Rear Suspension woes... Suggestions?

Un0Turb0-WP · 27 Dec 2005, 17:56 (Ref:1490647)

So my race car project is currently going at a slow pace, been busy with other things in my life unfortunately... anyways, I have to work out what I'm going to do with the rear suspension on the car.
The car was a 1993 Mk2 FIAT Uno Turbo. It came out with a beam axle as standard but unfortunately it wasn't a very good design. Flexes extremely badly
and really hampers the cars performance.

What is the general consensus on rear beam axles? Good?? bad??
I saw that the later model Primera's also used rear beam axle, Does anyone
have any pictures of this? How do they fabricate new beam axles for racing?
Do they also use spherical bearings instead of bushes etc?

Since I'm free of any rules or anything, would you recommend I change to something independent at the rear something like independent wishbones with McPherson struts, or even more extreme, unequal double wishbones??

I'm just trying to work out what I should have done.
Look forward to your input.

Regards
Bevan

Un0Turb0-WP · 27 Dec 2005, 18:07 (Ref:1490656)

BTW if anyone is wondering what a Uno Turbo is, this is what the car looked like when it was still road registered and driving everyday.
http://img418.imageshack.us/img418/6...yred0205ma.jpg

I would of like to have bought a new bodyshell from the factory without the usual seam sealer etc, but they are no longer produced here.

graham bahr · 27 Dec 2005, 19:16 (Ref:1490687)

this is probably better off in the racing technonolgy forum, but eitherway

beam axles such as on your fiat are very common form many FWD cars, Vw golfs and Vauxhall (opel) caviliers, astra's, corsa's and nova's ford fiesta's mk5 escorts to name just a few, all of which have been raced very successfully.

i'm interested in what you mean by flexing, all fwd beam's that incorporate the trailing arms, flex in a twisting mostion, if they didn't you wouldn't have independant rear suspension.

unless you have very substanical fabrication, engineering and design facilities/skills
you are probably far better off modifying what you already have, poly bushes, reinforcing/stiffening the existing beam, fiat uno's certainly here in the uk at least have been successfully converted into fast race cars without resorting to axle transplants

schomosport · 27 Dec 2005, 19:34 (Ref:1490694)

Used to be a fiat race series that ran these and similar, don't know if it still operates. Have a look via www.brscc.co.uk - Fiat racing challenge. This is a clubbie type series and, within the regulations they operate, someone would probably put you in the right direction.

**Tim Falce** · 27 Dec 2005, 20:02 (Ref:1490705)

You may want to take a look at this. Although it is on a Ford it is the same principle. The guy cut the beam and re-welded it allowing for camber and toe adjustment. It is worth looking at for ideas.

Un0Turb0-WP · 27 Dec 2005, 20:05 (Ref:1490707)

Quote:

Originally Posted by graham bahr

this is probably better off in the racing technonolgy forum, but eitherway

beam axles such as on your fiat are very common form many FWD cars, Vw golfs and Vauxhall (opel) caviliers, astra's, corsa's and nova's ford fiesta's mk5 escorts to name just a few, all of which have been raced very successfully.

i'm interested in what you mean by flexing, all fwd beam's that incorporate the trailing arms, flex in a twisting mostion, if they didn't you wouldn't have independant rear suspension.

unless you have very substanical fabrication, engineering and design facilities/skills
you are probably far better off modifying what you already have, poly bushes, reinforcing/stiffening the existing beam, fiat uno's certainly here in the uk at least have been successfully converted into fast race cars without resorting to axle transplants

Hi Graham, Wasnt sure where to post it, mods pls move it to the right section .
Anyways, i meant it flexxes more then what most other cars do,
Im not sure if it makes sense, but like if i had to compare it to say a Vw Golf its nothing close to being as stiff...
I fully understand what you saying that it has to flex but isnt there some point as to how much it can? or the strength of the beam?

this what it looks like on the car:
http://img423.imageshack.us/img423/9081/axle5xj.jpg

It also uses a separate spring/damper combination.
Would Poly bushes really be enough? where it mounts to the body it uses quite a huge rubber bush, im just worried theres gonna be too much movement in that area...

