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[rat_rod_russell]

So for those that remember me, I have a 1957 Chevy Truck, all C5'C6 corvette suspension, LQ4 STS twin turbos, coil overs, adjustable swaybars.

Bull shit propaganda link
http://www.hotrodjim.com/projects_shop_57_truck.php

I'm looking for someone to give my design a quick review. I'm running 275's up front and I've gone to a Flaming river rack and pinion. With my steering arm I will have 34 degrees of turn in and my tires will finally clear the inside of the frame under that much turning radius, the shock towers have been significantly redesigned and I have room for the exhaust and the steering linkage too.

Some pics

   

   

 

and for my tech friends who want to look at a 3D model to get a better look
eDrawing Link
http://dl.dropbox.com/u/26014887/Stage_2_Version_5.40_PT-57_Chassis_Complete_Assembly_4_w_motor.EASM
3D PDF (works like a pdf, no special software, but you can spin the parts zoom in and out to look at it better)
http://dl.dropbox.com/u/26014887/Stage_2_Version_5.40_PT-57_Chassis_Complete_Assembly_4_w_motor.PDF

Your thought?

Thanks
-Russell

[Derrick]

Interesting project.  If your goal is to have the truck "driftable" in the sense that the vehicle is not unduly disadvantaged for the occasional drift duty, then you will surely want a bit more steering angle than what you have achieved even now.  There's no magic number, but from my experience, cars with <40 degrees of angle are generally difficult to "balance" while drifting and will leave drivers frustrated.  The corvette is a great example of an exceptionally well handling car that is borderline hopeless on the drift track on account of insufficient steering angle.  Unfortunately, to escape this you may be facing further compromises in your front suspension design which you may not feel comfortable with.

Barring a complete redesign of the front suspension system for drifting, the next best thing might be to just go the easy route and simply run less wheel back-spacing, and a narrower wheel if fender fitment is an issue.  A big compromise this might appear, but a compromise that could be made exclusively for drifting and reverted for any other activity the truck sees duty.  To keep the steering in check with the wider wheels installed, you could whip up some adjustable steering stops or removable steering rack travel limiters to keep the 275s from hitting the frame rails at lock.

With the narrower wheels and lower backspacing, you may have concerns with the lowered grip level and increased scrub-radius.  While these might not be optimal, the tradeoff for the extra steering angle is very much worth the sacrifice, and the vehicle will perform much better and be more rewarding to drift.

Also, as Mike said, check that the brake caliper won't be hitting the shock or lower control arm at full lock.

[rat_rod_russell]

No problem with the caliper right now @ 34 degrees, I just have it all suppressed so my computer doesn't lockup when I'm trying to work on it.

When I last had the truck running she weighed in a 3398 lbs, just call it 3400. My goal is to get the weight down to 3000 in full street trim with a few creature comforts. The corvette C6 corvette will only hold around 30 degrees of turn in at full lock and has a 106" wheel base. I'm looking at 114.75". My plan is more along the street car / road racing territory but the more time i spend in a friends vette with the ass out the more I want to do it in the truck when its done. Now granted I can't hold the angle you guys do and so that's why I was looking for more info on turning angle. The original plan for 275's up front is for the road racing end of things, shut it down, turn in, grip into the corner and get a little lift under hard acceleration out. But that's for road racing when I'm running the 345's out back and lets face it no one without a pro sponsorship can roast that much rubber all the time and afford it.

So for a better drift setup I should look into more turn in, you say 40 at least and I see people cutting the steering arms and moving them back but do you correct for the ackerman or is that even really important on a drift car?

Thanks
-Russell

[fivehunsky]

My car has something around 52-55 degrees I think? I haven't checked again since I removed my rack limiters.. Just to give you an example of what kind of angle is alot. Most cars we measured were from 45-55 degrees. With modified parts to get there or near stock. 

[fivehunsky]

Also, I can't see your pics for some reason. Are you front or rear steer? Double a arm I'm guessing?

[rat_rod_russell]

yes, front steer dual A frames.

I have a bolt on steering arm so I can nail out the ackerman per chassis since I do quite a few of these for different cars. So it sounds like you guys have the front suspension more parallel than with proper pitch in?

I ask because I can't really move the rack back any more with out the motor coming further back and there's no room in the cab for that. I could make a drift specific steering arm to bolt on and swap down to a 235 or 245, I have some of those on 8" wheels lying around, but as noted earlier, I might need to go to a smaller caliper as the 6 pistons are rather large one the back side. How badly do you all see scrub radius affecting the turn in grip? I didn't know if anyone had put on some smaller tires with spacers to get them out so they will clear the suspension and checked to see if they were destroying the inside edge of the tires or not?

