suspension upgrade

[bavariankid]

hello, my E36 328i touring is equipped with the M technic package but i am thinking about an upgrade. i plan to go up to 18 inch wheels and would like a to maintain a relatively smooth ride. any after market suggestions or advice?

[e36m34life]

Welcome to the Fest'! :)

There are some things you missed out for me to give you a real accurate recomendation for which springs to buy.

If you want a low ride with very stiff springs that for some are very harsh on the streets, yet make a drastic difference in cornering and stability, then the H&R Race combined with Bilstein sports is for you.

If you want a slightly lower ride, and slightly stiffer springs, then the H&R Sports with Bilstein Sports are for you.

If you just want to lower it alot, and remain all of the stock ride qaulity, then the Tein S-Tech with Bilstein HD is for you. They have lower spring rates then stock, so they are not harsh at all, and combined with Bilstein HD's they give a very forgiving ride, and they lower your car almost more then the Race springs. But beware, they won't improve your cornering at all, maybe even a bit worse.

I had all three of these springs btw, if that adds any credibility to my post.

[FoxR]

e36m34life- Any pics of the H&R Race set-up?

[-Matt-]

Good info e36m34life.

I currently have the stock m-tech setup with >140K miles on it so I think I need to upgrade soon.

At high speeds I am starting to feel the rear of the car bounce and wobble side to side a bit - especially it the road surface is bumpy. - Feels a bit like the onset of speed wobbles on a skateboard! (I'm talking about a very subtle wobble here - but it doesn't exactly inspire confidence).

I am also noticing a slight tendency to understeer unless I flick the steering, dump the clutch or similar. I was hoping the balance of the e36 would be more to a natural oversteer.

Would the H&R race setup cure these problems for me?

[eclipse]

i have mtech on my coupe and would never change it as it is just right IMO for the roads i drive on

[-Matt-]

Eclipse, how many miles do you have on your suspension at the moment?

[eclipse]

120k ish

[-Matt-]

Don't you think it is probably quite a bit looser than originally intended by now? Or have you replaced lots of the parts with new m-tech ones?

[jasonf860]

Good info e36m34life.

I currently have the stock m-tech setup with >140K miles on it so I think I need to upgrade soon.

At high speeds I am starting to feel the rear of the car bounce and wobble side to side a bit - especially it the road surface is bumpy. - Feels a bit like the onset of speed wobbles on a skateboard! (I'm talking about a very subtle wobble here - but it doesn't exactly inspire confidence).

I am also noticing a slight tendency to understeer unless I flick the steering, dump the clutch or similar. I was hoping the balance of the e36 would be more to a natural oversteer.

Would the H&R race setup cure these problems for me?

Those wobbles your feeling are torn RTAB's, and the E36 was DESIGNED to have slight understeer.

[-Matt-]

Already replaced the rtabs (with new m-tech ones) and yeah they were wrecked - things are a lot tighter since then. I'm now being really picky but I want to get things perfect!

Why would understeer be desirable? Is there a way to tune this out with replacement suspension parts?

[eclipse]

will be replacing with new mtech but feels good to me

[B/\/\W]

I guess less experienced drivers will handle understeer better than oversteer, oversteer requires control, understeer is basically just a lack of cornering ability, thus no control required.

I believe you can set the car up for oversteer by having the suspension harder at the rear. You'll lose adhesion more easily because the tyre will spend less time on the road, so you'll end up swinging the rear out more. That's if you have a positive enough turn-in at the front for the rear to step out. Then again I could be totally wrong with this. Maybe a softer suspension at the rear but stiffer at the front would cause oversteer, because the rear of the car will not react as quickly as the front and it will not follow and step out more easily? Whatever, that could ruin the handling.

It'd just be better to increase overall grip with strut braces, bigger alloys, wider tyres etc, rather than changing the handling balance.

[-Matt-]

It's just that a lot is made of BMW's perfect balance. As a rear-wheel-drive "drivers car" I was expecting a slight natural oversteer. I was actually shocked that the first time I pushed hard into a corner I got a bit of understeer.

