Diet Taco... trying to keep things light

Thot this was Dicks thread.....

@DVexile

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I recommend designating them as Bay 1, Bay B and Bay III

No worries! To be fair I really haven't done anything to my truck in 9 months so I can see how you confused it for his thread...

 

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+3 DMB

 

Effect of Vehicle Weight on Braking Performance
There are two primary performance parameters for braking. The first is the distance it takes to come to a stop from a given speed. The second is the amount of braking that can be done before the system overheats and becomes ineffectual. Weight affects both but not necessarily as one might expect at first glance.

Braking Distance
Combining Newton’s Second Law with the equations for one dimensional motion and performing some substitutions and rearrangements gives the equation for the distance d to stop a vehicle:

d = 0.5 * (m / F) * v^2​

where m is the mass of the vehicle, F is the force decelerating the vehicle and v is the speed of the vehicle.

It is easy to make a quick but wrong conclusion that if we increase the mass by 10% that the distance will also increase by 10%. The issue is we don’t care about the distance for a fixed value of force, we care about the shortest stopping distance we can achieve which depends on the maximum force that can be applied to the vehicle. It turns out that the maximum force isn’t a constant but actually depends on the mass of the vehicle itself.

Pedal Force
Applying a force to the brake pedal transfers an amplified force to the brake rotors to decelerate the vehicle. In theory increasing the mass of vehicle or otherwise altering the brake performance (e.g. different sized wheels, different rotors or pads) changes the required pedal force to achieve the same deceleration of the vehicle. As a practical matter though this is not what limits the performance of a mildly overloaded vehicle. Modern vehicles have significant reserve braking power and modest pedal force results in the ABS system activating to maintain traction. Once the ABS system is activated pedal force is irrelevant and it is the maximum friction force the tires can generate without slipping that limits the deceleration of the vehicle.

It is easy to verify if this is true for any given vehicle at any given load. Find a safe open space on dry pavement and attempt to panic brake. If ABS activates then you don’t need to worry about your brake booster, calipers, pads or rotors being a limiting factor in braking performance for your vehicle weight. Similarly if this is the case then “upgrading” any of your brake components will do nothing at all to reduce your stopping distance.

Tire Traction and Friction
Assuming braking results in ABS activation the stopping distance of the vehicle is limited by the amount of friction force the tires can apply to the vehicle. We have an equation for stopping distance based on mass and force so all that is left to do is determine how mass affects the amount of friction force the tires can apply to the vehicle.

High school physics books will tell us the equation for friction force F is:

F = k * W​

where k is the coefficient of friction between the object and the surface it slides on and W is the weight of the object. Remember that weight is mass times the acceleration of gravity:

W = m * g​

So if we substitute all that into our stopping distance equation we get:

d = 0.5 * v^2 * m / (k * m * g)​

The m’s cancel leaving:

d = 0.5 * v^2 / (k * g)​

Which implies you can put as much weight as you want on and your truck will stop in the exact same distance as before.

Well, not quite. The equation given for friction above makes sense for rigid objects like metals, wood and stone. For a pneumatic tire the coefficient of friction actually goes down the more weight you put on the tire. Or put another way if you double the weight of the vehicle you end up getting a bit less than double the friction. The modified equation for friction with pneumatic tires looks something like:

F = k * W^r​

where the exponent r ranges from 0.7 to 0.9 instead of the ideal of 1.0. We will assume that our tires are not the worst on the road but probably sort of bad at stopping as they are meant for off road performance rather than racing. We will choose our estimate of r to be 0.75 as a pretty conservative number. Dumping this adjusted equation for friction into the algebra machine and rounding up all the constants and factors of two as a single constant C we now get:

d = C * v^2 * m^0.25​

For our purposes is doesn’t matter what the value of C is as we are just interested in how d changes as we increase m (that is, add mass to the vehicle). The distance only increases as the one fourth power of mass which means it is quite insensitive to added weight. As a specific example if we increase the mass of the truck by 10% (so adding 550 lbs past GVWR for the Tacoma) the stopping distance only goes up by 2.4%.

