Suspension Upgrades - Best Bang for Buck?

[Aussieboxy]

Tracked my 135 the other day for the 1st time & was a bit disappointed in the handling performanceNamely understeer & body roll.

Suspension is stock. Have 15mm spacers all round & running Khumo KU39, 255 back, 225 front (I think. Front is std size)

I'm (read the misses) not interested in spending a lot to improve the handling & would like a staged approach.

I hear that upgrading the front end to M spec makes a significant improvement in turn in & might go for slightly lowers springs provided ride comfort is not significantly degrades.

Any suggestions would be welcomed.

[Greg FEightytwo]

I hate to say it but there really isn't a solution that will not cost you some money to fix the issues you don't like about the suspension. I did a full m3 suspension upgrade and it was not cheap by far but the improvement is significant for sure.

Subframe bushings are awful. When they were pulled out, I could flex them with my hand. its about 1200.00 for those installed

You can get away with just springs and stock shocks but that is a huge improvement changing them out as I've been in cars that have it compared to my ride. I would pull the alignment pins and push the strut in all the way to gain some more camber. That's free.

Sway bars and the strut bar are cheap and easy to install.

The control arms in the front and rear are a big help as they have bearing's instead of flimsy bushings

I have the camber links and 1m shocks which are stiffer and have a bearing to aluminum instead of bushing that moves up and down.

The toe links you can get adjustable ones that help as well.

I hope this helps.

G

Originally Posted by Aussieboxy

Tracked my 135 the other day for the 1st time & was a bit disappointed in the handling performanceNamely understeer & body roll.

Suspension is stock. Have 15mm spacers all round & running Khumo KU39, 255 back, 225 front (I think. Front is std size)

I'm (read the misses) not interested in spending a lot to improve the handling & would like a staged approach.

I hear that upgrading the front end to M spec makes a significant improvement in turn in & might go for slightly lowers springs provided ride comfort is not significantly degrades.

Any suggestions would be welcomed.

[John_01]

You will get some useful handling improvement with the following changes:
1) More front camber with M3 front arms + front tension struts to reduce understeer. (Alternatively get camber plates)
2) E92 M3 Front sway bar to reduce body roll.
3) Upgrade rear subframe bushings with either M3 items, Polyurethane 2-piece, or the polyurethane inserts. This makes the car more precise and surprisingly allows the front end to grip better and feel more connected to the road.

Upgrade springs and dampers is also recommended if you want to do the job properly.

[BMW86]

Coilovers make the biggest difference.

[ian48]

As far as staged goes, I would say go with the rear subframe bushing swap first. If you have two jacks and some stands, it is a job that is doable in a day. Doing it yourself will save you a lot of money. They literally transform the back end. I'm sure you have already read other peoples experiences though.
As far as anything after that it's really up to you.

[TheSt|G]

Let's start from the top. What kind of budget are we working with and are you capable of doing your own work?

Skip the lowering springs, easily the least important suspension change that will destroy your ride quality without an appropriately matched damper.

[3002 tii]

Originally Posted by John_01

You will get some useful handling improvement with the following changes:
1) More front camber with M3 front arms + front tension struts to reduce understeer. (Alternatively get camber plates)
2) E92 M3 Front sway bar to reduce body roll.
3) Upgrade rear subframe bushings with either M3 items, Polyurethane 2-piece, or the polyurethane inserts. This makes the car more precise and surprisingly allows the front end to grip better and feel more connected to the road.

Upgrade springs and dampers is also recommended if you want to do the job properly.

+1 although I will add you may as well add Dinan camber plates and avoid 2 alignments and swap to stickier tires as soon as you wear out your current set. Kumho Ecsta are not track worthy IMO.

[TheSt|G]

Originally Posted by 3002 tii

+1 although I will add you may as well add Dinan camber plates and avoid 2 alignments and swap to stickier tires as soon as you rear out your current set. Kumho Ecsta are not track worthy IMO.

Let's be frank, Kumhos aren't street worthy.

[Aussieboxy]

Thanks guys. I appreciate the feedback.

What specific parts are required to upgrade the front end to M Spec?

I'm reasonably proficient with mechanical/electrical work on cars as I have been doing most of the work on my cars for many years like clutch replacements, head gaskets, brakes etc, so most things don’t faze me.
Rear bushings are definitely on the list, but I read that a special tool is required for removal. Anyone have further info on this.

As for the Khumo’s I changed to them from the Bridgestone Run Flats & they were a definite improvement. They had some pretty good write ups & until the track day I have been pretty happy with them. What alternate would you suggest in a similar price range?

[TheSt|G]

HPAutowerks rents the tool.

We still need the budget for the mods.

What are you looking for in a tire?

[128Convertibleguy]

Originally Posted by TheSt|G

What are you looking for in a tire?

More specifically.

Do you basically want a track tire you can use on the street, or a street tire you can use on the track? Or will you get some dedicated track tires? You can't have one tire that's the best for both.

Do you have to deal with snow, ever? If so, do you plan to get winter tires? Do you have to deal much with cold temperatures, say below 10C or 50F? Wet weather?

How important are ride and noise to you?

Tire choice is simple, if you only want one thing. Or if you're willing to get maybe three sets. Most of us deal with many things, and it's not simple at all.

[Aussieboxy]

I'm after street tyres essentailly as I've only tracked the car once & will not be doing so on a regular basis. Ride & noise are not critical factors.

