Different tyre pressures on toyo/kumho/yoko??

[speedmachine]

Hi guys,

On my new 3.5 I ordered some R888r because the old R888 worked pretty good on my previous atom 2.

But these tyres don’t work at all on track, no trust, feels like driving on eggs.
Now I’ve read that the kumho’s are advised to use on 27psi instead of the 12psi on yoko’s, this is such a huge difference that I thought maybe my new R888r arent sh1t tyres but they need a different pressure?

Any thoughts or experiences?

[Razzele]

the kumhos are fantastic. The Kumhos sidewalls are much softer than that of yoko/r888 which is why the factory recommend more pressure.

[Oli1122]

more pressure

Can't agree with that on as a general advice ref. the kumho's v70a
Soft at the front (195/50 R15) and medium on the back (225/45 R16) on a lighter n/a aa2 i start with 0.8bar cold all around.

On the Hockenheim GP Track you will need around 1-1,5laps before you getting in the right temp. window of the tyres (esp. for the fronts). Until then you can push hard through a 20min stint without thinking about releasing pressures a second time. And that even on 30 deg. cel. temps. outside

If the pressure is higher in the beginning and you do not release pressure during a few laps.. you will pretty quickly wash out the middle of the tyre. Don't get me wrong you can do both but I always want to drive during a stint and not tickling around in the pit with a freakin tyre pressure gauge.

But written that it all depends on different variables as geo settings, overall temperature, tyre dimensions, driving styles, ....

@speedmachine
Do you have any pics of your r888r's tyre pattern after track use?

[Razzele]

Well thats the factory’s advice not mine.

maybe go with your advice rather than Ariel’s.

[Maxi_z]

Oli1122

So what hot tyre pressure would you use on track with the kumho?

And what are your camber settings and tyre compounds front and rear?

Thanks

[wasp]

27 hot all round on the Kumhos works very very well.

Start at 24 cold on the front and 22 on the rear.

This is the Factory settings and I found it gave a great balance.

Cheers,
Stu

[thomas_fr]

27psi hot seems high no ?

[wasp]

27psi hot seems high no ?

Nope!
Obviously it goes against everything we ever knew for A048'S & r888'S 12 psi front, 14 rear) but it is definitely correct and works 100%.

All of us at Spa used these pressures on these tyres and they held up brilliantly.

Cheers,
Stu

[dc5ian]

i used to run r888 with the usual pressures.

i upgraded my wheels and went bigger, i can run a 255 tyre now. i choose to go r888r and run the same pressures as i did with the the r888. i was expecting more grip especially with the wider tyres. this wasn't the case and it was like driving on eggshells.

be handy to know if a different tyer pressure would help or do i need a new set of tyres. ive been off work all summer due to me tearing a ligament, as im self employed ive lost a fair amount of money so i don't have loads of spare cash at the moment.

[Toilet Duck]

I've recently switched from AO48's to Kumhos for track use. With the AO48's I ran 11psi front and 14/15psi rear HOT and this worked well with my set up. Front tyre wear was minimal (roughly two/three sets of rears to a set of fronts) and rears lasted approx three track days.

Running kumhos at the recommended 27psi HOT front/rear, the rears have been brilliant. However, after one trackday the fronts are destroyed. I originally tried a set of super softs at rockingham (two day charity event) and put this down to the compound being "too" soft. I switched to a soft compound and after one trackday at brands they were knackered.

This is what my rears looked like after two days at rockingham and one day at brands:



You can see that they are still "legal" treadwise.

This is my soft fronts after ONE day at Brands:



As you can see they are wrecked. Unless it's a pressure issue (too much maybe?), the only other thing I can think of is a suspension issue. I have the ten way adjustable Bilsteins and run the fronts at "10" so full hard. It might be that due to the kumhos having a stiffer side wall I need to back the suspension stifness off a bit. With the AO48's this was fine. Nothing has changed set up wise just a switch from AO48's to kumho V70.

Cheers

[Oli1122]

This is what my rears looked like after two days at rockingham and one day at brands:

Reading those high tyre pressures i'm pretty curious how your rear tyres look like from the side. I would guess the middle part between the two bigger grooves is washed out and noticeably deeper as the blocks on the inner and outer sides.
I never had those hot pressures you mentioned but those washed out part on lower pressures on the back tyres.

You murdered those fronts . Looks like you had a lot of fun on track More camber in the fronts?

So what hot tyre pressure would you use on track with the kumho?
And what are your camber settings and tyre compounds front and rear?

Front soft, back medium
camber front -0.75, back -1.75 (at the moment, ...will test with more camber in the near future)
bilstein (5-way): front 1, back 2
I have seen hot pressures around 1.2-1.4 esp. on the front left tyre.

Just my experience not necessarily right but works for me.

[John Scherrer]

Looks like you probably have understeer big time!?

Can try several things ..
- lower pressure on the fronts, higher on the rears
- reduce the front shock absorber stiffness, increase the rears
- increase front wing angle if wing fitted

[cvjoint]

I found that this car runs best on really low pressures and very soft compounds. The majority of recommendations for tires like Toyos built for heavier cars don't work on the Atom. You want to start at low PSI, get that sidewall to flex, in order to build heat. It's incredibly hard to build enough heat into the tires due to the light nature of the car. Compound wise, autocross tires are typically the only ones that have an optimal heat range that the Atom can get to. With slicks, you also have the option of formula compounds in addition to autocross compounds.

I start at 18 psi and end up with 20 psi and a tire temp of 110*F (43C) to 160*F (71C) depending on the ambient. I track at temps anywhere from 45*F (7C) to 105*F (41C). My optimal tire temp for max grip is 130* (54C)to 150*(66C).

Toyo R888R optimal temp is 160*F (71C) to 220*F (104C). I find that it is nearly impossible to get this kind of tire in the optimal heat range, especially the fronts. As a result I think it's a misapplication for the Atom. If this tire has to be used, I would start at very low PSI, the lowest that's safe without the tire coming off the wheel to build heat as much as possible.
See this link for optimal tire temps: https://www.tirerack.com/tires/tires.js ... oxes+R888R

[Atom120]

This is my soft fronts after ONE day at Brands:

That's quite impressive understeer!

Softening the front suspension is the quickest and easiest thing that will help, and adding more front camber will also help a bit too.

What you really want is to get the rear moving around a bit - steer from the rear!

[Toilet Duck]

The thing is, it wasn't really understeering, it "felt" OK. I do steer fro the rear, sometimes a bit too much ;-) I'm no racing driver but I wasn't hanging about.

Here's a recent clip from Rockingham (1st time there) with my first time using kumhos chasing down a Lamborghini Hurracan Performante :



And one chasing a 3.5R with paddleshift:



I was ruing super soft kumho on the front and they were obliterated.

I will definitely try backing of the front suspension a couple of clicks and reduce the front tyre pressure a tad. I may increase the front camber if that doesn't work, but my current geometry worked flawlessly with AO48's and I feel that I shouldn't need to make massive changes to get the front Kumho to work. The rear kumho are fine.

Cheers