should i drop the rear

T77911S · 12-13-2018, 09:16 AM

I have always hated how hi (the entire car) the rear end is compared to the front. but some Q's
do you think I have enough tire/fender room to drop the rear.
how much will one spline drop it
this should also reduce some over steer

I had it on the track for the first time about a month ago. it did have a lot of turn in over steer. I got much better at controlling that (on the gas really quick) but not sure how much is still me and how much is the car. I was also all over the place with tire pressures. once hot, the pressures were in the mid to upper 40's.
but, as said, I don't know if over steer got better do to 1 me slowing down, 2 me learning the car 3 tire pressures. (brakes over heated so I worked more on my line)

I have some pics of the car in the mountains and the front spoiler is about an 2.5 inches off the ground.

I really like the ride, I also like that I don't have a lot of neg camber eating up $1000 tries, but, I would like it lower and perhaps a little stiffer so I was thinking
20/27 Tbars. I was not planning on tracking it much but would like to learn to drive the better.

should I just drop the rear and track it again to see how it handles with the rear down.

T77911S · 12-13-2018, 09:35 AM

ELZ's930 · 12-13-2018, 09:40 AM

Looks pretty darn good as is. You may have to go more negative to get any more out of it but that's just from looking at one picture.

Very Nice.

JacobS911 · JacobS911's Garage

^^sweet ride! I say drop it like its hot

T77911S · 12-13-2018, 09:47 AM

my brothers is lower in the rear and his looks soooo good from behind.

T77911S · 12-13-2018, 10:07 AM

gumba · 12-13-2018, 10:36 AM

You should have factory rear adjustable spring plates, which is what I would start with. If not, get some. Dropping the rear end also changes the front, so you should do a 4 wheel alignment. If it's not a track specific car, I would do 0 rear camber, 0 rear toe, and 1.5 front and just check the tire wear. Or get an inexpensive tire temp gauge. Also get adjustable front & rear sway bars so you can adjust it for different track conditions.

RarlyL8 · RarlyL8's Garage

Nice looking 930!
If just for looks I'd lower the rear, if for practicality I'd raise the front. From a balance/handling perspective the front/rear bias is off as the car sits, the front needs to be higher. I would imagine it plows pretty bad as is.

Tippy · 12-13-2018, 12:26 PM

Sportscar in front, 4X4 in back...

You know my answer.....

full quack · 12-13-2018, 03:09 PM

I probably should not even chime in on this topic....given my propensity for all things low.

Mark

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by T77911S

I have always hated how hi (the entire car) the rear end is compared to the front. but some Q's
do you think I have enough tire/fender room to drop the rear.
how much will one spline drop it
this should also reduce some over steer

I had it on the track for the first time about a month ago. it did have a lot of turn in over steer. I got much better at controlling that (on the gas really quick) but not sure how much is still me and how much is the car. I was also all over the place with tire pressures. once hot, the pressures were in the mid to upper 40's.
but, as said, I don't know if over steer got better do to 1 me slowing down, 2 me learning the car 3 tire pressures. (brakes over heated so I worked more on my line)

I have some pics of the car in the mountains and the front spoiler is about an 2.5 inches off the ground.

I really like the ride, I also like that I don't have a lot of neg camber eating up $1000 tries, but, I would like it lower and perhaps a little stiffer so I was thinking
20/27 Tbars. I was not planning on tracking it much but would like to learn to drive the better.

should I just drop the rear and track it again to see how it handles with the rear down.

Nice car! As i mentioned in the other thread 245/35 & 285/30 would be a better tire choice.

It does look like the rear can come down a bit, at worst a tad more neg camber in back which would reduce any oversteer.

Your tire pressures seem way to high, for street or track 34 front 35 rear hot is going to be closer to what you want, too much rear is another contributing factor to over steer.

t-bars would help, 22/28 or even 23/29 isn't overly large and both reduce oversteer 23/29 the most

gas is glue for the rear so you are on the right track to counter any oversteer tendency, ie get on the gas(as long as you are pointed in the right direction) as early as you can and unwind the wheel as quick as you can

if overheating brakes use better fluid, Castrol SRF is the best, but there are other good fluids, and use track oriented pads, Pagid 29 or PFC 08 are great track pads that also work on the street

Get your correct line down first, speed will come later, but sometimes the line thought in DE isn't the fastest line, you may want to experiment and get advice from faster drivers.

DE is the best place to learn how to drive better, followed by A/X, If you can go to a car control clinic on a skidpad, watered down is best by dry is good too.

heliolps2 · heliolps2's Garage

Hello Turbo friends

Great looking 930, I love the wheels of course, I went with 235-40-18 and 285-30-18 looks slimmer, The tire setup you have now looks a little bulky, I would drop the rear 1/4 to half inch. maybe raise the front by the same to balance, remember lower rear less oversteer , 36 psi front and rear works well, Are your wheels 18 inch ? what's the width of your wheels ?

Here's some pic's of my car

Helio

JFairman · 12-13-2018, 04:26 PM

From looking at your picture I think it would look better if the rear was lowered around 3/4" to one inch, or around 19mm to 24mm. Maybe a little more.
The front is easy. You turn an 11mm bolt if I remember correctly and you can do that while laying on your side and reaching in under there with a wrench while the car is on the ground. count how many turns you make so you can go back if you decide to.
You have to try it and see where you like it.

