Front rotor drilled to 5-lug pattern

[farleyd]

Hi, i am in the process of going to 5-lug pattern. I wanted to have my front rotors drilled to 5-lug pattern. But on my new 914/4 rotors, there is a hub-centric rim, that doesnt fit into my early 911 Fuch 6x15, whcih arent hub-centric, but lug-centric.

Any suggestions? Taking out material from the Fuchs? Putting spacers to fill the hub-centric ticknessess?

Also, if i drill my rotors, can i just have them threaded to 914 lug-nut pattern, and use my longer Fuch 2.0L alloy bolts instead of tappered sutds and lug nuts?

Thanks to all.

[roadtrp204]

First, you cannot rethread the rotors for lug bolts. If you look on the back side of the rotor you will see the metal is thick only in the four spots where the current holes are located. You will have to use studs.
Second, if they fit the early rotors do not have the centering hub. Otherwise a machine shop should make quick work of removing it from yours.
Chris

[farleyd]

Thanks for replying. In which way there is a difference in strenght between using tappered insert studs and nuts OR screwing alloy lugnuts?

You mentionned that the material was too thin to threaded, in my mind, the threaded part will be as thin in both solutions?

[Dave at Pelican Parts]

If you use bolts, the threaded area is only as thick as the thickness of the rotor at that point. With studs, the threaded area is all of the area that the nut screws in to.

Press-in studs will have shoulders on the back side that come to rest against the back of the rotor, which distributes the load a lot better. This assumes that the back side of the rotor is spot-faced to make them flat and perpendicular to the stud.

--DD

[farleyd]

OK. Clear. Then will the holes have to be threaded or not? If not, what size should they be to have the properly inserted? A bit smaller i guess.

In case of drilled/threaded holes, where i screw the alloy bolts, you said that the threaded thickness would be only the thickness of the material, right? Any potential danger? Even with Lock-Tite?

[roadtrp204]

When four lug rotors/hubs are drilled to a five lug pattern, only one of the original hole is reused. In the case of drilling and tapping four out of five bolts would have a potential of pulling the threads out of the thinner redrilled portion of the rotor.
!!Danger of wheel breaking off in a turn!!

You need to get 14mm studs that press in from the back side of the rotor. The holes are drilled slightly smaller than knurled shoulder of the stud. When pressed in the knurl crushes and creates a very tight fit. In addition, as mentioned by Dave the area where the stud is to sit needs to be machined to give the stud a straight and flat place to rest upon.
Chris


[This message has been edited by roadtrp204 (edited 11-08-2000).]

[farleyd]

Hi, i will have my front rotors redrilled and tapped with pressed wheel studs, on which lugnuts are gonna secure the wheels.

I ll be using standard Fuch 6x15 and CAPPED lugnuts. Can you tell me what lenght the studs should be?

Also, am i tapping 5 studs? 4 will be into new holes but the fifth?

Is the original threaded hole have to be smoothed to accept the fifth studs? OR
Am i gonna use my original 2.0L alloy bolt, thru the wheel into the original threaded hole?

Thanks, it is a bit confusing for a novice.

[roadtrp204]

I never really thought about what to do with the original hole. Anyone of the choices I assume would be safe and work. (1) use original alloy bolt; (2) thread a stud into it; (3) drill and treat it like the other four new holes. I like to keep things uniform, so my personal choice would be to drill it and press a stud into it.

To anyone interested I sent a copy of an article in June 96 European car to farleyd that explains the whole process in detail. Send me an email if you would like a copy.
Chris

[Ed Atkinson]

The drill size that is used for the pressed in 14 mm studs is 9/16"... Only use 14 mm studs for thia conversion and always use NEW rotors. New rotors will last quite a while and you avoid having to do it again!

[farleyd]

OK. Very usefull. I have of alot of suggestion going directly to 911 strut combo. CAn someone bescribe - or give me URL - about this process? Parts, instructions.
If i understood well, ill have 911 calipers - better brakes, already have ss line and 19mm master cyl.
So i keep my rack and steering, a-amrs, and just bolt strut? What is a strut combo consists of?

[Dave at Pelican Parts]

http://www.pelicanparts.com/techarticles/914_five_lug_conversion/914_five_lug_conversion.htm

The short version is that you can replace just the struts (the struts are the vertical piece that goes from the A-arm up to the shock mount), and that will include five-bolt front hubs, vented brake rotors, and larger brakes.

You can also replace the whole front suspension, including the steering rack, the cross-member (later 911 ones are aluminum, and are lighter and stronger than 914 ones), the A-arms and torsion bars, etc.

You can also go in between those two. However, the torsion bars, A-arms, and torsion bar mounts have to be swapped as a unit. The 911 and 914 torsion bars have different numbers of splines, so you cannot mix and match the bars or the parts that hold the bars (the A-arms and torsion bar mounts).

--DD

[farleyd]

Hi all, upon all my conversation on going from 4-lug to 5-lug, between spacers/adapters, redrilled front rotors, i have come accross a set of 1984 Carrera front strut assembly w/Bilstein. Can it be swapped (bolt-on) with a 914 front assembly? Or i have to go 1969-1973 era assembly?

Thanks.

[Dave at Pelican Parts]

Bolt that sucker up! Uhh, it might be a good idea to use the 914 A-arms if you want to keep the same torsion bars you already have. Otherwise, you can substitute the 911 A-arms and torsion bar mounts and use the 911 torsion bars.

--DD

[farleyd]

Hi Dave and all, it is incredible the amount of things i am learning in such a short time on that BBS.If only the learning curve was that steep at school, where i am teaching...

I will try to get that set-up.Even comes with the space saver tire.

Should i go up to all the front suspension,if i can have it? How much superior it will be against my stock 2.0L wout/sway bars?

[efeinsmith]

One possible "got-ya" would depend on the year 914 you would be putting the 911 strut into. The way the lower ball joint attaches to the strut changed between early (1972 and back) and late (1973 forward) 914's. But then, you'd probably want to replace the ball joint anyway when upgrading the front end. Either ball joint will attach to the lower A-arm, so get the one that matches the strut.

[farleyd]

My 914 is a 1974 2.0L. Will the 911 1984 Carrera front strut assembly is a bolt-on one?

[odie]

I think your looking at my '84 struts. I have a 1975 914 that I was going to install them on as a precursor to a V-8 conversion which may never happen. But my car has been in storage for 4 years (still fires right up). I've got another car which commands my attention for the forseable future so I thought I'd clean out my garage and pass them on to another 914 owner.

[Joe Bob]

Obviously the easiest but more expensive way is strut replacement with a 911 front end and you get vented rotors and bigger brakes in the baragin.

But if you go with a stud replacement, drill and press them in using oem Porsche studs. Have it done by a competent machine shop. In some cases, you may have to use a then spacer between the newly studded front rotor and the five lug Fuch wheel.

The stock 911 studs my be a bit long and the lug nuts will bottom out, unless you use open top nuts. There should be no problem on the rear as the stud will be going throught the rotor and the hub....

Good Luck.

[Bee Jay]

My front rotors are being redrilled by Dave at GPR right now. I should get them back soon. I'll let you know how it went.
Bee Jay

[farleyd]

Hi, i spotted an ad on Ebay saying that you could put 5-lug 911 912 solid rotors on the front of the 914 and therefore having 5-lug instantly! Is this true? USing stock 914/4 front calipers? Do the rotors come with stud installed?
Second, can i use 911 912 rear hub on my 914/4 rear splines and stock calipers?
I am very very very confused....