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Old 02-11-2020, 12:23 AM   #1
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Join Date: Apr 2019
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Default Noob brass question

So... I was reading throughout the internet.. And found a lot of specific answers. I can't put my finger on the "right" advice, because it is obviously a situation based answer. I have a hybrid sport, with a 2 speed tranny, YR aluminium axle housings.. And I had some cash around which I hurriedly spent on brass parts, before I had to buy some silly things like food or something house related. So.. I was so proud having front portals and C h7bs in brass, only to hear that it could be to much, and I'll need to compensate in the rear. So I ordered some rear portal covers, and those round things that bolt to portals. I'm still waiting for the rear set to arrive, but.. How to decide where to use the weights? I'm surre that all out brass isn't necessary a good thing, but since I am out of money, and packing some brass.. How to best discern where to place it? Is there an equation of some sort? I've heard about the 60/40 bias, but how to measure front /rear weight.. I can't cut my rig in half... I'm running a lexan XJ body.. So it's not that heavy. The rig is over 8 pounds atm.
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Old 02-11-2020, 03:33 AM   #2
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Default Re: Noob brass question

Hi,
I can give my experience with 2 years and more then 300-400 miles running the trx4 long wheel base.

In stock form without any brass added, the Center of Gravity for the trx4 is too high. The portal design is part of this. But also because of the portals you have the best possible place to put more weight.

The 2 ways to change CoG is to remove weight from different places OR to add heavy parts on different places.

So what i did was this: I don't care so much about full scale look, so i removed a lot of plastic parts (battery tray, sliders, bumpers, the heavy body) and added 200 grams (100 each portal) up front and light body. And moved the battery in front of the servo / behind the front bumper.

The result for me and my terrain is awesome crawler performance and an OK scale look. Depend on your wheels how heavy are they you can add rear portals (if you are using plastic wheels, rear portals is OK. If heavy wheels in the rear stay with plastic portals)

In my opinion the best place to add weight is the front portals. So for you i suggest just add the front brass portals and run the truck. After this add more if you are not happy. It very much depend how and where you drive and if scale or performance is more important.

For best performance over all the lighter the better. But again depends on the terrain. I run in the Mountains and there if your rig is too heavy it digs in the soil and leafs too much. And in snow a heavy truck will not go far.(mountains in the winter are serious business ;)) On pure rock, heavier is OK.

(other performance boost is OD or UD gears for trail. For pure crawl use both) (but expensive, so leave it for the future).

The most important thing is that the actual setup for you and your driving is very subjective. So just run the truck, see what is happening and what you dont like. After that report in the forums for more input

Last edited by Veygr; 02-11-2020 at 03:40 AM. Reason: snow and winter conditions
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Old 02-11-2020, 03:59 AM   #3
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Default Re: Noob brass question

Performance orientated looks. Not the worse. So dont be afraid to try removing unneaded parts

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Old 02-11-2020, 04:04 AM   #4
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Default Re: Noob brass question

I'll try it out this weekend, and have some starting point. good thing is that brass is easily sell-able. Im just not a fan of plastic/brass mix.. not sure why.. probably my OCD
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Old 02-11-2020, 04:42 AM   #5
Hal
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Default Re: Noob brass question

I like Vey.gr's method of weight transference. I run comp rigs and 60/40 is a very good point to start. I have seen rigs at 70/30 and 50/50 that perform very well. 50/50 tends to be noobs and fast movers. To get the weight bias you will need a scale that can hold the weight of your rig. I bought one for 12 bucks that goes to 10 pounds. I put a paint stirrer across the scale so I can get both front or rear wheels on the scale at the same time. Weigh the front, weight the whole rig and devide whole weight by front weight and you have the weight bias. ie 6 lbs front end 10 lbs rig =60 %front 40% rear.
I also use the scale to weigh each corner separately to make sure weight from side to side are same. I do have to say none of my rigs are over 5 lbs, I like skinny girls, even my scaler (unless I put on the hardbody.) Iwould definitely find a place near the front for the battery, I like to move weight around when possible instead of adding weight when possible. If you do want to add weight try to keep it down low. Portal weights are a good place to start. I also don't do weights in the wheels, it is rotating mass that the driveline has to get moving. It is also tough on the axle bearings. Hope this helps good luck

