Sam's build thread

[Sydneykid]

Alright you've convinced me Gary. 215 /50/15 makes perfect sense. The 225/45/15 (they have 225/50/15 too) V70A's are 2-3 year old new shelf stock from the kumho Sydney dealer. I'll have to weigh up the age and whether running so wide on the 7in rims will kill steering feel. If I am to run 225 on 7in rims, if you ignore rolling diameter, the 45 would be the better sidewall to run for that rim yeah?

As we talked about before, in regards to tyre profile (sidewall height) lower profile is better if the suspension geometry is set up for it. But a higher profile (tyre) is better if the geometry is not ideal as the increased sidewall flex can help retain the contact patch. The most important issue is bump steer closely followed by dynamic camber, if they are optimised then the lower profile should be better.

I did a bit of checking around on the Kumho V70A and the only consistent criticism (albeit from a small sample size) I heard was their lack of steering feel/feedback. Which the lower profile should help with. But in general not many people are using them, which concerns me. Personally I'd prefer to go with a known product, but it's your budget.


Cheers
Gary

[sambb]

yep I'm getting the same info re dull steering. From what I can gather they do everything quite well but don't set the world on fire at any one thing. They seem to use them a lot in Europe and the UK, but then again they have nearly zero access to the A050's that we are spoilt with and

they seem to have literally 10 different compounds of them available in the UK but over here I only see K60 which is the medium. T

hey also don't seem to talk about Hankooks much over there either. Is Hankook just a trans pacific type market? Might pass on them I think.
I would have sworn Garys motorsport tyres had said the DZ03G had a 215/50/15 (they do on some Japanese sites) but last time I spoke to them to confirm they said no, only 205's. They were a bit cheaper than A050's but I guess that's out now.
I found a guy with a single freshish second hand ( early 2017) A050 215/50/15. I think i'll buy it and if it looks half decent then I'll get a brane newey off Levens which will give me a front pair. That'll have to do me with 205's on the back for the next little while until I can round out the set.

[metalhead]

Just some follow up info on the AR-1s. They seem to be working pretty well at the last couple of events where I've put a little effort into getting some warmth into them before each run. I've been more competitive than I ever have been in the past, against the same cars and drivers. I've made no changes to the car except some bump steer improvement in the front. In the club event this past weekend I beat both Steve Woods and Jeff Schmitt. I still haven't beaten my best first split on the Continentals - but I have now equalled my second best split, and have beaten all the other splits. I don't think they're world beaters, but they are now working pretty well for me.

On the other side of the coin, one of my brothers mates with an mx5 recently spent a track day with a pyrometer, a set of AR-1s, and a set of Hankook RS4s (a more street oriented semi) - and was consistently quicker on the RS4s, swapping back and forth several times through the day. He did apparently report that the AR-1s felt better cold?

[sambb]

Yeah it could be that being a treadwear 80 (although that hardly ever means much in an apples for apples sense) that the AR1's are gripping up quickly in the hillclimbs. Did he think the AR1's were overheating on the track? I know that when Pete went from a fresh set of A050 mediums 195/50/15 to a fresh set of 205/50/15 at south circuit, same rims too (yes he has two sets of regameisters) he was slower on the 205's. He said it felt like the 205's were just sapping crank power, like they felt noticeably heavier. I wonder how much of your mates slower track times on the AR1's were due to weight which would be even more relevant for a small capacity NA like in an MX5. For you with your million horsepowers that'd probably barely come into the equation. Next time we meet pal I'm going to have more rubber on the front, yokies too, like an F1 car in reverse - you're getting too close for comfort. No more of this 195 rubbish!

[Sydneykid]

I know that when Pete went from a fresh set of A050 mediums 195/50/15 to a fresh set of 205/50/15 at south circuit, same rims too (yes he has two sets of regameisters) he was slower on the 205's. He said it felt like the 205's were just sapping crank power, like they felt noticeably heavier.

