| Author |
Message |
Philip Airey (Pma1010)
Junior Member
Username: Pma1010
Post Number: 85
Registered: 7-2002
| | Posted on Friday, January 10, 2003 - 3:55 pm: | |
All
To close this chapter. The rear bars on the 308QV and 328 "B's" are 15 mm producing (I am told) a torque of 105.7 (ft) lbs at the attachment point/end link. The 18 mm rear bar on the "S" produces a torque of 210 (ft) lbs. I am having a custom 16mm 2 bolt adjustable sway bar built with a soft setting of close to 106 lbs and a hard setting of 173 lbs with rod ends to affix to the a-arms.
Second, your thoughts on tire selection and alignment specs, either posted here or sent to me separately have also been helpful.
Thanks
Philip |
Philip Airey (Pma1010)
Junior Member
Username: Pma1010
Post Number: 82
Registered: 7-2002
| | Posted on Friday, January 03, 2003 - 1:28 pm: | |
All
Rob's comments are on the mark given the specific request I made. As a follow up, can anyone provide me with the diameter of the rear bars on the 308 QV B and S and on the 328 B and S.
Philip
Thanks
Philip |
Rob Schermerhorn (Rexrcr)
Junior Member
Username: Rexrcr
Post Number: 59
Registered: 11-2002
| | Posted on Friday, January 03, 2003 - 11:13 am: | |
Mitch,
If there is only one thing I've learned with suspension tuning, especially when modifying someone else's design, it's that one can generalize (bigger then less grip, etc.), but that is only an opinion that cannot be validated by testing and become a "proven-in-all-cases rule of the suspension universe." Many times one will see what is expected, but push further in the same direction and the results may begin to improve. This is part of the attraction to suspension system design, and engineering in general. The guys who believe the "hard and fast rules" of race engineering get left behind at the finish line eventually.
I agree, killing one end of a car to go for balance rather than grip is not the best solution, but one which is utilized every weekend around the world to obtain a drivable car. Of course you want more grip.
View this tread in it's context though and you will see why we're making these specific recommendations for this specific car and this specific driver/owner on this day for this type of driving.
Yes I agree, softer front bar is definately something to try (and the Addco links can be utilized there, too), but here we are trying to use an example from a 328 owner's experience (see the previous link), so we travel down this road 'cause it's less expensive than the alternative, and see where it leads us. |
Mitch Alsup (Mitch_alsup)
Member
Username: Mitch_alsup
Post Number: 282
Registered: 4-2002
| | Posted on Friday, January 03, 2003 - 10:22 am: | |
Adding bar to the rear reduces rear grip countering understeer.
Subtracting bar from the front increases front grip countering understeer.
Which car goes around the trun faster: the one with lower grip in the rear to counter understeer, or the one with greater grip in the front to counter understeer?
Unless you have more roll than you like, you might be better off will less bar in the front. This remains true until you get so much roll that the camber curves alter the grip of the tires onthe road. |
Rob Schermerhorn (Rexrcr)
Junior Member
Username: Rexrcr
Post Number: 56
Registered: 11-2002
| | Posted on Friday, January 03, 2003 - 8:37 am: | |
Mark,
You've got it all correct, there is definitely and order of operations to dialing in or modifying a suspension system. And, yes, I agree there are an order of diminishing improvements when making modifications to your example of thin compliant bearing material: the effort to change hardly justifies the slight or negligible improvement. Every application is different, though. I.E. 348, 355, F40 series bushings on the control arm and lower shock mount pound out quickly under repeated track use, especially with proper racing slicks. Ferrari recognized this problem by releasing the Challenge bushing update, which went into production on all lower shock mounts with the F355 in 1995.
I agree again that when planning suspension improvements to your car, almost regardless of specific application, begin with tires/wheels, then tune spring/damper, then tweak with anti-roll bar.
We're discussing ARB's because of other limiting constraints for this specific project: cost, the fact that OEM Koni's have already been invested in, etc. So, simplest solution: slap on the bolt-on-able 328 bar, put on Addco's inexpensive drop links, and the project is done.
Someone with a larger budget should follow the former procedure, and be amazed at what a huge improvement one can make (grip, balance, adjustability, and in many cases, comfort) investing in higher quality components than what originally came bolted to the chassis. |
Mark Eberhardt (Me_k)
Member
Username: Me_k
Post Number: 286
Registered: 5-2002
| | Posted on Thursday, January 02, 2003 - 5:32 pm: | |
I'll throw this out, maybe I'm all wrong, but I wouldn't put urethane control arm bushings (yes on the sway bar)on a street car. On my 308, the stock bushings are pretty thin, I just don't see them moving very far. The stock springs were obscenely soft and the shock just bad, but after changing them the car is nice with very little harshness or road vibration. I also think that the sway bar is the last thing to change, definitely after the springs are picked out since the roll rate is inversely proportional to spring rate, use the sway bars to tune it after everything else is set. Again my car racing is limited to autocross, so I could be mistaken. |
Rob Schermerhorn (Rexrcr)
Junior Member
Username: Rexrcr
Post Number: 53
Registered: 11-2002
| | Posted on Thursday, January 02, 2003 - 7:18 am: | |
Yes, there will be an improvement, but only if the OEM bush material is significantly softer. The "amount" of effective rate increase is very small compared to increasing the diameter of the bar on cars with high durometer bushings from the factory (which include many modern Ferrari's). |
david handa (Davehanda)
Member
Username: Davehanda
Post Number: 413
Registered: 5-2001
| | Posted on Tuesday, December 31, 2002 - 4:54 pm: | |
Rexrcr,
Wouldn't changing all the bushings on the stock rear bar to polyurethane/graphite, give similar improvement as going up in size? Or not? |
Rob Schermerhorn (Rexrcr)
Junior Member
Username: Rexrcr
Post Number: 52
Registered: 11-2002
| | Posted on Tuesday, December 31, 2002 - 4:44 pm: | |
Alignment is definately important, I would not do anything before gathering the "before" data.
