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Discussion Starter #1 (Edited)
Hi folks,
Happy new year to all!

I recently put in GC coilovers on my beast.
One issue I have is the bottoming out of the front suspension on any harder bumps or dips in the road.
It's VERY jarring - a very loud bang!
I had the fronts raised a little and the top part of the coil thread was cut to allow a little more suspension travel and it is a little better now but it still does it.

Is this normal?

I also read on this board that I may have an issue of wheel fitment clearance if I run wider rear rims on the front.
I just picked up a set of rears that's waiting for the snow to clear before they go on.

I appreciate you responses.

2000 Ti-Sil/blk.
Rogue SS, front clears, SS brakelines, GC coilovers.
Next to do is Stoptech fronts
 

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DavidsM5 said:
Hi folks,
Happy new year to all!

I recently put in GC coilovers on my beast.
One issue I have is the bottoming out of the front suspension on any harder bumps or dips in the road.
It's VERY jarring - a very loud bang!
I had the fronts raised a little and the top part of the coil thread was cut to allow a little more suspension travel and it is a little better now but it is still do it.

Is this normal?

I also read on this board that I may have an issue of wheel fitment clearance if I run wider rear rims on the front.
I just picked up a set of rears that's waiting for the snow to clear before they go on.

I appreciate you responses.

2000 Ti-Sil/blk.
Rogue SS, front clears, SS brakelines, GC coilovers.
Next to do is Stoptech fronts
Are you using spacers on the front? I had to put 10mm spacers on when I did the H&R coilovers. Pull off the front wheel to see if its rubbing on the coilovers.
Boz
 

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I did a test drive with chunpng's M5 and encountered this bottoming out and loud clunk issue. You may want to send him a PM and find out if there is anything he has done (other than raise the ride height). I don't know how much customer support you can get directly from Ground Control, as they don't seem to excel in that area.

The bottoming out issue and customer service issue was what made me go with the Dinan Stage 3 suspension. I was a potential customer for the Ground Control and would have done it, but had concerns after trying it.

Please post if you do get a satisfactory solution to this.
 

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How low is your car compared to stock? What settings do you have the front shocks set to? I have bottoming out on the bumpstops, but only over VERY severe bumps and maybe one spot on the track if I'm going hard. During normal usage it's fine.

The wider rear wheels will clear with 2-3mm of space (depending on tire choice) with the GC coilovers with no problems if you use the proper 3mm spacers and longer lug bolts.

Once you get the GC setup dialed in, you will really love it.
 

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The clunk is somthing Ive heard many times with many GC systems.
 

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I know my friend had similar problems with his on his M3, only the bang would occur in the rear.

We figured the issue out to be the fact that GC sent the wrong spring with the kit and as a result a gap would build in the suspension and the bang would be the space created by the short spring being filled and then created again.

I would check that out as he had some fairly serious control arm damage as a result.
 

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Discussion Starter #7
Redshift,
As you can see by the photo I just took, it's not too low.
It was raised a little from the original setting.

Do I really need longer lug bolts with the 3mm spacers?

As for tire choice, I'm putting the Dunlop race tires that I just picked up from Tirerack.

And I also just ordered the Stoptech front brakes from (and thanks to) Dave Z;)
Daym! This board is costing me $$$.

David in Toronto
 

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David, that looks to be around 1.0" - 1.5" lower than stock, like mine.

Yes, you really do need longer lug bolts with the spacers to make sure that you have enough thread engagement. You are putting extra stress on the front suspension and you need all the help you can get! Don't skimp here. :)

Dunlop SP Sport Race tires in 265/35/18 I assume? Good choice!

Your setup will be identical to mine once you get the tires, StopTechs, and if you also do a Dinan rear bar along with SSR Comp wheels. Do you plan to take it to the track? I have a friggin blast in mine. People are always amazed at how I can outrun, outbrake, and outcorner them in a 4400lb (with student) car.
 

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Discussion Starter #9
Redshift,
Yes, tracking the car is part of the plan.
Yes, I picked up the 265/35-18 Dunlops, great deal.
Found out about those through this board too!
It would be interesting to see how they compare to the Hoosiers I had last year.
Would you believe that the Hoosiers are 6 seconds a lap faster than the stock tires on a 2 min 5 sec track!!

I plan to order the Dinan rear sways ASAP and perhaps the sway bar bracket?

David
 

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Oops, I forgot to mention that bracket. Yes, the Beast Power brackets are a must have item.

Yes, I would believe the Hoosiers are that much faster. They are much stickier tires. I would guesstimate that you will lose maybe 2-3 seconds from the Hoosiers with the Dunlops. The upside is the price and much longer life, plus they are street legal and run great in the rain as well.

You enjoy and be safe! :cheers:
 

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DavidsM5 said:
Hi folks,
Happy new year to all!

I recently put in GC coilovers on my beast.
One issue I have is the bottoming out of the front suspension on any harder bumps or dips in the road.
It's VERY jarring - a very loud bang!
I had the fronts raised a little and the top part of the coil thread was cut to allow a little more suspension travel and it is a little better now but it still does it.

Is this normal?

I also read on this board that I may have an issue of wheel fitment clearance if I run wider rear rims on the front.
I just picked up a set of rears that's waiting for the snow to clear before they go on.

I appreciate you responses.

2000 Ti-Sil/blk.
Rogue SS, front clears, SS brakelines, GC coilovers.
Next to do is Stoptech fronts
Your car looks too low in the front to prevent bottoming with linear streetable springs. The fender lip to roundel center distance should be greater than 13-1/2"...14" is probably optimal. In addition, soft-ish damper settings will promote bottoming. What is your damper setting?

What are the rates?? For E39 V8, GC has been selling everything from 350 to 500lb/in.

Need this info before offering opinion.
 

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Redshift,

Do you experience the same noises etc.?


Redshift said:
David, that looks to be around 1.0" - 1.5" lower than stock, like mine.

Yes, you really do need longer lug bolts with the spacers to make sure that you have enough thread engagement. You are putting extra stress on the front suspension and you need all the help you can get! Don't skimp here. :)

Dunlop SP Sport Race tires in 265/35/18 I assume? Good choice!

Your setup will be identical to mine once you get the tires, StopTechs, and if you also do a Dinan rear bar along with SSR Comp wheels. Do you plan to take it to the track? I have a friggin blast in mine. People are always amazed at how I can outrun, outbrake, and outcorner them in a 4400lb (with student) car.
 

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See above :)

Redshift said:
I have bottoming out on the bumpstops, but only over VERY severe bumps and maybe one spot on the track if I'm going hard. During normal usage it's fine.
 

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Thanks Redshift!

I wonder if it is an installation issue for the others? Or what the issue is? Maybe the settings?

Your situation sounds just fine and I really like your ride height. :cheers:

Bill has just sent me pictures of my GC. See enclosed. I will do a more complete write up about what we are going to be doing after the game is over or in a day or so.

GO USC!!!!!!!!!

P.S. These things look just awesome! :eek: I am in love . . . hiha

Did I say Go USC? :hihi:


Redshift said:
See above :)
 

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