Any suggestions for spring rates for a TD-Kline c/o?

[aus]

Just wondering if anyone has suggestions for spring rates for some coils? Most street with a couple track events a year. I'm very happy with the stock ride without EDC.

[Radiation Joe]

Call TCKline and ask them. You'll get a better answer than you could ever get here.

But since you asked, I'll take a wild ass guess and say he recommends 500F/600R. 400 to 500 pounds (front) rode well with the e46 M3s.

[TUNEDM3]

I have been pondering the same question. The motion ratio on the e90 is quite different then on an E36 or E46 M3 so the rear will require a significantly stiffer spring. TC himself is running 400/600, but based on his previous setups he likes a soft setup. I used to have 500/500 on my E46 M3 and was very happy with its ride quality on the street. I mentioned this to TC and he mentioned to go with 500/800 to achieve similar characterstics in the E90. I am just about to pull the trigger on a SA kit with 500/800.

[Orb]

Originally Posted by aus

Just wondering if anyone has suggestions for spring rates for some coils? Most street with a couple track events a year. I'm very happy with the stock ride without EDC.

A 400 lb/in front and 800 lb/in rear. Stick with swift main spring, helper spring and thrust sheets and the ride will be very compliant. If you’re around HP Autowerks Harold might let try his ride with this setup which TC had nothing but good things to say about it.

Orb

[Orb]

Originally Posted by TUNEDM3

I have been pondering the same question. The motion ratio on the e90 is quite different then on an E36 or E46 M3 so the rear will require a significantly stiffer spring. TC himself is running 400/600, but based on his previous setups he likes a soft setup. I used to have 500/500 on my E46 M3 and was very happy with its ride quality on the street. I mentioned this to TC and he mentioned to go with 500/800 to achieve similar characterstics in the E90. I am just about to pull the trigger on a SA kit with 500/800.

If you are going to run R compound it is not stiff enough in the rear. You need to get the rear frequency to 2 Hz with 900 lb/in rear spirng (which is still soft at the wheel 317 lb/in). The balance will be biased towards under steer a bit more at the limit compared to the stock setup with the springs you selected. The quality of spring will make or break this setup due to the high rear motion ratio. It is the one thing you don't want to skimp on.

Orb

[TUNEDM3]

Originally Posted by Orb

If you are going to run R compound it is not stiff enough in the rear. You need to get the rear frequency to 2 Hz with 900 lb/in rear spirng (which is still soft at the wheel 317 lb/in). The balance will be biased towards under steer a bit more at the limit compared to the stock setup with the springs you selected. The quality of spring will make or break this setup due to the high rear motion ratio. It is the one thing you don't want to skimp on.

Orb

Do you know if the ability of the shock to work with such a high spring rate is based off the spring rate at the wheel? The koni shock is just about maxed out with a 700lb spring on a E46, but if its based off the spring rate at the rear wheel I should be able to run a 800-900 lb rear setup.

I am aware that a 500/800 setup is a bit on the softer side for a track car, but I am looking for a nice median between street and track performance. I actually prefer a car with a slightly softer rear as I feel as if I can get on the power earlier out of turns. I will then try and fine tune the suspension by messing with a front sway, ride heights and alignment settings.

[Orb]

Originally Posted by TUNEDM3

Do you know if the ability of the shock to work with such a high spring rate is based off the spring rate at the wheel? The koni shock is just about maxed out with a 700lb spring on a E46, but if its based off the spring rate at the rear wheel I should be able to run a 800-900 lb rear setup.

I am aware that a 500/800 setup is a bit on the softer side for a track car, but I am looking for a nice median between street and track performance. I actually prefer a car with a slightly softer rear as I feel as if I can get on the power earlier out of turns. I will then try and fine tune the suspension by messing with a front sway, ride heights and alignment settings.

The actual spring rate is not important regarding dampening as we only care what the wheel will see. The important thing regarding the damper is the suspension frequency and the motion ratio of the damper. The motion ratio of damper is .81^2. It is squared since we have force and velocity but that not 100% correct when we dive into this but good enough for now.

The rear grip on corner exit will be governed much more by the roll bar stiffness than the spring until you get straighten out. If you are running R compound tire you will not optimize grip until you have at least 2 Hz rear suspension frequency (ideally you want 2.2 Hz). If you are running street tires then 800 lb/in in the rear is good but the 2.2 Hz frequency in the front suspension is too high. The point is softer suspension is only good if your maximizing your friction from the tires which is function of suspension frequency. The key thing is when you go stiffer then binding; friction and a non linear spring rate become the problem which results in poor grip and harshness and is compounded by the high rear motion ratio of the rear suspension. Many tuner will not deal with these issue which is a big big mistake….you have to, and do it well, and it is not easy.

If you talk with Pete at TC he has a good understanding of the motion ratio and what the damper can work with which is up to 1200 lb/in rear spring.

