Cheap BJ1 chassis bracing upgrade

[TheMAN]

I made a discovery last night while flipping through the shop manual... it says that the rear crossmember support bracket was added in 2001. In otherwords, BJ1s don't have this!

I just can't imagine not having this cheap, but crucial part (it came with my 2001, of course). It sits between the bottom of the floor and the centre portion of the rear crossmember. Its purpose is to reduce the rear crossmember flex in order to stabilise the rear suspension geometry under load. As with all chassis bracing, that is it's main purpose; to maintain suspension geometry in order to provide stable, predictable handling.

So for many of you BJ1 owners who weren't fortunate enough to have the Autoexe chassis braces, this is the next best thing. Here in the US, it's a mere $20 part, so it shouldn't cost much in oz either, and you might even be able to find it from the wreckers for next to nothing!

Here is what the part looks like:

There are also 5 bolts that goes with it

It goes here (the red Autoexe piece you see replaces it; I didn't bother taking pics of my stock one on the car):


Installation is very easy.
First, remove the 4 bolts for the rear crossmember, and lower it with everything still attached. Do NOT touch the lateral link bolts if you don't want to get an alignment done again.
Afterwards, bolt the support bracket into the bottom of the floor with 3 bolts. The opening side where you can insert the bolts are towards the fuel tank.
Finally, just raise the crossmember back up with a jack or with help of another person very slowly/carefully, then bolt the crossmember back on the car and bolt the bottom side of the support bracket through the openings at the bottom of the crossmember. There are 2 alignment/centring pins on each side where the crossmember bolts to the car, so its position will practically be the same as before.


Any of you who want to just buy this cheap part new, the part number is B30D-28-8C0. You will need 5 bolts, in which the part number is 9078-60-820.

Interestingly, Mazda chose to use a stronger support bracket for the Protege5 in the US. I don't have pics of it, but it is a US only part. Part number is BN5V-28-8C0A. It is a little more expensive.

[rodhog]

It's not uncommon for any car maker to do it let alone mazda.

They build a sliglhty different model and add ons get added. The did it in the 80's and with will do it tomorrow.

It's a bit like We Say in Australia- You never buy a series 1 commodore or Falcon you will know all the problem by series 2 or 3 o- or even 4 and 5

But mazda have add alot of braces over the years. sometimes what I find funny they add things but the basic weight never goes up ?

[Rhys]

wow this is an excellent idea. Thanks for this! I guess i'll go back to the wreckers at Wacol next weekend and see if i can get it off the sp20 that was there...

[TheMAN]

if you're swapping the front sway bar, you might as well get the entire front crossmember also from the BJ2 since you have to remove it anyway... it has a factory tie brace which can't be put on the BJ1 (mounting holes not there)... add a Cusco or Autoexe lower arm bar along with that, and the front end tightens up even more.... night and day handling difference!

[maztech]

Originally Posted by Rhys

wow this is an excellent idea. Thanks for this! I guess i'll go back to the wreckers at Wacol next weekend and see if i can get it off the sp20 that was there...

Was there 3 weeks ago, no sp there then

[Rhys]

Originally Posted by maztech

Was there 3 weeks ago, no sp there then

darn...

Also, had a look at my 2000 Protege and the cross member support was there.

[TheMAN]

maybe yours was a late build that had it added on? or the manual was wrong?

[Rhys]

I'm pretty sure mine was a later built one.. October or December or something like that if i remember correctly. Perhaps it's only for the 1.6's or something like that. Who knows??

[TheMAN]

yeah if it was built that late, it'll probably have it... it was a running production change
look on the door jamb sticker, it should say when it was built

if yours was built that late, chances are, your front crossmember will have the mounting holes for the factory tie brace too... or you can fit the GT spec 4 point ladder bar to it if you want

[maztech]

Edit the first post you do not need to touch the sway bar to fit the brace , drop the complete unit down and let it all hang

[rodhog]

I'm almost positive the original 100 or less original BLUE only Protege Sedan 2.0L's didn't get all the add ons the latter Sp20 model did get.

[TheMAN]

you're right... when I wrote that, I didn't remember if I took off the sway bar brackets or not when I dropped the crossmember to put that autoexe bracket in

[Rhys]

Just popped outside and checked- made in november 00.

The ladder bar might be a bit of overkill really...

[xeon8]

Mines a 1.6L, from June 2000, and I also have the cross member support

[Rhys]

maybe us aussies were lucky then?

[maztech]

Iam fairly sure all aus pec BJs had it fitted , another difference between US and AUS spec cars.

[TheMAN]

Originally Posted by Rhys

Just popped outside and checked- made in november 00.

The ladder bar might be a bit of overkill really...

it's not overkill if you plan on taking the car for spirited drives and some racing

the front crossmember is double U shaped... there's a U bend that goes around the the engine, then another U bend that goes over the exhaust/shifter

because it is a U bend that goes around the engine, and the suspension control arms attached on each end, the crossmember can flex inwards under hard cornering.. mazda added the ladder bar from the factory to reduce this flexing, which stabilises the suspension geometry and improves steering responsiveness... but this ladder bar isn't at the very end of the crossmember but only around the centre, so it doesn't do everything... that's why there's the cusco and autoexe lower arm bars...

since yours was built in november, it's very good news for you... you can simply get the OEM ladder bar and the bolts from any BJ2 and bolt it in!

[TheMAN]

Originally Posted by maztech

Iam fairly sure all aus pec BJs had it fitted , another difference between US and AUS spec cars.

perhaps...
not all countries got this fitted in the BJ1s of course... Japan didn't have them except in the Sport20 model, and Europe didn't either according to the European shop manual.... other countries didn't either

[rodhog]

I'd say it's an add on. I'd check earely 1998-2000 models.

I remember when they decided to do a few special 1.8L hatch's for dealers at Kingsgrove. I think it was before they were going to import the Sp20. I know it was before the protege 2.0L's. One thing that mazda is known for is doing many minor modifications for the Australian market not just just for compliance but for addoption to our conditions.

My Favourtie has been how some models will Get Euro spec lights - trim etc - but carry US suspension type specs and engines.

[TheMAN]

because they think everyone drives like mad max? lol