A-arm bushings, Pros - cons?? Options

[East coaster]

What's the best setup for a street car?

Tarret bronze/urethane? (Sounds like a good idea, but never heard from anyone running them)

Needle Bearings? ( I worry about rust and maintenance issues)

Stock with 40K on them? (Has a low "trick" factor, but probably works good)

Delrin/urethane (squeeky........don't want them)

Ditto for rear trailing arm bushings????

[anthony]

I think the Elephant poly bronze is a good solution but if your stock bushings only have 40K on them and haven't sagged then I'd just stay with those. There are tons of threads BTW on the 911 bird board about poly bronze bushings.

[914-8]

I think most people with street drivers would love to have A-arms with low mileage, excellent condition stock rubber bushings on them.

I know I would! I'd take those over any of the others you mentioned, hands down, for my street car.

[brant]

if you have good stock bushings...
then I'd agree.
I had a lowish mile green car for a while with NOT SHOT stock bushings.
that was a sweet ride for the street!
compliant and comfortable.

plus you'll never be able to go back to that!


oh by the way.
the poly aren't so bad if you install and zerk them.
they are certainly cheap.

although I agree that spending the $ for something like mueller bearings or Racer chris bushings are certainly better...

I have a poly car and a mueller bearing car currently.
brant

[srb7f]

What's wrong with keeping the stockers? Double check that they aren't sagging by taking a peek at the end of the torsion bar closest to the passenger compartment. If they are sagging, there will be a little groove worn into them just in front of the spline.

I wish I still had my stockers sometimes whenever the squeaks remind me that I put the urethane ones in...

Steve

[ChrisFoley]

QUOTE (East coaster @ Mar 19 2006, 10:48 PM)

Delrin/urethane (squeeky........don't want them)

Well made/installed Delrin bushings aren't squeeky.
Weltmeister Poly bushings are. No matter how much time you spend on the installation they won't be quite right.
People with needle bearings swear by them, even for street use.

[alpha434]

QUOTE (Racer Chris @ Mar 19 2006, 08:45 PM)

QUOTE (East coaster @ Mar 19 2006, 10:48 PM) Delrin/urethane (squeeky........don't want them) Well made/installed Delrin bushings aren't squeeky. Weltmeister Poly bushings are. No matter how much time you spend on the installation they won't be quite right. People with needle bearings swear by them, even for street use.

Do the needle bearings bottom out after extended use?

[alpha434]

Bump.


I meant, do the bearings wear on one side more than the others, since the bearing rarely makes a full turn and so a portion of the bearing is under load ALL the time while other parts or never under load.

[MattR]

QUOTE (alpha434 @ Mar 19 2006, 09:08 PM)

Bump. I meant, do the bearings wear on one side more than the others, since the bearing rarely makes a full turn and so a portion of the bearing is under load ALL the time while other parts or never under load.

The idea behind a bearing is it distributes the load reguardless of position.

[Mueller]

QUOTE (alpha434 @ Mar 19 2006, 10:08 PM)

Bump. I meant, do the bearings wear on one side more than the others, since the bearing rarely makes a full turn and so a portion of the bearing is under load ALL the time while other parts or never under load.

I don't have the specs in front of me, but the bearings are rated for something like 15,000 pounds static (way more dynamic)...now times that by 4 and you have plenty of support......we've pulled apart bearing after street and track use after 2 years, no signs of problems or rust.....

I'd opt for the Delrin bushings from Chris Foley and then the Elephant bushings.....I no longer make the needle bearing kits but as far as I know they are availabe from Shine racing....

[ChrisFoley]

QUOTE (alpha434 @ Mar 20 2006, 12:08 AM)

I meant, do the bearings wear on one side more than the others, since the bearing rarely makes a full turn and so a portion of the bearing is under load ALL the time while other parts or never under load.

That is one of my concerns regarding needle bearings used as suspension bushings. The needles will always be loaded on the same surface and will eventually become flat spotted.
My other concern is that the factory components the needle bearing outer sleeves press into aren't round, therefore the needle bearings have to be loose or they will bind.

[alpha434]

That idea only applies to load during rotation.

When the load on a bearing is pulling it one direction, and the bearing doesn't make a rotation, the load remains on one place until it wears.

With a wheel bearing, the wheel is turning, and no one bearing is exposed to the load for any readily calcuable amount of time.

The bearing at "TDC" is taking no load in the example of the wheel bearing. The bearing at BDC is taking 100% of the load. But the two change positions very quickly to compensate.

[914-8]

Chris, can you give some info on your delrin bushings?

