Rear dampers (shocks): Mazda5 (2nd gen) vs. Mazdaspeed3

[IamFODI]

Everywhere I look, most damper manufacturers insist that the rears are unique to the Mz5. What I want to know is exactly *how* the rear dampers differ, and why I can't just bolt up rear dampers meant for a Mazda3, Mazdaspeed 3, Focus, etc.

Anyone know what the differences are, beyond valving?

I've barely started digging into this myself, and it doesn't seem easy because all the relevant info isn't easily available on all dampers. But from what little I've found, it seems like the differences are minor. I found two dampers with info available on them: The KYB 343412 for the Mz5, and the TRW BBN528910C for the MS3. It looks like the TRW one for the MS3 has 1mm more stroke and 10mm more length. This was a bit of a surprise; I had assumed the Mz5 one would be longer.

Anyone have any knowledge or leads? Apologies if I missed this in another thread.

 

[IamFODI]

The plot thickens. Bilstein 19-197302 for the Mazda5: 21-22 mm more stroke than either option, and 4-14 mm longer length.

Source: Bilstein B4 OE Replacement Shocks 19-197302

Starting to suspect these rear dampers are interchangeable after all, valving notwithstanding.

...Not that valving is trivial.

 

[pkthomas]

The rear suspension is from the CX-7. I think this was due to added weight capacity. The valving and length of those is probably a compromise for use on multiple cars.

 

[IamFODI]

The rear suspension is from the CX-7. I think this was due to added weight capacity. The valving and length of those is probably a compromise for use on multiple cars.

Didn’t the CX-7 come out after the Mz5?

Springs and dampers don’t seem to cross-reference between the two. Maybe I’m missing something.

Agree that the weight was probably a major factor, though. Had to be, right? The 5 is made to haul around a bunch more stuff than the 3…

I just wish there were a credible option for (much) firmer damping on this platform. I’m on Koni Special Actives and they are not quite cutting it for my tastes. This investigation began as an attempt to justify using MS3-spec Bilstein B6s or something; I had assumed the main difference was length, and that I might be able to tolerate a shorter damper. But at this point I’m wondering if length isn’t a significant factor and valving is the main difference.

Anyone know of a 4-way adjustable damper for the Mz3/MS3?

 

[Silentnoise713]

Everywhere I look, most damper manufacturers insist that the rears are unique to the Mz5. What I want to know is exactly *how* the rear dampers differ, and why I can't just bolt up rear dampers meant for a Mazda3, Mazdaspeed 3, Focus, etc.

Anyone know what the differences are, beyond valving?

https://www.kyb.com/catalog/

Look up these car for same/similar year for apples to apples comparison. The difference is from the lower mount bushing size (width). The Mazda trailing arm has a wider box, so Mazda shocks have wider busing to account for the gap. Mz3/MS3 are direct fit (not recommend); Focus/V50 -need to add shims or source wider bushings to fit. A lot of shocks and struts can physically fit (maybe with slight differences in thru bolt sizing, bushing sizing), but valving is most important and must match spring rate and travel. Having extra piston length/travel is meaningless b/c the usable travel rate depends on what the spring allows after factoring in sprung weight. What matters is the Compressed and Uncompressed length, this ratio is directly tied to avail spring travel (+/- some margin).

KYB Gas-a-Just are a great option in the rear (the best IMO). It is the only monotube design avail for the rear (exclude the rear Bilstein B6 for V50). It would be nice if they would offer Gas-a-Just for the front!

I'm on B4s all around (twin tube design). I like them but have one huge grip, which is front struts do NOT have fitment ring/collar to fit square into the knuckle - they just add a dab of pinch weld -it's stupid, as if it is an afterthought.

 

[Silentnoise713]

I just wish there were a credible option for (much) firmer damping on this platform. I’m on Koni Special Actives and they are not quite cutting it for my tastes. This investigation began as an attempt to justify using MS3-spec Bilstein B6s or something; I had assumed the main difference was length, and that I might be able to tolerate a shorter damper. But at this point I’m wondering if length isn’t a significant factor and valving is the main difference.

What exactly are you trying to accomplish? I'm sure you are aware all things are a balance (or sacrifice).

How to best coilover or perhaps not for a Mazda5?

Mazda5 YellowSpeed Coilovers The recent suspension discussion brought some interesting points and since we have a few members with good first hand experience, figure now is prime to bring this up. Ive had this in mind and taking notes/measurements and put them aside for awhile and have been...

mazdas247.com

This topic brough back memories. The concept is the same, regardless if you are discussing separate spring+strut/shock combo or coilover kit (same thing other than adjustable perch and camber <-corner weighting and alignment are huge factors). I forgot I still have these in the basement. Interested in trying them out?

Autocross to Win (DGs Autocross Secrets) - Shocks

Autocross to Win, a technical discussion of preparing winning autocross cars.

farnorthracing.com

If you care to learn more, this is one of the THE BEST learning articles I've come across.

 

[IamFODI]

What exactly are you trying to accomplish? I'm sure you are aware all things are a balance (or sacrifice).

Absolutely.

Long story short, my family seems to share my wish that the Mazda5 had better body motion control, even at some expense to compliance. It's not urgent or anything but it'd be nice.

The thing is, our Mazda5 is on Koni Special Actives in an otherwise 100% stock (refreshed) suspension, and I'm not aware of any other Mazda5-specific damper options that seem worth the expense and effort to try. The only real sporty damper option is the Koni Sport ("yellow"), which I'm sure is firmer but not by much.

I know coilovers are an option, and thanks for your offer. I just haven't seen a coilover kit for this vehicle with anywhere near the level of engineering I like to see in a suspension product. I also want to keep stock ride height.

Autocross to Win (DGs Autocross Secrets) - Shocks

Autocross to Win, a technical discussion of preparing winning autocross cars.

farnorthracing.com

If you care to learn more, this is one of the THE BEST learning articles I've come across.

Love that site. This page was formative for me: Autocross to Win (DGs Autocross Secrets) - Buying Shocks

Especially this:

Remember this list:

• Bilstein
• Penske
• Koni
• Ohlins
• Sachs
• Dynamic Suspension

Not on this list? Almost certainly crap.

There are some arguables missing (KW, Nitron, JRZ, Moton, etc.) but, as far as most people will be concerned, this is pretty much dead-on.