tyre calculating program

polo2k · Post by **polo2k** » Sun Mar 23, 2003 6:47 pm

ive just found this link while looking on another forum and i thought it might be of some use to someone, somewhere
http://www.sgmotorsports.com/tiresize.htm
the only think is that you need to know the rim diameter in mm
the width is the first part of the tyre size
aspect ratio is the second part (its a percentage of the width so if its 100 then the sidewall hheight is the same as the width)
and then the third bit is the rim diameter in inches
so:
195/50/15
means
width 195mm
sidewall profile 50%of width
15 is the rim diameter

Speedlaw · Post by **Speedlaw** » Sun Mar 23, 2003 8:35 pm

Good one, I use this too. Pretty comprehensive as well. I found out my new wheels are actually better matching to the stock size than the 14's I had.

Better!

polo2k · Post by **polo2k** » Sun Mar 23, 2003 9:14 pm

have you noticed any detrimental performance issuses after going to a wider tyre cos normally you loose a bit of top end i know i did (about 30km/h)

Speedlaw · Post by **Speedlaw** » Mon Mar 24, 2003 10:01 am

That much?

Wow. I haven't really yet, but they're only 10mm wider than what I had. I did found that it didn't go as fast beyond 160 (kmh) than I expected. But I don't go that fast that often. Honest.

Up until 140, 150, I noticed no difference.

*fingerscrossed*

polo2k · Post by **polo2k** » Mon Mar 24, 2003 11:39 am

yeah i know up to about 180 she pulls but then its like hitting an aerodynamic limiter

Speedlaw · Post by **Speedlaw** » Mon Mar 24, 2003 12:58 pm

I'll give it a go when I'm in Germany again, do a couple of runs in different directions, see if it's changed.

So far I haven't notice a change at all, luckily.

Nelson_Wilbury · Post by **Nelson_Wilbury** » Sat Mar 29, 2003 5:21 pm

That was extremely helpful

Thanks Polo2k

polo2k · Post by **polo2k** » Sat Mar 29, 2003 6:12 pm

no problem buddy just remember that im here to help

polo2k · Post by **polo2k** » Sun Mar 30, 2003 7:38 pm

and to get the wheel size in mill then go here http://www.convert-me.com/en/convert/length

Nelson_Wilbury · Post by **Nelson_Wilbury** » Thu Apr 03, 2003 8:01 pm

OK,

NOTE: New Speedometer Reading = What speed the car will need to go (with the after market tires on) to be traveling at the same speed if the car had the orginal tires on.

So this bassically means if I put smaller tyres on the car will be slower??

Bassically, this is what I wanna do...

Current tyres...
195/55/R15s

Tyres I want...
205/45/R15s

So at 60mph the new car will need to be going at 63.18mph to achieve the same speed? Wouldn't that make the car slower to accelerate

and if it did what tyres could I fit to make it faster??

Sorry, I'm confused, LMAO

polo2k · Post by **polo2k** » Thu Apr 03, 2003 8:51 pm

well if the overall diameter is LARGEr then you will need more torque to achive the same acceleration but if the overall diameter is SAMLLER then you will accelerate faster but if i were you id go you 195 50 15`s as they will heat up a little faster so grip sooner and there a lot cheeper

Speedlaw · Post by **Speedlaw** » Fri Apr 04, 2003 1:34 pm

Smaller tyres (in diameter) means quicker acceleration (in true MPH) and an odometer that reads too fast.

And vice versa.

polo2k · Post by **polo2k** » Thu Apr 17, 2003 9:09 pm

well if your going 195/55/15`s then here is the relevant info
side wall-on the 205 it is smaller so this means a smaller overall diameter
width-slightly wider (10mm) which can be a bit if you like to push it
diameter- again the 205 is smaller
circumfrence- yet again smaller
conclusion-:in all you end up with a slightly amaller diameter so acceleration would be ever so slightly better but not really worth thinking about all you would gain by this would be a little width
the difference is .3% so your ok as far as that goes as the limit is 2% if your gunna be sensible
the only dis advantage to this would prolly be unsprung weight because if you get identicl tyres (make. model. and speed rating) there is more rubber on the 205 so there fore its heavier which can heve adverse handling affects (however i sholdnt imagine that the difference would be noticeable on a street car)
another thing to concider is upping the speed rating as i never put a tyre less than v rated on my polo as the higher the speed rating the stiffer the sidewall (i.e. ZR is rock solid where as H is flimsy)