How to master chassis setup, from tires pressures to alignment

Staff
By Staff Writer
Feb 5, 2024 | tires, suspension, Chassis, Handling | Posted in Shop Work , Suspension & Handling | From the May 2022 issue | Never miss an article

Photography Credit: Chris Tropea

What can separate a fast car from a really fast car? Power? Driver skill? 

How about chassis setup? The way those adjustable bits and pieces are set up and aligned can often make a huge difference in lap times, driver confidence and even tire wear.

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Comments
Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand UltimaDork
11/12/22 11:11 a.m.

Good work consolidating these into one concise article. 

Bluebayou22
Bluebayou22 New Reader
11/12/22 4:23 p.m.

Most excellent.  Thank you.

MikesVettes8TY4SPD13GS6SPD
MikesVettes8TY4SPD13GS6SPD New Reader
9/4/23 7:07 a.m.

Excellent article.  Tire temps are important but also is full tire contact patch area using tire pressures and alignment.

My old method....using a tire grease chalk, scrub 3 lines across each tires tread face, 1/3 segments around the tire circumference, shoulder-to-shoulder, and using your steps, determine which pressure provides the best/most tire contact patch area.  This will also provide a good indicator if your camber angles need adjustment for full contact patch area.

Because of vehicle weight distribution, the various radii of track turns, number of left/right turns, and inclination, you should not be surprised by variations of pressures and camber angles per wheel position.

Just sayin',

latelifecrisis
latelifecrisis GRM+ Memberand New Reader
10/30/23 2:27 p.m.

Not many people have a skid pad available.  Can you just use a track for similar hot tire pressure testing?

Andy Hollis
Andy Hollis
10/31/23 12:35 p.m.
latelifecrisis said:

Not many people have a skid pad available.  Can you just use a track for similar hot tire pressure testing?

Yes, but its not nearly as easy/effective.

If you are are using pace (lap times) as a metric you need a super-consistent driver and car combo, so that execution isn't also being tested.

If using pyro readings as a metric, there is a cooling off period from when you come off track to when you can measure.  Further, there will be a varied amount of use of each corner depending on track layout.

The biggest challenge is to be certain that you aren't testing tire operating temp instead of pressure.  Most 200tw tires, for example, will heat soak at least to some degree fairly quickly.  So if you go out and do a couple of laps, come in change pressure and go out again, the tires are now in a different operating temp window and may perform differently.

That's the beauty of a skid pad: short laps, easy to drive at the limit, super consistent.

rhammond
rhammond None
11/4/23 8:53 p.m.

I am skeptical that toe-in at the rear decreases understeer and toe-out decreases oversteer. Consider the steering effect of the outside rear tire in the corner. Also, many new cars including Lotus, Toyota Camry, Honda Fit, BMW, etc. come with rear toe-in do you believe they intend to increase oversteer?  C R Hammond

rhammond
rhammond New Reader
2/6/24 6:54 p.m.

From Dixon, Tires, Suspension and Handling, 2nd Ed., p, 308: "A small static toe-in at the rear often has a surprisingly large effect on handling, increasiing understeer; front-wheel-drive vehicles, being lightly loaded at the rear and therefore having a large rear tire cornering stiffness coefficient, are especially sensitive to this."   C R Hammond

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