Real Fiero Tech

Are you sure it's not the brake booster flexing?

On my 88 I get 0.035" vertical deflection of the brake master cylinder with full pedal force. As much as I can generate. 150 lbs? 200 lbs?

This is with the stock firewall but obviously not the stock master or booster.

ericjon262 wrote: ↑Wed May 01, 2024 9:13 pm
apparently plates like that are a thing on third gen F bodies, and a bunch of guys are happy with the results.

https://www.thirdgen.org/forums/organiz ... brace.html

this is definitely worth keeping more in mind than I thought.

There are quite a few chassis that have similar issues. In many front engine cars, the far end of the brake MC can be braced to the shock or strut tower effectively, but that doesn't work in a Fiero.

Series8217 wrote: ↑Fri May 03, 2024 3:59 pm Are you sure it's not the brake booster flexing?

On my 88 I get 0.035" vertical deflection of the brake master cylinder with full pedal force. As much as I can generate. 150 lbs? 200 lbs?

This is with the stock firewall but obviously not the stock master or booster.

Maybe it is? Might be time for the Tesla electric booster conversion.

I need the plate as a way to mount both a clutch pedal stop and my DBW throttle pedal, so I'll finish it up anyway.

Series8217 wrote: ↑Fri May 03, 2024 3:59 pm Are you sure it's not the brake booster flexing?

On my 88 I get 0.035" vertical deflection of the brake master cylinder with full pedal force. As much as I can generate. 150 lbs? 200 lbs?

did you check horizontal deflection too? this is an interesting observation, I know in my car, it appears as though the master moves a significant amount as I bleed the brakes.

The Dark Side of Will wrote: ↑Fri May 03, 2024 4:37 pm

ericjon262 wrote: ↑Wed May 01, 2024 9:13 pm
apparently plates like that are a thing on third gen F bodies, and a bunch of guys are happy with the results.

https://www.thirdgen.org/forums/organiz ... brace.html

this is definitely worth keeping more in mind than I thought.

There are quite a few chassis that have similar issues. In many front engine cars, the far end of the brake MC can be braced to the shock or strut tower effectively, but that doesn't work in a Fiero.

I've seen several bracing methods, but without connecting the front wheelwells to the front frunk wall, I'm not sure there's anything there to really stop movement. I have a few ideas I would like to explore, but I am very intrigued by Series' posted information above, maybe I need to get an indicator out too...

The Dark Side of Will wrote: ↑Fri May 03, 2024 4:37 pm

Series8217 wrote: ↑Fri May 03, 2024 3:59 pm Are you sure it's not the brake booster flexing?

On my 88 I get 0.035" vertical deflection of the brake master cylinder with full pedal force. As much as I can generate. 150 lbs? 200 lbs?

This is with the stock firewall but obviously not the stock master or booster.

Maybe it is? Might be time for the Tesla electric booster conversion.

I need the plate as a way to mount both a clutch pedal stop and my DBW throttle pedal, so I'll finish it up anyway.

The "Tesla" booster is also in several other cars too, it's made by bosch, and accords got them too. That said, you posted in that thread so you already knew that...

https://www.realfierotech.com/viewtopic ... er#p161121

ericjon262 wrote: ↑Sat May 04, 2024 5:18 pm

Series8217 wrote: ↑Fri May 03, 2024 3:59 pm Are you sure it's not the brake booster flexing?

On my 88 I get 0.035" vertical deflection of the brake master cylinder with full pedal force. As much as I can generate. 150 lbs? 200 lbs?

did you check horizontal deflection too? this is an interesting observation, I know in my car, it appears as though the master moves a significant amount as I bleed the brakes.

0.016" horizontal deflection.

I have the stock Fiero pedal box with an E90 M3 brake booster and master. The adapter that consists of a steel tube and two flanges -- one with the Fiero 4-hole pattern and the other with the E90 2-hole pattern. The ABS module is connected via braided steel lines so the pipes aren't providing any additional bracing.

I had a second, so I measured the deflection of mine as well, I'm getting around .020 vertical, I probably could have pushed the pedal a bit harder, but it seemed to deflect to .020 and then stop flexing.

Wow! On the '88 there is a steel brace that goes from the base flange of the master cylinder to the combo valve, which is bolted through to the left frame rail. Do you have that? I eliminated it with my master cylinder swap... I might need to bring it back...