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My woods rail/bug out build.
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Aerindel
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PostPosted: Wed Sep 15, 2021 6:45 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

PhillipM wrote:

So front and rear grip is going to be similar, as is load transfer if the wheelbase and CoG are similar.


Grip cannot be the same, as the weight is not the same.

Grip is determined by a couple of factors, but weight is a big one. Light vehicles will simply never have as much grip has heavier ones.

This is why my 5500lb truck will throw your against the seatbelt when you stomp on the brakes, without even skidding but my 1000lb buggy will just slide when you do the same.

The catch to this, is that heavier vehicles also have more mass to stop, so the total force they have to brake is greater, but generally, heavy vehicles stop better.
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Homemade woods/street, bug out rail. IRS, Balljoint front end. 1967 1600cc DP, Weber 32/36 progressive, tri-mil quiet pack. Rear only cutting brakes.

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PhillipM
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PostPosted: Thu Sep 16, 2021 7:59 am    Post subject: Re: My woods rail/bug out build. Reply with quote

Err, no, not a thing at all.
You will generate more outright grip, sure, but only in proportion to the extra force you then need to decelerate.

And tyres are a viscoelastic, the lighter they are loaded the more friction they generate. That's why you fit big wide tyres to things when you're trying to generate more grip.
Ergo he exact same car with less weight will stop faster, accelerate faster and corner better.


Grip from vehicle weight is only relevant when you're towing something tbfh. Because that's when it's not just offset by the extra weight of the vehicle. It's why heavier vehicles are better for towing with.
The only real exception to that is shallow snow when you have ice spikes and you're trying to cut through that to ground ice for the studs to bite in, when you might go narrow with the tyres (although, you'll still go as *tall* as you can with the tyres, because that spreads your weight over a longer longitudinal contact patch) because hitting the ice with the studs is a better option than going wide with tyres. But if you can't do that then you go with huge tyres for snow, like with arctic trucks. Or tracks.

Just for example, using g-force for cornering, or braking, because that normalises your vehicle weight against your traction, these are pretty standard tyre loads curves, there's thousands of these out there, including for dirt, mud, snow, etc, etc:

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


And yes, that does hold even for M/T and V-tread tyres:

Image may have been reduced in size. Click image to view fullscreen.


In fact as you can see the looser/softer the surface becomes the more it matters.
There's no reason your rail shouldn't brake like a normal roadcar on the same tyres, apart from them having active biasing and ABS. It's just a matter of brake and suspension setup.
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Aerindel
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PostPosted: Thu Sep 16, 2021 1:16 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

hmmm. This contradicts all my driving experience.....and everything locals do in winter, since its very common practice to throw extra weight in your vehicles for winter.


But, science cannot be denied. Sadly.
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PhillipM
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PostPosted: Thu Sep 16, 2021 5:17 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

There's a difference between putting weight over the driving wheels of a vehicle for snow - in that case you're not really wanting the extra weight, you're wanting to change the weight bias.

If you could do that by taking weight out, that would be prefered, but obviously it's much easier to load up.

Same with my RWD cars, I pop blankets, tools and water in the trunk in winter to give more traction from a more rearward weight bias. If the snow is pretty light over tarmac more weight or more tyre pressure might help you cut through to grippier tarmac, like the ice example before, but that's rather situational.


I mean the easiest 'common' if not really scientific example I guess is look at a semi/arctic truck and trailer - they're 40+ tons but they stop way worse than the vast majority of vehicles...


There's a lot of anecdotal evidence for things people think should work without testing or really understanding, just because they're using it to actually do something else than they think is logical.

That's why we end up with things like people on here recommending prop valves in front lines, etc, it's fairly common thing I've addressed before here - somewhat related is the amount of times I've seen, not just here but in threads here over the years, people recommending 'cutting down the brake pads' to reduce friction, with the reasoning that half the pad is half the grip, doesn't work like that. All that happens is you get brake fade and a shedload of brake wear and barely any change.
And as you just found out - unfortunately costing you time and money of your own (and the proponents that float around on here recommending it will handily disappear into the ether when it comes to helping out with either of 'em to correct it) - things like that don't always hold up under closer inspection.


Anyway, I think I've veered off topic enough, do you have any easy options to change calipers, or pads?
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oprn
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PostPosted: Fri Sep 17, 2021 5:33 am    Post subject: Re: My woods rail/bug out build. Reply with quote

The most impressive brakes I have ever driven with are the ones on my '83 944. When I plant my #13s hard on that peddle things happen! My cheeks pull forward and my eyeballs try to leave thier sockets! Without seat belts it's impossible to stay in the seats, you would be jack hammering your teeth out of the dash! The fronts do lock up slightly before the rears and the car is very predictable. This is not a particularly heavy car at 2600 pounds but like PhillipM says weight is not really that relevant to stopping power. Porsche did a bang up job when they designed those brakes!

