Mastersbilt

[7uptruckracer]

Masterbilt Smack car converted to GenXO spindles, and MBH front bolt ons (Not a concern) My issue. Need to get the LF into the track more without using RR spring. Tire isn't off the ground. Running a 400 LF no tether yet. running 275 on COT bump 3" tall with 3" gap at rideheight should add about 150 at 1" engagement. 225 RR and 175 LR Car is in neutral holes 7 hole rear for intermediate. 21" jbar at 8.5 and 3 clicks up on pinion I believe. 53.5 Rear 55 left 80 bite. Limited motor, engine is 1" up and too right. I don't want to lenghten RS bars because the smack already drives a little yawed, but I need a little on entry and that LF attitude. Suggestions? Have a decent amount of rebound in the front already because the track is a little rough. Have 325 6th coil

[TheJet-09]

Looking at the picture, I wish I could get my Smackdown to have the same attitude (I'm struggling with the LF up/wheelie syndrome). For conversation sake, I'm surprised you get away with a 400 on the LF. I'm at 475 and am most likely going to stiffen it. Is your "275 on COT bump" your RF? I'll admit you lost me there, but I'm not up to speed on bumpstop stuff. How much drop do you have on the LR? Did you also mean a 325 "5th" coil? If so, how far out? And have you ever measured the angle (in at the top) of your RR spring? More so out of curiosity on the above...

[Kromulous]

Stiffer LR spring would help.

Cut the bump stop travel down, maybe 1/4".

That or raise the RR lower bar one.

[billetbirdcage]

Masterbilt Smack car converted to GenXO spindles, and MBH front bolt ons (Not a concern) My issue. Need to get the LF into the track more without using RR spring. Tire isn't off the ground. Running a 400 LF no tether yet. running 275 on COT bump 3" tall with 3" gap at rideheight should add about 150 at 1" engagement. 225 RR and 175 LR Car is in neutral holes 7 hole rear for intermediate. 21" jbar at 8.5 and 3 clicks up on pinion I believe. 53.5 Rear 55 left 80 bite. Limited motor, engine is 1" up and too right. I don't want to lenghten RS bars because the smack already drives a little yawed, but I need a little on entry and that LF attitude. Suggestions? Have a decent amount of rebound in the front already because the track is a little rough. Have 325 6th coil

Something don't add up here: You sure your numbers are correct especially on the RF?

1. You have 6" of exposed shaft at ride hieght? (3" tall BS and 3" of gap to BS = 6" of shaft)
2. Assuming 1 is actually true: with that spring/bump set up and gap, your only getting 1250# on RF?

[7uptruckracer]

I can check the bumpstop height again but I have 3" of gap from the top of the bump to the bottom of the shock body. Pretty sure I'm correct it's a three run (not counting the base) cot 45 gram medium bumpstop.


Something don't add up here: You sure your numbers are correct especially on the RF?

1. You have 6" of exposed shaft at ride hieght? (3" tall BS and 3" of gap to BS = 6" of shaft)
2. Assuming 1 is actually true: with that spring/bump set up and gap, your only getting 1250# on RF?

[7uptruckracer]

Cars shock mounts have been changed its not Smackdown stuff that's why I didn't get too in depth there just wanted to provide the other details. That Cot bump is coming off for a bump spring stack 800/500 stack that I have to figure out what load I need and engagement height but that's besides the point. Is their any way to help my LF attitude that isn't RR spring I can't afford a tighter entry. I'm thinking more LF rebound and less compression. I don't want to add right upper bar and LR thrust angle will make it worse. Is my RF BUMP not potentially having me able to use fill travel helping keep my LF up? I also have a steel limited motor wet sump 1" up and all the way right. Cars good just think I'm missing something.

[7uptruckracer]

And sorry 325 5th I believe 35 out I'll Confirm on that too when I get to the shop I've thought about moving that forward maybe that would give me less rear axle separation as long as it doesn't cause more front lift?

[TheJet-09]

I'm possibly getting in over my head, but I wonder where your front roll center is...having changed the front end geometry to the Gen-X stuff. If I understand correctly (and I quite possibly don't) a higher front roll center can lift the LF. I've moved my front end mounting points so I guess I'll find out the hard way soon enough.

[7uptruckracer]

I've mapped it all out I know where it is and what my camber curves caster curves all that are after the changes we decided to make


I'm possibly getting in over my head, but I wonder where your front roll center is...having changed the front end geometry to the Gen-X stuff. If I understand correctly (and I quite possibly don't) a higher front roll center can lift the LF. I've moved my front end mounting points so I guess I'll find out the hard way soon enough.

