GC c/o's guys, need your input on coilbinding

[///Manuel]

I current have the track/school setup with 450front / 6" 525rear spring setup. Well since I installed the setup I'm getting minor coilbind from the right side. Ride height is at 11 3/4. With stuff in the car, it coilbinds very easily. I used to have 2 5/8" worth of bumpstops. GC increased it by 3/8's after I told them about the problem but even with 3/4" more I still get coilbind. I'm gonna try to add even more bumpstops to see if that gets rid of it after some point.
I'm driving more and more aggressively on the track and actually got it to happen over a fast transition (with a dip/bump in the middle), noise was stronger with people in the front passenger seat. I'm still running street rubber, I'm sure as soon as I run race rubber I'll be out of luck!
How much bumpstop do you guys run? What rear spring setup do you have? This is starting to bother me quite a bit during a testing I went thru a dip sideways accelerating in 1st and the rear got loose after coilbind... not good.

[frayed]

This is starting to bother me quite a bit during a testing I went thru a dip sideways accelerating in 1st and the rear got loose after coilbind... not good.\

Don't look to your suspension setup to save your ass in situations like this.

The bottom line is this: for max perfromance, you should adjust your bumpstop length to give *just* enough to prevent coilbind but not too much so as to cut into your suspension travel.

I'd suggest pulling out all your bumpstops, measuring how much travel you have at your rear shock from static ride height to full coilbind, and adding enough bumpstop to provide 3/4" of 'crush'. I used plumbers putty on the rear shocks to measure travel.

1/2" of crush and you can still get coilbind under normal driving on shitty city streets. 1" is too much. I found around 3/4" to work well to prevent Big Nasty Sounds from coilbind

[///Manuel]

Perfect! I'll try to figure that out. I just started to feel it on the track as I get faster I was able to go through a transition leaving the throttle down and going thru that dip I got coilbind.
Now, the weird thing is that it seems to happen on the right side only, the left side is perfectly fine (and that's the side that sees the most g's at the track). I guess it's measurement time, thanks for the tip!

[Sacramento M3]

Can anyone take the time to explain what coilbinding actually is for those of us that don't track our cars yet? I've searched the track forums among other places and no one has actually said what it is. I think I generally have a good idea of what happens during coilbinding but I want to know for sure. I want to make sure the suspension I go with will not present this problem in the future.

Thanks!

[John in Houston]

Originally posted by Sacramento M3
Can anyone take the time to explain what coilbinding actually is for those of us that don't track our cars yet?Thanks!

Picture your spring in your hand. Notice how none of the coils are touching?

Now, picture the spring mounted in your car. With 'zero' bind, all coils will be 'free' as in not touching. When coil bind occurs, the coils of the spring (one or all) are actually touching each other.

Now, some springs / suspension setups are designed to have some coil bind... others are designed to have none. In most instances, true coil-over setups are designed to have zero coil bind where as factory coil-over setups, and other setups sometime utilize coil-bind to generate the desired spring rate.

A good example of this is the H&R sport springs in the rear of an M3/2. If you look at the spring after install, the lower two coils are touching... thus bound.

[d4nn]

I've been wanting GC coil-overs for awhile & I've noticed that all of GC owners have coilbind issue.

I know that most of GC owners later got the problem fixed. However, I'm questioning the GC's engineering now.

Honestly, I'm not mechanically inclined. I read Frayed's solution on the coilbind issue & I swear to God that I've no idea what Frayed's talking about.

Is there any alternatives that dont require pulling out bumpstop, measuring the travel, & re-design it @ your own risk?

Thanks,
Danny

[Sacramento M3]

Well I will be going with the H&R Race Springs with my Bilstein Sport Struts and shocks. Does anyone know if there is some coilbind designed into this setup??

Thanks!

[M3RACER]

Originally posted by d4nn
Is there any alternatives that dont require pulling out bumpstop, measuring the travel, & re-design it @ your own risk?

Thanks,
Danny

I originally had coil bind issues with my GC kit, looks like they made a mistake at one point but it has been corrected. If you have any problems with the kit just give them a call and they'll be more than happy to correct for you. If you have been following these boards long enough you realize frayed is a hands on type guy, he din't have to go through all that work himself, I think he really enjoys it.

[frayed]

yeah, I'm a freak. Even Jay (the owner of GC) asked me one day when we were shooting the shit, 'your wife puts up with you tinkering around with your car all weekend?!'