If the rear springs are still torsion bars they have a different amount of splines on each end of the bars. 44 splines on one of the ends comes to mind but I'm going on memory from when I did that many years ago.
Because of that to lower or raise the back of the car small amounts you would go one direction like 3 spines on one end and then on the other end of the torsion bar you would go the opposite direction 4 splines.
Doing that will raise or lower the back end of the car in small amounts and much less than just moving one spline on one end of the torsion bar.

After doing any adjustments you will have to roll the car forward and backward or even better drive it a little so the tire caster and camber settles into it's new place.
After you get the ride hight where you like it you will need a 4 wheel alighnment done by a shop that knows these cars.

If you remove the torsion bars smear the entire outer surface of them with general purpose grease if they are bare metal so they don't rust. If they are powder coated or painted you don't have to do that.
Grease the splines on each end good too because you really don't want the bars to rust into their sockets. They can be difficult to remove if they've been in place a long time.

Good luck with it. Your car looks very nice

Alan L · Alan L's Garage

If you are lucky you will get 1" out of the spring plates. In a day or two I can give you exact numbers with the splines - ie two inner vs 1 outer = x inches. I just don't have the info handy.
If you want that info, let me know and I will post it when I get a chance. 40 splines on one end, 44 on the other. Clever arrangement.
Car looks great. Porterfield ST pads worth a shot - Street/track. I just use the Track ones - too much wear on ST when just track use.
Regards
Alan

Alan L · Alan L's Garage

I don't think the heights are too far off. But at 40 psi rear it will feel squirmy. I run 33-35 hot rear on track.
I suggest try correcting that first. You could tweek the rear slightly if you have enough spring plate adjust. But best practise is one change at a time.
Porterfield S/T (street/track) pads may be useful.
Regards
Alan

T77911S · 12-14-2018, 02:58 AM

Quote:

Originally Posted by RarlyL8

Nice looking 930!
If just for looks I'd lower the rear, if for practicality I'd raise the front. From a balance/handling perspective the front/rear bias is off as the car sits, the front needs to be higher. I would imagine it plows pretty bad as is.

actually no. had it in the mountains and the turn in over steer worked VERY well. this was with higher tire pressures. went back to the mountains after my track day and lowering/changing pressures seem to reduce over steer although still no under. (also may not have pushed it as hard).

track had lots of over steer. could also be me. turn in's may have been to "quick" at first making it over steer more. there were quite a few turns you would think I was trying to "drift" it. I actually got quite comfortable with it doing this expect for the 100mph kink.

T77911S · 12-14-2018, 03:07 AM

I already use motul 600 but just saw they have a 660.
just got the PFC 08 pads the other day.
got a piece of duct hose and I am going to see if I can vent some air the rotors. I do have air ducts in the front spoiler. RUF spoiler.

I was shooting for about 34 front and 36-38 rear HOT at the track.
if I go again I am going to buy a pyrometer and I may even put nitrogen in the tires and try to stop this tire pressure guessing game.
where I pitted was right off the track so I can check pressures pretty fast before the tires cool.

it was an HPDE put on by BMW.

T77911S · 12-14-2018, 03:17 AM

heliops, car looks great.
that is what I am looking for.

thanks to the rest.
suppose to rain all weekend. gotta get the headlight back together on my BMW first then on to the 930. the shielding on every wire is cracked and coming off. had to remove each wire and heat shrink the entire wire.

yes, I would like any info on splines and how much it lowers it.
i will check the spring plates first.

Jeff NJ · 12-14-2018, 06:50 AM

If the spring plates are stock, they are probably already adjusted to the lowest setting. That's how mine were, and when I researched on here at that time, it seems that's how they typically come from the factory, so you can either drop it a bit too far with the splines and then adjust the spring plate up to get it exactly how you want, or center the spring plate adjuster so you can go up or down after moving the torsion bars a spline or two. Maybe you'll get lucky and find your spring plates were already moved, so you can just use that.

I never was able to find out how much an adjustment of one spline on the inside or on the outside splines moved the body up or down relative to the wheels. Would be nice to know.

JFairman · 07:21 AM

The spring plate bolts can be more difficult than they look. If adjusting them while on the car you'll need a really thin special open end wrench to fit between the longitudinal and the spring plate to get at the big bolt/nut and they are on there really tight. I think they are eccentric bolts that work kind of like a cam lobe while you turn them. I've never done that though so I don't know.

When I have adjusted rear ride in different 911's I never touched those bolts and did it all by repositioning the splines on the torsion bars. By doing that like I mentioned before you can make fine adjustments in rear ride hight that can not come loose and will never change.

The rear spring plates on the car I used to have were not set to the lowest setting at the factory. They were in the middle range. It's real easy to tell if they have ever been changed from the factory positions because the spring plates are yellow zinc plated at the factory and if they are ever readjusted there will be a tell tale mark left in the plating. Only way that could be hidden is if they have been removed and re yellow zinc plated before you got the car and that is possible but unlikely.