front brake caliper help

williamm · 05-22-2002, 06:32 PM

So I've upgraded my 1970 914-4 front suspension with the turbo tie rods, 1973 struts, ball joints and rotors (with centering disk). And now I need help deciding on calipers. I have a set of the original 1970 calipers that were rebuilt and only have 50 miles on them. The problem is, one of them has been modified with a grinder to fit the 1973 strut. Seems to work OK, and the other one is still original. My first thought was to grind the other one down, using the first as a template. Or I could try to find '73 style rotors (rebuilt). The BMW i320 calipers is another option, but they would need to be ground down according to the other postings. Also, any thoughts on the potential crude grinding method versus machining? I appreciate any feedback

scotty914 · 05-22-2002, 06:53 PM

you dont need to machine for pre 73 struts when using 320 i brakes

williamm · 05-22-2002, 07:05 PM

Thanks for the quick response Scott, but the struts were switched to '73 the variety. Also, the master cylinder is a new 17MM.

yoh!!! · yoh!!!'s Garage

Williamm... you stated that you swaped the struts - you now use 73 + type struts. If this is correct you will have to modify your brake callipers. In both cases (original or BMW 320i) you will have to machine 0.128'' or 3.1mm off the inside flansh.
According to my oppinion grinding them down is not the best solution. Even if you would spend some effort on measuring I would assume that it would be very difficult to do this job accurately enough. The outcome will most likely be that your brake pads will not be positoned paralell to the disks. The pads will wear uneven and the brake performance will be limited.
READ THE TECH ARTICLE FROM PParts!!!
Check also the postings on this topic. Lately some people had some creative ideas with four piston calipers from 240 Volvos and 2002 BMW. The 2002 BMW calipers will require the same machine work as those from the 320i...
Most people recomend to use a 19mm master brake cylinder when swaping to bigger brake callipers.
Personally I like the BMW 2002 idea because of the four pistons. It also seems like the 2002 brakes will not have pad overhang.

Patrick Koch

Mark Howard · 05-23-2002, 06:39 PM

I'm fixin' to do the turbo tie rod thing myself. How hard was it? Any hints for me??

williamm · 05-24-2002, 06:23 PM

The turbo tie rods were a good upgrade, especially since my tie rods were worn out. The steering is more precise and responsive. Installation was pretty easy. Separating the old tie rods from the struts was definately the hardest part. You can get a tie rod separator from Autozone with a $20 deposit, they take them back or you can keep it. Unscrewing the eye bolt from the rack and pinion was tedious, since space is limited. Jack up your front end as high as you can and use a box end wrench to slowly work the bolt out. Putting in the new one was easier of course. Also, make sure to measure your old tie rods precisely so you can adjust the turbo ones correctly.

williamm · 05-24-2002, 07:14 PM

So I decided to machine down the 1970 style caliper to fit the 1973 strut because the caliper had been recently rebuilt. Unfortunately, the machine shop separated the caliper in halfs! I've heard that putting them back together without leaking is very difficult. Any hints on re-assembling them so they don't leak? Proper torque? Thanks

HMeeder · HMeeder's Garage

Haynes Manual page 113 figure 8:14

Torque first the inner bolts then the outers to 7 lb/ft, then repeat to 16 lb/ft. The longer bolts are the 2 inner ones. You could try to reuse the galley seals again, but I wouldn't.

Since the things are apart, why not do the whole rebuild? The kits run about $20 each and IIRC have the brake fluid galley seals. If course, you may have to temporarily put them back together in order to get the pistons out (see 'Brake Calipers stuck, stuck, stuck!' from about a week ago.)

Don't have a Haynes manual? Get one. It's not the best but since the the factory manual runs in the $300 range, it's gonna have to do. Actually, Haynes is pretty good, but the Brits who wrote it are a bit peculiar in their descriptions. It does have a Brit-to-American glossary.

I wrote a tech article here on the PP site about rebuilding the rear calipers, and many of the elements in it apply to the fronts, just ignore the references to the venting clearance adjusters and the P-brake actuator arm.

Good luck!