Predator

I finally installed my Strange 12-bolt with 4.11s and CM driveshaft and went for my first test drive yesterday. Aside from the 4.11s being awesome and perfect for my M6, I was even more impressed with how the car feels and handles now. First off, the car feels solid and heavier, and more planted in the rear. Also, this is the best bonus, the rear suspension doesn't feel as harsh, especially over bumps. I have SLP Bilstein shocks and springs, front and rear, and I was always disappointed how harsh the car rode in the back. It seems with the extra weight of the 12-bolt, the rear shocks are working much better, the way I always hoped they would. I also have Spohn's SB clamps and poly bushings and endlinks, so that has been a factor in handling feel too. This 12-bolt is by far the best mod I've done. Well worth the 3k I spent.

You don't hear much talk about how a 12-bolt rearend affects a car's feel and handling, so thought I'd mention my experience.

Anyone else have a similar experience after replacing the stock 10-bolt?

strokerblackhawk

iTrader: (4)

i noticed similar results when i swapped in my 12 bolt, my suspension is pretty close to what you have

Predator

Thanks for the feedback strokerblackhawk. At least I know I'm not crazy, at least relatively.

I'm psyched about getting my heads installed now, and UD pulley. After test driving my 12-bolt, I was craving more hp, and I didn't even push the car. I'm trying to break-in the rearend carefully. It just never ends.

z28bryan

iTrader: (7)

I can't disagree with you more on this. Of course everyone has their own definition of what "handling" is, so this isn't a means of shooting down your thread but just a different perspective.

First thing, the 12 bolt is just a rear end. It's got more weight than the 10 bolt. Weight can have an effect on handling. Adding weight I'm guessing could improve your handling feel depending on your shock specifications. Sometimes the way the car feels can improve, but cause you to be slower since you added weight.

Also, what kind of differential did you have before and after? That can effect handling. Did you use the same shocks and springs and what ones did you use?

I'll also say this too and people often take it personally, and if so then I apologize beforehand. Most people give take their car for a spin down the road and take fast turn on an onramp or something and consider that proven results if a car handles well. I think that's a poor way to test out a car's ability. The only way in my opinion to test handling is to take it on a road course or an autox and go through some sweepers and some slaloms where you are actually putting the car on the limit of traction and compare your times. Slaloms are a real good way to test how how the car feels. Most public areas are impossible to do that safely.

So no hard feelings, but I have to disagree completely with you. I'd say the 10 bolt is the best rear end to have in an fbody that you want to handle really well. Maybe if you're getting into 400-500+ hp, then you might want to sacrifice a little weight for durability.

I'm guessing this thread will go into multiple pages

Predator

z28bryan, my evaluation is completely amateurish seat-of-the-pants subjective comparison with how the car felt before the 12-bolt. Possibly if the car was on a test track it might prove to be handling worse, so I can't disagree with you, but then again it might indeed prove to be handling better.

All I know really is that the car feels planted to the ground, sort of like a train on tracks, and the complaints I had about my car's rear shocks on city streets have disappeared. The SLP Bilsteins, which I believe but I'm not sure are just Bilstein HDs, were extremely harsh with the stock rearend, but maybe that's ideal for the track, I don't really know. You definitely have to take my post for what it is. I'm no expert on handling, that's for sure.

You asked about the differential, shocks and springs. The shocks and springs are the same SLP Bilsteins I had with the ten-bolt, and the differential before was just the stock posi, and the 12-bolt is an Eaton posi.

Thanks for your post, I learned some stuff.

Predator

To condense what I've been trying to say, it seems that the performance of the rear SLP Bilstein shock/ SLP Eibach spring combination is much improved by the addition of the 12-bolt's extra weight. Does this make sense, and is it possible?

z28bryan

iTrader: (7)

I guess the way I see it is the rear end is just the rear end. The 12 bolt is the same as the 10 bolt only heavier, a lot stronger, and gives you different options for differentials and gearing. Maybe the shock and spring combo has a better feel with the heavier rear end for spirited street driving

Predator

Bryan, that's how it seems.

I know that the SLP Bilstein/ SLP Eibach rear setup is not considered to be very good on a car with a stock rearend, and my experience just street driving is the same. I don't know the technical terms for what exactly is the problem, but it seems with the extra weight that that spring/ shock combo feels much better.

I was hoping you suspension experts could explain how the extra weight affects rebound and damping so I could understand what's happening. It might even prove that what I'm experiencing is actually a worse handling experience even though I seem to prefer it, I don't know. Thanks.

RevGTO

iTrader: (12)

My guess is that the heavier rear end may tend to stay planted over bumps and such, whereas the stock rear, especially with shocks that have too much compression and too little rebound, tends to skip over them - which can be unnerving in the midst of high speed cornering. This would equate to better handling, which includes a lot more than better slalom times.

