Outer Limits 4x4 Board

I'm getting 35in tyres this week but I've heard that whatever % increase you go up on tyre size, you lose the same % in braking efficiency.

Is this true???

If so, what options are there to improve the brakes and what sort of $$$ are you up for. (Not keen to foot the bill for a rear disc conversion)

I can't even get the wheels to lock up if I brake as hard as possible at the moment so I figure any worse would just be plain dangerous.

V8 Middy wrote:I'm getting 35in tyres this week but I've heard that whatever % increase you go up on tyre size, you lose the same % in braking efficiency.

Is this true???

If so, what options are there to improve the brakes and what sort of $$$ are you up for. (Not keen to foot the bill for a rear disc conversion)

I can't even get the wheels to lock up if I brake as hard as possible at the moment so I figure any worse would just be plain dangerous.

Heavier tires, larger rolling diameter, means the brakes have to work harder to do the same as before...

if your going to be legal, they do a brake test when they engineer your car for 35's...

Slotted rotors are a start, but on yotas there maybe bolt on larger discs.. Not sure.

Braided flexible brake hoses are supposed to improve brake efficiency. Good place to start.

Are braided brake lines legal now??

A few years ago, when I had a bike, they were illiegal in qld. I could never understand it because they were such a great product, heaps better than OEM stuff, especially after a few years use. The OEM lines are usually stretched to the extent that you can see them swell if you watch 'em!!


Regards

Yes braided steel brake lines are legal now, not sure if they need engineers etc, but they need to be professionally made i believe.


There was a topic a while ago bout it
http://www.outerlimits4x4.com/PHP_Modul ... ht=braided

They are legal. Straight swap no certificate or anything. Had a guy who owns a mobile business come to a club meeting to talk about it.

Why not investigate a complete set up from an 80 series or such?

unlike nissans, cruisers have fairly decent brakes to start with and if the brakes are in decent condition they will easily pass the brake test even with 35's. Another thing to note is that your braking 'efficiency' does not change as a direct linear relationship with the increase in tyre size. To get the same braking FORCE you need more pedal effort, up to the maximum available braking force for a given braking system. You can improve the pedal effort:braking force ratio by reducing the diameter of the master cylinder, increasing the diameter of the wheel caliper piston(s), changing the brake friction lining material, and tuning the brake balance(bias) front - rear. Probably the easiest way to do this on a cruiser is to get a set of calipers from a 1990- 75 series which have slightly larger pistons and pad area.

Note that you also increase the overall weight of your vehicle and the rotational inertia of your wheel/tyre combo when you go up to a larger tyre size, so you may need to increase the maximum available brake RATE (I don't know if there is a technically correct term for this) which is the rate at which the brake to convert kinetic energy into heat - ultimately the ability of the brake to shed heat, or cope with higher operating temperatures. venting, slotted and/or cross drilled rotors (the factory rotors already have pretty good central venting - make sure it is not full of dry mud), different friction lining materials, and fresh hydraulic fluid all help in this regard.

fresh, braided soft lines will improve pedal feel and fade and are a valuable addition when you're taking your brakes closer to their capacity more often.

cheers

Brian

i recently upgraded my brakes on the middy, used hzj75 calipers and pads. bigger pad area meant better braking. this is one of dumbdunces ideas

my other step was to use a 60 series brake booster to increase brake pressure (double diaphram i think). unforntuneately this didnt work because booster was faulty. oh well. i did note that with 60 series brake booster the brake pedal sits a lot lower than normal, and you also need to move/remove standard fuel filter/water trap



Lance

dumbdunce wrote:unlike nissans, cruisers have fairly decent brakes to start with and if the brakes are in decent condition they will easily pass the brake test even with 35's. Another thing to note is that your braking 'efficiency' does not change as a direct linear relationship with the increase in tyre size. To get the same braking FORCE you need more pedal effort, up to the maximum available braking force for a given braking system. You can improve the pedal effort:braking force ratio by reducing the diameter of the master cylinder, increasing the diameter of the wheel caliper piston(s), changing the brake friction lining material, and tuning the brake balance(bias) front - rear. Probably the easiest way to do this on a cruiser is to get a set of calipers from a 1990- 75 series which have slightly larger pistons and pad area.

Note that you also increase the overall weight of your vehicle and the rotational inertia of your wheel/tyre combo when you go up to a larger tyre size, so you may need to increase the maximum available brake RATE (I don't know if there is a technically correct term for this) which is the rate at which the brake to convert kinetic energy into heat - ultimately the ability of the brake to shed heat, or cope with higher operating temperatures. venting, slotted and/or cross drilled rotors (the factory rotors already have pretty good central venting - make sure it is not full of dry mud), different friction lining materials, and fresh hydraulic fluid all help in this regard.

fresh, braided soft lines will improve pedal feel and fade and are a valuable addition when you're taking your brakes closer to their capacity more often.

cheers

Brian

For a long time I thought you were a knob!
and then you come out with a well worded, informative and technicaly acurate post like this and I don't know what to make of you

Peter.

