Mustang Handling - Fact and Fiction

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Spanner Monkey
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Mustang Handling - Fact and Fiction

Postby Spanner Monkey » Sun May 17, 2015 9:56 pm

First off you have to decide what you want to use your car for. There is no universal fix that will allow it to be a tight-handling track-weapon on the weekends and still ride the bumps of the English roads without knocking your teeth out on the daily commute, so you need to really think what you want to use it for. Don’t get swept away by the ‘I’ve got full race suspension’ bragging rights at the pub as you will hate to drive it to the pub if you do that. I know many people who have spent thousands of dollars modifying their rides way past what was necessary, way past their own driving abilities, and way past the point it was still a capable road car.
As most (if not all) handling improvements rely on the quality and adhesion of the tyres, and the skill of the driver we will take as read that the tyres are part-worn, super-sticky road and track type tyres at the correct pressures, and the driver is a close relative of the Stig. If your tyres are Nang-Kang remoulds then it doesn’t matter how much of the following you do, it will still handle like a camel with wobbly knees….
My suggestion would be to do these suspension mods in this order. If you decide to do all the mods in one you will never know what works for you and what doesn’t!
Step 1. Springs.
First step is to lower and uprate the springs. You don’t need to go super-stiff, just ‘fast road’ type. FRP, Eibach, Steeda et al do 2 ‘strengths’ of springs for each length. Go for the soft option but do some research as to which company produces the springs that best suit your car. I have two reasons for suggesting the softer option:
1)Road comfort. Stiffer springs will have your fillings out and dislodge your contact lenses the first time you hit a pot-hole, and you don’t want to return home to Mrs Mustang looking like you’ve just done a few rounds with Merryweather.
2)If you’re on a track-day, unless the track is warm and perfectly dry you will not see the benefits of stiffer springs. Soft springs allow compliance and that is what you need for grip in damp/wet conditions.
With leaf-sprung cars you need the stiffness to stop axle wind-up, but the softness to retain compliance and ride. The Spanner Monkey tweak is to buy the stiffest springs you can and then cut a leaf at a time from behind the axle until you’re happy with the ride. Ever wondered why those classic leaf-sprung race cars get around corners so quick? Take a peak underneath them and you’ll see this mod.
Step 2. Shock absorbers.
Ideally fit adjustable dampers so you can adjust them for your driving style, and if necessary tweak them up for track use and down for road use.
At worst just fit a good set of aftermarket shocks. Google search for the best ones for your vehicle as there will be 1,000’s of people before you who’ve tried them all.
Step 3. Bushes.
Stiffer suspension bushes will give you a noticeable improvement in handling, reduce brake vibrations and probably be cheaper than just renewing the rubber ones. Personally I’d avoid using Rose Joints (Heim Joints, Spherical Bearings) for a car that’s used on the road as they transmit too much road noise and as soon as they get a small amount of wear they become ‘clunky’.
If you do decide to uprate the bushes do all of them. Most owners will replace rear axle lower arms (on coil sprung cars) without a thought to the upper link bushes. A chain is as strong as its weakest link and all that.
Step 4. Sway Bars.
Or Anti-roll bars as the Brits like to say. Only really necessary if you’re serious about track work. If you are going to fit uprated ARB’s then make sure they are adjustable. Again as a rule of thumb you need soft (or no) anti-roll bars in the wet, and stiff anti-roll bars when it’s dry and hot.
Step 5. Body stiffness.
Somewhere through the above processes, particularly if you’re running ‘stiff’ (oo-err missus!) you may encounter some kind of body flex and decide to stiffen things up a bit.
Probably the first thing you’d be tempted with is a strut brace. There are two distinct types: those produced to look good and those produced to work. Do some research and buy the best. Don’t waste money on something that will look good but do sod-all.
Subframe connectors are a reasonable bet, but again the aftermarket is littered with good and bad. My advice would be to make your own (or get a good fabricator to make them for you) and that way you can control the quality and stiffness of material and fittings.
A good 6-point (or better) roll-cage will stiffen the whole structure. I believe the grand-poohbah of this site had a roll-cage fitted to his S197 and reported a noticeable difference in stiffness.
Myths and legends:
If you own a Mustang it’s about 99% certain that you have a live axle hanging around in the back somewhere. Don’t get fooled into buying lots of unnecessary bolt-ons as it’s a ‘Cart axle’, as with minor suspensions detailed above it will hustle round a track as fast as many fully-independent cars.
Panhard rod vs. Watts link. I challenge anyone to really tell the difference on a well set-up car. Those who have bought a Watts-Link conversion will 100% tell you that it’s better than a Panhard Rod, but that is probably because a) the Panhard rod they removed had worn and sloppy bushes, and b) they have to justify the huge amount of money they’ve paid to add a few kilos to the unsprung weight of the car. Think about it……
Don’t believe anything the Americans tell you. Bitter experience has taught me that the American way of making a car handle is to make it stiffer than a go-kart. Works well on a mill-pond smooth, hot, sticky track (or on the I4, 192 and International Drive commute) but will be an absolute bitch on your public roads. Talk to people who know, not just those that have an opinion!

