Thread: Narrowed C4 IRS....camber questions

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Guys, I think for the most part I have this thing whipped. I narrowed the batwing 10" overall and will beef it up with 1/4" 6061 plating, tig welded to the outer portions covering the inner webbing. Narrowed each side 3". Installed the VPB lower camber links and Denny's half shafts. Have an idea for mounting the QA1's. Now for the questions.

Suspension travel: without notching the frame, the first thing to touch is the toe links, with 2 3/4" of travel up (compression) from rest. Should I alow more. I have a feeling I should have allowed more stroke, the trouble is, I was worried about ripping my fenders off so I went with the shortest QA1 with 4" of stroke....giving me about 2" of up travel (comression). Any thoughts?


QA1 mounting: I'm told, not to mount the QA1's off the factory shock mount, which makes sense to me. I have seen people make a sort of plate mount using the two bolts that support the dog bones (trailing arms). The trouble is, I really cant use the top bolt because it nearly touches the frame when the suspension is fully compressed. Its like a 1/16" away from frame. I could notch the outside of the frame slightly but I was wondering if it would work using the lower dog bone bolt and the factory shock mount instead, and just leave the upper bolt alone. Anyone mounted thier coil-overs this way?


Camber change: This is strictly an eyeball way of checking camber. Used a inclinometer. My camber tool is on its way. With the face of the rotor at 0 degrees at rest. On full compression of the suspension, 2 3/4" upward (compressed) motion, I lose 1 degree of camber and lose the same 1 degree when moving down 2 3/4". Total of 5 1/2 " of overall suspension travel. Is this acceptable? Any thoughts. New poly busings throughout already installed. I also noticed the forward bracket for the dog-bones flex a little. Not much but they do flex some.

Any thoughts would be appreciated.

Thanks,
Dave

Dave

I haven't been able to find the drawings, but I got them from Brett at Everett-Morrison which are now in Texas---they advertise on CLUBCOBRA, sister site to CLUBHOTROD

I'll keep looking tho as we are moving STUFF out off our building in Elburn as it has been sold and closing is in a couple of weeks

Jerry

Originally Posted by jerry clayton

Dave

I haven't been able to find the drawings, but I got them from Brett at Everett-Morrison which are now in Texas---they advertise on CLUBCOBRA, sister site to CLUBHOTROD

I'll keep looking tho as we are moving STUFF out off our building in Elburn as it has been sold and closing is in a couple of weeks

Jerry

Thanks Jerry. I think I have it covered now. Thinking about getting the Chassis Engineering book by Herb Adams. Does anyone know if there is enough information about the IRS. There is a section in there but I cant preview that section.....for obvious reasons....then no-one would buy it. I'll probably get it anyway. Looks like good information about camber angles etc.

At this time I have found a few people that have suspended the coil-overs off of the combination of the lower dog-bone bolt and lower shock mount and had good results. That will free up my top bolt and give me enough clearance from the side of the frame. I am being told that a 1 degree change in camber just isnt enough.....still trying to find what is optimal for the street.

Thanks,
David

remember that there isn't any camber change in an solid axle!!!

What is your camber setting at ride height??? Doesn't seem that 2 degrees of camber change in 5" of travel would be too much.... The suspension will only go to full deflection when you hit a bump or really hammer it into a turn. Will you be running a rear sway bar? With a rear bar, the camber change would be even less. Under normal driving, it would seem the change would be less then 1 degree....

I which I could be more specific, but without being there to see your suspension work, it's kind of tough. Jerry is probably a whole lot more current on a Vette IRS then I am...

We used to play with rear camber on circle burners, used the same method as the NASCAR guys do. Never really did see any big results, either positive or negative but we were running on dirt, street use and paved tracks require a lot "tighter" specs on suspension then a dirt car....

Oh yeah, when you do all your suspension measurements, make sure you have the car "loaded" properly with the correct total weight and front to rear weight... Heck, bring it over and we'll put it on the scales, too, and have some real fun!!!!!!!

Originally Posted by jerry clayton

remember that there isn't any camber change in an solid axle!!!

I would think there would be some change? Puzzled. I am installing a C4 IRS though. You guys are the greatest...both you and Dave. I appreciate all of the help.

Dave

Originally Posted by Dave Severson

What is your camber setting at ride height??? Doesn't seem that 2 degrees of camber change in 5" of travel would be too much.... The suspension will only go to full deflection when you hit a bump or really hammer it into a turn. Will you be running a rear sway bar? With a rear bar, the camber change would be even less. Under normal driving, it would seem the change would be less then 1 degree....

I which I could be more specific, but without being there to see your suspension work, it's kind of tough. Jerry is probably a whole lot more current on a Vette IRS then I am...

We used to play with rear camber on circle burners, used the same method as the NASCAR guys do. Never really did see any big results, either positive or negative but we were running on dirt, street use and paved tracks require a lot "tighter" specs on suspension then a dirt car.

Oh yeah, when you do all your suspension measurements, make sure you have the car "loaded" properly with the correct total weight and front to rear weight... Heck, bring it over and we'll put it on the scales, too, and have some real fun!!!!!!!

Dave,

If I set the camber at 0 degree (what VBP suggests for street use) and 1/8" toe. Looks like I'm at -1 degree at jounce (compression of suspension). Looks like the QA's I got are only good for 4" of overall travel. I'll set them up at 60% rested height like Speedway suggests so I have a little more compressed travel. I'm shooting for 2.5" of compressed travel. I know you mentioned some time back to try to go with much more over-all travel. I just cant......believe me I tried to get more. Looks like I'm stuck with a max of 2.5" of up travel. Darn.... I'm trying to set up a 1 1/4 (1/4 wall....fairly heavy) thru frame sway bar from Speedway Engineering. 17" arms. The trouble I'm running into is finding room to make it work. At this time looks like I'm stuck with mounting the bar behind the rear with the arms over the hub....still working on it. Deciding on mounting positions has been a real bear... At this time...no matter what...looks like Ive got some bracket mock-ups (spread out over 2 different factory bolt mounts) to try out. Definitely going to be trial and error. The one place I really want to mount the coil-overs is in the area where they mount the factory spring bushings....I'll have to hog it out....kind of worries me. Dont want to break off the toe strut link...Still thinking. Rich Lagasee did this same mounting location for his coil-overs on his 63 Split Window....but I honestly dont think that car was designed for street use. I'm trying to drop him an email about it. I sure wish I was closer so I could weigh this thing.....I'll get some pics this week-end. I'm sure you guys will see what I mean by mounting issues.....travel issues.....etc. I didnt want to lose any of my bed depth. As it is...I raised my bed 1" so I could raise the frame rails an inch to get the 2.5" travel.

Thanks so much to both of you.....Dave and Jerry! I appreciate the input. Any more thoughts....please post.

Dave

Guys....This might help...and might not. Dont burn me. I'm on over 20 forums....I really thought the Pro Tour guys would help with this...or Digital Corvettes....or Lateral-G's. You two have helped more than anyone. To that....here is some fairly recent pics from my build at another place...

http://www.hotrodders.com/forum/jour...22&action=view

Another note: We were very fortunate to have a pro concrete man pour and level our floor...it actually is perfectly level (well....I know nothing is perfect) with the exception of the drains in the middle. I know I shouldve set up some sort of a jig.....I just felt the floor was real close to level so I've been working off of it. Jack stands are set and havent been moved since placed and tack welded. I hope its sufficient.


Dave

Waiting for the pics....I forgot, what weight springs are you running on the rear????

If per chance you have any circle burner friends around there, you might ask them who they use when they want to scale their race cars...especially the guys with the late model and A mod dirt cars... They do the majority of their chassis setups with a scale...I have a set of scales and let the guys use them for setting up their cars.... I only charge $50.00 for the initial setup, which is about enough for me to clean things out of the shop and get the scales setup and leveled.... Sure does take a lot of the guess work out of chassis setup and builds!!!! Also makes tuning the chassis at the track a whole lot easier when you know where your at as a base point on the weight.....

Originally Posted by Dave Severson

Waiting for the pics....I forgot, what weight springs are you running on the rear????

If per chance you have any circle burner friends around there, you might ask them who they use when they want to scale their race cars...especially the guys with the late model and A mod dirt cars... They do the majority of their chassis setups with a scale...I have a set of scales and let the guys use them for setting up their cars.... I only charge $50.00 for the initial setup, which is about enough for me to clean things out of the shop and get the scales setup and leveled.... Sure does take a lot of the guess work out of chassis setup and builds!!!! Also makes tuning the chassis at the track a whole lot easier when you know where your at as a base point on the weight.....

My bad. I shouldnt have posted that link. I was having trouble posting pics last time so I just ran a link instead. I understand the controversies from one forum to another.....I'm on 20 at this time. Again....I get some of my best answers here. Honestly....when I get this truck in paint....I return the favor much more than I have since joining. I'll try posting some pics again....

I may have lucked out. I found out that one of my old co-workers just got out of dirt track racing....he has a set of scales.....now we just have to fin-agle a price.

Ok....here's a try at the pics again.....I'll use my Flickr site...

And some more....

Looks good so far! I've always like the looks of an IRS on a Hot Rod, and the C4 setup looks like it will lend itself quite well to Hot Rod use! Some very nice work getting things put in their proper place! Should work great when it's all together.

Originally Posted by Dave Severson

Looks good so far! I've always like the looks of an IRS on a Hot Rod, and the C4 setup looks like it will lend itself quite well to Hot Rod use! Some very nice work getting things put in their proper place! Should work great when it's all together.

Thanks Dave. I'll try to make a generalized 'How To' later when I know everything is right.......requesting and/or expecting everyones input for any possible mistakes I have made of coarse. For instance.....the most important measurement on the whole thing.....the angle of the trailing link braket in factory form is 59-60 degrees. I think it can be fudged slightly with less or more as I have seen pictures...but that will depend on where a persons center of gravity (center point of vehicle) and what type of launch they expect....kind of getting back to dragracing set-ups....but I feel it can help a road set-up as well. In my case....I dont know where my the center point of my vehicle is....but...I know it should be fairly low (similar to a vette) (most of my weight will be lower than factory with the addition of x-braces and suspension add-ons) and further back than factory (aluminum LS pushed further into cab area). As I remember you want the center point of the suspension links (meet point of the triangluar links) to be ahead of your center of gravity to keep weight transfer low.....and above the center of gravity to allow more weight transfer to the back wheels. Darn......I wish I could find my DoorSlammers book. I've seen some of these set-up with the triangular links aimed waaaaayyyyy up and I wouldnt think on a street vehicle you would want that much weight transfer.....I'm really not sure what they were expecting Maybe that was the only way they could make the set-up work.

So Dave.....today much cooler up your way??? I woke up to 67 degrees this morn....time to start hacking away.... Have a good day and stay safe.

Thanks,
Dave G

Also, when looking at the factory specs remember they are set up for neutral handling and traction charachteristics so as to make them more forgiving when Joe Blow or whoever drives the car.... Aggressive chassis setups and a harsh ride don't sell well in the new car showroom, but they sure do work good for me!!!!

Temps back in the mid 80's, real tolerable!!!!!

Dave

I know you have been working out coil overs----but did you consider using the leaf spring that came on the vette???
I have shortened them, and the mounting/ride height can be adjusted by the end links
This keeps the car weight off of the lower shock mount ears
Still keeping eye open for my drawings

Jerry