Who has Power Stop Brakes? Thoughts on which ones to get with larger tires

[J_C]

Larger tires are not much of a factor for brake pad selection. They are swamped by vehicle weight which does not change much as a % from a few dozen lbs of tires. Rotational weight is an acceleration issue far more than deceleration.

Don't get "sport" pads if you want best cold performance, nor ceramic pads. I am curious why you are sure that stock pads aren't enough?

Get standard semi-metallic pads. Severe duty are also formulated for heat, opposite of your need.

If you are still lacking brake friction it's more likely you need a brake fluid flush (bleed) or new master cylinder.

Larger rotors can help a little but it seems like the issue you're describing is more than just a little off. Any 30 year or younger vehicle, with the system working like new, especially with oversized tires that have terrain optimized tread at the expense of pavement traction, has more than enough braking power to lock the wheels up with standard factory pads.

Granted, the pads you have might have not broken in well or the rotors could be glazed. I'm just stating that if you were to start from scratch from all good parts, the factory parts in new/good condition should stop fine with larger tires.

"Performance" parts don't offer better stopping in your described driving. Instead they try to keep stopping good at high heat levels, often at the expense of stopping at low heat levels.

 

[1997XLTRollover]

Larger tires are not much of a factor for brake pad selection. They are swamped by vehicle weight which does not change much as a % from a few dozen lbs of tires. Rotational weight is an acceleration issue far more than deceleration.

Don't get "sport" pads if you want best cold performance, nor ceramic pads. I am curious why you are sure that stock pads aren't enough?

Get standard semi-metallic pads. Severe duty are also formulated for heat, opposite of your need.

If you are still lacking brake friction it's more likely you need a brake fluid flush (bleed) or new master cylinder.

Larger rotors can help a little but it seems like the issue you're describing is more than just a little off. Any 30 year or younger vehicle, with the system working like new, especially with oversized tires that have terrain optimized tread at the expense of pavement traction, has more than enough braking power to lock the wheels up with standard factory pads.

Granted, the pads you have might have not broken in well or the rotors could be glazed. I'm just stating that if you were to start from scratch from all good parts, the factory parts in new/good condition should stop fine with larger tires.

"Performance" parts don't offer better stopping in your described driving. Instead they try to keep stopping good at high heat levels, often at the expense of stopping at low heat levels.

I have to disagree with the stopping larger tires not being a problem. It certainly takes more brake to stop an 80 lb 32" tire than a 29" 55 lb tire. My rotors could be glazed because I know these brakes have been taking a beating. How can I tell if they are?

Fluid is pretty fresh. 10k miles and maybe 2 years and it doesn't feel like there is air in the system, but either way ill be doing fresh dot 4 shortly along with new pads. Maybe rotors too.

All rubber lines are also only a couple years old. What gets me is they work well hot. So I'm thinking rotors are ok and so is the rest of the system, just wrong pad selection. But I could be wrong.

 

[J_C]

If you were talking about a tire free spinning in air, sure the heavier tire would need more brake friction but that is a small amount of kinetic energy compared to the vehicle at speed, far below what the brakes are designed to stop.

Instead the relevant weight is that of the moving vehicle, which increases very little from the tire change, and going further, the factory brakes are designed and tested to also stop the vehicle safely with some tow weight added, since up to (3000lbs?) doesn't require trailer brakes. Then again that weight # may vary by state but still...

 

[1997XLTRollover]

If you were talking about a tire free spinning in air, sure the heavier tire would need more brake friction but that is a small amount of kinetic energy compared to the the vehicle speed, far below what the brakes are designed to stop.

Instead the relevant weight is that of the moving vehicle, which increases very little from the tire change, and going further, the factory brakes are designed and tested to also stop the vehicle safely with some tow weight added, since up to (3000lbs?) doesn't require trailer brakes. Then again that weight # may vary by state but still...

Fair enough makes sense. It will still increase stopping distance but true maybe not as bad as I think it will. I have to have something screwy with these brakes. They just feel like they don't bite.

 

[CDW6212R]

You're right that something is amiss with those brakes, but the tires have some effect too, a noticeable effect. I immediately noticed poorer braking with my 72.5lbs wheels/tires.

