Challenger SRT8 vs Mustang Bullitt

[Sigma Projects]

Well, for what most people do with their mustangs, IRS would actually be better.  Lighter, better handling, and better everyday performance.

A better tuned SRA will be better than a crappy tuned IRS, of course a really good tuned IRS will do wonders, but from what I heard FMC didn't do well enough while figuring out an IRS setup and found the SRA in the mustang to be the best cost/performance design. But how is the IRS lighter than the SRA? In the celicas of my generation the weight difference between a SRA and a IRS is about 140lbs, it's part of the reason why I went for the SRA in the 3rd gen celicas. Same goes for the Cobra and the GT from the last gen mustang. An IRS setup is great when done right, but for lower cost, more robust and lighter SRA is the choice and I'm sure FMC wanted to keep the mustang price low.

[hounddog]

You have obviously never driven a 2005+ Mustang because if you had you would know that they handle and ride better then the Terminator Cobras do with an IRS.  I've driven Mustang from all generations and the 2005+ is the best by far, even better then the Terminators.

Actually, I have.  I drove a 2007 gt convertible.  It was ok, but it seemed a little blah when I ran it through some curves, it felt almost exactly like a Crown Victoria. 

Oh and by the way, Terminator Cobras shred their transaxles at the track all the time and many of them replace the IRS with a solid axle.  It's a popular conversion for Terminators that are used at the track on a regular basis.

Well, those are not "everyday Joes" now are they?  As for they handle and ride better bit, overall the car might handle better but it is a different car.  Put the IRS on the back and it WILL handle better, which is why the great handling cars of the world use IRS instead of the stodgy old SLA.  And, put the SLA on a bumpy road and you WILL get axle hop. 

Sure, Ford tried to dampen it with five link Watts, and huge sway bars but in the end it still suffers from the age old problems they have always suffered.

[hounddog]

An IRS setup is great when done right, but for lower cost, more robust and lighter SRA is the choice and I'm sure FMC wanted to keep the mustang price low.

This is the reason Ford opted not to use it, mostly it was cost.  They simply did not have the cash to put into the R&D, and have all but admitted to that.

[SVT666]

Actually, I have.  I drove a 2007 gt convertible.  It was ok, but it seemed a little blah when I ran it through some curves, it felt almost exactly like a Crown Victoria. 
Well, those are not "everyday Joes" now are they?  As for they handle and ride better bit, overall the car might handle better but it is a different car.  Put the IRS on the back and it WILL handle better, which is why the great handling cars of the world use IRS instead of the stodgy old SLA.  And, put the SLA on a bumpy road and you WILL get axle hop. 

Actually axle hop is what you get in a Porsche 911 at launch.  Hitting a bump in mid corner with a Mustang GT is no worse then hitting a bump in a stifly sprung sports car.  Is it perfect?  Aboslutely not.  The IRS in the Terminators was a terrible setup and the current car handles and rides much better.  Most people could never tell the difference.

Ford has done a marvelous job with the current live axle in the Mustang, and IRS is coming in the near future and I've got nothing against that.  I just hate how people use words like stodgy, archaic, etc. when describing things like live axles (that work just fine) and pushrods engines.

[hounddog]

I love pushrod engines.  The HEMI has high rpm range, and acts like a DOHC.  I wish they put it in boats!

And, I am sorry to disagree with you, but SLA is stodgy and archaic.  There is a far far far better suspensions out there, the IRS.  A marvelous SLA setup is still behind a merely good IRS setup.

[280Z Turbo]

Solid rear axles work okay, it's the truck style axles that use leaf springs to locate the axle that are the problem. Modern setups use multilink panhard or Watts linkage setups.

Many racecars use solid axles. Mazda's RX-7 had (and still has) a lot of racing success despite the solid rear axle.

It's not better than IRS and it's less than ideal, but it can be made to work well.

[Sigma Projects]

I don't think any mustang came stock with a watts link, that would be really cool. I want to install one on my celica in the near future.

