Tyre size calculator help please

Post by **jaymo** » 26 Mar 2008, 21:39

Please help me, I'm going out of my mind

So let me get this right. The tyres that are fitted as standard to a T25 Caravelle are 185/70/14 97 R and have a 5.5"J width rim? Or is it 205/70/14 97 R?

The new wheels I have are JK's 17" which are a 7J width, so am I right in saying that in a tyre size calculator, I enter 185 70 14 in the 'current' tyre size fields, and then in the 'new' tyre fields, enter the relevant width for the new rim first, which to fit needs to be between 195 and 215, then the profile height, which in my opinion needs needs to be 50, then the rim diameter which is obviously 17"?

If all that is correct, and I enter, for example, 185 70 14 in the 'current', and 215 50 17 in the 'new', I get a difference of 3.61% and + 22mm in diameter, which if I was travelling at 70mph would add 2.53mph to my speedo reading.

If my calculations are wrong, or I'm using the tyre calculator incorrectly, then some help would be great, before I end up losing my mind and being taken away by the men in the white coats.

Mark

Post by **kevtherev** » 26 Mar 2008, 22:02

man in a white coat here....

your calculations are fundamentally flawed...

VW fitted 185/82 X 14C originally

so a 225/50 X 17 would be a closer fit for the speedo accuracy

an ET between 30 and 39 would be ideal

7 1/2" is the limit on the fronts as it is very close to the suspension and wheel arches

Post by **jaymo** » 26 Mar 2008, 22:16

Thanks Kev. I feel my sanity returning

The calculator thingy makes a bit more sense now.

I was entering the spec from a Transporter Manual, which states the tyre size is 185/70/14, but I'd rather take the word of the guys on here than the manual I have, which is obviously misleading.

Post by **kevtherev** » 26 Mar 2008, 22:22

I have used Brickyards calculator...here

click here

Post by **toomanytoys** » 26 Mar 2008, 22:28

I doubt a 7.5j will go on even with an et of 30... I could be wrong though... std rims are 39 and there aint much clearance on them...

Post by **jaymo** » 26 Mar 2008, 22:29

Excellent!

Thats more accurate than the calculator I've just been using, as it gives an 82 profile.

I'll be able to get my tyres sorted now.

Many thanks Kev.

Post by **jaymo** » 26 Mar 2008, 22:35

The wheels I have are 7J, so they should be fine, shouldn't they???

Post by **kevtherev** » 26 Mar 2008, 22:44

Yes Simon they are the limit and you would probably have to ignore the ET to get them on

I think 16" is enough personally

7j is ok what about these rims what they off?

Post by **jaymo** » 26 Mar 2008, 22:50

I've bought a set of the Just Kampers 17" wheels, simply to save on buying other wheels and having to have them machined, and they do look really nice.

I'm not sure what the ET of the wheels is though. I think I may have seen somewhere on here that they are 23, but still don't know if thats correct.

Post by **kevtherev** » 26 Mar 2008, 22:55

Wheels with a ET of less than 30 tend to stick out more and give the vehicle a feeling of not wanting to do much more than going in a straight line, wheel bearing load will be increased, steering will be heavy and the tyres will wear more on the inside edge and in my eyes are to be avoided.

best make sure then...otherwise you'll be paying out on tyres...a lot

and the slider might not pass the rears without a door mod

Post by **jaymo** » 26 Mar 2008, 23:04

Yep, will definately check.

So if the wheels do have an ET of 23, can I correct it with spacers?

Post by **kevtherev** » 26 Mar 2008, 23:05

Post by **jaymo** » 26 Mar 2008, 23:08

Ok,

Thanks for all the advice Kev, much appreciated.