BD Race Springs - Rear Rate

TimeForACobra · #1 (**permalink**) 02-20-2014, 08:40 AM

Good Morning,

Does anyone know the rate of the rear Backdraft Racing Race springs?

Thanks,
Keith

Kobura · #2 (**permalink**) 02-20-2014, 02:37 PM

I think that my BDR springs, front and rear, are too stiff maybe because of the (relatively) small engine in my build. Admittedly, the handling through curves is great, like the car is on rails, but not so great if the road surface is bumpy. So, I attempted to find out what the stock spring rates are but came up with nothing. Therefore, I don't think anyone would know what the race spring's rate is. I have gotten a pair of softer coil springs for the front on the assumption that the stock spring rate is about 300 lb/in, but have not installed them, yet. I don't think that there are any softer springs for the rear as I believe the stock ones are the same as for the BMW 3 Series 318i. If anyone has spring rates for BDRs, front or rear, stock or race, it would be nice to know.

TimeForACobra · #3 (**permalink**) 02-20-2014, 03:57 PM

Thanks Kobura...

I'm trying to autocross and the stock spring rates are too soft. I've been told when I am on the throttle hard the back end squats pretty low. But, I drive the car quite a bit on the road.

From what I have been able to gather, the stock front springs are 215 lbs, and the front race springs are 450 lbs.

I haven't been able to gather the same info on the rears.

Also, I've heard/read that the race springs could be too harsh for street driving. Well, at least for my preference. So, I want something in between. I'm probably going to try 300 or 350 in the front. Now, I just need to figure out the rear.

The "in between" springs from Backdraft aren't yet available, so I'm starting to research other springs. Right now, my best option is to pull the existing springs and see what will fit.

Thanks again.

PLDRIVE · #4 (**permalink**) 02-20-2014, 07:40 PM

Race springs were (2008) around 450 front and 950 rear.

cbreez · #5 (**permalink**) 02-21-2014, 01:05 PM

Quote:

Originally Posted by PLDRIVE

Race springs were (2008) around 450 front and 950 rear.

That just doesn't sound right for the rear...seems way to stiff for a 2400 lb car...
Why don't you remove them and find a local racer with a spring checker to actually check them? Have you ever really checked your shock travel first...to see what they are doing?

pjmoore2003 · #6 (**permalink**) 02-21-2014, 08:34 PM

I have the race springs, car corners flat and rides nice over bumps... But my seats are much more padded

PLDRIVE · #7 (**permalink**) 02-21-2014, 08:42 PM

I had the springs tested . The rear springs were way toooooooooo stiff for my liking. I would not recommend them if they are still 950.

FYI Coilovers are roughly 60 to 65 % of an e36 rear spring rate ( u may have already known this.)

I run MCS double adjustable coilovers (Moton) on all corners.

Grey 65 · #8 (**permalink**) 01-09-2015, 10:10 AM

Quote:

Originally Posted by TimeForACobra

Thanks Kobura...

I'm trying to autocross and the stock spring rates are too soft. I've been told when I am on the throttle hard the back end squats pretty low. But, I drive the car quite a bit on the road.

From what I have been able to gather, the stock front springs are 215 lbs, and the front race springs are 450 lbs.

I can confirm the stock rates are 215lbs front and 450lbs rear. I had mine tested at Vorshlag Motorsports in Plano, Texas...

I am putting 450lb fronts and 650lb rears on my car.

Kevin.....

mln385 · #9 (**permalink**) 01-09-2015, 05:04 PM

Quote:

Originally Posted by Grey 65

I can confirm the stock rates are 215lbs front and 450lbs rear. I had mine tested at Vorshlag Motorsports in Plano, Texas...

I am putting 450lb fronts and 650lb rears on my car.

Kevin.....

That is quite an increase no. How do you think it will re act with those rates?

Grey 65 · #10 (**permalink**) 01-09-2015, 08:50 PM

Quote:

Originally Posted by mln385

That is quite an increase no. How do you think it will re act with those rates?

It will be fine. The 450lbs in the front is what the math says you should run for racing. The rear should be right at 900lbs-950lbs. But I wanted a little softer so I went with 650lbs since I drive on the street in addition to autocrossing.

There are no real struts for this setup. The closest is the BDR TD front struts which I bought and a pair of Bilstein rears which I also bought... Otherwise you have to have a special set of one offs made.

Kevin.....

Trueoo7 · #11 (**permalink**) 02-20-2014, 07:59 PM

Try Tony Martin at the factory. He helped me years ago with spring rates. Very knowledgable.

TimeForACobra · #12 (**permalink**) 02-21-2014, 05:51 AM

Thanks!

cbreez · #13 (**permalink**) 02-22-2014, 11:00 AM

That's very ingenious! You are very close on the weights. I have scaled my car with a tank of gas and the weights were 602 lf 635 rf 664 lr 714 rr about 47% front and 53% rear. BTW, if you put a driver in the car you will be close to a 50-50 side to side weight distribution.
I mentioned shock travel because a good rule of thumb is that you want 2 to 2 1/2 inches of travel...so if your springs get you close to that, you are close to having the correct rate in the car.
These cars will never feel like a Caddy!

spookypt · #14 (**permalink**) 03-17-2016, 05:21 PM

Hi, Ive done lots of searching but cant find anything in stone to confirm BDR Race Spring lbs. Can anyone confirm if the 450/900lbs mentioned on page 1 of this thread is true?

Backdraft Parts lists them but not their LBS. Need an answer urgently if possible.

Yes Ive emailed Reg...but no answers as yet. Matt

Kobura · #15 (**permalink**) 03-17-2016, 07:17 PM

It is a mystery why this data has not been made available to BDR owners by the 'Boynton Beach Boys' after so many years of discussion. My personal experience over the four years that I have owned my car is never having had a response on a technical question from the folks in FL. You may be able to get some assistance from VMS/Jay as I believe that they have suspension modification kits available and may be able to help you.

spookypt · #16 (**permalink**) 03-20-2016, 11:40 PM

Well no answers at all back so it looks like I'll have to pull them and get them tested. Pain in the ar5e that is for such a simple question.

cbreez · #17 (**permalink**) 03-21-2016, 06:43 PM

Quote:

Originally Posted by spookypt

Well no answers at all back so it looks like I'll have to pull them and get them tested. Pain in the ar5e that is for such a simple question.

Maybe that's a good idea...you know, do your own homework!

Cashburn · #18 (**permalink**) 03-21-2016, 07:08 PM

Quote:

Originally Posted by spookypt

Well no answers at all back so it looks like I'll have to pull them and get them tested. Pain in the ar5e that is for such a simple question.

What color are the springs? If I have a set we will measure them.

spookypt · #19 (**permalink**) 03-22-2016, 03:51 AM

Thanks Cashy. They're red. They're the race spec as per bdr parts store. The parts store lists them but not the poundage and to get my adj shocks valves correctly I need to know spring spec. Thanks heaps.

Cashburn · #20 (**permalink**) 03-22-2016, 11:34 AM

Quote:

Originally Posted by spookypt

Thanks Cashy. They're red. They're the race spec as per bdr parts store. The parts store lists them but not the poundage and to get my adj shocks valves correctly I need to know spring spec. Thanks heaps.

Hmmmm... I've been told race springs are either blue or yellow. The red are the stock springs. So that makes it difficult.

I have a set of blue springs I will see about getting a measure on since those were sold to us as "race springs".