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-   -   Z3(I6) Trailing arm compatibility (http://www.318ti.org/forum/showthread.php?t=44947)

winner9101 11-05-2020 11:01 PM

Z3(I6) Trailing arm compatibility
 
Quick question, probably posted on an older forum but I cannot seem to find my answer anywhere. I have a 318ti with 3.46 Torsen diff from a z3 and e30 axles on stock trailing arms. I am looking to widen the rear to compliment the widebody kit that is going on the car. I know the 6 cyl Z3 trailing arms are 20mm wider and are an easy swap when combined with the complimentary 6 cyl z3 axles. Will 318ti rotors and calipers mount to the z3(I6) trailing arm? I saw somewhere that the z3 hub is 5mm wider than the 318ti hub so I think that would also be what I want? That would give me a total 25mm wider with the z3(I6) trailing arm/hub/axle assembly over the 318ti. For the swap to z3(I6) trailing arms the ebrake cables and metal brake lines that come with the trailing arm assembly are the ones I would want to use right? In order to simplify things I am most likely getting a Sparta brake kit for the rear so due to the 5mm wider hub, I would need a z3(I6) kit, not a 318ti rear kit right? Thanks for your help and sorry if my questions have been answered somewhere else already. Am I correct in saying that all I will need is z3(I6) trailing arm/axle/hub assembly, and z3(I6) big brake kit?

anassa 11-05-2020 11:20 PM

DUDE!! How is the ti ? ?

What all has gone wrong/broke or needed to get fixed? :eek:

Here is bunch of info from when I was looking at doing the exact same thing:

http://www.318ti.org/forum/showpost....4&postcount=30

Here is a bunch of brake info:

http://www.318ti.org/forum/showthread.php?t=24547

As to your questions, your correct in that you need to use the z3 rotor, the caliper from ti will bolt on, just like I currently have z3 rear caliper bolted on, so those are changeable, but the rotor isn't.

Did you look at the SRS rear adaptor?

https://srs-concept.com/product/e36-...e-adapter-kit/

They also have an adapter that allows for m3 caliper/rotor, but you loose your ebrake.

The ebrake cable will probably not be long enough, I know that was a problem before for others but I am not sure how they solved the issue. When I get home I can search a bit more, but I don't know the answer off the top of my head.


Oh btw I really miss that 3.46 diff, if you want a 3.15, I can trade you :wink:

winner9101 11-05-2020 11:41 PM

The car has been great so far! I have been slowly making changes and preparing the car for a widebody kit that I got for the car and for BAR. Funnily enough, I probably should have thought about changing the trailing arms when I had the entire rear subframe out a couple of weekends ago to change to the subframe riser bushings and change the RTABs.

Nothing broke on the car, but I was looking into widening the rear track with the z3(I6) trailing arms. After I posted I started looking at some of your older threads and was reading all about your plans and modifications on the rear end. I was about to go and measure the rear track to see, but you probably remember, does the car already have the z3 trailing arms? With the wider trailing arms are the spring perches in the same location? What about the lower shock bolt?

I have looked into the SRS adapter, but I might be able to source a Sparta Big brake kit rather than something OEM BMW so I am probably going to go with that instead. Ultimately it looks like I am going to be running BBS 18x11 wheels so I don't have to worry about using smaller rotors.

Ultimately, if there is too much hassle involved in swapping to the z3(I6) trailing arm then I will just compensate with wheel offset or spacers.

I'll stick with the 3.46 for now! If I ever go to something more aggressive like a diffsonline unit I'll let you know

anassa 11-05-2020 11:57 PM

Quote:

Originally Posted by winner9101 (Post 392260)
The car has been great so far! I have been slowly making changes and preparing the car for a widebody kit that I got for the car and for BAR. Funnily enough, I probably should have thought about changing the trailing arms when I had the entire rear subframe out a couple of weekends ago to change to the subframe riser bushings and change the RTABs.

Nothing broke on the car, but I was looking into widening the rear track with the z3(I6) trailing arms. After I posted I started looking at some of your older threads and was reading all about your plans and modifications on the rear end. I was about to go and measure the rear track to see, but you probably remember, does the car already have the z3 trailing arms? With the wider trailing arms are the spring perches in the same location? What about the lower shock bolt?

I have looked into the SRS adapter, but I might be able to source a Sparta Big brake kit rather than something OEM BMW so I am probably going to go with that instead. Ultimately it looks like I am going to be running BBS 18x11 wheels so I don't have to worry about using smaller rotors.

Ultimately, if there is too much hassle involved in swapping to the z3(I6) trailing arm then I will just compensate with wheel offset or spacers.


Which subframe risers did you use? How much of a difference did it make?

I was eventually going to go with the IE weld-in posi lock toe and camber kit, for some adjustability.

For the spring peach mounting points, I don't think that will be an issue, since people swap in the z3m rear and it works fine, as well as the ti rear or z3m rear on e30's

https://www.r3vlimited.com/Media/e30...081305-005.jpg

That is a picture of the e30 and z3m trailing arm compared, I think the increase in width comes after the mounting point.

I never got to install the z3 trailing arms, so they are just the stock ones.

When you get a chance post up an introduction thread with a few pictues!

winner9101 11-06-2020 12:22 AM

Quote:

Originally Posted by anassa (Post 392261)
Which subframe risers did you use? How much of a difference did it make?

The car initially was lowered with the ground control rear shock and spring as a result of the significantly shorter shock, and the car was slammed! The fender was overlapping the tire by about 10mm. Surprisingly, the shocks are stiff enough so I don't think anything was rubbing.