All opinions expressed in this article are not necessarily those of the forum management. If you have enjoyed this Spanner Monkey blurb I may well put finger to keyboard and do the same with brakes, power, electrics, bodywork, tyres etc . but don’t hold your breath!

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Re: Mustang Handling - Fact and Fiction

Postby Mustang Barry » Mon May 18, 2015 10:08 pm

I wanna know more. Especially about older 60's/70's cars.

So apart from springs, shocks, bushes and stiffening, what about geometry? Caster, camber etc. There's plenty of bolt on kits out there that claim to be 'race proven' and give modern levels of handling with these things in mind. Can model specific, off the shelf units, make a wallowy old barge handle like a modern girl's car?

Is there an optimum level of handling performance limited by the car itself?

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Re: Mustang Handling - Fact and Fiction

Postby Spanner Monkey » Tue May 19, 2015 1:30 am

Mustang Barry wrote:I wanna know more. Especially about older 60's/70's cars.

So apart from springs, shocks, bushes and stiffening, what about geometry? Caster, camber etc. There's plenty of bolt on kits out there that claim to be 'race proven' and give modern levels of handling with these things in mind. Can model specific, off the shelf units, make a wallowy old barge handle like a modern Hairdresser's Car?

Is there an optimum level of handling performance limited by the car itself?


The same applies to the older cars. Older American cars have a terrible reputation for handling, but as all most of the 'reporters' have driven are 30+ years old examples I'd take that with a pinch.
If you have the aforementioned 60's or 70's Mustang, pay particular attention to the steering/suspension bushes and joints. Because the front suspension layout actually has the top arm under pressure all of the time it's not easy (or even possible in some cases) to check the wear. I've seen 60's Mustangs that have been checked time and time again for handling issues and given the all clear, that when you pull them apart there is huge amounts of play in the top arm and top balljoint.

Of course camber and caster will have an effect on handling. Caster angles on most cars are pre-set, and providing they are still within manufacturers tolerances I don't see any reason to mess with that.
Camber however is another can of worms. Look at race cars and you'll see the camber angles are huge. This is effectively set so when the tyre is at full load on a corner the opposite way to the loaded tyre (ie a right-handed corner it is the left of the car that is loaded up) the tyre will sit flat and get the maximum amount of tread in contact with the track.
On a road car the same applies, but because the tyre adhesion levels (and therefore the loads able to be applied to them) are considerably less, the camber angle needs to be less.
Excess camber angle will, of course, lead to uneven wear of the tyres, and it can often make the car feel jittery as it will be running on less of the tyre that it was designed to be run on. Effectively like removing 8" wide tyres and fitting 4" wide tyres with a bigger inset - the loads on the tyre and effect on handling will be the same.

Hopefully the lists of improvements suggested in my initial blurb will go some way to make a wallowy old barge handle like a hairdressers car. If you want a nice compliant, comfortable ride concentrate on suspension bushes and shock absorbers.

And to answer your last question - yes. Optimum handling is affected by vehicle weight, weight distribution, wheelbase and track, suspension design and wheel/tyre size. Whilst it's relatively easy to make a car lighter, alter the suspension and rolling stock it is very difficult to make a significant change in either wheelbase or weight distribution.

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Re: Mustang Handling - Fact and Fiction

Postby Mustang Barry » Sat May 23, 2015 2:31 pm

Thanks Mr. Monkey.

So let's say I have a classic muzzy. A '68 for arguments sake. I want it to hustle round track and road like the best of them. I'm willing to compromise on comfort (its not a daily driver) to gain on track handling, but bear in mind, it will be driven to the track and for Sunday blasts etc. I want it to be sharp as it can be. What would you do to sort it out?

NB This wouldn't be a bottomless pit build, but the budget could flex to accommodate some quality components and some skilled labour.

