Questions about Suspension/Drivetrain upgrades

[GarbageCanE30]

What's up everyone. I'm currently building my 89' 325is and am wondering what the recommended upgrades for a 300~hp e30 is. I've seen a lot of higher end performance builds running z3m axles/control arms but it seems incredibly difficult to come by those parts. Is a 5 lug conversion recommended? Should the stock differential be fine? My issue here is not cost but difficulty of installation/difficulty of locating the parts. Also I know that 300 hp isn't a crazy amount of power, but I'd like to emphasize the handling of this build and replace or upgrade as many of the old rusty parts as I can. Let me know what you guys have done and what you think works best. Thanks

[Slybeanx]

I dont think you need to beef up your suspension until you are past 450-500 hp, you should probably be fine.
I would reenforce your subframe though if you are doing suspension bits like bushings. Are you chaging wheel sizes/ lowering? if so look at raised subframe bushings/ camber toe kits. thats just my .02

[roguetoaster]

Don't think you need to upgrade too much on the driveline side, but you are really going to want more braking performance, and ideally more than a 205 tire considering the speeds that a 300HP E30 can attain. Additionally, maybe slightly improving your suspension/differential location may be in order, depending on how you drive.

[roguetoaster]

Don't think you need to upgrade too much on the driveline side, but you are really going to want more braking performance, and ideally more than a 205 tire considering the speeds that a 300HP E30 can attain. Additionally, maybe slightly improving your suspension/differential location may be in order, depending on how you drive.

[GarbageCanE30]

Don't think you need to upgrade too much on the driveline side, but you are really going to want more braking performance, and ideally more than a 205 tire considering the speeds that a 300HP E30 can attain. Additionally, maybe slightly improving your suspension/differential location may be in order, depending on how you drive.

Currently the car has bilstein shocks and h&r springs I believe, and I was considering doing a big brake kit if I can find a decent set for a decent price. It seems like at that point I'd likely want to do a 5 lug conversion however. The car is also on Ronal LS rims that I believe are 16's and quite a bit wider then stock. I believe they'll have plenty of rubber to handle the power, but if I were to go 5 lug they'd likely go up for sale. Once again, I'm quite new to all of this and there's no real definitive guide on the "best" way to upgrade an e30 top to bottom, so all I can do is ask questions and try and figure out what works best for me, and thank the people who offer their knowledge along the way!!

[Staszek]

You dont have to go crazy, you also dont have to do a 5 lug, you can but not necessary. I stayed 4 lug on my S54 with over 300 hp and upgraded the brakes to a Wilwood BBK. There are plenty of 4 lug wheels that will work if you get the 15" version of the Wilwoods, or you can get Apex wheels in 4 lug that are 17's. You can also get adapters and run Mazda brakes and I am sure a few others.

You can just upgrade the suspension with better shocks/springs (or go coilover if you want to spend the money), and sway bars. The car is light it doesnt need much unless you want to track it.

I would refresh all the bushings (subframe, RTB etc), they are likely shot, you can go with Poly, but to be honest, the OEM ones are just fine especially if its more a cruiser with some auto cross and light track time. If you are building it for the track go with a harder bushing.

Definitely reinforce the subframe and front and rear sway bar connections, they are the weaker points.

The diff and axles are just fine stock as long as they are in good shape.

If money is no object, I would upgrade the steering rack (tie rods too) that makes a huge difference in how the car drives. I went from an E30 rack to an E46 ZHP rack and it was a big difference.

You can get a little crazy with with upgrades, if I had to say the min for 300+ Hp is springs, shocks, sways, bushings wider tires and brakes. You can even get away way with the stock springs shocks and sways if they are in good shape, I would prioritize brakes and more rubber.

[GarbageCanE30]

You dont have to go crazy, you also dont have to do a 5 lug, you can but not necessary. I stayed 4 lug on my S54 with over 300 hp and upgraded the brakes to a Wilwood BBK. There are plenty of 4 lug wheels that will work if you get the 15" version of the Wilwoods, or you can get Apex wheels in 4 lug that are 17's. You can also get adapters and run Mazda brakes and I am sure a few others.

You can just upgrade the suspension with better shocks/springs (or go coilover if you want to spend the money), and sway bars. The car is light it doesnt need much unless you want to track it.

I would refresh all the bushings (subframe, RTB etc), they are likely shot, you can go with Poly, but to be honest, the OEM ones are just fine especially if its more a cruiser with some auto cross and light track time. If you are building it for the track go with a harder bushing.

Definitely reinforce the subframe and front and rear sway bar connections, they are the weaker points.

The diff and axles are just fine stock as long as they are in good shape.

If money is no object, I would upgrade the steering rack (tie rods too) that makes a huge difference in how the car drives. I went from an E30 rack to an E46 ZHP rack and it was a big difference.

You can get a little crazy with with upgrades, if I had to say the min for 300+ Hp is springs, shocks, sways, bushings wider tires and brakes. You can even get away way with the stock springs shocks and sways if they are in good shape, I would prioritize brakes and more rubber.

Fantastic man. Thank you so much for taking the time to provide all that info. Do you happen to have a link to the 4 lug bbk you bought? Would love to take a look. Just tracked down an aftermarket upgraded master cylinder for a great price so that's one piece of the puzzle completed. As far as the steering rack upgrade, is that a difficult/time intensive modification with fabrication required? I'm trying to stay away from that if I can as I'm doing most of the work myself to allow for more part money and less labor money. However I have seen most higher performance/higher end builds that tends to be a given. Thanks again.

