[RaceComp Engineering]

Originally Posted by 05_GD7

Shortened stockers? Or shorter different kind?

So given these numbers that RCE just posted....thanks for that by the way....If I'm using the RCE "regular guy" spring on stock dampers, what will happen first? Bumpstops or coil bind?

They will be entirely new stops, not just shortened stockers. We will be including stops that will allow for maximum strut travel while still preventing any possible coil bind.

-Dan

[stretch]

Good work, Dan! The revised springs sound much better, as does the inclusion of shorter bump stops. With the inclusion of shorter bump stops, does that mean the springs are now spec'd to lower the car more up front? Or will there be a revision 3 of the Yellows, designed to support more weight but maintain the same ride height? I ask because when you shorten (or remove) a bump stop that is supporting hundreds of pounds, that weight gets transferred to the spring, compressing it further.

I see that your solid length numbers are more than just number of coils * coil diameter, which means they were probably (hopefully) measured much more accurately that what I've been doing. This is exactly why manufacturers should provide data, it's generally much more accurate than the ricer math people like me use. It's good stuff to know, and I hope it's an example that other spring manufacturers follow.

Is there any chance you could measure the total strut travel of the Ohlins? I'm still a little worried that if Ohlins add more than half an inch of travel, that it's just not possible to make a spring that won't bind prior to hitting full compression of the included bump stop. You might bottom out either way, but I'd much rather bottom out on something made of rubber!

[RaceComp Engineering]

Originally Posted by stretch

Good work, Dan! The revised springs sound much better, as does the inclusion of shorter bump stops. With the inclusion of shorter bump stops, does that mean the springs are now spec'd to lower the car more up front? Or will there be a revision 3 of the Yellows, designed to support more weight but maintain the same ride height? I ask because when you shorten (or remove) a bump stop that is supporting hundreds of pounds, that weight gets transferred to the spring, compressing it further.

I see that your solid length numbers are more than just number of coils * coil diameter, which means they were probably (hopefully) measured much more accurately that what I've been doing. This is exactly why manufacturers should provide data, it's generally much more accurate than the ricer math people like me use.

Is there any chance you could measure the total strut travel of the Ohlins? I'm still a little worried that if Ohlins add more than half an inch of travel, that it's just not possible to make a spring that won't bind prior to hitting full compression of the included bump stop.

We have made a slight ride height adjustment to account for the shorter bumpstops so overall ride height will remain the same. We have also been working with Ohlins USA to get all of the specs on the fixed perch struts, including travel, bump stop length, etc. We should have more info on that shortly.

-Dan

[twiSTies]

Thank you RCE for putting your numbers out there!

[stretch]

Originally Posted by RaceComp Engineering

We have made a slight ride height adjustment to account for the shorter bumpstops so overall ride height will remain the same.

Awesome.

This sounds like this is a major redesign of your springs. Sure you want to call 'em "Yellows" still?

Originally Posted by RaceComp Engineering

We have also been working with Ohlins USA to get all of the specs on the fixed perch struts, including travel, bump stop length, etc. We should have more info on that shortly.

-Dan

Awesome.

[Mykl]

Originally Posted by RaceComp Engineering

They will be entirely new stops, not just shortened stockers. We will be including stops that will allow for maximum strut travel while still preventing any possible coil bind.

-Dan

I take it you'll have considered the potentially unique needs of the Ohlins fixed perch dampers as well?




*edit* I see Myles' post now.

[homer09]

i see how the new revisions of RCE springs are better, but they still dont seem to solve the coil bind issues.

stretch, you said stock struts travel about 2-5/8". that's 67mm. both RCE springs bind before that....

[stretch]

Originally Posted by homer09

i see how the new revisions of RCE springs are better, but they still dont seem to solve the coil bind issues.

stretch, you said stock struts travel about 2-5/8". that's 67mm. both RCE springs bind before that....

Indeed I did. That's 2-5/8" at its shortest point. The spring only need to compress to 3-3/8" at its longest point.

The spring perch has a 3/4" recess in which to house that last spring coil- look at the pictures so this makes sense. This makes judging a spring's solid length more complicated because the spring perch is not level. Essentially, the design of the lower spring perch gives you that last half wind of coil "for free", since there'd one less coil at the shortest portion of the spring perch.



If the Black's were still 78.38mm at their shortest point, they would be too long. However, even 5 coils at 13.75mm each equals 69mm. The 78.38mm figure is probably inclusive of rubber insulators and that 3/4 inch recess in the spring perch (which prevents a little compression). If the top coil of the spring is ground down (as is common), I think they'll be OK.

