suspension mechanics, based on other cars?

[torinalth]

ok, so this is a rather odd question. In theory, based on physics, a spring is just like any other spring. it may be progressive or linear, it may be harder or softer, and it may have different physical dimensions (height, width, etc). Same basic principle would also apply to struts, correct?

 

With that said, is there a way to take a suspension setup from one car, with known parameters (spring rates, car weight, etc) that has your ideal feel, and then run the numbers to figure out what parameters the the suspension would have to be to have the same feel on a different car?

 

make sense? in short, I had a mustang GT, LOVED the suspension setup I had, feel was perfect balance of firm and comfort. can I equate the same feel on the LGT because the specs for the mustang are known?

 

edit: for some prelim information - 02 mustang GT, Bilstein HD struts, HR Race springs.

 

T

[BAC5.2]

Not directly correlate, but partially.

 

You COULD correlate valving to motion ratio of the Mustang, then apply the same principle to get the right valving for the LGT. Same with the springs.

 

However, it's unlikely that Bilstein will custom valve you a set of HD's, and you'll have to pay for custom springs. And even then, there is a LOT more at work than just motion ratios. It's all geometry based. Much more work than you'd want to do.

[torinalth]

I think you are going a bit more extreme then I am wanting to go

 

while it would rock to get a set of custom valved coilovers to replicate my old GTs setup, thats a bit more money then I want to spend.

 

on a more realistic setup, I was essentially trying to find what would give me the closest match so I dont have to do what so many others do.... rebuying parts because the first attempt didnt do what you wanted it to.

 

plus I think just about everyone that mods a carhas probably said "I wish I could make this car like my old XXXXXX...." if we could get closer to what we want instead of a shot in the dark, it would be helpful, thats all.

 

T

[m sprank]

It doesn't work that way.

 

Far more complex. Not just what strut and spring.

 

If you like a Mustang GT's ride get a Camry.

[Norm Peterson]

With that said, is there a way to take a suspension setup from one car, with known parameters (spring rates, car weight, etc) that has your ideal feel, and then run the numbers to figure out what parameters the the suspension would have to be to have the same feel on a different car?

Same ballpark if the cars are of generally similar configuration, maybe. But there's so much more to this than springs, struts, and sta-bars. You can match ride frequencies and flat ride pitch behavior and it still won't necessarily feel the same or drive anywhere near the same.

 

But if you want an introduction to this stuff, hunt down a copy of Fred Puhn's book "How To Make Your Car Handle". Ignore such detail as the tables of specs for cars that have been out of production for decades and concentrate on the concepts and formulas. The next step above the $20 softcover Borders/Barnes&Noble level will cost ~$100 and will be found at the SAE bookstore.

 

I am definitely curious as to what it is about your '02 Mustang that makes it rate so high on your list. Rear suspension geometry and compliances in that car leave a lot to be desired in anything harder than moderate street driving. My '79 Chevy Malibu is cursed with the same rear suspension layout as the Fox/SN95/New Edge, right down to the rear sta-bar being connected to the lower trailing arms and nothing else (UCA angles and rear spring lower seat locations are the only real differences). The converging/triangulated 4-link can be band-aided, but only so far . . .

 

 

BAC - I think there is an outfit that will revalve Bilsteins, though I don't know what you'd have to go through to get the valving for a completely new application set to where you'd want it. Sam Strano may know more about this (Stranoparts isn't just a Mustang/F-body source - he sells a few things for the STi and WRX and a few other cars that are popular within the autocross community).

 

 

m - you really need to drive a current generation Mustang GT, preferably one with Koni yellows fitted (the OE rear shocks' high speed rear bump damping is kind of harsh). Any 2005 - 2010 will do, since the ride & handling balance is separate from the new car's 400+ HP 5.0 that has all the magazines excited. If Camrys felt half as good to drive, Toyota would be justified in suing Nissan for ownership of the "4 door sports car" tagline.

 

 

Norm

[BAC5.2]

I think you are going a bit more extreme then I am wanting to go

 

while it would rock to get a set of custom valved coilovers to replicate my old GTs setup, thats a bit more money then I want to spend.

 

on a more realistic setup, I was essentially trying to find what would give me the closest match so I dont have to do what so many others do.... rebuying parts because the first attempt didnt do what you wanted it to.

 

plus I think just about everyone that mods a carhas probably said "I wish I could make this car like my old XXXXXX...." if we could get closer to what we want instead of a shot in the dark, it would be helpful, thats all.

 

T

 

It's actually much more complicated than I mentioned.

