Welcome to the North American Subaru Impreza Owners Club Sunday April 20, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC General > Motorsports

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 02-09-2010, 01:52 PM   #1
Back Road Runner
Scooby Guru
 
Member#: 60082
Join Date: Apr 2004
Chapter/Region: MWSOC
Location: Minnesota
Vehicle:
2004 Forester STI
Silver

Default GC Chassis weight reduction - What are the big offenders?

Simple question hopefully. I'm looking at reducing some weight off my Forester (GC chassis base) for next auto-x/rally-x season. I want to drop a bit of weight off the front but weight off anywhere is good. The car will remain functional for daily use though, so it won't be a completely stripped, caged thing. I am mainly looking for key weight reduction options that are well known and easy/affordable to do.

Basics that I already know: battery, plop in a light weight, compact one, could relocate to the rear for better balance.

Light weight front end bumper beam: apparently the stock one is hefty, and there are some tough, very light ones available.

Common things like removing the spare tire and jack are more common sense.

The older chassis type doesn't have a front subframe stock, so there's nothing to do there.

I am already running a CF hood, although, I know of no other CF parts available for Foresters. There may be the option of attempting to fabricate my own CF parts if I were ambitious enough to make molds of the stock parts (all steel). CF and epoxy really isn't terribly cheap though and fiberglass and resin would be far less of a weight savings, or none if not done well, and comparatively weak and flimsy. There are no light aluminum versions available that I'm aware of, although newer models are largely aluminum.

I'm curious what other suggestions there are for dropping weight off the car, some things known in the race world but probably not looked at by the average joe. This may include removing parts completely or replacing parts with a lighter counterparts.
* Registered users of the site do not see these ads.
Back Road Runner is offline   Reply With Quote
Old 02-09-2010, 03:29 PM   #2
RB5 Clone
Scooby Specialist
 
Member#: 30909
Join Date: Dec 2002
Chapter/Region: NESIC
Location: lastditchracing.net & 03 STI
Vehicle:
RA East Open Class
Champs 07-08-09

Default

many of the changes you've suggested will bump you into different classes--jdm bumper beams DO remove a lotta weight way out at the ends where it's good, but that mod moves you up a class.

it's all good, long as you don't mind running against prepped rally cars, etc

lightening a car in a meaningful way while still retaining DD functionality is an expensive process--lots of $$4 for relatively little return. ripping out the back seats and interior panels is way cheaper and actually saves enough weight to be felt.

how much weight can YOU lose? seriously, taking 100 lbs out of the car (or off your waistline) is roughly equivalent to adding 10 hp to the motor.

Last edited by RB5 Clone; 02-09-2010 at 03:51 PM.
RB5 Clone is offline   Reply With Quote
Old 02-09-2010, 03:30 PM   #3
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

Well, the glass is heavy....and the Forester has ALOT of it......Pretty much ruins the daily driver aspect of things though.

The body spacers are solid steel, no? Probaly another 6-8lbs there, and a lower car once removed.....

Jay
Storm is online now   Reply With Quote
Old 02-09-2010, 05:58 PM   #4
Back Road Runner
Scooby Guru
 
Member#: 60082
Join Date: Apr 2004
Chapter/Region: MWSOC
Location: Minnesota
Vehicle:
2004 Forester STI
Silver

Default

I'm already in XP in auto-x and M4 in rally-x due to the CF hood and 4 point rear strut tower. I'm actually competitive in rally-x in M4 but only mid pack in the massive Street Tire spectrum in auto-x. The biggest problem seems to be weight and the overall power to weight ratio. I'm not really looking for wins. My goals are much more basic, just make the car more competent and faster. I would rather be limited by me then by the car. A sick engine will be part of the equation most likely the following season. I kind of want to toy with something towards a race spec NA for fun or supercharge it if I end up not getting what I want from it. Weight reduction is cheaper and something I can readily do for the next season.

I am unsure if I'm willing to remove the built in lift blocks. It's just that the car is set high because of rally-x, lower then stock and on sedan spec struts but rests a little higher from what a stock Impreza would be. The car won't lower from it. It'll just change the suspension geometry. The only way it would lower is if I cut and fabbed the top mounts higher. That's really the only way I could lower the CG while maintaining bump travel. Removing the body lift would also raise the CG of the car if I'm not mistaken. It'll lift up the engine and tranny higher into the car chassis. The engine mounts to the crossmember that the blocks connect to, dropping the engine, tranny, steering, and suspension points to lift the Forester body without messing things up. I remove them and the engine goes higher up, better clearance, worse CG.

