Front shock absorbers - advice

[AEnrico]

Hi to all and everyone!
I'm step by step fixing all the minor issues with my 325TI, but after taking it to a workshop for a complete fluids change, it has been discovered it has one front shock absorber leaking.
The car has got by the previous owner a lowered setup, and it has spacers overall and 18" staggered summer tires (225 &255).
Winter tires are squared on 17" rims.
So the question: changing just front shock absorbers, retaining spacers, 18" rims and so on, which shock absorbers should I get?
Goals are: fast driving qualities on B roads, durability, not too harsh when driving in town, some little advantage on track's performance over stock absorbers. Expecially, I wouldn't buy any great shock absorber that will require rebuiliding after 20K miles of mixed driving, that is definitely a no go for me.

As a side questions, there are many orginal BMW parts that are NOT listed as compatible with my car (a Compact), still I keep reading about people installing them. One item I fancy is the front strut tower reinforcements, namely BMW

51717036781. It is listed as not compatible with E46 Compact, still many people seem to install them on their Compact. Is it actually drop in compatible, or will it require some kind of reworking?

Last doubt on my side, I was ready to install new front tires, should I wait until new shock absorbers are installed?

THX!

[dworthy]

If you would call the new springs "lowering" then I would look at the right shock for that car. Sach/ZF is the OE provider to BMW for said shocks, and I would go with the "sports" for your application. If you don't find the "Compact" in the book, use the Coupe/Sedan ones, as they are the same.

I found a set off of ebay.de: Shock, bump stop, dust boot, and upper bearing for 225 euro delivered to my door.

As for the reinforcement piece, why not just try it as you already have them.

[AEnrico]

Thank you! Well, I don't know (not yet) whether it's just a lowering set of springs, or the shock absorbers are not original too. Was tempted about original M3 shock absorbers, but again they are listed as not compatible wuth my car (but are listed with a standard E46 Coupè). Price would be a little bit higher, but not as for any coilover set and it will be OEM quality. I expect them to be way stiffer than standard ones, but given how many people use their old M3s as daily driver, it should be still bearable, shouldn't it?

[bluptgm3]

The Strut Tower Reinforcement Plates p/n 51717036781 do fit and are highly recommend to strengthen the Strut Tower. These are to prevent deformation and cracking of the ST, especially when using Sport Springs and aggressively dampened shocks.
As for dampers I would get something listed for the ‘ti’ as you will want the dampening of the rear shocks to match the dampening characteristic of the front. All four should be replaced at same time. Sachs/ZF is/was the OE supplier, as stated, however, Bilstien and Koni offer great replacements. I believe Bilstein offers B4 (OE replacement), B6 (intermediate), and B8 (Sport, intended for use with lowering springs).

You will get ~ 30-40K miles out of the OE replacements.

I see that the E46 ‘ti’ uses the more refined multi-link rear suspension geometry/components unlike the E36 ‘ti’ which uses the E30 single Trailing Arm Suspension.
I do not know the E46M3 suspension interchangeability.

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[AEnrico]

Yes I know the Bilstein's lineup, but heard quite a few customers mourning their Bilstein's shocks went busted after 40k miles or less. This is why I stated durability as a requirement. Otherwise, living in Europe, I was thinking about KW or H&R sets, but it seems to me quite expensive (essentially speaking of coilovers, of course).
I read somewhere that M3 struts could be installed on any E46 using the whole M3's mounting plate and accessories

[dworthy]

I am not sure on the M3 shocks, as the valving would be different than what you have now.

The idea is to find a set of springs and shocks that work well together, and the E-46 rear ends kill aftermarket shocks like the E-36's do.

Find a tuning shop and have a chat with them to see what they would recommend for a set-up.

[AEnrico]

Well, I read around that M3 suspensions are compatible with E46 sedan/Coupè, just all the related hardware has to be changed. Mounting plates, springs, springs supporting plates have to be the M3 ones. Maybe (I'm not sure, didn't dig out) the upper mounts have to be flipped around (left - right) to have manageable camber values.
I've found a used set (front and rear, with all the related hardware) with around 50k miles on them for quite a cheap price.
Still I fear they will be too stiff/high, because an E46 M3 weight more than a sedan, let alone a Compact, so they could be just out of specs.
It's likely I will go for Bilstein B12, just I would like to buy the front ones only and save some money for the time being.
So now the real question is: Sportline o Pro-Kit?
Pro seems to lower the car a litlle less, and I would appreciate it, but are equally competent suspensions in cornering?

[dworthy]

I didn't know the upper strut bearings were specific to a side, for they both have the same P/N. Now you do have a left/right shock/strut, and the rears are both the same.

I can understand getting the lower control arms, for they will be different.