Re-Braking a TR3B

by Stan Seto

Follow these instructions at your own risk. The braking system on your car must function correctly to avoid serious injury; if you do not feel competent to do these modifications correctly, please either stick with the stock brake system or have a professional do the work for you.

Introduction:

It started with a stop…. A bad stop, the car halfway out in the intersection and everyone around, staring. Get on the brakes late after a long steady drive, pedal goes halfway to the floor and That’s What You Get! The ‘3 is an otherwise nice car to drive, accelerates well, runs through curves and corners without upset, it just does not STOP all that well. The bad stop got me thinking about improvement. Briefly considered rear discs, may still consider that, but in general more work than I care to get into. So what can be done in front??

Talked with Brother Russ who rebuilds Triumphs (TR Shop in Houston, TX). He sent me an article: Four piston brake caliper conversion for TR3 to TR6. Written by R. John Lye and Lee Janssen, it was published in The Vintage Triumph, Issue 76, available on the web from:

http://www.vtr.org/maintain/brake-conversion.shtml

The gist of the article (which concentrated on re-braking a TR6) was that this is not all that hard to do. The ingredients were brake calipers from a Toyota light truck (vintage 1979 to 1983), new brake lines, new bolts, some minor surgery on the dust shields and there you have it. I did have to read the article a number of times to ensure I understood the work to be done on the TR3 as opposed to that on the TR6, and ferret my way through the jargon and inverse thinking of the authors, but finally convinced myself I could do this.

So, what first?

Parts, availability, and cost! One Saturday morning I took off to an O’Reilly’s Auto Parts store near me (Auto Zone, KOI, Smyth, and other vendors were equally close), but in our TR outings, it seemed to me that O’Reilly’s always seemed to have what was needed. The lady at the Parts counter heard my request and started searching her online files (Diesel or non-diesel? Non-diesel), (Four-wheel Drive? Yes.), (What years? ‘79 to ‘83.)….. Well, there was one caliper part that carried through, so she pulled it up and it looked right. Price? - $42.00 and core charge, each. Brake lines? No, we don’t have those, go to Ohio Hydraulics. I knew where that company was. Called The Roadster Factory and asked for the STANPART number in the article, confirmed they were 12mm with SAE threads, and $9.95 each. TRF had some in stock. Ordered two new front brake lines for the ‘3.

During the week, went to Ohio Hydraulics, just off Kemper Road in Sharonville, OH. The brake lines are to be SAE fitting (7/16) and thread (24) on the end that attaches to the chassis and metric (10X1.0, inverted flare fitting) where it screws into the caliper. The Toyota caliper hose location was on the side of the caliper, so a 90-degree fitting was required. The Girling caliper on the car was a radial screw-in (straight down) so it can be straight at each end. Because I was not sure where the new caliper fitting was relative to the Girling caliper fitting, I made the decision to go with all new brake lines and slightly longer than the current. It was an OK decision and cost me about thirty dollars more than refitting the TRF lines, but rather too long than too short. Ohio Hydraulics could not find a metric fitting in a right-angle shape. We did find the fitting needed in an adapter. The final solution was an SAE fitting on one end of the hose, total length one inch more than the current hose, SAE right-angle fitting on the other end of the hose, and an SAE to Metric adapter.

Bought the calipers and a regular pad set. Can upgrade pads later. Bought the bolts and hoses. Took it all home and the next weekend, warm and sunny, put the front of the car up on blocks and disassembled the passenger’s side brake system. Started by putting plastic wrap over the top of the brake-clutch reservoir and screwing the top back on to minimize fluid loss. Broke the brake line at the chassis, pulled the caliper bolts and lock washers, and removed the caliper. Took the brake line off the caliper, removed pads, and put pad retention hardware back on the caliper (my core). Removed the nut and lock washer holding the dust shield to the support. Cleaned up all the parts removed. Everything was SAE 7/16 – 24. Recut the threads on the shield nut, as they were rusted.

Took a minute and went to Sears and bought new split ring lock washers (Grade 8) for all bolts. The brake lines at the chassis had anti-shake lock washers. Found them at Lowe’s, not Grade 8, but Grade 5.

