Input on tire pressure for Toyo R888R please

[MPowerZ_32]

Hi,

I've been running R888R in 275/35/18 square setup for a couple of track days now. My experience has been the grip drops off quite a lot after less than a handful of laps each session.

I will probably be switching to a more consistent tires once the R888R wear out. I've got maybe 3 more track days worth of thread left. My question is what is the best hot pressure for R888r. I've been running 33PSI hot. I got fairly good temp distribution across the thread. I'm wondering if the pressure is too low causing excessive heat, thus loss of grip so quickly. Would running a little higher, say 35 PSI hot be a good idea?

All input would be greatly appreciated!

[tlrid3r]

Yes. That’s very normal for those tires. They aren’t great tires for track. I gave up on them. You are spot on pressure. So you are doing the correct thing.
Start 8:42 for toyo

[redpriest]

m3number86

[SYT_Shadow]

the best pressure advice is to stop running them. They are not track tires at all.

In the probably hundreds of sets I've used throughout the years, this is the only set I've thrown away before they were worn. Complete shit

[DrFerry]

Originally Posted by MPowerZ_32

Hi, I've been running R888R in 275/35/18 square setup for a couple of track days now. My experience has been the grip drops off quite a lot after less than a handful of laps each session. I will probably be switching to a more consistent tires once the R888R wear out. I've got maybe 3 more track days worth of thread left. My question is what is the best hot pressure for R888r. I've been running 33PSI hot. I got fairly good temp distribution across the thread. I'm wondering if the pressure is too low causing excessive heat, thus loss of grip so quickly. Would running a little higher, say 35 PSI hot be a good idea? All input would be greatly appreciated!

A Few Questions:
1) What tire temperatures are you seeing across the face of the tread from inside shoulder to outside shoulder?

2) Is the difference in tread temperatures between inside and outside shoulder <=10F?

3) Are you running negative camber in excess of -4.5 degrees?

See the image below for tires with better heat tolerance. Yes, generally speaking higher cold starting pressures will result in lower overall carcasse and tread temperatures due to lower strain cycling and flexing. Therefore lower hot pressures and temps will result - which should yield more consistent lap times. Emphasis on generally speaking. 33psi hot on a 3600lb rear wheel drive car is low IMO. 38psi hot (end of session) will probably yield better consistency and lower tread temps.
.
Cross threaded:
https://www.m3post.com/forums/showthread.php?t=1916791
https://www.m3post.com/forums/showpo...&postcount=450
.

[MPowerZ_32]

Originally Posted by DrFerry

A Few Questions:
1) What tire temperatures are you seeing across the face of the tread from inside shoulder to outside shoulder?
2) Is the difference in tread temperatures between inside and outside shoulder <=10F?

The temperature diff between the inside and outside was less than 10F, with the inside being higher. Unfortunately, I forgot the actual values. I think the temp was about 140F? Seemed pretty high. I will be sure to remember on the next track day.

Originally Posted by DrFerry

A Few Questions:
3) Are you running negative camber in excess of -4.5 degrees?

I run Ohlins Dedicated coilover kit with the Vorshlag camber plate. The front is -3.0 and rear is all OEM hardware with camber maxed out. Front zero toe and rear slight toe in. I was pretty happy with the temp diff inside vs outside with this setup.

Originally Posted by DrFerry

See the image below for tires with better heat tolerance. Yes, generally speaking higher cold starting pressures will result in lower overall carcasse and tread temperatures due to lower strain cycling and flexing. Therefore lower hot pressures and temps will result - which should yield more consistent lap times. Emphasis on generally speaking. 33psi hot on a 3600lb rear wheel drive car is low IMO. 38psi hot (end of session) will probably yield better consistency and lower tread temps.

This makes sense. I found Toyo's official recommendation on R888R: https://www.toyo.co.uk/page/index/id.../set-up-advice
It also calls for 37 - 40 PSI hot. Since our car falls in the "very heavy" category.

[DrFerry]

Originally Posted by MPowerZ_32

The temperature diff between the inside and outside was less than 10F, with the inside being higher. Unfortunately, I forgot the actual values. I think the temp was about 140F? Seemed pretty high. I will be sure to remember on the next track day.

140F is far too low for the tire's tread compound to "come-into" its full operating grip regime potential. Generally speaking tires of this sort begin to work optimally from 180F to ~210F. In other words when the tires are not 'up to temp' -> grip and lap time are being left on the table (under utilized). Heat enters the tires from various transfer paths. Heat from the brakes passes into the hub, then into the wheel and then into the tire by heat transfer (conduction). Heat also comes from using the tire at its grip limit when cornering, braking and accelerating (due to friction) as well as merely rolling down the track/road due to rolling resistance.

Beginners are sometimes not able to work the tire's tread compound(s) into its best grip operating temperature window, until the ability to drive the tires at their limit is learned and achieved (car control skills). At higher speeds a thermal balance is achieved from convective cooling due to air passing over the tread, heat conducted from the brakes and friction from cornering + acceleration loads.

As the capability of the driver (and car) improves, steady state tire tread temperatures will increase. If aerodynamic loads are increased by adding wings, canards and splitters - then steady state tire tread temps will also increase. Aim for at least 180F hot tire tread temps when you come 'hot' into the pits in the mid to late end of session. Have someone stationed and ready to take tire temps with a pyrometer or infra red thermal sensor. Good luck.