We can double check our model by looking at some test data. This test of a 2015 TRD Pro is a good data point since it uses a suspension and tires similar to “expedition builds”. Stopping distance from 60 mph at 4,380 lbs was 159 ft while at 5,500 lbs it was 167 ft.

Based on the measured 4,380 lbs stopping distance our model predicts the 5,500 lbs stopping distance would be:

159 * (5500/4380)^0.25 = 168 ft​

Looks like we are on pretty solid ground with our model. And we can extend a bit further to see the impact of going 10% past GVWR:

167 * (6050/5500)^0.25 = 171 ft​

So slapping on 550 extra pounds beyond GVWR has made the truck only take an extra four feet to stop from 60 mph. Not something to lose sleep over.

It is worth noting there is actually a regulation for braking performance on new vehicles in Title 49 CFR 571.135. For a GVWR of under 7,700 lbs. the vehicle should stop in less than 230 ft. Even our overloaded Tacoma meets that requirement by a large margin. And taking our model well past the breaking point it predicts we’d need to somehow put 19,800 lbs on the chassis before it takes 230 ft to stop (though of course it will probably stop much faster at that point since the chassis will have collapsed).

Towing
A word on towing and stopping distance. The Tacoma owner’s manual indicates it is safe to tow up to 1,000 lbs with an unbraked trailer. Note that in the case of towing that no additional weight is put on the tow vehicle’s tires (beyond the tongue weight of course) and so we do not get any additional tire traction to offset the increased weight being braked. So in this case the braking distance does go up with weight linearly. Assuming a tongue weight of 10% of the trailer weight and reducing the vehicle payload by that tongue weight we would have a GCW of say 6,400 lbs and a GVW of 5,500 lbs if we towed a 1,000 lbs trailer with the vehicle at GVWR. In this case the stopping distance would be:

167 * (6400/5500) = 194 ft​

This is significantly larger difference than if the same 1000 lbs was on the chassis rather than on a separate trailer but still comes within the regulated 230 ft stopping distance.

Also realize that passenger vehicles (i.e. not tractor trailer rigs) towing large loads are likely incredibly unsafe as far as braking distance goes. There are in fact no regulations on this and the recently adopted industry “standard” for tow ratings allows for insanely long stopping distances.

Things are a bit confusing because of different starting speeds for different regulations and standards but we can normalize them to a common 60 mph stopping distance. As stated earlier passenger vehicles below a GVWR of 7,700 lbs must stop in 230 ft from 60 mph or equivalently 30 ft from 20 mph. We probably all think a tractor trailer takes a long way to stop, but in fact a loaded 70,000 lbs tractor trailer rig must stop in just 250 ft from 60 mph.

Recently the SAE worked with manufacturers to come up with a standard for tow ratings called J2807. This standard allows a vehicle towing a braked trailer above 3,000 lbs to have a stopping distance of 80 ft from 20 mph which is equivalent to 613 ft from 60 mph or more than a tenth of a mile!!!

So again, a 70,000 lbs tractor trailer rig must stop in 250 ft but Joe Zoomy-Zoom coming back from tearing up the dunes towing his quads and a giant camper is given 613 ft to stop. Just a little side observation for anyone who might think regulations and standards are a replacement for common sense.

Overheating and Brake Fade
The other limitation in brake performance is the duration of braking such as when going down a long grade. Brakes work by converting the kinetic energy of the vehicle into heat. Eventually the brake system can get hot enough that the brake fluid no longer effectively transmits force from the pedal to the calipers. At this point we get “brake fade” in which the brakes appear to no longer work.

This post has already gotten rather long and the analysis for this is long and boring, but essentially the “worst case” is that for a 10% increase in mass you would only be able to ride the brakes for 90% as long before overheating. Unlike the distance to stop a vehicle this is really easy to mitigate - don’t ride the brakes. Use low gears like you are supposed to.

