R400 suspension geometry and set-up

[pandjack]

Hi all

 

As a newbie, the first thing I need to do is applaud you all on the breadth & depth of technical knowledge available to tap into on blatchat - awesome!!

 

The second thing is to ask a not necessarily dumb question - but one to which I can't find a concise answer to - 'what would be the most appropriate castor,camber,toe,corner weight ratios & tyre pressures for my 2004 K series R400 as a starting point for my up-&-coming (& first) hillclimbing season?' Additionally I've read a couple of posts heralding the benefits of adjustable ARB's - worthwhile? or should I get some competition miles in & assess the balance of the car from a 'standard' platform first?

 

I'm currently running the car on 15" CR500's (195x45 front & rear) but have a set of 13" (175x55 front/205x55 rear) for competition, & whilst I've managed to glean a fair raft of info on the subject some of it's conflicting so thought it'd be worth floating the question before I get the car flat floored next week.

 

Many thanks in anticipation

 

[Mark w]

First of all get the 13 inch wheels put on and I would set the pressures at 18 psi cold all round .

 

As for set up you will get 10 replies all saying something different . personally I run my rear ARb on the stiffest setting because I like the way it drives that way .I have a blue bush front ARB .

 

my ride height is set with the front lower wishbones set horizontal which gives me about 70mm clearance under the sump , I then have the CC recommended rake ( up at the back , cannot remember but I think it's about 15mm ) Caster on mine is set with two washers either side of the wishbone and camber and toe were set from that starting position . From memory I think the toe is pretty much parallel .

 

Now stands back and awaits the flood of advice telling me I have it all wrong

 

 

 

Edited by - Mark W on 12 Mar 2012 20:02:48

[Richard Price]

Personally, I'd say that neither set of tyres is ideal on the hills.

 

I'm running supersoft 215/50-13 Kumho V70's all around and run a red 5/8" front ARB and no rear ARB. I find that running a rear ARB reduces traction and makes the back end unpredictable.

 

Many will tell you that you need these dampers or those dampers, but my car has standard springs and dampers, an has been reasonably competitive in the clubs speed championship.

 

I would not bother with an adjustable front ARB, and if I did have one, I would not mess with it between runs. If you do adjust it between runs, you don't know quite how the car will handle on the next run, so there will be an element of reservation in your driving as you learn the cars new characteristics.

 

Mark W talks of running the wishbones parallel to the ground, but doing that with the 13" CR500's may not give as much ground clearance as you'd like.

 

I'd run between 2 and 2.5 degrees negative camber and zero toe. I run 4 washers behind the wishbones.

 

or should I get some competition miles in & assess the balance of the car from a 'standard' platform first?

That's a good idea

Thewre is much more that comes from driving the car than this setup or that.

 

Rather than spending money of car upgrades, I'd make sure that you have an incar video set up that works. It's the easiest way to make the car go faster

 

 

 

 

[Englishmaninwales]

has been reasonably competitive in the clubs speed championship

 

Understatement of the year. 😶‍🌫️

[Mark w]

Richard

I bow to your better experience but my comment about wheels was to do with the size , I don't think that the original post actually stipulated CR500 for the 13 inch , my reccomendation was based on the fact that generally the seven is thought to ride and handle better on the smaller wheels .

 

As far as sump clearance is concerned I do about 3000 road miles a year and have never had a problem with ride height ( on CR500s ) , yes it is lowish but I don't seem to be collecting any scrape marks on the sump ,the only issue I have seen is with speed humps where the gearbox can catch if the ramp angles are steep .

 

interesting to see you don't run a rear ARB , maybe that's to do with the different handling requirements between sprinting and general track work ? , might disconnect mine and see what it's like .

 

I wouldn't profess to be an expert on this and as I said earlier ten people with give 10 different opinions . The great thing about these cars is that it's easy to experiment .

 

 

 

 

[NoLimits]

If you ping me an email I have a short PDF set up guide I give to customers which is doable at home with a tape measure.

 

It is likely to be identical to Richards set up as it has been to other competitive sprinters in the past.

 

Most of us find ourselves in or around the same numbers

[Richard Price]

Quoting Mark W: 

I don't think that the original post actually stipulated CR500 for the 13 inch

It didn't, but the 175/55-13 front size does suggest CR500's as no other common tyre is fitted in that size.

Quoting Mark W: 

As far as sump clearance is concerned I do about 3000 road miles a year and have never had a problem with ride height ( on CR500s ) , yes it is lowish but I don't seem to be collecting any scrape marks on the sump ,the only issue I have seen is with speed humps where the gearbox can catch if the ramp angles are steep .

Personally, I'd choose to be cautious when recommending ride heights. If the OP is running standard 150lbs/in springs, a low ride height, AND plans on carrying a passenger on the road, then I would be very cautious about running parallel wishbones and 175/55 CR500's.

I have a broken sump to prove that its not that safe ☹️ 😔

 

Quoting Mark W: 

interesting to see you don't run a rear ARB , maybe that's to do with the different handling requirements between sprinting and general track work ?

On the hills, traction away from the start, and out of slow corners is everything!

 

 

 

 

[pandjack]

Many thanks for the prompt responses guys

 

To clarify - yes - the 13" wheels are pre-shod with CR500's (came as a too-good-to-be-missed-at-that-price extra when I acquired the car towards the end of last year) & taking Richards point about them not being the ideal choice for the hill - It'd be a shame not to 'use them up' before re-shodding with some wider,stickier rubber.

 

Regarding ground clearance for road use I may well stick the 15's back on if things start to look sump threatening!!

 

No limits : pinged you one earlier as suggested - cheers.

 

Any thoughts on corner weight ratios?

 

 

 

[Richard Price]

Quoting pandjack: 

Any thoughts on corner weight ratios?

 

I normally set equal weights across the front axle with the driver normally seated.

 

 

[pandjack]

No limits - many thanks for the info - just the job

[Rockape]

re Horizontal wishbones, is that laden or with the car empty?

Brian

[Mark w]

Brian ,

I set mine horizontal unladen BUT as stated above it would seem that others have had problems with sump clearance so please make sure that you are happy with your ride height .

 

I have done nearly 20,000 miles without an issue , others seem to have had less luck .

[Pendennis]

For competition use, low as you can go is the way to go and don't worry about horizontal bottom wishbone Also, the least rake you can get away with the better. I set my competition car diagonally, which almost probably means reduced front spring coil winding 😬