Ohlins' Adjustable Coil-Over Kits Are In Stock At J&M / hotpart.com

[Norm Peterson]

It's expected from basic car setup charts that increasing front sway bar will add understeer. With the Mustang that is just not the case in fact adding more front bar (to some point) actually reduce understeer in the car you explained why very well but it something that most people that just start with setting up cars just find strange / not logical. But the reason is that the car just don't have enough spring for the weight.

Sometimes I think those charts get in the way as much as they help, as they tend to let people think in terms of "if this, then all you have to do is that". The average internet reader is not an engineer. So he isn't conditioned to ask questions like "why" and particularly "what else is related or involved here" when he's just starting to learn about something new. Never mind the matter of actually relating all those separate things to each other and to some expectation of car behavior.

If only people would do a little reading off of the internet, maybe starting with Fred Puhn's "How To Make Your Car Handle" (if it's still in print; my copy carries a 1976 date) and William Mathis' "Mustang Performance Handbook 2" just to get a basic introduction to how suspension things are inter-related.


Norm

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[Norm Peterson]

Thank you, Norm. I see. Originally, the spring rates that i was gunning for is 300-325lb/in. because I've heard it's kind of a sweet spot before the car goes intolerable. for street and it becomes dedicated to track-only kind of ride.

This gets into the matter of individual tolerance for a firm ride, and that you can get appropriate damping. IIRC, 350-ish is Steeda dual-rate territory. I haven't tried running any numbers to see how much different 350 would be from 250, all else held constant. But I doubt that roll or that the time to take a set would be reduced by much. It's what you'd do if you were competing in a class that required the use of OE-style springs, but it's more than you'd need for canyon running where you're going to be holding back at least a little. Less peaky/slightly slower breakaway is going to be your friend even more on the streets and through the canyons. That last tenth of a lat-g, not so much.

What do you think? IS 300-325lb/in seem to high? I guess coming from 160 stock spring rate to 250 is a good enough for a noncoilover setup which is close to or more less to the GT350 spring rate.

What I think is that you need to drive the car in whatever venue(s) the way it sits and let the car's behavior tell you what it needs - where you'd first fix what you most notice needs work.

I suppose you might want to go into that having decided whether you were going to follow the more traditional suspension development path where you first choose spring stiffness (and dampers) and do your fine-tuning with the bars, or some version of "big bar soft spring" where you'd work to reduce roll with adjustable bars as a priority over (say) nose dive under braking. You'd use bar adjustability to compensate for the springs you'd choose later being biased differently than OE.


Norm

 

[shogun32]

if you end up buying an adjustable rebound front strut, you can try the Steeda DR front springs. I have them. Feel fine 'in anger' but a bit annoying on highways and around town. I don't know how well say the Bilstein B6 would cope with the higher rate since the target spring rate is 200'ish.

If you want to try all manner of springs, then go with an adjustable coil-over. And you might as well spring for Ohlins or better. The Steeda (nee Koni) and Bilstein B16 ( 48-253901 ) are likely not valved to handle much over 350. Also the Bilstein don't appear to use standard 2.5" springs but rather a proprietary wind. Doesn't mean one can't fashion up an adapter though.

 

[bnightstar]

If only people would do a little reading off of the internet, maybe starting with Fred Puhn's "How To Make Your Car Handle" (if it's still in print; my copy carries a 1976 date) and William Mathis' "Mustang Performance Handbook 2" just to get a basic introduction to how suspension things are inter-related.


Norm

You think I didn't do enough reading :?
I agree but kind of like things like Tune to Win for example. I also agree that car setup is a bit more complex than it seams from the charts.

 

[DivineStrike]

Did you drive a 350/R around a track ? Even the R run springs that are good for the road and are more road than track. I work a lot with Kenny Brown (40 years of creating race cars) and his track cars with proven track wins use 800 lb front springs or more depending on track.

You are not seeing such rates on the cars here because people like you complain for street ability even from a 350 lb springs but that doesn't mean they are not used.

For example the Steeda #20 car is on MCS RR2 dumpers and is running more than 350 lb of front spring.

