Setup for road use

[glasgow]

Have been reading about setup and  had useful conversation with Phil Reynolds. I am going to take the car to a motor engineering (kennith Brown) for setup. But i would like to make sure i have the correct information:

As far as I understand I should aim for the following:

- Rear arm of front wishbone should be parallel to the ground (ie, the white and red arrow distance in the pic should be the same.

- Distance measured from the front of rear arch to the ground (black arm) should be 15mm more than the white arm

- sump should be 80mm clear

All the above measurements should be taken with the car loaded (in my case, 2 persons and 1/2 tank)

I performed some measurements today (with no load in the car) and here they are:

Sump clearance: 90mm, White arrow 200mm, red arrow 190mm ie the rear arm of front wishbone are NOT parallel to the ground.

- Q1) Am I putting the measurement arrows at the correct points?

- Q2) I am going to change my tyres from 16" to 13" but can't get my head around how the rear arm of the front wishbone could be parallel to the ground while maintaining the sump clearance (going for 13" will make the red arrow even shorter and to get wishbone arm parallel, the white arrow would need to get shorter as well and therefore the sump clearance will become less than 80mm- correct me please if i am wrong)

- Q3) Regarding the toe: the assembly manual says 0.2 toe "in". But I read on many threads it is toe "out" not "in"...!!!!

- Q4) If the engineer is not keen to do the setup with the car loaded, should the above figures still apply or there should be different measurements for unloaded car?

- Q5) What about flat flooring? is corner weighting really something that I should try and get it done (not sure if the engineer will be doing it. and I am not capable of doing it myself)

Many thanks for your help

Ahmed

[SM25T]

You must do it with the equivalent of your weights in the car. Doesn't need to be real people. I used concrete blocks. The sump clearance is the important thing at the front. I didn't check if the lower wishbone was parallel to the ground. With 13" rims you will need a much taller profile tyre to get the same ride height. I don't know what this would be ..... it is a big step down from 16". There are tyre size/profile calculators on line.

[Jonathan Kay]

Are you committed to that engineer? It sounds to me as if you might be better off with someone who is playing with 7s day-in day-out...

Jonathan

[revilla]

Regarding Q3, a little bit of toe out will improve the car's willingness to turn in on track, however the flip side of this is that it will feel more unstable on uneven road surfaces. A little bit of toe in will sacrifice a little of the turn in for better stability on the road. As a compromise you can set zero (wheels parallel). So track cars would probably benefit from a little toe out, road cars toe in. It's up to you how you want it to handle. My car is road only, so I run a little toe in.

[martyn]

The sump height, and angle of the front wishbone are basically measuring the same thing. You cant change one without affecting the other. Specifying a measurement/parameter for both doesn't make sense because it will only be a huge coincidence if your wishbones actually are parallel at 80mm sump height. That will depend on many factors such as what wheel size and tyre profile you have. The actual depth of your sump etc..

It is a waste to go to an engineer and ask them to set the parameters you've already worked out. You can do that yourself one afternoon by simply turning the spring platforms. And anyway, how do you know your parameters are the correct ones for your type of driving?

Instead find someone who is experienced in setting up Caterhams and go to them. They'll ask you how and where you like to drive, and what sort of behavior you like from a car. Then they'll decide and set the best parameters for you personally. As Revilla points out above, almost everything in setup is a compromise; there are no right or wrong answers.

Anyway, there are other parameters you haven't mentioned that you certainly can't set at home.

• Toe
• Camber
• Caster
• Ride Height
• Corner weight - yes this should be included as part of the service.

[glasgow]

Thank you for your reply.

- Will go for R888R 13x60x185 front and 13x60x205 rear. this will reduce the height by 19mm

- wheels will be caterham apollo 6"  front and rear (hope it won't catch in the de dion at the rear)

- not too many options up north. Deardnaught garage does caterham service but long drive away and not specialised in alignment and setup. Kenny brown is a well known name for sport car setup in Glasgow but not specialized in Caterham 

- as for toe, car is only for road, but I need better handling in the corner as I find my current setup and tyres "interesting" at the corners.

- my other current  setting are: 

--- Rear hight (black arrow) 178mm (which is LOWER than the front, ie no nose down stance)

--- Didn't measure camber and Castor but from reading in the archive, i found  Camber: 1.2-1.4 -ve camber for front and 1.3-1.5 -ve camber for rear and 3-6 +ve castor 

 

- need to go to a building yard and buy some slabs and blocks ;-)

[glasgow]

And BTW, I never understood how the corner weight is being done. How you adjust the weight. My understanding is you adjust the height at the suspension but how would you change a weight of a corner?

