TR6 Toyota Truck calipers on a TR6 WOW

[Hillbilly]

I just did this conversion and what a difference!
I used 1979-1984 Toyota 4x4 front brake calipers on my 1973 TR6.
I had to fab up some brake lines, but That in itself was easy too. a little trimming on the dust shield, and even used the stock OEM caliper mounting bolts. a simple straight swap.
OEM calipers for the triump were about $129.00 each, I picked up the toyota calipers for $38.00 each! twice the stopping power and saved $182.00 !!!
I saved a bunch of money and my braking is MUCH BETTER!
I also found out that I can actually use the very same calipers on my Datsun 240Z as well!
here is a link to the swap....
https://www.vtr.org/maintain/brake-conversion.shtml

 

[Starbuck]

Impressive.
And more than a "statistically significant" gain in stopping power.

I wonder if any such upgrade is available for Spitfires?

Or MGB's

 

[TR3driver]

You do realize that is impossible, right? Front/rear balance is important for maximum stopping power; you have to get both ends working as hard as they can to stop the car. The stock brakes (in good condition) come pretty close. If you did bolt on a big upgrade in the front, the front wheels would lock early and be sliding (meaning they have lost grip) before the rear wheels reach maximum braking.

 

[martx-5]

I have a set of the Toyota calipers on my TR3 only because I work for a rebuilder, and the price was right. I haven't noticed much of a difference in braking. I don't remember the what the four piston diameters are on the Toyota caliper, but the total area of the pistons is almost identical to the piston area of the two pistons in the Triumph caliper. This means that the hydraulic forces of the two calipers will be the same. The size of the pads of the Toyota caliper is larger, but what effect that has on the braking, I don't know. Perhaps heat dissipation is improved.

 

[Monkeywrench]

You do realize that is impossible, right? Front/rear balance is important for maximum stopping power; you have to get both ends working as hard as they can to stop the car. The stock brakes (in good condition) come pretty close. If you did bolt on a big upgrade in the front, the front wheels would lock early and be sliding (meaning they have lost grip) before the rear wheels reach maximum braking.

It's not impossible.

The biggest factor in braking performance are tires.

Everyone knows the the front brakes do 70%-80% of all the work. I don't know what the o.p. has done to his car, but if he has put stickier than stock tires and the suspension is relatively stock, he would have increased weight transfer to the front under braking which would reduce the amount of braking the rear can do and subsequently increase how much the front can. Also, depending on how "grabby" the o.p.'s new pads are, it can totally change the sensation of the braking system.

He also gained the extra heat capacity helping stop the car from high speeds or repeatedly. Looking at the size of a stock Girling caliper, I would imagine they would start to fade even during a single panic stop from 65mph or so.

 

[TR3driver]

The size of the pads of the Toyota caliper is larger, but what effect that has on the braking, I don't know.

Look up Amonton's second law.

 

[Monkeywrench]

The size of the pads of the Toyota caliper is larger, but what effect that has on the braking, I don't know.

Look up Amonton's second law.

Just did. I edited my post while you were making yours.

 

[Andrew Mace]

I wonder if any such upgrade is available for Spitfires?

Not exactly. However, the GT6 used the same Type 16 Girling calipers as did the later big TRs. Therefore, one could swap in the front vertical links and all associated brake bits (discs are larger as well on a GT6 than those of the Spitfire), and then do the conversion. I think I'd want to add the bigger 8" rear brakes from a GT6 to that same Spitfire if I were to do this.

OTOH, I don't know that the <span style="font-style: italic">average</span> Spitfire needs much more braking than the stock system -- perhaps with upgraded pads and/or shoes -- can provide, so.... :wink:

 

[TR3driver]

he would have increased weight transfer to the front under braking which would reduce the amount of braking the rear can do and subsequently increase how much the front can.

Meaning he would have premature rear lockup before the conversion. Have you ever seen a TR6 that locks the rear wheels first? (without having something wrong with the front brakes)

I agree, the brakes, suspension, tires, etc. work as a system. If you have changed one part of the system, then changing another part to match will improve things. But that's not what he said.

And besides, as Art pointed out, the Toy calipers have almost exactly the same piston area as the original TR6; meaning the same normal force is applied to the pads. Any changes in braking have to come from changes in pad material (coefficient of friction). There are high CoF pads available, and maybe there are more choices for the Toy pads (although most of the common compounds are also available for TR6 pads). But again, that's not what he said.

 

[swift6]

The pad size on the Toyota calipers are larger, the combined piston size in the Toyota calipers though are almost identical to the stock Girling pistons. There are twice as many pistons so they are spreading almost the same force over a larger area. Lots of very detailed reports out there about the Toyota brake conversion. It is somewhat less expensive but not necessarily that much better and the Toyota calipers may even be a bit heavier. The most detailed report with identical testing pre & post conversion showed very little difference between proper working Girlings and the Toyota calipers. Increasing the efficiency of the rear brakes over stock showed the biggest reduction in braking distance.

Think about the tires that were in use when these cars were made though. The cheapest Costco tires are going to give better performance today then the Michelin X's did when new. Modern tires can probably handle more rear brake pressure than the original tires thus the difference.

If you get too much weight transfer to the front then your rears will lock up early and you'll lose control of the rear end, which is worse than locking the fronts and sliding.

Most likely a case of old and tired stock calipers with old glazed pads vs. brand new Toyota units and pads. Same as replacing worn out SUs/Zeniths with brand new downdraft webers and then declaring the difference clearly shows the SUs/Zeniths were junk from the get go when all they really needed was a proper rebuild or service.

 

[Monkeywrench]

he would have increased weight transfer to the front under braking which would reduce the amount of braking the rear can do and subsequently increase how much the front can.

