18 replies to this topic

[REDA9X]

So wondering why no has posted new mag out with the detailed story of Brock 79 winner, interviews with all concerned etc
I am about half way thru it and have enjoyed it so far, one comment was John Shepperd say car ran 2.78 ratio, I remmeber discussing on here with RedA9X say it was much shorter. Other stuff that is interesting to me was I had chatted to Harry Firth over dinner a few years back and he was very proud of the fact the cars were little changed from what he built in 77, and so far reading John Sheperds comments that seems to be true, John spent a lot of time and effort fiddling with things but didnt make any major brak thru in terms of performance, just lots of little adjustment that yeilded small gains here and there, 12 horse power from changing the sump design but mainly only 2 or 3 horse power

John doesn't actually say the cars ran 2.78 ratio diffs, he says he thinks it was something like that. The L34 ran 2.78, the A9X was released with the 2.60 to be used at Bathurst. The thing was the A9X allowed a much larger rear tyre to be fitted, which gave a larger rolling diameter. This made the 2.60 useless. I spoke to John about this years ago and he told me 3.08 as did Bob Morris. I guess this weekend the Group C boys will be able to get some idea of the correct ratio at Bathurst. If you look at it this way though, a V8 Supercar uses a 3.15 diff at Bathurst, the rear wheel rolling diameter is smaller than an A9X was , top gear is still 1:1, and they rev a little harder, so 3.08 sounds about right for an A9X, exactly the same as the VC-VK Commodores ran.

[lcgtr1970]

yeah i had a read of it at the newsagents the other day and wasnt really impressed either...which is strange coz i normally buy up anything torana related.
i agree the articles didnt grab me and unfortunately i just didnt get that urge to buy it. oh well.

[REDA9X]

John Sheppard says "....maybe we used a 2.78 ratio at Bathurst, and that may be so, but going up the hill is just as important as coming down the hill. So as I said, I would have done it at the time and recorded it in the books; but I don't recall."

Yes they have the chase these days, but the cars now have at least 620 horsepower and rev to 7500 every lap, reach speeds of close to 300 and brake a lot later. They have 6 gears to get them up to speed quicker, the old A9X had 4, top gear was still 1:1. The A9X had 400hp on a good day, reved to 6000, maybe 7000rpm on a qualifying lap and reached 260 km/h and had to brake a lot earlier.

[REDA9X]

I'm not trying to be a smartarse mate, I'm just pointing out some facts.
The Group C cars could and most likely will be set up differently as there are variables involved such as the tyres may not have the same rolling diameter as in 79, the straight is slightly shorter, the cars will only be doing a few laps etc....

[Mort]

Bought it a couple of days ago with latest Street Machine, only flicked through it at the moment but looking at the replies don't think i'll be in a hurry to start reading it. Start work on Friday, might take it in and read it while getting loaded, it should last me through this cycle.


Mort

[TerrA LX]

LOL Redrida and niteA9x you are both making sence.

[enderwigginau]

Cruiza,

you wouldn't want to hit your top speed/rpm just before Murrays, you'd want to spend a fair and reasonable amount of time travelling downhill as fast as you could. �The boys would have been beginning to brake at about the distance of the pit entrance today, if not further back.

[REDA9X]

Cruiza,

you wouldn't want to hit your top speed/rpm just before Murrays, you'd want to spend a fair and reasonable amount of time travelling downhill as fast as you could. The boys would have been beginning to brake at about the distance of the pit entrance today, if not further back.

From watching the racing all these years and seeing the interviews with drivers I have been under the impression that they dont want the cars sitting on the rev limiter, but rather hitting max revs just as they need to brake for the next corner, given that the last few km per hour are slow to achieve

Thats true, but as grant said, they had to brake earlier as well. remember the brakes were a lot smaller and they didn't have pad changes back then. I remember Bob Morris telling me on a qualifying lap they braked just on the last hump and hoped the car would slow enough to get through the corner.

[76lxhatch]

OK this next post is going to put me in the 'what a sad barstard catagory'

Yes. Yes it does.

[REDA9X]

vote 2 for that one it's been said over and over now.
Next time you speak to Harry Firth ask why the diff failed in Harveys car in 77.