Tyre swap - July 2009
The A539s I've been running for the last 4 years are now rapidly approaching the end of their life. With a trackday booked for September, they would soon be finished completely! So I started doing some digging into a suitable set of replacements; the A539 is no longer available, so I needed to find a suitable alternative. This proved tricky, as 14" rubber now seems to be dominated by either cheap and cheerful brands, or expensive soft rubber such as AO48Rs, Toyo R888s etc which are not suitable for my year round use and high mileage. In the end the only real option seemed to be Toyo T1Rs in 195/55 R14. This was 10mm wider than the present 185/60 R14 size, but with a similar rolling radius. However, as a slightly oddball size they aren't especially cheap at about £210 a set
A bit of further digging revealed that 15" tyres are much cheaper, e.g. a set of 195/50 R15 T1Rs can be had for about £115, so nearly half the price of 14"s. Also there are various 15" tyres that come well recommended for kit cars. Hmm. I had a reluctance to swap the wheels as I liked what I had, 14" wheels tend to be lighter than 15"s (and I know my wheel and tyre assembly, at about 13kg, was reasonably light), and 195 width looks a bit wide to my eyes... however I decided to look into the possibility of new wheels & tyres, but on the understanding that I would only go for it if I could keep the weight gain to the minimum, and still not spend much extra money!
I struggled a bit to get weight data for many wheels, but thankfully found info on 4 wheel styles that wouldn't break the bank:
The TSWs were straight out of the running because of the weight (and made me immediately very wary of going for a wheel with no weight info) but the other 3 would result in a wheel and tyre assembly of around 14.5kg (15" tyres seem to hover around the 8kg mark). A 1.5kg increase per corner is not insignificant, but I figured it was probably the way forward for maximum tyre choice at lowest cost.
In terms of tyre choice, these are the ones I considered:
I now set about hunting for a good deal on a wheel and tyre package using some combination of the 3 wheel and 4 tyres on my shortlist, and came up with these options:
At this stage I asked for opinions on the JPSC forum and from various friends, and was surprised that the black wheels were by far the most popular option. Black wheels are a bit of a love / hate thing for me, they seem to work on some cars and not others, and can quite often get lost in a 'black hole' the middle of the tyre. However, the machined highlight on the edge of the Inovit rims helped to lift their look a little, and I think they actually really suit the car, matching well with the gloss black sidescreens and satin black roll bar. To top it all they were the cheapest option at £295 all in fitted with Toyo T1Rs, and were being sold by Midland Wheels who are based 15 minutes from my work! I paid them a visit to have a closer look, which also gave me an opportunity to confirm the weight at 6.5kg per wheel (without tyre!). I liked them enough to order a set! The end result is shown below:
The Mojo certainly now looks a little more purposeful!
Clearance to the cycle wings is very tight, about 3mm at the closest, but so far this hasn't caused any problems. The weekend after fitting the tyres I drove 300 miles, much of it on wet roads and some of it in heavy rain, and the Toyos worked very well, ejecting lots more water out from under the cycle wings than I can ever remember the A539s doing. They also seem much less prone to tramlining in grooves on the road or when driving over white lines and cats eyes, something I wasn't expecting to change.
Another thing to note is that the ride doesn't seem to have suffered with the extra unsprung mass, and if anything I think certain aspects have improved; the car now feels a bit less bouncy (which I'm putting down to less tyre wall flex over larger bumps).
In terms of cornering grip, they are more than a match for the A539s. So, although early days at present, I'm currently very happy with the swap! The old wheels and tyres will get shoved back on again if the trackday in September is looking likely to be dry, after which I'll be selling the old 14" wheels and tyres.