Predator

Interesting RevGTO, appreciate your feedback, and I'm glad to hear that what I'm perceiving to be better handling is actually better handling in the sense of what you described, which is the case. The rear of the car is more planted especially over a series of bumps instead of skipping, as you said.

I'd like to be able to conclude that SLP Bilsteins and SLP Eibach lowering springs are a good shock and spring combo with a heavier aftermarket rearend, but not so good with a stock rearend. Maybe that shock and spring combo should be marketed that way, just a thought, but I'm sure that actual track testing would really tell the story instead of my anecdotal/ seat-of-the-pants street driving experience. Thanks!

chupr0kabra

iTrader: (10)

It's interesting how different people react to similar mods.

When I had my 12-bolt installed, my handling went to hell. Everything you described (heavier, more "planted") was a negative to me. My car's handling went from firm and responsive to sluggish. That said, I was able to adjust my Konis to get it back to acceptable.

Not saying you're wrong. Just saying that "good handling" means different things to different people.


-Mike

z28bryan

iTrader: (7)

I really don't know but I would guess more unsprung weight/more mass on the rear would possibly make you want to increase compression damping slightly?

Like for example, a Miata can have really worn shocks and probably handle like crap but it would still be faster on a smaller course than a BMW 5 series with great handling feel. I guess it just depends on how you want to define good handling.

Predator

Mike, that's pretty much the crux of what I've been trying to find out. Even though my car, prior to the 12-bolt, felt way too harsh, suspension-wise, it handled curves pretty well, so I just wrote-off the harshness as a price I had to pay for a better handling car. Then after installing the 12-bolt, that harshness or stiffness (if I'm using the right terms) is much less severe, and the car still seems to be able to handle curves well, so translated, to me, I now have a better handling car, but maybe I actually don't. See my confusion?

I really don't know how a great handling car is supposed to feel, just what seems the most pleasing to me, mainly handling street imperfections without jarring my teeth, and hugging the road around curves. I'm no racer, just an F-Body lover who has been adding modifications over the past eight years.

And that's why I'm not offended by anyone who disagrees with my uneducated observations, because I could be completely wrong. I just have enough suspension information to make me dangerous, that's about it. Thanks.

Predator

Bryan, from what I've read here, the SLP Bilstein/ SLP Eibach combo is not considered to be a very good setup, but maybe the extra weight is what it needed to perform better. And that seems to be true according to my SOTP's meter.

Maybe it would be helpful to me if someone could try to describe what good handling is, and what it feels like, especially on the street as opposed to a track? Thanks.

Foxxtron

iTrader: (1)

AFA unsprung weight goes, you're correct. AFA more mass on the rear, again it goes back to what mass is sprung (rebound stroke) and what's unsprung (compression stroke). Just clarifying.

Right again, and that's due mostly to the Miata's low overall mass (which I may add that the Miata has some pretty low unsprung mass as well.) EDIT: While it is true that it helps to control the mass that's present, it's much more beneficial if there can be less mass to start with (provided that the overall chassis stiffness is still optimal).

EDIT 2: I should also stress that having the appropriate weighting over the wheels is essential as well. This could be another factor why some have perceived the additional unsprung weight to be an "improvement" in handling, however this shouldn't be the case here. Nevertheless, the stock 10-boltr axle has more than enough unsprung mass already, and adding more when not necessary does hurt handling/braking performance (regardless of SOTP).

I would like to stress here in this thread as I have in other threads that while SOTP is useful, it's highly subjective. A much better measurement of handling would be through some AX times, and it's best to compare the same exact car before the modification and after as well.

Sam Strano

iTrader: (41)

More unsprung weight is not helpful. It's the equivilent of running in combat boots vs. running shoes. If the compression damping is off and it's too high for a stock rear a heavier rear axle can "help" simply because it's a better match for the compression damping, not because in general more unsprung weight is better.

MeentSS02

iTrader: (11)

While I don't think the handling of my car improved by going to a 12-bolt, it didn't hurt it as much as I thought it would. Meh...who knows. To me, the extra reliability of a physically larger gear set and differential, positive axle retention, and 4.11 gear ratio were worth it to me.

Predator

Thankyou kindly Sam, exactly what I was looking for.

I didn't mean that the extra weight improves handling, generally speaking, just that with SLP Bilsteins/ SLP Eibachs on my car, specifically, it helped. With your explanation, I can pretty safely say that the compression damping was too high with the weight of my stock rearend. I realize that I would have a better handling car with the stock rearend and springs and shocks that were properly setup.

I was looking for the technical terms to explain what was happening with my car, and you came through. I appreciate it. Thanks again!

Predator

Same here, I'd never want to go back to the stock rearend, despite the extra weight.