E36 Rear Spring Rates for AutoX and Track?

**tptrsn** · 08-15-2016, 09:47 AM

Hi all,

I'm thinking of looking around in my bins of springs for something that might work well in the rear of my e36, and I was just wondering what people tend to like in general? Please don't bother telling me about how it's all part of a big magic picture with shock valving, sway bars and whatever else, I'm just looking for some general information of what you like.

Thanks in advance!

**Pat533i** · 08-15-2016, 06:41 PM

What do you have in the front?

**tptrsn** · 08-15-2016, 08:39 PM

Some 8Ks.

- - - Updated - - -

If you want to say what you prefer rear AND front, that's even better!

I really am curious what people actually like and use though, not just what they think I should use based on some of the current attributes of my car.

**TXBDan** · 08-15-2016, 10:59 PM

Why would you ask for advice and intentionally leave out the information that would result in a much better answer? Want us to make up random numbers?

**Bimmerman535i** · 08-15-2016, 11:28 PM

Aim for 100-150 lb/in stagger between front and rear, with front softer.

Rates vary highly on tires, car weight, driver preference, and DD need, so this is extremely general. Don't take this as gospel, and as always, there will be exceptions.

Primarily DD with some autox/track: front 350-500, rear 400-650 lb/in
Limited DD but still street car: 500-700 front, 600-800 rear
Primarily track car: 700-1000 front, 800-1100 rear or higher

These rates are also very dependent on your shocks. The ubiquitous Koni SA, for example, doesn't work very effectively above 700lb/in. Garbage trash shocks like the $1000 coilover kits are, well...trash. Proper track car shocks work well with the higher rates, but aren't the best choice for a street car.

**tptrsn** · 08-16-2016, 07:28 AM

Bimmerman535i, thanks!!

TXBDan, I think I was pretty clear, I want to know what people like to use on their E36es.

**CoMZ302** · 08-26-2016, 10:05 AM

For dedicated track cars, BimmerWorld generally sends out 800F (6") 900R (5") springs, as a starting point.

I'm going to start with 650F/800R, as I have front roll center correction (less spring needed), and I was able to find some only-used-once rears for cheap.

Also, I've read that NASA guys on the west coast like a little less spring, while east coasters seem to like a little more. If you spend an hour or so filtering through comments on here, you can get a reasonable idea what people are running; assuming they're telling the truth.

Finally, Vorshlag recommends 600F/750R - that seems like a great starting point, if you're willing to start there then buy another set of front or rear springs after a test day.

That's basically where I am, plus 50#. I have more spring for both the front and rear if I need them.

HTH.

**matthugie** · 08-27-2016, 12:21 AM

My car has 600/700, and for autox use I'd like a little softer in the rear. Unfortunately I haven't had it on track with this setup yet so I can't give a complete review, but I wouldn't do more than a 100lb spread between front and rear for a dual duty e36.

**tptrsn** · 08-27-2016, 07:43 AM

I'm surprised to read about people liking such a small front to rear differential with the big difference in motion ratios. I just popped in some 800#ers in the rear to go with the 8Ks I've had in the front, and so far I'm liking the feel for just driving around. No closed circuit driving with it yet...

I had 8Ks in the rear for a short bit, and the car was just really understeery and kind of generally saggy feeling in the rear.

CoMZ302, thanks for the info. That stuff makes sense to me now, I appreciate the help.

**Team Neverlift** · 09-01-2016, 06:32 PM

Calculate your motion ratio (or use figures available on the internet), and target your ideal ride frequency give the rates of your front springs. Everything else is just guessing.

**tptrsn** · 09-01-2016, 09:39 PM

Originally Posted by tptrsn

I'm just looking for some general information of what you like.

Team neverlift, what do you like? That is the point of the thread, not theoretical, or hypothetical, or calculated numbers.

**=BA=** · 09-02-2016, 05:39 AM

Anyone who can quote a ideal target frequency is full of BS imho.

That is too dependant on tire type, track surface, preference, weight etc.

I run 900/500 I think with a full rear coilover. This is a car on slicks.

**tptrsn** · 09-02-2016, 07:57 AM

Thanks =BA=, Very interesting!!