B/\/\W - I think your first thought was right - I should stiffen the rear suspension. Having a slightly softer front should allow grip for a positive turn in.

To be fair I have just put a new set of tyres on the rear so this could explain the extra grip at the back end.

I have also changed my tyre pressures - previously I was running with 40psi all round but after checking the wear pattern on my tyres I have to admit this was much too high. I have since reverted to the recommended pressures 2.5bar (~36psi) rear and 2.4 (~35psi) front. Things are feeling a bit too bouncy now (for me) so I may try increasing the rear pressure a little bit - hopefully this will shift the balance of grip towards the front a bit.

I will probably also switch the tyres so the new ones are up front.

Perhaps the ultimate solution will be to fit an LSD.:supdude:


bavariankid: sorry for the diversion from the original topic.

[bavariankid]

i have mtech on my coupe and would never change it as it is just right IMO for the roads i drive on

eclipse, what size wheels are u wearing?

[-Matt-]

FYI mine are 17's (235/40ZR17).

Personally I wouldn't want to go any bigger than 17 as this is going to start reducing the torque you can put down and your acceleration.

The reasons for going larger seem mainly cosmetic - but each to their own.

[bavariankid]

i see your point. i wanted to go 18" because i really like ac schnitzer's type iii two piece wheels but they only come in 18" and 19". leaning more towards oem 17" M double spoke 68s now tho...

[calvillor]

I have a 96 318TI WITH SPORT SUSPENSION, CAN i INSTALL m3 STRUTS ON MY CAR???

[eclipse]

eclipse, what size wheels are u wearing?

235/40/17

[bavariankid]

seeing that i've got the mtechnik package, should i be shopping for m3 shocks and springs?

[jasonf860]

It's just that a lot is made of BMW's perfect balance. As a rear-wheel-drive "drivers car" I was expecting a slight natural oversteer. I was actually shocked that the first time I pushed hard into a corner I got a bit of understeer.

B/\/\W - I think your first thought was right - I should stiffen the rear suspension. Having a slightly softer front should allow grip for a positive turn in.

To be fair I have just put a new set of tyres on the rear so this could explain the extra grip at the back end.

I have also changed my tyre pressures - previously I was running with 40psi all round but after checking the wear pattern on my tyres I have to admit this was much too high. I have since reverted to the recommended pressures 2.5bar (~36psi) rear and 2.4 (~35psi) front. Things are feeling a bit too bouncy now (for me) so I may try increasing the rear pressure a little bit - hopefully this will shift the balance of grip towards the front a bit.I will probably also switch the tyres so the new ones are up front.

Perhaps the ultimate solution will be to fit an LSD.:supdude:


bavariankid: sorry for the diversion from the original topic.
That will make the rear grip more and teh front less. To counter understeer you need to add air to the front and soften the rear. What you wrote is a very common misconception.

[-Matt-]

If I add air to any tyre it will reduce the contact patch and therefore the grip.

How can you explain increased tyre pressure providing more grip?

[jasonf860]

Please educate yourself on vehicle handling, over/understeer dynamics and suspension.

I'm not trying to be a jerk or anything, but there is far too much to explain in a simple thread. I've cited some excellent links below to get you started.

http://en.wikipedia.org/wiki/Car_handling#Aftermarket_modifications_and_adjustm ents_to_affect_handling

http://en.wikipedia.org/wiki/Suspension_%28vehicle%29
http://en.wikipedia.org/wiki/Oversteer
http://en.wikipedia.org/wiki/Understeer

[-Matt-]

Hmm, none of those links actually explains a plausible mechanism for increased tyre pressure to provide increased grip.

It is well established that over pressure will cause wear to only the center portion of a tyre - it is obvious that the contact patch is therefore reduced.