I used the Condor 12mm risers and sure enough, the car did look to be about 12mm lower (which was way too much for stock rear quarters) the GC spring comes with an adjustable collar that I was able to raise about 12mm (to the middle of the total adjustment) to counteract the lowering from the subframe risers. However, the main advantage should be less camber when the car is excessively lowered. At the moment I am not dialing in fitment, but rather preparing for when the widebody kit gets installed.

Considering I got quoted $450 for a set of used trailing arms and axles from a z3(I6), I might leave it the way it is and compensate with spacers if needed. Either that or steal the rear end off of my neighbor's z3 in the middle of the night. He wouldn't notice if I put my trailing arms and axles back on his car right? lol

I've wanted to make a thread for all the happenings on the car, but it is easier to just post to IG. When things are all said and done I might make a summary thread.

anassa 11-06-2020 01:16 AM

Quote:

Originally Posted by winner9101 (Post 392262)
The car initially was lowered with the ground control rear shock and spring as a result of the significantly shorter shock, and the car was slammed! The fender was overlapping the tire by about 10mm. Surprisingly, the shocks are stiff enough so I don't think anything was rubbing.

I used the Condor 12mm risers and sure enough, the car did look to be about 12mm lower (which was way too much for stock rear quarters) the GC spring comes with an adjustable collar that I was able to raise about 12mm (to the middle of the total adjustment) to counteract the lowering from the subframe risers. However, the main advantage should be less camber when the car is excessively lowered. At the moment I am not dialing in fitment, but rather preparing for when the widebody kit gets installed.

Considering I got quoted $450 for a set of used trailing arms and axles from a z3(I6), I might leave it the way it is and compensate with spacers if needed. Either that or steal the rear end off of my neighbor's z3 in the middle of the night. He wouldn't notice if I put my trailing arms and axles back on his car right? lol

I've wanted to make a thread for all the happenings on the car, but it is easier to just post to IG. When things are all said and done I might make a summary thread.

What spring rates are you using?

Also keep in mind that the lower the car is more toe out you will also have in the rear (or toe in? I thought it was toe out?) But toe definitely changes too and will impact the handling dynamic.

Ya $450 doesn't seem that good, I think I picked up the entire rear end for something like 300, diff included, but I eventually only used the diff, but you should be able to find the trailing arms for cheaper. I still want to go that route eventually, OEM widening sounds fun, no other e36 can do that.

I don't think your neighbor will notice! haha

That would be cool to see!

I don't think I ever updated my own thread to say that it was sold, and I haven't started a new one for the helrot one . . . so I am also dragging my feet, life has been wwwaaayyy to busy. But someday I will get around to it.

winner9101 11-06-2020 03:43 AM

Quote:

Originally Posted by anassa (Post 392263)
What spring rates are you using?

I am running 440 lbs/inch and 660 lbs/inch
Quote:

Originally Posted by anassa (Post 392263)
Also keep in mind that the lower the car is more toe out you will also have in the rear (or toe in? I thought it was toe out?) But toe definitely changes too and will impact the handling dynamic.

Yeah, I don't want to excessively lower the car. I just think that with the widebody kit it is going to end up lower than it would be with stock quarter panels. Hopefully, I will be able to find the right parts at the right price. I also need to source the m3 side skirts (twisted) for the kit to fit properly. If I remember correctly, the 2dr M3 skirts fit and the 4dr skirts don't. Looking at some of your older posts you said the track could be widened from 1413mm too 1494mm which would be roughly 40mm on each side wider. When I looked at e30 forums (https://www.e30zone.net/e30wiki/inde...Lug_Conversion) I saw that each trailing arm is only 20mm wider. Compared to an E30 the hub from the z3(I6) is 23.5mm wider, but the 318ti is 18mm wider than E30 which means the hub will add only ~5mm per side. This means I am at roughly 25mm wider per side, short of the 40 mm from your thread. Do you know where the remaining 15mm per side is?

anassa 11-18-2020 11:04 PM

Quote:

Originally Posted by winner9101 (Post 392264)
I am running 440 lbs/inch and 660 lbs/inch

Sorry for the late reply!

I am running 400lb front and 700 rear, the car actually rotates! Ya our rear definitely needs more spring.

This was a very interesting read for me when I was thinking spring rates:

https://www.bimmerforums.com/forum/s...ts-in-Z3-Coupe



Quote:

Originally Posted by winner9101 (Post 392264)
Yeah, I don't want to excessively lower the car. I just think that with the widebody kit it is going to end up lower than it would be with stock quarter panels. Hopefully, I will be able to find the right parts at the right price. I also need to source the m3 side skirts (twisted) for the kit to fit properly. If I remember correctly, the 2dr M3 skirts fit and the 4dr skirts don't. Looking at some of your older posts you said the track could be widened from 1413mm too 1494mm which would be roughly 40mm on each side wider. When I looked at e30 forums (https://www.e30zone.net/e30wiki/inde...Lug_Conversion) I saw that each trailing arm is only 20mm wider. Compared to an E30 the hub from the z3(I6) is 23.5mm wider, but the 318ti is 18mm wider than E30 which means the hub will add only ~5mm per side. This means I am at roughly 25mm wider per side, short of the 40 mm from your thread. Do you know where the remaining 15mm per side is?

If you look at the post above, that I had made previously on the widening idea, it was just done with taking the track width from the factor specs and doing some basic addition and subtraction. That is it. So there may be other factors that would account for that difference, especially since I have not done it myself and measured it personally. I used it more to give myself a rough idea. If I was going that route, I would go with the trailing arms, see how much difference it actually makes, then choose my wheels size/specs/setup and then figure out what widebody works for the setup.

On the side skirts - there shouldn't be a difference in length for the side skirts of ti/coupe/sedan/convertible, from what I remember they are all interchangeable. They all have the same track width, that I know for sure. The fenders/doors are different but side skirts are the same I think.


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