18" v 19" v 20" tyre sticky patch size difference?

[Milton477]

I have stuck with standard 19" wheels but have, depending on opinion upgraded to Cooper Xenons.



My D2 with 245/75/16s was unstoppable on the beach with tyres at 18psi & I am now wondering how much difference 18" Vs 19" wheels make on a D4 in the sand. I have measured the 19" contact patch to try to get a more accurate idea & I was wondering if someone out there with standard size 18s would do the same.

This is how I did it:



I started at 15psi then worked up to 37psi, pushing the 2 parallel rules in & measuring the gap. Results are as follows:

15 psi --> 275mm
18 psi --> 265mm
20 psi --> 255mm
25 psi --> 235mm
30 psi --> 220mm
37 psi --> 190mm

I have to say, there is not as much sidewall bulge in the Coopers at 18psi so seems like a safe starting point. I'd hate to get my permagrin stuck on the first beach outing.

[Aaron40]

I was talking to Landyandy about the patch between front and rear at the same pressure the rear seems to have a longer patch obviously heavier when car is empty. For beach work it's nice to have the patches similar so the car doesn't crab... I have GG's and I like them low around the 15psi mark on soft sand on the 19 inch rims but they don't float like my 265/75r16s in my D2 Td5.....

[Slunnie]

I had heard recommendations of deflating to a footprint length rather than pressures.

[Babs]

That low profile looks scary

Looks like I better get used to it

Great thread, very helpful that info, cheers

Sent from my iPhone using Forum Runner

[Meken]

It's not just about the contact patch - part of the reason to deflate is to let the tyre deform and "roll" up over the soft sand rather than pushing it up in front.

[LandyAndy]

Milton.
I will edit the title to include 20" too,as its the other wheel size with slightly better tyre offerings than the 19".Hopefully we get your post matched in 18" and 20" and different tyre size/profiles.Get to it people,see how many combinations we can compare,even similar size,different brands would be interesting.Will try to find time to do a Cooper AT3 265/60R18 over the weekend.
Thanks
Andrew

[LandyAndy]

That low profile looks scary

Looks like I better get used to it

Great thread, very helpful that info, cheers

Sent from my iPhone using Forum Runner

Scarry 15psi in very soft powdery WA sand!!!!!


Andrew

[Bytemrk]

Nice work Milton

Personally other than extremely soft sand, there is no way I'd take my 19"s down to 15...

Going down to 20psi gives you a very significant increase and with such a low profile, much less starts to get into dangerous territory in my view. Particularly with a well loaded vehicle.

[scarry]

Scarry 15psi in very soft powdery WA sand!!!!!


Andrew

No not guilty,i can't afford one of those flashy new models

As for my old hat poverty pack tyre size,i never seem to have any issues.

[LandyAndy]

Nice work Milton

Personally other than extremely soft sand, there is no way I'd take my 19"s down to 15...

Going down to 20psi gives you a very significant increase and with such a low profile, much less starts to get into dangerous territory in my view. Particularly with a well loaded vehicle.

At that place,Horrocks Beach,20psi was no good,they just couldnt get up on top of the soft sand,once we did,magic.Very hard to get them to move from a stand still.

Andrew