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Re: Mustang Handling - Fact and Fiction

Postby Spanner Monkey » Sun May 24, 2015 9:05 am

Classic Mustang Handling 101.
Been done 1,000's of times so much of this won't be news to anyone, but I'd do the suspension mods in this order:
1. Rebush everything. Fit new bushes to all of the suspension joints and mounts and preferably uprated (Nolathane or similar) bushes.
2. Do the Shelby upper wishbone mod. This effectively drops the inner mount by about an inch and increases camber on bump.
3. Uprated shocks and adjustable ones if you can afford it.
4. Lowered/uprated springs, and do the rear leaf spring mod mentioned earlier.
5. Adjustable anti-roll bars.
6. Stiffen the chassis.

Although it goes against everything I've said previously, if finance is an issue then do all of the front suspension mods in one, that way you will only need to dismantle it once and therefore save 4xlabour costs.

Wheels and tyres to suit your own taste, but don't go too radical on the offset of the front wheels as it will negate some of the positives above.
There is another major (and I do mean major) handling modification, but with apologies (as it leaves your question not fully answered) I will save that for a later 'Top Tip' that I'm brewing at the moment.

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Re: Mustang Handling - Fact and Fiction

Postby badhand » Sun May 24, 2015 10:31 am

So you'd really stay with leaf springs? Rather than IRS if you could fit to a '68...

I know there's a lot of debate as to whether there's any real-world advantage of IRS, but surely there must be?

And what about the many aftermarket rear coilover systems. Waste of time?

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Re: Mustang Handling - Fact and Fiction

Postby Spanner Monkey » Sun May 24, 2015 9:00 pm

Yes, 5 link and coil-over will give you a distinct advantage purely for the adjustability it affords.
IRS - a load of cash for an advantage that I challenge you to notice. Great if your trying to shave 10ths of a second off lap times (or bragging rights!), but for road/track attack - nah.

I thought the remit for this was budget? Give me a well set-up leaf-spring car at a very small budget and not only will I run rings around your 'budget' IRS car, but I'll have the spare cash to celebrate in the bar afterwards....

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Re: Mustang Handling - Fact and Fiction

Postby badhand » Mon May 25, 2015 6:38 am

Ah. You didn't make it clear this was handling on a budget. Or maybe I just wasn't paying attention... :oops:

So in a nutshell, your rear upgrade recommendations are:

If you're potless, do the leaf trick.
If you've got a bit of dosh - 5 link coilover kit. (5th link being the panhard bar?)
If you're totally caked, obsessive and mental - IRS.

In your experience, could you put a guideline figure on performance gain from stock?

For example:
Leaf / Spring - 120%
Coilover kit 150%
IRS - 151%

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Re: Mustang Handling - Fact and Fiction

Postby Spanner Monkey » Mon May 25, 2015 8:18 am

Budget comes from Barry's post:
Mustang Barry wrote:NB This wouldn't be a bottomless pit build, but the budget could flex to accommodate some quality components and some skilled labour.


Ref the performance gains from each mod, depending on set-up and using similar strength springs and dampers for each set-up I'd go:
Spring mod (uprated bushes etc) 150% (taking 100% as good standard)
5-link 180%
IRS 190%
But don't quote me on that!

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Re: Mustang Handling - Fact and Fiction

Postby waylander » Mon May 25, 2015 10:49 am

Spanner Monkey wrote:Ref the performance gains from each mod, depending on set-up and using similar strength springs and dampers for each set-up I'd go:
Spring mod (uprated bushes etc) 150% (taking 100% as good standard)
5-link 180%
IRS 190%
But don't quote me on that!


too late :lol: :butt :lol:

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Re: Mustang Handling - Fact and Fiction

Postby Mustang Barry » Mon May 25, 2015 11:14 am

Thanks Spanner Monkey.

