'71 Super Beetle Autocross Build

For road racing, autocrossing, or just taking that curve in style. Oh yea, and stopping!
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ONEBADBUG
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Location: SPOKANE

Re: '71 Super Beetle Autocross Build

Post by ONEBADBUG » Sat Dec 02, 2017 6:16 pm

Did you mean "Toe Out" in the rear, Frank?

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ChadH
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Re: '71 Super Beetle Autocross Build

Post by ChadH » Sat Dec 02, 2017 10:31 pm

FJCamper wrote:
Sat Dec 02, 2017 12:04 pm
You may know this already, but to really make a VW chassis a slalom car, don't use any front axle beam shims, get a ridiculously light flywheel, toe in the rear suspension to create tail-out swing just by leaning in your seat, and get a good solid seat and a harness. If you can breath normally with the harness bucked, it's not tight enough.
It's a Super, with struts, so no I won't use beam shims. ;) I'll have many (maybe too many) ways to adjust the front end, camber plates, easy/cheap spring swaps, some adjustability in caster, etc. I do have a 12lb flywheel to start. I have a new set of Sparko Sprints to install and will use 5-points when I get back to work on the chassis.
FJCamper wrote:
Sat Dec 02, 2017 12:04 pm
Have a working handbrake. No rear disk necessary. You should do about a third of your steering with the handbrake.

Once you can handbrake your car into a parallel parking spot against a curb you know you're good.
I disagree here. Maybe our courses have more flow that what you ran, but grabbing the e-brake would be a sure way to kill speed and cause havoc. It's all about smooth line and maintianing momentum. The courses are typically set up like a mini road course, with wide second gear corners and tons of room to pick a good (or bad) line. It's pretty rare that we have a tight 180-degree pivot cone, or have to grind down into first pivot the rear end and dig out of an exceptionally slow corner. It's also helpfull that I design about half of our local courses, and do set up on every one :)

I don't record my stuff, but here's one of our faster guys on one of our courses as an example.

https://www.youtube.com/watch?v=-s9A0BkUrhI
FJCamper wrote:
Sat Dec 02, 2017 12:04 pm
Cheat and get a 4.86 drag-race ring and pinion. Launch only in second gear after that for your own safety.

Get a short-shifter, a four-puck feramic clutch disk, and new shift-linkage bushings. Once you can make the transaxle scream louder than the engine on a downshift, you are formidable.
On our courses, the start is usually set up with a tight corner immediately off the start. This is to minimize advantages a big HP car would have from a dig, and help even out times between various classes. A little squirt off the line is somethimes helpfull in getting the rear to scoot around that first corner, but a drag race style clutch-dump will do nothing except create smoke, broken parts, and squarshed cones.

Half the reason for doing this car is so I can abuse the clutch without the cost and downtime of fixing a clutch on a modern car. I'm going to run a cush-loc to start (since I already have it) but once I get the car running, I anticipate the need to swap out things like the clutch, once I get the car reasonably sorted.

I have a hairbrained plan to relocate the shifter close to the steering wheel, and make the shifting action as tight as possible. We'll see if it works the way I'd like.

In the interest of cost and actually completing this project someday, I'll just be running the stock '71 tranaxle (4.12 I believe) until I inevitably break it. After that, I'll look into trying to optimise the transmission. I'm hoping I can get by long enough to scrape togeather the $$ for an LSD.

H2OSB
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Re: '71 Super Beetle Autocross Build

Post by H2OSB » Sun Dec 03, 2017 10:24 am

Hear hear!! Autocrossing in a nutshell. And, quite honestly, the super Beetle chassis is very good at it. They start out a bit under powered, but that's easily remedied.

johnL (aka H2OSB)
www.superbeetlesonly.com

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FJCamper
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Re: '71 Super Beetle Autocross Build

Post by FJCamper » Mon Dec 04, 2017 11:25 am

Hi OneBadBug,

Toe-IN. That makes the loaded outside rear tire steer the rear inwards, and is the quick way to snap oversteer unless you're good enough to catch it. Which is the point. We set up road racing cars just the opposite, with zero or even a slight amount of toe-out, to stop rear-end steering.

Rear Toe-in is like a gunslinger's hair trigger. Excellent for a pro, dangerous for everybody else in front of or behind the gun.

Chad, The SB front caster factory spec is two degrees negative. You need a caster-camber plate to adjust to zero caster. The car will then be easy to steer and have little to no forward self-tracking ability. You have to drive that baby. The first thing you'll notice is how much we depend on caster. At zero caster, you'll discover you have a car you can toss around at will but at no time can you count on the steering wheel recentering.

I see what you mean about your slalom courses being downsized road courses. I have myself seen this trend. In my opinion, a slalom course should be full of abrupt, tight moves. Think of a full speed race through city traffic. A slalom is not a scaled down road course. But, what has happened is modern suspensions and tires do not slide well, and the art of hand brake turns is being lost or is lost.

FJC

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raygreenwood
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Re: '71 Super Beetle Autocross Build

Post by raygreenwood » Wed Dec 06, 2017 12:51 am

FJCamper wrote:
Mon Dec 04, 2017 11:25 am
Hi OneBadBug,

Toe-IN. That makes the loaded outside rear tire steer the rear inwards, and is the quick way to snap oversteer unless you're good enough to catch it. Which is the point. We set up road racing cars just the opposite, with zero or even a slight amount of toe-out, to stop rear-end steering.

Rear Toe-in is like a gunslinger's hair trigger. Excellent for a pro, dangerous for everybody else in front of or behind the gun.

Chad, The SB front caster factory spec is two degrees negative. You need a caster-camber plate to adjust to zero caster. The car will then be easy to steer and have little to no forward self-tracking ability. You have to drive that baby. The first thing you'll notice is how much we depend on caster. At zero caster, you'll discover you have a car you can toss around at will but at no time can you count on the steering wheel recentering.

I see what you mean about your slalom courses being downsized road courses. I have myself seen this trend. In my opinion, a slalom course should be full of abrupt, tight moves. Think of a full speed race through city traffic. A slalom is not a scaled down road course. But, what has happened is modern suspensions and tires do not slide well, and the art of hand brake turns is being lost or is lost.

FJC
Extremely well said about castor. On the early McPherson strut suspensions.....411, 412 and super beetle...which are 3 point triangulated on the type 4 because they have a diagonal arm (radius arm) and a little less so on the super because they have no radius arm and utilize the front sway bar for this function and for strengthening for the control arm......castor is SUPER critical for these cars.

They can already have bump and wind steering issues on normal street cars....when they are short of castor. The spec for supers range from 2° to 3.2° on the street. The type 4 was hideously short from the factory at 1.45°. They all need right at 3° to prevent bunpsteer and tramlining...and to self center.....but the farther you get from 1.5° into + territory....the stiff, less responsive and more self controlled they get.

It makes total sense...having driven both 411 and super with effectively "0°" static castor......that it would be great for a track car....but you cannot take your hand off the wheel for a second....and you will need a serious lateral steering damper. Ray

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