OK, I have read a lot about tyre sizes the last days here, and I thought it
would be wise to throw up the different alternatives on tires:
The circumference of the standard 2000 tyre should be equal to 175/13
standard 80 percent height/width ratio):
(13 inches + 2 x (175cm x 0.8)) x PI = 191.7 cms
For the 2500:
(13 inches + 2 x (185cm x 0.8)) x PI = 196.7 cms
With 185-70 on a 13'' rim we get:
(13 + 2 x (185 x 0.7)) x PI = 185.1 cms, in other words too small for BOTH
2000 and 2500...
With 195/13 (if that dimension exists, I doubt that)
(13'' + 2 x (195 x 0.8)) x PI = 201.8 cms
With 195-70/13 on a 13'' inch rim we get:
(13 + 2 x (195 x 0.7)) x PI = 189.5 cms, too small as well, but pretty close.
I think going above 195 (or even including 195) combined with low profile
and 5 inch rim would deform the tyre and give uneven wear and even less
road holding. 195-70 seems like the sensible choice for 2000, 2500 is more
difficult.
OK, then we switch to 14'' rim (standard 2500S alloy rims):
175/14 gives
(14'' + 2 x (175 x 0.8)) x PI = 199.7 cms, too much for both 2000 and 2500.
185-70/14 gives:
(14'' + 2 x (185 x 0.7)) x PI = 193.1 cms, good for 2000, but too small for
2500
195-65/14 gives:
(14'' + 2 x (195 x 0.65)) x PI = 191.4 cms, spot on for 2000, too small for
2500.
195-70/14 gives:
(14'' + 2 x (195 x 0.7)) x PI = 197.5 cms almost spot on for 2500.
Of all these dimensions, the 185/70-14 is the most easily obtained and can
be found pretty cheap as there are a lot of cars using them.
And almost all these dimensions stay within 5 percent of the original size.
This is acceptable I think, we're not talking about big deviations from the
original size.
I have used 185/70 with my 13'' rims for my 2000, and these work nicely,
even wear etc.
I have also used a set of 195/70, but these wore down badly, but that might
be down to the fact that I had suspension anomalies at that time.
I think that 175/13 can still be found, but 185/13 has been removed from
the market (here in Norway anyway).
I have recently bought 4 alloy 14'' rims and would like to buy 185/70 for
those as this dimension is readily found and cheap as well. And alloy rims
give better grip because of the decreased unsprung mass.
I hope that this was to any help...
And BTW, please correct me if I am wrong. I am a bit uncertain about how
wide a tyre you can fit to a 5 inch and 5.5 inch rim...
I know that some firms widen rims, perhaps this is an alternative for the
2500 (I think that some 2500 models used the 175/13 as well) owners. 6 inch
rims make it possible to fit wider tires, and thus getting close to the
original size. But then, the triumph should NOT have extreme low profiles,
it doesn't look good I think.
---Asgeir---
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