Haha, the human weight element. I knew that'd be brought up. 45lbs. That's the savings I can achieve on the human side.

Yep, I'll have to carefully weigh the daily driver aspect and see what I am willing to let go.
Back Road Runner is offline   Reply With Quote
Old 02-09-2010, 10:52 PM   #5
RB5 Clone
Scooby Specialist
 
Member#: 30909
Join Date: Dec 2002
Chapter/Region: NESIC
Location: lastditchracing.net & 03 STI
Vehicle:
RA East Open Class
Champs 07-08-09

Default fix driver B 4 u fix car

Quote:
Originally Posted by Back Road Runner View Post
I would rather be limited by me then by the car.
Nice thought, but backwards. Improving your own skills will pay off way way more than tinkering with a few weight reduction mods to your DD.

I teach at Team O'Neil rally school, and I can't tell you how many STI and Evo pilotes have been utterly amazed at how fast the instructors can go in the skool's well-used 2.2 GC Imprezas. These cars are not highly built machines, they are running very basic suspension and tires.

On dirt, your Fozzie is just not the handicap you make it out to be. So yeh maybe it's a little top-heavy, learn to turn that extra weight transfer to your advantage.

The car is not the problem -- spend your time and $ improving the driver software.
RB5 Clone is offline   Reply With Quote
Old 02-09-2010, 11:23 PM   #6
Back Road Runner
Scooby Guru
 
Member#: 60082
Join Date: Apr 2004
Chapter/Region: MWSOC
Location: Minnesota
Vehicle:
2004 Forester STI
Silver

Default

Don't get me wrong. I wholely believe in improving the driver. There's zero point making a car faster unless you can make the car in its current state go 10/10ths. Otherwise, you're just wasting your time. A poor driver will make a fast car go very, very slow. However, at this time, I'm content with my own ability to drive the car, at least enough so where I don't see myself particularly limiting the car. I can always hone my skills more, but that argument can be beaten to death all day long. When I see myself drive the car slow, I blame myself. The second to last rally-x of last season was like that. I just drove slow that day and kicked myself afterward for being so lax.

I'm addressing blatant limitations with the car. Weight is a big one in my eyes. Power is another, although that is limited more to asphalt then dirt. I'm becoming increasingly aware of the mass of the car as a limitation. Long ago it was simple grip, then suspension. I've done bits with power and chassis stiffness along the way and improved precision with upgraded bushings, although I have plans to step to solid connections soon. Weight is something I see as the next major step that I really need to address.
Back Road Runner is offline   Reply With Quote
Old 02-10-2010, 08:48 AM   #7
neilschelly
Scooby Specialist
 
Member#: 94902
Join Date: Aug 2005
Chapter/Region: NESIC
Location: Merrimack, NH
Vehicle:
1988 911 Carrera 3.2
Silver

Default

I'm assuming you've already done the lightweight wheels and exhaust as those are big ones that are much more common. You can do aluminum suspension arms. There's a weight hidden under the front jacking plate by the oil pan worth about 5lbs. Hollow sway bars, if you can find/fit them. The AC is worth about 30lbs total. Aluminum radiator may save some weight up front. Lightweight race seats.
-N
neilschelly is offline   Reply With Quote
Old 02-10-2010, 11:06 AM   #8
RB5 Clone
Scooby Specialist
 
Member#: 30909
Join Date: Dec 2002
Chapter/Region: NESIC
Location: lastditchracing.net & 03 STI
Vehicle:
RA East Open Class
Champs 07-08-09

Default

on the big-T-shaped rear suspension subframe/diff carrier, there are 2 "harmonic balancer" weights on the outer ends of the T that will shave off about 3 lbs each...they unbolt easily.

jdm bumper beams are huge weight savers, probly 25-20 lbs @ each end

lose the rear hatch wiper motor/linkage

ditch roof racks n rails (rails big project, headliner needs to come down)

these are more or less free, compared to ally susp bits etc
RB5 Clone is offline   Reply With Quote
Old 02-10-2010, 11:08 AM   #9
neilschelly
Scooby Specialist
 
Member#: 94902
Join Date: Aug 2005
Chapter/Region: NESIC
Location: Merrimack, NH
Vehicle:
1988 911 Carrera 3.2
Silver

Default

I didn't have to remove my roofliner to remove the roof rack and rails. I don't remember the details, but I know I didn't have to do that.