Thanks again for answering all my questions.
-Russell

[Derrick]

So for a better drift setup I should look into more turn in, you say 40 at least and I see people cutting the steering arms and moving them back but do you correct for the ackerman or is that even really important on a drift car?

Thanks
-Russell

Ackerman doesn't appear to matter all that much in a drift car.  It might affect turn-in a little, but once the outside wheel has been turned to significant lock, the caster cross-jacking force unloads the inside front tire considerably, and it's free to scrub along the pavement lightly without consequence.  Speaking of caster jacking, large amounts of scrub enhance this effect, to good end in drifting I think.  The caster cross-jacking helps keep the front-rear tire grip balanced by loading the inside-rear with increased steering lock, which generally corresponds with a growing rear tire slip angle and waning lateral grip at that axle.

[rat_rod_russell]

You are really, really, really, really overcomplicating this.

Get yourself as much angle as you can, and downsize the front tire.  How much tire do you really need to turn in on a 3300# vehicle at 60mph while breaking the rear tires loose?

If your overengineering this thing this much, chances are you are going to be just as competitive as any of us at wanting to hold big angle.  Unless you can get 45+ degrees, you're just going to be frustrated.  Downsize the front wheels/tires (I'm only going to run 225 on 7.5'' fronts on my 72 Camaro FWIW) and get as much angle as you can.  Then put some steering stops on it for when you have big tires.

Summary:
Get as much angle as possible.

Sorry for being such a pain in the ass. I'm really just trying to get a better understanding of how everyone else does there setup but I'm looking for real numbers and guys like you who get and record that information (not pulling numbers out of there asses like so many do). btw thanks again. Do you mind if I get your caster camber setting and wheel offset so I can play with your number to see what it does. It will help me visualize it if I can make some quick transparent 3d models and play with them in the computer (cheaper too).

So for a better drift setup I should look into more turn in, you say 40 at least and I see people cutting the steering arms and moving them back but do you correct for the ackerman or is that even really important on a drift car?

Thanks
-Russell

Ackerman doesn't appear to matter all that much in a drift car.  It might affect turn-in a little, but once the outside wheel has been turned to significant lock, the caster cross-jacking force unloads the inside front tire considerably, and it's free to scrub along the pavement lightly without consequence.  Speaking of caster jacking, large amounts of scrub enhance this effect, to good end in drifting I think.  The caster cross-jacking helps keep the front-rear tire grip balanced by loading the inside-rear with increased steering lock, which generally corresponds with a growing rear tire slip angle and waning lateral grip at that axle.

Now this makes since. With lots of positive scrub radius like your talking about with the rear suspension under full load and in a hard squat I see the front out side tire rolling in and not having much or any grip at all now that you point that out. So if your front wheel with the traction has the right amount of caster for that much turn in and the right amount of camber to feather it out and keep the optimal foot print to the ground then I can see how that would really work out to make the car easily swap able to a drift configuration.

My big thing is I'm young with my own shop. I can't just go out and build a toy I want, I don't have enough work to justify that. I have to build something that I can use to benefit my shop first and find a way to make it fun for me later. I WANT TO DRIFT, but I can't rightly see building a dedicated drift car for my shop, I just don't see that much money in the industry from where I stand to make that investment. Right now my best customers want to autocross and road race there old cool cars and then drive them home. You need a new frames to handle all of that that. So I design and build these frames so they can be modern CTS-V's or Z06 Corvettes under 55 Chevy's and the like, and I've done pretty well so far. But all these cars are street cars first and race cars second. So my goal is to gain a better understanding of drifting. Then work on little things I can design now and bolt onto my tuck so after I road race, autocross and car show it in the hot rod circles I can make some little changes (that have already been planed for) and have a fun drift toy.

Derrick, whats your setup? if you have a build thread or and about my car thread I would be more than happy to read it. Same with your car Mike, so you guys won't be repeating yourself.

Thanks again
-Russell

[Derrick]

Now this makes since. With lots of positive scrub radius like your talking about with the rear suspension under full load and in a hard squat I see the front out side tire rolling in and not having much or any grip at all now that you point that out. So if your front wheel with the traction has the right amount of caster for that much turn in and the right amount of camber to feather it out and keep the optimal foot print to the ground then I can see how that would really work out to make the car easily swap able to a drift configuration.

I don't think you need to worry too much about front wheel traction levels, or the effects of the positive camber that caster and SAI bring with lock.  Generally speaking, the front axle does loose considerable traction due to the loss of footprint and cross jacking forces unloading the inside, but don't forget the rear axle looses traction too with increasing slip-angle.  In a way the too axles keep some degree of "balance" by loosing traction together with increasing drift angle, although the rear always seems to loose traction more quickly no matter how much the outside front is leaned over.  You're on the right track, but there's really no special considerations you need to make for drifting except for steering angle.  Conventional suspension setups for autocross or road-race are a great starting point that won't hold you back.