Okay, Let’s Start!

Back home, got out rotary tool (Sears, but Dremel would also do) and put a radiac wheel on it. Pulled the dust shield to a comfortable position, slid a piece of corrugated cardboard in between the shield and the brake disc, and carefully removed 3/10 of an inch of material from both sides of the shield that are closest to the caliper to make room for the new caliper. The three-tenth measurement was in a circumferential direction and from the middle of the current shield edge, and the cut line was radial, inner to outer. Both cuts took me about ten minutes each. The cardboard held the shield away from the disc surface and gave indication when the radiac wheel penetrated the inner surface of the shield.

I removed the radiac wheel and put in a metal cutting burr. Again with care, I used the burr to open up the holes in the shield that the caliper bolts had to go through to clamp the shield and the caliper to the support arm. Those holes are 7/16ths (0.4375 in.) and have to be opened to 12 mm (0.4716 in.), a matter of about 0.0341 inches on the diameter. Takes about 2 minutes a hole.

Took a couple of files (flat and rat tail) and filed all the cut edges smooth, getting rid of any lingering flash. Now ready to assemble things.

The Toyota caliper drops straight in. The bolts with lock washers reposition the dust shield, and the caliper support plate has threads recessed about a tenth of an inch, so the bolts self-center and getting the thread engaged was easy. Wound the bolts down snug and then put the washer and nut back on the shield support. Tightened those three items. There is no torque called out for the caliper bolts, so I leaned on them with a long-handled ratchet.

Attaching the hose to the caliper: a caution here. The caliper is all aluminum. The hose fittings are steel. The thread is UNF. DO NOT OVER TIGHTEN the hose fitting. If you strip these threads, it will cost you! I lubricated (brake fluid) and installed the metric adapter into the caliper and tightened. Then lubricated and screwed the SAE right-angle fitting into the adapter. Got it snug but not tight. Then I screwed the other end of the hose into the chassis hard line, again lubricating the threads. That line I tightened. I then had a neighbor turn the steering wheel so I could check clearance relative to the car body work and the hose in the caliper. There was some touching at full lock. I adjusted the hose at the caliper until I had sufficient clearance and then tightened that line into the adapter, holding the adapter with a wrench while I tightened the fitting.

Installed the brake pads and was done with the mechanics of the job. Doing the first side took about an hour and a half because I worked slowly. I did the other side in about forty minutes.

Bled the brake system and was done except for testing. Took the car out for a spin around the neighborhood. Brakes worked fine. Now for five hundred miles of pad break-in.

I did measure the brake pad area. The Girling pads have five square inches of area, and the Toyota pads have just over six and four-tenths square inches, a net increase of 26%.

So, what did it cost?

The calipers (O’Reilly part No. 19-820 and 19-821) were $42.99 each plus core charge ($25.00). Total cost - $85.98 plus state tax.

• The pad set (very standard), part No. D137 was $13.99.

• The Caliper Bolts from The Roadster Factory, Part No. 158668, were $9.91 each, four required. Total cost was $39.64.

• The Hoses were $37.56 each, and the adapters were $4.30 each. Total cost was $83.72, but if I had stuck with the normal TR-3 hoses and just changed the one end, then the total cost would have been about $72.00.

• Miscellaneous hardware (new washers, etc.) and grease for pads, total cost - $7.68.

All up cost was $231.01. Installed and ready to stop!

**Postlude**

I pretty much broke the pads in during the Fall Leaf Tour, and this past weekend the club did the Guy Fawkes Tour for another 200 odd miles. On the return home (32 miles) on a cold and starry night, and beating down Rte 42 from Lebanon to Hopkinsville, I had occasion to do four hard stops from 60 – 70 MPH to stopped at some traffic lights (8 total, hit yellow to red on four, one simply for a car that was making a left turn across our lane) and the car came down quickly and in a very short distance (and I might add the tires, Vredestein Sprint Classics, are new this year). So these new calipers are a lot better than the Girling’s which were removed. This is a relatively inexpensive, and quick conversion that will really enhance a TR-3, -4, or -6 stopping performance. I’d bet it would work equally well on a Morgan.