You could get a lightweight flywheel too - that's worth about 15lbs.
-N
neilschelly is offline   Reply With Quote
Old 02-11-2010, 12:02 AM   #10
speedyHAM
Scooby Specialist
 
Member#: 48377
Join Date: Nov 2003
Chapter/Region: MWSOC
Location: "They eat fish soaked in lye"
Vehicle:
1996 Gutted, built
XP class Impreza L

Default

Get one of these -

http://www.braillebattery.com/index.php/batteries/ml9c/

There's 25 lbs off the car. Just a little spendy though.
speedyHAM is offline   Reply With Quote
Old 02-11-2010, 03:18 AM   #11
Back Road Runner
Scooby Guru
 
Member#: 60082
Join Date: Apr 2004
Chapter/Region: MWSOC
Location: Minnesota
Vehicle:
2004 Forester STI
Silver

Default

Yep, I've had my eye on that battery (or any similar product) ever since it was brought up on Nasioc some time ago. That price I can live without though. I'd much rather buy a cheap motorcycle/lawnmower battery before I spend a grand on a tiny battery. I might look at something like the Braille B106 or maybe something slightly less small, although I think the stock Subaru battery was only rated to 230CCA or something ridiculously small like that. I may save my full battery for winter use but toss in that type of battery somewhere in the back of the car during the warm months or disconnect and pull the main battery just when racing.

Good point on the weight under the jack point on the front of the car. I actually recall seeing that a while ago.

Hollow sways...maybe eventually, although, the stock 20mm bar isn't very hefty. (never really intend to go big because of rally-x)

A lightweight flywheel will go in once my stock one dies on me.

Mine's an old car, and I'm not really sure if it even has the harmonic dampers. I almost want to say it doesn't, but I'll need to check.

The JDM beams are only about 10lb lighter. I was looking at something more like Oswald's beams if anything actually fit the Forester that is, half the weight of the JDM beams.

I'm sort of stuck with the exhaust unless I get something titanium fabbed up. I'm running a big TWE header connected to a custom fabbed mild steel rear section. The rear section could be swapped eventually with titanium if the price is right.

My summer wheels are Rota Subzero in a 17"x7.5" size, relatively light among the Rota product line.

I do want to eventually remove the roof rack. It's not a big project for me, but there's the big issue of all the holes in the roof. I has 4 lengthwise rails running along the roof inside the two main side rails. These are screwed into the sheet metal. I can remove them, but then I have 20 or so holes in the roof to fill. I haven't really decided what I want to do about that yet. I almost want to find some sort of snap fit buttons or something to fill the holes. I don't really want to get into welding/filling and repainting the entire roof to get rid of them. Whatever goes there needs to be cosmetically pleasant and waterproof, and that might be quite a challenge. I may end up just making some really skinning rails in a matching blue plastic to go in the stock ones places. I don't know. At least the side rails are relatively straight forward and have parts available to delete it.

I still use the rear wiper, and since this isn't intended to be a complete race car, it'll stay. I'm more particularly concerned about front end weight then rear end given the car's natural weight balance.

The A/C stays too.

However, I may delete the ABS hardware eventually as I don't use it.

When I have my interior out again come spring, I'll need to start looking at if there's any interior parts that could be taken out without compromising safety or daily use.

Seats would be nice if something cheap was available that was also good and still civil. I'm still on the stock ones and there's a lot of isolation and bounce to them that I would be happy to lose. It's just that I'm a cheapskate and would prefer to find a pair cheaper then dirt rather then the uber $$$ that a lot of the better ones end up being.

Last edited by Back Road Runner; 02-11-2010 at 03:46 AM.
Back Road Runner is offline   Reply With Quote
Old 02-11-2010, 11:01 AM   #12
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

As far as seats go....I can drive an endless amount of time in my 15lb Kirkey. Way-way-way more comfortable than the Cobra's in the other car......45minutes and my arse is numb.....