To my knowledge, the reason why there was a coilbind issue is that a whole bunch of kits got sent out w/o enough bumpstop. It is my understanding that this has now been addressed.

[Cannon]

I have a GC/AD setup (500/550) and haven't had any coil bind problems.

[badmonkey]

Originally posted by d4nn
I've been wanting GC coil-overs for awhile & I've noticed that all of GC owners have coilbind issue.

I know that most of GC owners later got the problem fixed. However, I'm questioning the GC's engineering now.

Honestly, I'm not mechanically inclined. I read Frayed's solution on the coilbind issue & I swear to God that I've no idea what Frayed's talking about.

Is there any alternatives that dont require pulling out bumpstop, measuring the travel, & re-design it @ your own risk?

Thanks,
Danny

I haven't had any problems either. Installed, set and forget. The only question I may have is the use of 6" springs rated under 550#'s on the rear, which seems to be the common link amongst those having problems with coil binding. Haven't done the math, so I couldn't say for sure. Just a thought...

///badmonkey

[///Manuel]

Yeah I had 2" & 5/8's bumpstop to start with. Received an extra 3/8's, added that on for a total of 3" & 1/8's. Same exact coilbind sound (identical intensity). Added both 3/8's on the culprit side, still coilbind. So I'm getting coilbind with 3" 1/2 bumpstop. I haven't calculated yet how much travel that leaves me but since it doesn't help the coilbind, I'm probably getting very low travel... sux. Now, the weird thing is that I get it on the right side ONLY!, that is weird by itself, don't know...

[badmonkey]

Are you sure you're not just riding on bumpstops?

[///Manuel]

It really sounds like a knocking noise. I had my girlfriend drive the car at full throttle in a straight line in 2nd gear. Going over a bump on the road (took a while to find the right spot), there is a knocking sound coming from the right spring. Looking at the spring, it looks like coils bind only on 1 side towards the rear of the car. Also when I went thru a dip accelerating in 1st I heard the noise and felt the rear getting slightly loose while turning.
Can anybody give me their bumpstop lengths?

[ebm34]

The problem with coilovers is that the optimal bumpstop length depends on the desired ride height. Raise the ride height, and the springs will coilbind. Lower the ride height and suspension travel is reduced. I don't know if getting bumptop lengths from others is the best idea because there are too many variables. For example, what about the white plastic washer in the strut? The Koni bumpstop? The black rubber thingy in the koni, and the height (type) of the RSM being used. A variation of 1/2 inch could be the difference between coilbinding and no coilbinding. I think if you're really interested in creating the optimal setup with your spring selection, you need to manually go through all the measurements as frayed suggested. If you don't feel like doing that, you can try lowering your rear ride height until the coilbinding is gone. The height you lowered by is appr. the length of bumpstop you'd need to add with your original ride height.

[John H]

ok, guys, i guess I really don't understand this :-/. I had started another thread about coilbinding a day or two ago (http://www.bimmerforums.com/forum/sh...&postid=548947 ) and the consensus from frayed (who seems to be the most knowledgeable on this subject) is this:

1. increase thinckness of upper spring perch or add to bumpstop to reduce coil bind (while presumably lowering lower spring perch, so that ride height remains constant) to get rid of coil bind.

2. do the opposite to increase suspension travel.

3. the "maximum performace" setup is where the springs just barely don't coilbind.

My question is this: How in the world does moving where the spring sits in relation to the strut tower/strut assembly make one bit of difference in regards to coil bind?

It seems to me (and my mechanic concurred) that you are just moving the spring up or down, but it should keep the same shape for a given ride height.

Maybe bumpstops do something more complicated, but given I have bilstein struts, the bumpstops are internal (so i hear) and can't be modified. Even so, I guess I still don't understand how bump stops would make a difference here.

I've thought about this long and hard, and it still doesn't make sense to me how one camber plate gives coil bind and a different thickness one doesn't (assuming you've changed the lower spring perch to keep ride height the same for both).

Really guys, I apologize in advance for my slowness here; clearly there is something major here I am failing to comprehend. Any insight would be greatly appreciated!

Cheers,
John

[frayed]

Originally posted by John H
ok, guys, i guess I really don't understand this :-/. I had started another thread about coilbinding a day or two ago (http://www.bimmerforums.com/forum/sh...&postid=548947 ) and the consensus from frayed (who seems to be the most knowledgeable on this subject) is this:

1. increase thinckness of upper spring perch or add to bumpstop to reduce coil bind (while presumably lowering lower spring perch, so that ride height remains constant) to get rid of coil bind.