If Pete can really feel a less than 1 kg per tyre weight difference (195 v 205) then he has amazing feel. Especially since he probably used more than 4 kgs of fuel during the day. I know on really low powered historic cars when we fit much wider/stickier tyres they actually (measurably) go slower, but that's more related to the additional friction than the weight. A 195 to 205 A050 would hardly have noticeable friction increases.


Cheers
Gary

[seangti]

Alright you've convinced me Gary. 215 /50/15 makes perfect sense. The 225/45/15 (they have 225/50/15 too) V70A's are 2-3 year old new shelf stock from the kumho Sydney dealer. I'll have to weigh up the age and whether running so wide on the 7in rims will kill steering feel. If I am to run 225 on 7in rims, if you ignore rolling diameter, the 45 would be the better sidewall to run for that rim yeah?

I've ran the V70's in a 17 and was really quite underwhelmed. There's not much tread depth so they wore quickly and didn't really deliver the lap times. I went from the V70 to the Federal RSRR and got quicker lap times (by like 1-2/10ths) and haven't over heated the tyres like the Kumho's. There were consistent once warm, but from recollection took a bit longer to heat up than the feds do.

I'll be going Nankang's next as I've been hearing pretty good feedback on them (and they have to be quieter than the feds).

[sambb]

yeah I know Gary I was sceptical too but he swore it felt more doughy and he did go slower (when we all started getting quicker) and they were heat treated new from Levens as well?? not sure

[sambb]

Andrew which circuit did you run at Ringwood? Nice one beating Woods - what was the margin? You watch, Schmitt will have proper R specs soon and Woods will do what Liam did and mod his brakes to get onto smaller rims so he can buy some decent semis. They wont stand for that.

[Sydneykid]

yeah I know Gary I was sceptical too but he swore it felt more doughy and he did go slower (when we all started getting quicker) and they were heat treated new from Levens as well?? not sure

There are 3 things involved, extra weight, wider so marginally "stickier" and larger diameter so taller gearing. Maybe all 3 added together made a difference, it's not impossible. But there's usually far more in track and driver variability than in a one size tyre change within the same compound. For example I need to work up to it, it takes me a few runs to get in the groove, so by the time the track is dirty from other excursions and it's hotter in the early afternoon that's when I'm likely to go better. So I've missed the cooler air of the morning and maybe a clean track compared to others that are on it from the get go.

That's why we have so much data available from the race cars, nowhere to hide, it's the ultimate truth serum.

Cheers
Gary

[metalhead]

Yeah it could be that being a treadwear 80 (although that hardly ever means much in an apples for apples sense) that the AR1's are gripping up quickly in the hillclimbs. Did he think the AR1's were overheating on the track? I know that when Pete went from a fresh set of A050 mediums 195/50/15 to a fresh set of 205/50/15 at south circuit, same rims too (yes he has two sets of regameisters) he was slower on the 205's. He said it felt like the 205's were just sapping crank power, like they felt noticeably heavier. I wonder how much of your mates slower track times on the AR1's were due to weight which would be even more relevant for a small capacity NA like in an MX5. For you with your million horsepowers that'd probably barely come into the equation. Next time we meet pal I'm going to have more rubber on the front, yokies too, like an F1 car in reverse - you're getting too close for comfort. No more of this 195 rubbish!

Don't know much more information (about the mx5) than what I gave you unfortunately, will have to chase up my brother for more details. It is true though that the Nankangs are heavy.

Don't make your car quicker mate, or I'll never catch you!

Andrew which circuit did you run at Ringwood? Nice one beating Woods - what was the margin? You watch, Schmitt will have proper R specs soon and Woods will do what Liam did and mod his brakes to get onto smaller rims so he can buy some decent semis. They wont stand for that.

A2A, so I did have the advantage of a couple of extra runs at the straights (it's the same as the standard layout but two runs around the top loop). Didn't beat them by much. Steve is on the R888Rs, and Jeff is on the AD08Rs - which he has been quicker on at Ringwood than on his other wheels which have Nankang AR-1s on them...