I have a G-force testing device, which can measure 1/4 miles stats, and braking distances from 60mph. I tested my Mercury after the heavy 18's, and then swapped the prior 58lbs Cobra wheels back on. The distance went down a lot with the lighter 58lbs wheels/tires. I don't recall the figure, but say about 15 feet. That was before I put together the custom brakes. I only tested the truck once more, just after the better brakes. It was much better then with the 18's, and a little better than with the 58lbs wheels/tires. That test device isn't designed for doing brake testing, it simply has an algorithm in it to begin recording distance once 60mph is reached. So the accuracy is dependent on how long it takes the driver to see 60mph and then hit the brakes. That's why I didn't do it more often, or post much about it. That device does well to see big enough changes to conclude a change was positive, or negative, but not helpful to know how much really.

 

[J_C]

^ But is that conclusive? In this topic we're already encountering another variable of temperature. If ABS comes into play, or any degree of traction loss then there's also differences in tire traction. There are a lot of Jeep guys who run larger, heavier tires with stock brakes and don't notice much difference.

 

[1997XLTRollover]

My ABS NEVER kicks in on dry road. Even all the way to a stop. I never lock a tire or even hear squealing like it's coming close to locking up. I wish I could find the axles I need fast because I would just do the 12" upgrade and put new pads on those rotors, but I don't want to take this all apart twice especially if the stock brakes should be working better than this.

You know... now that I think about it, something felt off about these brakes since the day I put them on. The first time I hit the brakes I thought the truck wasn't going to stop. They got better once they broke in after a day or so of driving, but they always had something wrong with them. I'm still waiting to hear back from Summit Racing to see if they can warranty them for me, but I've had them 10-15k miles and about 2.5 years so who knows.

Oh and I spoke with Power Stop. They said something is wrong (maybe glazed pads), that these are great street pads and the "towing" pad is the same compound but has a stainless steel backing plate to absorb more heat than the rubber one on my pads. So since I don't have a brake fade issue there is no reason to "upgrade".

 

[J_C]

I'd consider trying semi-metallic pads from autozone. Right now they have some with a lifetime warranty for $23 before a $10 Gift Card rebate, or rebates on higher line pads too. Worst comes to worst and they don't work any better, you're only out $13 bucks. Then again if they don't work any worse and something else is still the problem, you have replacement front pads forever for $13.

https://www.autozone.com/brakes-and.../duralast-brake-pads/94210_420698_1610_216815

However I don't have those, last set I put on (IIRC) were Autozone DG652, currently $41 before a $20 Gift Card rebate.
https://www.autozone.com/brakes-and...ast-gold-brake-pads/529520_855550_1610_216815

 

[CDW6212R]

My ABS NEVER kicks in on dry road. Even all the way to a stop. I never lock a tire or even hear squealing like it's coming close to locking up. ...
.

That's a tell tale sign, the ABS should be almost easy to engage. Mine wouldn't with the bigger 18's either. But with my custom brakes, the ABS would work hard at 80mph. The calipers I chose were a good bit larger in piston area than the stock ones.

Now with a replacement from SSBC that is closer to stock size(piston area), it functions close to stock, still better but a better balance in size. I'm putting those on my 99 mail truck, and then working on a different caliper for my Black Coal Limited. Assuming that works well, I'll duplicate them onto my 99, because they have huge pads. I know this doesn't help anyone else, I wish it didn't cost so much for special rotors, and the calipers. It'll be in the $1500+ range I'm sure.

For your, get new fluid in it, check the rotor surfaces well, and get new pads again. The current rotors should be fine, if they actually are glazed a bit, have them turned(only by a shop you trust to not cut off too much(parts stores will cut them deep(to make you buy rotors the next time))). Regards,

 

[Centaurus5.0]

Here's .02

https://www.aamva.org/uploadedFiles...izedTiresOnAlteredHeightVehicles_Findings.pdf

Quote:
"The oversize tires had a significant impact on maximum deceleration at various levels of applied pedal force."

"Braking performance reduced 20 to 25 percent by tire/suspension configuration regardless of the amount of applied pedal force (seeTable4). It is immediately evident that the ability to stop a vehicle with oversize tires depends on the amount of pedal force that can be applied."

"The installation of oversize tires had the most profound effect on changes to rollover propensity and increased pedal forces for achieving equivalent levels of deceleration with oversize tires. Similar results were found when a series of straight-line braking tests sponsored by NHTSA were conducted to study the dynamic response properties of a modified light-duty truck, heavy-duty truck and sport-utility vehicle equipped with body/suspension lift kits and oversize tires.13 The reduction in braking performance of the test vehicle was primarily due to the installation of oversize tires and not the body and suspension lift kits"


Like was mentioned, no disc/pad combo is going to make up for the loss in mechanical leverage and added weight.

