[CCJ]

Originally Posted by mcg311TJ

This is getting good.

Yeap I'll join.

[DocMojave]

I just put 35" Goodyear MT/R's on today so after I drive it around a little Ill report back with my discovery's. I have to say that I wasn't real happy with my brakes performance on the 33"s so this should be interesting.

[Knuckelhead]

Originally Posted by Varnish

I'm gonna wait & see how they do in 4low pointed steeply downward on the trails before making a call on upgrading em.

You'll upgrade em...

[fratis]

Originally Posted by mcg311TJ

I have stock brakes and 35"s.... ... If I had the money, would I get larger/better brakes? Sure who wouldn't? It work well enough for me right now.

ill apologize ahead of time for what will seem like picking on you. you are by far the norm and not doing anything uncommon.

so if you had the money you would upgrade your breaks? breaks being the most important thing on your vehicle. so you had the money for 35" tires, 4 kc daylighters, etc. but now you are out? this is what ill never understand. also how will you determine when "right now" is over?

[Bishop Creek]

Just waiting for mrblaine to show up.

[MisfitSeven]

Originally Posted by DocMojave

I just put 35" Goodyear MT/R's on today... blah blah blah ...I wasn't real happy with my brakes performance with the 33"s.
so this should be interesting.

smart. real smart.

[elkfan2]

Originally Posted by CCJ

Yeap I'll join.

Count me in to.

[never monday]

Originally Posted by lukethedork

Nevermonday, can you tell us your standards of what is acceptable for braking? Is it when your bum feels like it is going to slide forward off your seat from an emergency stop?

that's the way my 911 worked. It seemed good enough.


If your getting at my conclusion being subjective and yours scientific. I have nothing for you.

[nicolas-eric]

Here in Germany I also passed the brake test with stock brakes and 35s.

[Junky burp]

Where do you get the popcorn?

[rainmn]

Originally Posted by never monday

that's the way my 911 worked. It seemed good enough.

Yep, my 993 could just about put you through the windshield. I thought that was acceptable.

[justanotherjpr]

I thought the brakes on my 99 TJ with 31's were weak. Can't imagine running 35's on those brakes and feeling safe..

[Bishop Creek]

Originally Posted by Junky burp

Where do you get the popcorn?

In the lobby.

[jmasin]

Originally Posted by lostsheep

There is enough data here? Link? I would really like to see some quantified results of braking distances with and without brake upgrades. I would also like to compare these data to a scale with reference points; ie motorcycle to big rig stopping distance. I wonder if the percentage change in stopping distance varies linearly with percentage change in diameter? Can anybody show this theoretically? Please do not chime in if you cannot draw a FBD or use the appropriate language (math).

This was covered here recently in another brake thread, and it is actually fairly simple math. I don't have stopping distances because I don't know the values of the constants, but it could be figured out.

There are three key things at work in braking

1. The friction force applied by the pad to the rotor resisting rolling, this results in "brake torque". The amount of torque is linearly proportional to the distance of the pad from the center of rotation (axle). T=r * F

2. The rotational inertia of the wheel/tire assembly. This is proportional to the mass of the tire/wheel assembly and the center of mass relative to the axis of rotation. I=m * r^2

3. The friction of the tire/road and the torque applied by this force. This again is torque (T=r * F) and is in the opposite direction of the brake torque.

To stop a vehicle, #1 must oppose #2 and #3.

You can easily see by increasing the tire diameter, ALL ELSE EQUAL, the torque due to friction with the road increases (#3 goes up). Since all else has remained the same, stopping distance will increase.

Same story with heavier tire/wheel. #2 increases due to an increase in mass. Move the center of mass outward and it increases proportional to r^2.

In the track world (where I cut my automotive teeth) it is very common to see people go +1 with rotor sizes if wheels allow. Moving the brake pad out increases brake torque a significant percentage and improves braking assuming you can maintain grip (achieved by going to slicks/DOTRs).

The only way moving to larger tires does not increase stopping distance is if you are already traction limited, and by this I do not mean in a stab-at-the-brakes lockup condition, I mean in a hard braking threshold condition. If you are not traction limited, increasing tire diameter WILL NECESSARILY decrease braking effectiveness.

Cheers!
Jon

[mcg311TJ]

Originally Posted by fratis

ill apologize ahead of time for what will seem like picking on you. you are by far the norm and not doing anything uncommon.

so if you had the money you would upgrade your breaks? breaks being the most important thing on your vehicle. so you had the money for 35" tires, 4 kc daylighters, etc. but now you are out? this is what ill never understand. also how will you determine when "right now" is over?

fair enough, I have the money ( if needed ) But my breaks are working well enough right now. I got my junk over time and then started putting on all at once. After the lift and tires were on, I went for a ride and the brakes worked fine. So I said to my self, Will wait a month and see how there holding up the month came and went, It's been 3 months now, all good.

So to answer your question, when these brakes start to loose there grip... I'll up grade. If it ain't broke, don't fix it.