My balls are loose!!

powella · 06-07-2009, 01:16 PM

Hi Guys,

About 3 months ago I put some Rennline Monoballs on my 88 3.2. I've noticed that they make a real knocking noise when I go over any kind of bump. Is this normal?

any help much appreciated

cheers
Alex

DanielDudley · 06-07-2009, 01:18 PM

Did you call the manufacturer ?

Talewinds · Talewinds's Garage

If I'm out jogging mine knock together a lot, so, maybe its normal...
(Hey you started it, sorry I no experience w/ the Rennline Monoballs, but I've considered putting them on my 88')

Aurel · Aurel's Garage

Put a bra on the front end

.

kokenm · kokenm's Garage

There once was a man named glass who had two balls made of brass.
When he rubbed them together they played stormy weather.
And sparks shot from his A**.

Sorry man I don't know about those balls but you threw it out there like shave and a hair cut and I could not resist.
Mike

MattAlpha · MattAlpha's Garage

Powella,

I remember reading a post about a year ago or so with the same problem. He contacted the manufacturer and they send him replacement monoballs because the ones he received were bad out of the box (I think he had to send them back first though). Maybe your problem...

If you do a quick search you'll probably find the thread.

kucharskimb · 06-07-2009, 06:05 PM

Spherical bearings or monoballs are intended to be used in radial load applications, ie perpendicular to the thru-bolt. Think of the rod ends on a upper strut brace pulling in tension or the rear lower control arm bushings working back and forth and up and down.

When spherical bearings are used in an axial load setting, the suggested maximum axial loading is 10-15% of the maximum radial load. For COM 14/16 bearings, this is roughly 4000-5000 lbs force maximum allowable axial load. That may seem like a lot, but is it for a car?...

http://aurora.thomasnet.com/viewitem...1088&forward=1

http://www.aurorabearing.com/technic...s/default.html

"Harshness" is a misnomer. By harshness, you might be referring to rattling caused by worn bearings and the subsequent slop between the metal to metal parts. When all parts are new and tolerances are tight, the only harshness that will be transmitted will be caused by the stiffness of your shocks/springs/sways. Additional noise will be present due to the vibrational transfer properties of metal compared to rubber.

So, what happens when you exceed the axial allowable forces? Catastrophic failure? No. You slowly start to work (beat) the races away from the center bearing. What is the force transmitted by a 2600lb car that has been lowered when the front struts bottom out. The quick answer is infinity. Considering most people that drive on the street complain of developing a rattle/knock in their front upper strut monoballs, it begs to question.

Replacing the cartridge/bearing will only be a bandaid.

I had the same problem with mine, and a friend went through 3 sets on his street/track car before he finally gave up. It's a poor application for street cars. I would imagine track only cars have a bit better luck.

I'd love it if someone ran an equation with a force component through the strut of hitting a rut at 60mph with delta t being .1 seconds. Let's say 20% of the 2600lb car just smashing into a wall would be the force on the monoball. I come up with 1450lbs. Well under the 4-5000 lbs allowable, but is my equation realistic and correct?

Sorry, I geeked out there a bit...

Gordo2 · Gordo2's Garage

Alex,

I just got my car back together recently after a major suspension upgrade that included shock tower monoballs. I took my first drive this afternoon with the sway bars hooked up and noticed the same (major banging when I go over a harsh bump).

Will let you know how things are when I get it back from alignment and corner balance later this week.

Good luck,

Gordo

powella · 06-08-2009, 04:32 AM

Thanks for all your responses guys - May end up sticking rubber back in there again as the roads in uk are rubbish... I'll also ping rennline a mail too just to check what should be acceptable!! will post back with results...

cheers
Alex

calling911 · 06-08-2009, 06:13 AM

Guys.. I just want to get up on my little chair for a second and give a speech to you all. Porsches are designed from the factory to perform as best as possible on the street without compromising ride quality or environment.

Just leave the thing along. Save your money for when something needs to be repaired or maybe buy one of those go fast wings for the back.. lol.. or maybe whited out tail lights.. they are good for 20 hp.

Seriously.. I've learned these lessons over and over.. stock parts are the way to go unless you are willing to compromise ride quality for very minor performance increases... I dont want to sound arrogant, but with my racing background I'll take an stock car against your same year suspension modified, bolt on engine this and that and proceed to whoop your a$$. Better yet, spend your money on a drivers school...

Off my little chair.

Mattcamp · 06-08-2009, 06:30 AM

Nice rant.....really I liked it.

My friend has these and he has the same freaking problem but I think it's only on 1 side. I believe they sent him a new ball but it has the same problem.

Aurel · Aurel's Garage

Snow tires in the winter, bra in the summer. That`s all a 911 needs. And a cool collar

.

powella · 06-09-2009, 01:33 AM

I agree Porsches are designed from the factory to be as good as they can be, BUT, for that point in time only. dont forget we are 20 years down the road and an awfull lot has changed - some good, some bad, some not relevant. I understand your opinion and i'm always aware of it, but i want to make my little car perform as well as it can without sacrifice. Monoballs should give me that - and actually they do - my car handles superbly now - much much better than it did. I've spoken to Rennline and either I have not got the balls tight enough in the perch or i have knackered bearings!! Which they will happily replace...

calling911 · 06-09-2009, 02:07 AM

Quote:

Originally Posted by powella

I agree Porsches are designed from the factory to be as good as they can be, BUT, for that point in time only. dont forget we are 20 years down the road and an awfull lot has changed - some good, some bad, some not relevant. I understand your opinion and i'm always aware of it, but i want to make my little car perform as well as it can without sacrifice. Monoballs should give me that - and actually they do - my car handles superbly now - much much better than it did. I've spoken to Rennline and either I have not got the balls tight enough in the perch or i have knackered bearings!! Which they will happily replace...

Really.. what is th advantage on the street driving at legal speeds? Curious.

powella · 06-09-2009, 11:55 AM

The car would really snatch on the wheel moving from camber to camber with any kind of ripple in the road - that has completely gone since i fitted elephant polybronze control arm bushes and monoballs. The roads around here are very twisty country types where 60 ish is sometimes too much!!

Superman · 06-09-2009, 01:33 PM

Monoballs are for race cars.

Other improvements, even to a street car, can make sense.

Somebody out there is prepared to whoop your @$$ JP, using a bone stock Dodge Colt. If your racing experience is at a par with your blusteriness, then you and I will both know it's not about the monoballs. It's the nut behind the wheel.

Zeke · 06-09-2009, 02:41 PM

I had a problem with the Boxster that no one could find. Several looked at it over the course of a year. Turned out it was a trailing arm monoball. Now, when the car is on a lift, the suspension is in droop and the ball is bound. I suspected this link, but couldn't find a 4 post ramp lift to use in order to check it out with the suspension in normal position.

Anyway, we found it and replaced the part. No more noise. When I examined the part, you could hardly tell it was worn, but the sound on the bulkhead and in the car was extreme. It really sounded like 2 pieces of the body had detached.