[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: Big Red Stuff 2

In a message dated 98-10-27 10:26:22 EST, you write:

<< Spacers are pretty common on some cars...especially older 911's, including
 >Turbos that need to clear the calipers.  The spacers really
>aren't_that_thick.  We've not seen failures with smaller sized wheel
> spacers.
Thickness isn't the issue, it's torque x 2 shear points.  Usually the shear
point furthest from the anchor fails.  Take a look at a car that runs spacers.
Look for the thread marks on the spacer holes.  Now add torque (and in your
case, you claim a lot).  For a car that will see differing cf most of it's
racing life, ProRally is the worst place to use them.

 > The point is, that an 11.5 rotor and the "compact" 4 pot did not
 > clear a 16,
 > but did the SQ 15's.  Just proceed with caution and homework.
>> Your spokes were simply too close to the caliper.  That's easily
>> alleviated...if you choose not to use spacers, then you're going to have to
>> find another solution.  A 5mm spacer would cure your rubbing problem

Not in this case Mark.  In the case of the Sport q brakes, they are too long.
The ends of the caliper hit the inside rim of the wheel.  Not a spacer issue.

> The wheel studs are 911 9/16th studs that have a 12.9 rating.  They aren't
> easy to sheer off...we had these on our Porsche 911 SCORE Class 5 car, and
> NEVER broke a stud.  Again, whether or not you choose to use wheel spacers
> is your choice.

Sure, just trying to talk you out of it, that's all.  See above comments
regarding differing cf and torque.  You could have a cf really high on one
wheel and almost none in all the others in a Rally.  Find who uses spacers in
rallying.  Exception not the rule.  I don't believe in them, period.  In
racing, it really is a bandaid.  You can buy Compomotives pretty cheap
(Panasports too) in just about any offset you want.  So why add another shear
point?  Again, this is a case where the wheel comes before the brakes.  I only
advocate it should be the other way around.  It makes sense, and it's safer.
> The pad on the big red and 928 caliper can't even cover the entire surface
> area, so the easiest thing to do is put the rotors on a lathe and cut them
 >down to a smaller diameter.  I've since abandoned the idea of the Porsche
The pad on the Big Reds covers all but the top 1/16 inch of pad.  This avoids
breakdown of the edge of the pad material.  Even when I use 13.5 rotors, I
raise the caliper up to the Porsche design.
 > Get your own hats machined Mark.  Then you can get it the way you want it.
 >>We've considered it, but it's an expensive proposition.  I'd like to see if
>> there's any other shallow hats available first. My dad's friend Andy
>> Porterfield (owns Porterfield brakes) is trying to find us a solution.

It's not cheap.  But I'm going to convince you one way or t'other, not to use
those spacers.  :)

> I respect your opinion, but we don't feel there's much of a strength issue
>with a small spacer.  Our opinions simply differ on this issue.  Also note
 >that the wheel stud diameter on the GLH is pretty small, and I'm not sure
 >that the strength rating is as high as the Porsche studs.
May want to check into that first.  Mark, do what you want.  I'm not
lecturing, only trying to give you some heads up.  Find who uses them on the
Rally circuit and why they specifically don't.  You shouldn't be the first one
to use them.  There is too much btdt in regards to failures in rallying.
Bottom line:  A spacer "adapts" one wheel to "fit" something else.  Do it
right the first time, you adapt your wheel offset to fit your

My .02