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Re: Mustang Handling - Fact and Fiction

Postby Spanner Monkey » Sun May 31, 2015 8:38 am

As a prelim to the new ‘Top Tip’ (coming next week to a website near you) I’d like to expand on the subject of handling if you are really set on those tenths of seconds off your lap times.
The weight of your car is measured in 4 ways:
Total weight - Obvious really, this is the total weight of the car. This can also be split into ‘dry weight’ (no fluids) and ‘wet weight’ (with fluids – ready to run).
Weight distribution – the percentage of weight over the front and rear axles. Ideally you want the split as near 50/50 F/R as possible. Front engine cars are typically in the region of 60/40, rear engine cars 40/60, and mid engine cars close to 50/50. You will see the top echelon of all motor racing disciplines are mid engine for this reason.
Sprung weight – this is the weight of the vehicle that is supported by the springs.
Unsprung weight – the weight of all of the components not supported by the springs. This will be the wheels, brakes, hubs and certain suspension components etc.
For an ideal car you need a low total weight, 50/50 weight distribution, and very low unsprung weight. If you imagine your hub/brake/wheel/tyre as a gyroscope, remember those gyroscope toys that were really hard to move quickly? Multiply that force by thousands and you’ll see one of the reasons why it’s important to have a low unsprung weight, and that is why ‘professional’ race cars use carbon brakes and magnesium wheels.
It’s also important to keep any weight you do have as low in the car as possible to help the centre of gravity. This is the hypothetical balance point of the car. In a typical front-engined production car the centre of gravity is just under (and forward of) the centre of the dashboard. If you can move this downwards and backwards the benefits to handling are huge.

So what would the ultimate handling Mustang look like in the mind of Spanner Monkey?
First off I would remove a huge amount of weight. Cut out anything not needed, remove all of the floorpan and monocoque chassis and build a complete lightweight tube-frame chassis which will save weight and add stiffness. Move the engine further back to improve the weight distribution.
One of the benefits of removing any compromise in construction is the ability to put the suspension mounts exactly where you need them for ultimate geometry. I’d build a car with twin front wishbone suspension using cantilever suspension and placing the (heavy) shocks and springs as close to the centre of the car as possible. Steering would be by rack-and-pinion.
Rear suspension-wise, surprisingly I would still use a solid axle, but have it supported by either 4-link and Panhard bar or 4-link and Watts link. Again the suspension would be by cantilever with inboard suspension.
With all of that done, the driver wold be positioned to best suit the weight distribution, and as low as possible to help the centre of gravity. All ancillaries (fuel tank and pump(s), exhausts, the majority of the wiring, battery etc., need to be positioned within the wheelbase. Pendular weight (such as putting a large fuel cell and battery behind the rear axle in the boot) is also a no-no.
All of the suspension joints would be rose-jointed (heim joints). Rubber or nolathane bushes are compliant enough to allow your suspension and steering to ‘move’ out of their set angles which is very detrimental to ultimate handling. In the case of standard rubber metalastic bushes this compliance can alter the track/camber by 10mm+. That’s why some production cars feel twitchy on the track even with uprated springs & shocks.
Interior-wise there would be no heater or aircon (both the units and the fluids they contain are weighty), no radio or speakers, minimal instrumentation, only 2 seats max, lightweight aluminium or carbon-fibre panelling, lightweight windows.
Powerplant, brakes, transmission and cooling will all be covered in later instalments…
Would it work? Yes. It’s a tried and tested recipe for a tight-handling track weapon, but I wouldn’t like to drive across America in it….
Please feel free to comment or ask questions.

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Re: Mustang Handling - Fact and Fiction

Postby badhand » Sat Apr 30, 2016 2:50 pm

Just re-reading this with an eye to applying some of your logic to my Hell Yeah II project. I really have the opportunity to put a lot of these tips into practice as I'm starting with an almost blank sheet.

I really wanted IRS, but now I've bought a lighter engine (Coyote 5.0) I have less to spend on other areas, so your words on a 5 link leaf spring set up are encouraging... And talking of engine, I have the chance to move that around a bit too I guess.

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Re: Mustang Handling - Fact and Fiction

Postby Spanner Monkey » Thu May 05, 2016 5:13 am

badhand wrote:Just re-reading this with an eye to applying some of your logic to my Hell Yeah II project. I really have the opportunity to put a lot of these tips into practice as I'm starting with an almost blank sheet.

I really wanted IRS, but now I've bought a lighter engine (Coyote 5.0) I have less to spend on other areas, so your words on a 5 link leaf spring set up are encouraging... And talking of engine, I have the chance to move that around a bit too I guess.


Don't be put off by using a live axle. Those that criticize the handling of cars fitted with live axles are doing so from a point of ignorance.

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Re: Mustang Handling - Fact and Fiction

Postby cati » Thu May 05, 2016 6:52 am

Mister monkey

I have my first adjustable suspension. Can you help me with rebound and damping and setting up front and rear

Do both settings need to be the same between front and rear

Is choppiness rebound of damping or both


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