Make it handle

[BMERDOC]

Rob, That much caster will cure just about any abnormal tendancy. I think your biggest problem would be what I call "trameling", bumpsteers ugly little sister. A wide/low profile (or just wide or low profile tire) has a tendancy to follow defects in the road surface. The wider or lower a tire the greater the chance of this occuring. I think that a greater amount of caster would help in correction but wouldn't help in the initial response of the tire to the defect in the road.
With that much tire and caster, even with power steering, I hope your gym membership is still in effect
Are you concerned about unsprung weight?

[Ackattack]

If someone in the "crowd" was an engineer that was good with FEA (finite element analysis) programs, they could figure out how best to box and strengthen the frames. I'm an engineer, but don't work with FEA.

[robnolimit]

Had a good question today. "would'nt it be best to mount the rear shocks straight up and down?" Well, maybe, not. First thing to remember/or understand, is that most shock companies make one valve set (usually a front valve), so most shocks are valved the same. Example, if you buy Brand-X lowering shocks for your truck, and you get front and rear shocks, they may be different lengths/mounting, but they have the same valving. - This does change when you get into higher quality, more performance shocks. The front of your truck weighs appx 2300 lbs., 1150 per side. Lets say the A-arm has a 2 to 1 ratio, so there is appx 2300 lbs of force to act on the shock. Out back, there is appx 1200 lbs, 600 per side. If the shock is straight up on the axle, it moves at 1-1. It sees 600 lbs force to control. Now factor in unsprung wieght. This should be thought of as a % of total, not just a number. The front unsprung wt. I'll guess to be appx 220 lbs, or 9% of the total front wt. the rear unspung is appx 270lbs, or appx 23%. What does all this mean? The front shock deals with alomst 4x the force as the rear, but it does move at a slower rate due to the leverage effect, but this still tells you that the front shock valving should be stiffer than the rear. Next, apply the unspung wt. %, The rear is almost 2 1/2 times higher, higher unspung % = softer compression. It is a safe bet to say that we in truckland need softer rear valving. - but remember, most shocks are valved the same. So, if you lean the rear shock, you can reduce some of its valving effects. I'll look for a chart to post up. Have a great day.

[67cheby]

nice bit of info, so the more angle on the rear ( to some extent) the more it will help in the valving compensation for the rear shocks ?

[theastronaut]

I had this thought after reading Rob's last post on shock angle. If the angle changes the effective valving, could brackets be made to make the angle easily adjustable? In effect making somewhat of an "adjustable" shock?

Something like this might could work if there's room for it. Just throwing the idea out there.

[robnolimit]

When mounting coil-over shocks measure the degree of angle and use the chart to find your angle correction factor (ACF). Then divide the desired spring rate (DSR) by the angel correction factor (ACF) and the result will be the actual correct spring rate (CSR) that you need.

Angle 10º 15º 20º 25º 30º 35º 40º 45º
ACF .96 .93 .88 .82 .75 .66 .59 .50



Here is a chart of the shock/spring rate corrections

[robnolimit]

Let's throw a new topic into the mix. SAFETY I know, I know, I sound like my dad (a pretty sharp guy) How about we agree that, while there may be more than one 'right way', some stuff is just WRONG, and it's OK to say it. You might even help somebody by doing so. In the past two weeks, our lead tech, Sulivan, has been buried in fixes (take over, or repairs from other shops/installers). Some of those are kinda scary. Here's a short list
1. '56 F-100, volare clip. The clip was installed at the wrong angle. Upper A-arm sloping down in the front 3* (it should be 4* to 5* back) Resulting in negative caster, no antidive, and one squirley ride. lol-400+hp 351C. 24 labor hrs to fix. Should never have been drivin on a public hwy.
2. '58 GMC, camaro clip. Again , wrong angle. At least there are aftermarket chevy parts avail. 18 hrs to modify the clip & lower arms, and $435 for some APC adjustable upper arms.
3. '66 chev P/U, Typical bagged truck. Came in on a flatbed, hit a curb, fence, ... Just basic poor install safety. No clamps on any air or brake lines. An air line split, and as the truck dropped and bounced, it tore off a rear brake hose. Probably 5k in damage for the lack of 20 bucks in clamps, and maybe some new brake lines.
4. This is the sad one, a really nice '68 mustang. All aftermarket suspension, pro-touring style car. On a freeway onramp, on the throttle, the rear suspension came apart. Lots of carnage. The culprit? No one ever tightened the jam nust on the link bars. 5 minutes could have saved this one. One of the ends pulled out of the upper three link bar. The rear axle rotated around, drive shaft pulled out of the trans, ...bad, bad, bad stuff happened. We're still fixing this one, and will be for a while.
Make a pledge to use things like anti-sieze, locktite, a tourque wrench, the instructions, a motor manual, ...... you know, be a professional. - just sayin.

