11.gif)

Great topic though. Just goes to show how great these cars are when we have to debate the benefit of changing something from the original design. (IMG:style_emoticons/default/beerchug.gif)

It is also a discussion on unsprung weight. Question: Is there always benefit in reducing unsprung weight? I feel like I should know the answer but alas I am just an old hot rod guy that fell into the seat of a 914 and never had a desire for the old iron again. (IMG:style_emoticons/default/wub.gif) (IMG:style_emoticons/default/driving.gif)

[mepstein]

Pete - Would adding an LSD to your trans help you.

[horizontally-opposed]

I have a question. Does anyone think we are pushing our suspension and chassis design in spirited street driving beyond the design limits?

I have never added chassis stiffeners or even anti-roll control to my Alien. (IMG:style_emoticons/default/assimilate.gif) I drive the hell out of it. I have to admit the torque kills the traction. I can throttle steer the car even with 255/50/16's on 9's on the rear. Maybe it's all the years of winter driving or something. (IMG:style_emoticons/default/screwy.gif)

I guess I am wondering out load about the amount of re-engineering of a really good stock design. I am of the mind that on a narrow body car the design allows for a manageable spirited driving experience. Even on track day.

When I did the 7 of 9 (IMG:style_emoticons/default/alien_2.gif) I never felt I needed to do anything other than be sure I was in the right gear to stay in the torque zone. (narrow, factory anti-roll, 2.0 FI. Lightened flywheel) The lightened flywheel allowed for faster spin up but killed the inertia.

I agree it would be nice to have a low cost solution to trailing arm clearance. But my seat of the pants tells me we are discussing an option that would provide very little benefit for a cost well beyond a set of custom wheels.

I am all in for a low cost nip/tuck on the trailing arm though. Simple 914 solution to increase the foot print without the Rube Goldberg approach to modification for the sake of saying we did something.

I understand the desire for wanting more. The conversation started out as the need for tire clearance. I am wondering with the right compound on track day if the narrowed stock arm would be enough. Lets face it. I am not sure a redesigned trailing arm will stop the throttle lift spin condition when corning too hot. LOL! I think that is a bigger problem.. (IMG:style_emoticons/default/happy11.gif)

Great topic though. Just goes to show how great these cars are when we have to debate the benefit of changing something from the original design. (IMG:style_emoticons/default/beerchug.gif)

It is also a discussion on unsprung weight. Question: Is there always benefit in reducing unsprung weight? I feel like I should know the answer but alas I am just an old hot rod guy that fell into the seat of a 914 and never had a desire for the old iron again. (IMG:style_emoticons/default/wub.gif) (IMG:style_emoticons/default/driving.gif)

So many good inputs and gut checks here. Maybe someone can point out the blind spots, but I see them falling into three primary categories:

1) Handling dynamics
2) Engine power output and delivery characteristics
2) Driver skill/style/preferences

That last one is a biggie. Actually all three are.

Agree this discussion only highlights how great these cars are—and it's generally accepted that less unsprung weight is better (so long everything is strong enough, etc). This discussion has moved me away from the drive to reduce weight on the trailing arm—though any savings, even minimal, would of course be nice—if other objectives can be met.

This thread has me thinking the better/more likely place to reduce weight—both unsprung and rotational—is the steel caliper and one-piece cast-iron brake rotor. The only reason I've stuck with the [/u]hefty stock calipers is to have an e-brake, and all these photos have reminded me just how smart the 911/986/etc drum-brake e-brake is, by doubling the use of the inside of the brake rotor's "hat." Looking at the e-brake on the 986 carrier, it really doesn't look like a lot of extra weight. I also wonder if an aluminum hat is mechanically viable with a drum-type parking brake?

Another option for an e-brake is the RSR type clamp offered by Zuffenhaus alongside their insanely cool and period-right RSR/917-style finned calipers, but I am afraid these are simply outside my budget against 986 calipers…especially used/refurbished ones. And I'd switch to four-piston 986 calipers in a second, as I've also learned one of my other preferences: I prefer a sports car that's "over-braked" to one that's "under-braked," and have run into fade in some pretty serious machinery. You can always drive around it, but I don't like serving my brakes' needs—or even thinking about them—when pressing on.

[horizontally-opposed]

Pete - Would adding an LSD to your trans help you.

Doesn't really affect my interest here, as the desire to go to 185/215 is about stability and handling dynamics in all conditions over an ability to put the power down. The latter is controlled with my right foot, and has been a non-issue so far.

An LSD is on the list, however, for whenever the transmission comes apart next as a good one does offer some stability/predictability advantages.

[rick 918-S]

Here is a thought to reduce unsprung weight. What about a smart conversion to inboard brakes like the Jags have. (IMG:style_emoticons/default/idea.gif) This may be an easier conversion than anything we discussed to date.

