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Author Topic:   Rear spring height
posted January 03, 2004 11:32 AM
Wondering if there are any drawbacks from using the tallest rear springs that will fit in the car, assuming the correct ride height can be maintained. I went from 11" to 13" this past year and it seemed quite a bit better, especially on a fast, tacky track. Seems like alot of new cars are being built with 15" and even 17" springs. This is on dirt, metric framed, 3000# car with a stock type four link rear with weight jacks. THX

posted January 03, 2004 06:41 PM
Ride height is a neccasity, spring rate is too. Whatever spring length you use to achieve this don't mean squat. That is just what you have to do to get it right. If you put the new ones in and felt a differance I am guessing the old ones were worn out.

posted January 04, 2004 09:04 AM
Of course I know that ride height and spring rates are important. I think spring height DOES mean "squat". I am not talking about wore out springs either. I am talking about coil bind and on a car that rolls over hard on the RR and getting off of a short (11") LR spring. There are alot of professional chassis builders using 15" and even 17" rear springs, they must think it is better cuz its alot easier to put in a 11" or 13" tall rear spring in a metric chassis.

[This message has been edited by sixwillwin (edited January 04, 2004).]

posted January 04, 2004 09:57 AM

posted January 04, 2004 04:13 PM
Hmmm... I'm rather interested in this. I'm currently using 11" rear springs. I haven't checked frame heights yet this year, but I think from past measurements they were all +/- 1/2". Our track says level side to side front to back, but they've let some obviously 'unlevel' cars go. I could always just put spacers under the body mounts to make it LOOK level, doubt they'd look at the frame.

I'm just wondering how you'd get a 13" or 15" spring in without having to use a compressor every time. With the 11"s, we have a hard time getting them in and out without taking the shocks off. But I guess that wouldn't be all bad if it made the rear work right.

Anyone have frame heights with 11" and 13" springs? Weight differences by using the taller springs? I has to affect things significantly.

posted January 05, 2004 09:30 AM
My 2003 Terminator uses a 15" Hypercoil rear spring. I think it's mainly done so that the OEM upper spring cups can just be removed. That's quite a bit of weight that you're replacing with 2 little clamp on screw jacks.

I probably got a pic or two, if someone is interested.

posted January 05, 2004 04:23 PM car does not use any of the stock spring mounts(there cut out totally), its all fabricated and only has a jack screw nut welded in and supported by tubing, so I can simply raise that mount and fit any size spring in that I want too.
Istock59, does your car use 15" springs on both rears?? Could you email me a pick of that please? THX

posted January 06, 2004 05:29 AM
That was my point, the spring is the same rate regardles of height, if you move the buckets of course you change the height you need to use. If you're coils are binding that is a different story. If you are bottoming out it will not effect that. But that is not the question you asked so don't get upset if you didn't like the answer.

posted January 06, 2004 08:03 AM
dirtrace...thx for the long answer and insight...your CGH answer is interesting, seems to make sense, my scales dont figure that for me however, is there another way to figure that CGH??
Istock59..thx for the pics and your email.

When I had an 11" spring in the LR , I know/suspect that I was completely coming off of it as i got into the corners on a fast tacky track, the way I have my control arms mounted, I get alot of body roll and sidebite. So then I put a 13" LR spring in, the car stay supported by the spring longer/better. So, I am just trying to improve that again by possibly a 15" spring. thx all

posted January 06, 2004 10:15 AM           
racerguy, read my post, youll learn something.

It makes a big difference where the tops of the springs.

Six, I would want to find out the cg height before I just tossed in 15 in springs. If your at your cg now, then 2 more inches will hurt your performance....

Ill look at all my books for another method to figure cgh. I bet if you call longacre and ask them theres a mathmatical formula that can be used. Ill look at my scales directions maybe its in there!!!


posted January 06, 2004 10:21 AM
OK thx Jeff...........

posted January 06, 2004 10:53 AM
found this....

sounds hard to do unless the car is race ready....i guessed and used these figures...108" WB, 3050# car, 1450# front weight when level, 82" LF tire, 84" RF tire, car raised 12", even if the front only gained 75# when raised, using the 15" springs should still put the tops of them below the CGH. I have no idea how many pounds will be gained at the front when raised however, I am just guessing that it would at least 75#.? If its more, than even taller springs would work, although 15" is as tall as I am thinking about going.

Jeff, what do you think?? THX

True Blue
posted January 06, 2004 07:32 PM
Guys, check the tool box.Jammin has added a height calculator.Really Cool