Handeling Thread

[Guest Terry]

I am hoping that this thread will act as a database for those seeking advice and direction on some on the basics of car handling.

 

Over the years since first Racing in the British Formula Ford series back in 60s I have been asked by many people to advise on setting their car up. What I have discovered is, most cars including the 7 are “over sprung & under damped”.

 

The Basics

 

The spring needs to control the ride hide and the damper needs to control the spring.

 

If any one has driven a modern Caterham with the latest Nitron damper set up, you will have noted how soft the car is. No1 mistake, most Caterhams are WAY to hard.

 

Regarding 7’s my experience is limited to the Lotus 7 & Caterham. As a rule of thumb on a S5 SV Caterham it should have a least 5 inches of front end suspension travel. Put your hands on the inside edge of the top wishbones and push, if set up correctly it should have 5 inches of travel, 2.5 in each direction.

 

Hopefully we can get multiple posts on this thread in order that we can all learn from each other.

 

Remember “body role is not the enemy of grip”

 

Post what you've learned

[bigdog]

You mean that the rock hard "developed at the ring" ride advertizing hype by auto makers is bollocks?:jester:

 

I learned a long time ago via sport & dirt bikes that you need the suspension to soak up the bumps so that your tires follow the road and don't lose contact.

 

As I'm new to sevens, I look forward to gleaning a little helpful info from this thread.

[lancylad]

Looking forward to following this thread, mine will need setting

up this spring.

[James A]

There is no right answer here, how you set a car up is based on how the car is used and where it is used. Street only, track only, mixed use, autocross, lots of variation here. And then couple that with the nature of the track surface and there is a lot of variation in how a car should be set up.

[HOTTTCAR]

Niki Lauda's book The art and Technicalities of Grand Prix Driving is full the set up info you may be looking for. Its an enjoyabe read and easy to understand. He was and still is great at set up.

Gale

[AndyB]

Unfortunately I will be doing all the learning as ALL I have is my experience with my ancient Caterham.

First my car specs;

76 Caterham basically a series 3

When all is well, close to 140 hp through an RS2000 4 speed gearbox and live axle.

Adjustable Spax coil overs on the softest setting on a stock coil I believe.

195-50-15 Dunlop Direzza Z1 200 tread wear.

I reference most of my experience to autoxing charity event I've done for the last 3 years. Unlike competition on this day it's easy to do 20 or more runs if your car is popular with the donating read paying public. With this many runs you can start to focus totally on your driving and the cars reactions.

My biggest challenge is a figure 8 or double 360, 1 in each direction. Also there are 2 single 360's parts of these become off camber. I try to time my braking so I'm off the brakes as I'm turning in to move the weight to the front wheels. This works well for the 1st 180º but to maintain momentum you are back into the gas and that's when the front starts to wash out. Dropping the front pressure to 15 lbs has helped but not alleviated the problem. As this is not a timed event I mash the gas to keep the front steering in the correct direction which thrills the other occupant but I'm sure does nothing to improve on time.

Any thoughts as to how I can get more grip into the fronts?

[nick47]

Getting off the brakes moves weight to the rear wheels, not the front. Sometimes a tap on the front brakes can get you a little more front end grip, or just trail-brake all the way in. Definitely stomping on the gas will unload the fronts, and you'd like to have most of your turning done before that.

 

If you're in the middle of one of the eights and still understeering, the classic fix is lower front spring rates or stiffer rear.

 

In autocross you're in transition most of the time, so you can make big changes through shock adjustments. There are some rules of thumb but it's mostly trial and error depending on the car and the course.

[AndyB]

Getting off the brakes moves weight to the rear wheels, not the front. Sometimes a tap on the front brakes can get you a little more front end grip, or just trail-brake all the way in. Definitely stomping on the gas will unload the fronts, and you'd like to have most of your turning done before that.

 

If you're in the middle of one of the eights and still understeering, the classic fix is lower front spring rates or stiffer rear.

 

In autocross you're in transition most of the time, so you can make big changes through shock adjustments. There are some rules of thumb but it's mostly trial and error depending on the car and the course.