[mepstein]

I'm not sure what Pete has on his car now but if they are ATE steel calipers then going to 3" Brembo or 3.5" S calipers and PMB aluminum 914-6 calipers would save 8-10lbs.

I know the PMB rears are nla but there are always parts available if you look and ask.

I am still in the belief that front suspension is 75%, rear 25% so tuning the front suspension is more important. That's from my bike riding and racing experience so I realize I have a huge knowledge gap for cars.

[ClayPerrine]

Here is a thought to reduce unsprung weight. What about a smart conversion to inboard brakes like the Jags have. (IMG:style_emoticons/default/idea.gif) This may be an easier conversion than anything we discussed to date.

There are at least two problems (that I can think of) with inboard brakes....

1. U-Joint/CV Joint Windup. It puts more load on the CV joint due to braking, and that causes windup in the drivetrain.

2. Heat Dissipation. It adds heat inboard where there is less airflow, causing both brake fade and possible other heat induced problems with the transmission.


I think the benefits of less unsprung weight are outweighed (pun intended) by the drawbacks. If it were a huge benefit, we would be seeing inboard brakes on a lot of modern performance cars.
Clay

[rick 918-S]

Here is a thought to reduce unsprung weight. What about a smart conversion to inboard brakes like the Jags have. (IMG:style_emoticons/default/idea.gif) This may be an easier conversion than anything we discussed to date.

There are at least two problems (that I can think of) with inboard brakes....

1. U-Joint/CV Joint Windup. It puts more load on the CV joint due to braking, and that causes windup in the drivetrain.

2. Heat Dissipation. It adds heat inboard where there is less airflow, causing both brake fade and possible other heat induced problems with the transmission.


I think the benefits of less unsprung weight are outweighed (pun intended) by the drawbacks. If it were a huge benefit, we would be seeing inboard brakes on a lot of modern performance cars.
Clay

Ya, you would need to change to real U joints like the Jags and Corvettes. I see the issue with the CV's

[horizontally-opposed]

I'm not sure what Pete has on his car now but if they are ATE steel calipers then going to 3" Brembo or 3.5" S calipers and PMB aluminum 914-6 calipers would save 8-10lbs.

I know the PMB rears are nla but there are always parts available if you look and ask.

I am still in the belief that front suspension is 75%, rear 25% so tuning the front suspension is more important. That's from my bike riding and racing experience so I realize I have a huge knowledge gap for cars.

^ Yep on steel ATE rear calipers. Have 3' Brembo aluminum calipers up front that I guess could be moved to the rear if there are 911, 986, or RSR-type e-brakes, leaving room for a caliper upgrade up front. Would need to research what would be balanced with the Brembos if they move to the back. Or just go with a f/r system that's matched, whether 986 or 930.

But first, need to know what I am mounting said rear calipers to.

Losing 8-10 pounds would be worthwhile, and might be increased with the right rotors. I had a race shop drill my "hats" last time around, partly to cut a little weight but mostly for the fun of it…as it's a little detail I like on the 917s (not to mention modern Audis…with the common denominator being Piëch). Could a pound or two be shaved from each trailing arm? Or 3-5? Or maybe new arms would be even steven or even a bit heavier but offset by aluminum calipers and new features. Too early to tell, but a bit here and a bit there can really add up—and a lightweight battery plus 10-20 pounds out of the rear suspension and brakes might offset 30-50% of the weight gain with my six conversion in roughly the same area of the car, and I do miss the light, tossable feeling of my car as a -4.

Agree on importance of front suspension, but might put it closer to 50-75% (not sure where it falls, but I'd put it closer to 50%). Believe me, I have ideas for the front suspension, too. (IMG:style_emoticons/default/wink.gif) The difference is: Great options exist and are readily available—it's just a matter of budget…and figuring out what it will be paired to in the back!

[horizontally-opposed]

Here is a thought to reduce unsprung weight. What about a smart conversion to inboard brakes like the Jags have. (IMG:style_emoticons/default/idea.gif) This may be an easier conversion than anything we discussed to date.

There are at least two problems (that I can think of) with inboard brakes....

1. U-Joint/CV Joint Windup. It puts more load on the CV joint due to braking, and that causes windup in the drivetrain.

2. Heat Dissipation. It adds heat inboard where there is less airflow, causing both brake fade and possible other heat induced problems with the transmission.


I think the benefits of less unsprung weight are outweighed (pun intended) by the drawbacks. If it were a huge benefit, we would be seeing inboard brakes on a lot of modern performance cars.
Clay

(IMG:style_emoticons/default/agree.gif)

Yep to all that.

[mepstein]

A light battery is definitely low hanging fruit.

[Chris914n6]

996/997 rear susp. Would make sense to fab a steel subframe that fit under a 914 that had the wheels tucking appropriately. Use the 914 axles if possible. Welding to the chassis would make it much stronger back there.

