I'm looking around to upgrade the brakes, and do a 5-lug conv at the same time. I read some stuff (including the Pelican article for 5-lug conv) and it seems like the options are to either replace with 911 parts or to use 914-6 parts. I've seen a couple of complete 911 front-rear suspension assy for sale at dismantlers and I think I saw a 914-6 setup somewhere.

Anyway, here's my questions:

One of the articles says early 911 rear-suspensions are direct replacement. Can you use a later than 71 911 REAR suspension? or does that require too much modifications?

Is there a difference in performance of the suspension (front&rear) between the 911 and 914-6 options?

Is it possible to install replacement Brembo/Zimmermann rotors and bigger calipers on the 914-6 assy (in particular front)?

What would be your recommendation for this upgrade?

Thanks,
Johan

911 rear suspension does not fit the 914. Some components can be used (hubs, brakes, axles, e-brakes) but it is not an easy swap - you can find some recent info here: 911 e-brake. The easiest way to get 5-lug on the back is to have your hubs redrilled. Another option is 914/6 rear stub axles and early 911 hubs. Next up is early 911 stub axles, axles, and hubs.

Then to the brakes - you can use 914/6 rear rotors with your stock calipers (slight trimming of the inside of the caliper is sometimes required). 914/6 rear calipers are nearly impossible to find, but that would be an option to give larger pistons. Other options are more exotic and require fitting of 911 e-brakes (non-trivial) or something custom assuming you need to retain your handbrake. If you don't then there are many more possibilities such as 911 rear calipers and 914 fronts on the rear.

914/6 front brakes are the same as 911, and if you are going to go to the trouble you may as well use later 911 parts. SC or Carrera are probably the ones you want to shoot for ('78 to '89). You can keep your 914 suspension and use just the struts/hubs/brakes from a 911. Be cafeful which struts you get, as factory Koni and Bilstein can only use those shocks as replacements, while Boge struts can use anything.

The only thing the other 911 components gets you is an aluminum crossmember (on later 911s) which in reality may not be better than the steel one, and the a-arms have a different torsion bar spline. The different spline allows you to get larger torsion bars from later 911s (so they are cheaper because they are used). You can buy larger torsion bars new for the 914 splines, so again this is of marginal benefit.

Finally, you need to deal with brake balance. 911 fronts with stock rears and the stock proportioning valve leaves way too much front bias. You can remove the valve and replace with a VW "T" fitting if your parts are well matched, or add an aftermarket valve to replace the stock one for improved adjustability and feel over the stock valve.

Excellent reply James! I've been researching this very topic for years and you have brought up everything i've learned in it's proper perspective in one well worded message.

Rick

do you have a lot more power than stock ? do you spend a lot of time on the track ?
if that's 'no' and 'no' there is marginal benefit to be had with uprated brakes. if you can lock the wheels at the end of the straight on the tires you have, there is little more to be gained.

914.6 front suspension -is- early 911 front suspension, down to the last nut, bolt, and screw, warts and all. James has covered most of the technical issues. it's not actually the crossmember, aluminum or not, that governs torsion bar fitment, but the A-arms (914.4 and .6 are dimensionally identical, save for that spline issue) and the height adjustor block that mounts in the crossmember. if you're looking at a track application the wider array of 911-splined torsion bar sizes may be a factor - otherwise you can probably get whatever you want and probably, you'll leave it that way when you're done.

there is -nothing- about 911 rear suspension that is compatible, as James has correctly said. the hubs, stub axles, brake disks and such are one avenue to 5-lug conversion.

there is no performance difference between 911-914.6 options, because 914.6 is the same in front, and the rears and completely different. if you go -too- new in 911 parts ("Carrera") you run into Porsche's newer front suspension with radically different hub placement.

you can go as big as you want on front brakes with 911 components. you can get struts with 3,5" caliper-mounting spacing and use the finned 917 calipers from the midyear 911 Turbo. they're astonishingly expensive and very heavy. if you have to brake a 3000-lb car from 200 mph all day long, they're the hot ticket, but if you're just trying to drive a 914/4 on the street, there are better places to put your money ... as big as makes sense in that application is probably the early 911 (914.6 - same) 'M' caliper or maybe the aluminum 'S' caliper (3,5" mounting - you need to know what you want when you buy struts) or (more likely) its cast-iron 'A' equivalent. it's hard to go bigger than 914.6 rear in back (not that it's necessary) without serious fabrication - or loss of E-brake, which most of us think is -ah - suboptimal ...

recommendation? THINK about where you and the car are headed, and deal with the ENTIRE car as a package, rather than approaching each subsystem as an independent modification opportunity. are you planning a big 6 conversion, or a V8? definitely more brake. are you going to be spending a lot of time on the track (not autocross - the big stuff?) maybe more brake ... but 914's are 'quick' because they are conservation-of-momentum cars - they use their superior roadholding to carry more speed through corners than most other cars can. most slow drivers are slow because they brake too much ...

Thanks for your honest replies. I plan to do a conversion, 6 or V8 - not decided yet - but I'm not building a track-car. I do like to let the ponies out though - feel the G-force - straight line or better even in the corners. To be honest I just want to make sure I can stop when 1) Granny comes from the hairdresser in her pink Cadillac and doesn't see my small car when she turns on the street in front of me, and 2) I didn't see that yellow 15mph sign that's partially hidden behind a tree. I'm being serious, experienced both situations on a motorcycle (fortunately didn't hit anything) and I noticed quite a couple of times that people either don't see my 914 or think I'll go out of the way since they have a bigger car.

Anyway, from your replies it seems like any upgrade to 914-6 or 911 brakes (whatever size) is adequate for what I need.

Thanks a lot
Johan

bigger/better brakes is but the tip of the slippery slope, since plus or minus a little, all they do is let you lock the wheels a little sooner. you need to get more traction - and you'll have a better selection of tires for wheels that come in a wider variety of sizes for 5-lug hubs. it's all part of a package ...

Bigger tires will definitely be part of the package - them GT flares look mighty good too. Thing I struggle with is the transaxle. I don't want to go to a 915 cause that's going to cost me my right arm and leg (the left arm and leg will already be gone). Looks though that the 901's with some upgraded items should be good for street non-abuse.