It would be very interesting to take an accelerometer along in different cars and trucks and see how they compare. Often suspension deflection, or the lack of, gives a false perception of braking power.

It would also be very interesting to see how the brake balance would have been on Aerindel's Buggy had he gone with drum brakes. Mine turned out to be rear biased but then I am running Bus rear drums that were designed for a much heavier car.

I would have to go back and look but maybe he can shift some weight forward to load the front more.
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oprn
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PostPosted: Fri Sep 17, 2021 5:41 am    Post subject: Re: My woods rail/bug out build. Reply with quote

Yes! There is another difference between his Buggy and mine. I have the fuel tank and the battery in the very front. That may help a bit too along with the tallest tires he can fit on the stock rims.
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Aerindel
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PostPosted: Fri Sep 17, 2021 8:08 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

Quote:
Anyway, I think I've veered off topic enough, do you have any easy options to change calipers, or pads?


Nope.

Pretty much my only option is to put in a whole new pedal set with a balance bar.

I still have a little hope the new tires will help...but I can't put them on right now because my wife was just listed as a covid close contact from work (she works at the hospital) so now she is living in my shop for four days until a valid test can be run and I'm 'stuck' in the house.

But I will freely admit, my current front tires are total crap, which never mattered much because I didn't have brakes on them...so there is a chance some new tires with tread and....flexibility....could help.

I guess I could also move my fuel tank and battery up front, but I'm not sure that would be any easier.

Quote:
t would also be very interesting to see how the brake balance would have been on Aerindel's Buggy had he gone with drum brakes


I can only assume it would be less of a problem given that drum brakes usually don't brake as well as discs. I wish I had just gone that way but as the price to buy drums from scratch wasn't that different from the price for discs I went with discs simply because discs are considered 'better'. lol
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Homemade woods/street, bug out rail. IRS, Balljoint front end. 1967 1600cc DP, Weber 32/36 progressive, tri-mil quiet pack. Rear only cutting brakes.

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PhillipM
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PostPosted: Sun Sep 19, 2021 4:19 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

Some new tyres in as soft a compound as you can find might be a big help, yes, especially if you go up a little on the height.

I don't know if you guys can get them over there but here you can buy Fedima and Insa tyres in soft race/rally compounds as well as the normal 4x4 road car options - they're much better on a light buggy/rail where tyre wear doesn't matter as as ozone/UV degradation normally takes 'em out first.
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Aerindel
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PostPosted: Sat Oct 02, 2021 5:58 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

So I got the new tires on....situation improved!

However, the proportioning valve stuck and starting acting like a residual pressure valve....as in it would not allow the front brakes to fully disengaged.

POS.


Anyway, since its been shown to me that solution would never work anyway.

Whats every bodies recommendation for a pedal set that WILL work, as in one with a bias bar etc.??
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PhillipM
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PostPosted: Sun Oct 03, 2021 5:22 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

Depends how much fabrication you want to do - plenty of places sell a kit with a balance bar, spherical bearing and a housing to weld into a brake pedal, then you'd have to make mounts for the cylinders, of course.

We got a Tilton 600 series in ours just because it was relatively cheap, light and easy to get replacements for instead of messing around making customs:

Image may have been reduced in size. Click image to view fullscreen.


They're a pretty neat, well made setup, little pricy compared to just making something though.
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Aerindel
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PostPosted: Sun Oct 03, 2021 7:18 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

At this point in time, I think I just want to solve the problem rather than spend the next two months in my shop building something from scratch.

That being said....I'm not sure what you mean by:


Quote:
plenty of places sell a kit with a balance bar, spherical bearing and a housing to weld into a brake pedal, then you'd have to make mounts for the cylinders, of course.


Do you have an example?

Sorry of all the questions. I'm just a little worn out at this point at spending money on things that don't work and want to be sure I am doing the right thing for the next step.
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Mike Fisher
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PostPosted: Sun Oct 03, 2021 7:37 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

PhillipM told you he runs Tilton 600 Series pedals because they are relatively cheap.
I would call that 'an example'.
Looks like they have many different bolt in setups for sale at Jegs & Summit etc.
https://www.google.com/search?q=tilton+600+series+...nt=gws-wiz
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Aerindel
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PostPosted: Sun Oct 03, 2021 8:34 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

ah, so that is the 'kit' then. I thought he as talking about something else.
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Aerindel
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PostPosted: Sun Oct 03, 2021 9:05 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

So ,at the moment, I'm thinking of this assembly:

https://www.amazon.com/Wilwood-340-12410-Pedal-Ass...B00GIHNOGQ

As its relatively cheap, has all three pedals and appears to have a balance bar etc.