Edit: I just noticed something after looking at my above picture. I said earlier that changing the shape of the spring would help, and sure enough, the spring has a very slightly decreasing diameter. This means the coils are not stacked perfectly vertically and explains why coil bind doesn't happen as soon as I would have expected on the RCE Yellows (though I'm sure it still happens, they're very far off). It also means calculating the springs' solid lengths is more difficult! Varying the diameter of the spring is actually a trick to get coil bind to be LESS noticeable in the event that it does happen, go figure!

[RaceComp Engineering]

Originally Posted by homer09

i see how the new revisions of RCE springs are better, but they still dont seem to solve the coil bind issues.

stretch, you said stock struts travel about 2-5/8". that's 67mm. both RCE springs bind before that....

There are a few things to consider with that:

1) This assumes that Stretch's measurements are completely accurate. The methods that were used to measure are good for giving a rough estimate of strut travel but they are by no means exact, especially when you are talking about a variation of a few millimeters.

2) You also have to take the bumpstops into account. By using a shorter, progressive bumpstop you change the characteristics of the strut as it approaches maximum stroke, or rather as it approaches the point in its stroke where a spring could potentially bind. When you are talking about fairly tight tolerances, the bumpstops can play a large role in whether or not the springs will bind.

3) Just because a spring can potentially bind on paper, this does not necessarily mean that they will in the real world. Considering the solid length of these springs subtracted from the free length, as well as the rates, it would take a LOT of force to cause full compression.

-Dan

[homer09]

wouldnt the end all proof consist of two pictures:

- one with an assembled front strut without a spring, compressed fully
- one with an assembled front strut with X spring, compressed fully

if both pictures show the same total height, spring bind is not an issue. this would obviously require some sort of press to compress a fully assembled strut/spring/

[RaceComp Engineering]

Originally Posted by stretch

Indeed I did. That's 2-5/8" at its shortest point. The spring only need to compress to 3-3/8" at its longest point.

The spring perch has a 3/4" recess in which to house that last spring coil- look at the pictures so this makes sense. This makes judging a spring's solid length more complicated because the spring perch is not level. Essentially, the design of the lower spring perch gives you that last half wind of coil "for free", since there'd one less coil at the shortest portion of the spring perch.



If the Black's were still 78.38mm at their shortest point, they would be too long. However, even 5 coils at 13.75mm each equals 69mm. The 78.38mm figure is probably inclusive of rubber insulators and that 3/4 inch recess in the spring perch (which prevents a little compression). I think they'll be OK, even if it's very close.

Edit: I just noticed something after looking at my above picture. I said earlier that changing the shape of the spring would help, and sure enough, the spring has a very slightly decreasing diameter. This means the coils are not stacked perfectly vertically and explains why coil bind doesn't happen as soon as I would have expected on the RCE Yellows (though I'm sure it still happens, they're very far off). It also means calculating the springs' solid lengths is more difficult! Varying the diameter of the spring is actually a trick to get coil bind to be LESS noticeable in the event that it does happen, go figure!

This is another thing to consider. If you do a simple calculation of the solid height of the new Yellows using coil count and diameter, you get 64.8mm, whereas the actual solid height is 71.34mm. I think this is a result of the offset angle that the spring is wound at, as opposed to being perfectly vertical. Nobody ever said this stuff was simple...

-Dan

[Splash]

Heh, what you need, is a blown front strut so the shaft is easy to move. compress the shaft, have a 300lb guy put his weight on the upper perch, and measure the distance between the perches.

I've been measuring springs at their tallest points, so the perches should be measured that way too.

[stretch]

^^^ Please don't ever assume my measurements are accurate. I round.

I did try to give a fair estimate of peak bump stop compression, though. If anything, a shorter or softer bump stop will permit more total compression and thus require the spring to have an even shorter solid length.

[D1SMember]

wow...good read very informative. I still don't know what springs I want to buy though. I really wanted to get the yellows but I think I'll hold off for a little to see how this revision pans out. I love this forum. You guys know your $H!T. Which is good for someone like me that would have never known any of this. I'm going to keep a close watch on this thread. Any suggestions on springs? I have heard a lot more good than bad from RCE springs but coil bind is not cool. Do you guys think the revision is sufficient so far or should I look else where. Thanks

[05_GD7]

Well from the sounds of it, RCE has addressed these problems. I'm still moving forward for RCE blacks.