 

Surely braking loads the front wheels but you have to come off the brakes as you start to turn otherwise you are asking the front wheels to do double duty.

And getting on the gas hard is to step the rear out and therefore keep the fronts tight to the turn. Like I said not the fastest but effective.

[Guest Terry]

Sounds like we are getting into already. As stated there is no perfect set up because the application changes, there are however some basic rules that dont change.

 

When running slicks on a Hayabusa Powered Caterham we have removed the front role bar which allows the car to role and the same time we drop the front end.

[JohnK]

My experience is that most folk (including myself, at times) are looking for a 'magic bullet'. A single fix that going to make their car handle wonderfully in one fell swoop. There just ain't no such animal. Enlightenment isn't that easy to achieve, if it actually is ever achieved. The pursuit is not for the timid. The Lotus 7 and today's Caterhams deliver handling that is magical – just ask the Porsche and Ferrari drivers that can't keep up with one on 'name-your-track'. This did not come about by accident. It involves a huge amount of study, experience, insight and experimentation. Learning what this stuff is all about is a great opportunity to acquire humility.

 

For starters, see my recent post

http://usa7s.com/vb/showthread.php?t=9238&page=2

and spend some time pondering the link that's attached to that post.

You might also find things of value in my extended (or extremely tedious) post, Ithaca Lemonade.

 

Here are a collection of resources which, along with a fanatical desire to make some sense of what is going on when your car is going 'round a corner with both ends broken free, will get you a glimpse of what 'handling' is all about.

-Competition Car Suspension by Allan Staniforth is a delightful read, and what he summarizes so nicely will deliver insights for years into the future. (Great pictures, too)

-Racing and Sports Car Chassis Design by Michael Costin and David Phipps is a classic and should be on your bookshelf - and read carefully.

-Race Car Vehicle Dynamics by William F. Milliken and Douglas L. Milliken (father and son, I believe), the nearest thing to a Bible in this field, is stuffed with golden truths, but at a price.

-Carroll Smith's collection of "_____ to Win" books is a a treasure and one of them has the punch line in it - and here it is, but it will take you years before you get to the point where you can think to yourself "Yes! that is indeed exactly what is going on! I understand now!"

From "Tune to WIn". page 54: ...While it is possible to control wheel camber either during vertical movement or during chassis roll, it is not possible to achieve very good camber control under the combined conditions --- we have an "either --or" situation. ...

Staniforth says the same thing, but in more accessible/less rigorous language.

 

If you're really, really serious, buy Wm. Mitchell's WinGeo3 suspension software and the companion book by his friend Rowley's book, Race Car Engineering, which comes with analysis software that allows you to see the data that Mitchell's software allows you to collect and organize in dynamic circumstances. (http://www.mitchellsoftware.com/) … no relationship, financial or otherwise, of any kind here.

(Unhappily I found out that Bill Mitchell died January of 2014. I am one among many who are saddened by the industry's loss of his contribution to the sport. As of april 2015 I haven't found if anyone is taking responsibility for distributing his product. See http://www.apexspeed.com/forums/showthread.php?t=61960 for an explanation of his passing. )

Figure the program out (it is NOT a polished finished piece of software and involves comprehending LOTS of critical definitions) and then spend, perhaps a week, maybe two, measuring your car (I did it three times, and I'm still not completely happy with the results) and when you start playing with the results you'll see what the limits are of your measurements and why NASCAR and F1 teams spend tens of thousands of dollars on things like Romer Arms to get suspension link and ball joint postions to the nearest 'thou (not to mention chassis centerline and suspension pickup locations.) All in all, the many, many days I spent learning the software and learning how to ACCURATELY measure my car, paid off handsomely and has been and continures to be well worth the effort and cost. (And makes me realize how much simpler it would have been just to by a Caterham, not fiddling a bit with it, and just enjoy driving the damn thing in blissful ignorance :-) ...

