BC Broncos racer crossed up

[chuck]

mine has stock body mounts so i go off frame to axle measurements. after my 3 year project, taking out a few times and adjusting ride height by adding then removing leafs. mine ended up 1in lower than stock(someone else comparing axle to frame and telling me) with 6-6 1/2in up travel from ride height. when the rear is bottomed, the axle tube is 1/4 maybe less from touching the bare frame rail. original bumstops and plates all gone. to get it this low i put the rear shackle bushing 1/4 in below the bed right at the rear of the body and moved the front mount up several inches. it uses all of a 3.0 16 inchtravel shock.(fortunate to have a friend at king to help tune, which i think is class 3 fail point, suspension really working like it should). one thing that helped a ton with raising the front mounts is i ended up (by luck) 0-1 degree pinion change over 18in unstrapped and less than 1/8 drive shaft plunge. i think plunge affects suspension movement greatly while under accel or deccel. your front obviously cant be as low as mine due to not being able to c notch for the trackbar and draglink at full bump. but still as stated every class 3 eb i have seen has been super tall. i have watched hours of you tube videos and still feel that if you look at what keeps eb(besides breakage) especially from improving speeds is not properly tuned suspension.
i also think the huge disadvantage of unsprung weight can be offset by increasing the weight of the eb. mine weight 5500pounds 40 gallons of fuel but no tools or anything. 2800 is the rear and 2700 in the front. i think all that weight especially in the rear more than makes up for it being a little slower by improving stability and suspension operation.
new front end is in the works, but here is a pic where you can see that keeping low ride height is totally possible.

check out the king(go figure)sponsored buggy at 42 seconds. never seen a slass 3 solid axle truck this smooth or a solid axle move so freely under a vehicle while the vehicle is so smooth. so it can be done.
http://www.youtube.com/watch?v=tBy7afq3fag

Here is a picture of my rear shackle. The rear travel is 15" at the axle. up caused a small dent in the fuel cell that is mounted on top of the frame. The down travel is limited by driveshaft bind. The also has 15" of travel, the up is limited by the oil pan and tie rod contact and the down by driveshaft bind. Because of the longer leafs I have more driveshaft plunge at full droop than at full compression. One extreme to the other the total plunge is about 1". The racer weight is 3740 front is 2140 rear is 1600 that was be for we added the spares, they weigh 95 each, that makes the rear 1795. We have the suspension working well at 90 and going over woops. Cornering is good but could be better. The real problem is the acc. control.
PS your EB is lower, I like it did you lower the body on the frame?

 

[VT_Don]

re: "Maybe someone here may know the fix."

I've never professionally raced a Bronco, but have modest experience with a short wheel base, high HP, RWD car on paved, hill climb courses. As you mentioned, fighting to keep the vehicle pointed straight on acceleration is a handful if using a Detroit locker. Carroll Smith addresses the subject in his book, "Engineer to Win." May want to look into Gold Track or Platinum Track differentials from DPI. My understanding, they are designed exactly to for what you're trying to achieve.

Check out this video of an extreme HP, RWD car rocketing up Pike's Peak on dirt. Note how the car is "driven" thru the corners on dirt as opposed to "drifting." Thus, carrying as much speed as possible thru the turn. Turns are approached with antiscipation to avoid heavy braking. Standing on the brakes loads then unloads the suspension reducing traction when acellerating out of the apex. Far more difficult then it looks. This is absolutely amazing driving talent. I'd find out what he's using for a differential and see if it's available/adaptable for a 9-inch.
http://pca.org:80/Panorama/PanoramaPhotoVideoGallery/PikesPeak2010RaceRun.aspx

 

[bigjhoov]

Needs toe-in in the rear which you can't do with a solid axle.

