Things that go BREAK at speed-Sway bar recommendations

[jphillips-998]

Just got back from Road America in WI. Fast track. Coming out of the carousel at something close to 100. Right sway bar drop link goes bang! and I go spinning. There are concrete walls on each side. Nothing like a 100 mph spin surrounded by cement.

I managed to stay off the walls but am pretty frustrated with the sway bars from AJ USA. They sent a replacement part overnight mail (at my expense) and I had the same part fail on day two. A very reputable race shop did the install so I am confident that all was well on the install front.

Question is what bars and sizes do you track guys use? I had heard that AJ's were supposed to be higher quality than Weltmeister. My bars are 23 mm front and rear.

[katigbr]

Jphillips,
I'm not familar with the AJ bars and you didn't state whether the problem was with the front or rears. What kind of break was it? I'm running 22mm TRG bars front/back and had a droplink fail as well. In my case it was my right rear droplink. Based on conversations with a couple of racers and a mechanic whose opion I trust, the problem was related to the suspension geometry and how the droplink is set. My droplink appears to have failed when I set it to full stiff. This setting combined with my low ride height bent the droplink and contributed to the failure.

I'm contemplating a change to smart racing bars to prevent this. I'm assuming that because they mount to the springplate as opposed to the trailing arm they would prevent the problem from re-occuring at the rear.

Anyone else BTDT?

Here's what it looked like.



Regards,
Rick

[jphillips-998]

Mine was also the right rear but it was the part that attaches the drop link to the spring plate. There is a bolt that goes from the drop link to the spring plate that snapped.

The rear settings were about midway down the bar, so not overly tight.

I will check out the Smart Racing Products bars.

[911pcars]

Not sure how the AJUSA drop link attaches to the spring plate. If it's like the Weltmeister, a smallish dia. bolt goes through the upper heim joint into a modified eccentric bolt. In WM's case, it's a relatively skinny 5/16" allen head cap screw (although probably 180,000 psi). Yours is the first one I've heard that broke (which statistically doesn't mean anything). In lieu of any other changes, you could change this part out periodically with a new bolt.

The heim bearings (aka rod bearings, spherical bearings) supplied in sway bar kits can vary quite a bit in quality. Off-the-shelf bearings sell for between $3 and $75 a piece - quite a range. Even the best units have a limited misalignment angle when installed. Misalignment during operation will stress the bearing and the fastener which might have contributed to its failure. Most manufactures offer a high-misalignment angle series of bearings that might cure your particular problem. A higher strength replacement fastener could also work.

Some say the best attachment point for the rear drop link is at the factory location on the control arm. The bolt size is a fairly beefy 12mm dia. (?) which means the drop link rod bearing (whose ID accepts this bolt) must be as well. Charlie Bars (still available?) uses this mounting point; not sure about all the others.

Hope this helps,
Sherwood Lee
http://members.rennlist.org/911pcars

[Jack Olsen]

As a rule, I've been happy with the things I've gotten from AJ-USA.

But the front swaybar they sold me broke. I sent the connecting arm in to be re-welded at their expense, and -- during a competitive event -- it broke in the same place again. I threw the whole thing out, and put on a Weltmeister bar (it was all I could get at 5pm) and was on the track the next morning. No problems since then.

[jpachard]

I have the Smart Racing bars on my car (87' Carrera at 2650 lbs.) and have never had a problem. They have seen 25 track days with 9 of those at Watkins Glen. I have 23mm bars front and rear and the only problem I had was the stock mounts tearing off. I have fixed this by gusseting the hell out of them. Now I fly through the esses at 110mph plus with out a hitch.

Cheers, James

[campbellcj]

If I could afford them, I'd go with the SMART Racing bars, hands-down. Those things are works of art and seem to be built to true p-car standards.

[jphillips-998]

checked out the Smart Racing bars and yeah, they look good and yeah they are expensive.

The $1,500 spent now seems worth saving the $15,000 later when a cheaper product breaks and I am not so lucky to stay off the wall.

[jpachard]

Chris, I got mine for 1200.00 direct and they are worth every penny. The front mounts are much more robust than the weltmiester ones and I believe that the extra money spent initially will save you in the long run. I hate to see folks at the track have to lose track time for items like these failing.

Cheers, James

[89911]

Hey, I think I'm qualified to answer this post. I did have AJUSA bars on my car for 2 years. After driving the hell out of it and numerous breakage, I switched to SmartRacing bars 27mm from and rear. The AJ's aren't bad, it's there design that is a problem. The rear bolt within a bolt setup is just not strong enough for track use. I broke those at least 3 times before changing. The fronts tore through my inner fenderwall, but that was mostly do to the frailty of the inner sheetmetal. The SmartRacing bars work well, but you must reinforce all your mounting points because they will now become your weak points. After working out these bugs, they work fine. The ride quality is actually better with thicker bars then the AJ's. Better kinematics I suppose.

