Yokohama AD08R tyres and geometry

Since enjoying Griff on the track as well as the road I have found that the Toyo T1R tyres do not seem to perform very well on the track. I really rate the Toyos as an all round tyre on the road but unfortunately they overheat and melt when exposed to constant cornering forces.

I did not want the hassle of having another set of wheels for the car for track day use only as I only do around 2-3 track days a year. After doing some research online two tyres seemed to get continue praise, the Toyo R1R and the Yokohama AD08R. I noted that the Toyo R1R only starts off life with 6mm of tread and the AD08s start with the full 8mm, I am not keen on the idea of paying for a tyre that does not have a full 8mm of tread so I went for the AD08Rs.

I could not get the AD08Rs in the same sizes I had on the car originally so using an online tool I calculated the rolling radius of the wheel before and after to get as close as possible to the original. I ended up with the following sizes which so I am lead to believe were the sizes used on some of the early non-PAS Griffiths.

Front – 205/50 R15
Rear – 225/50 R16

I had the tyres fitted at my local garage an immediately after driving out I noticed how much better the car felt on turn in, I was always a bit disappointed when I swapped from the OEM Bridgestone SO1/SO2 tyres to Toyos as the sidewalls did not feel as stiff and reading up this is a common complaint. The AD08Rs have a Kevlar reinforced sidewall and this for me was reminiscent of the feel of the old Bridgestones. The feel of the car and grip was also very encouraging, I normally hate having new tyres as the car feels a bit squirmy and unsettled on new thicker tread, I tend to prefer tyres once they are half worn, these new tyres did not feel too bad at all.

My only compliant was that I could feel the geo needed to be addressed as the car was not pulling straight on acceleration and had a tendency to wander to the right on a trailing throttle.

I booked a session with Super Tyres in Maldon for a 4 wheel alignment and geometry.

The initial read out from the hunter system showed that the geometry was in need of some attention.

I provided my own settings which I found on the PistonHeads forums many years ago and I have used ever since:

TVR Geo – Neill Anderson
Front & rear camber 0.75 to 1.25deg negative, as equal as possible side to side
Front tracking (toe) 10 to 20 minutes TOTAL ACROSS AXLE (5 to 10 minutes each wheel)
Rear tracking (toe) 4 to 6 minutes EACH WHEEL (as equal as possible side to side)
Front castor 4.75 to 5.25deg Positive (more important that each side is within 0.5deg of the other)

NOTE: As the front and rear wheel alignment are adjustable independently, but only the front wheels are connected to each other (by the rack) it is important that the pair of rear wheels are aligned to the nominal centreline of the car and not just to each other. The castor is not usually adjusted, the spacer at the upper ball joint is simply to ensure adequate clearance at the full extents of negative camber adjustment.

A couple of hours later the car was dialled in and the final read out looked good.

I took the car for a spirited drive and what an improvement, car pulls straight on acceleration, the tyres stick very well once they have some heat in them, turn is much improved.

2015 Update

On track these tyres are simply amazing. The Toyo T1Rs where good for a very short period between being stone cold and slippy to being too hot and melting. The AD08Rs grip and grip, not only is the grip fantastic they also inspire confidence as you know they will hook up time after time, it was a gamble with the Toyos as when the overheated they had the tendency to bin you off the circuit randomly when pressing on.

Goodwood Circuit I had the telemetry setup and recorded cornering at 1.0G at 121MPH.

Later that year Castle Combe 1.2G at 65MPH

Really impressed by these tyres, they are a great compromise between a road tyre like the Toyo T1R and a full out track tyre like a Toyo R888. As I discovered Toyo T1R is great on road but not good on track, R888 are great on track but not that suitable on road. Yoko AD08R does both very well, not quite as good in the wet as a T1R but still safely drive 70MPH on motorway in heavy rain. Not as good on the track as an R888 but very close. A great compromise tyre without having to maintain a set of winter tyres, summer tyres and track tyres.