As for snow I live in a subtropical climate so the lowest it gets is prob 5 degrees Celcius which is about 40F. Wet weather performance is important but not critical.

As I am in Aus there is no HP Autoworks here to rent the tool from. What other option are there?

Budget....whatever I can convince the boss...which will be as little as possible.

Thanks guys

[Ginger_Extract]

Dampers, and subframe bushings/inserts. Mainly dampers. The 135i is so critically under-dampened from the factory, that I am amazed people are running lowering springs on them. It must ride horribly.

[wjk_glynn]

Originally Posted by Aussieboxy

...Any suggestions would be welcomed.

I'd asked HPA a somewhat similar question in a different thread, here's what they said: http://www.1addicts.com/forums/showp...07&postcount=8

Karl.

[TheSt|G]

Originally Posted by Ginger_Extract

Dampers, and subframe bushings/inserts. Mainly dampers. The 135i is so critically under-dampened from the factory, that I am amazed people are running lowering springs on them. It must ride horribly.

People are spectacularly out of touch/idiotic when it comes to performance modding, and that's before "stance" and other such garbage comes into play.

[Kgolf31]

Originally Posted by TheSt|G

People are spectacularly out of touch/idiotic when it comes to performance modding, and that's before "stance" and other such garbage comes into play.

I'm stanced with -3.6* of camber yo

[TheSt|G]

Originally Posted by Kgolf31

I'm stanced with -3.6* of camber yo

Hopefully with stretched tires to keep them taunt through the turns.

[3002 tii]

Originally Posted by TheSt|G

Hopefully with stretched tires to keep them taunt through the turns.

215's on a 9.5 broski, that's the way to do it.

[chris82]

Originally Posted by Ginger_Extract

Mainly dampers. The 135i is so critically under-dampened from the factory, that I am amazed people are running lowering springs on them. It must ride horribly.

THIS^^^^^

Stock dampers are awful, I hate them. Forget the M3 parts and get quality spring/damper setup.

[John_01]

Yes the stock dampers are really too soft as they are compromised to match the awful runflat tires. The only issue with upgrading dampers is you need to match to springs.
If you are undecided on changing the springs, you can do the other mods first (rear sub frame bushings, front camber, front sway bar). That may change your feeling about the cars handling ability.

[Clovef]

I think there are a few cheaper and easier options that make the most sense.

Rear subframe bushings: $179 from whiteline. These will have very similar benefits to the m3 bushings but they are two pieces for ease of instillation. You don't need a special tool for these and most DIYers seem to be able to do these in 3 hours pretty easy, while trained mechanics say the m3 bushings take twice as long and are a PITA so 2 part bushings are a great choice.

Shocks. If I was doing it again and did not often track I think I would just do shocks and skip the springs. A stiffer shock can help control body roll and can be left soft for the street allowing some compromise.

E92 or e93 front anti sway bar and brackets. ~$280 there is some debate if this adds or reduces under steer. If you read an old book it will tell you a stiffer front bar will keep a little less weight on your outside tire in a turn and decrease your grip. What people seem to experience is that it keeps the front from rolling over and creating positive camber. The FSB reducing that roll over in the suspension allows the suspension to maintain a larger tire contact patch and as such increases front grip and reduces unsersteer. This is due to the suspension design on the e82 which can curve to positive camber in a turn when the corner sinks and that is not good for the tire contact patch. This is why I and most others on the site feel a benefit from this relatively cheap mod that most people can do on their own in an hour.

Camber: if you are having unsersteer problems the first thing I would look at are my alignment options. The 135i does not have much camber up front stock. Alignment is a great way of changing the cars balance and behavior and is pretty cheap. You can remove alignment pins up front for about -.5 camber plus there is some general adjustment room. Beyond that you would need camber plates or could use the m3 front control arms for -.7 but that is not exactly good bang for your buck.

2 piece RSFB =179 +3 hour install
E92M3 FSB =280 + 1 hour instal
Alignment = ~$100
Total $560

Shocks $500 - $2600

[128Convertibleguy]

Originally Posted by Clovef

E92 or e93 front anti sway bar and brackets. ~$280 there is some debate if this adds or reduces under steer. If you read an old book it will tell you a stiffer front bar will keep a little less weight on your outside tire in a turn and decrease your grip. What people seem to experience is that it keeps the front from rolling over and creating positive camber. The FSB reducing that roll over in the suspension allows the suspension to maintain a larger tire contact patch and as such increases front grip and reduces unsersteer. This is due to the suspension design on the e82 which can curve to positive camber in a turn when the corner sinks and that is not good for the tire contact patch.

I don't think there's actually much debate about this. The books are not necessarily old, but they refer to race cars with camber compensating suspensions, not McPherson strut cars. Based on recently adding a 32mm Hotchkis front bar to my 128i i can report that, in this case, it reduced understeer. And that's with no rear bar at all. I don't think that would work on a race car, or even on one with double a-arms up front.

I'm not an engineer, or a suspension expert, but personally I'm coming to a conclusion that, on a 1 series, for cornering grip, camber trumps most things up front. Limiting roll seems particularly important if you run static camber less negative than -1 degree.

By the way, a stiffer front bar increases weight transfer to the outside tire from the inside. That's why, on some cars like Porsche 911s with competition suspension, you sometimes see them pull the inside front right off the track. By making just one tire do the work, you reduce grip. But, I think the camber effect is usually more important on a 1 series.