[jphillips-998]

Thanks all. It sounds like Smart Racing is the way to go. Wish I would have asked earlier....would have saved me a ton of time, money and frustration. Appreciate everyone's input.

[gchappel]

I'll add another example of the rear bolt on the AJUSA sway bar breaking. I broke 2 of them, but both were on slight off track excursions where the wheels either hit hard rumble strips or some holes in the dirt. I carry an extra bolt around with me- it is a 5min fix as long as you can get the broken bolt out of the eccentric nut. I never had it break without the added stress of going off track. Make sure the bolt stays tight- even when torqued to spec, the bolt tends to back out, and I think that also increases the chances of it breaking.
This board is great, I thought the bolt problem only occured on my car, my mechanic had never heard of it before. I don't track the car much anymore- I have a spec miata for that now- but may look at different bars
Thanks again
Gary

[911pcars]

For those of you who use/used an AJUSA rear sway bar; what kind of bolt broke? Was it a hex head, internal hex head (Allen)? The breakage frequency of the AJUSA sway bar hardware from this thread sounds a little higher than the Weltmeister.

thanks,
Sherwood Lee
http://members.rennlist.org/911pcars

[89911]

I have had both the Weltmeister bolt and the AJ bolt both break. They both utilize one the alignment bolts in the spring plate. The size of this bolt was very small compared to the factory one. The breakage would usually occur where the bolt exits the spring plate bolt. Because of the numerous breakage, I switched to the Weltmeister bolts because I thought it might be stronger. Wrong. The other post could be correct in that it might be some curbing that caused the breakage. Regardless, it happened almost at every DE. I never liked the adjustability of the rear bar. It actually had very little adjustment when sliding. When you tried to tighten the back end up, the droplink was tilted forward and would actually slide up the bar if not super tightened. For an improvement over the stock bars, perhaps, but not for extended track use.

[911pcars]

I think a general rule for the drop links would be to have them as long as practical without bottoming out. The more effective sway bars provide this in their design. The short links on the WM and AJUSA rear bars, as 89911 points out, create inefficient angles beyond a narrow adjustment range - probably sufficient for the street, perhaps less so on a track car.

The WM upper link attachment bolt is a 5/16" SAE internal hex head bolt (not sure of the configuration of the AJUSA bolt). This internal hex bolt should have a tensile strength of 180,000 psi, pretty good for a bolt that size. It's probably a good idea to start off with one made by a reputable manufacturer (non-hardware store brand) and replace it periodically.

Not to get too overly dramatic but Jim Clark, the great F1 driver and World Champion as well as Indy 500 winner, died at Hockenheim when his rear sway bar broke at speed.

Sherwood Lee
http://members.rennlist.org/911pcars

[Howard Nelson]

Hi Jeff!

I didn't realize you were in the carousel when it broke - I'm glad you and the car are ok. FWIW, I have the 22mm Weltmeister F&R and haven't had any problems (so far...) Then again, I'm not going as fast as you By the way, on Sunday I matched my best time - with the street tires on front! Take care...

[jluetjen]

The other post could be correct in that it might be some curbing that caused the breakage.

If you ask me, "Curbing" didn't cause the breakage - a poorly designed or executed swaybar linkage does. Normal wear and tear on a race track includes riding curbs in my book, especially in a "sedan" like a 911. (OK - I'll grant you that it may not be as acceptable of a technique in a Formula or Sportsracer).

Just to echo what I think everyone is saying - I think that it is time to try another mounting strategy (or vendor in this case). Failure to do so will only result in further breakages.

BTW -998, could you post a picture of the linkage as installed on the car. I'm not picturing it.

[Bernie914]

I too have had a sway bar drop link fail...
(Addco on a non Porsche) No loss of control resulted.
I replaced the drop links with grade 8 bolts of larger
diameter to correct the problem.

[jphillips-998]

I am picking up the car tomorrow, complete with the new Smart Racing Products bars. I can tell you that just by looking at the hardware they will be much more reliable, albeit at twice the price.

Should be well worth the addtional expense, just wish I would have gone that way to begin with.

I will post a pic of the new and the old system once it is all back together.

[jphillips-998]

Howard,
Yeah it was in the carousel and the video is pretty wild! Congrats on your best time, is that why I saw YOUR wheels still on the other guys car when I drove out? Just happen to forget to switch back?