 

[68ford]

Chuck-im running stock body mounts, its just that low. I'm guessing being low plus full width plus 1000pounds heavier ad to my stability. Also your rear shackle is about 6in higher than mine so imagine how much higher my front must be be keep it that low. Plus I'm running ranger race pack with 3 leafs out. So its 8 leaf pack super soft and my shock does all the work. Different from most leaf set ups with 11 leafs. Ever think about raising the engine an inch or so for clearance? If your high pinion the angle won't matter. Not to come across like mine is the way or anything, but I'm good friends with adam householder and co-drive class 1 penhall car. So I've had a lot of experienced help and people driven in my eb that have told me it "should not work that good for leaf springs". Seriously think you should shoot for it weighing more. Everything heavy always seems to handle and work better.

 

[VT_Don]

re: "Everything heavy always seems to handle and work better."

Please explain how this is possible.

 

[68ford]

That statement was in reference to offroad racing and vehicles used for what me and chuck do. Axles can only be so light. So how do you lighten the unsprung weight? Make the truck heavier. In offroad racing the bigger heavier vehicles are generally the fastest and the heaviest. Search trophy truck on youtube if you not familiar. They are typically the fastest and heaviest weighing about 6000pounds average. Terrible hebst old truck worked good very stable and took big hits with like 14in front travel, most have 24in, and it weighed 7000 pounds. When you hit a bump in a heavy truck the suspension works more and the force is not felt in the truck and doesn't force the truck to move nearly as much.

 

[68ford]

heavy truck geiser truck to my knowedge arearound 6000 pounds. this truck handles amazing and has several 1st place finishes. it wasthe first example i found.
http://www.youtube.com/watch?v=RyAIm50pHAo

http://www.allthingsadventure.com/baja-1000-trophy-truck/

quick write up on trophy truck. whatched a show on tv on the speed channel with several nascar, formula1 and drag race/funny car engineers on there. every one of them instantly agreed that a trophy truck is the highest technologically advanced vehicle in any form of motorsports. obviously what me and chuck are try to make our broncos do is on a much lower level but still. without going to mexico or a southwest offroad race youll never understand the environment. these trucks have to be designed to work in everything you can think of and doing it fast. youll go frombigboulders to silt so soft you cant imagine unless you have tried to go through it(probably one of chucks favorites haha). i have personally wathed RG go through no less than 3 foot deep holes for every bit of a 1000 feet long, while the radar gun said 125mph and at the end he was going 130. imagine trying to put 900hp to the tires while using over 30in of wheel travel and have no torque put into the suspension. there is more to the theoretical measurements off his truck for his 4link than anyone on this site would understand. and i feel that when you addup the small thingsyou really can end up with a vehicle that can potentially work a lot better.

 

[VT_Don]

re: "the bigger heavier vehicles are generally the fastest and the heaviest."

I'm still confused...............

 

[68ford]

i dont know how else to explain it. the best off road riding and handling and fastest trucks are "trophy trucks" and they are the heaviest. all i can say at this point is watch some videos on youtube or read up about them. not to knock where your from, but i think without ever experiencing the terain and what these vehicles do, you guys from that side of the county will never under stand. all statements i have stated are off road related. im sure adding a 1000pounds to a nascar or funny car will not benefit awhole lot hahahaha

 

[NYLES]

re: "the bigger heavier vehicles are generally the fastest and the heaviest."

i'm still confused...............

big blocks!

 

[roundhouse]

Needs toe-in in the rear which you can't do with a solid axle.

I thinik there is a way to do toe in by raising the front mount and lowering the rear mount, or maybe its the otherway around.

Ive seen the writeup for a 2nd gen Firebird, in a mag somewhere, they changed the height of the rear spring mounts to get rid of understeer or something like that.

When the vehicle leans over, the difference in the height of the front v/s rear spring mount causes the axle to shift j forward or back just a little, might not be noticable on dirt though.

 

[bigjhoov]

technically, that's not toe-in, it's rear-steer I believe.

 

[mavereq]

technically, that's not toe-in, it's rear-steer I believe.

kinda what i was thinking.... a 4link with some rearsteer engineered in and swapping the locker out for a posi unit would be my plan. i have no idea what limitations you have on the suspension.

when i was in germany we'd hit the track on drag weekend but they'd still have a small road course set up. the guys running lockers couldn't keep the backends from kicking out and ran slower since they couldn't accelerate as hard from the apex of the turn.

