would smaller tyres have similar affect as higher ratio diff gears?

[zskinner]

hey so im looking into getting some 3.45 diff gears, but i had a thought...... if i changed my rear tyres from the stock 205/65 r15 to lets say 195/55 r15, the diameter of the wheel would obviously be alot smaller. so my question is would fitting this size tyre have the same/similar affect as fitting say 3.45 diff gears? cos the car would probably have a tad bit better accelaration, as well as rev a bit higher at speed, and the speedo would also be out a fair bit. what do yous reckon? anyone done this?

[ybl8te]

i know when i ran 40 profile on my 17" i could sit there all day from one end of my "drive way" to other doing burn outs......did notice my rev counter sitting higher at 100km and my fuel bill went up.......quick gear changes also

[vk.jonno]

Well, no. I highly doubt it would change much at all.

[zskinner]

i dont expect it to change alot, just a little (of course to get a real difference you'd need even smaller tyres). just wanna know if im on the right track and if it might work is all.......

[Brett_jjj]

Years ago I used to fit 14 inch 265/50 and 245/50 bridgestone eager tyres to my falcons,they were a bit smaller in diameter than the standard 14 inch tyre but a lot wider,and it would effect the speedo reading by heaps.It would read 20-30 km/h faster,so it definitely has a similar effect to changing the diff ratios.

[soop]

To the OP, yes it does change the final drive. Not to the extent that a 3.45:1 diff would how ever. You won't really notice the difference, unless you went really small, and then I'm fairly confident that it's illegal.

ybl8t, stop smoking crack.

[hakhawk]

Tire size calculator

changing down to a 195/55 will not only change the speedo, but will most likely also put you over the legal 15mm max diameter change. get diff gears and do it properly

[minux]

so this site is run by whom - you. ok should i rewrite my post so it does'nt offend your non like for burning rubber

"from memory i thought my rev counter would do 2100rpm at 100km/h with 40 profile now running 45 profile and sitting on 1700rpm @ 100km/h - there was a difference for me......."

I hope that's better reading for you------am sorry to up set you

If you do not stop posting absolute crap I will just ban you. If you do not liek the site rules, there is a little button top right of your browser that says Log out. I suggest you use it and do not come back.

[zskinner]

Tire size calculator

changing down to a 195/55 will not only change the speedo, but will most likely also put you over the legal 15mm max diameter change. get diff gears and do it properly

ah true, didnt realise there was a law like that well thanks everyone for your replies, but my car gets too much police attention as it is so i'd rather keep it legal and roadworthy and out of trouble lol guess ill start searching for some new diff gears. cheers again for everyones help

[Lost_Pete]

A quick look at the tyre calculator;

205/65 15 vs 195/55 15 is a 8% change

This would be the same as changing your diff from 3.08 to 3.32

A friend of mine did this a long time ago and he did say you could notice a difference.

185/75-14 5.5in 12.5in 24.9in 78.3in 809 0.0%
195/55-15 4.2in 11.7in 23.4in 73.7in 860 -5.9%