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Discussion Starter · #1 ·
Hello All:

Quite a while back, I started a thread on the subject of using the limit straps on the rear axle as a method to control body roll in Series 3 Spiders. Unable to locate that post with Search, but as I recall, several folks weighed in with thoughts on how handling would be effected, as well as the always present possibility of unintended consequences.

Here's my thinking on the subject and a summary of my results:

It has always seemed to me that if the 2-3" gap between the axle and the limit straps could be eliminated, rear body roll could also be minimized since the body could roll no further than the amount permitted by that gap. As we all know, the "flexible flyer" characteristics of unmodified Spiders allow the front and rear of the car to operate pretty much independently in regard to roll.

My concept was to minimize the "limit strap-to-axle gap" and the next challenge was how to do that in a tunable, easily reversable way (no shortening of straps :)). I accomplished this by inserting four (4), stacked, 1 1/2" segments of bicycle tire into the gap on each side and securing them with a heavy nylon tie wrap. (The process involved loading the suspension and does not require extraordinary talent.) After the 4 segments were installed, a small gap remained above the top piece of bicycle tire, and combined with the compressibility of the tire segments, still allow for some degree of downward axle travel.

Reno SCCA's Autocross at Reno/Fernley Raceway this Sunday seemed an ideal venue to test my idea, and in keeping with cautions proposed by folks who responded to my first post on this subject, I cinched up my sealt belt extra tight :rolleyes:.

A bit of background. I'm not able to participate in Autocross on a regular basis and subsequently I don't run in a class, but simply "no points". Also, my overall ranking is usually measured not by seconds, but with a calendar, if you get my drift. I believe the only reason I'm tolerated is that I can usually be counted on for at least one, massive, crowd-pleasing spin out.

Anyway, things were very different this Sunday. After two runs to lock in the beautifully laid out course, I attacked the track much more aggressively than usual and was amazed to discover how much more neutral the Spider had become. Full throttle exits resulted not in the usual oversteer and occassional spin, but with well controlled, predictable handling :).

If you look at Sunday's results (below) you'll find me in position 38 of 46, but more significantly you'll see that I'm within 3-4 seconds (an eternity, I know) of perhaps a dozen worthy adversaries. Not too shabby for a box stock, 120k miles, almost eligible for classic plates, Spider. Also, a gentleman visiting from MI with his Series 4 Spider (Mr. Small, if memory serves), bravely rode along on my last run and commented positively on the handling.

The 50 mile trip home was uneventful and on the mostly smooth roads, my mods were transparent.

2011 Round 10 Raw Results

Looking forward to comments and perhaps a technical explanation of what is going on. Insights into unintended consequences are welcome.
 

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Any pics of said modification?
 

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Discussion Starter · #3 ·
Pics

Paul:

You'll smile when you see how simple it is :).

Film at 11

One other issue...I'm concerned there may be a powerful placebo effect at play here. Just took a short ride and upon my return, looked under the car and found my bicycle tire inserts hanging off the straps from the tie wraps ??!!. When that happened, I can't say. Unfortunately, probably at the track. Hmmmm.

More development and testing is clearly indicated :(. The price was definately right, however.

At the advice of Counsel, "Don't try this at home", YMMV, "past performance is no guarantee of future results" and "Don't send cash in the mail".
 

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it's almost a alfa romeo spider
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hey..it's 11 pm some where.. WHERES the photos???:):):)..i am not getting any younger, you know:):)
 

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on the straps,, if they are at least 12" long( the bike tire psrt) can you just not drill a few small hole and bolt them togeather like alfa did futher up the strap?
 

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Discussion Starter · #6 ·
I know you folks are pacing up and down awaiting pics.

Soon...

How soon?

Real soon...

Gotta put it back the way it was, with Bianchi's suggestion, then wait for the nest Autocross for a proper test. OK, scratch the Autocross. I'm on it!

And Bianchi1, the tire segments are only 1 1/2" wide and, when stacked, snuggle up under the axle.
 

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I'am turning blue:):):)
 

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Lowered the rear end?

I'm famously bad at visualizing things but it sounds to me as though what you have accomplished is the equivalent of shorter stiffer rear springs if I'm grasping this right.

Basically you're loading the coils and thus stiffening and shortening them thereby pulling the rear of the car slightly downward , right? Would't this be the same as cutting one coil off the springs?
 

