Cutting a 3"ID CO Spring for the Rear?

[Dave Patten]

Has anyone ever considered or tried cutting a 14" or 16" long x 3" ID coil over spring in half to make 2 rear springs to fit in a 510's stock rear spring location?

Here are my thoughts. I'm looking to install 1200-1400 lbs rear springs in my vintage 510 roadracer. Rules require that the springs be in stock location for some vintage groups that is why I'm not looking to use coilover shocks.

The thought is if I purchase one 3"ID x 16" coil over spring rated at 650lbs and cut the spring in half with a fiber cut-off wheel, I would end up with two (2) 8" springs that would have a spring rate of around 1300lbs. They would have one flat end and one pig tail end to fit the 510.

I plan on using a DPR ride height adjuster to get proper ride height.

Anyone ever try this?

The 3" CO spings are about $100 each so the experiment wouldn't break the bank.

[okayfine]

Haven't heard it being done, but it makes sense from a rate/size standpoint. The only question would be the ride height, which you're taking care of via DPR.

[HudsonMC]

DPR also sells those ride height adjusters for 2.5" springs. He also sells a neat little weld-in adapter for the control arms to use 2.5" springs that's also only $100. It may open up your spring selection quite a bit. Do the rules require they be the springs be the same diameter, or just location?

This is what I'm doing with my car. I have the parts, but have not installed them yet.

[Dave Patten]

DPR also sells those ride height adjusters for 2.5" springs. He also sells a neat little weld-in adapter for the control arms to use 2.5" springs that's also only $100. It may open up your spring selection quite a bit. Do the rules require they be the springs be the same diameter, or just location?

This is what I'm doing with my car. I have the parts, but have not installed them yet.

The DPR rear weight adjusting kit is designed to work with stock diameter springs, so the 3" ID springs should work fine. The adjustment is good from many points, ride height, adjusting corner weight and compensating for spring height.

Being the 3" spring fits the stock spring pocket in the control arm and the adjuster, it shouldn't be a big deal to use them.

As far as using 2.5" springs, I do not beleive the spring diameter matters from a rules veiwpoint, but I'm not sure I'd find any real benefits from using them. The 3" springs come in 500, 550, 600, 650, 700, 800 lbs rates so when cut in half it covers 1000, 1100, 1200, 1300, 1400 & 1600, which is about as good as you'd need.

Here is the DPR rear weight adjuster hardware. Pretty reasonable at $130.
(I will verify the OD of the hat before I order.)

[HudsonMC]

The DPR rear weight adjusting kit is designed to work with stock diameter springs, so the 3" ID springs should work fine. The adjustment is good from many points, ride height, adjusting corner weight and compensating for spring height.

Being the 3" spring fits the stock spring pocket in the control arm and the adjuster, it shouldn't be a big deal to use them.

As far as using 2.5" springs, I do not beleive the spring diameter matters from a rules veiwpoint, but I'm not sure I'd find any real benefits from using them. The 3" springs come in 500, 550, 600, 650, 700, 800 lbs rates so when cut in half it covers 1000, 1100, 1200, 1300, 1400 & 1600, which is about as good as you'd need.

Here is the DPR rear weight adjuster hardware. Pretty reasonable at $130.
(I will verify the OD of the hat before I order.)

You can order them for stock diameter springs or for 2.5" springs. Here are my parts in my shop shown with a 2.5" spring:



They fit super snug on my 2.5" springs, and I'm sure the same is true for the other size mounted on stock springs. What is the stock spring diameter? Isn't the stock spring diameter something more than 3"? I don't remember. If you want, I think Don does a lot of this stuff one-off, so you may be able to get him to make you some hats for a 3" spring.

[okayfine]

ID for stock rear springs is 3", give or take a .01".

[HudsonMC]

ID for stock rear springs is 3", give or take a .01".

Ah, well, in that case, sounds like a plan.

[tr6racer21]

Rules require that the springs be in stock location for some vintage groups that is why I'm not looking to use coilover shocks.



Dave,

Which Groups are you looking to run with. Got off the phone with Don O. a few minutes ago as I am in the middle of this same to do or not to do issue. Out his way the co's are frowned upon. Not sure about this coast though. When I ran the Jefferson (VRG/VDCA) last year there were at least (2) 510's running co's including Leitzinger. I usually run with VDCA which follows SVRA guidlines. I know that SVRA is in the middle of reorganizing but at this point I can't find anything in the rules that would object to co's on the rear of our cars.

http://www.svra.com/SVRA/SVRAHome.nsf/a ... penElement

http://www.svra.com/SVRA/SVRAHome.nsf/a ... penElement

Either way you still have to sort the car with both systems...don't know where there is any competitive advantage using co's over weight jackers. Weight jackers may be easier to set ride height and co's may provide an easier change of spring rate...but neither is more advantageous on the track if set up correctly.

Interested in your thoughts and interpretation

Chip

[Dave Patten]

Chip,
A friend I race SCCA with has an FP PL510 with coilover and rear disc brakes. He spoke with the tech inspectors at SVRA about racing with them in 2010+/-. They told him the rear disc, coilovers and Goodyear slicks needed to go before they would allow him to run.

