Question about spring length

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Lynx94
Posts: 25
Joined: July 1st, 2006, 12:07 am

Question about spring length

Post by Lynx94 »

I removed the spring from my Lynx B. Although I can't determine the strength of the spring, it is 10" long. I have two other springs that I purchased separately from this car. Spring #2 is 149lbs and 12" long. Spring #3 is 115lbs and is 12 7/8" long.

Can I install either spring #2 or spring #3, then set the suspension, and have everything work fine? Or should I use only 10" springs on my car?

Thanks,

Dave
Dietmar
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Joined: June 24th, 2006, 11:56 am

Re: Question about spring length

Post by Dietmar »

Dave

You have a personal message

Dietmar
Quixote Racing
SR Racing
Posts: 1205
Joined: June 24th, 2006, 1:58 pm

Re: Question about spring length

Post by SR Racing »

You can use different spring lengths if the geometry allows you to adjust everything correctly. Please note that if the geometry changes this could effectively change the spring rates. If the bell cranks change position it can move you from rising rate to fading rate (for example). This is due to the different angle that the bell crank may take. You can probably use spring perch spacers to resolve this.

However if you change spring RATES the car handling will very likely be much different. In the case that you have described a 149# vs. a 115# there will be handling differences. You can possibly level the playing field by drilling a different hole in the bell cranks to change the ratio. But, you are getting into a lot of effort when a new spring only costs ~$50.

Jim
SR
hardingfv32-1
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Joined: December 1st, 2006, 8:01 pm

Re: Question about spring length

Post by hardingfv32-1 »

Why will the handling be different if he changes the rear spring rates within the range specified in the thread? Interested in your opinion.

Brian
problemchild
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Joined: June 25th, 2006, 9:34 am

Re: Question about spring length

Post by problemchild »

Here is a link to a previous thread that might help you determine the rate of your current spring.
http://www.formulavee.org/interchange/v ... ate#p17496

You never explain why you want to change the spring in the first place. "Somebody" selected the one you are using. Often it is the easiest one to install on the shock. Those soft springs require a lot of compressing (and about 6 hands) to assemble.
Greg Rice
"Happy 50th Birthday"
jpetillo
Posts: 759
Joined: August 26th, 2006, 2:54 pm

Re: Question about spring length

Post by jpetillo »

hardingfv32-1 wrote:Why will the handling be different if he changes the rear spring rates within the range specified in the thread? Interested in your opinion.
Brian
Off the top of my head, if you do as you say, then the ride height should be able to be maintained. But, the different spring rate would have the car react differently to jacking forces and bumps. Bumps can be dealt with somewhat with damping adjustments (if you have that ability). The jacking can be dealt with somewhat by modifying the compliance of the droop stops bumpers. Okay, dinner's on the table - gotta go - I hope I didn't say anything wrong - can't think while I'm hungry!

What do you think?

John
SR Racing
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Joined: June 24th, 2006, 1:58 pm

Re: Question about spring length

Post by SR Racing »

hardingfv32-1 wrote:Why will the handling be different if he changes the rear spring rates within the range specified in the thread? Interested in your opinion.
The rates he gave were 149# and 115#. One takes an additional 34# per inch to compress it. Thus at any corner, under braking or under throttle (or track irregularities) there will be additional rear camber changes at a minimum. There are other dynamics, but that is the most obvious. Maybe I misunderstood you question?
Lynx94
Posts: 25
Joined: July 1st, 2006, 12:07 am

Re: Question about spring length

Post by Lynx94 »

Thanks everybody. To answer Greg's question, why did I take it off...

I don't have much in the way of mechanical aptitude. One of the last times I had the car on the track (which was unfortunately several years ago) someone pointed out that my spring was binding and that I should get a new one. He suggested a 150lb spring. He had owned a Lynx B so I didn't doubt his suggestions. I bought a 150lb spring from DRE, but I had measured the diameter wrong on my orginal spring and ordered one 1/4" too big. So I never used that spring. In the meantime, someone on the board was selling springs and I bought them, not thinking about length. My thinking on the 115lb spring is that it might be good for bumpy Nelson Ledges, and for just getting some seat time. Then I was cleaning the garage today and looked at the springs, noticed they were longer that the one I took off, and thus the post.

I think I'll put the original spring back on, get some much-needed seat time, and fine tune things later. And yes, this spring did work very well for the previous owner. I hadn't thought of that.

Thanks again,

Dave
problemchild
Posts: 901
Joined: June 25th, 2006, 9:34 am

Re: Question about spring length

Post by problemchild »

Hey Dave,
Gaining compliance and improving ride over bumps is best delt with by dampers (shocks). Nelson is a track where the well-tuned big-dollar shocks can make a big difference. My car handles the Nelson bumps like they are not there .... and I see most of the cars around me are afraid to drive within 3 ft of the track edge because they have no confidence in where their car is going. I tried another pair of front shocks and had the same lack of confidence and was significantly slower.
Changing your rear spring may change things a little bit but I doubt it will make much difference. Stiffer or softer may be better but that would depend on how it matched up with the shock condition and valving. It is not uncommon for these soft springs to be mis-shaped and drag on the shock body. The 2 1/2' springs seem to be better than the 2 1/4" in this regard. While this dragging is not ideal, it has been a constant in FV, and appears to be insignificant. It is imperative that there is no binding or interference between suspension components through the full range of travel. That needs to be fixed ..... but all the other stuff above appears to be "drive the car and deal with it the best you can" status.
Also, make sure that the front end has no binding, interference, and your steering links are set for minimal toe change over bumps. The Lynx has the beam mounted very low on the chassis so make sure the front suspension is not binding/hitting the horns (which can be bent or removed).
Have fun!
Greg Rice
"Happy 50th Birthday"
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