F3 ??? rear suspension

[retro_msport]

I'm toying with the idea of doing a double wishbone rear suspension on a saloon, leaf sprung RWD originally. Now to keep costs down I dont want to be fabricating uprights and wishbones if I can use off the shelf items. And in this respect the final drive will probably be a LSD equipped BMW item (apparently bullet proof).

Has anyone got any ideas of costs or links to where i can get second hand kit from?

The idea behind this is to provide a better suspension for the same sort of costs of an Salisbury LSD Atlas axle and 6 links

An idea of weights and power .... weight around 1000kg with 60/40 split (atlas equipped) power 425-450 Bhp and around the same Torque, 10-12" wide rear wheels

[Suze]

look at some LMP1/LMP900 cars they are 900+ kg and have the sort of thing you are looking at.

The cost is gonna be pretty high though as I don't think F3 wishbones would be up to it - plus they damage a lot easier

[ian_w]

Sounds like you are into some serious fabrication to mount the diff and make pick-up points for the suspension. If you are confident of being able to do this then making some custom wishbones must be a walk in the park for you.

As far as uprights goes, can you use something off a production car that already has a similar suspension system? Going to be much cheaper and easier to find than some bespoke racing parts.

[Goran Malmberg]

Looks like a tricky question, just a few thoughts. Many of these suspension parts are for pushrod coilover activation. Also, they probabley wont match the front suspension geometry.

Goran Malmberg

[retro_msport]

Ian,

To make parts that can be bought normally works out more expensive than buying parts...theres the jigging and design etc, thats why i want to buy off the shelf parts for the bolt on bits, the shells will all need modding so thats an un-avoidable cost. But with the cost of a fully floating Atlas around £4,000 unfitted, then you have the shell mods for the 6 link etc ... thats a lot of fabrication time if the parts can come in under £1000.

Goran,

The standard suspension on Escorts is not the best and even with a Standard (gp4 rally car parts) 6 link fitted there is still around 300mm difference between roll centers. On my cars i can get this down to 100mm, and back up to 300mm. Also the 4 link is multi adjustable for toeing the axle in roll (both in, zero steer and out) and also squat/neutral/anti-squat, with ride heights ranging from 120mm under the chassis rails to 45mm ride height with 40mm of bump when using a 22 inch tyre.

This venture is just furthering the Mk1 and 2 Escorts development, I allready have a double wishbone front suspension on paper, just need to make it bolt in for ease of fitting. Mounting the bell cranks/ push/ pull rods isnt a problem, doing it all for the same price as my 6 link rear is ?????

Suze,

Lm .. sounds pricey, the F3 has wings so probably weighs in at twice if not more than the Escorts. As for damage, probably less as the Escort has wheel shrouds whereas the single seaters can lock wheels. Think i'll have to have a chat with Steve Greenald though..as hes just mapped a couple of LM cars, maybe I can get a looksie

[trikesrule]

Just wondering about what goran suggested 'new rear suspension not fitting or suiting the front. I reckon he's spot on there. The first thing I would be looking at is the rear roll centre height. You need to work this out so you have an idea of what parts to source on the cheap.......trikes

[retro_msport]

The roll centers is one thing of the reasons for doing this. Also there is a growing number of enquires about fitting the Ford Sierra rear beam,,, and that is a non starter, horrible camber change, the roll centers not particully matched with the front of an Escort, the weight of the Sierra kit. And the diff units are a bit weak.

Ideally i would be looking at un-equal length and converging wishbones on the doner chassis, but the 2 main advantage to going double wishbones is.
(1)the toe and camber adjustment, At the moment theres only so much tweeking a live axle can take.
(2) the unsprung weight

And again, the front roll center can be sorted with the double wishbone suspension thats on the back of a ciggarette packet at the moment.

Just another thought on roll skew... with a high rear and low front rollcenter we have a rear wheel lifting on corner entry, and a front inside wheel lifting on corner exit, now if the skew was reversed, would that mean the reverse would happen or would braking force cancel out the lift??