A 400 lb/in front spring is about softest you want to go for tracking or pitch is not well controlled. A 450 lb/in the front and 900 lb/in rear will give you the best of both worlds if your running R compound tires and street tire for your daily drive and give you similar balance.

The springs you can get from TC are much better than H&R ect but they are not really the best or most linear you can get. Swift springs are more less the only thing you should be using if you want a very smooth ride. From my own tuning experience this was the most important thing bar none. You can talk with Harold at HP Autowerks as well about this as he has gone through this comparison.

Orb

[TUNEDM3]

Originally Posted by Orb

The actual spring rate is not important regarding dampening as we only care what the wheel will see. The important thing regarding the damper is the suspension frequency and the motion ratio of the damper. The motion ratio of damper is .81^2. It is squared since we have force and velocity but that not 100% correct when we dive into this but good enough for now.

The rear grip on corner exit will be governed much more by the roll bar stiffness than the spring until you get straighten out. If you are running R compound tire you will not optimize grip until you have at least 2 Hz rear suspension frequency (ideally you want 2.2 Hz). If you are running street tires then 800 lb/in in the rear is good but the 2.2 Hz frequency in the front suspension is too high. The point is softer suspension is only good if your maximizing your friction from the tires which is function of suspension frequency. The key thing is when you go stiffer then binding; friction and a non linear spring rate become the problem which results in poor grip and harshness and is compounded by the high rear motion ratio of the rear suspension. Many tuner will not deal with these issue which is a big big mistake….you have to, and do it well, and it is not easy.

If you talk with Pete at TC he has a good understanding of the motion ratio and what the damper can work with which is up to 1200 lb/in rear spring.

A 400 lb/in front spring is about softest you want to go for tracking or pitch is not well controlled. A 450 lb/in the front and 900 lb/in rear will give you the best of both worlds if your running R compound tires and street tire for your daily drive and give you similar balance.

The springs you can get from TC are much better than H&R ect but they are not really the best or most linear you can get. Swift springs are more less the only thing you should be using if you want a very smooth ride. From my own tuning experience this was the most important thing bar none. You can talk with Harold at HP Autowerks as well about this as he has gone through this comparison.

Orb

How do you calculate HZ? Based on what you are saying do you think the car will be more prone to understeer running a 500/800 spring rate due to lack of grip in the front end on street tires? So for a street tire setup wouldnt a 450/800 be optimal? Are you basing what is best on the stock bmw rate front/rear? Thanks for all your help

[aus]

Originally Posted by Orb

The actual spring rate is not important regarding dampening as we only care what the wheel will see. The important thing regarding the damper is the suspension frequency and the motion ratio of the damper. The motion ratio of damper is .81^2. It is squared since we have force and velocity but that not 100% correct when we dive into this but good enough for now.

The rear grip on corner exit will be governed much more by the roll bar stiffness than the spring until you get straighten out. If you are running R compound tire you will not optimize grip until you have at least 2 Hz rear suspension frequency (ideally you want 2.2 Hz). If you are running street tires then 800 lb/in in the rear is good but the 2.2 Hz frequency in the front suspension is too high. The point is softer suspension is only good if your maximizing your friction from the tires which is function of suspension frequency. The key thing is when you go stiffer then binding; friction and a non linear spring rate become the problem which results in poor grip and harshness and is compounded by the high rear motion ratio of the rear suspension. Many tuner will not deal with these issue which is a big big mistake….you have to, and do it well, and it is not easy.

If you talk with Pete at TC he has a good understanding of the motion ratio and what the damper can work with which is up to 1200 lb/in rear spring.

A 400 lb/in front spring is about softest you want to go for tracking or pitch is not well controlled. A 450 lb/in the front and 900 lb/in rear will give you the best of both worlds if your running R compound tires and street tire for your daily drive and give you similar balance.

The springs you can get from TC are much better than H&R ect but they are not really the best or most linear you can get. Swift springs are more less the only thing you should be using if you want a very smooth ride. From my own tuning experience this was the most important thing bar none. You can talk with Harold at HP Autowerks as well about this as he has gone through this comparison.

Orb

Thanks for all the input from everyone here. It's a LOT more than I thought I would get.

Orb, would you recommend 450 lbs front and 900 lbs rear for most street use and a 2-4 track events a year on street tires?

And in regards to the Swift springs, where would you get those and could you use them with a TDK system? Honestly, I'm sure I'm not at a level I would notice.

[Orb]

Originally Posted by TUNEDM3

How do you calculate HZ? Based on what you are saying do you think the car will be more prone to understeer running a 500/800 spring rate due to lack of grip in the front end on street tires? So for a street tire setup wouldnt a 450/800 be optimal? Are you basing what is best on the stock bmw rate front/rear? Thanks for all your help

Suspension frequency (single wheel corner): pie * (spring rate / corner sprung mass)^0.5 = Hz

Yes the car will be biased towards under steer when compared to the stock car with 500/800 combo.