[Staszek]

Fantastic man. Thank you so much for taking the time to provide all that info. Do you happen to have a link to the 4 lug bbk you bought? Would love to take a look. Just tracked down an aftermarket upgraded master cylinder for a great price so that's one piece of the puzzle completed. As far as the steering rack upgrade, is that a difficult/time intensive modification with fabrication required? I'm trying to stay away from that if I can as I'm doing most of the work myself to allow for more part money and less labor money. However I have seen most higher performance/higher end builds that tends to be a given. Thanks again.

You can upgrade to an E36 rack and its plug and play with some spacers on the stock subframe. There are a lot of threads on here on steering rack swaps, I bought mine newly refurbished from Rack Doctor, but you can find them cheap online depending on what you get. The Z3 ones and the E46 ZHP ones are the most expensive.

Here is the link to the brakes. I got the 16" wheel version but they sell 15" versions if you are getting smaller wheels.

https://www.iemotorsport.com/product...30-brake-kits/

BTW how are you planning on getting 300hp? Turbo? If a swap that opens up way more things.

[GarbageCanE30]

You can upgrade to an E36 rack and its plug and play with some spacers on the stock subframe. There are a lot of threads on here on steering rack swaps, I bought mine newly refurbished from Rack Doctor, but you can find them cheap online depending on what you get. The Z3 ones and the E46 ZHP ones are the most expensive.

Here is the link to the brakes. I got the 16" wheel version but they sell 15" versions if you are getting smaller wheels.

https://www.iemotorsport.com/product...30-brake-kits/

BTW how are you planning on getting 300hp? Turbo? If a swap that opens up way more things.

Im about 99% sure at this point I'm buying an early 90s dinan turbo kit for the m20, which is said to make about 300 hp on 10-11 psi. Ive been flip flopping between an s5x swap and stickin with the m20 and I think I've finally made up my mind. Ah yes, was looking at those wilwood kits on IE kinda figured that's what it would be. Only difference between the 15/16 inch kits I assume is the rotor size?

[varg]

Most 5 lug conversions I've seen boil down to the owner wanting to have $$$$ 5 lug wheels and are not practically necessary . It is not even close to the realm of necessity with a mere 300whp, even big brake kits aren't necessary there unless you're going to track the car. The stock size brakes are good stuff when not neglected or fitted with econo pads, and unless you're doing repeated slowing from high speeds like you would on a track they aren't going to fade on you. You'd be hard pressed to find a situation where you need a big brake kit for any street driven E30, let alone a 5 lug conversion. As for some of the above points, a steering rack swap should be the first handling mod you do. My Z3 rack made the single biggest improvement in the feel of the car of any other suspension mod I did. Stock E30 steering sucks.

[GarbageCanE30]

Most 5 lug conversions I've seen boil down to the owner wanting to have $$$$ 5 lug wheels and are not practically necessary . It is not even close to the realm of necessity with a mere 300whp, even big brake kits aren't necessary there unless you're going to track the car. The stock size brakes are good stuff when not neglected or fitted with econo pads, and unless you're doing repeated slowing from high speeds like you would on a track they aren't going to fade on you. You'd be hard pressed to find a situation where you need a big brake kit for any street driven E30, let alone a 5 lug conversion. As for some of the above points, a steering rack swap should be the first handling mod you do. My Z3 rack made the single biggest improvement in the feel of the car of any other suspension mod I did. Stock E30 steering sucks.

Gotcha, seems more and more like one of the essential upgrades will be the steering rack. The big brake kit would be less so out of necessity for performance and moreso because I think it completes the look of a well thought out and high investment build. Its the shoe laces that tie everything up nicely whether or not they're needed for performance. In that case though I'll probably forego the 5 lug and just keep an eye out for a z3 rack as I've seen a couple part outs on Facebook. Hopefully the steering racks are still available! Thanks for your input sir

[Staszek]

Im about 99% sure at this point I'm buying an early 90s dinan turbo kit for the m20, which is said to make about 300 hp on 10-11 psi. Ive been flip flopping between an s5x swap and stickin with the m20 and I think I've finally made up my mind. Ah yes, was looking at those wilwood kits on IE kinda figured that's what it would be. Only difference between the 15/16 inch kits I assume is the rotor size?

I believe so but I would call them.

[Staszek]

Im about 99% sure at this point I'm buying an early 90s dinan turbo kit for the m20, which is said to make about 300 hp on 10-11 psi. Ive been flip flopping between an s5x swap and stickin with the m20 and I think I've finally made up my mind. Ah yes, was looking at those wilwood kits on IE kinda figured that's what it would be. Only difference between the 15/16 inch kits I assume is the rotor size?

I would stick with the turbo over the swap unless you go with an S50 which you will still need to do work to to get over 300hp. There are just so many other things you need to take care of in a swap that are not bolt on.

[dmanb2b]

Gotcha, seems more and more like one of the essential upgrades will be the steering rack. The big brake kit would be less so out of necessity for performance and moreso because I think it completes the look of a well thought out and high investment build. Its the shoe laces that tie everything up nicely whether or not they're needed for performance. In that case though I'll probably forego the 5 lug and just keep an eye out for a z3 rack as I've seen a couple part outs on Facebook. Hopefully the steering racks are still available! Thanks for your input sir

I picked up my z3 rack on ebay. remaned from detroit axle iirc

[drzhivago1965]

Hey dmanb2b, How's the Detroit Axle rebuild working out? Was it a true Z3 rack with 2.7 turns lock to lock?