For daily drive car I could argue that you don't even need firmer springs the PP1 shocks and struts with good Front bar and great alignment is all you need in order to have an amazing canyon car that is super predictable and fun to drive in Mountain passes. I drive with bunch of Evo X's and I'm not slower than them in the corners and they say my car handles insane when pushed mostly because with my current setup I don't have under/oversteer which mean that car is perfectly balanced. Also GT spring rates are soft enough to be able to handle potholes good. Which in my 3rd world country is big deal. So you don't need to spend tons of money to have a reasonable daily driving Mustang you just need to step a bit out of the beaten path.

you also have to take into account tire size and compound when choosing your spring rates. If your using street tires and not r-comps or aggressive autocross tires, then 500 in/lbs will probably overload your tire prematurely. I could see your performance dropping instead of improving in that case. Which is why i chose 300 up front for mine, since I’m on mps4s’ and 285 width. Norm put an interesting perspective into why Jri and ohlins chose the setups they did. i will say I am curious to try a more aggressive front setup. Powering out of a corner with a softer rear would put more weight on the rear tires so maybe it’s better that way.

 

[bnightstar]

you also have to take into account tire size and compound when choosing your spring rates. If your using street tires and not r-comps or aggressive autocross tires, then 500 in/lbs will probably overload your tire prematurely. I could see your performance dropping instead of improving in that case. Which is why i chose 300 up front for mine, since I’m on mps4s’ and 285 width. Norm put an interesting perspective into why Jri and ohlins chose the setups they did. i will say I am curious to try a more aggressive front setup. Powering out of a corner with a softer rear would put more weight on the rear tires so maybe it’s better that way.

I currently drive on 275/35 140TW (Soft) Semi-Slicks tires on the track and plan to go with Ohlins + Apex SM-10 + 295/30 (Medium) 240TW Semi-Slicks so yeah I do need extra spring rate. Installing Steeda Front Bar (520 lbs) did help a bit with the body roll but car still unload the inner tire during cornering which mean I'm losing grip. Soft rear helps power out that's for sure you need your rear to be as soft as possible without understeer. Obviously dialling a Suspension is not exactly simple task as you need tire temps, good driver that can feel what the car is doing and tools on the track to dial the perfect setup.

 

[Norm Peterson]

You think I didn't do enough reading :?

It's never clear what most other people have read or where they read it. Or (these days) if it was only something they picked up from some youtube video. There's a few people like Brian@BMVK here and elsewhere who have obviously put some serious study time into this stuff . . . and everybody else.

I agree but kind of like things like Tune to Win for example. I also agree that car setup is a bit more complex than it seams from the charts.

If car setup was easy - and more importantly if it didn't inherently involve compromises that aren't going to be the same for everybody - threads like this probably wouldn't even exist.

FWIW, the impression I get from reading 'Tune to Win' was that while it does a good job of identifying and describing concepts, it could have done a better job at tying them all together.


Norm

 

[TeeLew]

not sure I subscribe to that. rebound valving is generally linear and pretty heavy compared to comp which may have an initial curve similar to rebound but after say 4"/sec blows off.

Steeda claims their DR "are good on the street". We differ on that definition. Livable, sure. Good, no. On track they may be brilliant. TBD. They also said the Pro-Active+progressive springs was a good combo. Solidly 'nyet' in my book.

I only bring it up to suggest guys who tune race cars for track use seem to have a rather distorted view of what is ok/good on the street. If you talk to the Hotpart guys they don't agree with Ohlins default choices either and have personal experience to back up their opinion. Feel is somewhat subjective.

I personally would start with a 250-275/950-1000 combo and also buy a front 325 or 350 if you want to experiment.

For dedicated autocross/road course work the 500+ fronts may be perfect. But that use case and desired chassis pitch characteristics is wildly different from casual corner carving on public roads at less than 80mph.

As a simple comparison my SS/1LE runs ~170lb/in springs up front and handles better than the Mustang. It has MR shocks to contribute to control chassis pitch so it's not just the spring. I am of the opinion that vehicles are SUPPOSED to tilt and shift weight around as long as it isn't excessive to the point of dragging body parts or taking too much weight off the opposite corner and compromise traction and control. Other people can't abide a car that moves on it's axis.

As far as the compression/rebound split, don't try to derive a 'should' from an 'is'. I believe most people use (over use, to be specific) rebound because it's easy to feel, not because it's the best tool for grip or to shift balance.

I'm right at the spring rates you mention 220# front with a spring rubber, (so probably ~275#) and a 950# rear. I'm dropping the rear rate because it's too loose when I Auto-X. On the street it's OK, because I pull the camber out of the front, but when the front is working well, I need better powerdown performance. The fact that the surface I compete on is both rough and slick probably plays into my evaluation, but so be it.

On the street, my car is OK, but I feel a little softer rear will be an advantage all-around just for the added compliance. I completely agree a car with a decent suspension geometry should be allowed to move a bit. It's better for grip, tire life and balance consistency through the corner. The Camaro rates reinforce that opinion.

