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Old 04-18-2006, 10:25 AM   #1
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Shake in front end..

I have a minor shake in the front end at some higher speeds (70+)
I have 4 brand new tires, all balanced, checked wheels and they are true.
Thoughts?

My old 951 always did this no matter what I did, same issue? live with it?

Thanks
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Old 04-18-2006, 10:34 AM   #2
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Hi,

Were your new Tires Dynamically Balanced? There can be some great discrepancies between new tires and only by using a Hunter Dynamic Balancer (97XX Series is most current I believe) can you be sure that the Tires are within spec (they all are not or cannot be properly matched with their Mate).

If this was done, start thinking about alignment or possibly a bent suspension member (these are Alloy and can be bent from a PotHole, Speed Bump or hitting a curb, albeit lightly, sufficient that they introduce a shimmy such as you describe). Hope this helps...

Happy Motoring!... Jim'99
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Old 04-18-2006, 12:13 PM   #3
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Front end shake, vibration, shimmy, whatever you want to call it is typically a tire issue. At times it can only be seen if the balancing is done on the car, a method not often used by your typical tire shop. If your tires have been (most likely) balanced and re-balanced off the car, you might poke around and see if you can find someone that can do it on the car.
A couple of other possible contributory tire conditions are out-of-round (relatively rare), and problems with uniformity, a manufacturing defect related to internal stresses caused during the tire building process.
Out-of-round used to be addressed by grinding the surface (usually the shoulders) of the tread, but I don't even know if they do it anymore.
Uniformity problems are uncorrectable, other than by replacement of the tire.
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Old 04-18-2006, 12:29 PM   #4
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find a "road force" balance machine such as a Hunter 9700 as Jim suggested. Check this website for a zip code search. My closest Discount Tire just installed one a month ago, which is nice to have close by... and cheap too. $19.99 a tire. The high performance shops were nearly double that when I called.

http://www.gsp9700.com/pub/search/findgsp9700.cfm

Other readers of this post should search too to find one nearby and make a mental note of it! Boxsters seem to be very hard to get into wheel balance and keep there. This machine really got my boxster smooth and vibration free after many, many balancing sessions at 4 different places!
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Old 04-18-2006, 05:50 PM   #5
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Yes, these cars as well as the 996's are a PITA when it comes to the mid 70's speeds. I just swapped out a used set of modular rims with BBS RS-GT's and brand new N1 Pilots and it's glass smooth up to 74 then it vibrates to about 90 then it smooths out to where it's glass again at 100 and above (don't tell anyone....). They were balanced on a hunter 9700 but it looks like I'll be getting it done again on a different machine, probably the one at the dealer. The have the 9700 and don't charge an arm and a leg for tire work.
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Old 04-18-2006, 07:48 PM   #6
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Check your tire pressure. The shops never fill it properly when balancing. If the balancing really is good, then try an alignment. If the alignment doesn't take care of it then it's most likely a worn control arm bushing, worn ball joint, worn tie rod end, bent suspension part, worn wheel bearing, bad shock and/or spring or worn steering rack mount bushings.

That should narrow it down a little. Be patient, these things can really be a PITA to find if it's a worn part.
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Old 04-19-2006, 10:02 AM   #7
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Marc, I've got the same problem. My boxsters pretty smooth until I hit 80 or so....then it's vibration city. Really sucks. Love the car, but after spending over 20 grand on the purchase, I'm a little disapointed to say the least. Takes all the fun out of it. I've taken it to the local Porsche garage a couple times and they check this and that, but it's still the same. I've got 18 inchers on it and don't know if that could be a problem as the 98 came with 16s. Had a Saab 95 before this and it was as smooth as silk. I don't think I'll find the "high tech" equipment you guys got in the US here in Spain, so I'll just have to keep trying....till they fix it or I get fed up and sell her. And 80 mph isn't that fast here, the speed limits about 72 mph (120 kph).
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Old 04-19-2006, 10:06 AM   #8
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Bigdog, it could be your tires, even if they're new. The first set I put on my cars were out of round and no amount of balancing, regular spin or road force or on-car balancing was going to correct it. And my problem occurred at 80 or so...

Try two new tires on the front first and see if that fixes it.
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Old 04-19-2006, 10:23 AM   #9
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I just changed the back tires and they cost me a arm and a leg...you wouldn't believe me if I told you. The fronts LOOK brand new. After the fortune I've spent (Sport suspension, new top, complete tune-up, new radio-cd, speakers, clear rear lights, a set of 2nd hand 16 inchers for the road inspection, new rear tires...) kinda blows to think I have to spend more...and if it doesn't work? If it wasn't such a beautiful car!
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Old 04-19-2006, 10:31 AM   #10
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Quote:
Originally Posted by bigdog
Marc, I've got the same problem. My boxsters pretty smooth until I hit 80 or so....then it's vibration city. Really sucks. Love the car, but after spending over 20 grand on the purchase, I'm a little disapointed to say the least. Takes all the fun out of it. I've taken it to the local Porsche garage a couple times and they check this and that, but it's still the same. I've got 18 inchers on it and don't know if that could be a problem as the 98 came with 16s. Had a Saab 95 before this and it was as smooth as silk. I don't think I'll find the "high tech" equipment you guys got in the US here in Spain, so I'll just have to keep trying....till they fix it or I get fed up and sell her. And 80 mph isn't that fast here, the speed limits about 72 mph (120 kph).
Hi,

18" Wheels on the '97s and early '98s are a big No-No! And, likely to be contributing to your problem if your production date is early.

Porsche structurally reinforced the Chassis on later '98 models to accept 18" Wheels. Without this reinforcement, the Handling can be so adversely affected as to be dangerous at higher speeds. Hope this helps...

Happy Motoring!... Jim'99 (w/ OEM 18" Wheels)
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Old 04-19-2006, 01:14 PM   #11
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Jim, have you read the most recent comments from the PCA web site's tech area on this subject?

PCA Article on 18 inch rims on 97 boxsters...

Joel Reiser ended his explanation with this:

"All that being said, I would not be too worried about running 18" wheels on a street-driven 1997 Boxster as long as the widths and offsets are in range with what the factory offered later, and you are not driving the car to the limits."
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Last edited by RandallNeighbour; 04-19-2006 at 01:19 PM.
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Old 04-19-2006, 02:56 PM   #12
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Quote:
Originally Posted by RandallNeighbour
Jim, have you read the most recent comments from the PCA web site's tech area on this subject?

PCA Article on 18 inch rims on 97 boxsters...

Joel Reiser ended his explanation with this:

"All that being said, I would not be too worried about running 18" wheels on a street-driven 1997 Boxster as long as the widths and offsets are in range with what the factory offered later, and you are not driving the car to the limits."
Hi,

I did read it and to me it's not that definitive, in fact if anything, the Author lends a somewhat cautious note and is not so emphatic about his opinion until he checks with others (other civilians, not Porsche).

He cautions about driving at the limit without ever stating what that limit is - What does that mean? The point to where the 18" Wheel rips the suspension from the unreinforced chassis? It's like the fellow Bus passenger who asks you for directions and you tell him to get off two stops before you do...

We can't get Porsche to even get the RMS straight, but if they're adding structural reinforcement for the sake of merely increasing the Options List, there must be a reason.

My '99 is already taken care of, but I'd be cautious about oversizing the Wheels on an earlier model...

Happy Motoring!... Jim'99
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