Fred W B
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| posted on 21/7/07 at 08:01 AM |
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What size tires for my new rims on CANAMSA?
After much deliberation, as in this thread,I finally ordered 7 and 8J 15"
Superlites from Performance Wheels in Leicestershire, with the centers painted in charcoal colour. Cost 348 Pounds
The wheels had to be special ordered from Performance Wheel's supplier in Australia, then once in the UK they waited to meet up with some other
items and were finally transported to SA. I had to resolve a small problem with the customs people when they wanted to know why I was importing
flammable "superlight charcoal". 
Now I have then in hand, what size tire do I want? Depending on what I can source locally, I was thinking 205/50 on the 7J's on the front and 225
or 235 / 50 on the 8J's on the rear. Or maybe a 60 profile on the rear?
Cheers
Fred W B
 
superlights
[Edited on 21/7/07 by Fred W B]
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RazMan
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| posted on 21/7/07 at 08:32 AM |
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Fred, I would have thought you need a lower profile on the rear to keep the rolling radius the same as the front.
Possibly something like a 235/45 if they exist?
Lovely wheels btw 
[Edited on 21-7-07 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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ecosse
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| posted on 21/7/07 at 09:04 AM |
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Going by the tyre bibles width recommendations I would aim a bit bigger on both front and rear tyres sizes, probably 225 front and min 245 rear.
Tyre Bible
Look for "rim-width calculator" about halfway down
Cheers
Alex
PS
The wheels look good
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ned
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| posted on 21/7/07 at 09:10 AM |
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Look in keeping with the historicness of the car I'd of thought you'd want a taller tyre wall, also 15" isn't a huge wheel for
a big car so it would help to beef out the arches a bit imho.
Not read all your background but presumably you know what size wheels/tyres the original cars used?
Ned.
edit: what sizes do GD run on their cars?
[Edited on 21/7/07 by ned]
beware, I've got yellow skin
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Fred W B
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| posted on 21/7/07 at 04:46 PM |
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The original T70's started out with 15" 8J and 10J wheels, with tall profile tires. Nowadays a lot of GT40 reps and the GD T70's
are fitted with very wide 17" rims and very low profile tires. Seems you have to choose between optimum performance and correct period
appearance.
I decided to buy 7J and 8J to avoid the expense of split rims. The local guy who supplies racing type road legal tires reckons the optimum size for
race handling is 195/50's on the 7J and 205/50 on the 8J. I am not worried about trying to get the period look exactly right, and while I do
want the car to perform well, I think these sizes might just look silly. I'm not worried about having a bigger rolling radius on the back.
I haven't yet spent much time looking at what's avalable, as I suppose it will come down to what I can get. 225,s, 235,s and 245,s
don't seem very common, at least in 15".
Cheers
Fred W B
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thomas4age
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| posted on 23/7/07 at 07:32 AM |
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Hey Fred,
I agree with you on the 15" vs 17" debate, i looked at the GD wheels also but they just don't seem right in a way.
Just make sure that the tyres have enough flesh to take the rim (that varies if you go superwide on narrow rims an vise versa) with enough torque and
traction you can spin a wheel inside a tyre.
anyway supurb choice and colour wheels for the car, I asume yours will be red?
grtz Thomas
If Lucas made guns, Wars wouldn't start either.
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Fred W B
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| posted on 23/7/07 at 11:09 AM |
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Hi Thomas
Yes, I want my car to be a deep blood red with silver stripe, just like this car.
Cheers
Fred W B
 
red/silver
[Edited on 23/7/07 by Fred W B]
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Fred W B
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| posted on 23/7/07 at 11:22 AM |
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Something like this, but redder. This is too much towards maroon for my taste.
The car is a one off RCR with coupe style nose and tail.
Cheers
Fred W B
[img][/img]
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Doug68
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| posted on 23/7/07 at 12:48 PM |
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Off topic but... I've seen this come up a few times and for the life of me can't work out any sensible reason why anyone would care if the
front and rear rolling radii are different?
Assuming of course the suspension has been designed around the tyre selected.
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Fred W B
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| posted on 23/7/07 at 01:25 PM |
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I think that it gets brought up when dealing with tyre suppliers more used to the chav element , who want to "upgrade" shopping cars by
fitting the biggest possible rim size.
Keeping the same rallling radius would avoid changing the gearing or speedo calibration.
That said, what chav understands those concepts?
Cheers
Fred W B
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RazMan
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| posted on 23/7/07 at 05:19 PM |
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I'm not absolutely certain on this point but using different sized tyres can make quite a difference when setting up corner weights and can
compensate for ride height anomalies...... I think
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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v8kid
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| posted on 23/7/07 at 08:17 PM |
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Fred,
Relative tyre width front to back can depend on the weights on each axle the heavier end having pro rata more width. Corse thats assuming that the
springs and rol bars are set up this way as well.
Then theres the weight transfer to consider under braking which requires more performance from the front tyres - if the center of gravity is low its
not so important it its high then its a big issue.
Then there is acceleration requirements if you have a beefy motor, like a stonking great big V8, preferably Rover, you need bigger rear tyres
instead.
Then if you are trying to compensate for idiosyncracies in the suspension setup you have to fiddle about with it as well, then there is the drivers
skill can he cope with oversteer or play safe with understeer?
What about wet weather conditions?
Just put the tyres on and try it out on the track - I went for tyre size pro rata to weight distribution and was absolutely amazed that the blessed
thing works OK. Will still want to change tyre size just to see though.
Now who's car is there in the car park with similar size wheels I wonder
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gazza285
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| posted on 25/7/07 at 08:35 PM |
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When I had 15x8" rims on my bubble arched Mk1 Escort I ran 205/50 on the front and 205/55 on the rear. It looked ace, just haven't got any
pics..........
DO NOT PUT ON KNOB OR BOLLOCKS!
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