With the increase in trackday popularity, semi slicks have been getting a lot more attention. The Toyo R888 is arguably the leader in the market, featuring as the OEM tire on a number of extreme high performance Japanese Sports Saloons, but it isn't the only semi slick worth considering. The Michelin Pilot Sport Cups comes fitted to the Porsche 911 GT3 RS by default, the Kumho V70a was the winner of the Autobild group test, and the Yokohama Advan A048 is the Lotus tire of choice. The market has progressed from only a handful of options 5 years ago, to now over 20 different semi slick trackday tires available.

With all this new interest comes a lot of confusion, and there are a few basic questions that come up fairly frequently. "Should I put trackday tires on my car?", "How much faster is a semi slick over a road tire", "Will I crash on a trackday tire at the first sign of rain?". All good questions, but no one seems to have answered them particularly well.

To answer the above we got ourselves a set of road tires, a set of semi slicks and decided to head to Donington Park on a warm summers morning.

The tires

The tires we've bagged for these test are both arguably class leading.

Kumho V70a
The trackday semi slick is represented by the Kumho V70a, also known as the Kumho V700 in America. This is a well respected track tire, that just so happened to beat the other leading brands offerings to win the Autobild track day tire test back in 2005. Autobild found the V70a excelled in its dry weather grip, leading the dry braking and finishing a close second in dry cornering. Like a good race tire, the V70a is available in 3 compounds, and for this test we've picked the harder compound tire to match our test vehicles characteristic (mid-engined 315bhp @ 1100kgs).

Toyo T1R
For the road tires we picked the Toyo T1R. This is Toyos pinnacle high performance road tire that has proven itself a firm favourite amongst tuners and track day enthusiasts alike. Known for it's soft compound, the T1R is the perfect choice to represent the road tire on track.

First Impressions

The first thing you notice about the Kumho V70a while fitting it is the weight. Without scales to hand, it would be impossible to say just how much lighter the tires were than the worn Bridgestone SO2s coming off the rim but it was significant. They are also noticeably smaller than the Bridgestones when placed next to each other. All this means more performance, as rotational inertia is the most important weight you can remove from a car, and the smaller rolling radius effectively shortens the gearing.

The second thing you notice is how they sit on the rim, they're more pinched in profile, offering a much tougher sidewall look. Recently one of the fronts looked a little under inflated, and on checking the tire pressure the reading came as a little shock, with just a single PSI registering. While it was frustrating to have a puncture, it really did highlight how strong the sidewalls are constructed.

In comparison the Toyo T1Rs look... cool. It's not hard to see why this tire is so liked, it sits proud on the rim with an aggressive tread pattern which looks sticky even when stationary. You'd certainly trust the T1R over the V70A if there was any standing water involved, but fortunately our mid August track booking ensures it will be dry...

Road VS Trackday Tires - The Track day

It's a warm August afternoon as the car rolls slowly into garage 27 at Donington Park. As the area echoes with pings of the exhaust cooling it's time contemplate the excitement of the day ahead - tirereviews first official track tire test is less than an hour away from beginning. We have our usual array of track day extras with us but with one important addition, a full data acquisition system from Racelogic.

The question we have come here to answer is simple - how much faster are track day specific tires over normal road tires, and just as importantly, how do they feel back to back. The comparison will be made not just on raw data but also on driveability. Racing slicks are extremely fast once warm but are difficult at the limit, quick to let go and will have less experienced drivers going backwards into the tire wall before they have a chance to correct any slide they might experience. You go to track days to enjoy yourself, not to strangle the last 10th out of your car...

The Semi Slick - Kumho V70a

As the minutes tick down to the start of the session the final checks are performed. Four PSI is let out of each tire to compensate for track temperatures and the consequential increase in pressures, the tires are given the visual once over and the damping is increased to 12 clicks in at the front and 13 at the rear. The car is ready.

The claxon marks the start of the test day. First task of the day is to put a few banking laps on the V70a's, set up the data logger and make sure our temperatures and pressures are where they should be once hot.

The first few corners fill you with confidence. The car feels solid on its new rubber, the turn in is positive and the tires quickly obtain their needed slip angle. A lap later and everything is warm so it's time to push on, the car improving more and more as the tires come up to temperature. After a couple of quick laps it's time to return to the pits to check how the tire pressures have reacted.

Once the car has had time to cool down we head back to the circuit to get some fast laps in. It's a busy test day and traffic is a problem but the car feels good. Braking is strong, the car is controllable on the limit and the times are getting better.

If anything the front of the car feels a little numb, the nose seeming to hesitate for a split second before changing direction but when the tires do bite, is it strong and they happily guide you towards the apex.

Finally the track opens up and there's nothing to impede progress. Leaving the final corner it's time to get on with the job at hand - how consistent can track tires be, and just how fast are they?