I'm not sure where this was in SVRA's ownership. The prior owner to today's was quite "open" in the rules interpretation, so it may have been the earlier owner's inspector (2 prior to today's) when things were a little tighter.

I am looking at running with one or more ofthe following, SVRA, VRG and a small group HRG that piggybacks on marque club and SCCA races as a single race group.

[duke]

I ran cut 3" ID springs in the rear of my car for a couple of years, until I recently switched to coilovers. The only negative that I experienced was that the cut section of the spring doesn't fit perfectly into the pocket of the trailing arm. If you look at the stock springs, the last coil on the spring on the trailing arm side is flattened slightly (not as much as the body side obviously) to allow it to seat better. When you cut the springs 3" ID springs you don't get this slightly flattened coil at the end. Once the springs do get seated though, they work just fine.

Dave, if you're interested I still have the springs I cut. It was a 600# 18" spring that I cut in half, then cut a little more off of to achieve my desired ride height. I think they are about 8" long now (I would have to double check though). PM me if you're interested, they are just sitting in my parts pile currently.

[tr6racer21]

Dave,

You will enjoy VRG. Cal Trumbo, Mark Palmer, and the rest of that group are really great people. They do a stellar job of putting on the Jefferson 500. The Turkey Bowl this month is a low key event without timing and scoring, but might have a little snow...probably this year!

I run the most with VDCA, Mike Jackson and his wife Sandy, a group that splintered from SVRA when they were more interested in making money and entertaining high end elite cars. With VDCA you will get a ton of track time (usually 4 sessions/day) or more, and low cost as they are not for profit. They put on events at Sebring, Roebling Road, Road Atlanta, and VIR. The Wild Hare at VIR is always a great time. They share some events with VRG.

The VIR Gold Cup which was a few weeks ago has always been a constant even though its been run by a few different groups and the track itself. I heard the other day that the new SVRA (minus Carl Jensen and Jack Worley) has a long term contract to run the Gold Cup starting in 2013.

If you can get to a VDCA event thats where the most track time for the dollar is...I think second comes VRG...then the rest

Looking forward to seeing you most likely at the Point for the Jefferson....think about coming to VIR as well if you can make the trip.

On a technical note I am going to try fitting some older Carrera aluminum body coilovers that I ran on my Eprod TR6 to the rear on the 510...what the heck their on the shelf and won't cost me anything. If that doesn't work out I'll be back to either weight jackers or entertaining Don's coilovers (steel body shocks w/coilover sleeves)

I pulled all 4 corners on the car today and went about setting up ride heights and travel...sitting on 3" blocks right now...pictures to come

Maybe I'll get it out for the Turkey Bowl

Take care, Chip

[DADZSUN]

I've been running a cut 3" ID rear spring for a year now.

I purchased a single offroad 18" long, 3"ID, and 400lbs/in spring. I cut it in half (sawzall) to get two ~800lbs 9" long springs complete with a pigtail for the lower spring perch.

The setup works well, just be sure the spring is coiled clockwise (when viewed from above) so the pigtail seats in the lower control arm perch as intended (don't ask how I figured that out). Several offroad springs I've researched are wound counter-clockwise.

Fritz

[Byron510]

Hi Fritz,

I have to ask, but what brand of spring did you end up buying and what ride height did you end up with installed in the car wet (fuel tank, interior ect installed )?

Photos please?

Byron

[Uber Deaf One]

I've been running a cut 3" ID rear spring for a year now.

I purchased a single offroad 18" long, 3"ID, and 400lbs/in spring. I cut it in half (sawzall) to get two ~800lbs 9" long springs complete with a pigtail for the lower spring perch.

The setup works well, just be sure the spring is coiled clockwise (when viewed from above) so the pigtail seats in the lower control arm perch as intended (don't ask how I figured that out). Several offroad springs I've researched are wound counter-clockwise.

Fritz

This is what I have been running as well. Currently at 1100 lb rear springs, a little under 9" tall each. I started with a 550 lb 18" length truck spring with a 3" ID.

[akara]

I have been running a single cut Eibach offroad spring in the rear of my 4 door for a year now and its great.
My car is a daily driver mostly stock car that I wanted to be comfortable on the street so I went with a single 18" 400lbs Eibach spring, was $120 bucks from ORW and I cut it in half with a cutoff wheel. You can get springs up to 800lbs in an 18" length which might be pretty good for roadracers!
I used part number EIB1800.300.0400, this turns into two 800lbs 9" springs. I would say these would match up well with 150-175lbs springs in the front. I currently have 200lbs in the front and the front is a little stiffer.
Here is my ride height with the cut 18" 400lbs eibach. I still have the stock rubber spring isolator in there too which adds half an inch or so.
http://imageshack.us/a/img807/8286/photo2ct.jpg
http://imageshack.us/a/img689/5741/photo1do.jpg
http://imageshack.us/a/img190/9225/photo3og.jpg

vs stock springs which is hideous LOL
http://imageshack.us/a/img638/520/img0265u.jpg