Meaning he would have premature rear lockup before the conversion. Have you ever seen a TR6 that locks the rear wheels first? (without having something wrong with the front brakes)

He could have and I have (saw it an an autocross and have experience it first hand with changing to 140treadware tires on a Miata (which are notoriously front biased)). Stickier than OEM tires (ie, any modern radial), increases weight transfer. Increased weigh transfer = less loading on the rear tires which means less traction from them for braking. The fronts will have the ability to do more braking under these conditions.

I agree, the brakes, suspension, tires, etc. work as a system. If you have changed one part of the system, then changing another part to match will improve things. But that's not what he said.

If he changed tires, he took advantage of their new found grip.

And besides, as Art pointed out, the Toy calipers have almost exactly the same piston area as the original TR6; meaning the same normal force is applied to the pads.

I understand that. As I said before, I edited my post while you were making yours. I did only wake up about 10 minutes before I posted that...

BUT, Pad surface area increases. Same normal force applied over a great area.
https://www.vtr.org/maintain/brakes/brakes01.jpg scale it out and take the area of the two.

Any changes in braking have to come from changes in pad material (coefficient of friction). There are high CoF pads available, and maybe there are more choices for the Toy pads (although most of the common compounds are also available for TR6 pads). But again, that's not what he said.

See my first point.

Despite what he said or didn't say, you said it was impossible. I'm telling you why it's not.

 

[swift6]

BUT, Pad surface area increases. Same normal force applied over a great area.
https://www.vtr.org/maintain/brakes/brakes01.jpg scale it out and take the area of the two.

When this information was migrated from the original site with the original test information to the VTR site, the effectiveness of the Toyota calipers somehow increased from the original test data. Check out this site for the original information and even a warning that the information on the VTR is not accurate and all attempts to get them to change it have failed.

https://turbo-tr6.info/tr6_brake_install.htm

 

[Marvin Gruber]

Whew, you guys are making my head hurt!

Marv

 

[Monkeywrench]

BUT, Pad surface area increases. Same normal force applied over a great area.
https://www.vtr.org/maintain/brakes/brakes01.jpg scale it out and take the area of the two.

When this information was migrated from the original site with the original test information to the VTR site, the effectiveness of the Toyota calipers somehow increased from the original test data. Check out this site for the original information and even a warning that the information on the VTR is not accurate and all attempts to get them to change it have failed.

https://turbo-tr6.info/tr6_brake_install.htm

Though it's interesting information, it still doesn't give anyone real world performance figures (just that they are theoretically equal despite ignoring other significant factors). That article didn't account for caliper stiffness, the ability of the caliper to keep the pads' entire surface in contact with the rotor, and though it mentions heat absorption, that is a HUGE factor in braking performance that cannot be tossed aside like that. That's a good article for trying to figure out master cylinder sizes though.

So friction coefficients being equal, the greater pad surface area will run cooler at equal clamping force. That means less gassing of the pad (which will push it away from the rotor), and the most obvious one, it will take more to boil the fluid.

So yes, driving around town it won't make a difference, but make 3 consecutive stops from 55mph with the stock calipers and the Toyota calipers and get back to me. The original poster didn't say he did that, but he also didn't say he didn't do it. It depends on how you and where you drive. Were I'm from, we have some roads with 55mph speed limits and a lot of traffic lights.

I don't really care one way or the other, but it is NOT impossible.

 

[Hillbilly]

I did change the tires.
I have goodyear Eagle GT Performance Touring. They are a directional tread tire and are the widest I can fit on the rims.
VERY nice handling .
BTW, I tried to rebuild the original Girlings and was totally in a VERY VERY Bad mood after trying to install the rubber dust boots in the calipers. I spent an honest 2 hours trying to get ONE boot on, and after I got it on, it simply rolled off. I was nearly fit to be tied. I wish there was a pond next to the shop as I would have raised the level by two caliper's worth.
After the frustration and anger subsided, I went to the internet and searched for a good deal on calipers. It is then when I came across the brake upgrade article. The weight betwixt the two are negligible. The pad area is much larger with the Toyota calipers... I would say almost twice the size. I have not "Tested" the efficiency of the setup as I have only taken the car out once since it's 20 some year sleep and was more concerned with getting home than a brake-testing session. Time will tell as there are lots and lots of twisty curvy fun driving roads around here in Kentucky and I will be driving this car whenever conditions permit. I'll keep you posted.

 

[tdskip]

Keep it friendly guys....

 

[eschneider]

Hey kids - I think if the bore of the rear wheel cylinders ins increased, the balance argument is resolved?

I think these are pretty close:
https://www.bpnorthwest.com/.sc/ms/dd/ee/9813/Wheel Cylinder Rear 7^2F8 bore

 

[Mickey Richaud]

I like cheese!

 

[SkinnedKnuckles]

Most likely a case of old and tired stock calipers with old glazed pads vs. brand new Toyota units and pads. Same as replacing worn out SUs/Zeniths with brand new downdraft webers and then declaring the difference clearly shows the SUs/Zeniths were junk from the get go when all they really needed was a proper rebuild or service.

That's were I was going as well. Rebuilding my stock calipers made a big difference in braking - shortened stop distance & no pulling. Green pads helped even more.

 

[Geo Hahn]

...BTW, I tried to rebuild the original Girlings and was totally in a VERY VERY Bad mood after trying to install the rubber dust boots in the calipers. I spent an honest 2 hours trying to get ONE boot on, and after I got it on, it simply rolled off...

There is (like so many things) a trick to putting that boot on that gets the job done in under 10 seconds. Too late for your brakes but now that you've found this forum you'll find out about other tasks that may appear worse than they need to be.