I think it's an over statement that a marvelous SRA is behind a good IRS setup especially in smaller application. This is what should go into a CR Mustang if they were ever to make one



the shaw link for the older mustangs is just bad ass.

[SVT666]

I don't think any mustang came stock with a watts link, that would be really cool. I want to install one on my celica in the near future.

You're right it never came with a Watts link.  It comes with a panhard bar instead.  The Watts link is far better at doign the job and can be bought through any number of suppliers including Saleen.

[SVT666]

I love pushrod engines.  The HEMI has high rpm range, and acts like a DOHC.  I wish they put it in boats!

The HEMI redlines at 5700 rpm.  I have seen aftermarket tuners that get it up to 6800 or so, but that's really getting up there for that engine.

And, I am sorry to disagree with you, but SLA is stodgy and archaic.  There is a far far far better suspensions out there, the IRS.  A marvelous SLA setup is still behind a merely good IRS setup.

That's simply not true.  The SLA in the Mustang GT is a very good setup, but to make it marvelous one must buy a Watts or Saleen Link for it and that setup works absolute wonders with the live axle.  Just look at how the racing Mustangs kick ass every weekend in road racing events around the world.

[JYODER240]

On a racetrack it's not going to make much of a difference if the car has IRS or SRA, atleast in theory. The problem with SRA is that it resists allowing the wheels to move indepentantly of each other. It will act similarly to a sway bar. A car that has IRS and extremely stiff sway bars will handle similar to a SRA in that the car will get upset when either only one side of the car hits a bump and it transfers it to the other side or when the car hits a bump mid corner and it upsets the cars composure. On a smooth racetrack a SRA shouldn't have any handling disadvantages over an IRS. The problem with SRA comes up in that none of us drive on smooth bump free roads.

[Nethead]

This is the reason Ford opted not to use it, mostly it was cost.  They simply did not have the cash to put into the R&D, and have all but admitted to that.

DogDude:  Mostly true.  They put the cash into IRS R&D for the Mustang years ago and came up with one that could generate around 1.1 G on all-season radials, and much more on track rubber .  The coil-overs were mounted horizontally above the differential and its two axles, with the upper and lower A-arms transmitting the compression to the coil-overs by forged aluminum "L-shaped" items.  They had a tech term for these "L-shaped" items but I can't recall it (Update:  Good googling found that tech term used to describe these suspension bits: "bell cranks").  There were pivots at the top of the "L" and at both ends of the bottom of the "L".  The top pivots connected to the coil-overs, the inner bottom pivots connected to the body/frame, and the outer bottom pivots connected to the lower A-arms or to the bottoms of the hubs.  There was a second, developmental version--significantly lighter--that replaced the upper A-arms with a single swaybar connecting the tops of the left and right hubs.  The "regular" version was terrific, but it was costly and required a transverse "hump" across the trunk to clear the coil-overs, and to clear the upper A-arms at high spring compression.  This had a detrimental effect upon the cargo area, naturally--and ended all hope of a flat cargo space with the rear seats folded down.  The utility of the flat cargo space with the rear seats folded down was an amenity that Ford would not forsake for IRS as the 60/40 fold-down rear seats are a high value item to the great majority of Mustang customers. In a vehicle with the massive cargo volume of a Crown Vic, that "hump" would make only a minor difference in trunk capacity, but we ain't talkin' Crown Vic cargo volume in a Mustang...

The Ford GT IRS is splendid, too, but that may require extending the rear wheel tubs further inwards to clear all suspension components, resulting in a different version of the same problem--restricted cargo volume. But this would presumably leave the cargo floor flat--although narrowed considerably by the extended rear wheel tubs.  This sounds like the way to go to the Nethead here, but mock-ups should be shown to lots of younger Mustang owners to see how they feel about the narrowed cargo area when the rear seats are folded down.  I say "younger" owners because they're the ones far more likely not to have second vehicles with bigger cargo capacities--and thus the ones who would have to pass on a Mustang if the cargo area is insufficient for their needs. 

But it ain't up to the Nethead here to decide, and we haven't gotten the word from those who will...

