Rear ARB and/or strengthened rear axle? What to change?

[Alex__]

Could do with some suspension advice off people who know what they are talking about please.

On my track car I am currently running a PMS 19mm RARB, and after doing some reading up I am thinking of changing to a 22mm one to change the handling characteristics slightly.

I was planning on fitting a strengthened rear axle using the PMS kit, at the same time as fitting coilovers. http://www.pure-motorsport.co.uk/cl...pension/rear-axle-stiffening-profile-kit.html

My question is, would stiffening the rear axle have the same effect on handling as running a stiffer ARB?

With a stiffer axle is there any need to run an ARB?

Obviously theres a lot of work involved with fitting the PMS axle kit, do would I save a lot of time and hassle by not bothering with it, and just sticking with the 22mm ARB? Or are there other benefits such as less flex?

 

[JamesBryan]

Do you think you need it stiffer or is more of that you just want it?

If you're going for the beam strengthening kit then just stick with the 19mm RARB.

Or the 22mm bar without the strengthening kit.

22mm bar + the kit will be mega stiff.

 

[JamesBryan]

Oh and to use the full strenghtening kit, you need to run a full coilover on the rear as the kit removes the rear spring perch of the standard setup.

You can leave that part of the kit out, but then that's pointless IMO.

 

[JB21]

22mm bar and Coilovers should be plenty stiff enough. You can also go stiffer spring rates as well...

 

[Alex__]

Do you think you need it stiffer or is more of that you just want it?

If you're going for the beam strengthening kit then just stick with the 19mm RARB.

Or the 22mm bar without the strengthening kit.

22mm bar + the kit will be mega stiff.

Id like to dial out some understeer/induce oversteer (in the dry Im talking now). The strengthening kit is a lot of faff to install, so just changing the RARB is my preference.

I was just wondering if there were any advantages of running just the strengthening kit VS standard axle + RARB?

Oh and to use the full strenghtening kit, you need to run a full coilover on the rear as the kit removes the rear spring perch of the standard setup.

You can leave that part of the kit out, but then that's pointless IMO.

Yeah, as above, I plan to install full coilovers (ASTs) at the same time as the strengthened beam... if I decided to go down that road.

22mm bar and Coilovers should be plenty stiff enough. You can also go stiffer spring rates as well...

Happy days then. What spring rates are people running on track-only clios? (Should probably a separate thread really)

 

[JamesBryan]

You want to be looking at the 8kg/80nm/450lb range for track.

You can get away with a softer rear spring on a full coilover.

Harder springs on the rear are used on separate spring and damper setups. I'm not sure on the technicalities of it.

 

[JB21]

I've currently got 9kg/90nm/506lb fronts and 11kg/110nm/618lb rears, I'm yet to try these though, so will let you know how the harder springs at the rear coupled with a rarb works out...

 

[JamesBryan]

I've currently got 9kg/90nm/506lb fronts and 11kg/110nm/618lb rears, I'm yet to try these though, so will let you know how the harder springs at the rear coupled with a rarb works out...

Should be fun haha.

 

[JB21]

Should be fun haha.

Especially at Aintree with its bumpy track, lets just hope it doesn't rain :fearscream:

 

[Alex__]

I've currently got 9kg/90nm/506lb fronts and 11kg/110nm/618lb rears, I'm yet to try these though, so will let you know how the harder springs at the rear coupled with a rarb works out...

Ive noticed on a few threads that a lot of people seem to run a harder rear spring. Not sure what a good starting setup is yet tbh!

 

[JB21]

Ive noticed on a few threads that a lot of people seem to run a harder rear spring. Not sure what a good starting setup is yet tbh!

Having done a lot of reading myself mate, I'd say 8kg/450lb minimum front and rear for a track car. People tend to use harder springs at the rear to aid turn in and reduce under-steer but with the wanted/unwanted side effect of over-steer and general twitchiness at the rear.

 

[bloke]

stick with the 19mm bar if you're bracing the beam. i just built one with same set up running bc's and it was good. put in some good stage times.

 

[Alex__]

stick with the 19mm bar if you're bracing the beam. i just built one with same set up running bc's and it was good. put in some good stage times.

