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Discussion Starter · #1 ·
I am looking at new calipers for the front of the Model T. Already has brackets for the GM metric floater calipers. The D154 fits this bracket and has 1 piston or 2 piston models. What would be the advantage of either one?. They are comparably priced. The 1 piston model has a 2.5" piston. The 2 piston model has 1.12" pistons. The rears are the GM metric calipers (1 piston) with built in emergency brake. I will leave those in place. Which one would you suggest, 1 or 2 piston?
 

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I'd go for the single piston. I changed my Wilwood 2 piston calipers for the Metric units as I was unhappy with the braking power of the two piston. The single piston unit actually has more piston surface area than the two piston.
 

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i agree with bill3337 over 2.5X the surface area in the single piston caliper
the single 2.5" piston has 4.9 in², while each 1.12" piston is .99 in² for a total of 1.98 in² in the dual piston
with a 100 psi in the lines the single piston will have 490 lbs of stopping force vs 198 lbs of stopping force
this is assuming the same sized pad in in²
 

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Discussion Starter · #5 ·
The wilwood 2 Piston is 1.62 bore= 2 .06 sqin per Piston or 4 .12 sqin per caliper. Still less than the single 2.5 piston
Yeah I did some more research. The 1.12" 2 piston is apparently for the rear. As you said there is also a 1.62" 2 piston caliper for the front and yes it does not have as much piston surface area as the 2.5" single.
The Wilwoods are in the $200 each area. I guess the next question is, does the Wilwood provide enough performance improvement over the 2.5" single piston GM metric caliper to justify the considerable extra cost of the Wilwoods? Seems to me that the GM caliper with the same size piston should have just as much clamping power as the Wilwood.
If that is the case I think I will just stick with the GM metric calipers. I did find some metric calipers that have a 2.75" bore. That might be something for me to look into.
 

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A stock GM caliper is probably stiffer than an aluminum body caliper. Racers that have to run a stock stock type caliper would note the pedal getting a little spongy under really hard braking, but probably not noticeable otherwise. Coleman also makes parts to reduce the size of the Pistons for brake balancing using the metric caliper.
 

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Race it, Don't rice it!
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The GM cast iron are stiffer but.....the performance advantage of the weight savings far outweighs the rigidity concern which is very easily fixed with pad compounds. This also depends on street, track and what kind of track.
Your indirect answer it depends......What are you looking for and under what condition?
 

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I guess the next question is, does the Wilwood provide enough performance improvement over the 2.5" single piston GM metric caliper to justify the considerable extra cost of the Wilwoods?
IMO fancy calipers are for bragging rights as to how much you spent upgrading your new mustang 🍆
2.5" piston is a 2.5" piston is a 2.5" piston, plus you can get gm calipers anywhere
 

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Discussion Starter · #9 ·
OK. Let me start at the beginning. I started this quest to improve the barely adequate braking system in my '26 T coupe. It has the GM metric calipers in front with the rear calipers having the built in e brake.
I have never been happy with the brake performance. I spent a good part of the day yesterday researching. I had never heard of low drag calipers and that is what my front calipers are, low drag, unbeknownst to me. Apparently these calipers have a seal that causes the piston to retract away from the pad, and they require a step bore MC, also known as a quick take up MC. I have been running a standard Corvette MC. This is apparently the cause of the longer than normal stroke of the pedal and reduced braking power. So it looks like I can solve my problem with a MC change. I have ordered a step bore MC for a 1985 S-10. It uses these low drag calipers, so it should work with mine. I was figuring to spend $6-700 for new calipers and MC to fix the problem. That S-10 MC cost me $63. Pretty cheap fix, if it works. I'll let you know.
Thank you guys for the help.
 

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OK. Let me start at the beginning. I started this quest to improve the barely adequate braking system in my '26 T coupe. It has the GM metric calipers in front with the rear calipers having the built in e brake.
I have never been happy with the brake performance. I spent a good part of the day yesterday researching. I had never heard of low drag calipers and that is what my front calipers are, low drag, unbeknownst to me. Apparently these calipers have a seal that causes the piston to retract away from the pad, and they require a step bore MC, also known as a quick take up MC. I have been running a standard Corvette MC. This is apparently the cause of the longer than normal stroke of the pedal and reduced braking power. So it looks like I can solve my problem with a MC change. I have ordered a step bore MC for a 1985 S-10. It uses these low drag calipers, so it should work with mine. I was figuring to spend $6-700 for new calipers and MC to fix the problem. That S-10 MC cost me $63. Pretty cheap fix, if it works. I'll let you know.
Thank you guys for the help.
You're likely on the right track. The GM metric caliper braking system was designed for 4000# vehicles and should have no problem stopping a 2000# bucket T even in stock form.

Russ
 
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Discussion Starter · #12 ·
Racing brake pads will provide much more braking effect than any parts store pads.
I would think you would want a MC for a 4 wheel disc system like a later model S10 or Blazer, Bravada,etc.
I have never used racing pads on anything but my circle track cars. I was under the impression that they were only better when they are hot. I didn't think that they would get hot enough driving on the street to be of any benefit. I know they are definitely more aggressive on the rotors. Is there a pad you would recommend?
As far as an MC for 4 wheel disc, just what is the difference in the MC for a disc system and the MC for a drum system. I'm not sure but I believe the only difference is the volume of the reservoir. I have had MC hooked up with disc/drum system with the Corvette MC with the port nearest the flange hooked to the front discs. and the rear to the other port. Then, just to see, I changed it around so the front discs were hooked up to the port farthest from the flange. I could tell absolutely no change in brake performance. As far as I can tell there is no difference in a disc or drum MC. I could be completely wrong, but that is what my experience is telling me.
Anyway that MC should be here in a couple of days, and I'll know for sure. If it doesn't work, I've made a lot worse than $63 mistakes. I'll let you know.
In my research, the 80's S-10 MC was recommended several times. They were disc/drum systems though. I'm gambling a little bit here.
 