After having EBC rotors on my rig for 1.5 years now, I can say I'll never buy a pair of slotted rotors again. Too much noise and traps dirt in the slots and pads. Old school NOS Motorcraft Made in USA rotors off ebay for me here on out.

 

[1997XLTRollover]

Yeah I'm fairly certain this is a large tire issue. I just wouldn't expect the brakes to bite that much better when hot. But in all fairness I never tested this with factory tires. After reading that article I do really want to do the 12" upgrade asap.

 

[J_C]

^ The article is suggesting a mere 1.5% difference. Follow the math below and look at the article on page 8.

While I feel there are several variables the linked test does not take into account, ultimately what they found was that at the max pedal force tested (150lbs), at the same 4" lift height, brake force decreased from 0.70g to 0.68g with a 4" tire diameter increase from 28" to 32" (bottom of page 8).

Stock tire height with a 5.0L and 16" wheels (P255/70/16) is about 30" and the move was to 32" tires, a 2" difference, half the 4" difference tested (28" vs 32" with the same 4" lift). It could then be extrapolated that if brake force decreases with tire diameter (and weight) increase then with half the tire diameter increase, the brake force difference would change by half too from 0.70g to 0.69g, half as much instead of 0.70g to 0.68g.

0.69g/0.70g * 100 = 98.5% of the braking performance with the 2" larger tires. Their statement of 20-25% decrease was only the most extreme test cases, cases where variables start to make a lot more difference like the tread pattern of huge tires, the contact patch if inflation pressure is not adjusted to vehicle weight (goes down as tire size goes up).

While they do not list the weights of their tested tires, it seems reasonable to assume that they tried to pick a 32" with a weight representative of the market unless stated otherwise.

Everything else swamps your 2" larger tires, but particularly it looks like your brake pad formulation is no good until it heats up. Switch to pads not designed to trade cold performance for hot endurance.

 

[J_C]

Oh, one more thing about the linked article. It is flawed and cannot support what they're stating. They used a brake tester that leaves the vehicle stationary and is only meant to test Brake Balance from rotational torque, not vehicle kinetic energy. For the results to have real world application to support their conclusions, the vehicle would have to have zero weight besides the wheels so it had no kinetic energy besides that from the ~400lbs of the wheels.

 

[Centaurus5.0]

There is the static weight of the tire. Then there is the diameter of the tire. Then there is a multiplication of force as the speed of the tire increases. Not a linear 1-2% increase of force at all speeds I wouldn't think.

How do you calculate centrifugal forces? I got a D+ in math.

 

[CDW6212R]

Centrifugal forces increase dramatically as weights and diameters become larger. I'm sorry but I didn't read the article. I appreciate good math, but I'm confident that common weight changes of wheel/tire weights has a noticeable affect on braking performance.

I've only tested the concept with one of my own vehicles, and I didn't like the poor braking I had with my first heavy 18" wheels/tires. They were 72.5 pounds each, and I replaced the tires twice as I wore out the old ones, and ended with weights around 64lbs with smaller sizes(265/60/18's versus now 255/55/18's). My brakes are big enough now to handle bigger wheels or tires, but the weight also slowed acceleration noticeably too. I wanted to improve what ever I could.

 

[Centaurus5.0]

Personal style aside, I think a 2011 Ranger 15" wheel that fits over the Sport/Trac 12" discs with whatever tire you need using non-slotted/drilled brakes is optimal for performance for a 2nd Gen.

With the loss in mass that comes with slotted/drilled rotors come a loss in pad-to-disc surface area and less available mass to absorb heat.

 

[1997XLTRollover]

Personal style aside, I think a Ranger 15" wheel that fits over the Ranger 12" discs with whatever tire you need using OEM non-lotted/drilled brakes is optimal for performance for a 2nd Gen'er.

With the loss in mass that comes with slotted/drilled rotors come a loss in pad-to-disc surface area and less available mass to absorb heat.

I've never had a heat issue. In fact I wish my brakes would stay warm. Then I wouldn't have this issue. Not once have I had brake fade.

 

[Centaurus5.0]

More mass means the disc would hold heat longer, once it was warmed up. Slotted/drilled discs heat up quicker but also cool off faster. Just like the engine and transmission, brakes have a temp range for optimal performance and life, and that depends on materials, design and application.