Make it handle

[gringoloco]

Ok, what you're saying makes sense--especially considering my recent experience in swapping from 'bags to drop coils on the rear of my truck--definitely a stiffer ride. I may try to buy back some of the articulation by swapping to rubber bushings. Can you expand a little on the advantages of the "soft spring, big bar" theory? Also, how will this affect load capacity? Does this hold true for the front, as well?

Thanks for the info!

[robnolimit]

OK, lets think about spring rates. First, we need to imagine our basic truck, and how we want it to sit. I'll say that we have a trailing arm C10 shorty, dropped 4", no notch. There is now 4" from the axle housing (top) to the frame rail (bottom). So, from Ride Height (RH) we have 4" of compression travel available. - then it bottoms out. I'll also say that our truck weighs in at 3850 lbs. with 1400 lbs on the rear (JT's specs.). Looking at the rear only, thats 700 lbs per side. If you had a 400 lb/in spring, it would take 1600 lbs per side to bottom the truck out, 3200 lbs total. (appx 1600 lbs and a good bump would do it) But this will still haul a 1/2 ton load. Now if we put 200 lb springs on it, and get the same ride height it would reasonably only carry 800 lbs without bottoming out to bad. Remember that appx 1/2 of the driver/passanger weight will go to the back. So now your down to about 600 lbs load cap. - max, with 200 lb/in springs.

[robnolimit]

There are a lot of concepts out there about handling. Here is one thing i see a lot at Auto-x and track events. The problem is that the car (truck) is loose through the corner. The solution is to disconnect the rear sway bar. ?what? I see this all the time. OK, I get it the first time, but this is backwards. If you need more rear bite, lower the roll center (panhard mounting points) and/or softer rear springs. Now I'll ne honest, I n
know just enough to get into real trouble. When it comes to other suspension concepts, I try to understand why, and then look at the outcome. Porsche does very well with a 'stiff spring' layout, as do most exotics. - but their CG is VERY low. Mercedes and BMW have great handling and smooth riding cars with the 'soft spring' approach. -higher CG. There is no "one size fits all" answer. Trucks and Hot Rods (my arena) all suffer from a high CG. Using a soft spring and big bar set up makes sense to me. The weight will force the truck to lean over, so let it compress the outside corners of the suspension with soft springs, then use a large swaybar to transfer the suspension load to the inside corners.

[69gmcc10]

So, why do u reccamend 3/4 ton front springs for these trucks?... your logic would say that 1/2 ton springs would be the way to go. Is it because the fronts of these trucks are so heavy and gm undersprung the 1/2 ton truck to ride soft? I am honestly just trying to understand not be confrontational.

thanks

[robnolimit]

Originally Posted by 69gmcc10

So, why do u reccamend 3/4 ton front springs for these trucks?... your logic would say that 1/2 ton springs would be the way to go. Is it because the fronts of these trucks are so heavy and gm undersprung the 1/2 ton truck to ride soft? I am honestly just trying to understand not be confrontational.

thanks

Good catch! Your right on both counts. Yes, with the stock A-arms and suspension points, what we would think of as 'soft' is still a bit firmer that the OE 1/2 ton. The cut 3/4 ton spring nets out at about 1000 lb/in. This sounds like a lot, but the ratio on the lower arm is close to 30%, so the 1000 lb spring nets appx 300lb/in load rate at the center of the tire (hub face of the rotor)

[69gmcc10]

So, even with the cut 3/4 ton spring in the front and stock 1/2 ton springs in the rear the front has less than half the rate than the rear does? and there is nothing in the bed?

[robnolimit]

SHOCK MYTH Got your thinking caps on? Company A advertises thier new bad ass double throw down billit shock. It's the latest and greatest ever. Years of testing and technology have gone into them. - Now, this could be 1970, 1999, or today, it's been going on for a long time. So lets think about how good these are for YOUR TRUCK. They sell these new Brand-X shocks by LENGTH, and MOUNT TYPE. So, you need a 4.5" stroke shock in front, with a 10" spring, and a 6" stroke rear shock with a 12" spring. Now here's the really cool part, they have it all in stock!!!! This is so cool. They tell you you need a 500 lb front spring and a 250 lb rear spring. Good to go. Isn't this great? This is all set up just for your truck! ----- or is it??? Did you notice any information telling you a different part number for a front or rear shock? Well, no but the length does that right? Honestly, I don't know. But I do Notice Brand-X only seporates shocks by length. Thinking cap time. If the front of your truck weighs 2400 lbs, (1200 per side) and has a load rate of 30%, the shock would see almost 4000 lbs of force per inch of shock travel. Out back, the rear weighs in at 1400 lbs (700 per side) with the shock layed over at 20% you net a load calc around 88%, so the shock would see about 795 lbs of force per inch of travel. OK, once again, 4000 lbs force up front, 800 lbs force in the back. Wow, thats 500% difference! Here's the question of the day - How could you expect the same shock valve to work correctly in both places?

