spitfun New Reader
Dec. 16, 2012 2:40 p.m.

Ok guys,I have a question. I am trying to up the spring rate on the rear of my autocross car. I am not sure on the stock spring value as I keep finding conflicting information on the web. If I move the lower free spring INTO the pivot box-in essence disabling the swing operation I believe I will stiffen the whole assembly up. My spring values are .330" leaf thickness (5 leaves all the same),1.75" wide,40.5" eye to eye. The spring is 4.25" off the ground so if I put a 1" lowering block in there I shouldn't have any tuck in problems. The calculator I found online (link below) says the spring rate should be about 394 lbs. at that point. What do you guys think?? Thanks Rich LINK: http://www.therangerstation.com/tech_library/leafspringrate.htm

erohslc HalfDork
Dec. 16, 2012 7:36 p.m.

All you will do is change roll stiffness (and probably NOT to your advantage).
Same number of leaves, same distance between eyes = same spring rate.

You seem to be fixated on the rear spring rate. But the critical issue on a Spitfire is getting the rear camber (and thus the rear ride height) dialled in.

Anyway, are you SURE that you need to make the rear spring stiffer?

Maybe you should get the rear camber (and thus ride height) set correctly, and then drive the car to see what you actually have. That will tell you what direction to take.

Carter

Ian F PowerDork
Dec. 16, 2012 9:05 p.m.

The thing about a Spitfire is by the time you're putting down enough power and have enough traction that the spring rate is a concern, you have much more important things to worry about, like the differential, u-joints and axles.

spitfun New Reader
Dec. 16, 2012 10:54 p.m.

I already have a Quaife Diff,race axles and stronger u-joints. The car (RotoSpit) will make about 190 HP at the crank. I have another GP Spitfire (the one in my avatar) that does have a stiffer spring in the rear and a camber compensator as it is an older setup. I know that Triumph softened up the spring on the swing axle car and feel the car should be a little more balanced with 480 lb. front springs and a stiffer spring rate in the rear. Rich

You'll need to log in to post.

Also on Grassroots Motorsports

GRM Live on Wednesday, June 28: The Science Behind Fasteners

17 hours ago in News

They hold all of your work together, but do you know when to use each type of fastener?

Action Cam Guide

17 hours ago in Articles

Capture your on-track memories with today’s latest and greatest

Reader's Ride of the Week: Troyer Modified Hillclimber

18 hours ago in News

It's a circle track car that's been convinced to turn left and right, and go up hills.

You Need This: Track-Ready 1991 Mazda Miata for $5500

19 hours ago in News

What’s better than a Miata? How about a Miata that’s ready for the track?

MX-5 Cup Racing: Live on Your Screen This Friday and Saturday

3 days ago in News

Catch all the action of the Global MX-5 Cup race at Road America live this weekend.

How to Run Compressed Air at Home

3 days ago in Articles

A guide for installing an air compressor and air tools in your home garage.

2017 Volkswagen Golf SportWagen TSI 4Motion

3 days ago in New Car Reviews

Say hello to the Volkswagen Golf SportWagen TSI S with 4Motion. It comes with a turbocharged 1.8-liter engine that is ...

You Need This: $1600 Street Racer Ford Festiva

3 days ago in News

It already has a GRM sticker and everything.

Get Your Subscription Combo Deals!

3 days ago in News

Get both our magazines for the price of one!

Your Projects: smokindav’s VW GTI Project

3 days ago in News

Love a good MK5 GTI? You might enjoy this build thread.

Wing It: Simple Talk on the Complex Subject of Aerodynamics

4 days ago in Articles

Whether sleek, boxy or somewhere in between, all cars interact with the air while racing down the track.

2018 Acura TLX V6 A-Spec

4 days ago in New Car Reviews

Acura is introducing something new for the 2018 model year: the Acura TLX V6 A-Spec. It's the highest trim level ...

OUR SPONSORS

Grassroots Motorsports Magazine

Subscribe Today

Also get your instant access to the digital edition of Grassroots Motorsports Magazine!

Learn More
JfgsFqSZbXRDmC5LfuOooTeXhPfJGJYb