We can also get a little idea of whether the Tacoma has a problem with overheating brakes by looking at some tests. All vehicles need to pass a brake fade test in Title 49 and in our earlier linked test the Nissan under test did eventually start having brake fade after repeated stops while the Tacoma did not. So since the Nissan passed the Title 49 tests that tells us that Tacoma has got more brake cooling than necessary to pass the test.

So for modest overloading (10% to 20%) we don’t need to worry about brake overheating on the Tacoma but we would always be wise to make intelligent use of low gears.

Conclusions

• The Tacoma is rated to tow an unbraked 1000 lbs load which already implies it is “safe” by some measure the manufacturer considers reasonable to brake about 900 lbs above the GVWR.
• Unless you put really large tires on or drastically overload the vehicle the brake system itself will not be the limiting factor in determining stopping distance. You can check this yourself by panic stopping and seeing if ABS engages.
• When limited by tire traction the stopping distance is quite insensitive to added weight. Increasing the weight by 10% only increases stopping distance by 2.4%.
• Brake overheating worst case increases linearly with mass and is easily mitigated by proper driving technique.
• The Tacoma appears to have plenty of reserve braking performance based on tests of stopping distance and brake fade.

In the final analysis it appears the brakes are in no way limiting safety for a Tacoma loaded well beyond the GVWR. Adding up to 1000 lbs past GVWR would still result in a vehicle that can stop in a safe distance both by federal regulations and manufacturer recommendations.

 

I can't stop coming back to this thread. Amazing work. So no fancy off-road lights or bars?

 

Thanks!

Not so far but I'm still undecided. If I did something it would probably be a light bar in the lower grill, potentially a "stealth" install behind the grill itself.

Originally I assumed I'd do a light bar for sure at some point but since doing the fog lights anytime mod and having done a few night runs I'm pretty happy with the stock high beams plus fog lights. I really don't run at night very often, especially if family camping we are usually at our site before dark. I have done Saline Valley from the south entirely in the dark a few times now but that is a road I'm very familiar with. I've done some shorter night runs (5 or so miles) on unfamiliar roads when making a late camp solo.

What I've found so far is the stock brights keep up with what I consider a top "safe" speed of 45 mph on a good dirt road at night. With the fogs on at the same time I get plenty of light to the sides when doing tighter turns and the lower illumination angle from the fogs shows ruts and rocks well so that I can slow down in time for those. So now I'm doubting if I really need a light bar. The weight really isn't an issue nor is the cost. Mainly I'm just prioritizing the time involved in selecting one, getting it shipped to where the truck lives and then figuring out time for me to actually do the installation. I've already got probably a year's worth of "to-dos" given the limited time I have to do work or mods on the truck since I'm now on the other side of the country from the truck and any work I do is "steeling" from my vacation time actually using the truck.

I do wonder though if a light bar is one of those things you don't know what you are missing until you try it! Certainly I've been in situations in the dark in unfamiliar places where I'd like some more light. In those cases though I usually want more light off of the road, like when looking for side roads or camp spots. One thing I was considering was just getting an uber bright LED flash light - an insanely bright hand held one. That would help for checking out an area for camp spots or other features. I know having read around that most cops find their vehicle mounted spots that are by the review mirror to be pretty useless and they prefer to just use a powerful hand held spot light/flash light instead.

So anyway, no plans for now but maybe in a few years when I running out of things to waste time and money on I'll put a light bar in the lower grill.

 

I'm planning on only 2 light mods. No, 3.

First, I wanted some legit fogs for snow and rain and dust and...fog..., with amber lenses, and a broader/longer dispersion pattern than OEM. I got the Baja Design Squadron R Sport wide corning yellow fogs in the fit kit for the OEM location, set them at level (zero degrees relative to her mounting bracket on the bench top), and have found that I will definitely need to rotate them down 5 or so degrees to use them as true fog/driving lights. Coming down from Donner Summit on I 80 in the middle of the night, I could see I'd be blinding oncoming drivers. Not an offroad concern, but also not what a fog should do.