Also, my other MC's are wilwood brand so presumably would be compatible so I could switch those over and just buy the smallest MC I can find for the front brakes.

Its also a floor mount like my current pedals so should be fairly easy to mount to the same floor plate.
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PostPosted: Mon Oct 04, 2021 4:40 am    Post subject: Re: My woods rail/bug out build. Reply with quote

Remember that in hydraulics a smaller master cylinder will give you a higher force at the wheel cylinder with a given peddle pressure. if you want to reduce the effectiveness of the brakes then a larger master cylinder is required.

After this discussion I too am giving up on the proportioning valve idea. Mine just eliminates the rear brakes completely and on disassembly I cannot see how it could do anything else the way it is designed. And like Aerindel says these sand rails don't stop worth a crap on front brakes only.
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PostPosted: Mon Oct 04, 2021 8:50 am    Post subject: Re: My woods rail/bug out build. Reply with quote

If you go with Wilwood you can add Wilwood 340-4990 Remote Brake Bias Adjuster Cable. Maybe the bias knob will fit others??

https://www.amazon.com/Wilwood-340-4990-Remote-Bra...&psc=1

If you want as much adjustability you can get one big master cylinder and one smaller. Then you can set the balance bar to the middle, drive the buggy. If needed swap the masters to get the best braking. After that you can use the brake bias knob on the fly. Works great this way.

On mine the rears where locking up before the front. I put a smaller master on the front along with the balance bar centered and my brakes felt very even.
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Aerindel
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PostPosted: Mon Oct 04, 2021 11:58 am    Post subject: Re: My woods rail/bug out build. Reply with quote

oprn wrote:
Remember that in hydraulics a smaller master cylinder will give you a higher force at the wheel cylinder with a given peddle pressure. if you want to reduce the effectiveness of the brakes then a larger master cylinder is required.

After this discussion I too am giving up on the proportioning valve idea. Mine just eliminates the rear brakes completely and on disassembly I cannot see how it could do anything else the way it is designed. And like Aerindel says these sand rails don't stop worth a crap on front brakes only.


Right, the MC pistons bore size to force is reversed to that of a the calipers.

They don't stop worth a crap, but even worse, they don't steer....at all.

It was a struggle just to get my rail turned around and parked with the front brakes locking up at the slightest touch of the pedal.


Quote:
If you want as much adjustability you can get one big master cylinder and one smaller. Then you can set the balance bar to the middle, drive the buggy. If needed swap the masters to get the best braking. After that you can use the brake bias knob on the fly. Works great this way.


Thats my plan. I assume the bias bar has a limit to how much bias you can shift so I want to start off with as much rear bias built in as I can and then dial it in with the bias bar.
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Homemade woods/street, bug out rail. IRS, Balljoint front end. 1967 1600cc DP, Weber 32/36 progressive, tri-mil quiet pack. Rear only cutting brakes.

http://www.thesamba.com/vw/forum/viewtopic.php?t=630046
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PostPosted: Mon Oct 04, 2021 1:01 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

Oh when I say a weld in kit I mean like this:

https://www.waltonmotorsport.com/product/obp-bias-...BsQAvD_BwE

And yes, you want the small M/C on the rear and the larger one on the front.
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Aerindel
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PostPosted: Mon Oct 04, 2021 2:16 pm    Post subject: Re: My woods rail/bug out build. Reply with quote

PhillipM wrote:
Oh when I say a weld in kit I mean like this:

https://www.waltonmotorsport.com/product/obp-bias-...BsQAvD_BwE

And yes, you want the small M/C on the rear and the larger one on the front.


Ah, ha. Thanks.

Yes, I see how that could be done. Aerindel of a few years ago would probably have gone that rout and just built pedals from scratch but currently I have more money and less time.
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Homemade woods/street, bug out rail. IRS, Balljoint front end. 1967 1600cc DP, Weber 32/36 progressive, tri-mil quiet pack. Rear only cutting brakes.

http://www.thesamba.com/vw/forum/viewtopic.php?t=630046
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PhillipM
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PostPosted: Tue Oct 05, 2021 5:24 am    Post subject: Re: My woods rail/bug out build. Reply with quote

Yep used to do the same and now it's just "We can work more and buy a Tilton and it comes out less labour hours" Laughing
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