Benefit of shelby drop?

tylerrocks · Oct 21, 2005

I know everyone says DO IT. But through my searches the only is beneift that I could find was lowering of the car. I did this mod on one side lastnight (gonig to finish it up right now) and it didn't lower it all that much (1/2" Like I was told it would do). So I know there has got to be some geometric advantages there, but can anyone explain what has changed geometricly? Also, I have new UCAs, LCAs, spring perches (non-roller), 600 Maier springs, KYB gas adjustables, 1" front sway bar, and strut rod bushings; Will I be able to FEEL the diffrence in a stock to shelby relocation of the UCA?

Tyler

Capt Dan · Oct 21, 2005

http://www.thecarsource.org/shelby/restore/lowering.html

http://www.sunflower.com/~vervaecke/a-arms.htm

red65 · Oct 21, 2005

One of the main benefits of the Shelby drop, besides lowering the car, is correcting the Mustang's original camber curve. On a stock '65-6 Mustang (maybe other years too - don't know), the outside wheel on a hard turn would tend to angle outward at the top, as the outside wheel is loaded and the suspension is compressed. Think about this for a minute - it's exactly the wrong motion. What you'd like is for the outside (loaded) wheel to angle inward at the top as the suspension is compressed, angling the tire more optimally to resist cornering force. The Shelby drop, combined with lowering the front end, helps to accomplish this correction (without spending a lot of time talking about suspension kinematics - someone's already done the math for you!). It only matters in the twisties, but if you mean to drive your Mustang even a little aggressively in anything but a straight line, you'll appreciate the difference. Hope that helps. :Track:

S-Car-Go · Oct 21, 2005

Think of riding a bike and leaning away from the corner. You'd just fall over. This is how the stock suspension works. The shelby drop makes your wheels lean into the corner(or at least stay straight up).

grego37 · Oct 21, 2005

The "shelby drop" really doesnt lower the car too much.
some say not at all, some say 1/2"
to lower the front end you'd need to change coil springs or cut the one's you have.

You used the proper template to mark and drill the new holes......right?
what year car is it?

mfp4073 · Oct 21, 2005

Yeah, lowering the car is not the purpose. Instead it changes the way the suspension reacts to cornering. In laymens terms, under cornering the top of the wheel leans in causing a much better contact patch than the standard setup.

HistoricMustang · Oct 21, 2005

Can someone explain which tire design takes better advantage of the "Shelby Drop" - Bias Ply or Radial?

Any engineers want to take a stab at this one?

HistoricMustang
www.historicmustang.com

302 coupe · Oct 21, 2005

I'm gonna say bias ply since you brought it up Henry, LOL...... I'm not sure why either, but I bet it has something to do with sidewall stiffness.

HistoricMustang · Oct 21, 2005

302 coupe said:
I'm gonna say bias ply since you brought it up Henry, LOL...... I'm not sure why either, but I bet it has something to do with sidewall stiffness.

302, this is something I have actually laid awake at night thinking about. Perhaps the radial designed tires actually "hurt" the early models because of side wall flex and their superior grip.

I know it sounds stupid but perhaps all that grip actually hurts the turning problems that we all know is present in the early model.

I cut class the day they covered "Physics" so this has been a real mystery to me.

At the track I have used both radial and bias ply and the ply does perform better but I do not really know why and if it performs better at the track you would think it would do better on the street. But maybe it does not matter in daily drivers, it matters only when at the limits?

HistoricMustang
www.historicmustang.com

bnickel · Oct 21, 2005

HistoricMustang said:
302, this is something I have actually laid awake at night thinking about. Perhaps the radial designed tires actually "hurt" the early models because of side wall flex and their superior grip.

I know it sounds stupid but perhaps all that grip actually hurts the turning problems that we all know is present in the early model.

I cut class the day they covered "Physics" so this has been a real mystery to me.

At the track I have used both radial and bias ply and the ply does perform better but I do not really know why and if it performs better at the track you would think it would do better on the street. But maybe it does not matter in daily drivers, it matters only when at the limits?

HistoricMustang
www.historicmustang.com

Henry, i think you have to look at a couple things when comparing modern radials to original bias plys and modern racing bias plys.

it could be that when people started using modern radials it revealed a design flaw that wasn't noticed when the car was on original bias ply tires rather than the radial actually "hurting" the performance.

as for the moden racing bias plys you run now they have a very different design than original street bias plys comparing the two is about the same as comparing modern street radials to modern racing bias plys.

modern street radials versus modern racing bias plys is another one of those apples to oranges comparisons since each tire was designed for a specific type of driving and compromises were made to each tire that would make it unsuitable for the type of driving the other tire was designed for.

now if you compare modern racing bias ply tires to modern racing radials you will close the gap up quite a bit, although the bias play will usually perform slightly better than a radial, which is probably more due to the weight of each tire than anything else. the radial tire is pretty damn heavy whereas the bias ply is actually fairly light. the best places to start cutting down weight on a race car is unsprung weight.

then you have to get into the compounds of the tires and etc. so there is really more than one answer to your question but that's pretty much the jist of it.

tylerrocks · Oct 21, 2005

Thanks for all the explinations I understand now and I understood when I drove the car. Grego37, For some reason I couldnt get the printout to be perfect in all demintions so I just used a micrometer and a short level, its a 64.5

Tyler

RGS0907 · Oct 22, 2005

I can't believe my eyes!

Are y'all seriously thinking that bias ply is even remotely close to radials in handling? I've owned 7 Mustangs from my first car a '65 to my '70 GT500 & wouldn't even consider putting bias ply on any of them. The handling improvement is so dramatic that when I recently put a brand new pair of TA's on the Shelby it even felt better than the old vintage TA's that were on there.

