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Author Topic: Total travel of suspension for Bonneville  (Read 15622 times)

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Offline Harold Bettes

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Total travel of suspension for Bonneville
« on: May 12, 2007, 12:22:29 AM »
Hey Guys,

For a Gas Coupe / Sedan: Is a total suspension travel of 2"-3" enough for jounce/rebound?  :? I know that the salt is far from a billiard table, but I also don't want too much travel.  :-o I want to limit the travel and still have enough to allow the tires to follow the available surface to generate acceptable traction. :wink:

Also any comment on shock rates that have proved to work well for the full body door slammer critters? :|

Thanks and Regards, :-)
HB2
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Offline Bob Drury

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Re: Total travel of suspension for Bonneville
« Reply #1 on: May 12, 2007, 09:10:05 AM »
Harold, in my opinion the less you have the better.  I run my 4500# car with the front suspension near bottom out, using 550# springs on the front and 400# springs on the rear.  I would also recomend heavy sway bars fore and aft.  Keep the car low as possible, same with ballast.  Use a front air dam if legal for the class.  What you don't want is spring rebound which allows air to suddenly get under the car unless you like to back thru the lights.......................
Bob Drury

Offline JackD

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Re: Total travel of suspension for Bonneville
« Reply #2 on: May 12, 2007, 10:38:02 AM »
The drive train needs a minimum travel to be flexible but you can never design it to be compliant because the surface changes so much in the span of a run and from one run to another.
The required geometry changes were all done with modifications to stock parts.
I limited my cars to about 1 inch total.
Modern cars have a lot of work done by the OEM for aero stuff and will have a device under the front bumper already.
I sorta preferred to lower the car to almost scrape the ground and with a slight tail up angle to let more air out than in.
Added front air dams have a use ,but for my application they made the front of the car larger. :wink:
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Offline ddahlgren

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Re: Total travel of suspension for Bonneville
« Reply #3 on: May 26, 2007, 02:29:17 PM »
If you use a wheel rate(not to be confused with a spring rate) equal to the corner weight you  will usually end up with 3/8 to 1/4 inch travel which is more than enough..
Jack I am with you low is good and small as well. I might add if it has broad flat surfaces on the topside you might want to add 'landing gear' as well. It is a 3 dimensional world at least and you can spin in all planes.. pun intended.. If you get everything else right adding lightness can help a bunch as well. Think of the 1/4 speed as your 60 ft time and you are on the right track or portion thereof..
Dave

Offline JackD

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Re: Total travel of suspension for Bonneville
« Reply #4 on: May 26, 2007, 04:52:21 PM »
 "Think of the 1/4 speed as your 60 ft time and you are on the right track or portion thereof"..
Dave
[/quote]

If your CD and CG are correct and you are not driving over your head, you have a better chance to stay on the track and not go on your head.
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Offline Sumner

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Re: Total travel of suspension for Bonneville
« Reply #5 on: May 26, 2007, 06:12:43 PM »
If you use a wheel rate(not to be confused with a spring rate) equal to the corner weight you  will usually end up with 3/8 to 1/4 inch travel which is more than enough..
Jack I am with you low is good and small as well. I might add if it has broad flat surfaces on the topside you might want to add 'landing gear' as well. It is a 3 dimensional world at least and you can spin in all planes.. pun intended.. If you get everything else right adding lightness can help a bunch as well. Think of the 1/4 speed as your 60 ft time and you are on the right track or portion thereof..
Dave

Interesting :-).  Is this the way Keith's car was setup when it ran so well on the rough track in '05??  Do you feel 3/8 is good for a track that is that bad??  I knew about spring rate of a tire, but this "wheel rate" is new to me.  I found the following site that seems to explain it pretty well:

http://www.miracerros.com/mustang/t_wheel_rate.htm

You are correct about the 1/4 speed (speed at the 2 1/4 trap for someone that might need to know what it is).  I looked at our runs last year and if we picked up 6 mph at the 1/4 from one run to the another we carried it through the 5 mile, so get your 1/4 speed as high as possible.  Don't just think you can run down to the 2 and then get on it.

Thanks and c ya,

Sum

Offline ddahlgren

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Re: Total travel of suspension for Bonneville
« Reply #6 on: May 27, 2007, 06:24:31 AM »
There was nothing basically wrong with the 05 track only cars and bikes built for a perfect track complaining. Building something that requires a perfect track and not adjustable is silly. Yes I know I am right that is why I offered the info about the quarter speed. Yes ran a setup like that..
Jack I suspect you meant CP and CG.. Cd has nothing to do with it as fare as I ever knew..
Dave

Offline JackD

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Re: Total travel of suspension for Bonneville
« Reply #7 on: May 27, 2007, 07:07:24 AM »
Ya, dats FARE. lol
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Offline jimmy six

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Re: Total travel of suspension for Bonneville
« Reply #8 on: May 29, 2007, 10:56:03 AM »
It's all about the 1/4.......Every fast guy will tell you that. Any bets I have made on the salt were 1/4 mile speeds.
When we would watch Al, Nolan, Nish, or Tom run their liners we would wait for the first speed and for the most part knew if we were going to see history in the making.

I believe just the minimal suspension is needed for your vehicle. At the speeds traveled today by the time the vehicle reacts you are another 100 yards down the road so you need it quick and firm. Perfectly round tires are a must especially with a locked you differential. Good Luck
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Offline JackD

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Re: Total travel of suspension for Bonneville
« Reply #9 on: May 29, 2007, 11:11:37 AM »
Please don't tell me I gotta agree with Tone, please don't tell me ! :wink:
"I would rather lose going fast enough to win than win going slow enough to lose."
"That horrible smell is dirty feet being held to the fire"

dwarner

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Re: Total travel of suspension for Bonneville
« Reply #10 on: May 29, 2007, 12:57:08 PM »
Ask Fogliadini and Ron Jolliffe about the race to the quarter.

Fogie in a GMC 6 '32 five window coupe, Ron in a swoopy '34 Ford roadster with a AA engine.

Fogie won the dollar. "it's all about the quarter, the rest is roll out" Fogie

DW

Offline jimmy six

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Re: Total travel of suspension for Bonneville
« Reply #11 on: May 31, 2007, 11:03:01 AM »
One of the finest rememberances I have is the display I made from Fogie and the owners of the BMR Coupe. A total of $2. It is framed and in my trailer. If I can remember, it was whether I could run 196 in the 1/4 after running 190 the day before using high gear only. I ran 202. The plaque was made in their colors of Yellow and Red....................JD
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Offline bvillercr

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Re: Total travel of suspension for Bonneville
« Reply #12 on: July 15, 2007, 11:09:06 PM »
I thought the old time fast guys didn't believe in suspension. 

Offline 1212FBGS

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Re: Total travel of suspension for Bonneville
« Reply #13 on: July 16, 2007, 11:15:07 AM »
rigid up front.... limit to a soft 1" in back.....
kent

Offline bvillercr

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Re: Total travel of suspension for Bonneville
« Reply #14 on: July 17, 2007, 02:06:10 AM »
rigid up front.... limit to a soft 1" in back.....
kent

How is your traction with out front suspension?  Do you get loose anywhere?