View unanswered posts | View active topics It is currently Sat Apr 20, 2019 8:41 am



Reply to topic  [ 22 posts ]  Go to page 1, 2  Next
rear springs on front etc ? 
Author Message

Joined: Tue Jan 11, 2011 1:30 pm
Posts: 35
Car(s): isuzu bellett pr20 rhd
Reply with quote
Hi all,

Heard various conflicting reports about putting the rear coil springs on the front of Belletts. My car had original front springs which made it ride kinda high at the front. Swopped them for a set of rears I had and it sits a lot better now.

Heard some folk saying this worked well, others saying not good. (Cars not on the road yet so I don't know how it will handle).

Also any easy way of beefing up the front anti-roll bar as it looks kinda puny.

Advice / comments anyone ?

Thanks, Jeff (scotland)


Tue Jul 24, 2012 7:39 pm
Profile
User avatar

Joined: Tue May 10, 2011 2:23 am
Posts: 2613
Location: Melb.
Car(s): '72 Sport Bellett (imported 180912), had Belletts in past, 2 sed, 3 GT's. M/B A250 Sport, i30
Reply with quote
Jeff
there is a thread on springs somewhere on here mentioning colour dots etc. Maybe not much help to you as you most likely don't have a pile of springs to choose from....... but it might give you an idea of the amount of lowering for the ones you seem to have.

I have done this many years ago and it works. 30-40mm from (bad) memory

The GT front sway bar is thicker but again, you won't have access to one i guess. They are not too thick on the ground here either .

With a LOT of luck, searching car wreckers who still have very old cars, might turn up something but really a long shot.

glenn

_________________
'72 PR60 Sport


Wed Jul 25, 2012 12:35 am
Profile WWW

Joined: Wed Oct 08, 2008 12:16 am
Posts: 74
Location: New Zealand
Car(s): 1968 Isuzu Bellett
Reply with quote
My car drives nicely with rear springs in the front :)


Wed Jul 25, 2012 12:46 am
Profile

Joined: Wed Sep 24, 2008 10:05 am
Posts: 543
Location: 12,450 miles away from the Big Warehouse in Melbourne
Reply with quote
Might be this thread:
viewtopic.php?f=35&t=122
But I don't see any mention of rear springs on the front, and I remember that discussion too.

OK, this is going to read like someone raining on the parade. But everything I've learned about suspension tuning was learned the hard way. And I have not tuned a Bellett suspension, so I won't pretend to say what is or isn't a good setup for this particular car.
I race autocross, which in North America, is similar to Japanese Gymkhana. Cones are set up marking a course on a paved parking lot. Course elements include slaloms, offsets, chicanes, Chicago boxes, and hairpin, hard, and sweeping turns. Compared to Gymkhana, Autocross looks like a mini road course. The course design is supposed to limit speeds to no higher than 60 or so MPH, so we run in second gear, bouncing off the rev limiter. It's 45-60 seconds of panic maneuvers, cross the finish line, slam on the brakes, and start breathing again.
I race an FF or FWD car. In general, these cars tend to understeer the harder you push them. For this type of racing, it is desirable to have just a little bit over oversteer, so you can aim for a tight line, and the rear end swings just enough that the inside rear tire misses the apex cone. Just a little bit more oversteer, and the tail swings out and the car spins, and your run is over. So we spend a huge amount of time turning the suspension.
In the past, I have followed some really bad advice from internet sources, or tried to solve issues without thinking them through thoroughly, and made arbitrary changes to one end of the car and not the other. These things seemed good driving around on the street and on the highway, but put the car on the race course and it would spin, and in one case put the car uncomfortably close to a course worker who probably needed clean shorts worse than I did afterwards. And I was upset enough to feel nervous about driving the car home on public streets without undoing the offending change that caused the instability.

What I have learned is that you must treat the front and rear suspension as a matched set. If the car is even remotely well balanced, then making a big, arbitrary change to one end is going to throw things way out of balance, and it might feel good driving, until you have that sick feeling that you are about to be wearing glass and twisted metal while the car is not turning when you have the wheel turned as far as it will go to the side, or you are looking out the windshield in the opposite direction as the car is traveling.

According to the book, the front springs are 3.5 kg-m (196 lb.), and the rear springs are 5.65 kg-m (316 lb.). If the car handles anywhere close to neutral or the typical slight understeer road-safe manner that most car makers seem to like their stock setup to be, then doubling the front spring rate by swapping in a set of rear springs, should create some pretty serious understeer. And the thing is that unless you take the car out and do something like 45-60 seconds of panic maneuvers, most people wouldn't find out that this change causes the car to understeer at the limit, and just slides in a straight line when the front wheels are cranked sideways, until they are trying to avoid a car pulling out in front of them, a child running out into traffic from between two cars, or a kangaroo that suddenly darts out of the bushes and into the road in front of you on a dark night.