Un0Turb0-WP · 27 Dec 2005, 20:09 (Ref:1490711)

Quote:

Originally Posted by falcemob

You may want to take a look at this. Although it is on a Ford it is the same principle. The guy cut the beam and re-welded it allowing for camber and toe adjustment. It is worth looking at for ideas.

Hi, I dont have to modify the rear axle for Toe/camber as i managed to get an ex group n racing axle which they modified to allow this..
But other then that its exactly the same as the std axle.

graham bahr · 27 Dec 2005, 20:36 (Ref:1490725)

with a lathe and a bit of work you could convert the beam axle bushes to using taper roller bearings for location, think motorcycle headstock if your not sure what i mean,
ir possibly fit a watts linkage, normally only used with live axles on RWD cars but theres no reason not to do so with a FWD beam

R59 · 27 Dec 2005, 22:53 (Ref:1490787)

Nylotron works well, and is easy to machine. Make a stainless insert to run through the middle.
Opel Corsa's have a similar beam, anti-roll bat runs through the beam, fixed at each end, which stiffens the beam by means of increasing torsional strength.

You could plate the beam (if it is an open U section) which would stiffen it.

What do your regulations permit?

Rob

John Cummins · 28 Dec 2005, 02:55 (Ref:1490821)

The beam is a stamping. I box them in by welding a plate over the opening from side to side. Takes most of the flex our of it and lets the springs do their job a little better.

ubrben · 29 Dec 2005, 17:35 (Ref:1491518)

There was a very good article in RE a while back describing the twist beam mods made by Triple Eight for the Astra BTCC cars. A very ingenious system and would remove the need for changing lots of other structure as you'd need to to run struts, etc.

Ben

Un0Turb0-WP · 29 Dec 2005, 17:44 (Ref:1491524)

Quote:

Originally Posted by ubrben

There was a very good article in RE a while back describing the twist beam mods made by Triple Eight for the Astra BTCC cars. A very ingenious system and would remove the need for changing lots of other structure as you'd need to to run struts, etc.

Ben

Hi Ben, Where was the article in? where can i get it?

Regards!

Un0Turb0-WP · 29 Dec 2005, 17:47 (Ref:1491527)

Quote:

Originally Posted by racing59

Nylotron works well, and is easy to machine. Make a stainless insert to run through the middle.
Opel Corsa's have a similar beam, anti-roll bat runs through the beam, fixed at each end, which stiffens the beam by means of increasing torsional strength.

You could plate the beam (if it is an open U section) which would stiffen it.

What do your regulations permit?

Rob

Theres no regulations on what can and cant be done to the suspension, so im pretty much free to do what i want

graham bahr · 29 Dec 2005, 18:26 (Ref:1491548)

Quote:

Originally Posted by Un0Turb0-WP

Theres no regulations on what can and cant be done to the suspension, so im pretty much free to do what i want

ok is it for road, rally or race track use? on the loose or smooth tarmac? is it both a race and a road car?

Un0Turb0-WP · 29 Dec 2005, 19:08 (Ref:1491566)

Quote:

Originally Posted by graham bahr

ok is it for road, rally or race track use? on the loose or smooth tarmac? is it both a race and a road car?

Racetrack use only, smooth track, 100% Race car, Car is no longer registered to drive on the road.

graham bahr · 29 Dec 2005, 20:19 (Ref:1491596)

ok that makes it simple,

a fwd tarmac race car doesn't need anything fancy in the rear suspension dept, as it has little travel and are usually sprung so as to make the rear end loose thus counteracting the natural understeer inherent in FWD cars, i.e they run with the rear end almost solid its not unusual to find fiesta's with 1000lb inch rear springs, and mini's with rear roll bars about an inch thick.

so i would say stick with the fiat beam, improve the bushing materals, the beam can be dramatically stiffened up by welding plates across any open or "L" shape section, and get yourself some decent dampers valved to suit some bloody stiff rear springs.

all this assumes you are going to use some decent grippy tyres, i.e slicks or at least something along the lines of yoko 032's,48's etc

Un0Turb0-WP · 29 Dec 2005, 21:50 (Ref:1491652)

Hmmmm thanks for the info Graham, I rekon thats the best way to go. Im gonna try and find out if i can somhow have the part where the bush normally goes machined or something so i can use a bearing there instead.