The next light mod I intend is a pair of Baja Designs S2 Pro driving combo, clear lens, for adding to the front of Prinsu rack to provide additional forward light in challenging conditions (ultra dark unknown trails and roads, like one remote, windy and wooded road in Utah with pure black cows standing inches from the shoulder were essentially invisible in my headlights until I was within a few feet of them and they turned their heads, still have a brown stain in my BVDs from that), and mounting them slight angled to the sides similar to a typical ditch light mounting. Mounting them high will provide the added benefit of still having good forward light should the headlight become covered in mud or snow in nasty conditions.

The last is pair of Rigid diffused flood rear-facing from the Prinsu Cap-rack for the purpose of auxiliary works lights, camp set up, and trailer ops.

Trying to keep it all small, light, sensible, and low-drag.

 

Nice! Looks like a well thought out plan - and even some parts on the shelf already too.

I can imagine if you encounter actual fog then swapping out the stock fogs makes a lot of sense. I'd looked at swapping out the stock fogs for just "more light" for my off road use but none of the options seemed to throw around that much more light than stock. I'm pretty happy with my near field light and the fogs blend nicely with the high beams as is.

Those S2's up on your rack should be nice. That's one thing I've been wondering about is how effective is a bar mounted low. I know lights up high can blind you with hood reflections but proper mounting and shading would fix that I'd think. With the Flip-Pac I'm not likely to be mounting anything up high. Certainly I could make something fit but I don't feel like doing an install on the roof solely for lighting. With a rack there already that seems like a great idea for your rig.

Camp lights on the back would be a nice touch. I've seen a few rigs in camp with those. Especially if you are setting up a camp site really useful. With the Flip-Pac I don't really set up anything outside the truck though! I've considered putting a LED tape strip along the bottom edge of the Flip-Pac door though so when open it illuminates the tail-gate area where I often prepare food. The famous Dave Bennett did that with his Flip-Pac and it looked really nice. One of the options for my Flip Pac lighting mods whenever that happens (2020 maybe?).

The BD stuff looks nice if expensive. I think if I end up doing anything it will likely be a 30" S8 in the Driving/Combo setup with their mounting bracket for the Tacoma. I'm getting into the pay/cry/bleed once approach to things as I get older so sucking up the BD prices is probably what I'll do. With that solution I'd be within my "order of magnitude or don't bother" threshold for adding components. Stock brights are about 1350 lumens per bulb or 2700 for the pair. The S8 is 12,000.

Really, in the end I think I need to sit in a truck with a lower grill mounted bar just to see if I think it is all worth it. No rush for me though...

 

Yeah, we used to get A LOT of fog in the Sac Valley in winters, and it has been surprisingly reduced or absent in the last decade, but I'm sure it has nothing to do with fake climate change.

The OEM headlights are a significant improvement over the 1st gen, and with high beams, yeah, I don't even understand why people would need light bars unless, as you indicate, the idea of mounting something down low to cast different shadow on low road surface obstacle (whoops, etc.), or in the case of headlights becoming fouled mid trail. But I think the OEM headlamp lateral throw is weak, and am interested in supplementing that. The only other times I think anyone would need a big bar is for running through Baja backcountry at Warp 9 when you need to see 1000 yard ahead. Or for find a parking spot when you go to Foot Locker and Abercrombie and Fitch.

For backing and turning the trailer into pitch-black camp sites at night, or even in other poorly lit areas on road, having a rear lighting angled out a bit is a big help, and the need to cast it back beyond, and either side of, the trailer to some degree is important. I had the trailer guy install a large LED reverse lamp as a custom touch, but its effectiveness in real-world situations is not adequate. At least other bozos behind me can be alerted to my intentions.