If you want to do it right, use the front to rear ratio of the stock setup as a starting point. Increase spring stiffness (and include the sway bar rates in this consideration), keeping the front and rear ratio similar to the factory setup. If the vehicle is oversteering or understeering, make small, incremental changes to find out what happens.
Use standardized springs (coilover springs), that have a measured spring rate, from a company with a good reputation (a company that makes springs for racing).
Adjusting ride height will involve threaded spring perches, or better yet threaded lower suspension mounts.
The original dampers will not be able to handle significantly stiffer springs, and adjustable dampers are desirable for tuning and flexibility if you find you need to change spring rates to adjust the handling.

It's not the cheap or easy way, but it involves less auto body repair and fewer hospital stays.


Wed Jul 25, 2012 2:01 am
Profile
User avatar

Joined: Tue May 10, 2011 2:23 am
Posts: 2613
Location: Melb.
Car(s): '72 Sport Bellett (imported 180912), had Belletts in past, 2 sed, 3 GT's. M/B A250 Sport, i30
Reply with quote
I am sure you are 100% correct there JT191.

the racers among us will have used the appropraite spring rates etc. The info from the book though gives "range of load acceptable" not an actual spring rate per inch or cm from what i can see though ?

The rest of us, who like a lower front, have gone with the rear spring setup basically for looks alone. Few of us race these cars on the street. None i hope actually. So far, no kids or kangaroos have jumped in front of us. Maybe good luck so far i guess as these things can happen and the point is taken.

My Sport, has lowered front and rear. Apparently a factory stage 3 (?) setup or option. Have no idea though what spring rates are used. When it arrives i will be looking at the coloured dots in the hope of finding out just what is has.

Glenn

_________________
'72 PR60 Sport


Wed Jul 25, 2012 2:52 am
Profile WWW
User avatar

Joined: Fri Sep 26, 2008 6:16 am
Posts: 1155
Location: Adelaide north near the hills.
Car(s): Roman Red 1965 Sedan, Mint 67 Sedan Auto, 1967 GT , 1.5x 1967 sedans, 1968 Deluxe Sedan, 1965 Wasp Ute (Resto project)
Reply with quote
Glenn. sounds like you may be able to save quite a few of us a great amount of time if you can get as much info from your Sport Sedan as possible. Still say factory Sports setup is the best. looking forward to further posts regarding the info you can gleen!

Cheers


OZ

_________________
So many toys and so little time to play!!


Wed Jul 25, 2012 11:28 am
Profile

Joined: Wed Sep 24, 2008 10:05 am
Posts: 543
Location: 12,450 miles away from the Big Warehouse in Melbourne
Reply with quote
Glenn wrote:
The info from the book though gives "range of load acceptable" not an actual spring rate per inch or cm from what i can see though ?


The book shows the "spring constant" two lines above the "range of load acceptable".
For the front, there is a typo for the units of kg-m, which is correct for the rear as kg-mm (I think, metric measurements confuse me).

Image
Image
Image

The three different load range springs listed is a little confusing, because each is indicated to have the spring constant and length above, but a different carrying capacity. Maybe this indicates progressive rate springs? And the spring constant remains the same at installed height?

A few serious problems with the book information:
The spring data is listed for PR20 and PRD10, the vehicles in production when the book was originally written. The spring rates for the PR90, PR91, and PR95, would almost certainly be different, and would be a more desirable starting point to work from.
The data from the "factory stage three" springs would also provide a big jump in the right direction.

No idea about the children and kangaroos running out into the street down there near the Big Warehouse In Melborne. The PBS "Urban Roo" documentary seemed to show them pretty thick on the lawns and streets of Australia. Here on the other side of the world we have deer, which are smaller, more nimble cows, with clusters of spears on their heads (antlers). I haven't had the pleasure of hitting one, but bought a car with an antler hole in the hood from the previous owner hitting one.
Yesterday I had the displeasure of a Dodge SUV driver pulling out in front of me on a little two lane road, 75 feet past the railroad tracks I was cresting at the time. Lock up the brakes in mid air, squeal to a stop after the car comes back to the ground, and glare up at the idiot that almost caused an accident who was inches away from where my car came to rest.
Saturday, I was following a pickup that suddenly came to a dead stop on a four lane road. No turn signal. Then the guy starts looking for a parking space to pull into on the side of the road.
These are becoming everyday experiences. Maybe I need to move into the country.


Wed Jul 25, 2012 2:55 pm
Profile

Joined: Fri Mar 20, 2009 8:23 am
Posts: 1816
Reply with quote
jt we have deer here too we don't worry bout them to much theres lot's of other things here to kill us :lol: Red back has to worry bout water buffallo up his way they are like hitting the wharehouse in melbourne.


