Is this really a sensible option?

speedo · speedo's Garage

Great feedback on the bolt-up swap of a 73T to a SC front... struts-hub-caliper-rotor for a 3 ltr conversion, thanks everyone.. While looking around to find the complete package at a reasonable price, I ran across someone offering a BMW 3" ctc caliper replacement. Apparently the caliper uses the existing 73 strut , hub and rotor, and I'm told provides the same increase in braking performance that the SC upgrade would....but obviously with less money and work. I have no reason to question the individuals ethics but want to know if anyone has heard of this conversion and/or used it. I'll let someone else go first.....is there any additional benefit to the SC upgrade....weight, materials, rebuild kits etc?

masraum · 02-04-2003, 06:54 PM

I was under the impression that part of the upgrade process was getting bigger rotors so they can hold more heat. If you go with the BMW calipers and use the same rotors, where is the improvement?

Todd Simpson · 02-05-2003, 08:08 AM

An SC and a '73T use the same vented 20mm rotor, so yes, you can upgrade the caliper and use the same rotor. The next upgrade is the Carrera 24mm rotors. I think the Carrera calipers are the "same" as the SC calipers, just wider to accommodate the thicker rotor. This is the setup on my '71T track car and the brakes stay MUCH cooler than my stock SC brakes used to get. Bigger rotor, much lighter car.

I don't have any other details on the upgrade you're looking at , but check out Bill Verburg's brake info here...

http://www.pelicanparts.com/MotorCity/wmv/brakes.htm

KTL · 02-05-2003, 08:20 AM

Are the BMW calipers fixed or floating calipers?

If they're floating, that's certainly not an upgraded in my opinion.

speedo · speedo's Garage

Its a fixed caliper that uses the stock rotor....argument is that it is a more powerful caliper. Obviously as pointed out using the same rotor is not going to dissapate heat any better...but I'm a street, not track person.

KTL · 02-05-2003, 08:52 AM

So i'd think the only difference you'll feel would be a change in the pedal effort, right? Nothing wrong with that. Just asking since i'm not certain.

I imagine the BMW calipers use a larger pad too?

zotman72 · 04:50 PM

Two things, first make sure you get the right BMW caliper. I remember about a year ago, I heard of this swap possibility. Supposedly from '76 320is. I went down to a junkyard, found 320i of that year and remove the calipers. Rebuilt them with an ATE kits and then realized they were for solid rotors! Sold them to a Pelican 914 pilot for $30 loss. Make sure the gap for the rotor will fit your ventilated rotors.

For PCA events, these brake calipers though made by ATE, are not Porsche OEM , therefore they can disqualify you for stock class events. In our region, RMR, adding these brakes would have moved me to an Improved class rather than stock in our Challenge Series rules. I suspect similar things in club racing but do not know anything about this. But the pads are about 35-40% larger than the M caliper ones.

Unfortunately for me, I am on the our RMR Challenge Series board so I would have been in untenable situation if my BMW calipers had fit and I did not declared them. I bought a used set of SC calipers from DART Auto and am quite happy. Do not get me started on how I finally got 3.5" brake ear struts for my 911.
HTH.

speedo · speedo's Garage

Bill , does that mean that upgrading to SC calipers would not have bumped me up to an improved class, but the ATE brakes would? Also , with your swap to SC stuff did you require any other mat'ls?

zotman72 · 02-06-2003, 07:37 AM

SC or A calipers are same size as S calipers but of made of steel rather than Al alloy. Because S calipers were available back in '72, the A are legit in RMR Challenge Series Modified class. But you need 3.5 spacing brake ears on the struts to deploy these calipers. Getting a set of SC front struts is one a way to address this situation.