Plus, have you ever tried to drive these front heavy cars in the rain on bias plys? I'm getting white knuckles just thinking about it.

HistoricMustang · Oct 22, 2005

bnickel said:
Henry, i think you have to look at a couple things when comparing modern radials to original bias plys and modern racing bias plys.

it could be that when people started using modern radials it revealed a design flaw that wasn't noticed when the car was on original bias ply tires rather than the radial actually "hurting" the performance.

as for the moden racing bias plys you run now they have a very different design than original street bias plys comparing the two is about the same as comparing modern street radials to modern racing bias plys.

modern street radials versus modern racing bias plys is another one of those apples to oranges comparisons since each tire was designed for a specific type of driving and compromises were made to each tire that would make it unsuitable for the type of driving the other tire was designed for.

now if you compare modern racing bias ply tires to modern racing radials you will close the gap up quite a bit, although the bias play will usually perform slightly better than a radial, which is probably more due to the weight of each tire than anything else. the radial tire is pretty damn heavy whereas the bias ply is actually fairly light. the best places to start cutting down weight on a race car is unsprung weight.

then you have to get into the compounds of the tires and etc. so there is really more than one answer to your question but that's pretty much the jist of it.

Very good explanation and makes perfect sense.

These nose heavy machines turning at speed on radials just simply seem to roll over because of the side wall flex negating the superor grip of the radial.

Or, could it be the bias ply actually does provide superior grip turning at speed?

Sorry we got a little off topic.

HistoricMustang
www.historicmustang.com

tylerrocks · Oct 22, 2005

Thats fine, I like ALL types of mustang tech talk. I in fact do not know the diffrence between Bias Ply and Radials (modern, original, street oar racing). Care to explain deeper?

Tyler

rbohm · Oct 22, 2005

when the cup cars went to radial tires, they had to do many changes to the suspension to take advantage of the radial tires extra grip. since you are running race tires, one thing you may or may not have noticed is that you can tune your chassis, when using radial tires, with air pressure adjustments alone due to the more flexible sidewalls. you cant do that with the bias ply tires as the sidewalls are far too stiff for that. also remember that the early stangs were not tunes for radial tires, you are going to have to change caster, camber, toe in, spring rates, shock rates, etc. to take advantage of the superior grip. try a bit more negative camber and a bit less positive caster first. also a bit more air pressure int he front might free up your turn in problems.

oh and when you tune with air pressure, SMALL adjustments are all that is needed. the cup guys will tune with as little as 1/4lb pressure change.

HistoricMustang · Oct 23, 2005

rbohm said:
you cant do that with the bias ply tires as the sidewalls are far too stiff for that.

Believe it is actually the other way around.

The bias plys (because of the stiffer side walls) seem to respond to air pressure adjustments much better than radials.

Thanks,
HistoricMustang
www.historicmustang.com

6T6coupe · Oct 23, 2005

Lowering the pivot point of the upper control arm only has a small effect on the ride height of the car. But by moving the pivot donw an inch, you change the roll center of the vehicle and make it more responsive to turn in. It changes the camber curve of the suspension, making it roll less "positive" as it goes thru its arc.

You'll feel it in two ways, primarilly. The front end will roll less because of the change in geometry and the car will have a more positive turn-in, i.e. the front end will be more responsive to steering inputs.

The Shelby drop is not optimal, but 1" is all you can do without binding the upper ball joint on full jounce. It's also not the best you could do because of the length of the upper control arm. That's why there are aftermarket arms that allow for more drop without bind.

Nevertheless, it's worth doing.

Edbert · Oct 23, 2005

It all boils down to the type of tire within each category and where/how you use them...if you are talking about street tires or racing tires.

I've never had the pleasure of driving a road course near the limit in a classic Stang (I'll be correcting that beforfe too long) but I keep reading/hearing that these old cars like to be loose and need to slide around a bit to get lower ETs. Therefore I would think the old-school bias ply tires would work the best as long as the style they prefer is in line with the driver's style and preference.

For street driving I'd take a radial any day. The improved traction and smoothness cannot be compromized and you should not be at the limit of traction on the street anyhow.

rbohm · Oct 24, 2005

HistoricMustang said:
Believe it is actually the other way around.

The bias plys (because of the stiffer side walls) seem to respond to air pressure adjustments much better than radials.

Thanks,
HistoricMustang
www.historicmustang.com

actually no. like i said the cup car crew chiefs will make air pressure adjustments as small as 1/4lb, where as in the old days with the bias ply tires, they would make small adjustments in the 2-3lb range. it is because of the flexible sidewalls that the radials respond better to pressure adjustments, because you end up stiffening the sidewall in a radial tire. since the bias ply tire sidewalls are already stiffer, you dont get the same change with small pressure adjustments.

Psydwaze · Oct 24, 2005

Lowering the mounting position of the upper control arm makes the following improvements over the stock position; quicker negative camber gain, higher roll center, lower center of gravity and reduced roll rate.

The lower mounting position at the shock tower places the upper arm at an inclined angle which draws the top of the wheel inward at the suspension compresses. This is known as negative camber gain and the improved geometry now keeps the tire in better contact with the road. The inclined angle of the upper control arm also moves the roll center of the front suspension upward (roughly 1/2" if memory serves me), closer to the center of gravity of the vehicle. The closer these two points (roll center and center of gravity) are together the lower the roll rate, making the stabilizer bar and springs more effective at controlling the vehicles tendency to roll when cornering.

As an extreme example, if the roll center and center of gravity are at the exact same height the vehicle will exhibit no body roll and would not require anti-roll bars.

Benefit of shelby drop?

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