Last edited by Hal; 02-11-2020 at 06:41 PM.
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Old 02-11-2020, 02:40 PM   #6
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Default Re: Noob brass question

I've adeed the fenders today.. and the weight distribution as it is is 55/45 in favor of the front end. I don't think I need anything at the back... I think I have just wasted 50$...But.. I'll sell it sooner or later...I have a spare tire on my roof rack.. I should remove it and see the distribution then... its around center.. so I don't think it makes all that much difference...
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Old 02-11-2020, 06:19 PM   #7
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Default Re: Noob brass question

Brass is a thing you add as you go. See what each piece does for your rig. If you haven't upgraded the servo yet. I have to suggest that before adding too much weight up front. The stock servo is really a joke. My Trx is 8lb 1oz with battery in A low COG tray. 60/40. Up front I have alloy axle housing, aluminum knuckles, 93g each portal weights, 6oz bumper and a full electronics box. In the rear I have samix outter portal covers, aluminum shock towers, truggy cage and scale items. The balance feels perfect! Test and tune is going to be your best friend. The more weight you put up top the easier it's going to tip. You might not think that spare on the roof rack makes a big difference, but it makes a bigger difference then you realize. Hal makes a great point on removing and moving stuff. I removed so much unneeded plastic on mine when I started modding it. Trx has been around awhile and there are allot of great build threads to read through here for ideas and inspiration. Good luck brother! Let us know how it goes! here's a shot of my rig

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Old 02-11-2020, 07:22 PM   #8
Hal
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Default Re: Noob brass question

Animal hippie has a good point about just putting weight on without running the rig with the changes you have already made. I would be careful where you put ANY added weight. The further away from the axle centerline you go, the more it will change how your rig handles in off camber situations. Off camber meaning, hills, side hill, up hill, and down hill. All have a different affect on how that weight will act. The reason we run the weight bias is so when we are going up hill the weight will transfer to the rear axle and help push the rig better. Now consider if we are side hilling that same weight will try to push the truck side ways. If you have good grip, you will roll downhill depending on how steep it is. Going down hill it will put all that weight towards the front and cause you to endo. The tire being much higher up also has a bit more leverage, remember it's further from the axle centerline, so can push even harder in the direction of gravity. I know you are trying to get a nice looking truck, so you like the scale add-ons. If you really like the spare there, so be it, but see what you can do to make it lighter. My Demon has a spare with a very light weight rim and I run it with minimum foam in it to keep it light. There are trade offs to everything
My club runs a lot of Scaler events. Even though I don't run in them I love to attend and watch. We don't give points for "Scale stuff" so most of the rigs that do well are bare bones. Those same rigs are totally different than they are on a Saturday out trail running. The bare bones bodies come off and on go the winch bumpers, spare tires, cab mounted lights, axes, sleeping bags, drivers, pets and you name it. Its fun! It's all what YOU want in your rig, comp rigs are all business, looks come second. My scaler stuff is all about fun with my grandsons. Of course some of the "business " comes out on Grampa`s rig. I can't be getting beat by a 6 year old with a stock ride.
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Old 02-11-2020, 10:37 PM   #9
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Default Re: Noob brass question

lol.. yeah .. I have a kid whose rig is least invested in.. but he's holding his own.. Those hyrax tires and 120mm shock sure help.. lol.
I had the tire on the rear bumper, but the funky chinese people messed up my order and instead of a front bumper, they've sent me a CNC machined rear one.. so the tire had to go higher. I'll remove it if need be, because my hardbody Vaterra never had a spare. I have a longish trail coming up this sunday.. and I'll give it a go....

Thank you everybody for the advice

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