Im just wondering the plate where the spring sits, should i remove that and have a new box section welded there, as the rear will have coilovers instead of a separate spring/damper combination.
Also Im probably going to have to stiffen up the mounting point on the body where the axle bolts to, perhaps tie it into the rollcage etc.

Thanks again for the help

Un0Turb0-WP · 29 Dec 2005, 21:53 (Ref:1491655)

Another thing, What about fitting an adjustable Anti Rollbar on the rear so that i can fine tune it even more?? I dont want to make it tooo stiff now? or wont that be an issue?

Un0Turb0-WP · 1 Jan 2006, 00:06 (Ref:1492682)

Anyone got a scan of the suspension article from RE? we dont get RE here and I would really like to see what they done. thx

graham bahr · 2 Jan 2006, 00:08 (Ref:1493086)

Quote:

Originally Posted by Un0Turb0-WP

Another thing, What about fitting an adjustable Anti Rollbar on the rear so that i can fine tune it even more?? I dont want to make it tooo stiff now? or wont that be an issue?

rear anti roll bars are usually a good idea on a FWD car, a nice stiff rear bar can help traction out of the turns and turn in as it will help to keep the front of the car well planted. having said that i feel its important to get rear springs somewhere near right first, then fine tune with the roll bar.

Mackmot · 2 Jan 2006, 02:22 (Ref:1493148)

Try droop stops. They dont allow the unloaded wheel to travel all the way to the ground and mean you use the weight of that wheel to stabilise the car. It can be done really easily with a bit of ratchet strap webbing bolted to the chassis above and strapping the trailing arm to sit at static ride height position.

Un0Turb0-WP · 2 Jan 2006, 19:36 (Ref:1493621)

Quote:

Originally Posted by graham bahr

rear anti roll bars are usually a good idea on a FWD car, a nice stiff rear bar can help traction out of the turns and turn in as it will help to keep the front of the car well planted. having said that i feel its important to get rear springs somewhere near right first, then fine tune with the roll bar.

Fantastic!! Once again thanks for all the advice so far Graham I really appreciate it!
I'll take some pictures in the next few days on the axle just so I could get some pointers on what specifically to do. I had a close look at it today and it looks like there are quite a few places that need some beefing up or modification.

Cheers!

Un0Turb0-WP · 2 Jan 2006, 19:39 (Ref:1493624)

Quote:

Originally Posted by Mackmot

Try droop stops. They dont allow the unloaded wheel to travel all the way to the ground and mean you use the weight of that wheel to stabilise the car. It can be done really easily with a bit of ratchet strap webbing bolted to the chassis above and strapping the trailing arm to sit at static ride height position.

Hmmm havent gotten that far yet, But doesnt the damper have this built in or can you have it built in?

graham bahr · 2 Jan 2006, 20:30 (Ref:1493656)

Quote:

Originally Posted by Un0Turb0-WP

Hmmm havent gotten that far yet, But doesnt the damper have this built in or can you have it built in?

it all depends on the amount of extension that the damper has, most performance dampers are shorter and achive the same thing as the strap, which maybe coupled with rear anti roll bars is why you often see fwd cars cocking a rear wheel up in the air

Un0Turb0-WP · 5 Jan 2006, 11:27 (Ref:1495421)

Here are some close up pictures of the rear axle:

The section where the rubber bush mounts: (diameter is roughly 47mm)

http://img233.imageshack.us/img233/8819/axle0013dr.jpg

The Adjustable Stub Axle (excuse the surface rust.. been standing for a while

)

http://img216.imageshack.us/img216/6716/axle0023yx.jpg

Underside of the Axle:

http://img232.imageshack.us/img232/3453/axle0036xc.jpg

Closeup of the Underside:

http://img207.imageshack.us/img207/4446/axle0049tp.jpg

Underside of Spring Pan:

http://img220.imageshack.us/img220/2261/axle0054nd.jpg

Top View of Spring Pan and trailing arm:

http://img207.imageshack.us/img207/2889/axle0060sz.jpg

So what do you guys think? Should i remove the spring pan and box that section in better?
Any other idea's??

Thanks in advance!
Bevan

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