It's suspension system, IMO, not idividual component tuning exclusively. So it is all important: tires, wheels, alignment, pressures, temperatures, construction, compound, geometry characteristics (camber gain, roll centers, CG, wheel base, track, roll couple distribution, ride frequency, roll frequency, pitch, heave, warp), unsprung weight, sprung weight, corner weight, rake, aero, etc.
In this forum, it's easier to discuss one topic at a time. And also, I try to take into consideration the amount of time available, cost/time benefit for the client or job.
Sometimes it's easier to offer a quick solution to try first because the problem does not necessarily require in-depth study.
Without the data, it's just an opinion. |
Rexrcr (Rexrcr)
Junior Member
Username: Rexrcr
Post Number: 51
Registered: 11-2002
| | Posted on Tuesday, December 31, 2002 - 12:01 pm: | |
Philip,
I have a couple of solutions.
Quick, easy, budget solution is to get the 328 bar (it's a bolt-on?) and buy Addco's adjustable end links. They make them in a variety of lengths. I've never used them, but they sure are cheap and should give you the adjustability to quell your concern over making the car too loose. http://www.addco.net
If you want ultimate control over your chassis, then I strongly suggest following what was outlined in the other thread. Baseline the rubber, it has by far the greatest affect over chassis dynamics. Go with high quality race bread easily adjustable dampers and slightly revised spring rates. Keep the springs close to stock, but by adding quality adjustable damping, you gain incredible control over the car's behavior. Drivers who use adjustable dampers for the first time are amazed by the amount of quality control they give you over the car. Driving is believing. And I'm not talking about a mass produced shock, so you're looking at an investment, not an inexpensive solution.
My company can build a set of quality dampers with a wide range of adjustability for about $2,800/set. We're building a set for a fellow F-Chatter in Singapore for his TR right now. He'll be able to maintain a nice ride on the street and really control the car at track events by simple adjuster knobs. He complains about the typical push built into Ferrari's, now he has control over how much he's comfortable with. This is a powerful tool. I will help you set it up and offer tuning advise. We even have a system where you can do this remotely via computer control in the cockpit.
This is the same type of project I did for nearly a decade with Challenge customers and other on-track enthusiasts. |
JRV (Jrvall)
Member
Username: Jrvall
Post Number: 487
Registered: 11-2002
| | Posted on Tuesday, December 31, 2002 - 11:37 am: | |
Why don't I ever hear camber settings being mentioned along with corner wieght checking ?
How are you guys developing a Base Line? |
Philip Airey (Pma1010)
Junior Member
Username: Pma1010
Post Number: 81
Registered: 7-2002
| | Posted on Tuesday, December 31, 2002 - 10:40 am: | |
Rex
It's obviously related. I'm putting the front of the car back together now and am planning to tear down the rear (shocks, a-arm bushings and swaybar/bushings).
My take on the trust of the prior thread was "do tires first, then do sway bar". But also, no one expresssed any direct experience of a larger rear sway bar on a 308 (outside of Mark's custom set up with Ohlins, stronger springs etc) and the friend I cited who found significant gains on his 328 (4s a lap). Having heard the feedback and also talked to a couple more people, having an adjustable rear sway bar would seem to be the best of both worlds. In particular, simply putting a gts bar on my car (a "b") may work but it'd be problematic if it produced a too tail happy car (as you know, the fatter bar was to cope with the more flexible structure of the open top car).
I have found a company advertising in GRM that claims to make custom sways, mounts (and links) and have an enquiry into them.
My concern given the stock end links come from the lower rear control arm is the range of movement available. without going to welding custom bosses on the upper a-arm and cutting off the lower.
I certainly be interested in any advice and thoughts and, if your company would make somthing up, what it might cost me. On the latter, feel free to post or email me privately, thanks
Philip
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Rexrcr (Rexrcr)
New member
Username: Rexrcr
Post Number: 50
Registered: 11-2002
| | Posted on Monday, December 30, 2002 - 10:05 pm: | |
Philip,
Are you refering to this past thread? http://www.ferrarichat.com/discus/messages/112/183680.html
I have (and others here on FC) more than a decade of experience setting up F-cars (and other race cars). My company can build one for you, though if this is the same project as the above thread, I'm curious what you have tried since then? |
Philip Airey (Pma1010)
Junior Member
Username: Pma1010
Post Number: 80
Registered: 7-2002
| | Posted on Monday, December 30, 2002 - 7:57 pm: | |
Having upgraded my gtb with fatter and unequal (F, R) section tires, I have increased the amount of inherent understeer. I am looking into an adjustable rear bar on my 308 and am curious if anyone else has been done this path, and, if so, if the stock end link mounts were retained. A search of the archives found no hits.
Philip |
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