Almost All You Ever Wanted to Know about..., Rear Hubs and 5-Lug Conversions Options

[Eric_Shea]

There’s been a lot of questions lately about 5-lug conversions; What hubs to use? Can I use a standard -4 hub? Should I use the early -4 hub with the bosses? Should I get expensive 914-6 stub axles and use an early 911 hub? How about the 944 hub conversion? All great questions; the idea behind this post is to put it all together in one thread with a few pictures.

First, let’s take a look at the two basic styles of -4 hubs. The first series of hubs for a 914 were on the 1970 cars. They were a little different as the factory had bosses formed in the casting for not only 4-lug configuration but 5-lug as well. The 4-lug bosses were predominant as they sat at 11.75mm while the remaining 5-lug bosses sat at 7.5mm. These are very popular with people who are doing their own conversion to 5-lug because they simply had to take them to a machine shop and request a 5x130mm pattern.

Here’s a picture of an early 1970 -4 hub that has been drilled for the 5x130mm pattern (courtesy Mike Ginter). These hubs have been replated to make them shiny new (IMG:style_emoticons/default/wink.gif)



The following is a picture of the standard -4 hub that you will find on most cars. From MY 1971 on, all 914 hubs looked like this.



There are basically three things that can be done with these “914” hubs.

1. If you have the early hubs you can, as above, take them to a machine shop and have them drilled to a 5x130mm pattern.
2. If you have a later hub you can take it to a machine shop and have it spot faced (where they make the stud surface level) and drilled to the 5x130mm pattern, and
3. You can have them spot faced with the 5x130mm pattern, have ring bosses made up to bring the stud engagement back up to the 11mm depth. Press the studs in and weld the bosses on.

I think all are good choices. Regardless of what you hear out there, I’ve yet to see a -4 hub that’s been "properly" drilled fail. I’ve seen one picture posted here of someone who basically drilled out their hub with a hand drill and didn’t spot face it. The studs worked loose and buggered everything up but, I’ve never seen one done right fail.

I’ll add to that; I’ve never seen a stud fail. You can purchase inexpensive studs from EMPI at www.cip1.com. If they’re installed properly they will probably outlive you. I do like the factory Verbus studs because of full thread engagement and “consistency”. They are extremely consistent across all sizes and various studs in a batch. If you want custom length studs Porsche has probably tried them all on various vehicles so again, Verbus will be your only choice if you are using adapters etc. Be prepared… they are expensive. Some coming in at $10-15.00 EACH! (IMG:style_emoticons/default/ohmy.gif)

[Eric_Shea]

Those expensive studs definitely aren't '10.9' strength anymore if they were in there when welded.

I understand the concern but, to harden steel it is heated to a red glow (which the studs never were) and quenched in water or oil (which the studs never were). It this point they would be extremely brittle.

To anneal (temper or soften) it's heated to just over 1400°F and then slowly cooled for 20-40 hours at a very consistent and steady rate to soften. This would reduce the hardness “a very little” and the brittelness a lot.

I think it’s safe to say the hardness of these studs is hardly affected.

If the rings were welded prior to the studs being pressed in they would tend to warp.

Regarding balance: The relatively slow rotation of this centered mass will not be affected. Or so I’m told. After two year of making them, I’ve yet to be told otherwise by people who have them on their street and track cars (IMG:style_emoticons/default/wink.gif)

[smdubovsky]

To anneal (temper or soften) it's heated to just over 1400°F and then slowly cooled for 20-40 hours at a very consistent and steady rate to soften. This would reduce the hardness “a very little” and the brittelness a lot.

I think it’s safe to say the hardness of these studs is hardly affected.

Tempering doesn't require a slow cool (its not quenched either). Its done after the original hardening w/ quench (sometimes the quench is air depending on the alloy - and Im sure you know all this, but others might not) Annealing is the only process that requires a very specific cooldown rate though the critical temp zones. Heating the steel will have SOME effect on temper. W/o knowing the alloy and actual temp reached, none of us know the extent of that effect. I was just staying it would be safer for the studs to not have them in there when welding (esp in todays litigious society!)

If the rings were welded prior to the studs being pressed in they would tend to warp.

Agreed. Thats why I said to bolt, weld, and THEN re-spotface them;)

Just trying to offer suggestions/alternatives. No disrespect intended. I didn't say a THING about your welds like *cough* BRAD *cough* (IMG:style_emoticons/default/biggrin.gif) (BTW, Brad has no room to speak there. A monkey on crack could have made the welds on their spec boxster cage - I already gave them shit about that one;) I'll say no more.

Best,
SMD