[jlsanborn]

Is that why you recommended brand X-front and brand Y-rear for my truck today? I didn't see brand X on your store page? You also recommended a "stock height" shock for my lowered front. What's the reasoning there? I sure appreciate your help and your bad a$$ parts! My C10 is going to be sweet because of your hard work!

[ferk_3131]

I am currently running the rear springs from a 68 2 door chevelle on my 69 c10 long fleetside. The rearend is about an inch and a half from the factory bump stops,no notch. It made a huge difference in the ride but a bit to soft. With a couple hundred pounds in the bed the bumpstops are just touching. A buddy is going to lend me some with different rates from his imca modified to try.
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[robnolimit]

We currently have a set of chevelle wagon rear springs in the JT. The drop is about 4" from stock springs. We haven't had it on the track yet, but the ride may be edging toward the soft side. IMCA mod springs may be a good idea.

[jimmydean]

Originally Posted by robnolimit

SHOCK MYTH Got your thinking caps on? Company A advertises thier new bad ass double throw down billit shock. It's the latest and greatest ever. Years of testing and technology have gone into them. - Now, this could be 1970, 1999, or today, it's been going on for a long time. So lets think about how good these are for YOUR TRUCK. They sell these new Brand-X shocks by LENGTH, and MOUNT TYPE. So, you need a 4.5" stroke shock in front, with a 10" spring, and a 6" stroke rear shock with a 12" spring. Now here's the really cool part, they have it all in stock!!!! This is so cool. They tell you you need a 500 lb front spring and a 250 lb rear spring. Good to go. Isn't this great? This is all set up just for your truck! ----- or is it??? Did you notice any information telling you a different part number for a front or rear shock? Well, no but the length does that right? Honestly, I don't know. But I do Notice Brand-X only seporates shocks by length. Thinking cap time. If the front of your truck weighs 2400 lbs, (1200 per side) and has a load rate of 30%, the shock would see almost 4000 lbs of force per inch of shock travel. Out back, the rear weighs in at 1400 lbs (700 per side) with the shock layed over at 20% you net a load calc around 88%, so the shock would see about 795 lbs of force per inch of travel. OK, once again, 4000 lbs force up front, 800 lbs force in the back. Wow, thats 500% difference! Here's the question of the day - How could you expect the same shock valve to work correctly in both places?

This is such a good point, Rob. One of the big talks I had with RideTech when I was looking at the Shockwave was the valving based on my application vs. the shockwave that "fits my mounting location". At least from what I gathered the Shockwave Selects are valved soft/hard based on preference and application.

When I tuned my motorcycle suspension, it was a combination of valves and springs based on bike weight, rider weight and overall performance objectives.

[robnolimit]

Right you are sir. I'd have to give RideTech a nod to the positive on this one. RideTech has used a few different shock manufacterers in the past, and now all of their shocks (billit/adjustable) and shockwaves are built by Fox. In the begining, they spent a LOT of time and energy testing and tuning. I have had more than a few dozen shocks from them here. (test shocks have a very WIDE adjustment range, but not to accurate) We would tune them in to our liking, pull them off, and send them back. Each round of testing gets you closer. A few years ago those Indiana boys were out here and we all went up to Infinion Raceway with the Fox engineers, and buy the end of the day, nobody wanted to drive any more laps. - again. ever. we were beat. But thats how you get it right. BTW, motorcycle guys in the know tend to be a bit more 'shock smarter' than the rest of us.

[robnolimit]

I'm Just Trying to Help When we go out to the track, it's in an effect to go faster. We want everyone to go faster. So, we're wiling to help. A lot of people will ask us to look at their cars and offer some advice. I always ask them about the alignment specs. Usualy the Toe is slightly 'in'. "Toe it out" I tell them. They are very hesitant to make a change. Last Tuesday night was no different. "Well, I don't know if I should..." is what we hear back. So here is my new reason for this.

"Stand with you toes pointed in" I said, and he did. "Notice how it makes your knees point in?" - "U Huh" . "Notice how your balls are uncomfortable?" - "ha ha ha , ya" "There ya go" I said. "Now, point you toes out" he did "So, are your balls more comfortable?" - "ha ha ha , ya" Then I added "OK. So there is the Toe-Out lesson. If your balls are happy, you will feel better and go faster!" Hey, it got the point across.

This weekend is the Run To The Coast in El Toro, Ca. I'll be there with the HellBoy. I'll get some picts and video for you guys. Have a great weekend.

[69gmcc10]

I love analogies! This one is funny, gets you involved, works and gets the point across.

[jimmydean]

Originally Posted by robnolimit

BTW, motorcycle guys in the know tend to be a bit more 'shock smarter' than the rest of us.

390lbs and only 2 wheels makes tuning a great deal easier.

