TR2/3/3A Toyota calipers on a TR3

[tdskip]

Pat - think you had some fit issues, yes? Anyone else go there recently? Tips to pass along?

 

[martx-5]

The big fit issue is that the mounting brackets for the TR3 won't work. You need a set from a TR6, as they move the mounting holes further out.

Here are the two brackets...TR6 on the left, TR3 on the right.
You'll also need the late TR6 caliper mounting screws that have the wider shoulder.

Edit: Here's a couple of pics of the brake line bracket I fabricated.

 

[tdskip]

Ah - got it. Thanks Art!

 

[PatGalvin]

Hi Tom
My install was similar to Art's. A few tips or observations.
1) I think there are at least two different Toyota calipers out there that could be used for this mod. The caliper I selected did ride exactly centered in my rotor. So, I took it to the machine shop and had 40 thousands shaved off the caliper bracket (yes, TR6 caliper bracket) and voila, rotor is smack dab in center. Then I learn that there may be another caliper that works better for this application. Oh well, another $20 and half day of nonsense...
2) I had TSI custom fab up braided stainless brake lines. I made brackets and brake line pigtails (like Art) and had a bulkhead fitting on each end of the brake line. Looks great and I hope it works great too. Brake lines don't foul the wheel or frame so that's good. Pigtails were easy to make - I purchased short brake lines with 10 MM nuts at FLAPS and then reused the old brake line nuts on other end of pigtail.
3) I had to do quite a bit of trimming off the brake dust shield. There was a template on VTR that I used but that was totally insufficient for my car and I had to trim a lot more to get the dust shield to fit around bracket.

 

[DNK]

I'm a big fan of banjo nuts on my brakes and clutch pieces.
A small braided with a banjo would work for this too.

 

[Bremer]

To those who have done this mod: What are the differences in braking before/after? Is it worth doing?

 

[TR3driver]

Is it worth doing?

Kinda depends on what is wrong with your original brakes. They actually work quite well IMO unless there is a problem; easily modulated and well balanced front/rear (considering that there is no active balancing mechanism). You should have no trouble locking all 4 wheels when you want to. And there is no way that more braking will help, once the brakes are stronger than the tire's grip on the road.

But I noticed a lot of folks at the TRfest autocross who were experiencing significant front wheel lockup. IMO they need to 'improve' their rear brakes first!

Of course, this only applies to the larger brakes found on the (lighter) TR3. The heavier TR6 with it's smaller brakes may not do as well.

Not trying to pick a fight with those that want to drive Toyota/Triumph hybrids; just stating the facts as I see them.

 

[Marvin Gruber]

Just did some horsetrading and got a set of Toyota brakes, planned to put them on the 76 TR6 but after seeing the mod for the TR3, think I will save them for the TR3b. Thanks guys,.

Marv

 

[vivdownunder]

I'm also a vote for the original disc brakes. When kept in proper working condition they are just fine. I've had cars with power boosters which lighten pedal pressure, but still prefer the standard pedal weighting.

I've driven a TR3A with Toyota Hilux van 4 pot front calipers, and you have to be very careful on wet roads if still on skinny 165 x 15 tyres. Old hard rubber such as the common Michelin XZX's will easily lock up. It's a good conversion for competition work, but wider rims and tyres should be considered as part of the package for a road car.

Viv.

 

[tdskip]

Good info, guys. Thanks.

 

[martx-5]

Here's the VTR article on the Toyota calipers. They have some comparison info at the end of the article.

 

[TR3driver]

The problem with that comparison is that it is essentially impossible. One of the authors requested his name be removed after I pointed out the problem:

To achieve maximum braking with given tires, etc. you must have the brakes balanced such that all four wheels reach the point where the tires slip just a little bit without locking up. Once you've reached that point, any increase in braking effort will actually increase stopping distance, because a sliding tire will not grip the road nearly as well as a rolling one. This means that if one end locks up first, there is no way to improve stopping distance by improving the brakes at that end.

So, improving only the front brakes can only reduce stopping distances if the rear brakes locked up first with the stock brakes. But they don't.

Furthermore, increasing pad area does not increase braking force. Unlike tires on pavement, the brakes obey the 'classic' friction law quite well, which states that friction is proportional only to applied force and the coefficient of friction, NOT the frictional area. My high school physics teacher gave a convincing demonstration of this, with a simple block of 2x4 and a tilted table. The block slid at exactly the same speed, whether it was resting on the 2" side or the 4" side, even though the friction area was doubled.

BTW, Viv, I have wider (5.5") wheels and 205/55 tires in a fairly sticky compound. They are still street tires, but grip significantly better than the stock ones.