The attached image shows the relevant points in the table from the first link:

http://www.bimmerfest.com/forums/attachment.php?attachmentid=146880&d=1210788436

This says that to reduce understeer I need to reduce the contact patch of the rear tyres. This is in agreement with what I said as reduced contact area can be achieved by over inflating the rear tyres.

The table then contradicts itself by saying that reduced tyre pressure at the rear will reduce understeer.

As a physicist I require at least a plausible model and preferably experimental verification before I accept the validity of any information - particularly if the source is wikipedia!

I can say for certain that over inflated rear tyres gives a tendency to oversteer as I have verified this first hand. I have also proposed a mechanism for how this result is affected.

If there is a mechanism for increased tyre pressure to produce more grip then it should be possible to summarise the mechanism in a brief paragraph/sentence. Surely this would have taken less time than searching for those links.

Please do not suggest that I am uneducated - that is not the case. However, I am trying to learn more about this specific area, as are most of the readers of this thread. Perhaps you could educate us all.

I'm not trying to start an argument and I'm pretty sure you are actually right - I'm just trying to understand this better.

[big-tex]

Welcome to the Fest'! :)

There are some things you missed out for me to give you a real accurate recomendation for which springs to buy.

If you want a low ride with very stiff springs that for some are very harsh on the streets, yet make a drastic difference in cornering and stability, then the H&R Race combined with Bilstein sports is for you.

If you want a slightly lower ride, and slightly stiffer springs, then the H&R Sports with Bilstein Sports are for you.

If you just want to lower it alot, and remain all of the stock ride qaulity, then the Tein S-Tech with Bilstein HD is for you. They have lower spring rates then stock, so they are not harsh at all, and combined with Bilstein HD's they give a very forgiving ride, and they lower your car almost more then the Race springs. But beware, they won't improve your cornering at all, maybe even a bit worse.

I had all three of these springs btw, if that adds any credibility to my post.


sorry to bring up a old thread.

how harsh is the ride, with the h&r race/blisten sports? i ask because as soon as i get my car thats the first upgrade i plan on. i hate body roll in corners, and i like to take corners fast, and u-turns fast to beat traffic, i know not the brighest idea, but ya gotta make the commute fun somehow.

[eclipse]

if you hate roll change your anit-roll bars

[jasonf860]

Hmm, none of those links actually explains a plausible mechanism for increased Tyree pressure to provide increased grip.

It is well established that over pressure will cause wear to only the center portion of a tyre - it is obvious that the contact patch is therefore reduced.

The attached image shows the relevant points in the table from the first link:

http://www.bimmerfest.com/forums/attachment.php?attachmentid=146880&d=1210788436

This says that to reduce under steer I need to reduce the contact patch of the rear tyres. This is in agreement with what I said as reduced contact area can be achieved by over inflating the rear tyres.

The table then contradicts itself by saying that reduced tyre pressure at the rear will reduce under steer.

As a physicist I require at least a plausible model and preferably experimental verification before I accept the validity of any information - particularly if the source is wikipedia!

I can say for certain that over inflated rear tyres gives a tendency to oversteer as I have verified this first hand. I have also proposed a mechanism for how this result is affected.

If there is a mechanism for increased tyre pressure to produce more grip then it should be possible to summarize the mechanism in a brief paragraph/sentence. Surely this would have taken less time than searching for those links.

Please do not suggest that I am uneducated - that is not the case. However, I am trying to learn more about this specific area, as are most of the readers of this thread. Perhaps you could educate us all.

I'm not trying to start an argument and I'm pretty sure you are actually right - I'm just trying to understand this better.


I agree with you totally that it makes no sense, but I've tried it, on both front drive, rear drive and all drive vehicles and it works. It turned my understeering monster Honda into a neutral-slight oversteering car. All by going 2 lbs higher front and 2 lbs lower rear.


That being said, Think of it as your tire being part of the actual suspension, and not just the contact patch. It makes sense as a higher pressure will net a stiffer sidewall/tire.

Please don't take offense, I didn't intend to suggest you are uneducated, rather sugesting that you read, as I have, about it.