 

Agreed. I'm pretty happy with OEM brights + fogs after doing the fogs anytime mod but I'd like to have the option when off road to throw a bit more light to the sides.

Bars seem overkill to me - at least for my uses.

Yeah, trailer would be a bitch I imagine. Right now my LED replacements for the back-up lights are barely sufficient for backing up off-road. Much better than OEM of course, but again I could use more light to the sides for when backing in a tight turn. Don't think I'll make any changes to the back at this point, but what you are doing making combined camp work lights and back up lights is very sensible.

As of now having been goaded into looking at this more by @adadandhistruck and your post (my wallet hates both of you by the way) I think if I do anything it looks like the Baja Designs Squadron-R Pro Driving/Combo replacing the OEM fogs is my most likely path. Each light is 4900 lumens, half in the 42˚ wide and half in the 9˚ spot. A pair is 9800 lumens which is a bit more than a 20" S8 bar and a bit less than a 30" S8 bar!

So as a pair that means effectively throwing 4900 lumens into the brights pattern and 4900 lumens into the fog pattern. The OEM is about 2000 lumens in fog and 2700 lumens in brights. Upgrading to the BDs I'd lose the OEM fogs but still have the OEM brights on. So for trail running I'd go from 2000 to 4900 in the wide/fog pattern and 2700 to 7600 in the brights. Or about 245% increase for fog/wide and 280% increase for bright/spot.

I would of course no longer be able to run fogs on the road, but I really never do that anyway. Basically my fog lights would become trail lights. From a time perspective this looks to be a 30 minute job just adding a screw in bracket and harness adapter. I've already done the fogs anytime mod of course. And just $500... ouch.

 

Damn didn't expect to get such a detailed response. I did the same to you earlier about sliders. Sorry! LMAO. Im in the same boat as you... Doing mods thoughtfully and slowly. Taking trips and then deciding what I need. So far I just run a softopper for sleeping under, water pressure pump system from @ProForce, tires and some interior protection. For sure coming up is sliders and maybe upgrading the head lights and fogs for running the mountain trails this summer at night. Don't wanna go too crazy with my prerunner but so far I've gotten to some cool places with it.

 

Well Baja Designs is expensive across the board while Cali Raised is some of the best bang for the buck around.

Issue here is the BD is not really a fog replacement, rather it is an alternative to a light bar coming in at 9800 lumens for the pair with a well designed light pattern mix of narrow and spot. No new wiring, no new electrical load. I've never lost a light to rocks since I don't travel in caravans but BD does have user replaceable lenses. But of course the price ($450 for the whole kit with TW discount).

The Cali Raised are amazingly priced at $130 but they don't do what I need. Slightly less than half the power and all in spot. The whole reason I did the fog anytime mod was because there wasn't enough light being thrown to the sides so the CR in this case do the opposite of what I want.

Where Cali Raised is really compelling is the 32" bar mounted in the lower grill at 28,000 lumens for $280. That is a combo bar so would answer my needs for light pattern. Does add 25A load and associated wiring. I do sort of wonder about blocking the lower grill though. I assume Toyota put it there for a reason - after all the grill increases drag on the vehicle and they could have improved mileage slightly by not having a grill there. I run in really hot places, but then again I don't tow. Probably not worth worrying about.

Anyway, right now the most likely outcome is no additional lighting as I think I'm good with stock plus the fog anytime mod.

No worries, it is all good and provokes good discussion! Haven't bought either yet

You are doing it the right way, don't rush. I slapped a bunch together in the first year because there was that one year we were living in CA so it was easier to do mods. But waiting has paid off more than once already. I did the raised floor as a quick, cheap thing to try before coming up with a fancier build out. Now I know I'll stick with the simple raised floor for the duration. Does everything I need and way more flexible than a complicated build. I had really complicated ideas for Flip-Pac lighting but first I did a real simple mod to the existing lights to provide red or white selection and that actually seems to be almost all I need. I actually prefer a fairly dark camp I'm finding and so just those two lights and headlamps is proving to be almost all I need.

