Plunky
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| posted on 26/11/16 at 04:16 PM |
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245/40/15 Tyres
Hi,
I've managed to get hold of some genuine Caterham wheels for my F27.
The tyres haven't got much life left in them.
The rears are very wide, 245/40/15, can anyone recommend where I can get some tyres of this size from? Not having much luck at present...
Cheers
Liam
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CosKev3
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| posted on 26/11/16 at 05:45 PM |
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Have you tried a wheel on the rear to make sure it clears arch?
How wide are the wheels?
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rodgling
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| posted on 26/11/16 at 07:27 PM |
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That sounds unnecessarily wide... how much power are you running? I find 225 fine with 320 bhp
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Plunky
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| posted on 27/11/16 at 10:46 AM |
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They fit perfectly on the rear to be honest.
I might go down in size if I can't find any direct replacements.
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jeffw
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| posted on 27/11/16 at 10:52 AM |
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The tyres will almost certainly be Avon CR500s in 245/40 15". Avon also do the same size in ZZS tyres which are the CR500 replacement.
[Edited on 27/11/16 by jeffw]
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Plunky
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| posted on 27/11/16 at 10:53 AM |
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I am only running a 2.0 zetec, so not big power at all.
I thought as long as the fronts arnt too wide (which they're not), I would be ok. Surely the wider get better on the back?
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jeffw
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| posted on 27/11/16 at 10:55 AM |
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I assume the rims are 6J or 7J front and 8J rear. Probable too much for a low powered car but if you can afford to put the right tyres on it then no
troubles.
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Plunky
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| posted on 27/11/16 at 11:13 AM |
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quote:
Originally posted by jeffw
I assume the rims are 6J or 7J front and 8J rear. Probable too much for a low powered car but if you can afford to put the right tyres on it then no
troubles.
I believe they are 6.5j front and 9j rear!
I just see it as future proofing! 
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jeffw
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| posted on 27/11/16 at 12:21 PM |
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You can look at it like that. Give I run 8J rears with 400BHP you might call it overkill....
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Matt21
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| posted on 27/11/16 at 12:29 PM |
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Wider is not always better.
Lets say the rear of your car weighs 550lbs (250kg)
and the rear contact patch of a 195 width tyre is around 30.8inches squared (for the two rear tyres)
The force on them is ~17.8psi
Using the same weight, but a 245 width tyre, the contact patch is about 38.4inchs squared
The force is ~14.3psi
So you get less force on the tyres, the wider you go the less force, if you get to a point where the force isn't enough to allow the tyre to
perform properly then you won't get the grip you need.
Same goes with too skinny tyres, you'll get too much force and damage the tyres.
You may find that 14.3psi is the optimum pressure to exert on the tyre to get the best performance, you it may be that you need 18psi or whatever
[Edited on 27/11/16 by Matt21]
Instagram: @matt211988
Photobucket
My YouTube
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sdh2903
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| posted on 27/11/16 at 12:31 PM |
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You might change your mind with the 245s when you get a price for them.......
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Matt21
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| posted on 27/11/16 at 12:41 PM |
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Just to add another bit to my mathematics.
Those figures are at a standstill, you may find your car generates uplift when its doing 60mph, which reduces the force, or it may have lots of down
force and increase the force...
who knows 
Instagram: @matt211988
Photobucket
My YouTube
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jeffw
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| posted on 27/11/16 at 02:52 PM |
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quote:
Originally posted by sdh2903
You might change your mind with the 245s when you get a price for them.......
This was kinda my point as well.
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Plunky
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| posted on 27/11/16 at 04:47 PM |
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Thanks for the info guys.
I'll see what prices I get... can always go slightly thinner
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DW100
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| posted on 27/11/16 at 05:23 PM |
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Listed here,
http://bmtrracing.com/size-price-list/
£144.60 + VAT and carriage each
[Edited on 27/11/16 by DW100]
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