I have been following this for a long time and maybe someone could clue me into something I may have missed. I have 03 Sedan with Eibach Prokit, sways and D-Specs. Sways set full soft F and med in R. D-specs 4 turns from full hard F and 4.5 in R. Looking for better performance. Read a lot here about 350Z H-Techs and RS*R down. Not sure if I want to make investment in full coils for street since I have already spent enough. Spoke directly to TEIN about 350Z H-Techs and they advise that spring is progressive?? Everything I read here from the gurus says linear. What is the truth? Any advice from those who have either of these springs on sedan is appreciated in terms of camber problems, comfort, performance. Leaning toward H-Techs but unsure. RS*R sounds great, but may cause other issues with drop. Please advise. Thanks.

 

based on what Gsedan35 said, I assumed they are linear rate.

 

I spoke directly to the engineers @ TEIN, Tim@Tein.com, and they said that all of their springs are progressive. Anyone have any advice on these springs?

 

In all the conversation's I've had with the tech's at Tein on the phone, none of them have ever said the rear springs on any G or Z application were anything buy linear, which they in fact are.

On the specific point of 350Z H-tech's they have twice said the front spring is progressive. However, they are in fact no more progressive then the oem front springs are. Unlike all other G and Z Tein spring application's, they do not use progressive coil's that are wound tightly in order to bind and theirby change rate.

Tein 350Z H-tech springs are all linear. I took pics of the springs for the express purpose of pointing out the error of what Tein is saying the front springs are.

In the most technical sense, since all springs that use the oem upper mount will see the spring change their outside diameter from the bottom to the top, they are slighly progressive. Since they will not offer up much rate change and will NOT do so with a sudden change, we consider the oem springs linear. The front springs on Tein Basic coilovers are this way, and Tein considers those springs as linear.

Tein 350Z H-tech front spring


Tein 350Z H-tech next to a oem spring


Notice in this picture of 350Z S-techs that the two left springs have coils at the very top that are tightly grouped together, they will bind in use and cause a rate chage, meaning they are progressive. All other G and Z Tein lowering springs feature this construction.


This is a picture of a Tein Basic front spring, they are sold seperately under the standardized spring catagory as taper type springs

Notice that the top of the spring is wider then the bottom.

 

You can go either way with RSR 350Z down springs or 350Z H-techs. Either spring will be vastly superior to the Eibachs your running now. The RSR's will give you a greater drop amount and while the resulting camber settings will be in a more performance oriented vain, they will be in the high side and certainly out of oem sedan alignment specs by a good margin. If the nature of your corning are speeds above 45mph, I'd argue you may be fine. But for speeds less then that where you'll see higher steering angles and caster induced camber effects, whole car aftermarket camber fixes would be a very good idea to ward off excess inner tire wear.

The H-tech's have a slignly greater front spring rate, with will help a bit in reducing camber change due to roll. And frankly, since they undercut the RSR in price point, you can use that price differance to score a set of oem 2005 350Z springs. Use the oem 2005 Z rear springs to test if going higher in rear spring rates gives you a meaningfull improvement, or if it's a liability.

I have been on 448lbs front rates and run the rear at 375, then 427 and then to 342. In town where corners are taken at speeds lower then 45mph, understeer is a lot higher. However, when cornering speeds are higher, balance if fine and traction at corner exit is better. Since most of my fun is in town, not sure if I'll stick with the 342lbs rear rate, but I do not have enough testing time yet to make a change.

 

I agree with what you are saying and what you are so nice to provide visual evidence of. I have been following many of your suspension posts and I am glad you answered. I can't understand why one of TEIN's own would tell me otherwise, the reason for my original post. Now in terms of the RS*R and 350Z H-Tech. Like you, most of my driving is done in and aroung town and on the freeway, not at track, althought I am exposed to some nice twisties where I live. Since I am use to the higher progressive spring rate of the Eibachs do you think the H-Techs will feel too soft for me as compared to the RS*R with a higher rate? I notice you mentioned the OEM 350Z rear springs matched with the front H-Techs. Is there a problem with rear H-Techs? I really am considering going with the RS*R, but like you said in slower speed
turns, camber could be an issue.

 

Pretty sure that every single tech that will anwer the question is reading from the same source. Asking that person to go grab a front spring and tell me the same thing, is totally different. One thing that might not help is that in Japan the H-tech for the Z is a progressive spring with spec's that match the USDM S-tech for the Z, go figure. Maybe someone forgot to mention that the USDM H-tech spring ditched the progressive bit, I dunno.

The Eibach's peak rates are 334 front and 417. However, you have to work past the softer inital spring rates to get to the higher final rates. You give up turn in performance and resistance to brake dive and squat during acceleration. Neither the RSR or H-tech springs have a softer rate the car has to work past and when your at or close to the limit's of adheasion, all corners of the car are on the same spring rates, so every corner is on the same page.

Their is nothing wrong with the 375lbs rear Tein rates, just pointing out that with the Tein's lower price point you could make for a 358lbs front rate 427lbs rear rate combo by picking up a set of oem 2005 Z springs, if you wanted to and still be at or below the RSR down spring option, with a bit more ride height to boot.

 

Understood. Where do you get all this info? I received another e-mail from TEIN stating that "people assume our springs are linear because the information in our catalogs gives one spring rate, but rest assured our springs are progressive". I am sending them the pics you provided. I have seen in your sig that you have worked with the 350Z H-Techs on your sedan. How do you like the drop? Eibach lists drop of 1.1 F & R but looks like more, I failed to measure. Do you think OEM Z springs will drop more than 1" because of increased weight of sedan? Same with H-Tech and RS*R because they are designed for Z, which is roughly 200lbs. less?

I feel that all springs listed here will increase my driving experience, I now just need to avoid serious geometry problems. Since I already have Eibach sways and D-specs, this is the last piece for my puzzle. No camber adjusters if I can avoid it and I don't want to invest in coils. Leaning toward H-Techs, but concerned if drop is enough. Like drop of Eibach's, but could go more. I have had no camber issues with Eibach's. I think I need to get more info from G_Monster on RS*R. Didn't he do this setup on his sedan?

 

Gsedan35, I have purchased the RSRs for my G35 sedan as per our emails earlier this year... But I have not yet installed them, I was wondering about tire wear...Most of my driving and cornering is in clovers at around 40-50mph on the freeways, if I don't do the front a-arms will my tire wear on the front tires be bad enough to cause me to replace the tires prematurely? also, I plan to do the rear camber bolts. I would rather not spend the $400 on a-arms, but if it saves me $ in tires in the long run it will be worth it...One more thing... What is the drop I will see in my sedan with the 350z RSRs again? Thanks again for all your help and knowledge!

 

From what has been posted I believe your drop will be 1.6 F and R. Please let me know what your impressions are after your install. I just purchased 350Z H-Techs and have yet to install. I am hoping to avoid major camber issues while maintaining good ride comfort, improved handling and same drop as the Prokit springs I am replacing. I was considering RS*R, but did not want to have to make larger investment in A-Arms up front and camber kit in rear. Please let me know how everything goes after install. Thanks.