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up-grade suspension bottoming out...? by hypo327
Started on: 02-11-2014 05:32 PM
Replies: 11 (246 views)
Last post by: Silicoan86 on 02-13-2014 09:54 PM
hypo327
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Report this Post02-11-2014 05:32 PM Click Here to See the Profile for hypo327Click Here to Email hypo327Send a Private Message to hypo327Edit/Delete MessageReply w/QuoteDirect Link to This Post
My late run '86 GT (basically an '87) bottoms out when I hit small sharp bumps, drop-offs or pot-holes, etc. Here are my specs: The '87 up-grade 15"x 7" simulated spoke wheels, with Falken 215/60R15 on the front and 224/60R15 on the rear. Eibach 1.5" lowering springs all around, and KYB struts and adjustable shocks, and polly bushings throughout. The ride is nice with the typical sport car stiffness, but the Falken tires send all vibrations on bumps into the car. Is there a solution to stop what feels like bottoming out bang??? Could the hard tough Falken tires be the culprit?
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Steven Snyder
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Report this Post02-11-2014 06:00 PM Click Here to See the Profile for Steven SnyderClick Here to visit Steven Snyder's HomePageClick Here to Email Steven SnyderSend a Private Message to Steven SnyderEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did you raise the bump stops when you installed the lowering springs? Look here: http://www.westcoastfiero.c...front_bump_stop.html
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rogergarrison
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Report this Post02-11-2014 06:28 PM Click Here to See the Profile for rogergarrisonClick Here to Email rogergarrisonSend a Private Message to rogergarrisonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Id say the unmodified bump stops and the poly bushings are the reasons. 60 series tires have an adequate sidewall height to absorb a lot. 70s are even better. The rule goes with the lower the profile tire, the harsher the ride. I think you have a good compromise tire size. Thats whats on my Sebring and my Ferrari kit, and they both ride pretty nice as well as handle good.
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hypo327
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Report this Post02-11-2014 06:34 PM Click Here to See the Profile for hypo327Click Here to Email hypo327Send a Private Message to hypo327Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Steven Snyder:

Did you raise the bump stops when you installed the lowering springs? Look here: http://www.westcoastfiero.c...front_bump_stop.html


I'm not sure, since I did not install them, but I will definitely check them out. Thanks so much. I've got a sneaking suspicion that that's the problem. Thanks!
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Steven Snyder
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Report this Post02-11-2014 06:47 PM Click Here to See the Profile for Steven SnyderClick Here to visit Steven Snyder's HomePageClick Here to Email Steven SnyderSend a Private Message to Steven SnyderEdit/Delete MessageReply w/QuoteDirect Link to This Post
For what it's worth, I didn't notice any difference in ride quality when switching from rubber to poly bushings when my car was otherwise stock.
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hypo327
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Report this Post02-11-2014 06:51 PM Click Here to See the Profile for hypo327Click Here to Email hypo327Send a Private Message to hypo327Edit/Delete MessageReply w/QuoteDirect Link to This Post
Just as a foot note: I just got through making a 1300+ miles trip to Fallbrook, CA from up by the Canadian border in Washington state. The ride was fine except for the hard tough Falken tired that transferred all the little bumps, cracks and rough road surface up into the car. Not the best ride and lots of road noise. I pulled into a 76 station to gas up right before the last 75-mile leg and when I went to start it, all I got was solenoid click. A couple of Mexican kids admiring my car gave me a push by hand, and it fired right up then quit, in a hail of sparks under the car, and everything was dead. The battery ground wire had melted the lead right out of the battery contact, and the bolt was welded to the ground wire. I had to have it hauled to my daughters to jack it up and find out what happened. To make a long story shorter, the tire vibration had loosened the 3/8" lock nut that holds the solenoid wire to the stud and fallen off, shorting out on the block. Not only that, but the top front damper bolt had also vibrated out, and I later found that the screws that hold my driver's side safety belt had vibrated lose and one had fallen out. I ordered new parts and fixed everything, but kind of worried about what will vibrate lose or fall off on the 1300+ miles home trip...lol! Falken all-weather highway tires are not a good choice for a little sports car. BFG next time for sure!
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NetCam
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Report this Post02-11-2014 06:53 PM Click Here to See the Profile for NetCamClick Here to visit NetCam's HomePageSend a Private Message to NetCamEdit/Delete MessageReply w/QuoteDirect Link to This Post
Bump stops were my first thought as well. I've heard some got away without it but most needed to remove the equivalent of the lowering off the stops to prevent bottoming out.

Edit: Looks like I posted as you were writing.... Sorry about your luck, if it's not one falken thing it's another

[This message has been edited by NetCam (edited 02-11-2014).]

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olejoedad
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Report this Post02-11-2014 10:06 PM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
What kind of tire pressure are you running?
You should be around 30 psi with those tire sizes.

[This message has been edited by olejoedad (edited 02-11-2014).]

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rogergarrison
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Report this Post02-12-2014 10:32 AM Click Here to See the Profile for rogergarrisonClick Here to Email rogergarrisonSend a Private Message to rogergarrisonEdit/Delete MessageReply w/QuoteDirect Link to This Post
Tires do make a difference. Falken is a cheaper brand at least around here. They are harder rubber to get you better wear, and Ive seen a lot of them out of round. When you get home, have them checked for runout. You can just jack up the rear and let them spin to see if theyre true. To check the fronts yourself, you need to mount them on the back and run them too. I bought a set of them once for a Lincoln and it rode very rough, lots of front end vibrations. They told me that my front end was shot, but took them back. I put BFGs on it and it rode smooth as silk. They did wear faster than tires I was used to because of softer compound.
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Shonyman32
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Report this Post02-12-2014 04:13 PM Click Here to See the Profile for Shonyman32Send a Private Message to Shonyman32Edit/Delete MessageReply w/QuoteDirect Link to This Post
I have falken tires with the exact same sizes. I went and asked for the cheapest tire they had and they put them on my car. The tires haven't given me any trouble with over 4000 miles on them.
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Steven Snyder
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Report this Post02-12-2014 05:01 PM Click Here to See the Profile for Steven SnyderClick Here to visit Steven Snyder's HomePageClick Here to Email Steven SnyderSend a Private Message to Steven SnyderEdit/Delete MessageReply w/QuoteDirect Link to This Post
It's not the tires --- you are riding on your bump stops. You have no suspension!
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Silicoan86
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Report this Post02-13-2014 09:54 PM Click Here to See the Profile for Silicoan86Click Here to Email Silicoan86Send a Private Message to Silicoan86Edit/Delete MessageReply w/QuoteDirect Link to This Post
It's definitely not your tires causing that, unless they are extremely out of balance. As mentioned, it's likely that you've turned your bump stops into your springs. Bump stops are not good at being springs.

While you didn't specify which model of Falken tires you're running, judging by those sizes I'm guessing that they're one of the more standard all-seasons like the ZE-912 or ZE-512 (there aren't many options for 15" wheels these days). They really aren't known for their stiff sidewalls, especially with a 60 series aspect ratio. There are many of us on here running much harsher performance tires with no issues like you described.
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