Jay
Storm is online now   Reply With Quote
Old 02-11-2010, 11:12 AM   #13
sachilles
Scooby Specialist
 
Member#: 115107
Join Date: May 2006
Chapter/Region: NESIC
Location: Waitsfield VT
Vehicle:
02 wrx wagon
61 Morris Mini

Default

as for your butt going numb, a 3/4" memory foam(blue if you can find it) can make some the worst seats very comfy.
sachilles is offline   Reply With Quote
Old 02-11-2010, 11:14 AM   #14
RB5 Clone
Scooby Specialist
 
Member#: 30909
Join Date: Dec 2002
Chapter/Region: NESIC
Location: lastditchracing.net & 03 STI
Vehicle:
RA East Open Class
Champs 07-08-09

Default

Quote:
Originally Posted by Back Road Runner View Post

Mine's an old car, and I'm not really sure if it even has the harmonic dampers. I almost want to say it doesn't, but I'll need to check.
they're on there, my 93 Impreza L even had em. they just don't look like much, until your get em off and see how heavy they are.
RB5 Clone is offline   Reply With Quote
Old 02-11-2010, 12:11 PM   #15
RaceCarRiot
Scooby Specialist
 
Member#: 6542
Join Date: May 2001
Chapter/Region: South East
Vehicle:
1997 Ver IV
silver

Default

On my '97, which was stripped to the shell, so obviously some of these solutions will be a bit, shall we say, "impractical"...

- lightweight bumper beams
- carbon fiber hood (latch, release assembly removed)
- battery relocated to trunk
- lightweight flywheel
- car re-wired with a '96 brighton harness (lighter, believe it or not)
- no power anything
- every ounce of insulation under the carpet, in the door panels, trunk, ceiling, etc. removed - replaced headliner with the base model vinyl one with no grab handles, etc.
- any and all unnecessary damper weights removed
- washer tank / assembly removed
- obvious spare, jack, other trunk crap, etc.
- rear seatbelts, anchors, etc. removed (no one's gonna ride back there anyways, car would rub)
- removed crusty 13 year old airbags, etc.
- aftermarket stainless headers, cat-less track pipe.
- no rear speakers.
- a bunch of other little things I'm not thinking about.

Car still has A/C, PS, a radio, "full" interior to make it "liveable." Not sure numbers-wise how much weight it shaved off the car, but it's significantly lighter than a stock brighton, and WAY lighter than a stock RS.

Probably the two biggest weight-savers were the bumper beams, and especially the insulation (if you can live with that)...though YMMV with the insulation; obviously working with a bare shell offers you some advantages in getting stuff out that you normally wouldn't be able to. Just know that there is a LOT of that in there, and it's a significant chunk of weight.

Relocating the battery and leaving out the washer tank took a lot of weight out of the front end too. Just wash the windshield at gas stations. *shrug*

At this point, it's less of a car, and more of a "go-kart with weather protection and A/C" (you hear every squeak of the coilovers, every ounce of differential whine, every swaybar bushing thwacking over a bump, etc.), but with an otherwise stock 2.2, it gets around a road course WAY quicker than a new WRX.
RaceCarRiot is offline   Reply With Quote
Old 02-11-2010, 03:43 PM   #16
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

Quote:
Originally Posted by RB5 Clone View Post
they're on there, my 93 Impreza L even had em. they just don't look like much, until your get em off and see how heavy they are.
Pics please?
Storm is online now   Reply With Quote
Old 02-11-2010, 03:44 PM   #17
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

Quote:
Originally Posted by sachilles View Post
as for your butt going numb, a 3/4" memory foam(blue if you can find it) can make some the worst seats very comfy.
F-that......the seat is not worth my time to put any effort into it. I love the Kirley and it's lighter to begin with.

Jay
Storm is online now   Reply With Quote
Old 02-11-2010, 04:55 PM   #18
RB5 Clone
Scooby Specialist
 
Member#: 30909
Join Date: Dec 2002
Chapter/Region: NESIC
Location: lastditchracing.net & 03 STI
Vehicle:
RA East Open Class
Champs 07-08-09

Default

Quote:
Originally Posted by Storm View Post
Pics please?
heh, no pics, I was too covered with crusted mud and rust flakes while under there to do any camera work.

the 'harmonic balancers' are little button-shaped knobs at outer ends of the T-shaped rear subframe/diff carrier. they just unbolt.
RB5 Clone is offline   Reply With Quote
Old 02-11-2010, 06:13 PM   #19
Storm
Scooby Guru
 
Member#: 5218
Join Date: Mar 2001
Chapter/Region: MWSOC
Location: SAUL'S Motorsports
Vehicle:
96L Most Over-
Developed Beater

Default

I don't recall seeing those things on my car.....Maybe they ran away when I had the frame out for the tank replacement.....

