Wheel diameter

[Mike Costigan]

As far as I am aware, 18" wheels were exclusive to the vans, export cars were fitted with either the standard UK specification, or 16" wheels, depending on destination.
Westminster Green was a standard stock colour for the 1935 Ruby, but not for the Open Road Tourer; however standard colours could be ordered at no extra cost, but subject to a delivery delay, or non-standard colours could be ordered at extra cost. So if your car was originally Westminster Green it just means the original owner was prepared to wait for his colour of choice.

Edit: I have just checked the A7CA Archive website, and Catalogue 1290 (dated October 1935) quotes 4.00x18" as standard export specification (see page 32) - you learn something every day 

[Ian Williams]

Quote Mike C "Edit: I have just checked the A7CA Archive website, and Catalogue 1290 (dated October 1935) quotes 4.00x18" as standard export specification (see page 32) - you learn something every day"

Interesting Mike, in NZ it appears common that Ruby era cars came with both 16" and 17" wheels, 18" wheels are somewhat or a rarity, I am not saying they are completely non existent but I have never seen a set here.

[Erich]

Charles, that certainly helps. My 17 inch wheels have 3.50s X 17s at the rear and 3.25 X 17s at the front. I had thought that changing the FDR this way not only changes the FDR but also lowers the CG. Am I missing something regarding this hill climb and the optimum FDR?

[James Anderson]

In reply to the initial question of this thread, I'm sure I read somewhere that for some obscure reason some if not all export A7 Swallows had 17" wheels and their use may have applied to other export production models of A7s. This would bring the date of their production and use to well below the date of 1934 that Ruairidh mentions. I know this news made me more happy about my 'far from correct' Mk2 Swallow that for all its incorrectness looks quite comfortable with them and has good acceleration and speed to match.


  P1100100 (2) (800x610).jpg (Size: 343.22 KB / Downloads: 219)

[Austin in the Shed]

Charles, that certainly helps. My 17 inch wheels have 3.50s X 17s at the rear and 3.25 X 17s at the front. I had thought that changing the FDR this way not only changes the FDR but also lowers the CG. Am I missing something regarding this hill climb and the optimum FDR?

I think Charles is limited on wheel dia by the VSCC regs.If I were you and was only going to use the car for 1 hill climb event and for road use out there I would leave the 4.9 axle in and just swap the wheels,and it does lower the c of g a bit.
I feel the 4.9 ratio is good if you don't have too many steep hills to climb and doesn't feel under geared on the flat especially if you have a reasonably powerful engine.
If 3 speed box yes C/Ratio

[Ian Williams]

I run a 5.25 diff and unrestricted by VSCC rules use the full range of wheels from 15" to 19" depending on venue, 15" wheels give me a 2 second gain on one particular hill by putting me in the power exactly where I need it.

[Alan]

The problem you have is not with top gear, but the intermediate gears. 3.50x17 wheels with a 4.9 diff will give more or less the same gearing in top as 3.50x19s and a 5.25 diff. The problem is that second gear (3speed box) which was already too low, becomes even lower. The same is true for a four speed box. Making Austin 7s go fast is as much about gearing as it is engine tuning - you have to get it right. It matters not whether you use 17in wheels or a different axle ratio, the change to top gear speed will be the same,but it's the spacing of the intermediate gears you really need to sort. So, what I'd do - 5.25 or better, a 5.625 and stick with 19 in wheels (why? - they look nicer), but then swap the box for one with Ulster ratios. This will be ok for most places, but then if I was getting serious I'd have 17 and 16 inch wheels as well, because it really is all about gearing, and the more options you have, the better

[Steve Jones]

The problem you have is not with top gear, but the intermediate gears. 3.50x17 wheels with a 4.9 diff will give more or less the same gearing in top as 3.50x19s and a 5.25 diff. The problem is that second gear (3speed box) which was already too low, becomes even lower. The same is true for  a four speed box. Making Austin 7s go fast is as much about gearing as it is engine tuning - you have to get it right. It matters not whether you use 17in wheels or a different axle ratio, the change to top gear speed will be the same,but it's the spacing of the intermediate gears you really need to sort.   So, what I'd do - 5.25 or better, a 5.625 and stick with 19 in wheels (why? - they look nicer), but then swap the box for one with Ulster ratios. This will be ok for most places, but then if I was getting serious I'd have 17 and 16 inch wheels as well, because it really is all about gearing, and the more options you have, the better

Unsurprisingly, I agree with what Alan says. My car which does OK but hasn't the most highly tuned engine out there has 3.50 x 19 tyres with a 5.25:1 CWP and 'fake' Ulster C/R 3 speed gearbox ratios. It's OK for most places but better for hillclimbs than sprints (and we do more of the former than the latter). Second gear is excellent and is the one used for most of the time on most of the hills we do. Only time I use top is on some sections of the longer hills on the Isle of Man. For sprints it's a bit different and I do have to use top. I don't, really, like to as gear changes cost time but it's either that, rolling off the throttle a little or revving the engine to places I don't want it to go to!! Snetterton Sprint next weekend will be something of a challenge in this respect!

Steve

[Alan]

The other possibility of course is really low gearing. Say 5.625 with 3.50x16 tyres. That will put top only slightly higher than 2nd with a 4.9, 3.50x19s and a c/r box. That way you get a really useful set of gears for Shelsley or Loton.

[Charles P]

I wasn't really thinking about VSCC rules but more about what looks right on an Ulster.
I'm in agreement with the general thrust and a CR box is the best mod to make a 3 speed Ulster more fun.