2. do the opposite to increase suspension travel.

3. the "maximum performace" setup is where the springs just barely don't coilbind.

My question is this: How in the world does moving where the spring sits in relation to the strut tower/strut assembly make one bit of difference in regards to coil bind?

It seems to me (and my mechanic concurred) that you are just moving the spring up or down, but it should keep the same shape for a given ride height.

Maybe bumpstops do something more complicated, but given I have bilstein struts, the bumpstops are internal (so i hear) and can't be modified. Even so, I guess I still don't understand how bump stops would make a difference here.

I've thought about this long and hard, and it still doesn't make sense to me how one camber plate gives coil bind and a different thickness one doesn't (assuming you've changed the lower spring perch to keep ride height the same for both).

Really guys, I apologize in advance for my slowness here; clearly there is something major here I am failing to comprehend. Any insight would be greatly appreciated!

Cheers,
John

Hmm, being the most knowledgable about anything sounds suspect and dubious to me.

Anyway, as to 1: Increasing spring pad thickness will cause more coilbind. As ride height is increased, coilbind issues become more severe (in the rear). Up front, it's the opposite.

3. Yes, absolutely. You want to use every inch of travel you have, and implement *just enough* bumpstop to prevent coilbind.

I'll respond to your other issue in a bit, gotta go make dinner.

[d4nn]

I just called up Jay today & ordered the Track/school setup.

Jay said that they've stopped being too greedy on the precision, so nobody should have any coilbind issue.

I'll see how it goes.
Danny

p.s. Frayed, you rock.

[CABimmer]

Seems like there are a lot of the GC threads running. I have the 6in frnt and 5.5 rear with the new rear koni shocks. got it a few weeks ago. I have not had any coilbind. but have hit the bumbstops a few times on spead bumps. Real sharp ones.

[John H]

Originally posted by frayed
Hmm, being the most knowledgable about anything sounds suspect and dubious to me.

Anyway, as to 1: Increasing spring pad thickness will cause more coilbind. As ride height is increased, coilbind issues become more severe (in the rear). Up front, it's the opposite.

3. Yes, absolutely. You want to use every inch of travel you have, and implement *just enough* bumpstop to prevent coilbind.

I'll respond to your other issue in a bit, gotta go make dinner.

ok, frayed, first off, thanks so much for the response.

second, i think i am beginning to get this now. correct me if i am wrong (which i probably am).

so my bilstein struts have internal bump stops that serve the purpose (or rather have the effect) of making it difficult for the shock to bottom out. they are internal, and i can't modify them. they make the suspension slightly non-linear (since theoretically the spring is linear all on it's own, and the bump stop would make the force needed to compress the shock/spring combo further even harder.

now where the spring actually sits relative to the strut tower, within some reasonable range, is basically irrelevant (as I said my mechanic and I had decided in my earlier post). this makes sense to me.

however, the shock attaches to the shock top/strut tower at some definite point. the bottom line is that this point is now ~7/8" higher with my GC plates than with my stock shock tops. the result is, for a given ride height, the shock is now extended ~7/8" more than it used to be when at rest.

thus now, with my GC plates installed, if i go over a bump, the shock has 7/8" more to travel before it hits the bump stop. this extra travel allows the spring coils to touch more easily, thus giving me a coilbind problem.

so, now to the solution: ideally, i need to find some way to lower where the top of the shock connects to the GC plates by ~7/8". where the spring sits doesn't matter as much. this may be hard to do however... maybe i could make custom shims and machine a big hole in the center and place it between the GC plate and the strut tower.

the slightly less ideal solution might be to make my own external bump-stop (thus totally incapacitating the internal one). this is less ideal though because i still run the risk of topping out my suspension, and presumably my jerry-rigged bump stop will not be as good as what the engineers at bilstein decided to put inside my shock.

ok, so this makes sense to me now. i'm now ready for you to tell me why it's all wrong and i can start over again .

really, thanks for your patience with me on this.

cheers,
john

[frayed]

John,

You have it all right.



I don't have experience with the Bilstein bumpstops, however. Maybe some Bilstein people can speak up here to clarify on the internal nature of the bumpstops. Konis and stock both have external bumpstops; while I know the Bilsteins do have internal ones, I was under an impression that they had external ones as well (under the dust covers, which cover the strut shaft).

