Suspension rebound following wheel size change

[marcusjames]

I have changed wheels from 15” to 18” in an attempt to improve grip and reduce lean. I am hugely surprised by the immediate change and now curious.

Stationary and pushing down the front winch bar, the car used to dip significantly (felt like 50cm). Now the car won’t dip at all. I’ve only changed the wheels and not yet touched suspension. Could this be the camber needing adjustment or some quirk with the wishbone angle now sitting lower.

I hope that makes some form of sense.

[phil4]

Just a question...

You’ve changed from 15” to 18” wheels.... but what actual change in diameter has occurred?

I ask his as I’ve a set of 15s running mud tyres and a set of 18s running geolanders. Theres not a lot of difference in the diameters from what I can see.


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[marcusjames]

The 15” had geolanders and the 18” have A052 235/40.

[phil4]

Yup, but what’s the difference in diameter?


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[marcusjames]

15” with 75 geolanders and then to 18” with 40. I calculate this to be both at around 21” diameter.

[phil4]

Cool, I’m which case I doubt they’ve changed your suspension.

Instead I’d guess at things like tyre pressure and sidewalk stiffness.

The geolanders you had may well have been run at lower pressures and with more sidewall give, especially with 75 profile sidewalls.

The new street tyres are likely to run at higher pressure and with less sidewall, probably stiffer too... will have much less give.

Since the suspension settings isn’t a numbers game with a right answer try adjusting it but by bit until it feels right to you.


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