[7uptruckracer]

Ahhh I think I see where you are going here billet. You think I'm under loading the RF and it's not planting it and helping turn the front end? So if it is engaging to late I could shim my stack up, but couldn't I also change how quick it engages at its current height by softening the spring to say a 250 and just have it get to the bump quicker? That's what we do on asphalt just trying to think many ideas through

[billetbirdcage]

Ahhh I think I see where you are going here billet. You think I'm under loading the RF and it's not planting it and helping turn the front end? So if it is engaging to late I could shim my stack up, but couldn't I also change how quick it engages at its current height by softening the spring to say a 250 and just have it get to the bump quicker? That's what we do on asphalt just trying to think many ideas through

1st: Before we get to far: Do you know for sure you're basically getting 4" of total travel? Meaning do you have an external travel indicator to know the actual travel thus the amount of load on BS. I have a feeling you either don't have an indicator and it's traveling way more then you think or the driver is fairly aggressive and drives the car in on the RR and is more of a crooked driver over an extremely straight driver thus not getting a higher load on RF (this isn't bad/wrong, just happens with some driving styles).

2nd: Changing the spring and changing the shim stack (if using a BS correctly - IMO) is completely different and not even close to the same ballpark as far as an adjustment and where and when it effects the car.

Trying to help but somethings related here, that I'm not going to post on a forum.

[RCJ]

I'm running almost the same set up as you.Forget about the r/r spring it didn't work.If we get our ballast to high the car will rock over to much.The r/r bars are where we are seeing some results.We are going to try moving some weight a round also.

[7uptruckracer]

Yes we use external indicator. Even if I go to 4.5 total and engage at 3" I load 1587.5 but I dunno if any of this will effect my LF attitude I don't plan on keeping this COT bump very much longer regardless, either going to go back to a 350 or a bump spring stack. I don't like how the COT can spike once it gets much past 1" Just didn't want to hit him with too much at once


1st: Before we get to far: Do you know for sure you're basically getting 4" of total travel? Meaning do you have an external travel indicator to know the actual travel thus the amount of load on BS. I have a feeling you either don't have an indicator and it's traveling way more then you think or the driver is fairly aggressive and drives the car in on the RR and is more of a crooked driver over an extremely straight driver thus not getting a higher load on RF (this isn't bad/wrong, just happens with some driving styles).

2nd: Changing the spring and changing the shim stack (if using a BS correctly - IMO) is completely different and not even close to the same ballpark as far as an adjustment and where and when it effects the car.

Trying to help but somethings related here, that I'm not going to post on a forum.

[fastford]

I started on the bump stop , once I learned the effects of the BS, both good and bad, I moved on to the two stage spring set up, much better on a rougher track. I never went that stiff though, usually floated between a 600/500 and 500/500,

[7uptruckracer]

I started on the bump stop , once I learned the effects of the BS, both good and bad, I moved on to the two stage spring set up, much better on a rougher track. I never went that stiff though, usually floated between a 600/500 and 500/500,

Well the bump spring stack is a 500-800 but it's not a lockout it's a 308 and 2.5" tall their are some guys there running dual stages however

[billetbirdcage]

Ahhh I think I see where you are going here billet. You think I'm under loading the RF and it's not planting it and helping turn the front end?

Yes, that is where I was going somewhat or least bringing it to your attention.


I dunno if any of this will effect my LF attitude

Just to be clear I wasn't meaning your LF issue was with the RF, I was just pointing out that your numbers where odd. Not that it's right or wrong, just different then the most typical numbers you see these days.

RCJ is correct, that the RR spring while may help slightly and/or on certain area's of the track it isn't really much help in fixing or eliminating much of the LF issue your worried about. You need to look in different places.

[7uptruckracer]

Thanks guys I'm going through the whole car this was a test night so I'm confident we have something to build on. I have a lot to check going to look at weight height, shock settings and right side bars I just don't want to get the car too yawed or tighten entry I could always add right lower bar and then shorten the right side back up so I add slight thrust angle but don't add more rear steer? Or even do the same with the upper and run higher bite. We will see I'll post what I went with



Yes, that is where I was going somewhat or least bringing it to your attention.



Just to be clear I wasn't meaning your LF issue was with the RF, I was just pointing out that your numbers where odd. Not that it's right or wrong, just different then the most typical numbers you see these days.

RCJ is correct, that the RR spring while may help slightly and/or on certain area's of the track it isn't really much help in fixing or eliminating much of the LF issue your worried about. You need to look in different places.

[TheJet-09]

Yep, definitely over my head. I tapped out around comment #10. Good luck though! Some intriguing stuff.

[Matt49]

Thanks guys I'm going through the whole car this was a test night so I'm confident we have something to build on. I have a lot to check going to look at weight height, shock settings and right side bars I just don't want to get the car too yawed or tighten entry I could always add right lower bar and then shorten the right side back up so I add slight thrust angle but don't add more rear steer? Or even do the same with the upper and run higher bite. We will see I'll post what I went with

Moving the right lower bar up on the frame usually has no noticeable effect on exit. But it will noticeably free the car on entry.
I think your idea of going up with the right upper bar and increasing bite will get you the result you're looking for. But again this might free entry a little. You might considering moving the right upper bar up and then shortening both right sides to keep it from over-rotating on the gas. Let us know what you find works for you but as was said before, a lot depends on how your driver gets the car into the corner.

[7uptruckracer]

Yeah I really think what you mentioned might work the last thing I want is a yawed out car. I would stand a little free on entry as it was a little tight. I added a rubber to the 225 and it made the car way to tight getting in. Thanks guy I will let you know!