 

[Norm Peterson]

I'm right at the spring rates you mention 220# front with a spring rubber, (so probably ~275#) and a 950# rear. I'm dropping the rear rate because it's too loose when I Auto-X. On the street it's OK, because I pull the camber out of the front, but when the front is working well, I need better powerdown performance. The fact that the surface I compete on is both rough and slick probably plays into my evaluation, but so be it.

Autocross is typically 2nd gear. Do you suspect that you'd still have the same concerns in 3rd gear or higher on a road course? Or would not having as much rear "axle" torque be enough to rein in the on-throttle looseness?


Norm

 

[TeeLew]

Autocross is typically 2nd gear. Do you suspect that you'd still have the same concerns in 3rd gear or higher on a road course? Or would not having as much rear "axle" torque be enough to rein in the on-throttle looseness?


Norm

Good question. I've thought about this one for quite a while and I don't know that I can say one way or another.

The Test/Tune day I just did was all second gear, but the SCCA stuff often has a quicker, lowish 3rd gear corner thrown in, but even then, it's not really fair. Auto-X stuff is point & squirt with everything being shorter duration, so you don't really get the opportunity to have the car rolled over with lateral load for any extended period of time.

I will say this, and it may be a function of the surface I'm on, but the loaded rear tire never really seems to dig into the pavement. It feels like it's always skating across the top of the pavement. When I do overstep the grip, it's a pretty good slide before it recovers. I don't feel any difficulty getting the car to respond to transitions and the chassis motion (either roll or squat) seems relatively small. These things all put together indicate to me that I'm a little too stiff. Keep in mind, I could be entirely wrong. I do a lot of work on cars, but I don't do a lot of driving, so I could easily be reading this wrong.

As far as being in low gears and chasing the rear because of having ample 'axle (drive?) torque', I have to think it's at least part of what I feel. Auto-X on relatively cold 200TW tires is kind of an odd-ball application which could put me in a different direction than if I were on a racetrack, particularly if I were on semi-slicks and the track was rubbered in. It's also going to be influenced by how I drive. I make a concerted effort to load the front of the car at corner entry and _not_ carry a lot of mid-corner speed. I'm always fastest if I take a couple mph off the potential mid-corner rolling speed to gain the ability to turn the car and apply (full) throttle early. This means I'm challenging the rear on entry and exit. If I get it under me in those two areas as I like, I almost always end up with some U/S mid-corner. It's just part of my compromise.

How's that for a long-winded non-answer?

 

[guitrflip]

I'm right at the spring rates you mention 220# front with a spring rubber, (so probably ~275#) and a 950# rear. I'm dropping the rear rate because it's too loose when I Auto-X. On the street it's OK, because I pull the camber out of the front, but when the front is working well, I need better powerdown performance. The fact that the surface I compete on is both rough and slick probably plays into my evaluation, but so be it.

Someone brought it up back on 2016-2017. It appears the reviews of people are very positive and content enough that it's no longer mentioned as much as today.

It's become apparent to me that maybe you should look into Swift R Spec Springs... After reading up different suspension setup (BMR, Steeda, and FP noncoilver setups), I found Swift Springs appear to fit the bill for people looking for the best of both world performance and OE feel.

Front Spring Rate: ~280lb/in (1.1 in drop)
Rear Spring Rate: ~784lb/in (1.0 in drop

If I'm understanding correctly, the rear should have a softer setup for better grip upon acceleration of exit corner. I'm assuming this is how our S550 chassis are developed.

Is it possible the Japanese company is on to something?

 

[TeeLew]

I've got the Maier adjustable rear spring perches, so I'm on standard racing springs (for the rear) as opposed to automotive ones. 800 #/in Hyperco's are being ordered today. I'm also getting the Hyperco hydraulic spring perches to try to address the misalignment as the suspension goes through it's motion. The Maier kit uses a large monoball on the bottom to assist in alignment, but I'm going to try to keep things happy on both ends of the spring.

 

[guitrflip]

800 #/in Hyperco's are being ordered today

Well excuse me, sorry for my ill-advise.
That's the next level shit! End-game suspension!
Excited for ya! Let us know how they feel. Hyperco is the real deal!

 

[TeeLew]

It's all good.

 

[bnightstar]

To continue the topic of Ohlins mine finally arrived in the OEM rates 504 lbs F/800 lbs R.
Need to find time to install them but overall that's one really good looking set of coilovers.

Still need to order adjustable endlinks and IRS base pack from Steeda in order to not drop the rear subframe twice but overall should be great ones everything is installed as it should be.

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