Nose Dive While Hard Braking!

OMG....how silly is it to think installing a spacer will increase spring tension. Of course it will not. What is really comical is that we now have Brian and harper offering two different reasons (both false) that neither can agree upon.

harper thinks he increased spring tension and Brian thinks he's altered the center of gravity enough to actually reduce nose dive during braking. This is turning into an epic thread! I love it! I'm definitely posting a link to this thread for my favorite peeps!

Oh, and just for the record...I've had a spacer lift installed in my own 4Runner for about 5 years now. And it definitely did not reduce nose dive upon heavy braking. But then again, the 5th gen 4Runner seems to suffer from excessive nose dive much more so than the 4th gen.
 
westwind77 said:
If you have seen Harper's 4R, and the amazing mods he has completed already, you KNOW that he can be trusted. I think once you get to know people on here you will know who to trust.....and more importantly, know who not to trust (cough cough Jed).
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No question that harper's done some nice mods to his 5th gen. But that doesn't automatically make him knowledgeable or trustworthy. He's made a few statements lately that were complete FAILS. One of my favorites was when he said that a spare tire loses more air than a tire in use. Sorry, but I'd rather deal in reality than blindly follow along with more of harper's gems.
 
Here ya go Jed, a technical description on how rake effects the nose dive;

To determine the percentage of front suspension braking anti-dive, it is first necessary to determine the tangent of the angle between a line drawn, in side view, through the front tire patch and the front suspension instant center, and the horizontal. Then, divide this tangent by the ratio of the center of gravity height to the wheelbase. Finally, multiply by 100. A value of 50% would mean that half of the weight transfer to the front wheels, during braking, is being transmitted through the front suspension linkage and half is being transmitted through the front suspension springs.

i.e. changes in one of those variables, lifting the front end in relation to the center of gravity. The variable in question is "center of gravity height to the wheelbase".

Harper, I assumed you used a top out, sorry. So you actually opened up the housings and recompressed the springs all without dismantling the XREAS hoses in your damn garage!!! You are the man sir... I remember reading your post but didn't fully comprehend the workload. Holy crap, nice..

Jed, I could see arguing that adding a top out spacer (being more specific) has arguable influence on brake diving, that's something that really depends on how high the spacer lifts in relation to the original height. But to argue that increasing the spring rate (or technically since the spring is more compressed it's initial start point is higher) by installing a spacer within the compressed housing is just plain stupid.
 
BrianLSU said:
Here ya go Jed, a technical description on how rake effects the nose dive;

To determine the percentage of front suspension braking anti-dive, it is first necessary to determine the tangent of the angle between a line drawn, in side view, through the front tire patch and the front suspension instant center, and the horizontal. Then, divide this tangent by the ratio of the center of gravity height to the wheelbase. Finally, multiply by 100. A value of 50% would mean that half of the weight transfer to the front wheels, during braking, is being transmitted through the front suspension linkage and half is being transmitted through the front suspension springs.
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Oh where to start? First, it's funny that you actually took the time to look that up. But again, you first made the supposition that raising the front suspension would transfer the center of gravity rearward, thus changing the brake bias and lessening the nose dive. Of course your paragraph above does nothing to support your theory, but it is still interesting nonetheless. The fact of the matter is that raising the front suspension, by say, an inch or so will not change the center of gravity rearward by even 1%. Have you ever heard of a fulcrum? Do you understand that your own theory requires a pivot point on the fulcrum between the unmodified rear suspension and the modified front suspension? Math is your friend...it is easily calculated if you know the wheelbase dimensions and the amount of lift.

Harper, I assumed you used a top out, sorry. So you actually opened up the housings and recompressed the springs all without dismantling the XREAS hoses in your damn garage!!! You are the man sir... I remember reading your post but didn't fully comprehend the workload. Holy crap, nice..
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You're easily impressed. It's not even challenging to install spacers without disconnecting XREAS. I did it in my garage by myself without anyone helping. No biggie...really.

Jed, I could see arguing that adding a top out spacer (being more specific) has arguable influence on brake diving, that's something that really depends on how high the spacer lifts in relation to the original height. But to argue that increasing the spring rate (or technically since the spring is more compressed it's initial start point is higher) by installing a spacer within the compressed housing is just plain stupid.
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Top out or pre-load doesn't matter. I think you're getting confused with progressive rate springs because your post doesn't make any sense. Again, I'll tell you that the spring rate DOES NOT change with the addition or deletion of a spacer (not even with a pre-load spacer). I'm not sure why that's so hard for you to understand.
 
Jed said:
Respect has to be earned. 'nuff said.

If you have something constructive to add, feel free.
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You don't earn respect... you give it freely.

Your BS has grown tiresome.

And I think asking you to be respectful to others is definitely constructive.
 
The spring rate increases when you add a spacer on top of the spring inside a Coilover and below the top plate is because of the Physics law of elasticity called Hooke's Law.

In my opinion.....Increased spring rate in the front helped cut down on brake dive on my Limited but made the ride a little firmer.

It was a real pain to use a spring compressor in the wheel well for sure.Won't do that again!

Goin' to Dinner now......lol:nicethread:
 
For what it's worth...

I feel like I could squat real low and lean way back and I still wouldn't be able to compete in this pissing match you boys have got going.

However…

I am probably only one of a few that own a 5th gen and have had it stock, with spacers, and full 3" suspension lift. In other words I DO have something to compare to and it DOES make a difference in the nose dive! The spacers helped some, but the lift has basically eliminated it completely. :moon:
 
This is fun! I'm a newbie here but y'all are starting to feel like family...even Larry.
Sorry, maybe I'm just biased but I don't have squat to add to your dive problem.

:D
 
skel said:
The stock P245/60R20 tires' recommended PSI is 32. Thanks for the clarification on XREAS, it does make sense the way you explained it. It's just very unusual that I felt it this weekend out of nowhere really--I felt my back coming off the seat when braking (and I'm just talking standard braking at a stop light, nothing crazy).
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Sorry to beat a dead horse. Does the door sticker itself show 32psi?

As far as your back coming off the seat, perhaps brake assist was involved. If you go from gas pedal to a fairly firm brake pedal quickly, the computer interprets this as a possible panic stop and increases brake pressure to slow or stop the vehicle more abruptly. Just a thought.
 
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