[alpha434]

QUOTE (Mueller @ Mar 19 2006, 09:33 PM)

QUOTE (alpha434 @ Mar 19 2006, 10:08 PM) Bump. I meant, do the bearings wear on one side more than the others, since the bearing rarely makes a full turn and so a portion of the bearing is under load ALL the time while other parts or never under load. I don't have the specs in front of me, but the bearings are rated for something like 15,000 pounds static (way more dynamic)...now times that by 4 and you have plenty of support......we've pulled apart bearing after street and track use after 2 years, no signs of problems or rust..... I'd opt for the Delrin bushings from Chris Foley and then the Elephant bushings.....I no longer make the needle bearing kits but as far as I know they are availabe from Shine racing....

A raw strength rating doesn't protect it from abrasive machining. Wear. I never thought that they would bend or break under load. A LOT of the wear variable would depend on the lubrication system. But I suppose that a good a-arm regreasing could be a smart part of regular maintenence. Especially if the performance is better.

[ChrisFoley]

QUOTE (914-8 @ Mar 20 2006, 12:38 AM)

Chris, can you give some info on your delrin bushings?

Have a look at my Suspension Webpage first so you can ask me specific questions.

[Mueller]

the bearing races are hardened to 60R, "if" and when there is wear, it'll be many, many moons down the road...the bearing itself cost $6 each (4X) so what if you have to replace a few 10 years from now??? (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

none of the rubber bushing replacments are perfect, there will always be some sort of comprimise with each solution

[alpha434]

QUOTE (Mueller @ Mar 19 2006, 09:42 PM)

the bearing races are hardened to 60R, "if" and when there is wear, it'll be many, many moons down the road...the bearing itself cost $6 each (4X) so what if you have to replace a few 10 years from now??? (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif) none of the rubber bushing replacments are perfect, there will always be some sort of comprimise with each solution

Fair enough, Mueller. I always liked the idea of needle bearings there anyway. I just wanted some input and maybe open discussion on it. Thanks.

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[ChrisFoley]

QUOTE (Mueller @ Mar 20 2006, 12:42 AM)

none of the rubber bushing replacments are perfect, there will always be some sort of comprimise with each solution

The primary compromise with my bushings is that the tooling required for fitment is too expensive for everyone to purchase their own, so it isn't a DIY same-day method. You have to ship the trailing arms or the front brackets to me for proper installation of the bushings. The big advantage is the ID of the bushings will be sized accurately and will be truly round.

[914-8]

QUOTE (Racer Chris @ Mar 19 2006, 09:42 PM)

QUOTE (914-8 @ Mar 20 2006, 12:38 AM) Chris, can you give some info on your delrin bushings? Have a look at my Suspension Webpage first so you can ask me specific questions.

I've had a lot of porsches over the past 25 years and done a lot of work on them, but replacing the suspension bushings is one of the things I've never done.

So forgive me if the answers to this are obvious or I'm off base.

But your website says"

"Exchange your old carrier brackets for powdercoated ones with Delrin bushings.

The bushings are pressed in, then reamed to a precise tolerance."

Would I have to send the A-arms to you? Because my understanding was that the a-arms themselves are the things that have loose tolerances. So without my actual a-arms, how can you ream the IDs of the bushings to a "precise tolerance?" What tolerance do you ream them to?

[alpha434]

QUOTE (914-8 @ Mar 19 2006, 10:02 PM)

QUOTE (Racer Chris @ Mar 19 2006, 09:42 PM) QUOTE (914-8 @ Mar 20 2006, 12:38 AM) Chris, can you give some info on your delrin bushings? Have a look at my Suspension Webpage first so you can ask me specific questions. I've had a lot of porsches over the past 25 years and done a lot of work on them, but replacing the suspension bushings is one of the things I've never done. So forgive me if the answers to this are obvious or I'm off base. But your website says" "Exchange your old carrier brackets for powdercoated ones with Delrin bushings. The bushings are pressed in, then reamed to a precise tolerance." Would I have to send the A-arms to you? Because my understanding was that the a-arms themselves are the things that have loose tolerances. So without my actual a-arms, how can you ream the IDs of the bushings to a "precise tolerance?" What tolerance do you ream them to?

The delrin has to be pressed in first, so that the material won't flex during cutting, then he will measure your a-arms and cut EXACTLY the right size +- .001 or so to the specific A-arm part. THAT is why he has to have your a-arms on hand. They are low tolerance and the bushings won't work properly at that low of a tolerance. He matches the sizes and everything is better.

But I'm a big fan of burnishing the delrin instead of reaming. More expensive tooling initially, but there isn't any raised surface after the reaming, and the finish can come out VERY smoot. Up to a 4 micron finish on mechanical grade delrin.