 

Suspension design is not for the feint of heart. I've designed front and rear suspensions for a few different applications and it's not as cut-and-dry to translate from one design to another. It is actually extremely difficult to do that kind of thing, to the point where I doubt it could be done reliably.

 

If you want it to ride like your Mustang... get another Mustang. I'd focus your energy on getting it to ride as well as possible. That will at least see some return. You'll always fall short trying to get it to ride exactly like your Mustang did.

[devobuzz]

The best thing to do is get a ride in other Legacy's with different suspension setups. Pick the one you like best!

[torinalth]

I think several of you are completely misreading my situation. I am not looking for the LGT to HANDLE like the Mustang, if nothing else the RWD/vs AWD alone would make that impossible..... its all about the ride quality.

 

why: for whatever reason the combination of the Bilstein HD struts, and the HR race springs have the ideal setup for a DD feel. improved handling a lot, but the ride was firm, not jarring, not bouncy, not irritation. it made an improvement and didn't degrade the ride quality. reminded me of a BMW suspension, firm but not aggrivating.

 

but seeing as this is an impossible endeavor we can let the thread die here.

[BAC5.2]

You can definitely get AWD cars to handle like a RWD car. That's all about alignment. Handling and performing are different, an AWD car that handles like a RWD car will always be faster than that RWD car.

 

I'd find some locals, ride in their cars, and see what you like the best!

[Norm Peterson]

I think several of you are completely misreading my situation. I am not looking for the LGT to HANDLE like the Mustang, if nothing else the RWD/vs AWD alone would make that impossible..... its all about the ride quality.

Via the internet it is sometimes difficult to pick up exactly what the intended objective really is and what compromises might be acceptable. Sometimes it's difficult to straight-away even express what that objective is. For example, the term 'feel' can be interpreted to be associated with either ride quality or handling, and the tendency for most of the "regulars" in suspension fora (not just this one) is to assume that handling has some priority. IOW, it may take a bit of back and forth discussion to home in on it rather than the initial question directly lending itself to some "canned answer".

 

 

In any event for this particular subject, I don't think it's wise to focus on only one "side" of things here. . . . . . Just to fire a not-so-rather-odd question back, suppose you could duplicate the ride quality almost exactly, but doing so sent the handling into the toilet. Then what?

 

(I'm not saying that's the way it would be, just asking how happy you'd be if you chose to ignore the handling side of the equation and it actually did turn out that way.)

 

 

Norm

[torinalth]

BAC: yes I am familiar with getting an AWD to have similar tendencies as a RWD car, but just like you said, even when setup to "perform the same" the AWD car will out perform due to the extra traction. but that is not quite the direction I had intended this thread to go.

 

Norm: Yes, you are right it does make it difficult to get things across properly on a forum. as far as the question you posed of "if the ride is what you wanted but the handling then went down the drain" well, yes, that would be epic failure on my end then

 

knowing this is a performance oriented forum (as is any forum that deal with modifications) I was expecting (perhapse my failing on this one) that I could get the answer based on mechanics not perception (hence the whole spring rate vs car weight, etc)..... with that being done by those that are like minded in the desire to have the best car possible (why would anyone want to make it worse intentionally), I figured that if I got my answer to how to make the car ride just like my GT did all the possible routes that took the handling into the toilet would either be left out or would be noted as "this will get you there, but something else will suffer for it".

 

perhaps I was a bit to narrow in my original setup for the scenario, or maybe just misunderstood... disregard that the mustang was an american car (blah blah, american cars cant handle).... that car rode perfect. firm and poised, NO bounce, ever.... not harsh at all, even under bad road conditions.... it was almost ironic that it felt that good considering it was american, and that all I did was springs and struts (did more, but that was all that would affect the ride alone)

 

now, the feeling of perfection for me would undoubtedly be considered too soft by some, and too form by others... hence why I was attempting to remove the "feel" from the equation and focus simply on numbers and physics.

 

What I was hoping for would have been, since the GT had XXXX figures, that would translate into XXXX figures on the LGT. ok, since no single shocks fit that bill the adjustable Koni's would would have that figure fall within its range. the translated spring rate for the LGT would be X front and Y rear. take into consideration the different weight distribution of the LGT and the Swift springs would be the closest match for the front spring rates, while the rallitek would match the rear.... either would get you as close as possible without going custom.

 

I knew it would not be a simple answer known by all (or I wouldnt need to ask the question), but figured someone would have some insight on what would need to be looked at.

