l18-b110 - I keep squeezing the other things in because it is important. Hell I didn't even mention that the wider the tyre the less camber it tends to 'like' - which can be indicative of things.

Of course f1 (or anyone else) is running the widest tyres they can (or what they must run) - you're mis-interpreting what I'm getting at. The reason to run wider tyres is not because they grip better 'per se' - if that's the case I welcome you to get some bob jane australian all rounder tread put on some 265 width tyres, and I'll bring some toyo ra1s around to compare. What I am saying is the _reason_ for the widest tyre possible in a racing situation is to give the opportunity to run the stickiest compound possible, but still get enough tyre life to finish enouh laps between pitstops (or the sprint race distance or whatever). It's not just the width.

I _did_ definitely mention that a bigger tyre won't overheat as quickly. I also mentioned at the start of the post that I was simplifying things a bit to get a point across. If you want to discuss hysteresis (which I probably mis-spelt) and how friction co-efficient actually drops off *(albeit marginally in contrast) with downforce, go for it. I'm not in any way taking this personally, and am happy to discuss it at any length. I'm also not perfect, by any measure, so take anything I say on that basis too!

If you wouldn't mind (and I ask this sincerely, not as a smartalec) - do you happen to have pyrometer readings for the tread - possibly - outer and inner edges and centre region - for the tyres you ran that had the big difference before and after. It'd be interesting to see the spread of temp - both from before and after different tyres, but also to know what temps they ran across the width of the tread, it might be enlightening (to me, if no-one else)


What I was trying to get at, and I'll re-state it (and I know you've said that you would go along with this, and as such we are both sort of talking about two slightly different but related tangents) tread compound is the big deal. It's (relatively) hard to overheat tyres on the street, in most parts of this country, and I can't speak for elsewhere, you'd probably end up getting arrested if you drove hard enough and long enough to overwhelm the tyres. Brake pads - well it'd be relatively hard to overcook a1rms with a bit of touring on twisty roads, but certainly possible on a circuit.

It's not so much I'm getting 'tied up' with theory, but rather I'm just as interested *(if not more) in the why, than just the 'what'. I first came across the whole idea as a teenager - when I was playing mostly with toranas (which are understeering pigs in std form, due to the engine location and polar moment of inertia issues, not that I had any idea of what that meant at the time). I ran 205/60 13s on the almost 'mandatory' sprintmaster mag wheels that are so well linked to the vehicle. I then had a set of wider wheels and ran (and I forget - I think it was bf goodrich, or it might have been bridgestone) 235/50 13s. Then I got a set of 185/60 13s given to me - a set of yokohama a008s (remember this is like 20+ years ago, they were 'something' back then - there were also the a008R which were a softer compound again.. What I really wasn't expecting (I just ran them because I had them sort of thing) was how much better the damn things gripped than the other larger tyres. I didn't manage to overcook them on the street, but I also have to be fair and say I didn't push the cars relentlessly or anything, a few quick squirts here and there.

It wasn't until years later that I got some of the books mentioned, that it started to become clearer to me. And I did my best to apply it. I previously tried more and more neg camber on the torries, but it was rapidly diminishing returns (not to mention braking started to be affected). If I get another torana, engineer willing, I'll relocate the motor rearward somewhat. Not only will it improve entry understeer, but ironically they also have trouble out of corners - not polar moment of inertia related, but rather just a lack of downforce (relative % of the cars weight on the rear tyres)

I'm not saying tread compound is the 'only thing in the universe' but I am suggesting it is the prime consideration.

I'm DEFINITELY not advocating running 155 width tyres or anything. I hope I haven't come across like that. Perhaps I'll restate it better thusly - width isn't 'all that' I'm not saying run bicycle tyres, but find the specific brands in the wider sizes that have a good track record, it will make or break the deal. There's (unfortunately) seemingly no shortage of tyres available that are 'big' that are also very mediocre as far as grip is concerned.

the same thing applies to brake pads. 'larger' pads, which wrap further around the disc, don't stop better, unless you are reaching the temp limits of the smaller pads. (*if the pad material is the same). The same is true of brake shoe width. IF you are getting them quite hot, then sure, wider is better, but for single stops (or a handful of multiple stops) it won't change things. NOW bigger diameter discs, same pads, definitely improve things, because then they get more leverage.

and one more thing - that's a wicked machine mate.