 

[bigjhoov]

Links aren't allowed in Class 3. We're limited to stock-ish suspension. I believe quarter elliptical's have been tried with limited success.

 

[68ford]

Quarter eliptical set ups can be tuned to be far superior to conventional leafs and yield a lot greater travel numbers. Problem is they are very expensive and chances of the rate being right the first time is next to impossible. Properly tuned would be awesome and strong, probably better in every aspect. Just the time and money to tune it. Suck for us small guys, if your not big name guy spending 20grand on shocks they go very little out of their way to help get it right. Like coachbarnes, I believe they set him up with a coilover to go on top of the leaf spring(normal thick pack) and a bypass shock, it didn't work so now he has 2 3in bypass shocks, that is way more shock than eb every needs, ever. He has a lot of adjustibility now, but I feel king should have thought about what they are dealing with. Like I said they don't care about the small guy and you need to know someone to help tune your own truck.

 

[Ratch]

Quarter eliptical set ups can be tuned to be far superior to conventional leafs and yield a lot greater travel numbers. Problem is they are very expensive and chances of the rate being right the first time is next to impossible. Properly tuned would be awesome and strong, probably better in every aspect. Just the time and money to tune it. Suck for us small guys, if your not big name guy spending 20grand on shocks they go very little out of their way to help get it right. Like coachbarnes, I believe they set him up with a coilover to go on top of the leaf spring(normal thick pack) and a bypass shock, it didn't work so now he has 2 3in bypass shocks, that is way more shock than eb every needs, ever. He has a lot of adjustibility now, but I feel king should have thought about what they are dealing with. Like I said they don't care about the small guy and you need to know someone to help tune your own truck.

I have just enough experience with suspension that what 68ford said makes sense. What he said in a previous post about high total weight vs. high un-sprung weight has to do with weight ratio and not total weight numbers. If you watch some videos of trophy trucks making insane jumps with incredibly soft landings it starts to make sense.
Rock crawlers vs. high speed off road racing is like Nascar vs. NHRA, some things just don't translate between the two.

But then I might have had too much to drink tonight, in which case don't mind me. (Away from home on business and it is fat Tuesday after all.)

 

[chuck]

Links aren't allowed in Class 3. We're limited to stock-ish suspension. I believe quarter elliptical's have been tried with limited success.

That is not quite
true. You have to run stock concept suspension ie leaf springs in a bronco but you can also run a quasi 4 link.
I think you guys are on the right trail. I raised the leaf and shackle mounts and may have screwed up the mounting locations, it does not squat.

 

[68ford]

That is not quite
true. You have to run stock concept suspension ie leaf springs in a bronco but you can also run a quasi 4 link.
I think you guys are on the right trail. I raised the leaf and shackle mounts and may have screwed up the mounting locations, it does not squat.

Sound like the rear shackle mount need to be lowered quit a bit and the front raised. As for not squating, its probably the spring rate to an extent. Like I stated I have right about 1000 pounds more on my rear axle and I only have 8 leafs, typical 1/4in thick or whatever and 1/4 wider than stock eb because they are meant for a ranger. ever consider a spring under? Everyone seems to be going that route with really good results. More travel and lower ride height. And less axle wrap for whatever reason.

 

[chuck]

I found my engineering to win book. Looks like my 6" rear shockles are about 2" too tall to equal the stock front to rear shockle mount points. I am thinking broncos don't squat much anyway so a little more squat might be good. I am running f-150 leafs that are 11" longer than stock. I will have to measure but from the front eye to the pin is shorter than the length from the pin to the rear eye. I have no room for the suspension to go up any more but I can move the back down and the front up.
I have been think for a long time to do a quasi 4 link, this might be the right time to do it.

 

[chuck]

My experence with weight is, the first racer we built weighed 6800 lbs. it slowly wallowed through the bumps and bottomed out on every little bump. The next year we were down to 3700 lbs. and the racer handled much better. TT have longer wheel bases ~120" and they have 50"-60" of wheel travel, also they mostly have 2 very long shocks per wheel, EBs are limited to 15"