Remove the no longer needed inner trailing arm mount and a Boxster engine should fit. But that is a whole different ball of wax. But then you could likely do a Porsche -6 swap for $10k all in... (IMG:style_emoticons/default/idea.gif)

Ignore the red circles... best pic I could find quickly.
(IMG:http://www.914world.com/bbs2/uploads_offsite/9lf.de-431-1612559439.1.jpg)

[rgalla9146]

I love the idea.
......those upper links will extend well into the trunk/wheelhouse.
We're looking at the drivers rear hub from the roll bar down
.....but not exactly a DIY solution

[horizontally-opposed]

996/997 rear susp. Would make sense to fab a steel subframe that fit under a 914 that had the wheels tucking appropriately. Use the 914 axles if possible. Welding to the chassis would make it much stronger back there.

Remove the no longer needed inner trailing arm mount and a Boxster engine should fit. But that is a whole different ball of wax. But then you could likely do a Porsche -6 swap for $10k all in... (IMG:style_emoticons/default/idea.gif)

Ignore the red circles... best pic I could find quickly.
(IMG:http://www.914world.com/bbs2/uploads_offsite/9lf.de-431-1612559439.1.jpg)

I can see it for those willing to cut up their chassis and/or go to something other than a Type IV or 901 flat six, but will probably push the wheels well outside of the fenders outside of a narrow body 914 and require either modern wheel offsets even with M471 flares.

I've been thinking about your idea with the 986 carrier ever since you posted it, and the more I think about it, the more it makes sense. I even looked at whether optional lateral links could be adopted somehow, maybe off of a "saddle" added to or above the 901 or the transmission mounts, but it looks like an unnecessary complication and not sure the geometry would work out anyway? And I'm not sure the 914 suspension concept needs a rethink, though? It works well enough to have put these cars into the winner's circle for decades, and their handling is (rightly) legendary. Its execution, to a price, can be improved upon, however—just as with older 911s.

Anyone taking this on as a vendor needs to maximize market interest…and that's going to be for something that a) bolts on, b) doesn't require unibody mods, and c) is true to factory concepts and price sensitive (cap is somewhere around or a bit more than "the works" + 911 e-brakes on an old pair of 914 trailing arms).

[ClayPerrine]

I did the research on putting a Cayman rear suspension under a 914.

The track is about 6 inches wider. So you get 3 inches on each side. A different offset wheel (A Cayman wheel) would probably fit with no spacers under a narrow bodied car. For a flared car, just use a wheel with the correct offset.

The shock towers on the rear of a 914 lean forward, but the Cayman ones stand straight up (at least in the front/back reference plane). So you would have to remove the current shock towers and replace them with the ones from the Cayman chassis. The mounts points on the chassis would have to be removed from the Cayman donor, and welded in the correct location on the 914. The trailing arm mounts would have to be completely removed, and the mount for the front link added. From pictures, it looks like it would come out right where the trailing arm mounts are located, so maybe that could be salvaged. You would also need custom park brake cables, but those are not a big issue to get made.

If I did this, my car would have an advantage. I just remove the custom trans mount and support the trans with a jack stand. Then bolt the factory Cayman trans mounts to the trans, and bolt the other ends to the Cayman subframes. So now I would have references for the proper location of the chassis mounts.

It's a lot of chassis mods for something of unknown gains. How would it work with a stock 914 front suspension?? Would I need to go to coilovers and an RSR style suspension in the front to take advantage of it?

I have been thinking about this for years. For some reason, it intrigues me. But I think I am going to keep the stock 914 rear suspension for now. I have other things on my car I would like to finish before I even consider something of this magnitude.


Clay

[914forme]

Pete - Would adding an LSD to your trans help you.

Doesn't really affect my interest here, as the desire to go to 185/215 is about stability and handling dynamics in all conditions over an ability to put the power down. The latter is controlled with my right foot, and has been a non-issue so far.

An LSD is on the list, however, for whenever the transmission comes apart next as a good one does offer some stability/predictability advantages.

Pete, PM sent.

[Dave_Darling]

Curious if Dave Darling remembers who built/offered/canceled the blade type arms with camber/toe adjustment at the rear of the arms.

You forgot the underscore in my user name, so I didn't get the notification.

Anyway, I do not remember who made the arms. I think it was on Porschephiles back in the 90s, and what I remember is:
- They made tubular trailing arms, not blade-style
- Adjustment was out at the wheel end
- They didn't sell, and were abandoned
- It was done at least a few years before I heard about them, so possibly in the 80s

That's it. Sorry I don't have any more information.


I'd be worried about the strength of blade-style arms. There's a lot of torsion going through the 914 arm, and a flat piece of metal will bend a lot in torsion. Multiple blades can deal with that to some extent, or a blade to carry the loads in one direction with an I-beam or a box to carry the rest. (Note that the 911 spring plate for the most part only carries the torsion bar loads. The cast arm carries the twisting loads and such.)

Sounds like this is a lot of work for little benefit, frankly.

--DD