The first lap is a 1'23.4, a strong time. The second lap is half a second faster, yet still feeling controlled, no sliding, no moments, just planted. Braking is where you make up the time on track rubber. The car is fitted with race discs and pads yet it struggles to lock a wheel in the huge braking zone at end of Starkies Straight.

A few more laps prove just how consistent and sure footed these tires make the car feel. They're extremely confidence inspiring and give the car a feel not experienced on road tires before. Sadly the morning session comes to an end, meaning it's time to fit the Toyo T1Rs and see how they compare. There was probably a little more time in the car but the session ends with a best lap of 1'22.9.

As you can see from the above, the track tire can pull much higher G under braking, hold a higher speed through Crainer Curves, and allows you to get on the power earlier to exit the corners faster

The Road Tire - Toyo T1R

An hour break for lunch gives time to take a breather after the morning's adventure (and perform a four wheel change). As the lunch break ends we roll out onto track, and without considering the new levels of grip, we attack the track with the same enthusiasm and momentum built up during the first session. Sadly, the cold, road-specification Toyo T1R tires aren't as keen to slow the car into turn one, missing the apex by over a metre and nearly exiting the car into the gravel.

Having finally collected everything from turn one, it's time to learn the car again as what's underneath has a totally different feel to earlier in the day. The most noticeable difference is the braking. What was previously a test of just how hard you could step on the middle pedal is now back to an art form, delicately feeling each individual wheel reach its limit of traction as the speed scrubs off. Turn in surprisingly feels a bit more positive, but as the rear follows you into the corner it now has no objection to step out of line if you dare trail the brakes too close to the apex. Exiting the turn - which puts 315bhp through the 225 section rear Toyos - now requires a little more finesse to stop power-on oversteer.

Again, a piece of clear track presents itself and it's time to get serious. Lap after lap we pound away, each lap within a tenth of the last. The car is moving around a lot more, the tail is drifting out of the hairpin, the nose is unsettled under braking - it's hard working. After 4 hot laps the Toyo's decide enough is enough and grip falls away rapidly - the rear tires have over heated. Driving quickly turns into drifting at every hint of direction change, it's time to fall back to the pits and take notes.

The best time was a 1'25.0, just 2.1 seconds slower than the track tires but there's something else. As the driver I'm sweating more, and I'm smiling more. The car was moving around, it was alive. Hard to drive, but much more rewarding. A less experienced driver might have found this unnerving, and would certainly have been many times slower but as the day closes the surprise result was not that the road tire was just 2.1 seconds slower, but it was a far more fun challenge.

Track Conclusion

Road tires or track tires - it's a question that often gets asked. But unfortunately, there still isn't a straight answer.

Track days are about having fun, not ultimate lap time. How the car feels is more important than bettering your lap time by a fraction of a second. If you're new to trackdays, or aren't confident with the car moving around a set of track tires like the Kumho V70a will help you ease into driving quickly and give you time to work on your craft and lines. They provide a far more stable base to work with and fill you with confidence that the car will do everything you ask of it.

As someone with a little more experienced of driving on the limit the bigger smile came from the road tires. Not ultimately as quick, but they made driving a high powered car a far more delicate affair which was ultimately more rewarding. 2.1 seconds a lap isn't going to be noticeable on the average track day, what is going to be noticeable is the smile on your face at the end of the session. The Toyo T1Rs overheated a little quickly which means your sessions will be shorter, but a tire like the Bridgestone S02 will run exactly the same lap time and allow you to stay our for twice as long.

Road VS Trackday Tires - The Road Manners

There's not a huge amount that can be said for the Kumho V70a tires road manners - "OK" about sums it up. Imagine a road tire that's a little noisier, takes a little longer to warm up and gives you a bit more feedback and you're imagining the V70a on a nice summer evening. Throw in a bit of rain and the dynamics change.

In the wet, once the tires are warm the grip is there, but trying to get heat into the tires quickly turns into a cat and mouse game. Wheel spin in third isn't unheard of and if the ambient temperatures are cool, you might as well forget warming the front tires in a mid/rear engined car. Throw in some standing water and the narrow channels will choke quickly and have you aquaplaning at any speeds.

This isn't a criticism of the V70a, it's just a characteristic of the semi slick tire. By design they will have very little tread for water dispersion, and a compound that needs heat to work, but then this is part of their charm on the track. The softer compound versions might fair a little better, but they'll still be miles off a road tire with standing water.

Can you run semi slicks as an every day tire? As mentioned in the introduction people do, but these usually aren't every day cars. If you understand the limitations, and are willing to drive accordingly you will be fine, but don't expect to enjoy your commute if it dares to rain. Would we? In our test vehicle with no driver aids, no traction control and power delivery that could be described as peaky, no. In a super saloon like an EVO X, most certainly yes, providing our wallets were deep enough...

The Data

For all the speed traces, lateral G measurements and map overviews of this test please head over to the road vs track tire data page

As always, any comments or feedback are welcome below.