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The Hawk Black pads will stop better than any conventional pad.
Some MC use a step bore to provide more fluid to the calipers than the wheel cylinders. MC with a varying diameter in the casting for the Piston is the indicator. Calipers have different volume requirements than wheel cylinders. The bigger bore does reduce the outlet pressure.
 

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DTC and HP blacks….the shower of sparks wards off tail gators as well. I’ve mentioned pads that work great that are more rotor friendly and still work well cold without and less performance loss at temp.
 

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Discussion Starter · #15 ·
Boy! This hotrodding thing is never easy, is it? I got the new S-10 MC. Got it bled and bolted in. Guess what? The outlets are way bigger than the 3/8"-24 for 3/16" tubing, they are 1/2"-20 IFF. Of course that was never mentioned in the specs. Never noticed it till it was in there. That's what I get for assuming. So, now I need adapters, 1/2-20 IFM to 3/8-24 IFF. I thought I had everything I needed to get the job done in a few hours. Now I have to wait with the car down a couple of days for adapters to show up . Why did those S-10's have such a big fitting there?
 

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Boy! This hotrodding thing is never easy, is it? I got the new S-10 MC. Got it bled and bolted in. Guess what? The outlets are way bigger than the 3/8"-24 for 3/16" tubing, they are 1/2"-20 IFF. Of course that was never mentioned in the specs. Never noticed it till it was in there. That's what I get for assuming. So, now I need adapters, 1/2-20 IFM to 3/8-24 IFF. I thought I had everything I needed to get the job done in a few hours. Now I have to wait with the car down a couple of days for adapters to show up . Why did those S-10's have such a big fitting there?
That's what the fun is about Hot rodding. experimenting and learning. If you just bought bits and bolted them on where would racing be ? Innovation comes from trying something and making it better . ;)
 

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You don't have to have a "step bore" MC for low drag calipers. ALL GM calipers since 1983 or so are "low drag". That really just means the caliper floats better and the pads pull away from the rotor easier. The seal is just a square o-ring type. The square o-ring "tilts" a bit when pressure is put on the piston (then the piston slides in the ring if it has to go very far) and goes back in place when pressure is off - pulling the piston slightly back. The caliper rides on sort of loose pins -- as compared to the old Bendix brakes that slide on rails with a "leaf spring" tensioner (older Ford style brakes).

What BORE is your master cylinder? It sounds like you don't have enough pressure. You shouldn't have anything more than a 1" bore MC. Many Corvetee MCs are 1-1/8" and 1-1/4". Four wheel disc Corvette MCs may be as little as 7/8". The smaller the bore the more pressure, but less volume. So if you decrease the bore there will be a little more pedal travel to move the same volume. You can change as much as 1/8" in bore and hardly be able to tell the difference in pedal travel, but will in pressure. It's hydraulics 101, nothing special.

MP Brakes (www.mpbrakes.com) has some good tech papers on their site with all the math and info you could want. Something is off in your set-up -- a T bucket is a light car, almost any hydraulic brakes should perform well.
 

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Discussion Starter · #20 ·
Coleman also makes parts to reduce the size of the pistons for brake balancing using the metric caliper.
Whoa! I have been doing business with Coleman since about 1986. Great company. I never saw those piston reducers for the 2.5" GM metric calipers. I looked them up. That reducer is very interesting.
I called Wilwood yesterday. Spent about 45 minutes on the phone with one of their techs. He had no clue about "low drag" brakes. Couldn't tell me if his calipers were low drag or not. I asked him to recommend a bore size for his MC. He didn't know anything about my rear calipers w/ ebrake from a 1982 Cadillac Seville. I didn't know the piston size in it either. So he couldn't give me a recommendation on bore size. I have since measured it. It is a 2" piston, so GM made some attempt at balancing the front and rear brakes by reducing rear caliper piston size on cars equipped with the hydraulic/mechanical e-brake, and the Coleman reducers won't work with 2" piston calipers. Dang it! So I will have to rely on the proportioning valve to get my balance right. With this new information I will call Wilwood back and ask again for a bore size recommendation.
Thanks, Imsport!
I just got off the phone with Wilwood tech. He recommended a 7/8" cylinder for good brake modulation, or a 15/16" for a higher harder pedal, depending on personal preference.
I did some math: Wilwood 1.12 dual piston caliper for the rear has 1.98 sq. in. area.
The 2" GM caliper has 3.14 sq. in. area. So I expect that i will have to dial back the rears some.


That's what the fun is about Hot rodding. experimenting and learning. If you just bought bits and bolted them on where would racing be ? Innovation comes from trying something and making it better . ;)
That's exactly why I have been building hot rods and race cars for more than 50 years now! But sometimes it feels like you are beating your head against a brick wall.
 
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