I currently have 8kg in the front and 800# in the rear. I'm thinking I might try a slightly softer spring in the front since I would still like it if the front end was a bit more "pointy." Are you saying that on slicks you are liking 900# in the front and 500# in the rear with the spring around the shock, so you have a rear motion ratio much closer to 1 or the opposite of that?

And by the way, I have done the process of calculating ride frequencies on my old autocross car, and it was fun, but didn't really work out for me.

**aeronaut** · 09-02-2016, 08:37 AM

Here you go, 550F/650R. And now you have my spring rates, and not much else.

**olemiss540** · 09-02-2016, 08:46 AM

Originally Posted by aeronaut

Here you go, 550F/650R. And now you have my spring rates, and not much else.

Those are my rates, theif!

**aeronaut** · 09-02-2016, 08:53 AM

I just 'borrowed' them man, calm down.

**tptrsn** · 09-02-2016, 09:03 AM

You guys like that setup then I guess?

**TXBDan** · 09-02-2016, 09:12 AM

I enjoy the ride quality of a 100/150 setup.

**aeronaut** · 09-02-2016, 09:16 AM

^ Was thinking of running that myself. I can do that by cutting my spare 200/300 springs in half, right?

**=BA=** · 09-02-2016, 10:18 AM

Originally Posted by tptrsn

Thanks =BA=, Very interesting!!

I currently have 8kg in the front and 800# in the rear. I'm thinking I might try a slightly softer spring in the front since I would still like it if the front end was a bit more "pointy." Are you saying that on slicks you are liking 900# in the front and 500# in the rear with the spring around the shock, so you have a rear motion ratio much closer to 1 or the opposite of that?

And by the way, I have done the process of calculating ride frequencies on my old autocross car, and it was fun, but didn't really work out for me.

Ride frequency's are a useless number, unless you can apply that figure but nobody in amateur sports has the data to do that, and even in more professional series they simply don't have the data to apply it, other than their own testing figures. I have done the calculations and have all that data on my car but in practice it's not usuable for anything.

As for making the car more pointy, in your case I would actually try to solve that through the dampers rather than the springs. You could soften the fronts (turn down slow rebound) to make the entry somewhat more pointy.

8K fronts and 800 Lbs/in is roughly equivalent to 450/800. That means that when you calculate wheelrates, you get someting like 397/338. This gives you 54% weight transfer on the front axle. That is very neutral. You always want to ensure you have a bit of front bias to keep traction and the rear planted in steady state cornering. Most people run around 60-65% FYI.

The people that I know that have run very stiff rear springs have all fallen for the same trap, ie they turn down the rear dampers so it rides a bit better, but in reality it makes the rear underdamped and when you hit a pothole or bump while cornering it's easy to spin out of control. Maybe not an issue with AutoX but if you are doing 100 MPH on track you might be in for a supprise.

**tptrsn** · 09-02-2016, 10:49 AM

Thanks again =BA=!!

TXBdan, I have to ask, why are you so hateful on someone asking for personal experience? You just like trolling that well?

**TXBDan** · 09-02-2016, 11:24 AM

Asking for spring rates without context is completely useless and you're explicitely asking that we don't add context. Is your intention to simply average all the numbers posted and run that? I just don't see where you're going with this. There are knowledgeable people on here that will help you if you let them.

**tptrsn** · 09-02-2016, 11:32 AM

Ok, I didn't mean to ask people not to give me the context of their spring rates. What I was trying to get was personal experience based information. That worked out pretty well and I'm appreciative of the input. Clearly I wrote my initial post badly though.

**jakermac** · 09-02-2016, 01:46 PM

I've been running 800f/850r for the last 2 years, but I'm about to try 800f/900r to see if I like it. I have also lowered the rear of the car a little bit more to reduce rake, and I have the small front GC hollow bar and no rear bar. I'm also planning on trying the medium front bar to try to combat bicycling at autocross. I have made modifications to the rear suspension in an attempt to alleviate some bottoming/jacking.

**MassiveWalrus** · 09-02-2016, 03:25 PM

Depends... if the track is smooth... 900 rear 750 front & soft setting on my sways. if the track is bumpy then 650 rear and 450 front but sways are adjusted to be more stiff. this is just my opinion... im not sayings its the best but its works for my driving style during time attack and HPDE events.