[martyn]

Yes it is exactly that.. by changing the height of each corner.  By raising one corner up, you add more weight to that wheel, and it's diagonally opposite wheel.  Think about the analogy of a wonky 4 leg table, where 2 legs are longer than the other 2.  The two longest legs carry more of the tables weight than the others.  You can aim to have equal weight distribution on the front wheels, which gives good breaking performance, but might mean the car has a slightly different balance when turning left vs right (because the rear will be quite uneven).  Or you can aim to have the weight evenly distributed across the diagonal pairs of wheels.  This will give the same balance when turning in either direction, but will probably mean that one wheel will always lock first while breaking.

As you can see, setting the corner weight messes up the ride height at each corner.  This is why its not really useful to get too fixated on each corner of the car being a certain height off the ground.  Its all a compromise of optimum corner weight vs a balanced ride height all round.

[glasgow]

[Jonathan Kay]

I've often wondered if the term "corner weighting" causes confusion. Would it be better if we said something like "load distribution"?

Jonathan

[cr500dom]

Nope, you Caterham bods have already called it something else to confuse normal folk

Its always been corner weighting.

God knows where "Flat flooring" came from ?

Corner weighting is the correct engineering terminology.

In Racing terms each wheel and suspension system is classed as a "Corner"

You are measuring how much mass is being carried by each wheel (Corner)

 It is nothing to do with the floor

[ScottR400D]

Except that if you don't have the car on a flat floor, the corner weighting is pointless.

The term flat floor simply refers to what the car is sat on, but covers anything from a flat, horizontal floor to 4 separate scale mounts, set to exactly the same height as each other.

 

[martyn]

"Flat floor" I believe refers to the flat workshop floor that is needed to perform any kind of geometry adjustment or corner weighting.  People have mistakenly started using that term believing it refers to making the floor of the car flat.  Which obviously is never the goal.

To me getting a car "flat floored" refers to the entire geometry setup and corner weighting process because you put the car on the flat floor to do it. Its not correct to say "flat floor" is another name for "corner weighting". 

But you're right, I dont like that term at all, and just prefer not to give it a name.

Edit..   Beat me to it Scott!

[glasgow]

So, back to the main topic. did I get this right:

 

I need to sort the toe, camber, caster and 80 mm sump clearance. Then EITHER, 15mm rake higher rear OR corner weighting because I can't have both rake and corner weighting same time-correct? Anything else?

[David Brown]

Ahmed, I think we should get together and I'll help you sort it out. It isn't rocket science compared with what you do every day. A waste of time doing anything (beyond ensuring the height adjusters move) before you get your new wheels and tyres. Presume the floor in your new garage is flat, if so it'll do fine.

David

[martyn]

Yes you can set both rake and corner weighting correctly. A car could have so much rake that the rear is 2 feet off the ground, yet still be corner weighted for perfect front distribution or cross distribution.

Rake is used to control handling balance front to rear. It does this by raising or lowering the rear centre of mass and rear roll centre relative to the front.  It can also make small adjustments to the weight distribution front to back.

I wouldn't worry too much about what needs to be set or what values to set to. Discuss your driving with a setup specialist and they'll tell you the best values they've chosen for you personally. If you do want to do it yourself with the Caterham recommended values then all the instructions are in the Assembly Guide.

[glasgow]

Thank you, David. Yes, garage has flat floor and corner weighted . Tried to do a test with 2 screw drivers to move the height adjusters after soaking them with gas plus but they didn't move. I may need to jack the car up as Ian suggested.

 

[nickh7]

Not sure you'll get 80mm on he sump and the other measurements you stated . I've just fitted New dampers and with 150mm from chassis to floor I got 70mm under the sump. I fear it will be too low but I've no more turns on the dampers . 

[glasgow]

What car and tyres is yours Nick. Mine is SV 2003 roadsport. I currently have 90mm sump clearance on 16x45x205 and "I think" I can see about may be 20mm tread on the dampers. Mt dampers is the standard Caterham ones. With 13x60x185 i will loose 19mm in the ride height but hopefully i could adjust the dampers to compensate for the loss. 

 

[nickh7]

Hi, 97 1600 k wide track 14" 185 60s . Just fitted Nitrons street series. Bottom wishbones are level and I've got 20mm rake back to front . Ride on the shocking roads in west Yorks is very good and much more controlled 

[Bizzielizzie13]

 

Hummmm, does the 'Floor' here mean the ground the car is on, surely you are unable to 'Corner Weight' unless the car is... on a flat floor?

[ScottR400D]

Yes it does, as said earlier. The point is to get the bottom of each tyre at exactly the same height, more correctly the platform of each scale at the same height. 

IME garage floors often have a slight fall towards the door so I would carefully check that it's level in both directions before I just went ahead and set corner weights that way. 

As an example, if your garage floor sloped by 10mm across the wheelbase of your 7 you could end up with perhaps twice the rake that is recommended and too much weight on the front.

If you don't have a perfectly flat floor, corner weighting will be a waste of time. 

[ScottR400D]

 I calculated 22mm drop in ride height and 7.5% speedo overread from those figures. Seems a lot but, of course, a 7 should run on those tyres.