Seam welding rear shock towers |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Seam welding rear shock towers |
yeahmag |
Dec 4 2018, 12:31 AM
Post
#1
|
Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California |
I’m moving up from 225lb to 300lb springs in the rear to try and combat the rear rolling over and the large amount of front, inside wheel lift I’m getting. Is there a general rule of thumb for when I should seam weld the rear shock towers?
|
Chi-town |
Dec 4 2018, 07:50 AM
Post
#2
|
Senior Member Group: Members Posts: 850 Joined: 31-August 18 From: Disneyland Member No.: 22,446 Region Association: Southern California |
What valving are you running in the shocks?
What sway bars are you running? Street car, Auto-X, Track car? |
yeahmag |
Dec 4 2018, 09:31 AM
Post
#3
|
Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California |
Car is a narrow bodied autocross car.
Tires: Hoosier A7 Front: Raised spindles - 19mm built by Tangerine Racing for an EP 914-6 Rebel Racing (teflon) bushings Bilstein custom valves 22 mm torsion bars 21 mm sway bar Rear: Rebel Racing (teflon) bushings 225lb rear springs (going to 300lb) Koni Yellow No sway bar |
Chi-town |
Dec 4 2018, 10:45 AM
Post
#4
|
Senior Member Group: Members Posts: 850 Joined: 31-August 18 From: Disneyland Member No.: 22,446 Region Association: Southern California |
If you're getting that kind of weight transfer have you thought about stiffening the rear valve stack before going heavier spring rate?
I'm worried if you go heavier spring on that valving you're going to start to run in to tire bounce or funky snap oversteer. |
yeahmag |
Dec 4 2018, 10:50 AM
Post
#5
|
Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California |
I definitely need more spring. 300 may be too much, but I think it will be close to correct. I will likely end up with custom valved bilsteins in the rear, but shock valving won’t cure what I’m chasing.
|
Chi-town |
Dec 4 2018, 11:28 AM
Post
#6
|
Senior Member Group: Members Posts: 850 Joined: 31-August 18 From: Disneyland Member No.: 22,446 Region Association: Southern California |
I'm confused by your thoughts on this? Can you explain?
Not trying to question, just trying to understand your train of thought. (IMG:style_emoticons/default/beerchug.gif) I'm a track guy not an auto-x guy for the record. My thoughts: Stiffer compression valving slows the rearward weight transfer motion and reduces the front tire pick up. Heavier spring rate will try to eliminate any rearward weight transfer and apply extra load to the tire carcass possibly overloading contact patch (aka my snap oversteer comment earlier) Having thought about it a bit more, why no rear sway and have you thought about travel limiters for the rear shock like the GT used to use or shorter stroke shocks in the rear? |
yeahmag |
Dec 4 2018, 01:22 PM
Post
#7
|
Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California |
Please! Ask away! Debate!
So, we are having rear traction issues due to the car rolling around in the rear. The rear is rolling over enough to cause issues including the front wheel way off the ground, all the time, and (we think) rolling over the outside rear tire enough to break traction. Traditionally, autocross cars don't run a rear bar unless they have an LSD (which I do not). It's our opinion (my co driver is a hot shoe and worked for HRG as a tech and knows more about suspension theory than I ever will) that we need more spring to help plant the rear and stop the excessive tripoding. I personally think that I will actually distribute the weight overall better. If I do end up defeating some absolute traction at the back, I feel the rear end will be more predictable than what it is now. It's really sloppy back there now... We ran a ton of front bar to try and combat this (working the diagonals), but have reached the limit of what that can do. |
eeyore |
Dec 4 2018, 05:32 PM
Post
#8
|
Senior Member Group: Members Posts: 889 Joined: 8-January 04 From: meridian, id Member No.: 1,533 Region Association: None |
Do you have oversteer or understeer with the current setup?
Adjustable sway bar? |
brilliantrot |
Dec 5 2018, 02:33 AM
Post
#9
|
Member Group: Members Posts: 125 Joined: 27-April 07 From: Costa Mesa Ca. Member No.: 7,699 |
Do you have oversteer or understeer with the current setup? Adjustable sway bar? I'm the co-driver. The simple answer is both. To make the car drivable and faster we pretty much maxed out the adjustable 21mm front bar. The car has some push now but that was the only way to keep the rear end behind the car in sweepers and put down power as the car has roll oversteer also. Tightening up the front bar resulted in pulling front wheels close to 6" in the air as the rear is still rolling a lot as we got rid of most of the droop in the front by doing this. I would like to play with shocks to get things dialed in more but that's not on the table as an option right now. I think 300lb/in from 225 is too big of a jump and think the Konis will have a hard time controlling the rebound but who knows, I do like a loose car as long as it is predictably so which it was with a looser front bar, it just wasn't all that fast as it wouldn't put power down. The car is fast as I have gotten the top PAX time in it the last two events we have run, it just could be even faster. https://www.youtube.com/watch?v=3hRf0cg7RNU |
sixnotfour |
Dec 5 2018, 02:52 AM
Post
#10
|
914 Wizard Group: Members Posts: 10,436 Joined: 12-September 04 From: Life Elevated..planet UT. Member No.: 2,744 Region Association: Rocky Mountains |
22 mm torsion bars
21 mm sway bar wow like driving a Camaro |
ChrisFoley |
Dec 5 2018, 06:08 AM
Post
#11
|
I am Tangerine Racing Group: Members Posts: 7,934 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
If you add that much rear spring you may run into the other problem - rear wheel spin when trying to apply power coming out of a corner.
I would try 250 lb rate first. |
Andyrew |
Dec 5 2018, 10:13 AM
Post
#12
|
Spooling.... Please wait Group: Members Posts: 13,376 Joined: 20-January 03 From: Riverbank, Ca Member No.: 172 Region Association: Northern California |
[quote name='brilliantrot' date='Dec 5 2018, 12:33 AM' post='2671195']
[quote name='eeyore' post='2671049' date='Dec 4 2018, 03:32 PM'] https://www.youtube.com/watch?v=3hRf0cg7RNU [/quote] Damn I wish my car turned in like that!! Quick ratio rack or anything? |
yeahmag |
Dec 5 2018, 12:34 PM
Post
#13
|
Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California |
It does, but that really only helps on things like hairpin turns. It does noticeably speed up the steering when you are playing "catch and release" with the back end.
I think what you are seeing more than anything is just a well set up car ;-) |
PlaysWithCars |
Dec 7 2018, 12:00 AM
Post
#14
|
Senior Member Group: Members Posts: 524 Joined: 9-November 03 From: Southeast of Seattle Member No.: 1,323 Region Association: Pacific Northwest |
I'm running the same spring rates that you are and considering going stiffer. The jump to 300# does seem mighty big though. I was targeting something more in the 250#, 275# range.
|
eeyore |
Dec 12 2018, 09:39 AM
Post
#15
|
Senior Member Group: Members Posts: 889 Joined: 8-January 04 From: meridian, id Member No.: 1,533 Region Association: None |
This problem is similar to the issues JP and Britain had with the Sh!tbox.
As for the original question, there have been much back-and-forthing about benefits or necessity of welding & reinforcing shock towers. Try bigger springs for an AX or two. If they do what you want and stuff starts to tear, weld the towers. |
Lo-Fi Version | Time is now: 10th June 2024 - 03:22 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |