Competition Front end hop when pulling???

[RyanB]

Hey Guys-



Just looking for a little info or advice on my truck.



yesterday I put the 2nd hook on the truck as a demo because on its first run I was getting some bounce from the front end in the first 75 feet and wanted to see if it happened again.



Well, this time it was smooth comming out of the hole but at around 150 feet it started again but I just stayed into it. The track pretty much sucked (Loose Dirt track with hard stuff down about 3-4") but was pretty ruff for everyone.



Im thinking I probably should add another shock or even two per side of the axle to try to cure this. In the truck it was actually a fairly smooth ride as you will see from the video that the actually body isn't bouncing... just the axle.



The suspension is pretty much custom on the truck as I am running a Dodge D60 with a set of 05+ Ford Trailing arms from a F350. I am thinking its the super long trailing arms and only running the one shock because there was an 07 Ford F250 that pulled (it was totally stock) and his axle was doing the exact same thing the whole way down the truck)



Anyway, here is the video YouTube - Orangeville Truck Pull 07 ... what do you think?



RyanB

 

[csevers]

hanging some weight on the front would help, you are probably unloading the front axle(well almost) and then it doesn't have enough pressure to settle it down. If memory serves me right I have seen a lot of fords doing the same thing mostly stock trucks with no weights on the front.



Craig

 

[RyanB]

hanging some weight on the front would help, you are probably unloading the front axle(well almost) and then it doesn't have enough pressure to settle it down. If memory serves me right I have seen a lot of fords doing the same thing mostly stock trucks with no weights on the front.



Craig

Yeah thats the thing though... 60" out I have as much as I possibly can (750lbs) and there is no more weight I can move around (already gutted the interior).



When I weighed the truck there is 5200 lbs on the front and 2800lbs on the rear tires. So I would think I am good weight wise there.



I think its just the shocks but if anyone else has any other opinions let me know. . >RyanB

 

[jwilliams3]

How about pressure up front?

 

[JoshPeters]

Yeah thats the thing though... 60" out I have as much as I possibly can (750lbs) and there is no more weight I can move around (already gutted the interior).



When I weighed the truck there is 5200 lbs on the front and 2800lbs on the rear tires. So I would think I am good weight wise there.



I think its just the shocks but if anyone else has any other opinions let me know. . >RyanB

The problem is, that's what it weighs sitting on a scale. How does the weight transfer when you have the sled in tow?

 

[RyanB]

How about pressure up front?

Air pressure on the fronts were at 26psi at both pulls. Tires are BFG MT's 255/85R16 E-Rated so I figured I could slacken them a bit more than a D-Rated or something else.

 

[JTroiano]

Holy Crap!!! Maybe the control arms are flexing and bouncing back. I would think shocks first (cheaper) and then stronger control arms second. What about having a way to pin the front axle solid to the frame for just the pull? You dont really need any suspension for that distance and the big tractors dont have any front or rear suspension. I'm way out of my league.



Do you drive that monster on the street? What are your EGT's and boost pressure during a pull like that?



Jon T

 

[Turbo Tim 1]

If I am not mistaken the 255/85 BFG MT's are D rated tires not E's

 

[RyanB]

If I am not mistaken the 255/85 BFG MT's are D rated tires not E's

Your right... my mistake... I thought they were the same as the 235's (had it in my head because I just priced a set for the hauler the other day).



About the solid suspension... . from what I have heard thats a no no but would like to hear more on it because it would be a great way to do it for cheap. There is no bounce at all in the rear end and honestly I can hardly feel it in the cab.



RyanB

 

[JTroiano]

To start! I have no experience in pulling. Something is eather flexing or bouncing. After thinking about it some more. Have you ever taken a tire and wheel and bounced it like a basket ball? It can be done. 26psi? I would jack it up higher (35). It would make it less bouncy, also less traction but I think the whole thing is a trial and error thing until you figure what works. Rancho 9000's set on the hardest setting would also maybe help or dual shocks like you said. If those ideas dont work, cut some 4x4 wood blocks to wedge between the frame and axle or bump stops and axle. Make them a little big so you have to lift the body and frame a little so they are wedged in. Nylon rachet straps to hold it all together. I do think this is a bandaid. It may also limit flex to get good traction. The rear end will still flex. I do think some very stiff shocks and tire pressure shold be the ticket. I want to know what fixes it.



Still don't know what boost pressure and EGT's are going on?



Jon T

 

[RyanB]

Thanks for the tips... Anyone else have anything to add to that? Boost and EGT's are known and I want to talk to a few other people familiar with my setup before I say whats going on.



RyanB

 

[Jim Fulmer]

Thanks for the tips... Anyone else have anything to add to that? Boost and EGT's are known and I want to talk to a few other people familiar with my setup before I say whats going on.



RyanB

There both high! Your making allot of power Ryan! I have not input on this deal except you can hear it in the motor when it loads and unloads. In the drag racing world this is a priority, if you have to back out of it you just unloaded the suspension... ... 4 link!



The Rancho 9000's (if you go that route) are a good shock, I run them on my truck and have for years, took the wheel hop out!



On another note, tires are odd when they get loaded! Wes Snow (Crawler) told me my tires look like basketballs on the dyno at 45 psi, so now I run 60-70 psi and just let them shake a little!



Always a pleasure to chat with you Ryan, you mind never stops!



Jim

 

[BigBadDodge]

A basket ball with more air bounces higher then one with less air



I would go down to 20psi go 20psi over rating on rears move as much wieght forward of the front axles as possible and get some shocks that don't bottom or top out, you want the front to float freely.



BBD

 

[TAbbott]

I think a set of 90-10 drag shocks would be the answer. They'd let the front end come up easily for good weight transfer but when it tried to settle back down they'd be stiff as heck, holding the truck up. That's what they used to use on drag cars in the old days and it seemed to work for them --- course their front wheels weren't powered, but would still think the concept is valid... .

 

[crawler]

Here is a pic to show you what around 750 HP does to stiff tires on the dyno.



Jims looked freakier than this. I just don't have a pic of his.



I know this stuf doesn't apply to the truck in this thread. But, I wanted to show what Jim was talking about.



#ad




~Wes~

 

[GOT-Torque]

WOW!!!

 

[Turbo Tim 1]

Crawler, that is an awesome picture

 

[RyanB]

Yeah that is pretty wild looking. I have seen tires on drag cars look like that when viewed in slow motion or frame by frame but never like that on a dyno.



I picked up a set of 90/10 drag shocks today and am going to try to mount them up before the weekend so hopefully they will work!



I will keep you all updated... . RyanB