 

I mean, granted its not common knowledge, but there HAS to be some formula of X rate, with Y travel supporting Z weight has a sprung value of R. spring value of R supporting Z weight of the LGT and a travel range of the LGTs Y would requite a spring rate of X for the LGT. with the spring rate of X for the LGT you would need * dampening value to support it properly.

 

I know geting exact is going to be custom and way to expensive, I just wanna get as close as possible considering the options for the LGT.

 

T

[m sprank]

None of your equations work. Change the wheels and its all screwed up. No way to factor in unsprung weight. It is an unknown. Its not just weight of car. Its weight of everything involved.

 

Plus, most members here dont mix and match spring sets. It only happens when we get into coil overs. Even then most members accept whatever the manufacturer gives them. Heck I complained about my springs and requested a different set up. What did I get? 4 months with almost no reply's to my requests. Emails telling me my options, but no response to accepting payment. COLD SHOULDER for complaining about spring rates and asking to BUY new springs.

[Norm Peterson]

tor - seems I can't either think fast enough or type fast enough today.

 

I suggest picking springs based on front and rear ride frequncies and pitch behavior including some effect for damping. Formulas exist, and they aren't all that difficult to use if you have a mind for such things. It's up to you to choose ride frequencies that you think that you can live with (1.0 Hz is pretty soft, 2.0 Hz is probably too stiff) and the range of speeds that you want the front and rear frequencies to be more or less "in sync" rather than "out of phase". Out of phase = think 1950's-era pickup truck with dead shocks and nothing in the bed.

 

Then correct (or make) any handling changes via stiffer or softer sta-bars and live with any ride deterioration over one-wheel bumps. There are formulas for determining the distribution of lateral load transfer (please don't call it "weight transfer") as well. About 5% more LLT up front than there is front weight percent is commonly used elsewhere, but you might want a slightly different percentage where AWD is involved.

 

 

You can find most of this stuff in Puhn's book, except for the mathematical treatment of damping with respect to ride frequencies (which is a fairly minor effect until you start cranking in LOTS of damping).

 

 

Norm

[BAC5.2]

I mean, granted its not common knowledge, but there HAS to be some formula of X rate, with Y travel supporting Z weight has a sprung value of R. spring value of R supporting Z weight of the LGT and a travel range of the LGTs Y would requite a spring rate of X for the LGT. with the spring rate of X for the LGT you would need * dampening value to support it properly.

 

So you no longer want to make your LGT ride like your Mustang? There isn't a translational formula for the LGT -> Mustang.

 

You are over simplifying things. You aren't accounting for things like unsprung weight or suspension geometry differences, let alone damping scenarios (high vs. low speed). Plus, Z changes as a function of ride height, which is dependent on spring rate.

 

I think your best bet is to ride in friends cars, see how you like it, then mimic that setup.

[torinalth]

M Sprank: they were a basic layout for what crossed my mind, nothing accurate (or real for that matter) by any stretch of the imagination. I think Norm hit on closer to what I was kicking around in my head with the frequency. I know all too well about the issues with getting specific items that do not match the norm when it comes to dealing with retailers. had the same issues with the mustang till I found Maximum motorsports who live for that kind of stuff... alas, they have no desire to work with anything other then mustangs.

 

Norm: interesting information. that sounds like what I need to look into so I may end up grabbing that book and seeing what I can glean from it. Not trying to reinvent the wheel here, just save myself from making a purchase, hating it, and spending the same money again.

 

BAC: untrue. I still want to get the same ride quality that my mustang had. handling is a different issue, but the feel of the every day movement when on the highway, taking bumps, etc is what I am trying to replicate.

 

and yes, I AM over simplifying things since I dont know at this point what other questions I need to answer to limp me along to my final goal. you are right that riding with other people would be the easiest route. the issue is that the only local ones I know have imprezas, which are not identical. any Legacy or OB I find local are all old people owned and are stock. I'll keep looking for people while I think about the outcome.

 

In the end I may just end up saying screw it and get koni's with rallitek springs.... I just dont want to buy something and then remove it within a week like I did with my Ksport pro coilovers I had on my WRX.

 

I do appreciate all the input, though it does seem to have gotten a little convoluted in the various posts.

 

T

[BAC5.2]

I only asked because your "formula" didn't mention anything about the Mustang.

 

If you are dead set on trying to figure out some correlation between different vehicles suspensions, then start riding with Imprezas. The 08+ Imprezas have a lot more in common with our cars than the Mustang GT.

 

Keep in mind that you'll need scales, a tape measure, and a lot of patience if you want to actually try and go about this.

 

I think you'll find, if you read some books on suspension design, that what you want is pretty difficult, if not impossible, to obtain.