[BMERDOC]

I couldn't agree with you more. I am currently repairing a truck that had $3000.00 worth of damage because they guy installed his emergency spare backwards, then drove on it crushing and bending brake and suspension components. I have to fix things that "mechanics" repaired on a regular basis. Not saying anyone here is incompetent but planning, execution and pre-flight checks are very important.

[Conundrum]

I'd like to add something Rob, take your time, plan it out and think it through, don't get in a hurry and rush it or you may end up with one of those costly mishaps.

[Mechanic77]

I'm with you Rob.....I've been mechanic'n for 10+ years, and it makes me furious to see what some other mechanics call a "repair", it gives all car guys a bad name.

[robnolimit]

Amen, brothers! Poor quality work makes us all look bad, and it hurts our industry. As for a guy who feeds his kids by building cars, our overall image is important to me, and to you guys as well.

[KQQL IT]

Never sieze rules
messy and grows but works o so well
Posted via Mobile Device

[robnolimit]

Another topic shift here. This weekend were going to go and some testing with brake pads. We have two trucks, The 'Bullit and the J.T., and a friends 67 camaro pro-touring car going out. For each vehicle, we have five sets of pads. Two from Wilwood, Hawk, Baer, and a premium OE set. We're going to do 70-0, and roadcoarse laps on each pad and compare.

How about you guys, any experience with pads? any favorites?

[Mike Bradbury]

Maybe I'm missing something but are you saying you are going to test all these different types of pads on the each of the trucks? If the Bullit has one brand of caliper how are another brand of pads going to fit it. I understand if they were a caliper that was close to OEM specs several brands would fit, but I was not aware that a Hawk or Baer made a pad would fit in a Wilwood caliper or vise versa. I will be interested in the results.
I have a Lincoln 9" rear and have been having a heck of a time trying to find anything but regular OEM type pads. I would like to find a pair of premium pads if I could.

[robnolimit]

Originally Posted by Mike Bradbury

Maybe I'm missing something but are you saying you are going to test all these different types of pads on the each of the trucks? If the Bullit has one brand of caliper how are another brand of pads going to fit it. I understand if they were a caliper that was close to OEM specs several brands would fit, but I was not aware that a Hawk or Baer made a pad would fit in a Wilwood caliper or vise versa. I will be interested in the results.
I have a Lincoln 9" rear and have been having a heck of a time trying to find anything but regular OEM type pads. I would like to find a pair of premium pads if I could.

The JT has stock calipers, and rear drums, we have four sets of pads for it, OE, hawk, and two from Wilwood. The 'Bullit has Baer brakes, they use a corvette pad, as does the '67 Camaro. We have muliple sets for each to swap and test. I've never done any testing like this, so, we will be making this up as we go along.

[Spla'nin]

Originally Posted by robnolimit

Another topic shift here. This weekend were going to go and some testing with brake pads. We have two trucks, The 'Bullit and the J.T., and a friends 67 camaro pro-touring car going out. For each vehicle, we have five sets of pads. Two from Wilwood, Hawk, Baer, and a premium OE set. We're going to do 70-0, and roadcoarse laps on each pad and compare.

How about you guys, any experience with pads? any favorites?

Good topic Rob...Including brake tire warm up or cold turkey? How important are the turns / braking in the very first part of the course that contribute to "putting the heat" into braking tire system to get it to the level to make a good time...? The driver skill / adaptability factor is huge when the conditions change dramaticly...much respect pick up dude
I suppose a pyrometer and air temp recordings may be of interest also...

[robnolimit]

Originally Posted by Spla'nin

Good topic Rob...Including brake tire warm up or cold turkey? How important are the turns / braking in the very first part of the course that contribute to "putting the heat" into braking tire system to get it to the level to make a good time...? The driver skill / adaptability factor is huge when the conditions change dramaticly...much respect pick up dude
I suppose a pyrometer and air temp recordings may be of interest also...

