Brendan's 2014 Solid Red STU Autocross Build Thread

[Brendan]

Small update. One of the most frustrating rules regarding building a car for this class is the one regarding suspension bushings. Due to this rule we cant run nice arms like spl or voodoo and a means we are stuck using arms that are more difficult to work with.

I had a set of z1 arms which don't allow for even or easy adjustment as you have to take apart the front suspension to make any changes.

The z1 arms were durable so I would recommend them to anyone looking for affordable arms if they dont plan on adjusting the car often.

I decided to "make" a set of arms that were easy to adjust but also legal for competition. I started with a set of upper control arms from gk tech. These arms are new on the market but the company makes stuff for the 350z and other Nissan cars.

The control arms from gktech work very similar the spl arms but are like a 3rd of the cost. These arms have spherical inner rod ends but the bearing is a standard type that you can get from most stores that stock suspension parts. What I decided to do was replace the rod ends with a type that would be legal for racing. I was able to find a set of rod ends from a 4wd parts company of all places. The dimension and type were perfect for the 370z. I ended up having to swap over the guts from the bushing on the z1 arms to make the rod ends work but someone might be able to put together a set by just having a set of inner sleeves made for the rod end bushings.

Anyways, now I have a set of arms that are easy to make adjustments on and are legal for racing. The only drawback so far is that they gave up some caster. I haven't measured yet so I can say how much, but it was around +8 with the z1 arms. These seem to be more in the range of the stock upper control arms. They do allow for a much larger range of camber which is very nice. Even with the new rod ends I was able to get around -4 and there seemed to be enough threads left to get even more.

Fyi it seems like it would totally be possible to convert a set of spl arms the way I did these GKTech, I didnt want to spend $1000+ finding this out if I wasn't sure.

PXL_20210319_222049350 by brendan sobers, on Flickr

[vwhite_turbo]

Originally Posted by Brendan

The control arms from gktech work very similar the spl arms but are like a 3rd of the cost. These arms have spherical inner rod ends but the bearing is a standard type that you can get from most stores that stock suspension parts. What I decided to do was replace the rod ends with a type that would be legal for racing. I was able to find a set of rod ends from a 4wd parts company of all places. The dimension and type were perfect for the 370z. I ended up having to swap over the guts from the bushing on the z1 arms to make the rod ends work but someone might be able to put together a set by just having a set of inner sleeves made for the rod end bushings.

Fyi it seems like it would totally be possible to convert a set of spl arms the way I did these GKTech, I didnt want to spend $1000+ finding this out if I wasn't sure.

PXL_20210319_222049350 by brendan sobers, on Flickr

Man, this is very helpful and so close to exactly what I need. I am trying to do the same thing but using the SPL arm. The SPL rod end is a 5/8-18 RH thread, which barnes4wd.com doesn't seem to have. I will email them to see if they can custom make the exact mount with a different thread size.

I know Speedway sells one that has the 5/8-18 thread, but their bushing mounting width is only 1.3" which is too short and the housing ID is only about 1" which is a little small.

Do you happen to know the width of the forged housing without the bushing?

[gomer_110]

Originally Posted by vwhite_turbo

Man, this is very helpful and so close to exactly what I need. I am trying to do the same thing but using the SPL arm. The SPL rod end is a 5/8-18 RH thread, which barnes4wd.com doesn't seem to have. I will email them to see if they can custom make the exact mount with a different thread size.

I know Speedway sells one that has the 5/8-18 thread, but their bushing mounting width is only 1.3" which is too short and the housing ID is only about 1" which is a little small.

Do you happen to know the width of the forged housing without the bushing?

With some shims (think precise thickness washers) you can use the Speedway rod ends without too much difficulty. That's what I've been doing on mine for a number of years now.

[vwhite_turbo]

Originally Posted by gomer_110

With some shims (think precise thickness washers) you can use the Speedway rod ends without too much difficulty. That's what I've been doing on mine for a number of years now.

Thanks. I thought about that as a possible solution but it technically isn't legal in ST, even though it offers no performance advantage but you know how it goes.

[Brendan]

Originally Posted by vwhite_turbo

Man, this is very helpful and so close to exactly what I need. I am trying to do the same thing but using the SPL arm. The SPL rod end is a 5/8-18 RH thread, which barnes4wd.com doesn't seem to have. I will email them to see if they can custom make the exact mount with a different thread size.

I know Speedway sells one that has the 5/8-18 thread, but their bushing mounting width is only 1.3" which is too short and the housing ID is only about 1" which is a little small.

Do you happen to know the width of the forged housing without the bushing?

38mm