rraustin

Anyone running solid thrust arm bushing and spherical bearing monoballs at the same time on the street? If yes, how is the the NVH (noise, vibration, harshness) compared to OE?

I am putting in the Tarret solid thrust arm bushings but am concerned that if I also install the Tarret monoballs the NVH may be too much for the street. It is not a daily driver and I will be doing a lot of track days, but I will be driving it back and forth to the track (sometimes a 5 hr trip one way) and weekend romps on twisty two-lane.

orthojoe

I have this setup on the GT3 and there is no discernible change in NVH.
I will do the same with my GT4

Rob VN

On my 987 I had the RSS LCAs which were all solid/hiem joints and the X73 suspension. You could feel everything in the street but that was OK. On the track it was very good. What I couldn't stand was semi solid engine mounts that caused the interior to rattle.

rraustin

Thanks guys. Sounds pretty good to do both.

Rob I had stiff motors mounts in a GTI and the interior vibrations were when idling at stoplights.

gmgracing

Not only will it help with bushing deflection, but you can also gain caster adjustment with them.This is a gt3 in the photo, but our gt4 also used them in order to correct caster due to the additional camber we added.

GAZZ

I have the RSS system on my 987.2S and it makes less noise than the stock GT4.

The GT4 has wheel hop problems and 987.2S wheel hop pretty well fixed after the RSS install.

jphughan

Are monoballs more commonly installed only in the rear or both front and rear? Some cursory reading in other RL sections suggests that both paths are pursued and that putting monoballs in the front doesn't have nearly the positive impact that the rear does, but that's just cursory reading, so I'm curious to hear what someone who has investigated this more deeply or done one or even both of these ways themselves would say.

Also, looking at Tarett's site it seems that the appropriate product for the GT4 would be the monoball ends, not the monoball bearings, correct? Strange that even the latter claim to be usable with 2-piece LCAs, albeit not GT3 LCAs.

Mvez

Don't the stock thrust arm bushings have two positions for adjustment?

rraustin

From what I understand is you could do either. Monoball ends have the bearings build it and are expensive since they are a complete assembly. You can remove the stock rubber bushings from the OE ends and replace with the spherical bearings.

ShakeNBake

I think I recall AP saying that the only rubber is the thrust arm bushing. The LCA on both the upright and chassis are solid/spherical, and the strut mounts are bearings. I could have missed the detailed spec...

BGB Motorsports

I wanted to resume this discussion and share what I have found. You have rubber inner control arm bushings front and rear; you have a rubber lined caster puck in the front and an aluminum one in the rear. When we first started engineering these cars for Pro racing we struggled. I had ZERO support and while parts or money would have been great, even information would have helped us save in testing costs. One night while in my Cayman laboratory the light bulb went off that we were experiencing toe deflection. I had some of the best sports car drivers in the country struggling with this car and I stared at the 911 and then the Cayman and then the 911 and BOOM, divine inspiration occurred. The series gave us monoball rear toe links but we had to use rubber rear control arm bushings. In the back, a Cayman has 3 links vs the 911's having 5 and it finally occurred to me that a hard mounted toe link needs a spherical monoball control arm. Without it, the rubber inner control arm bushing gives up when it's loaded. The 911 has the upper dog bones to rely on for this. I made a rules request, got the inner monoballs approved and the radio chatter went silent. Suddenly "that's how this thing should have been handling all along."

I was concerned last week that by selling you all aftermarket toe links I was recreating the problem but it already exists from the factory given that the front and rear OE toe links are spherical in nature and the control arms are not. I was sort of shocked to learn this last week as I studied my car on the lift. A lot of folks don't like monoball inners because of the road noise but I think that as you all outfit your suspension wish list, you need to consider upgrading the inners. The car has such an abundance of rear tire that it isn't the ill handling car that our GS race cars were running 245/275 tires with a soft sidewall but if you are thinking about going to a more track oriented suspension package, it's worth considering. My $.02.

ShakeNBake

John, is the part we need one end of the split LCA, the side that attached to the chassis? (thanks for the data!)

myBailey07

I love that you guys provide information like this, except I have no clue what it means (But, that's all me...) In my ideal world I simply want someone that is fast and I can trust like you, or ShakeNBake, who I know is very fast and knows his car stuff, to say to me: "go to X website, buy Part Y, install it and you'll be much better off..."

morefun

John: For street DD and DE use (in conjunction with the toe links) Rear LCA mono *****.- Inboard, outboard or both? Both of my 987s were tail wagers under hard braking. You get used to it, but....

BGB Motorsports

Swapping out the inners is all that is necessary. You could even retain the OE inner arm and just press out the rubber bushing OR buy an aftermarket inner from RSS and Tarett so you can always go back to stock when you want.