[INSIDIOUS '86]

So rob do you have a formula for for shocks? Such as finding our leverage ratio spring rate and such? I know you have shock working angles covered but if we were to call x or y company and give them specs to match a shock I'm sure a lot of us will start doing so and soon we will all be able to zero in on a group that most wil like

Also pinion angles. They have an effect on our handling?
Posted via Mobile Device

[duallyjams]

[quote=robnolimit;5630790]I'm Just Trying to Help When we go out to the track, it's in an effect to go faster. We want everyone to go faster. So, we're wiling to help. A lot of people will ask us to look at their cars and offer some advice. I always ask them about the alignment specs. Usualy the Toe is slightly 'in'. "Toe it out" I tell them. They are very hesitant to make a change. Last Tuesday night was no different. "Well, I don't know if I should..." is what we hear back. So here is my new reason for this.

"Stand with you toes pointed in" I said, and he did. "Notice how it makes your knees point in?" - "U Huh" . "Notice how your balls are uncomfortable?" - "ha ha ha , ya" "There ya go" I said. "Now, point you toes out" he did "So, are your balls more comfortable?" - "ha ha ha , ya" Then I added "OK. So there is the Toe-Out lesson. If your balls are happy, you will feel better and go faster!" Hey, it got the point across.


so simple a cave man can understand it LOL

[calvin78612]

Rob,i have a 67,disc-drum,booster and prop valve fromm CPP.The prop valve is leaking from the brake sensor fitting(plastic)since i am going to change the prop valve would i benifit from going w/a adjustable prop valve and a check valve in the rear line?Thanks,Calvin.P.S. my vaccum to the booster is good and i belive it is 1 " bore front and rear.

[calvin78612]

Ttt

[jimmydean]

Rob, I had a question about weight distribution front/rear.

Obviously a major issue with a truck as a performance platform is the lack of weight in the back on average. Without the idea of a bed, it it ideal for a rear wheel drive vehicle to be close to 50/50?

Or is there an advantage to having more in the back, say 47/53 for putting power down?

[jimmydean]

Originally Posted by jimmydean

Rob, I had a question about weight distribution front/rear.

Obviously a major issue with a truck as a performance platform is the lack of weight in the back on average. Without the idea of a bed, it it ideal for a rear wheel drive vehicle to be close to 50/50?

Or is there an advantage to having more in the back, say 47/53 for putting power down?

<edit> My Corvette in stock form is 53/47 @3200lbs, but I hope with the swap of an LS3 I will be more like 45/55 @2900lbs and I don't want that to be bad. The LS3 is roughly 300lbs lighter with accessories (and 130hp more) and sits closer to the center than the LT1.

[robnolimit]

OK. Using my handy-dandy Weight-Pro tuning guide, I came up with this. 3200 lb with 53/47 gives you 1696 lbs ft. and 1504 lbs rr. If, the engine swap nets a 300 lb saveings, givin the vette setback, you will net -247 ft. and -53 rr. New weights would be 1449 lbs ft. and 1451 lbs rr. For a near perfect 50/50. And a really light car to boot. I would say that this is closing in on the best balance. Perhaps 49/51 would be optimal, but once you start taking more weight off of the front, your gains are offset by losses. Steering out of a corner, on the throttle would start to be iffy, and a 'push' will develope. Stay targeted at 50/50 and use springs and shocks to make it perfect from there.

[jimmydean]

Thanks a lot, Rob.

My Vette is one of the few with the FX3 system (Selective Ride Control) and I am having the shocks revalved by Bilstein when I get the actuators upgraded to metal moving parts. The downside of having a '94 with FX3 is it also came with slightly softer springs to make the soft setting slightly softer. I might be upgrading to the firmer spring set once I give it a go.

Keeping the Vette (I bought it to cut up for the truck, now I can't do it) has put a dent in the plans for the truck. But the idea of a sub 3000# car sitting on 430hp with the wheel base of the C4 makes me crazy.

I watched C4's run better times than the C5 or C6 at the Corvette Rally autocross and was told it was the wheel base.

<edit> And the fact that the Corvette total project with NEW crate LS3 and full suspension would still be under $12k total price including the car...

Consider it a C4 Z06.

[robnolimit]

http://youtu.be/pVDd6aHYC5k

Enjoy. Watch the tire shot, you can see the push (driver induced, I went in too fast) at the far end on the 180* left. Otherwise, pretty good. If you watch close, you may see the door gap shift, I think this is the latch? Anyway, it was a fun day for sure.

[robnolimit]

Jimmy, years ago I ended up with a '84 C4, the original car had the cross-fire injection (bad) and the 4+3 slappy auto. It was a bad car (bad, as in not good) Most of it's technology didn't work. After much frustration, I gutted the car, Put in a tuned port 383, a 5 speed from a camaro, fabbed an aluminum dash with autometer guages (none of the digital worked ) Two Cerullo buckets, (again, the 28 way adjustable seats were crap) Along with gutting the dash, all of the climate control a/c came out, I put in a Vintage Air Mini unit. Weight dropped to 3100 lbs, and it was re-born as the killer of Z-06's It was a fun car street or track, but they do rattle alot