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.

http://www.aulro.com/afvb/attachment.php?attachmentid=111418&stc=1&d=1468566239

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:

http://www.aulro.com/afvb/attachment.php?attachmentid=111420&stc=1&d=1468566668

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 :o

Looks like I better get used to it :)

Great thread, very helpful that info, cheers :D

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[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 :o

Looks like I better get used to it :)

Great thread, very helpful that info, cheers :D

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

https://www.aulro.com/afvb/images/imported/2016/07/726.jpg (http://s113.photobucket.com/user/LandyAndy_2006/media/20160107_160650_zpsmrfuvi7g.jpg.html)
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!!!!!

https://www.aulro.com/afvb/images/imported/2016/07/726.jpg (http://s113.photobucket.com/user/LandyAndy_2006/media/20160107_160650_zpsmrfuvi7g.jpg.html)
Andrew

No not guilty,i can't afford one of those flashy new models:D;)

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.
https://www.aulro.com/afvb/images/imported/2016/07/724.jpg (http://s113.photobucket.com/user/LandyAndy_2006/media/20160107_160716_zpstvychlvm.jpg.html)
Andrew

[Tombie]

Signature lights at opposite phase in the pic. Looks good!

[LandyAndy]

Signature lights at opposite phase in the pic. Looks good!

You cant pic it by eye but they flicker.Pics taken on a tablet,when you are framing the pic the sig lights show flashing.Note how both vehicles have different bits of the sig lights showing.
Andrew

[Bytemrk]

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.
https://www.aulro.com/afvb/images/imported/2016/07/724.jpg (http://s113.photobucket.com/user/LandyAndy_2006/media/20160107_160716_zpstvychlvm.jpg.html)
Andrew

Andy, not saying I wouldn't go to 15 in really soft sand if needed - I would...

I just wouldn't race down past 20 unless there was a damn good reason...;)

Looks like fun:D

[KONDO]

Just installed the Compu 18" rims with 285 60R 18 on the D4 (2013) and loving it! :)

[Tombie]

You cant pic it by eye but they flicker.Pics taken on a tablet,when you are framing the pic the sig lights show flashing.Note how both vehicles have different bits of the sig lights showing.

Andrew



I know they do... It's PWM for thermal management.

[Grentarc]

I know they do... It's PWM for thermal management.

And PWM also for dimming once headlights are on etc

[Milton477]

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

Thanks Andrew. I wondered where the 20" came from. The additional size would be useful.

I read somewhere that the OEM wheels hold onto the bead much tighter than after market varieties. If this is true, lower pressures should not pop the bead quite so easily.

[Bytemrk]

Thanks Andrew. I wondered where the 20" came from. The additional size would be useful.


Current model D4's come from factory with either 19" or 20" rims.

[Babs]

Scarry:):):):):):):) 15psi in very soft powdery WA sand!!!!! Andrew

Hard to tell from pic but they don't look like they're bagging out :)

15 is low for an already low profile.

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[Tombie]

Hard to tell from pic but they don't look like they're bagging out :)

15 is low for an already low profile.

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You don't want them bagging out. You want a longer not wider footprint.

[Babs]

You don't want them bagging out. You want a longer not wider footprint.

Sorry, I meant that in a positive way, they don't look like they're bagging out as a good thing. :)

What tyres?

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[Lukeis]

Wheels look great kondo 👌

But why show the white writing on the tyres, I would have them turned inwards!

[LandyAndy]

Wheels look great kondo 👌

But why show the white writing on the tyres, I would have them turned inwards!

Then people would only be able to read them after you ran them over:):):):)
Andrew

[LandyAndy]

Current model D4's come from factory with either 19" or 20" rims.

He is refering to his title.I added 20" and asked some 20" owners to get some measurements too;);););););););)
Andrew

[Aaron40]

I only have experience with 265/75r16 on the D2 and 255/55r19 GG's on my new D4 and even at low pressures of around 15 psi the tyre as Andrew said does not want to float like the larger 16s (Toyo MT) did they break through the soft sand and plough....with sand moving through the rim... I would happily take pressures even lower on WA's soft sand, I have seen Gordon's posts talking about 12 psi and lower... they are better with momentum but very plough like at slow speed and take offs... problem is as soon as you come to any limestone you have to air up... I am hoping to get 18's soon and most accounts seem to suggest that they help in the soft stuff. Gordon recommended 285/60r18 Zeons or similar for very soft sand use although I like the 647 as well...

[LandyAndy]

Here are my measurements.Cooper AT3,265/60R18,cold.

15psi 290mm
18psi 265mm
20psi 255mm
25psi 235mm
30psi 210mm
37psi 185mm

Pic at 18psi and then 15psi.
https://www.aulro.com/afvb/images/imported/2016/07/695.jpg (http://s113.photobucket.com/user/LandyAndy_2006/media/Mobile%20Uploads/2016-07/20160716_100646_zpspfjtv1i3.jpg.html)

https://www.aulro.com/afvb/images/imported/2016/07/696.jpg (http://s113.photobucket.com/user/LandyAndy_2006/media/Mobile%20Uploads/2016-07/20160716_100912_zpsksyzj7vb.jpg.html)

After doing this experiment Im much happier with the 18" tyres.20psi should be good on beaches,then there is plenty more deflation available at 15psi.Much more sidewall height than the OEM 19" Wranglers at 15psi.

Andrew

[Russrobe]

At 18psi there's barely any bulge in the 285 60 18s. So little in fact that i was tempted to just drive home to pump mine up last weekend! Interesting to see how they go with an extra 500kgs of cargo though.

