bad shock(s)? Sources?
09-25-2015, 02:14 PM
#1
3rd Gear
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bad shock(s)? Sources?
Car is April '94 prod 993 base Coupe, 125k miles
A decade ago I replaced stock springs/shocks with a Carnewal-sourced ROW MO30 kit. Marvelous conversion. Since then the car has seen about 25k+ miles and maybe a dozen track days, the last one in 2007.
Over this past summer, its handling seems less precise, and especially sudden directional changes seem to unsettle the car. Nothing is loose underneath and trying to bounce the corners (old fashioned way of "testing the shocks") produces nothing unusual, but pushing sideways on the roof produces some jiggling that I don't think is right. Since the car isn't tracked anymore, the obvious tire hop under braking and crazy cornering aren't noticible, but I strongly suspect bad rear shocks. On the otherhand, this seems like a rather short life, considering the original items lasted 90+k miles and lot of track days.
Thoughts? And what is the appropriate and cost-effective source and replacement for the ROWM030 shocks?
Thanks.
Phil
A decade ago I replaced stock springs/shocks with a Carnewal-sourced ROW MO30 kit. Marvelous conversion. Since then the car has seen about 25k+ miles and maybe a dozen track days, the last one in 2007.
Over this past summer, its handling seems less precise, and especially sudden directional changes seem to unsettle the car. Nothing is loose underneath and trying to bounce the corners (old fashioned way of "testing the shocks") produces nothing unusual, but pushing sideways on the roof produces some jiggling that I don't think is right. Since the car isn't tracked anymore, the obvious tire hop under braking and crazy cornering aren't noticible, but I strongly suspect bad rear shocks. On the otherhand, this seems like a rather short life, considering the original items lasted 90+k miles and lot of track days.
Thoughts? And what is the appropriate and cost-effective source and replacement for the ROWM030 shocks?
Thanks.
Phil
09-25-2015, 03:37 PM
#2
Rennlist Member
Dampers damp, so I don't see that being the problem from your description. You don't mention the age of the tire, or if that's not the case, then maybe a different tire. And things can come loose. Until you're under there you don't know.
Other elephant in the room is something changing in the alignment. Out-of-spec rear toe causes all sorts of odd behavior. (My cousin's 993 Turbo came to him properly aligned and drove horribly. We finally found two bent rear arms.)
Not sure where tire hop would come into play on track, from describing past behavior. There's no need to be into the ABS. And that's not tire hop anyway.
IF you had a bad rear damper, first you'd be looking to one cornering direction with dissimilar behavior to the other.
Other elephant in the room is something changing in the alignment. Out-of-spec rear toe causes all sorts of odd behavior. (My cousin's 993 Turbo came to him properly aligned and drove horribly. We finally found two bent rear arms.)
Not sure where tire hop would come into play on track, from describing past behavior. There's no need to be into the ABS. And that's not tire hop anyway.
IF you had a bad rear damper, first you'd be looking to one cornering direction with dissimilar behavior to the other.
09-25-2015, 03:45 PM
#3
RL Technical Advisor
Hi,
IMHO, you need a qualified professional to help you diagnose a bad shock (or two) as that takes a fair bit of experience. The OEM Monroes are certainly not known for durability/longevity so this isn't surprising, at least on my part. You may have a tire issue, however a competent technician will be able to tell you that.
Without knowing where you live, I'm unable to offer any recommendations or referrals, but should your M030 dampers be defective, I'd recommend the Bilstein HD's for your car as an excellent replacement. US-sourced ones carry a limited lifetime warranty, something not available outside this country.
IMHO, you need a qualified professional to help you diagnose a bad shock (or two) as that takes a fair bit of experience. The OEM Monroes are certainly not known for durability/longevity so this isn't surprising, at least on my part. You may have a tire issue, however a competent technician will be able to tell you that.
Without knowing where you live, I'm unable to offer any recommendations or referrals, but should your M030 dampers be defective, I'd recommend the Bilstein HD's for your car as an excellent replacement. US-sourced ones carry a limited lifetime warranty, something not available outside this country.
09-25-2015, 06:19 PM
#4
3rd Gear
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Thanks for the tips and advice.
Tires are 5-6 years old Michelins at recommended inflations.
I've owned the car for 20+ years and its history is well-known to me. Suspension wear items and wheel bearings were replaced at about 75k by Steinel (Ohio) so I have doubts this is bad bushings etc...
I do my own work on the car, and have recently been under it for inspection, and am its only driver. Between all this, I'm confident there's not been anything knocked out of alignment and there is nothing loose or abnormal appearing.
"tire hop".....On the last legs of the last set of shocks my left front would hop under hard threshold braking (I'm a former PCA instructor for LSR and had some success in the motorsport competition world, so I think my footwork is decent), a problem that responded to the diagnosis suggested by a fellow instructor, by replacing the shocks. Not too hard for me to imagine that certain loadings set up resonances that bad dampers will not dampen.
I plan to look the car over again with a more critical eye this weekend. Another thought....engine mounts (still factory originals)? I've heard no clonking with sudden turns, and have so far ascribed the increasingly temperamental clutch uptake to 21 years and 125k miles....
Tires are 5-6 years old Michelins at recommended inflations.
I've owned the car for 20+ years and its history is well-known to me. Suspension wear items and wheel bearings were replaced at about 75k by Steinel (Ohio) so I have doubts this is bad bushings etc...
I do my own work on the car, and have recently been under it for inspection, and am its only driver. Between all this, I'm confident there's not been anything knocked out of alignment and there is nothing loose or abnormal appearing.
"tire hop".....On the last legs of the last set of shocks my left front would hop under hard threshold braking (I'm a former PCA instructor for LSR and had some success in the motorsport competition world, so I think my footwork is decent), a problem that responded to the diagnosis suggested by a fellow instructor, by replacing the shocks. Not too hard for me to imagine that certain loadings set up resonances that bad dampers will not dampen.
I plan to look the car over again with a more critical eye this weekend. Another thought....engine mounts (still factory originals)? I've heard no clonking with sudden turns, and have so far ascribed the increasingly temperamental clutch uptake to 21 years and 125k miles....
09-26-2015, 02:35 AM
#5
Drifting
Not sure if any link to your original question, but given your car's mileage and age, you will thank yourself for some new mounts. One of the easiest DIYs you can do: 6 bolts+2 nuts, jack under tail of engine, 2 beers (if you are doing it with a friend and chatting). OEM/RS/Wevo/etc whatever will tighten things up a bit. I went RS and shifting was a bit improved. My old mounts pissed out hydraulic fluid in the process of removal....yeah, they were done. I did this at somewhere around 90k mi.