So definitely go slow and figure out what you really need before jumping in!

 

I got the Sports, which are about half the price and fewer lumens, of course. Plus, be on the lookout for a Baja Designs sale or special offer. That's when I bough mine.
https://www.bajadesigns.com/products/squadron-r-sport-pair-wide-cornering-amber.asp

Yes, in general, they are not cheap, but you can swap out lenses and bezels to change them if you wish. And the material and workmanship are outstanding. I also think those with the capacity to do so would find their lumen ratings legit, not BS. Same with their patterns. But again I have a different approach for what I was doing in the wide cornering/fog arena, and anticipating to spend more on the additional off-road illumination up top.

 

I understand why BD is expensive. Lifetime warranty, company around for 20+ years, very nicely engineered products. Photos of their light patterns show careful and thoughtful design. Lots of data and images showing they know how to properly drive and cool LEDs.

So if I understand correctly from you there is some adjustment of the angle you can do in their mounting in the factory fog location? Ability to fine tune that is desirable - I don't like a blinding foreground so being able to tip up as needed would be useful. I'd be doing exactly the opposite of what you are trying to do with the angle!

The idea of swapping the fogs for nothing remotely like a fog is kind of intriguing. As someone in the BD thread said:

Using a squadron pro to replace a fog lamp is sorta like using a wood chipper to sand your coffee table.

But that's exactly the effect I'd be going for. Using the factory fog locations to throw light-bar amounts of illumination around.

 

LOL. I thought I linked to my thread where I set them perpendicular to the bracket (zero degree base line) on my bench top.

My idea was do this upon initial install, then later use a digital angle gauge to change them (i.e., rotate the bracket) methodically until you reach the angle/pattern you seek. Of course, doing this with any precision requires pulling them off the truck and back onto the benchtop, I think. You could put the angle gauge on the stainless bracket. If you had a spare set of hand, you may be able to do this while installed and have a helper operate the gauge on the face of the light while you loosen and nudge the light from the backside. Have I done any of this adjustment, yet? No.

To initially square up the brackets with the lense faces, I just used some aluminum stock of various thicknesses because it was quick and allowed me to quickly and easily tighten the mounting bolt without messing up the angle.

 

Dude, you originally linked to your thread where the lights got delivered on page 58 of your thread. By the time I clicked to page 61 where a cat Vigo the Carpathian is featured I figured there wasn't anything more to be seen.

Thanks though now for the link to page 76 when you actually did something with them! I'm guessing you put your inventory control bar codes on them around page 65?

Seriously, thanks for the link, description and the photos. Helps me understand better what's going on. If I ever get them and attempt to adjust them it will likely be a totally ghetto procedure done in the middle of the desert by myself. Likely outcome is my truck will look like Peter Falk in Columbo. Which would be appropriate since apparently a TW build is all about "Just one more thing..."

 

Page 64, actually.

OK, so look, since you'll have limited resources, consider that with mine set at zero with the wide cornering optics, I was still lighting up a significant amount of upper tree trunks down my street, and coming down from Donner summit, larges swaths of woods above and beyond the roadway. I never got any pictures of this that satisfied me, and the yellow lenses sort of mess with your perception the blast zone, especially when much of the zone is greenery.

I think you just have them shipped to your home, set them at zero at home before you deploy, and they will be lighting up what you need.

Oh, another thought. I've got damn near no rake right now with my stock suspension and the cap and other junk on the back. Do you have any rake with your setup? That could warrant a couple degrees right there.

Whatever you do, don't Feldmanize it.

 

Subbing for future reading and possibly making my fat pig of a 4cyl lighter..... probably not bUT I got to page 10 and I like where this is going

 

Very well thought and out together build!!! Reminds me of my truck before I went full potatoe on it. Unfortunately my own truck will never be as light in full camping trim, pushing 5300lbs in dd form, but I love the trip reports again very well done sir