[Milton477]

Thanks Andrew. I guess the myth about 18s being so much better on the beach than 19s just got busted based on the contact patch size. I will concede that the 18s will have a wider patch by 10mm though. Probably should have worked out the square meter size to get a true comparison. It will be interesting to see if someone with 20s comes to the party.

I'm sorry I did not do the same measurements with my D2 before I sold it so if someone reading this feels like it - please. The D2 just did the sand so well. Was not a problem stopping & then pulling away on the soft off ramp to the beach at Bribie, Straddie or Rainbow Beach.

[Tombie]

Need to wash those wheels Andy. All the brake dust has made them look Grey.. [emoji6][emoji48]

[LandyAndy]

Need to wash those wheels Andy. All the brake dust has made them look Grey.. [emoji6][emoji48]

They are Grey BFG;);););););)
They are early build GOE wheels,seen a few sets now that arent so glossy,especially black ones.The later grey ones are a different shade too.
Yet to polish them;);););););)
Andrew

[phl]

I read somewhere that the OEM wheels hold onto the bead much tighter than after market varieties. If this is true, lower pressures should not pop the bead quite so easily.

That they do; seems to be built-in bead lockers on the rim. When I had my tyres changed, because I was watching, the chap doing it warned me that the seating of the bead is pretty explosive... and it was! Just as well I was warned, or I'd have thought he busted the rim.

[catch-22]

I mucked up yesterday. In haste, I didn't lower my tyre pressures thinking the sand wasn't that soft. Man was I wrong. Had it in sand mode and suspension high, but did NOT turn off traction control. Tyres were well in the sand. So I got the maxtrax out and used them for the first time. It wasn't until I was having a beer with a mate last night that I realised I didn't turn traction control off. Tyres down to 18 made no difference.

I wish I could say this was the only time I'll ever do that again but with the rush of not being seen stuck by Toyota drivers and the risk of the tides, adrenalin kicks in and mucked with decision making..

I run 19s but physics is physics.....and stupidity can't be cured [emoji3]

[Tombie]

It's not Traction Control - It's DSC.

[catch-22]

Nope, good point. Turning it off should have helped though, right?

[Aaron40]

Nope, good point. Turning it off should have helped though, right?
yep.
Dynamic Stability Control (DSC) reduces engine power and applies ABS braking to individual wheels to help maintain control, should it detect a loss of lateral grip that could occur in a turn.
Turn it off when changing programs height etc, it will turn back on each time you change programs.

[PerthDisco]

I would happily take pressures even lower on WA's soft sand, I have seen Gordon's posts talking about 12 psi and lower... they are better with momentum but very plough like at slow speed and take offs... problem is as soon as you come to any limestone you have to air up...


Anyone in WA tried coming off the beach south of the Warren River up the big exit dune? Mt Calcalup I think. That needed 12 but got up easy once set up after a few tries. Getting launch speed was hard. Is a tricky step 3/4 way up. Was a big line up of bush bashers top and bottom.

[Russrobe]

Anyone in WA tried coming off the beach south of the Warren River up the big exit dune? Mt Calcalup I think. That needed 12 but got up easy once set up after a few tries. Getting launch speed was hard. Is a tricky step 3/4 way up. Was a big line up of bush bashers top and bottom.
Going to try this one around xmas if we can find someone to join us!

Think you mean Callcup though.

[Tombie]

Anyone in WA tried coming off the beach south of the Warren River up the big exit dune? Mt Calcalup I think. That needed 12 but got up easy once set up after a few tries. Getting launch speed was hard. Is a tricky step 3/4 way up. Was a big line up of bush bashers top and bottom.



That's where leaving ego at the door and helping one another is great for the environment and the vehicles...

Done this type of exit many a time, link the vehicles and help haul each other over. (Was needed at Robe many years ago)

[PerthDisco]

Going to try this one around xmas if we can find someone to join us!

Think you mean Callcup though.



In summer months can come in through Yeagarup Dunes and can cross the river mouth. Getting in at Yeagarup usually needs 18 or less. Make sure you drive down the face of the big powder dune to the right. Getting to the top is as much fun. You can actually drive all the way south on the beach to come out before Windy Harbour I believe. Have not checked that out.

The track a bit further north all the way to Black Point (Rock) is great also.

[Babs]

It's not Traction Control - It's DSC.


Ha ha ha :)

Tombie you should make that a sticky, that's not the first time you have written that and it definitely won't be the last :D

Cheers, Babs :D Sent from my iPhone using Forum Runner

[shanegtr]

I wish I had my D3 with me here to throw up a 17" rim for comparison as well

[Russrobe]

Will do the 285 60 18s when i get the car back... Will be interesting to see is people's perception of a thinner tyre being better is true.

I always thought the 285 might be a better match to the D4's weight, therefor allowing for more deflation without bulging or a better float so to speak. Only comparison i have is the LC200 which has the 285s from standard....

Assuming overall size has a bigger impact than rim diameter that is...

Definitely understand why people say a wider tyre creates more rolling resistance, but there has to be a crossover point somewhere for optimal deflation in sand..

[Tombie]

Apart from the usual there is another risk introduced with wider tyres.

The wider a tyre for a specified rim the more the increased risk of pinching a deflated tyre sidewalk between the ground and rim edge.

[Russrobe]

Apart from the usual there is another risk introduced with wider tyres.

The wider a tyre for a specified rim the more the increased risk of pinching a deflated tyre sidewalk between the ground and rim edge.
Hmmm even if the profile remains at 60%?

Suppose you wouldn't go anything above 285 without going to a 9.5" rim...