Edited April 25, 2015 by JohnK
passing of Bill Mitchell

[Kitcat]

A while back an auto-X friend really stiffened up the suspension of his track only Datsun. At his first auto-x, with all the suspension mush gone, he turned into a sharp right hander, the suspension "went solid" since there was no compliance, and over he went, upside down, just like that. Didn't hit a curb, didn't do anything other than run slicks with tons of grip.

[coffee break]

A while back an auto-X friend really stiffened up the suspension of his track only Datsun. At his first auto-x, with all the suspension mush gone, he turned into a sharp right hander, the suspension "went solid" since there was no compliance, and over he went, upside down, just like that. Didn't hit a curb, didn't do anything other than run slicks with tons of grip.

 

How many cones did he take out? :conehead::conehead::conehead:

[xcarguy]

A while back an auto-X friend really stiffened up the suspension of his track only Datsun. At his first auto-x, with all the suspension mush gone, he turned into a sharp right hander, the suspension "went solid" since there was no compliance, and over he went, upside down, just like that. Didn't hit a curb, didn't do anything other than run slicks with tons of grip.

 

 

Any Video?

[coffee break]

How many cones did he take out? :conehead::conehead::conehead:

 

Yes, I'm a bit callous. I hope the damage was only to the Z.

[Kitcat]

No, but it is indelibly printed in my brain: I had done 2 auto-x's so far at that point and it happened at my corner. It seemed to happen in slow motion, up, up, up (no, no, no), then over. Fortunately this convertible had a roll over bar that easily passed the broomstick test.

 

It was terrifying (I thot auto-x was safe). The only instruction I had at that point was when to hold up a cone that was knocked over. They dont teach you what to do in case of a roll over. No one knew. We all just looked at the driver hanging upside down in his racing harness and had a lengthy debate while he yelled at us.

 

Anyhow, he was fine, the car was eventually repaired (and the suspension was seriously "softened" back up).

[Surfmonkey]

Good stuff John.

 

Thanks

[JohnK]

No, but it is indelibly printed in my brain: I had done 2 auto-x's so far at that point and it happened at my corner. It seemed to happen in slow motion, up, up, up (no, no, no), then over. Fortunately this convertible had a roll over bar that easily passed the broomstick test.

 

It was terrifying (I thot auto-x was safe). The only instruction I had at that point was when to hold up a cone that was knocked over. They dont teach you what to do in case of a roll over. No one knew. We all just looked at the driver hanging upside down in his racing harness and had a lengthy debate while he yelled at us.

 

Just so you guys know... When you work with this stuff you'll run into the term 'overturning force' or vector or whatever. Any vehicle whose center of gravity is above ground can be turned over, if the tires generate enough friction and the cornering force is sufficient. Think of the stunt car drivers of yore that would get old sedans balancing on their wheels (I think they used a ramp, but I've seen it done with no more than a quick yank on the steering wheel), or a wine glass unsuccessfully slid across a tablecloth. Even something as flat (really low CG) as a go-cart can go over, which is why their drivers are hanging way off the inside as they corner. Sidecars are a real study in physics here, as well as fun to watch the difference between the monkey's antics going from left to right hand corners. That's also the reason why LSDs are important - since you don't have very good traction when the rear inside wheel is waving in the air as the overturning force is lifting the car up onto its outside wheels. The guy in the Datsun (I'm guessing) had no idea what the results were going to be when he stiffened up the suspension and went to toss his car into the corner like he was used to. Isn't Science fun?

[HOTTTCAR]

John

The fact that a car with a lot of body roll is less likely to flip over than a car that stays flat in a corner is not intuitive to me. By stiffening up the suspension wouldn’t you get less traction on the outside if the weight was not allowed to shift more to the outside front wheel?

I thought that a measured amount of body roll would get you through the corner faster due to the increased traction on the outside front.

What am i missing.

Gale

[coffee break]

Physics lesson? :lurk:

[HOTTTCAR]

Physics lesson? :lurk:

 

yep ...got thru Quantum Mechanics in college physics but the dynamics of auto suspension is really really complex.

Gale