[phoenix]

Have you considered uprights and wishbones from a mid-engined kit-car, such as a GT40 replica or maybe and Ultima?

[retro_msport]

Originally Posted by phoenix

Have you considered uprights and wishbones from a mid-engined kit-car, such as a GT40 replica or maybe and Ultima?

Yep.... From Ultima £1794.23 . but it uses bushes, would really like rod ends.

[retro_msport]

Has no one got an idea of what second hand F3 suspension parts cost then.. i've hunted around the sites that I know of, and I can find bodywork, tubs, etc but no rear suspensions, someone must be selling bits.

[StephenRae]

I think you are going in the wrong direction looking at F3 rear suspension stuff. It was designed with completely different parameters such as tucking the uprights out of the air stream and minimising disruption of airflow. From what I have seen single seater suspension is only just up to the job it was meant for with little concern for durability.

[JamesH]

Take a look at some of the indi rear suspension from things like Westfield and some of the home-built IRS Locosts (Or the MK Indy). Generally use a Sierra diff with Sierra hubs, but since you will be making you own drive shafts, you can change that for the beamer diff.

www.mkengineering.co.uk
www.mksportscars.co.uk/indy.htm
www.gtstuning.co.uk

IRS on a Locost costs about £300 or so in bits from MK Sportscars I think.

[retro_msport]

Stephen, F3 , F anything ... i just need to find some light weight componants that are easily avalible, the F3 gear has some huge loadings on it.

Go back a few years and think of F5000 chassis with various bodies on top.. The Special Saloons Beetle springs to mind.
Also bear in mind most Escorts have a heavy live axle hanging off 6 pieces of ERW tube and 6 3/8's bolts.

James, I did look at a few Caterfields. But i've also seen a few failures on the wishbones, And Sierra Hubs weigh a fair bit.

All i'm looking at, for the moment, is a ballpark figure, someone must have damaged their rear and bought replacements.

[StephenRae]

My F3 experience was in the eighties when they hadn't got round to laminates, upper rear rockers were pretty substantial but lower wishbones would be perhaps 18-20 gauge oval steel tube which you could practically bend over your knee! when pushrods were adopted the top wishbones were the same. Previously F5000 and the like were pretty robust and able to cope with a bit of extra weight. Pricewise an F3 wishbone new about £200 and an upright about £500 each.
I have just fitted cast alloy front uprights to my Reynard, made by a fellow competitor £500 the pair complete with bearings etc. They may suit your purpose they are a lovely piece of kit and could easily be adapted for driveshafts

[retro_msport]

Cheers for that Stephen..

I'm trying to juggle the price between doing a 2-Piece shaft+LSD / Fully Floating Atlas (around £2000 - £4000) and the fabrication cost of fitting it to an Escort and this wishbone idea ... If the cost are comparable then its a go'er. Theres a fair amount of Fabrication on the Escorts for the 6 links i do and yes there would be more for the wishbones but i think (know) the results will be worth it.

[crogthomas]

Road car parts might be you're best bet if you're looking for a inexpensive, robust setup. There must be something out there that has RWD, double wishbones and all mounted to a subframe of some sort that you can just use whole?
Some ideas that spring (pun intended) to mind, but have no idea if they are actually of this arangment, are:
Nissan 200SX
Mazda MX5
Lexus LS400

Worth a look?

[retro_msport]

I keep on thinking about road car stuff, but its normally heavy,, un-adjustable
and packaged to fit under bums etc. I'm going to throw the F3 prices at the customer and see what he thinks..

[sereneseven]

If I were you I would look into a stouter set-up than formula suspensions designed around 1500LBS and less....I would contact people such as picchio or Doran and others of the like. there are a ton of old srp2 cars floating about. I think you will run into major reliability issues trying to over work flimsy formula suspension.