I was planning on bracing the beam, but its a lot of work to remove it, get the plates welded on, paint it, then refit. So now leaning more towards just running a stiffer RARB.

But wondering if I should go down the strengthening kit option if I plan to run full slicks in the future?

 

[bloke]

it's not that bad a job to do. bit fiddly but done worse.

 

[Alex__]

But wondering if I should go down the strengthening kit option if I plan to run full slicks in the future?

Any thoughts on the above @JB21 @JamesBryan ?
Just to throw another spanner in the works when I thought Id made up my mind :smile:

 

[JamesBryan]

Any thoughts on the above @JB21 @JamesBryan ?
Just to throw another spanner in the works when I thought Id made up my mind :smile:

If you plan to run full slicks then yeah it's probably worth it.

You'll also have to think about bigger bearings and things, because the increased strain on them with slicks will kill them quicker.

If it's just for fun on track days, you have to think to yourself is it really worth it all. Just a bit of fun at the end of the day.

 

[Alex__]

If you plan to run full slicks then yeah it's probably worth it.

You'll also have to think about bigger bearings and things, because the increased strain on them with slicks will kill them quicker.

If it's just for fun on track days, you have to think to yourself is it really worth it all. Just a bit of fun at the end of the day.

True, but part of the motivation to run slicks is the cost benefits. Can pick up part worns for very cheap, and even new toyo RS1s are the same price now as what Im paying for new A048s.

But we will see, still a lot of mods to do to the car before I get to that stage.

 

[JamesBryan]

True, but part of the motivation to run slicks is the cost benefits. Can pick up part worns for very cheap, and even new toyo RS1s are the same price now as what Im paying for new A048s.

But we will see, still a lot of mods to do to the car before I get to that stage.

Yeah slicks are cheap. How much are A048's?

Have you considered Dunlop DZ03G or Nankang AR1?

 

[Alex__]

Id like to try direzzas next!
Once my current a048s are dead ill try them.
Think I paid 120 per tyre for a048s

 

[JamesBryan]

Id like to try direzzas next!
Once my current a048s are dead ill try them.
Think I paid 120 per tyre for a048s

The Dunlops are about the same price i think.

I thought the Yokos were more than that.

 

[JB21]

Been looking at slicks myself, and I would like to try them at some point but will be learning the car on decent coilovers first. Plus I've got suspension and chassis parts to upgrade first.

I get all my semi slicks part worn from ebay for peanuts, no point in buying new when you can pay less than a quarter of the price from new, still with decent tread left. I just make sure they're not over 10 years old.

 

[JKING3008]

I've just bought the strengthened axle from mk2dillion for coilovers as I'll be getting the AST 5100 kit.

 

[bloke]

Am sure a few track day organisers say you've got to be caged to run slicks?

 

[JB21]

Am sure a few track day organisers say you've got to be caged to run slicks?

Yep MSV even require MSA/FIA spec.

 

[JamesBryan]

My mate with a Megane has done a few days with full slicks and no cage, no one has said anything yet.

 

[NorthloopCup]

Strengthening the rear beam will help with flex, but I'm sure it's designed to reduce deflection more than anything, and reduce geometry changes.

Running a thick rear arb is THE way to do it. The reason why most people run stiffer rear springs with the Ast coilovers, or any rear coilovers for that matter, is to increase the rear roll stiffness. This isn't the correct way to setup a chassis, but it does work.

 

[IanLee]

Strengthening the rear beam will help with flex, but I'm sure it's designed to reduce deflection more than anything, and reduce geometry changes.

Running a thick rear arb is THE way to do it. The reason why most people run stiffer rear springs with the Ast coilovers, or any rear coilovers for that matter, is to increase the rear roll stiffness. This isn't the correct way to setup a chassis, but it does work.

Correct. I haven't seen one of these strengthened rear axles, but looking at the kit it is to stop the stub axle flexing relative to the beam. The torsional stiffness is not changed at all. A thicker anti roll bar will change the torsional stiffness. The axle strengthening and anti roll bar are doing two different things. Unless you are running slicks I doubt you'd feel any handling change with the axle strengthening and the same anti roll bar.

 

[Sonic Boom]

I run a PMS rear beam with a Whiteline RARB and 700lb rear springs (500lb up front)
I find it spot on to be fair.
Rich