OT: Should I stay with drum or switch to disc?

[rsr911]

<font face="Verdana, Arial" size="2">Originally posted by debequem:
Unless you are going to race it or run severe duty, I'd stick with the drums.

However, if you are going to race it, I would just buy a 911 and sell the bug!

Or, if you really like that VW engine, buy a 912!

Okay, I am biased. ;-)</font>

Here is mockup of brakes I'm doing for a friends 911:



We are using 13" Wilwood Rotors and 964 calipers. For the track car I'm building (3.0 powered 1973 911) I'm going with 996 calipers and 14" rotors in front with 13" in back. Late model Porsche brakes are made by Brembo.

Back to the topic, I say discs front and rear if possible. The first time you have to panic stop you'll thank me. Besides that a bit of spirited driving will cause those drums to fade in no time. I can fade my '66 911's brakes with ease on some of the roads around here. Given that the Super Beetle and the 911 are of similar size and weight and both rear engined why not make adapters to run 911 brakes? I'll bet the bias is very close.

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-Christian D. Sokolowski

[This message has been edited by rsr911 (edited 01-13-2006).]

[This message has been edited by rsr911 (edited 01-13-2006).]

[abn]

And the first time he stabs the brakes and swerves in a panic and the ass end swings around because of improper brake balance...he may thank you as well.

I agree, four wheel disc brakes are better...Porsche Brembos are (until recently) the only "real" OEM brakes...and I'd wholeheartedly suggest their use. But the job doesn't stop (and shouldn't start) with just the disc install.

<font face="Verdana, Arial" size="2">snip&gt;
Back to the topic, I say discs front and rear if possible. The first time you have to panic stop you'll thank me. snip&gt;
[/B]</font>

[Norman Atkinson]

There is a correct and classical answer and I would agree that it may not be acceptable.

It starts and ends with insurance.
The insurance company has a proposal to insure a named vehicle type and specification. Having regard to this, it will quote for that vehicle which they understand is as near as possible to the vehicle which comes off the production line.
Again, it will expect wheels, tires and all the rest of easily modifiable things and service items to be still standard- as described in the makers specification.

In the event of a claim, the insurance company can refuse a claim on the grounds that they quoted for an unmodified car and only an unmodified car.

Hence, the drums, disks or whatever should remain standard.

Sorry to be boring- for once!

Norman

[3 Phase Lightbulb]

<font face="Verdana, Arial" size="2">Originally posted by Ron LaDow:
Adrian,
Not sure of your question. When I made half-shafts with CV joints, I just made sure they didn't run out of travel in the CV joints.
You have a lot of vertical travel; measure or calc the resultant linear travel for the full excursion and make sure the CV joints can not bottom.
Also, try to arrange it such that they are not absolutely straight in normal running. A bit of angularity prevents premature wear.
</font>

I've calculated the CV angular limits but I'm not sure what the correct distance between CV flanges should be.

For instance the CV joints/axles I'm using seem to work if the distance between CV flanges is between 21" and 23". This is because the CV joints slide inward and outward on the splined axle ends.. My 5-link design only pulls/pushes the CV joints in/out about 1/4" through-out the entire travel range because of the geometry of my 5-link system. I'm wondering if I should size my links so in the neutral (0 deg) places the CV joints in the middle of their spline travel, or should I just make sure there is plenty of play inward and outward throughout the travel range?

-Adrian

[Ron LaDow]

Adrian,
You can't rely on the CV joint to travel or slide on the spline; won't do it.
Check the joints themselves. Most all of them have a certain amount of axial travel built into them.
Make the shaft of a length so that the CVs will not bottom in their travel. If you have a max axial excursion of 1/4", it'll be a snap.
I've used the small ones (914 Porsche when I bought them) and the large ones (930P) CVs and both have axial travel.
Using ones that don't have that travel, the solution is a ball-spline in the shaft somewhere.
(Sure hope I'm answering the question)
Thanks,
Ron LaDow

[3 Phase Lightbulb]

<font face="Verdana, Arial" size="2">Originally posted by Ron LaDow:
Adrian,
You can't rely on the CV joint to travel or slide on the spline; won't do it.
Check the joints themselves. Most all of them have a certain amount of axial travel built into them.
Make the shaft of a length so that the CVs will not bottom in their travel. If you have a max axial excursion of 1/4", it'll be a snap.
I've used the small ones (914 Porsche when I bought them) and the large ones (930P) CVs and both have axial travel.
Using ones that don't have that travel, the solution is a ball-spline in the shaft somewhere.
(Sure hope I'm answering the question)
Thanks,
Ron LaDow</font>

Yup, you nailed it.. Sorry, I was thinking the CV joints were moving on the spline, but now that I think about it more, I do remember seing the CV cage w/balls inside sliding in/out of the CV housing.

I'm using 944 CV joints (Type 4, w/22 deg). I wanted to use 930 joints (25 deg) but I got a super deal on the 944s w/axles so I'll try them first.

"If you have a max axial excursion of 1/4", it'll be a snap."

That's where my question/consern came from. Becuase I only need 1/4", It's easy to get no binding with CV flange distances from 21 to 23" so I wasn't sure if say 22" is the best (in the middle) or would 21" be better (less wear on the CV?) or maybe 23" would be best? I'm not sure if it matters (That's basically my question).

-Adrian

[Ron LaDow]

Adrian,
Center the distance and let them float; best wear characteristics when they can find new places to run all the time.
That's also the reason to make sure they run a slight angularity in 'normal' conditions.
Added by edit:
There are only two sizes available. Yours were used in the 4-cyl. Porsches and every other sub-200#/ft application. The large ones take more torque.
Thanks,
Ron LaDow

[This message has been edited by Ron LaDow (edited 01-13-2006).]