Bent RR trailing arm

fly4val · 11-25-2006, 06:17 PM

Had a major alignment done to get the steering rack spaced out and installed new turbo tie rod assemblies.

Good alignment guy says the RR trailing arm is bent; however, he was able to bring it back within spec, kind of....should I replace it with new or try a used one or?

'88 3.2 coupe, totally stock except lowered

thanks,
Val

randywebb · 11-25-2006, 07:14 PM

An '88 would have an Al. arm - he is saying the Al arm was bent and he straightened it??

fly4val · 11-26-2006, 02:25 PM

Hi Randy,

Clarify.....no, he didnt straighten it, he just fiddled with the
shims/adjustments as best he could.

Q still stands, new or used? Noted 'LA Porsche dismantler' in
the valley (Sun?) has used ones avail for $200-
what do you think?

Thanks,
Val

randywebb · 11-26-2006, 03:38 PM

I'd get used.

HarryD · 11-26-2006, 04:03 PM

When I had my car done last year at Rothsport, I was told the same thing. I asked if I should be concerned and they told me that unless I needed more negative camber, there was no need to rush.

Does your car track ok, no odd tire wear, and feel "right"? If you are in spec, you are in spec. If so, sounds like something you may need to address down the road but I wouldn't hurry.

Grady Clay · 11-26-2006, 04:08 PM

When I was in the business I had all the factory P-tool test jigs for the suspension arms (still do). I let anyone bring in their arms to be tested. When some wanted to go back and forth bending and re-testing I refused. These were the steel (’65-’73) arms. Sorta like trying to use a straightened pop can. The aluminum arms, like yours, are even more sensitive. I don’t recommend straightening.

My recommendation is to use a known (tested) new or used arm. While seldom done, I would Zyglo any used (and possibly new) arm.

You should also measure the wheel bearing bore for out-of-round and size.

Best,
Grady

fly4val · 11-26-2006, 04:14 PM

Gents, Randy and Harry, many thanks for your input.

The car tracks ok, took it in due to a wee bit of tail wagging
and not happy with the front alignment (hunts) post
the front end work.

I'll pick up a used one out of LA, probably when I'm
in SoCal to winter over for Xmas...22-28 Dec.

PS is there a kit that has all the consumables, brgs
,seals, etc when changing one for a used one...?

Thanks again..hope ya had a good gobble gobble

Zeke · 11-26-2006, 04:31 PM

Not really a "kit" that I know of available. Ask here for a used arm on the parts4sale forum before spending 2 bills. Sometimes a pair goes for that. An orphan might be cheaper yet.

Now, your comments about "car tracks ok, took it in due to a wee bit of tail wagging and not happy with the front alignment (hunts) post the front end work" is of more concern. This could be due to tires (did you do the alignment following the installation of new tires? [recommended] ), or shocks, or even other factors like worn bushings.

Also, was the alignment done by someone that knows 911's well? We need more info on this to discuss.

fly4val · 11-26-2006, 04:47 PM

Hi Milt....

Tire age indeterminate, inner/outer sidewalls good no checking, tread wear so so....thinking about 10-15k as car was not driven
that much over its life, I had local Discount Tires pop all tires off the rims and swap left to right in case of camber wear. Have most of the records since 55k...had 98k when I bought it in feb. Same story on the shocks....first alignment was done by Les Schwab's whom I do not care for...second alignment a done at Barrier Porsche on Friday. Spoke at length with the tech; he had raced SCCA, same as me some years ago; however, I was running a '63 s/w Corvette in B Prod. He also showed me thwe left rear sway bar bracket was broken said it was a fairly common item..your thoughts?

Actually handled a bit better prior to the front end work, shop tech tried to align it himself and took it back for above noted defects then it went to Schwabs, no one else local within decent driving, Im at Boeing with 60 hour weeks so its hard to deal with someone open only during the week.

BTW had 7.5 happy years at LGB with Douglas, sure sad to see them gone....

HarryD · 11-26-2006, 05:52 PM

Quote:

Originally posted by fly4val
Hi Milt....

Tire age indeterminate, inner/outer sidewalls good no checking, tread wear so so....thinking about 10-15k as car was not driven
that much over its life, I had local Discount Tires pop all tires off the rims and swap left to right in case of camber wear. Have most of the records since 55k...had 98k when I bought it in feb. Same story on the shocks....first alignment was done by Les Schwab's whom I do not care for...second alignment a done at Barrier Porsche on Friday. Spoke at length with the tech; he had raced SCCA, same as me some years ago; however, I was running a '63 s/w Corvette in B Prod. He also showed me thwe left rear sway bar bracket was broken said it was a fairly common item..your thoughts?

Actually handled a bit better prior to the front end work, shop tech tried to align it himself and took it back for above noted defects then it went to Schwabs, no one else local within decent driving, Im at Boeing with 60 hour weeks so its hard to deal with someone open only during the week.

BTW had 7.5 happy years at LGB with Douglas, sure sad to see them gone....

The sway bar mounts are a common failure point. WEVO makes an improved version. You might want to check it ut. How are your welding skills?

Before you start chasing your suspension issues by buying a new arm I think you should stop and summarize the problem you attempted to fix and where you are today. While replacing the arm may fix the problem either directly or in a collateral way, you may be $$ and time ahead by speding a bit more time gathering diagnostic data before you proceed.

I think I am hearing "tag wagging" (perhaps due to broken sway bar not helping to reduce oversteer effects) and front end wander (maybe not enough toe). From your last alignment report, what were the "as left" conditions. How do they compare to the specs for your car? How does your ride height look? I presume you do not have corner balance data but that may play into the equation as well.

FWIW, an interesting web site.

T77911S · 11-28-2006, 05:05 AM

the rear sway bar adds oversteer, lack of bar would reduce oversteer.

fly4val · 12-02-2006, 04:11 PM

Hi Milt...thanks for all your post...couldnt find WEVO on a web search is there more of a name for them? Reviewed the ref'd article, pretty much refreshed my memories from days in SCCA, thanks.

Welding skills suck....had aerospace welding classes years ago but no equipment or place to do it these days. Have excellent working relationship with a local large body shop, does lots of dealer work and very exacting. Probably will go to them when I'm ready.

Alignment Tech at the Porsche dealer gave me a steer for the bracket installation from a local body shop they use and the tab is/was $325- seems bit high?

I'm an EME engineer at Boeing in Everett north of Seattle. Have a good network here but need to find someone in production or quick fix shop that could do it on the side for me? Have 'the' man as a friend but he's in Tahoe so not practical.

Thanks to you and T77911S about the effects of a non fully functioning rear sway bar, frankly hadnt thought of that at all...