Brian[/quote]

For a long time I thought you were a knob!
and then you come out with a well worded, informative and technicaly acurate post like this and I don't know what to make of you

Peter.[/quote]


I don't get why people come out with compliments????? like this when its only a matter of time before they ask for people's input and assistance.

Personal opinions aside and to the topic at hand:

If I was to upgrade to 1990 75 series front rotors and calipers, would this restrict / become a consideration in my choice of rims?

V8 Middy wrote:
If I was to upgrade to 1990 75 series front rotors and calipers, would this restrict / become a consideration in my choice of rims?

most 15" rims will still fit. the caliper body itself is only slightly larger on the outside because of some cooling fins. they may require very slight, non-steructural trimming to clear alloy rims and some steelies.

droopypete wrote:For a long time I thought you were a knob!
and then you come out with a well worded, informative and technicaly acurate post like this and I don't know what to make of you

Peter.

I don't suppose there is any way I could interpret "knob" as a compliment, is there?

dumbdunce wrote:

V8 Middy wrote:
If I was to upgrade to 1990 75 series front rotors and calipers, would this restrict / become a consideration in my choice of rims?

most 15" rims will still fit. the caliper body itself is only slightly larger on the outside because of some cooling fins. they may require very slight, non-steructural trimming to clear alloy rims and some steelies.

Excellent!!!! SO long as I can speak with an engineer who will take on this little adventure, I'm going tyre shopping on the weekend!!!!

Again, I'm assuming the offset helps clear brake components etc

V8 Middy wrote:
Excellent!!!! SO long as I can speak with an engineer who will take on this little adventure, I'm going tyre shopping on the weekend!!!!

Again, I'm assuming the offset helps clear brake components etc

usually, yes. don't go crazy with the offset though, it will steer like a cow and you might end up with rubbing issues (did we already do this bit in another thread?)

Hi
I did this when i put 35's on my 60 series.
All you need to do is get some 1990 plus 75 series callipers, and bolt them to your discs, you need to trim a little off the backing plate/splash guard to get them to fit in there, but they bolt to thesame 2 bolts on the anchor frame. Pistons are larger, pads and longer...these were modded when the 1hz came out in the 75. Same rims can be used, everything is thesame.
Lance, the booster was out of an 80 series........i know the 80 booster went on my 60 ok...it doesnt look like the 80 booster fits a 70 as well.
Andrew

V8 Middy wrote:
I don't get why people come out with compliments????? like this when its only a matter of time before they ask for people's input and assistance.

V8 Middy, let the emoticons be your guide
and I was serious about the "well worded, informative and technicaly acurate post" bit
good luck with the conversion
Peter.
Ps, by the way, I have 35"s on my 70 series as well.

ps for even bigger callipers, v6 forrunners fit aswell, and give 4x45mm pistons same as an 80 series. Disc on a runner is thicker, but that doesnt stop the calliper working ok. Also hilux callipers from 90 on will fit and are close to being thesame as the 75 calliper.
All of these options need to use the 90 plus 75 series pads.
Andrew

droopypete wrote:
V8 Middy, let the emoticons be your guide
and I was serious about the "well worded, informative and technicaly acurate post" bit
good luck with the conversion
Peter.
Ps, by the way, I have 35"s on my 70 series as well.

Its always hard to judge the tone of voice when you can't hear it!

I'd love to hear from you in my thread re rim offset etc to know what offset you're running, if and where the wheels rub and if you lost any of your steering lock to achieve this.

Just go off the phone to a mob that engineers tyres and although the guy I really need to speak to was not available, the one I did speak to said that if the tyres didn't rub, they were legal for the rims they were on (no MTR's DOH!), they fitted inside the guards etc and the speedo was re calibrated then that was it!!!

No mention of a brake test! I'll keep you all informed as the process goes on!

V8 Middy wrote:they were legal for the rims they were on (no MTR's DOH!)

Actually the only ones that are recommended for 15x8's are BFG's...

Out of interest, how much would it cost, parts and labour to get the 1990 75 series front rotors and calipers? Where in Melbourne is good to get this type of non-standard stuff done?

V8 Middy wrote:Out of interest, how much would it cost, parts and labour to get the 1990 75 series front rotors and calipers? Where in Melbourne is good to get this type of non-standard stuff done?

rotors are the same (I think). I have a pair of calipers you can have for $100, they are functional but could do with an overhaul if you felt so inclined. labour is jack up, wheels off, 2 caliper bolts and one hard line per side, trim stone guards, bleed brakes - any halfway competent shop should have it done well inside 2 hours so say $130 for labour.