after a ton of searching i was unable to come up with any good information on which to go with. i know the urethane will make things tighter and all, but ive heard they will wear out and crack fast and make it hard to adjust the camber/toe in the rear vs just using new OEM bushings. so i need some honest data backed by experiences on which will be the best for longevity and performance. i want to get my stuff ordered this week so i can have to rear end done by thunderhill in april. also open to suggestions oh where to get the bushings for the rear end. was just going to go with AKG 75D diff, subframe mount and weld in adjustment eccentrics. Thanks for the input!
Urethan vs OEM Trailing arm bushings
Ranger
#2
You are not going to find consensus on this, sorry. There are folks reporting pros and cons of each.
Eccentric rtabs and the weld-on toe/camber kits allow you to get your desired alignment by forcing the trailing arm pivot points off axis. The down side of this is that it puts stress on the pivot points. Since both solutions do the exact same thing…force the pivot points off-axis, the stresses are the same. Soft bushings will reduce the stress by allowing your desired alignment to become undesired. Harder bushings will work harder to keep your desired alignment but could be overwhelmed by stress.
If it was me, I’d put in the harder bushings and see what happens. Potentially you could decide later that they can’t handle the stress and you replace them with softer ones.
Fortunately swapping out rtab bushings is quick and easy.
kgobey
#4
Ranger knows his sh*t…
There is a lot of advice out there. It’s not all the same to be honest… But you need to make some decisions - so here are a few words of learned experience.
[ul]
[li]Race cars are faster when the alignment you have spent time researching is maintained for optimal grip.
[/li]
[li]Race cars that are faster, tend to run through parts faster
[/li]
[li]Tires wear less quickly when the chosen alignment is correct and maintained properly under cornering and acceleration forces.
[/li]
[li]New drivers are able to control a car with more confidence and therefore drive more quickly when the car has a certain amount of compliance.
[/li]
[li]Compliance is another way of saying soft. Soft cars don’t maintain the desired alignment as we as stiff cars.
[/li]
[li]There are trade offs in everything you do, not just race cars, and there are no absolutes of grantees in race car set up. You can mix and match bushings on a trailing arm to reach a desirable compromise.
[/li]
[li]No 2 E30’s are the same apparently - well, this issue isn’t as extreme as the S944, but it’s there all the same.[/li]
[/ul]
Let me ask a couple of questions… Do you notice any particular advantage other car(s) have been having over you while cornering or mid-corner acceleration or deceleration??
jlevie
#5
I tried poly RTAB’s with weld-in camber/toe adjusters and found that I had to tack weld the adjusters to have the alignment hold over a weekend. I was using very short tacks, to make it easy to undo, and had one pop and toe changed. Once I went to OE bushings the settings have been stable. I figure that what I give up in the greater compliance of the OE bushings is much less that having camber or toe change during an event.
kgobey
#6
There was a lot of talk about putting in rubber at the body or the suspension end of the trailing arm - but not the other a fews years go… I really don’t remember the details and it was related to ITS
Speedracer
#7
[quote=“kgobey” post=55578]Ranger knows his sh*t…
There is a lot of advice out there. It’s not all the same to be honest… But you need to make some decisions - so here are a few words of learned experience.
[ul]
[li]Race cars are faster when the alignment you have spent time researching is maintained for optimal grip.
[/li]
[li]Race cars that are faster, tend to run through parts faster
[/li]
[li]Tires wear less quickly when the chosen alignment is correct and maintained properly under cornering and acceleration forces.
[/li]
[li]New drivers are able to control a car with more confidence and therefore drive more quickly when the car has a certain amount of compliance.
[/li]
[li]Compliance is another way of saying soft. Soft cars don’t maintain the desired alignment as we as stiff cars.
[/li]
[li]There are trade offs in everything you do, not just race cars, and there are no absolutes of grantees in race car set up. You can mix and match bushings on a trailing arm to reach a desirable compromise.
[/li]
[li]No 2 E30’s are the same apparently - well, this issue isn’t as extreme as the S944, but it’s there all the same.[/li]
[/ul]
Let me ask a couple of questions… Do you notice any particular advantage other car(s) have been having over you while cornering or mid-corner acceleration or deceleration??[/quote]
Currently i have an entirly stock rear end, and i am also still trying to dial the car in. i am currently running about 6-8seconds behind the front runners, although i think the majority of that time is due to my inexpirence on the track. however i do feel like the car is a little unstable in the rear end at the last dry event. i have made some changes to the car, but the last event was in the wet so i didnt gain any usable data. i think what ill end up doing is using the OEM bushings for now as i think the main problems are with the entirety of the rear end being old.
kgobey
#8
The best way to improve any E30’s handling is to add the eccentric Front LCA bushings (any brand will work as long as they are “quality items”)… The next most important thing is to ditch the rear Subframe bushings - ASAP
From here you start to get into the rear end for real. The rear end of an E30 is a wonder of design-perfection - for a street car… Really, the rear end needs to be pulled out, inspected for bent parts and then reassembled with a lot of modifications to the bushings… Spherical bearings and relocated pickup points would net us the best results, but in our case - working within the rules set we have, a mixed bag of new rubber and Urethane along with the Diff bushings replaced (while in there) will net you a good working rear suspension set up.
The Alignment tabs from Ireland are the way to go IMO.
(note: I have been informed by an old associate of mine - last name begins in Ir and ends in land that there a lot of time tied up in the rear end of an E30)