We got some good info from the pad manufactures, yes on the heat gun, didn't think to check air temp, - good idea. We will have three drivers, all with 'some' experience. should be fun

[robnolimit]

Originally Posted by Spla'nin

Good topic Rob...Including brake tire warm up or cold turkey? How important are the turns / braking in the very first part of the course that contribute to "putting the heat" into braking tire system to get it to the level to make a good time...? The driver skill / adaptability factor is huge when the conditions change dramaticly...much respect pick up dude
I suppose a pyrometer and air temp recordings may be of interest also...

We got some good info from the pad manufactures, yes on the heat gun, didn't think to check air temp, - good idea. We will have three drivers, all with 'some' experience. should be fun

[gringoloco]

Will these be 'streetable' pads, or full-on race compounds? Will you record noise and dusting? This should be cool

[robnolimit]

Originally Posted by gringoloco

Will these be 'streetable' pads, or full-on race compounds? Will you record noise and dusting? This should be cool

Hmm, noise? didn't consider that one. As far as dusting, I don't know that we'll get enough time on each pad. - If we do see dusting, then it would be extreme.

[Ackattack]

I used some hawk pads on my trans am when I was autocrossing it and had good results (I don't remember which line of pads I was using, it was ~2000-2001) So when it came time to get pads for my 68 I went with Hawk HPS (IIRC).

Basically my brakes suck. My setup includes new drilled vented rotors on the front with dual piston aluminum calipers from POL and the Hawk pads. The Rear are LT1 camaro PBR sinlgle piston calipers. New brake lines also. They have sucked from day one. In trying to correct the problem I have gotten a new power brake booster, 72 corvette manual MC, manual brake proportiing valve (originally I was using a disk-disk proportionting valve from CPP). I even took the calipers off and sanded on the rotors and pads to remove any glazing.

The trucks stops OK, probably not quite as good as a stock front disk setup. The poor braking is what really kept me from attempting the autocross at the KC goodguys show. My next step is to change the pads, as it seems like they just aren't gripping. I'm thinking of using some EBC pads (not sure which ones at this time)

[robnolimit]

I have twi thoughts here. 1. rear GM calipers MUST have the e-brake connected and used from time to time to keep the rear calipers adjusted. 2. I have used a few brands of aftermarket calipers for the stock brake. "drop-in" upgrades. NON have ever performed better than stock. Try swapping in some used OE calipers for a try.

Originally Posted by Ackattack

I used some hawk pads on my trans am when I was autocrossing it and had good results (I don't remember which line of pads I was using, it was ~2000-2001) So when it came time to get pads for my 68 I went with Hawk HPS (IIRC).

Basically my brakes suck. My setup includes new drilled vented rotors on the front with dual piston aluminum calipers from POL and the Hawk pads. The Rear are LT1 camaro PBR sinlgle piston calipers. New brake lines also. They have sucked from day one. In trying to correct the problem I have gotten a new power brake booster, 72 corvette manual MC, manual brake proportiing valve (originally I was using a disk-disk proportionting valve from CPP). I even took the calipers off and sanded on the rotors and pads to remove any glazing.

The trucks stops OK, probably not quite as good as a stock front disk setup. The poor braking is what really kept me from attempting the autocross at the KC goodguys show. My next step is to change the pads, as it seems like they just aren't gripping. I'm thinking of using some EBC pads (not sure which ones at this time)

[BMERDOC]

On JT's rear drums have you considered crossdrilled drums and "skeleton" brakes? I would love to see either a stock backing plate water jetted to reduce weight or a complete skeleton backing plate! These drums are sold by Danchuk for 55-57 Chevys. The skeleton brake were fabbed up by Hollywood Hot Rods for one of their projects. They were used on dirt track cars, I think.

[theastronaut]

Originally Posted by BMERDOC

On JT's rear drums have you considered crossdrilled drums and "skeleton" brakes? I would love to see either a stock backing plate water jetted to reduce weight or a complete skeleton backing plate! These drums are sold by Danchuk for 55-57 Chevys. The skeleton brake were fabbed up by Hollywood Hot Rods for one of their projects. They were used on dirt track cars, I think.

Those may not be a good idea on a car that sees street use in the rain. That design would allow more water in, and wet drums don't stop well! Would work on a track only car though.

[BMERDOC]

I would argue that it would do the complete opposite. Stock drums/backing plates retain water which they cannot shed, drilled/open drums will instantneously shed water through centrifugal force and an vented concept. It would also shed heat a lot faster, not to mention a slight drop in unsprung weight.