Ride height

[Steve W]

I’ve been thinking about raising the rear ride height on my car by a few mm as a test to see if this reduces the understeer. I’ve heard from a couple of people that a rake of around 15mm is a reasonable starting point. I’ve measured this from the floor just in front of the rear wheel and from the lowest point just behind the front wishbone. I found the rake was actually 20mm

Now with the not so superlite driver in place this changes to only 10mm 🙆🏻

So is 15mm rake a good staring point and should this be loaded or not ?

 

[scooby dooby doo]

it should be measured laden. i think i've heard 15mm as recommended as well.

 

you'll need to check the corner weights again after this as well.

 

HOOPY R706KGU CYCLE WINGS AEROSCREEN K SERIES CUCUMBER

[Peter Carmichael]

The overall rake of the car is not that important, so the 15mm figure is spurious. It is much more important that the angle of dangle of the radius arms is appropriate.

 

If you change the ride height by 5mm, the change over the length of the car is a very small angle. The change of the same 5mm over the length of the radius arms gives a much larger change in angle. The angle of the radius arms controls rear steer effects, so any rake of the car effect is swamped by the radius arms effect. Equally, if you adjust the front by 5mm and the rear by 5mm you have the same rake on the car but the angle of the radius arms has changed. This is why the rake of the car is spurious.

 

Just try moving the platforms two turns and if the car feels like it wants to swap ends, back down by a turn. Feedback from real world drivign tells you the right settings, not some made up figure in a book or on a website.

[scooby dooby doo]

is the chassis not accurately made enough for rake (as opposed to radius arm angle) to be a valid measurement then 🤔 (honest question there - not being argumentative)

 

i agree that its better to measure the actual thing you are intested in (radius arms) instead of something that in some way depends on it. however, rake is easier to measure. and 15mm exists as a ball park sanity figure.

 

agree totally that the "change it, try it" way is the best. OTOH its not always possibly to test the understeer characteristics on the open road ❗

 

HOOPY R706KGU CYCLE WINGS AEROSCREEN K SERIES CUCUMBER

[Peter Carmichael]

Hoopy,

 

Read what I have written. It is all in there already:

 

If you change the ride height by 5mm, the change over the length of the car is a very small angle. The change of the same 5mm over the length of the radius arms gives a much larger change in angle. The angle of the radius arms controls rear steer effects, so any rake of the car effect is swamped by the radius arms effect. Equally, if you adjust the front by 5mm and the rear by 5mm you have the same rake on the car but the angle of the radius arms has changed. This is why the rake of the car is spurious.

---

[Steve W]

Thanks for the replies. Just wanted to know I was in the ballpark (with the front wishbones level).

Will just try a couple of turns and see how it feels. This is all because of an 'introduction to sprinting' day a curborough. Getting faster and faster during the day, finding the limits of the car (and well over them). Might just have to try a couple of the club sprints next year 😬

[scooby dooby doo]

hmmm... i missed the "if you raise both ends.." bit. very odd. but the rake measurement usually comes with a "set the front ride height to xxx" disclaimer. which i can't remember.

 

ah heck, must drink more coffee at work....

 

HOOPY R706KGU CYCLE WINGS AEROSCREEN K SERIES CUCUMBER