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i think he jsut took up the belt slack under the axle, not shorting the spring, just taking up slack..
 

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I'm famously bad at visualizing things but it sounds to me as though what you have accomplished is the equivalent of shorter stiffer rear springs if I'm grasping this right.

Basically you're loading the coils and thus stiffening and shortening them thereby pulling the rear of the car slightly downward , right? Would't this be the same as cutting one coil off the springs?
Same here I need to see it I feel I know what you did but I'm visual or so I keep telling my wife when she catches me watching skinamax, but i digress, look forward to seeing pics when available.:D
 

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Discussion Starter · #11 ·
Limit Strap Mod Pic

Hello:

Thanks for your patience.

Here's a picture of the bicycle tire segments hanging by a tie wrap from the limit strap. Have not had time to reposition and secure, so just imagine the 4 segments rotated CCW between the strap and axle.

Clearly there much more lateral motion back there than I anticipated and a better way to retain the segments is needed. Although they did come loose during Autocross, I've convinced myself they were in place during my fastest run...or not:(.

Steve
 

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But Mad North-Northwest
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I think if you want to control roll you'd be much better off going with a stiffer roll bar or stiffer springs, or both. While that'll cost money it'll give you a safer, smoother transition as the body rolls.

The issue with a "hard stop" like you're proposing is that in hard cornering you might get a very nasty transition from the body rolling on the ARB/springs to it suddenly applying all the force to the axle and lifting the outside wheel. I realize you're trying to minimize this possibility with the rubber tire pieces to make it not exactly a hard stop, but even with those in place I'd be worried about the non-continuous response to roll forces.

IIRC there was an "anti dive" kit for the transaxle cars a long time ago that sort of worked like this: basically a stop with a small rubber bush to limit how far the body could rise over the rear axle. I am told it was a very poor idea in practice.

Ah, here's a pic: http://www.alfabb.com/bb/forums/alfetta-gtv6-1975-1986/42286-dedion-brace-maybe.html
 

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Discussion Starter · #13 ·
Input appreciated

Tom:

"a stiffer roll bar or stiffer springs, or both"

Do ya think :):):)?

All seriousness aside, my days of putting more discretionary $$$ into the Alfa are gone. Just tires and essentials for now. Hence the wild and crazy bicycle tire concept. Abrupt transitions you mentioned were not an issue as the QV tracked well thru corners and I was especially pleased that acceleration out of corners did not result in the usual oversteer issues. Can't speak to lifting an outside wheel since it was not in my line of sight :) and no course wokers mentioned anything. As you also observed, my thoughtful choice of scientifically selected bicycle tire segments (4 seemed to fit just right :)) may have provided a transitional cushion (vs the hard stop you are concerned about) during vigorous roll situations.

Just wish I had been paying more attention and knew when things came apart on me. For all I know, I didn't even make it to the track with my mod in place :).

Gonna tighten things up and sneak into the DMV testing lot some evening this week. Spin outs were always easy for me to initiate so I'll be able to tell if things have truly improved. Next Autocross is not till Labor Day at RFR.

Thanks again for you observations.
 

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Good on you for trying a theory out, but my experience in racing with a 105 is that this is the wrong way to go. Droop limiting will not prevent roll, it will just lead to you picking up an inside rear tyre, therefore reducing the lateral grip that you have available and the point at which you can apply power before the apex. This chassis is inherently grip limited at the rear (which makes it fun, up to a point) and doing things that make that situation worse is not recommended for road use or track racing (maybe an option for autocross however...).

For an otherwise standard car, you might want to look at seeing if you can lengthen the straps to allow for the inside rear to stay on the ground during extreme roll. I've not tried this (I went from standard to bigger springs and front bar) and am not sure how much extra travel you could find without causing a problem. Maximising wheel travel is a holygrail for suspension engineers, so if it was easy, I'd say that Alfa would have done it already (they do have a lot of experience after all and rarely muck it up fundamentally). However, it you want to experiment further, it may be worth looking at - otherwise, bolt on a big front swaybar as it is really your cheapest and best option.
 

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You are supposed to control body roll by the end of the car that does not have to deal with traction issues, thus in your Spiders case that would be the front end.

Why?, because you want to keep the driving wheels in contact with the ground all the time.