[FoMoJo]

A better tuned SRA will be better than a crappy tuned IRS, of course a really good tuned IRS will do wonders, but from what I heard FMC didn't do well enough while figuring out an IRS setup and found the SRA in the mustang to be the best cost/performance design. But how is the IRS lighter than the SRA? In the celicas of my generation the weight difference between a SRA and a IRS is about 140lbs, it's part of the reason why I went for the SRA in the 3rd gen celicas. Same goes for the Cobra and the GT from the last gen mustang. An IRS setup is great when done right, but for lower cost, more robust and lighter SRA is the choice and I'm sure FMC wanted to keep the mustang price low.

Unsprung weight is lighter which may be the greatest advantage of IRS.  Axle hop can easily be resolved on both IRS and live axles if needed.

[SJ_GTI]

Motivemag.com did a comparison (sort of) between the GT500 and Challenger SRT8.

http://www.motivemag.com/pub/feature/versus/Motive_Versus_Dodge_Challenger_SRT8_versus_Ford_Shelby_GT500.shtml

No instrumented testing, but they did get to thrash them both a bit side by side:



Their conclusion:

So, to sum up: The Challenger has a more advanced suspension, superior ride, incredible brakes, a more gratifying engine, a better-crafted interior, and posts similar numbers. The Mustang is more adrenal, currently has better steering, and can play the guitar solo to Stairway to Heaven while administering a roundhouse kick to your face. The GT500 is rough and raw, while the SRT8 is a very powerful, very competent cruiser. This test has turned out to be a fair illustration of the differences between a muscle car based on an intermediate body and one based on a pony-car platform. If you want a high-strung, nine-testicled pet, get a GT500; if you want a chilled-out muscle car you can drive everyday, put your name on the Challenger waiting list.

[SVT666]

That picture makes both cars look so damn muscular and downright frightening.  I would take the GT500, but if the Challenger had a manual tranny then that's the car I would park in my driveway.

[FoMoJo]

The GT500, on the other hand, rides on front struts and a live rear end, and it's about as stable and behaved as a crack-smoking monkey. Driving it provokes alternating fits of abject terror and uncontrolled giggling, and it takes a sure hand to control. Go in to a turn with too much throttle, and you'd damn well better commit, stay in it, and let the rear end do the turning for you.


Sounds like my kind of car .

[SVT666]

The GT500, on the other hand, rides on front struts and a live rear end, and it's about as stable and behaved as a crack-smoking monkey. Driving it provokes alternating fits of abject terror and uncontrolled giggling, and it takes a sure hand to control. Go in to a turn with too much throttle, and you'd damn well better commit, stay in it, and let the rear end do the turning for you.


Sounds like my kind of car .

Me too, although every other magazine says it's extremely predictable and very well behaved.

[280Z Turbo]

The HEMI redlines at 5700 rpm.  I have seen aftermarket tuners that get it up to 6800 or so, but that's really getting up there for that engine.
That's simply not true.  The SLA in the Mustang GT is a very good setup, but to make it marvelous one must buy a Watts or Saleen Link for it and that setup works absolute wonders with the live axle.  Just look at how the racing Mustangs kick ass every weekend in road racing events around the world.

I think there may be a problem with adjustability though. We scrapped the Watts linkage for a panhard setup on our Mazda RX-7 racecar.

[FoMoJo]

Me too, although every other magazine says it's extremely predictable and very well behaved.

In the next paragraph they say...The Shelby is chuckable in the extreme. It's lighter and tighter than the SRT8, and it maintains that impression even in the presence of heavier control feel. The steering is firm and progressive, and you never have to make annoying, minute corrections mid-corner.

It almost contradicts what was said before.

[SVT666]

In the next paragraph they say...The Shelby is chuckable in the extreme. It's lighter and tighter than the SRT8, and it maintains that impression even in the presence of heavier control feel. The steering is firm and progressive, and you never have to make annoying, minute corrections mid-corner.

It almost contradicts what was said before.

Actually it doesn't almost contradict the previous paragraph, it does contradict it.

[ChrisV]

The problem with SRA comes up in that none of us drive on smooth bump free roads.

