When do larger tires require larger brakes ?

[Dewyaw]

Nothing to do with tire size. It's vehicle weight. MASS is what you are stopping, not tire size.

How can tire size have nothing to do with it?? Physics 101...larger rotating mass requires more friction to stop.

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[Renegade]

I'd argue against 'they are nothing great' - they are BETTER than my prior trucks had, better than any other Jeep we've ever owned. I thought I was going through the windshield first time I hit them even moderately hard.

I agree that they work well. Physics still wins. It ALWAYS wins.

 

[ShadowsPapa]

How can tire size have nothing to do with it?? Physics 101...larger rotating mass requires more friction to stop.

That's what I said later - if there's more MASS. Now not ALL larger tires mean more mass. Some folks have found some that weighed similar or the same as slightly smaller tires.
In fact some have put 35s on that didn't weigh more than the 33s I have.
So if it means more MASS, then that also factors in.
Check tire weights.

 

[ShadowsPapa]

 

[Mac]

That's what I said later - if there's more MASS. Now not ALL larger tires mean more mass. Some folks have found some that weighed similar or the same as slightly smaller tires.
In fact some have put 35s on that didn't weigh more than the 33s I have.
So if it means more MASS, then that also factors in.
Check tire weights.

It is leverage, think of it this way, if you have to break a lug nut free which is easier? A 12” ratchet or a 24” ratchet? That is the principle that tires apply to braking force. A once or two increase in tire size does not seem like like much but it has a significant affect, the weight of rotating mass also effects braking distance.

 

[Silvertruck]

All you guys are right with physics. But the JT stops well for size, vehicle mass and rotating mass even with 37s.

plus if i needed bigger brakes i’d have to get rid of my 17’s and jeeps need fat tires

 

[Renegade]

Powerstop makes a Performance brake kit. Their Z36 pads are also available separately. I haven’t tried them, but some JL owners report positive results.

 

[FLUndertaker]

I had 42” TSLs on my CJ with manual brakes. Tons with 4 wheel disks and large capacity corvette master cylinder with a tuned proportioning valve helped but still an emergency stop was a scary thing.

 

[Front Runner]

For stock JTs.... if you don’t believe the stopping distance increases when you add larger tires your kidding yourself.

Not what I said at all. I said plenty of stopping power. I had a much heavier JKU and 35’s. I upgraded it to the equivalent of what is on the JT and JL now. Plenty of stopping power but more weight and larger tires equals longer stopping distance but what is on here is more than adequate. As a driver you have to drive a modified vehicle differently Know it may weigh more. Nothing you can do about a situation out of your control...

 

[Higher_Ground]

This has been an interesting read, and a refresher since it's been 15 years since I had any classes on physics or dynamics. In other words, this may be totally wrong but it's my shot at understanding it.

I was under the impression that pretty much every vehicle will be able to produce enough braking power to lock a wheel, so the power isn't really the problem. The problem is how much friction force the tires will take before slipping, right? Stopping the wheel doesn't stop the vehicle.

That doesn't seem to be dependent on radius. All other tire variables held constant, it seems more dependent on the surface area, which in turn would depend on the weight of the vehicle and air pressure in the tires.

So while it would seem that larger wheels/tires would require a greater braking force, the stopping distance traveled doesn't seem to be any different assuming the tires have the same coefficient of friction and surface area.

So does it affect the brakes? Yes, and I assume the effect is greater wear. Does it effect the distance you come to a stop? Probably not, as that is a factor of the rubber on the tires and not the brake pads themselves.

 

[Renegade]

This has been an interesting read, and a refresher since it's been 15 years since I had any classes on physics or dynamics. In other words, this may be totally wrong but it's my shot at understanding it.

I was under the impression that pretty much every vehicle will be able to produce enough braking power to lock a wheel, so the power isn't really the problem. The problem is how much friction force the tires will take before slipping, right? Stopping the wheel doesn't stop the vehicle.

That doesn't seem to be dependent on radius. All other tire variables held constant, it seems more dependent on the surface area, which in turn would depend on the weight of the vehicle and air pressure in the tires.

So while it would seem that larger wheels/tires would require a greater braking force, the stopping distance traveled doesn't seem to be any different assuming the tires have the same coefficient of friction and surface area.

So does it affect the brakes? Yes, and I assume the effect is greater wear. Does it effect the distance you come to a stop? Probably not, as that is a factor of the rubber on the tires and not the brake pads themselves.

Sorry, you just failed the oral exam in Physics class...
Here is a non-mathematical blog article which explains it fairly well. The mathematical calculations would probably be too much...
https://www.beefedupbrakes.com/blog/heavier-wheels-tires-braking-distance/

 

[MrZappo]

Sorry, you just failed the oral exam in Physics class...
Here is a non-mathematical blog article which explains it fairly well. The mathematical calculations would probably be too much...
https://www.beefedupbrakes.com/blog/heavier-wheels-tires-braking-distance/

For the record, (and I know weight/mass plays a role) I was mostly referring to the tire circumference ... A larger diameter tire has far more leverage to overcome ...

Mass is one aspect of this but an increase in tire diameter with the same diameter brake disk would make a large difference in stopping ability ... Better pads or more pistons in the caliper would help of course but larger disk would likely help the most ...

If anyone wants proof, look at the disk diameter on a sports car ... Some are close to the wheel size ... That larger brake disk stops far better than typical sized disks ... And a larger diameter would have the same effect (Only it would make stopping worse) ...

I was simply wondering what the collective experience has been in stopping with 35, 37, or 40 inch tires with no corresponding increase in disk or caliper size/capacity ..

 

[Higher_Ground]

Sorry, you just failed the oral exam in Physics class...
Here is a non-mathematical blog article which explains it fairly well. The mathematical calculations would probably be too much...
https://www.beefedupbrakes.com/blog/heavier-wheels-tires-braking-distance/

I read that page and others, it didn't really explain it with any equations or diagrams.

I managed to get a PE, not too worried about any more exams. I can't tell if you're trying to be funny or trying to be a dick...

 

[kcchiefs]

Just curious - do you have stats on that, a study? Or seat-of-the-pants measure?

32 vs 33 vs 35, I'd be shocked to see a difference. There's so very little difference in the leverage the road has over the brakes until you get much larger.
Jeep assumed you'd be changing things - I'd bet they have it all figured in up to a point.

Look at the challenger, the scat pack stops better than the hellcat. The hellcat has bigger brakes and tires. The reason it weighs more due to supercharger

 

[Renegade]

I read that page and others, it didn't really explain it with any equations or diagrams.

I managed to get a PE, not too worried about any more exams. I can't tell if you're trying to be funny or trying to be a dick...

I’m trying to be funny, but probably came off being a dick. You can’t argue with the physics of it though (I guess you can, but you will be wrong). When a tire radius increases, your braking power decreases.

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