The purpose of the limit straps are I believe to stop the rear shockabsorbers pulling apart. Why Alfa Romeo use this design instead of specifying shockabsorbers that are strong enough to look after this I do not know?. No other car that I am aware of uses limit straps, they all use the shocks.
Pete
 

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I like the ingenuity! But I would third what the guys from Downunder have said - a front bar is the best first step, a second choice would be stiffer front springs. Free suspension tuning can be found through tire pressure tuning. An old trick is to use white shoe polish on the tire edges to measure tire roll, then adjusted pressures to equalize front to rear. Increasing pressure at the heavier front could help balance things out.
 

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Discussion Starter · #17 ·
The presidents blink at the light when I open my wallet.

Thanks for the compliment on ingenuity...born of my penurious nature :).

Not as fussy about tire pressures as I need to be either. Oh!, white shoe polish. No wonder that tip never worked so well for me.

Will provide progress reports as the situation develops.
 

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Another helpful thing to do is to put cable ties around your shockabsorber shalfs. This will tell you the max movement your suspension is going through, as the cable ties will get pushed up and stay in that position.

Why is this important?, because you need to keep your car OFF it's bump stops. That is the only reason you ever need to stiffen a car. Once a bump stop is used during cornering your suspension rate goes through the roof and you loose grip.

Thus if your car is not hitting it's bump stops it does not need to be any stiffer, spring rate wise.
Pete
 

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Discussion Starter · #19 ·
Pete:

Will take your advice on the tie wrap iaround the shock idea. I have noticed wear marks on my bump stops but don't know how my current mod is affecting that situation. Also notice the anti-roll connector rods on each side have hit the upper spring mounts hard enough to dent them on both sides. Lotsa roll! I know, I know....stiffer springs!!

Will put the TR's on when I determine how to get those tire segments to stay where I want them to be.

Thanks again.

Steve
 

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Discussion Starter · #20 ·
More on the DIY Suspension Mod

Due to a diminishing number of requests, I've chosen to provide an update on my rear suspension mod involving bicycle tire segments placed between the limit straps and the rear axle. When last I reported, the single lower tie wrap proved inadequate to the task of holding the segments in place against higher than anticipated lateral rear suspension/axle movement and after in-depth analysis of the situation by the guys and gals back in Product Development, a decision was made to add two more tie wraps as depicted in the accompanying photo.

The shiny object may be recognized as a deep well socket, temporarily inserted to displace the limit strap and show more detail of this extremely high tech change to my suspension :). Additional development work is ongoing in regard to how short to cut the loose ends of the tie wraps and a full report is expected from the folks in P.D. by early next week.

Obviously if I decide to take this concept to market, I will upgrade from nylon tie wraps to stainless steel hose clamps (but only for the first 100 callers :)). Use of bicycle tire segments from a new bicycle tire are also under consideration but may not be feasible due to the desire to keep the package price under $49.99 (S&H extra). But wait, there's more! Actually, no there isn't, except to say that a previously unemployed English Major is currently laboring on the first draft of an anticipated 25 page installation manual, fully indexed, foot-noted and cross-referenced including several "8 1/2 X 11 color glossy photos, with circles and arrows and a paragraph on the back explaining what each one is about".

Ultimate performance results await SCCA Labor Day Autocross at Reno/Fernley Raceway and in the meantime I'll do some local driving to ensure things hold together. In the immortal words of Han Solo, "Hold together, baby, hold together".

Earlier comments on my efforts regarding this mod by those far more knowledgeable than myself (including just about everyone on the Forum :D) are much appreciated and in a continuing effort to minimize the body count as development proceeds, vigorous testing will be performed exclusively on the NV DMV parking lot, at night and with my seat belt snugged up extra tight.

Also, forgot to mention, but the legal crew is currently initiating a comprehensive patent search. For those who are concerned about development costs to date, the brutal economy here in Nevada has allowed me to staff up with unemployed technical and legal types who are working on a contingency basis, based upon ultimate project profitability (if any:D). Yep, that's how bad it is out here.

Note: contributions by sympathetic parties may be sent c/o Gov. Brian Sandoval with checks made out to NV Dept. of Treasury. (Do not send cash in the mail). Unfortunately, the situation here is no joke :(.

Gotta go and finish work on son Dave's SV650.

Film at 11
 

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