350 knockback issues

[D K]

Hello

I know ther are a lot of cars with serious knockback problems.

Has anyone found a good solution to fix the problem?

David

[Matt93SE]

pump the brake pedal a couple times before stopping.

My G35 w/ StopTechs has had an annoying knockback issue since the day I bought it. poor design on the wheel bearings I guess.

[gills]

Hello

I know ther are a lot of cars with serious knockback problems.

Has anyone found a good solution to fix the problem?

David

I had this issue on my 04 Subaru STi with the older 5x100 hubs/bearings. It sucks. I would just tap the pedal a couple times on the straights before braking zones like Matt93SE said.

You can also try this solution. Don't have firsthand experience with it though:
http://www.apracing.com/Info.aspx?In...10&ProductID=7

[icantdrift]

A residual pressure valve will also help some, but if your bearings/rotors are sloppy you will still have it happen.

[Def]

G35/350Zs just do that - the bearing is underdesigned for the loads. Nothing will really fix it except a more robust bearing/spindle.

[theultimatehero]

I had no idea what this meant, nor that it had a specific name. For anyone that needs an explenation (like I did) StopTech has an article on it. I have found other usefull articles on their site too, like this one on Warped Brake Discs.

[Sleepy_Steve]

Right knee injuries are great practice for left foot braking.

[eye-5]

I've seen some cool in car footage with pros that always tap the brake with their left foot before any major braking zone.

Sent from my SGH-M919 using Tapatalk

[Matt93SE]

There's a damn good reason for that..

[240sxTTC]

I do it before every corner except for corners that are immediately after the previous. It's a great safety habit to get into. It firms up the pedal from knockback plus will also warn you early if there is a major issue.
Certain cars are more susceptible than others but the severity and occurrence is also track dependent. Tracks with taller curbs and tracks where the fast line is using those curbs will increase both occurrence and severity.
My lap around Mid-OH. The light above the shifter is connected to the brake switch - https://vimeo.com/108166468

[icantdrift]

I've started doing it as well. Even without major knock back issues it's nice to know the pedal is firm before trying to run deep into the turn. I've had oh **** moments in 10a at Road Atlanta when I tried to brake late and had to catch a pump midway through to get full pressure; that little momentary pump had me throwing the car through the corner to not end up in the gravel.

[D K]

Thanks guys

Yes, I had to do the left foot tap, otherwisw I wouldnt be alive...

I was just surprised that everyone seems to just accept this flaw?...

Seems the brakes were designd with WAY too much rear bias and the hubs are too thin, so they flex.
Everybody whos ever tracked a 350 just says: yea, mine dos that too.
I have alarm bells going off in my head and Im thinking how did a car company get away with designing such a poor system?

Really a bummer as I looked forward to possibly getting one, but now the only option is a 370 at much higher price point.

[gills]

Thanks guys

Yes, I had to do the left foot tap, otherwisw I wouldnt be alive...

I was just surprised that everyone seems to just accept this flaw?...

Seems the brakes were designd with WAY too much rear bias and the hubs are too thin, so they flex.
Everybody whos ever tracked a 350 just says: yea, mine dos that too.
I have alarm bells going off in my head and Im thinking how did a car company get away with designing such a poor system?

Teally a bummer as I looked forward to possibly getting one, but now the only option is a 370 at much higher price point.

This is what happened when car companies threw a large fixed multi-piston caliper brake setup on a car that was never really intended for them. Regular sliding calipers mask the flex in the assemblies for the most part.

Is there a way to upgrade on that chassis? On my STI I put on the later model 5x114.3 hubs and bearings and that fixed the issue almost entirely.

[Matt93SE]

Thanks guys

Yes, I had to do the left foot tap, otherwisw I wouldnt be alive...

I was just surprised that everyone seems to just accept this flaw?...

Seems the brakes were designd with WAY too much rear bias and the hubs are too thin, so they flex.
Everybody whos ever tracked a 350 just says: yea, mine dos that too.
I have alarm bells going off in my head and Im thinking how did a car company get away with designing such a poor system?

Teally a bummer as I looked forward to possibly getting one, but now the only option is a 370 at much higher price point.

That's because the 350Z, G35, and FX35/45 are all designed *primarily* as street vehicles. I have 160,000 miles on my G35 and the factory wheel bearings are still rolling just fine, even with the abuse I give them on the street. It's not a track car.

Track use with DOT-Rs or slicks regularly puts 2-3-4-5-10x the lateral loads on the wheel bearings as they see on the street. (how often do you take a turn at 1G on the street as compared to the track?).

What percentage of Zs, Gs, and FXs that all use these hub assemblies ever see track use? it's WAAAAAY under 1% of the total sales number. Thus, we are expecting them to do more than they were designed to do in everyday life. This is not a design flaw, this is 'engineering for a purpose'. Wheel bearings are a common wear item on race cars of all makes and are replaced fairly regularly.

Is there a way to upgrade on that chassis? On my STI I put on the later model 5x114.3 hubs and bearings and that fixed the issue almost entirely.

I don't *think* so. The factory assembly is a pressed-together blob of bearing and hub that bolts onto the front steering knuckle assembly-- doesn't have an axle stub in it like the S13/S14 chassis.. It's not a place where I would want to try to press it apart and put a larger bearing in there. Maybe it's possible to use 370Z hubs instead... Are they any beefier than 350Z hubs??

[Def]

Thanks guys

Yes, I had to do the left foot tap, otherwisw I wouldnt be alive...

I was just surprised that everyone seems to just accept this flaw?...

Seems the brakes were designd with WAY too much rear bias and the hubs are too thin, so they flex.
Everybody whos ever tracked a 350 just says: yea, mine dos that too.
I have alarm bells going off in my head and Im thinking how did a car company get away with designing such a poor system?

Really a bummer as I looked forward to possibly getting one, but now the only option is a 370 at much higher price point.

Welcome to the world of tracking a production car. Some are more suited to it than others, but in general, they all have some sort of Achilles heel.

A 370Z is even less track worthy for a more advanced driver IMO. Horrible fuel starvation issues, ABS is programmed poorly for hard driving on sticky tires (gets into ice mode randomly).

It's faster, but I wouldn't say better.


Slightly off topic, but I feel like the engineering conservatism from the 90's generally resulted in more robust vehicles that are typically happier on track than later model vehicles that are engineered much more closer to their "design target" - which is not the racetrack, but more like "spirited street driving on rough roads."

I don't *think* so. The factory assembly is a pressed-together blob of bearing and hub that bolts onto the front steering knuckle assembly-- doesn't have an axle stub in it like the S13/S14 chassis.. It's not a place where I would want to try to press it apart and put a larger bearing in there. Maybe it's possible to use 370Z hubs instead... Are they any beefier than 350Z hubs??

370Z hubs are supposedly improved, but I don't know if they work with 350Z bits. I didn't notice any major pad knockback on my buddy's 370Z when I drove it.

My S13 gets a tiny bit, but it's manageable. I run S14 bearings on GKTech aluminum uprights - which are approximately as stiff as stock steel uprights.