Jay
Storm is online now   Reply With Quote
Old 02-11-2010, 06:35 PM   #20
RB5 Clone
Scooby Specialist
 
Member#: 30909
Join Date: Dec 2002
Chapter/Region: NESIC
Location: lastditchracing.net & 03 STI
Vehicle:
RA East Open Class
Champs 07-08-09

Default

these things are pretty ordinary-looking. discovered them while poking around under car doing a pre-race inspection/bolt check.

hmmm, what're them thangs?

peeked at rear susp schematic, huh, "harmonic balancers"

well, kin we git em off the car?

yes, couple 10mm bolts later, hey! those things are HEAVY

well, mebbe a couple-or-three lbs all told

we figured they were worth at least 10 sec per mile

file this item under "stuff you didn't know you didn't know, but now you know"
RB5 Clone is offline   Reply With Quote
Old 02-11-2010, 07:01 PM   #21
REDrum
Scooby Specialist
 
Member#: 61536
Join Date: May 2004
Chapter/Region: NESIC
Location: Peoples Republik of Cambridge
Vehicle:
WRX' 04Road02gravel
www.ToltecRally.com

Default

Don't forget titanium valve stem caps....
REDrum is offline   Reply With Quote
Old 02-12-2010, 02:39 PM   #22
bmxpunk
Scooby Specialist
 
Member#: 89599
Join Date: Jun 2005
Chapter/Region: RMIC
Location: middle of nowhere, wyoming
Vehicle:
1995 almost 22B:)
red

Default

I skimmed... did you remove that solid rubber mount under the lift plate on the front cross member? good god! I just took it out of my forester when i did steering rack bushings. Replacing the bumper beams on my DD and our rally car saved approx 40lbs IIRC. Thats alot of weight off the ends of the car and it is noticible, just don't get in an accident.
bmxpunk is offline   Reply With Quote
Old 02-16-2010, 08:39 AM   #23
MSI
Former Vendor
 
Member#: 95419
Join Date: Sep 2005
Chapter/Region: E. Canada
Location: montreal
Default

Titanium or aluminum body trim bolts too ... basic aluminum bolts to hold things like dash cards, fenders, wiper motors, etc are not too expensive and adds up as well. Don't get discouraged by the weight savings of ONE bolt, you need to look at the group!
MSI is offline   Reply With Quote
Old 02-16-2010, 06:37 PM   #24
RaceCarRiot
Scooby Specialist
 
Member#: 6542
Join Date: May 2001
Chapter/Region: South East
Vehicle:
1997 Ver IV
silver

Default

Quote:
Originally Posted by bmxpunk View Post
Thats alot of weight off the ends of the car and it is noticible, just don't get in an accident.
From what I've seen of GC's with lightweight bumper beams vs. the US ones that have been hit, it's a question of if you want to junk the bumper beam at the end of the day (lightweight), or bend the whole chassis around that point since it doesn't give (US).
RaceCarRiot is offline   Reply With Quote
Old 02-16-2010, 06:45 PM   #25
Craigs
Scooby Specialist
 
Member#: 24030
Join Date: Sep 2002
Chapter/Region: NESIC
Location: MA
Vehicle:
07 mazda3
Protoform p2

Default

"The JDM beams are only about 10lb lighter. I was looking at something more like Oswald's beams if anything actually fit the Forester that is, half the weight of the JDM beams."

Anyone else think these numbers are off?

I would have said 30lbs stock vs 4lbs for JDM.
Craigs is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
What are THE BEST chassis mods you can do? g3ninfinite Brakes, Steering & Suspension 17 11-15-2007 12:23 PM
What are the Chassis codes? Kincaid Racing Newbies & FAQs 4 01-05-2006 11:35 PM
What are the big differences between a JDM V8 STI short block and a USDM STI nos Factory 2.0L Turbo Powertrain 16 06-09-2005 09:25 AM
What are the turbo engine swappers doing about the radiator and hoses on GC/GM body? garface Subaru Conversions 57 04-13-2005 05:55 PM
Luke: What are the weights of 225/40/18 Kumho 712s and Yoko ES100s? SC WRX Tire & Wheel 5 07-07-2003 10:44 AM


All times are GMT -4. The time now is 07:36 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.