If they are completely internal, then yeah, I'd say that an add-on external bumpstop is a bandaid and not ideal.

Looking past the bumpstop issue for a moment, let me say this. More travel is good. Really, really good. This is a primary benefit of camber plates. So, my solution to your problem would be to run longer, linear rate springs. Get the suspension travel that you deserve having spent the cash on camber plates, fine tune your front rates, and convert to a linear setup all in one fell swoop. I'd do the same for the rear. Ping kitwetzler or MRob for more info, as both have gone in this direction with their HR c/o's. I think the Bilstein dampers on the HR setup are fine; they just need more spring and true linear rate springs to upgrade their performance.

Alternatively, you could run down to the hardware and get a 1/2" stack of washers for each strut to shim your top spring perches.

I'd call GC on this issue. Jay, I know for a certainty, is keenly aware of the issue. B/c of the HR c/o installed base, the new hybrid street/track camber plates they now make maintain factory stack height to avoid the issue you are running into.

Finally, my HR coilovers would coilbind with stock camber plates (aka strut hats) lowered only 1". Not a big booming coilbind, but enough to rub off all the paint at contacting coil surfaces. This leads me to believe that the HR c/o's don't have enough spring.

Anyway, those are my thoughts, albiet after a few pale ales and a big dinner with too many carne guisada tacos.

[John in Houston]

If you are running Bilsteins on an M3, it should have come with an external bumpstop (yellow, approx 2" tall) as well as an internal bumpstops (brown, looks like a turd, 3.5" tall).

Now, I'll talk from my setup as this is what I am most familiar with:

98 M3, Stock strut mounts, Bilsteins and H&R sport springs.

With the external bumpstop installed, the car was on the bumpstop before I even had weight on the suspension. Removed the external bumpstop and gained 2" of travel. Now, the car is almost at the internal bumpstop at rest.

You can modify the internal bumpstops on Bilstein struts. Quite simple (although I have not done mine yet).... Remove the strut assembly from the car. Flip the strut over. You'll see a bolt and a lock-nut on the bottom of the strut. Remove the nut and screw the bolt into the assembly (you will most likely need heat as there is lock-tite and paint on the assembly). Be careful not to damage the threads or touch the strut shaft. Once the assembly is turned all the way in, the inner strut assembly can be removed. The internal bumpstops are at the bottom of the assembly and should consist of 3 equal segments (looks like a turd... seriously). I plan on removing 1 segment.

Reassembly is the reverse of above.

This should increase your strut travel by 1.5 inches... more than enough to keep you off the bumpstop.

[John in Houston]

It should also be noted that what alot of people think is 'coil-bind' may infact be running out of strut travel and sitting on the bumpstops.

If your spring is capable of compressing more than your strut / shock... this is precisely what is going to happen.

Shoe polish (or a different color paint) is an excellent diagnostic tool in this arena. Place some on the offending bumpstop and / or coils and then go drive agressively. Then all you have to do is check your paintwork. If the bumpstop shows signs of missing paint / polish, then you found the culprit. If the coils show signs of missing paint / polish... there you go.

Easy and cheap to identify.... much harder / expensive to correct.

[John H]

Originally posted by John in Houston
It should also be noted that what alot of people think is 'coil-bind' may infact be running out of strut travel and sitting on the bumpstops.

Thanks John and frayed for the info. John, yes it is coil-bind... i've done the spring experiment before to check.

frayed, I'll take your advice and call Jay at GC tomorrow. Definitely that sounds like the better plan (get taller springs). I am assuming taller springs have greater travel without binding by design (i.e. the same number of coils, but spread out more allowing for more compression). also, I'm assuming I won't have topping out problems by extending my shock ~7/8".

it seems like the other plan is to get bigger bumpstops from bilstein, but i like the spring idea better. i like the idea of getting a more linear setup .

frayed, you mentioned doing the same thing in the rear... i am not sure how I would do this unless what you mean is i should cut my bilstein bump stops and get a taller spring there too. the problem is the rear isn't height adjustable, and my rear end would then be sitting pretty high I would think. i'll see if I can talk to kitwetzler (i actually talked to mrob over the weekend) if GC doesn't know for sure.

Thanks a lot guys again! I think I finally understand this

Cheers,
John