I am not using BMW biasing for suspension frequency rather what you find in Milken race car vehicle dynamics for a performance setup. A performance setup will have the front frequency equal to the rear up to 10% higher in the front than the rear. The exceptions are KW's which are15% higher in the front than the rear in most cases and guess what ...500/800 is what specified on the m3 club sports and it is 20% higher in the front...a bit too much for my taste. The stock suspension frequency biasing is 12% higher in the rear than the front which is typical flat ride setup so no surprise there.

It is hard to really recommend something with out a goal in mind. I run a 400/900 setup but I like the front to take set in a corner before the rear. Since I am close to equal suspension frequency I can turn down compression dampening and still have good pitch control for my daily drive and not comprise anything else. I had a purpose in mind so I tuned for this specifically and you should as well….nothing big small things that matter to you.

Originally Posted by aus

Thanks for all the input from everyone here. It's a LOT more than I thought I would get.

Orb, would you recommend 450 lbs front and 900 lbs rear for most street use and a 2-4 track events a year on street tires?

And in regards to the Swift springs, where would you get those and could you use them with a TDK system? Honestly, I'm sure I'm not at a level I would notice.

I wouldn’t recommend what you’re suggesting. I would go with 400/800 setup. The swift spring and thrust sheet fit perfectly on TC system. Harold at HP Autowerks has TC with these spring rates. He sells the TC this way so one stop shopping. Big problem is selecting a decent camber plate and I wouldn’t suggest TC in this regards unless you like noise and replacing bearing every 6 months or sooner.

You will notice the spring quality more than any dampening changes you could ever make. For this car the spring quality and the use of thrust sheets is paramount to anything else...it is a big deal. Ask harold at HP Autowerks who compared...his car is softer and has more grip with 800 lb/in rear than the TC rear spring at 500 lb/in.

Orb

[Radiation Joe]

I strongly suggest that you call TC Kline in Ohio and ask to speak to TC himself. He will be more than happy to discuss his suspension designs with you. Along those same lines, you can get suggestions for a good street/track suspension by calling Turner Motorsports and asking to speak to Will Turner. Call Ground-Control and ask for Jay Morris. James Clay at Bimmerworld is a frequent poster here and has recently come out with street/track set-up (see here). Hell, even Steve Dinan will advise you if you tell him what you want to accomplish. These people are experts at preparing winning race cars and livable street cars. They are approachable and honest.

Do not, under any circumstances, believe equation spewing interneters when it comes to suspension set-up. After these cars have been around for a few years, there will be consensus as to proper set-ups and you might be able to trust what you read. Until then, unless you are experienced in suspension set-up, you should rely on the advice of the vendors.

[aus]

Originally Posted by Orb

I wouldn’t recommend what you’re suggesting. I would go with 400/800 setup. The swift spring and thrust sheet fit perfectly on TC system. Harold at HP Autowerks has TC with these spring rates. He sells the TC this way so one stop shopping. Big problem is selecting a decent camber plate and I wouldn’t suggest TC in this regards unless you like noise and replacing bearing every 6 months or sooner.

You will notice the spring quality more than any dampening changes you could ever make. For this car the spring quality and the use of thrust sheets is paramount to anything else...it is a big deal. Ask harold at HP Autowerks who compared...his car is softer and has more grip with 800 lb/in rear than the TC rear spring at 500 lb/in.

Orb

Thanks again Orb. Would that 400/800 set-up with with the TCK spring or the Swift spring? Any suggestions for rates for the TCK springs?

I'll also give Harold a call and will definitely call TCK before buying.

[Orb]

Originally Posted by aus

Thanks again Orb. Would that 400/800 set-up with with the TCK spring or the Swift spring? Any suggestions for rates for the TCK springs?

I'll also give Harold a call and will definitely call TCK before buying.

As for springs. TC gets there spring for http://www.vogtland-na.com/racingsprings.asp and good quailty spring but not the best. You can see the Swift springs at this site which is worth a read http://www.swiftsprings.com/.

The price for either springs sets are the same and selection is better with Swift. There is no differance in the rate you would put in your car for either brand so this makes no differance.

Certainly give both vendors a call.

Orb

[Radiation Joe]

Originally Posted by Orb

A for springs. TC gets there spring for http://www.vogtland-na.com/racingsprings.asp and good quailty spring but not the best. You can see the Swift springs at this site which is worth a read http://www.swiftsprings.com/.

The price for either springs sets are the same and selction is better with Swift. There is no differance in the rate you would put in your car for either brand so this makes no differance.

Certainly give both vendor a call.

Orb

Nice call on the Swifts. They sound like an improvement without compromise. Lighter weight, less coil binding and (hopefully) more consistent over time.

Any idea on how susceptible they are to relaxation? One of the tests I saw implied that the material has a very high endurance limit, but that might be due to relaxation instead of some fantastic material property. This would manifest itself as sag after some amount of time in a street car.