Wed Jul 25, 2012 10:00 pm
Profile
User avatar

Joined: Tue May 10, 2011 2:23 am
Posts: 2613
Location: Melb.
Car(s): '72 Sport Bellett (imported 180912), had Belletts in past, 2 sed, 3 GT's. M/B A250 Sport, i30
Reply with quote
pretty sure there were no variable rate springs in a Bellett or maybe even other cars at the time?

OK on the constant too. I missed that ! Quite a difference front/rear as you suggested, JT191.

My guessing is that the springs were made to a nominal length as shown in the info, then graded in pairs for deflection and colour dotted by the makers so that "a matched pair" would be fitted later on the assembly line.

It will be interesting to check out my Sport although I won't be removing anything at this stage to check spring free lengths ! I can find the dots hopefully and measure the spring wire thickness though. Count the turns also.

Don't beleive the hype.
Truth is, JT191, most of us in Oz live in the 3 large cities here on east coast and would not see a kangaroo unless we went to a Zoo.

_________________
'72 PR60 Sport


Wed Jul 25, 2012 10:12 pm
Profile WWW

Joined: Fri Sep 30, 2011 5:08 am
Posts: 38
Car(s): 1978 TD Gemini
Reply with quote
You'd be surprised Glenn, I used to work in Mulgoa. An at worst 45 min drive from Liverpool (Sydney) where I live and dodging kangaroos was an almost daily experience. I've even got a crinkled drivers door skin on my daily from a coming together with a roo.


Thu Jul 26, 2012 3:07 am
Profile
User avatar

Joined: Tue May 10, 2011 2:23 am
Posts: 2613
Location: Melb.
Car(s): '72 Sport Bellett (imported 180912), had Belletts in past, 2 sed, 3 GT's. M/B A250 Sport, i30
Reply with quote
yeah, but that is out in the sticks :lol:
was it a roo or a Wallaby though. We have Wallabies about 5km from here but it's national park.

there have been some sitings on the near to outskirts of Melbourne also but its a pretty rare occurance. More chance still to see one in the Zoo !

There is a perception that they are everywhere though. I have been to the USA a number of times and this often comes up.

_________________
'72 PR60 Sport


Thu Jul 26, 2012 4:06 am
Profile WWW

Joined: Fri Sep 30, 2011 5:08 am
Posts: 38
Car(s): 1978 TD Gemini
Reply with quote
Definately a roo. But luckily a small one, otherwise I may have copped a headbutt because my window was down :shock:


Thu Jul 26, 2012 4:29 am
Profile
User avatar

Joined: Tue Oct 28, 2008 12:17 pm
Posts: 2432
Location: Rye Park, N.S.W.
Car(s): Doris, AuntyMary, Shrek, Jimmy; GT, Wasp, Flo & Sed unrestos; 65 Elf; 81 Rodeo, Sigma, 02 Forester; 07 Santa Fe CRD.
Reply with quote
Can't help but chuck in my bit on 'roos.................

We are fortunate enough to be in the half of the population that doesn't live in Sydney & Melbourne. We get plenty of Skips, they are the fillers of panel beater's shops. In our first year of new Subaru ownership, we had 3 Kanga claims, after a recent claim in the previous car. Tolerant insurance company. Only hit 2 since then though, in 9 years!
You don't hit the ones you see, just the ones that spring from the scrub into your grille. :( Kamikase style. I hate hitting any critters.........
It's why Hiluxes have those gates welded to the front.

You city dwellers only have to watch out for that most unpredictable critter, the Drongo. :roll:

Cheers, Matt.

_________________
Life is far too short not to fill it with what you love. - Jackie French.[/size]


Fri Jul 27, 2012 5:07 am
Profile

Joined: Mon Jan 05, 2009 10:39 am
Posts: 1135
Location: Adelaide Hills
Car(s): GU Patrol, AU ute, 1969 florian deluxe, 1976 Luv & 1980 KB 4x4 isuzu
Reply with quote
right of topic but i live in an area where there are a few roo's, i have been lucky enough to avoid them but they are about. no set time as to when they are about but i have seen them crossing the road at anytime! as long as they dont hit my bellett or florian im happy to leave them be.... maybe time to try some roo tail soup!

