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Ultimate front rear weight dist. for crawling?

MadJack

Red Skull Member
Joined
May 19, 2020
Member Number
166
Messages
5
As the title states...........opinions/ discus...
 
Portal guys seem to be figuring ~55/45 f/r bias. It's a range though....60/40 seems to be in the mix as well. They're playing around with it with water in the tires and even running different ratios of ring/pinion to get the front to drag the rear up an obstacle. I guess at least some of this was theory tested out in the RC rockcrawler world.
 
Sean that make sense only if you only crawl uphills.

Also keep in mind weight in tires don’t help on controlling front or rear suspension from unloading.
 
TrailTamer said:
Sean that make sense only if you only crawl uphills.

Also keep in mind weight in tires don’t help on controlling front or rear suspension from unloading.
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The car is trying a lot harder to rotate around the rear axle and flip backward climbing an obstacle than it is trying to spin around the front decending under brakes or engine braking though. The fancy car guys mitigate the suspension unloading with suck down winches.
 
I've heard 60/40 and the rigs I emulated were using that target.

I'm just under, I think it was 58% when we had mine on the scales. I'm happy with performance. Front engine, non-portal, drag axle.
 
If scale/RC physics apply, the bias is more like 70/30. 30% overdrive on front axle. Lots of unsprung weight on front axle itself. Low CoG, sitting on the bumps, mostly all down travel.
 
mobil1syn said:
jesse haines also has some box that makes the rotation of the front/rear driveshafts opposite of each other to counter the torque lean.
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Probably just a hummer portal gear set in a sealed box.

Sean said:
Portal guys seem to be figuring ~55/45 f/r bias. It's a range though....60/40 seems to be in the mix as well. They're playing around with it with water in the tires and even running different ratios of ring/pinion to get the front to drag the rear up an obstacle. I guess at least some of this was theory tested out in the RC rockcrawler world.
Click to expand...

I don't think there is a perfect number. Too many variables in rigs, drivetrains, packaging, ETC. My rig is 55/45 with water in the front tires and I'm really happy with how it reacts, I'm crawling not competing... Some of the comp guys are running lead shot in the tires as well.
 
I'm 58/42. Every car/driver will be different, but 55-60 front bias is generally where everyone ends up.

Over 60 sucks in the drops. Much below 55 sucks on the climbs.

I have never front-flipped, I've always driven out to save it. I HAVE backflipped a few times, none was due to bias, just crappy driving.
 
Jesse Haines needs to do Q&A's more often on IG. I loved it when he did....

Here is what he said last time....
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It sounds like he does bias to the rear on sprung weight but then uses water to make it front heavy.

I stalked some old posts on pirate and found this. Funny how when he joined he was "mud truck" lol I am sure he has nothing to do with mud now.

Did the tech change in 10 years? idk but what he said back then.

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Geometry and chassis design has changed a shitton since 2014, and we all have learned a ton, including Jessie.

Today's rear engine moon buggies are front biased without water/shot in the front tires. Shot (with water) is used for more "abrupt" weight transfer when you shoot a wall and stop quickly at the top, plus it keeps the weight lower. Water is cheap/easy, most generally end up at half or top of wheel.

Water weight is about 275# with a 42" tire on a 20" wheel, water filled to 12:00 on the valve stem.
 
disregard his 2014 post. The IG comments are 1.5 year old info. much more recent.
 
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