Ride height vs Traction

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66NCVW
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Ride height vs Traction

Post by 66NCVW » Sun Jan 14, 2018 5:25 pm

My project 66 is at stock height at the moment. I'm putting a set of m&h's on it for street duty and want to bring the back end down a little bit. I don't have the time/extra cash just this second to do the RLR tranny raise so my question is how far can I come down in the rear before the axle geometry no longer works for launching/drag racing? It's a 66 short axle bug.

Bruce2
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Re: Ride height vs Traction

Post by Bruce2 » Mon Jan 15, 2018 4:51 am

There is no answer for that.
As you lower a swing axle car, negative camber gets greater as you probably know. At some point your tire's contact patch is reduced enough so that you don't get enough traction on the line. The amount of traction you need depends on how much hp you make.

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Chip Birks
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Re: Ride height vs Traction

Post by Chip Birks » Mon Jan 15, 2018 7:15 am

66NCVW wrote:
Sun Jan 14, 2018 5:25 pm
My project 66 is at stock height at the moment. I'm putting a set of m&h's on it for street duty and want to bring the back end down a little bit. I don't have the time/extra cash just this second to do the RLR tranny raise so my question is how far can I come down in the rear before the axle geometry no longer works for launching/drag racing? It's a 66 short axle bug.
I brought the rear of my 60 down a few inches over its 215/65 15s. Its not slammed, but does tuck the tire nicely, definitely sits with some camber. I also run 29mm torsions in the rear. The car has 60ft'd in the 1.60 range, doesn't spin if I launch at 5500rpm with a few psi boost, rolling on M&H 6" slicks. It has clicked off an easy 12.1 in that configuration, making way more power than 12.1s require, but fighting other issues. I'm sure if i spent some time trying to tune the suspension, it would go easy 1.5s, but I just don't really care. The car is wicked fast and feels stable on the street, where it spends 99% of its time.

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66NCVW
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Re: Ride height vs Traction

Post by 66NCVW » Mon Jan 15, 2018 1:06 pm

Chip Birks wrote:
Mon Jan 15, 2018 7:15 am
66NCVW wrote:
Sun Jan 14, 2018 5:25 pm
My project 66 is at stock height at the moment. I'm putting a set of m&h's on it for street duty and want to bring the back end down a little bit. I don't have the time/extra cash just this second to do the RLR tranny raise so my question is how far can I come down in the rear before the axle geometry no longer works for launching/drag racing? It's a 66 short axle bug.
I brought the rear of my 60 down a few inches over its 215/65 15s. Its not slammed, but does tuck the tire nicely, definitely sits with some camber. I also run 29mm torsions in the rear. The car has 60ft'd in the 1.60 range, doesn't spin if I launch at 5500rpm with a few psi boost, rolling on M&H 6" slicks. It has clicked off an easy 12.1 in that configuration, making way more power than 12.1s require, but fighting other issues. I'm sure if i spent some time trying to tune the suspension, it would go easy 1.5s, but I just don't really care. The car is wicked fast and feels stable on the street, where it spends 99% of its time.

Perfect! Thats what I was looking for. Thanks Chip! One more question, what size wheels/offset were you running at that time?

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Chip Birks
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Re: Ride height vs Traction

Post by Chip Birks » Mon Jan 15, 2018 11:02 pm

I currently run 5.5" gas burners from cip1. Not sure on the offset. 3.5 or 4" i think. I have 1/4" spacers behind the rears as the inside of the tire was touching the body to pan mount occasionally. 3" beam with dropped spindles and disks.

I've also run ERCO Star cut outs, 0 offset 3.5" fronts and 6" rears, not sure on the offset, probably 3.5.

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slowsixtyduece
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Re: Ride height vs Traction

Post by slowsixtyduece » Thu Mar 22, 2018 7:06 pm

My old 67 was lowered about 2-3" in the rear (see image below). The tires tucked up pretty nicely and it was not extremely low but it did have some camber to it. With my previous motor (1915 w/ FK-8, Steve Timms heads, 1-5/8" header, etc) I ran 13.7's no problem. My best 60 ft time was a 1.92. Tires were semi-dried out 215/65/15 radials; about the same aspect ratio as the M&H DOT's. Suspension was all stock including old OG oil shocks.

Needless to say, the camber it DID have from lowering it DID NOT seem to make much difference for me.
Old 67 VW.jpg
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risk
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Re: Ride height vs Traction

Post by risk » Fri Mar 23, 2018 10:58 am

My 67 is lowered somewhat with adjustable spring plates, just a bit of camber and around 3/4" of tire to fender gap. 205/65/15 on a 6.5 empi brm with 4.125" backspacing and short axles. I run 28mm torsions which are a little soft on hard launch.

The only problem being lower will be squatting hard on acceleration which is hard on the spade end of the axles and fulcrum plates, and possibly cracking the side gears eventually.. The bigger torsion bars help reduce the squat..but you still need some type of down travel limiter. I can tell you that letting off the gas at 120mph can be sketchy on a swingaxle car. I welded a 1/4" piece of flat stock on each side where the spring plate bottoms out, this limits the down travel when the suspension unloads thus reducing the positive camber. You can also get a clamp on device called the flop stop that does the same.

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