_________________
I am "that" Florian guy.
never buy a car you cant push.


Fri Jul 27, 2012 9:04 am
Profile

Joined: Tue Sep 16, 2008 11:54 am
Posts: 2450
Reply with quote
we've all been doing the "rear spring to front" converstion for years, without problems... and it's all about getting the correct "colour" springs in my book.
i use the white dots in the front, and yellows in the rear. i tried yellow front and red rear once, but as i like a harder ride, it wasn't to my liking.
the main thing is u MUST make sure u have a matched pair of springs at each end of the car. ie: not a yellow at one front corner and a red at the other for argument sake.

sway bar wise... as Glenn said, yes, a GT bar is thicker. i use one in my race car. but the bar itself isn't the problem...
it's the mounting points.
have a look under the front of a Bellett. the outer ends are rubber mounted to the lower suspension arms, which works well...
but the inner mounts are done via silly little drop rods that are mounted in 4 rubbers each! this will NEVER make the sway bar itself work properly, as there is simply too much flex in the whole assembly. look at any other car too, and the bar is mounted straight to the subframe, crossmember, etc, not on little rods that are rubber mounted themselves...
we've all had the bar "walk" across the front of the car where it sits to one side more than the other... that's caused by this area of flex.
i've even seen cars where there's been enuf wear in the rubbers (which trust me, isn't much...) that u can physically grab the bar in your hand and move it back and forth in this area... so it would be having zero effect whilst driving.
to fix it, you have to beef up the mounts on the crossmember, which is easliy done with some 1.5inch square steel tube between the flat plate that the bar mounts too and the crossmember itself.

_________________
I like apples....


Sun Jul 29, 2012 12:49 am
Profile

Joined: Tue Jan 11, 2011 1:30 pm
Posts: 35
Car(s): isuzu bellett pr20 rhd
Reply with quote
Thanks to all the responses - just going to see what colour code my springs are.

Will get back and let you know how she handles once she's on the road.
Thanks guys, Jeff


Thu Aug 02, 2012 12:55 pm
Profile

Joined: Tue Jan 11, 2011 1:30 pm
Posts: 35
Car(s): isuzu bellett pr20 rhd
Reply with quote
Mr pr91,

My front springs are yellow (which are a pair of rears off donor car. My original rears, still on the rear don't seem to have any obvious colour code.....any ideas what sort of a ride I'l get with this combo ?

Jeff


Thu Aug 02, 2012 1:08 pm
Profile
User avatar

Joined: Tue May 10, 2011 2:23 am
Posts: 2613
Location: Melb.
Car(s): '72 Sport Bellett (imported 180912), had Belletts in past, 2 sed, 3 GT's. M/B A250 Sport, i30
Reply with quote
PR91 wrote:

sway bar wise... as Glenn said, yes, a GT bar is thicker. i use one in my race car. but the bar itself isn't the problem...
it's the mounting points.
have a look under the front of a Bellett. the outer ends are rubber mounted to the lower suspension arms, which works well...
but the inner mounts are done via silly little drop rods that are mounted in 4 rubbers each! this will NEVER make the sway bar itself work properly, as there is simply too much flex in the whole assembly. look at any other car too, and the bar is mounted straight to the subframe, crossmember, etc, not on little rods that are rubber mounted themselves...
we've all had the bar "walk" across the front of the car where it sits to one side more than the other... that's caused by this area of flex..


I supect in a street car that the little rods at the front allow some front rear flex for the sway bar as the suspension moves over full travel range. This would tend to allow the end of the sway bar to move in and out of the end rubbers much less as the lower arm moves. [one wouild need to draw this up as an arc over the range of the suspension travel relative to the inner bushing, to see how it works.]

Izusu would have spec'd the upper little link rubbers to be fairly stiff i would imagine to allow "just enough" front rear flex. All in conjunctiom with the the original spec. end rubbers too of course. Over time, these upper tie rubbers become next to useless of course unless replaced with the same type. Impossible now.

In a race car, where the suspension movement would be much less, then this is less of a problem. So the rods can be dispensed with.

my 2c of thoughts.....

glenn

_________________
'72 PR60 Sport


Fri Aug 03, 2012 12:47 am
Profile WWW

Joined: Tue Sep 16, 2008 11:54 am
Posts: 2450
Reply with quote
did the same sway bar mod on my GT when i resto'd it.
very happy with it.

_________________
I like apples....


Fri Aug 10, 2012 3:37 am
Profile
User avatar

Joined: Tue May 10, 2011 2:23 am
Posts: 2613
Location: Melb.
Car(s): '72 Sport Bellett (imported 180912), had Belletts in past, 2 sed, 3 GT's. M/B A250 Sport, i30
Reply with quote
I'm guessing here but would think with no front rubbers, the sway bar end rubbers might wear out a little quicker.

The arc of the lower arm movement is totally different to the arc of the sway bar. Something has to give.

_________________
'72 PR60 Sport


Fri Aug 10, 2012 3:44 am
Profile WWW
Display posts from previous:  Sort by  
Reply to topic   [ 22 posts ]  Go to page 1, 2  Next

Who is online

Users browsing this forum: No registered users and 4 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group
Designed by ST Software for PTF.