The other problem is that none of us should be driving FAST enough to notice the difference on the roads we do drive on.

Those of us that drive on the track, and don't drive at track speeds on the street, don't seem to have a problem with it. My Fiat Spider was live axle, and it handled just fine on the street.

OTOH, I have pushed cars hard on the street, too, and have found that even independant setups can skitter over bumps, both rear AND front suspensions, especially as you get suspensions modified to maximize cornering forces.

Basically, it's not a deal breaker for me. I've driven the new Mustang and the suspension felt fine.

[Nethead]

I don't think any mustang came stock with a watts link, that would be really cool. I want to install one on my celica in the near future.

I think it's an over statement that a marvelous SRA is behind a good IRS setup especially in smaller application. This is what should go into a CR Mustang if they were ever to make one



the shaw link for the older mustangs is just bad ass.

Sigma Projects:  SigmaDude, the shaw linkage photo is intriguing, to say the least!  Are there blogs telling how it actually performed in practice?  Preferably, blogs by some party or parties not involved in the manufacture and/or sale of shaw linkage kits, for obvious reasons!

Yet another profoundly informative posting by SigmaDude!  Good work, Sig

[JYODER240]

The other problem is that none of us should be driving FAST enough to notice the difference on the roads we do drive on.

Guilty. But to be the fair I only push it that hard on corners where I can clearly see what's coming and there's nothing else around but open fields.

On the Mustang though I noticed it getting nervous and I wasn't near track speeds. Some of the roads here are pretty bad.

[nickdrinkwater]

I guess they chose the Bullitt because it and the SRT8 are both flavour of the month.

[Schadenfreude]

If I remember correctly, wasn't the current Mustang designed so it could fit either an IRS or a SRA?  I could've sworn I remember read something somewhere about Ford having one of each in development, but I could be wrong.

[Sigma Projects]

thanks nethead, I don't hear much about it, but it's from ConTex, I found it on this review. http://www.mustang50magazine.com/howto/15419_contex_ultra_sport_suspension_system/index.html

I was searching for it since Mustangs do a lot of road racing and have a SRA, so I was looking around for ideas for my celica. Not sure how many people will get this kind of setup since it it's really for the track, this for sure wouldn't be comfortable on bumpy roads. But the article said that on the track it's more comfortable than the traditional ultra stiff suspension.

FoMoJo: Oh ok, yea IRS would have less unsprung weight, just when he said IRSs are lighter than SRAs, that's why I responded since SRAs can be lighter by 100~150lbs in the overall assembly.

[Sigma Projects]

just incase someone doesn't quite understand why a watts link is superior to a Panhard bar it's that a watts link it eliminates the scrubbing action that occurs with a Panhard bar and creates a better center axis for the rear axle to twist on.



http://www.youtube.com/watch?v=-J4xkHuP7QY

[r0tor]

But how is the IRS lighter than the SRA? In the celicas of my generation the weight difference between a SRA and a IRS is about 140lbs, it's part of the reason why I went for the SRA in the 3rd gen celicas.

i believe your research failed and didn't include 100% of the SRA is unsprung weight, the enemy of a good suspension

[Soup DeVille]

i believe your research failed and didn't include 100% of the SRA is unsprung weight, the enemy of a good suspension

So horrible in fact, that Colin Chapman abandoned the original DeDion tube suspension on the Lotus 7 and upgraded it to a live axle...

[Sigma Projects]

i believe your research failed and didn't include 100% of the SRA is unsprung weight, the enemy of a good suspension

thanks for pointing out something that I corrected myself in my last post addressing FoMoJo saying "Oh ok, yea IRS would have less unsprung weight, just when he said IRSs are lighter than SRAs, that's why I responded since SRAs can be lighter by 100~150lbs in the overall assembly." =P

[omicron]

If I remember correctly, wasn't the current Mustang designed so it could fit either an IRS or a SRA?  I could've sworn I remember read something somewhere about Ford having one of each in development, but I could be wrong.

Engineers are like that; a bit of an undisciplined rabble.