Gearbox's and Ratios

[Tyler]

Right i am going to bite the bullet here and ask asilly question... (as usual)
Can i ask someone to explain gear ratio's in as simple form as poss... I am looking for a box that has different ratios to the UK My98's, i want something that is a little more aggressive but not limited to 120mph like my mate had in his old classic... I am looking at a 555 gearbox...

[andy-m]

hav you tried just inputting ratio's for boxes in to the cathrin and ken speed calculator? i'll fnd the link in a sec

[andy-m]

here:-
http://www.catherineandken.co.uk/sti/tyres.html

i use that and the transmission chart I gave you the link for the other day to work out top speeds

[Tyler]

Cheers Andy its just the box's i have been looking at dont have no information on them (typically)

[andy-m]

well the fist part of your question, explaining gear ratio's, you ever been on a mountain bike?
low ratio gear makes it easy for you to pedal up hill, but you dont have a high top speed. a high ratio gear has a better top speed, but is a lot harder to pedal.

so if you have 2 cars, both identical except one has a low ratio box and the other a high ratio box, the one wil the low ratio box will have a quicker 0-60 time but a lower top speed than the car with a high ratio box.

if you want a better top speed, but the quicknes of a short ratio box, some people fit a UK 5th gear in low ratio jap boxes aparently. dunno how good it is though as i aint experienced it myself

[Tyler]

Andy you are a diamond buddy, thank you... Yeah i have herd about this... What is with the final drive bit?? Mine think my old uk box was supposed to be 4.11 final drive... but the ones i have been looking at are 4.44... So is that also the same principle as what you explained..

[andy-m]

not necesarily.
if you are comparing 2 boxes with the same ratio gears but different final drive ratio's then yes, the principal will be as i described.
however, a box with a 4.111 ratio final drive and one with a 4.444 final drive may have diferent ratio's for the gears to each other so that the end result is the same.

go back to that link for the speed calculator. with the default numbers in, final drive is 4.111, 5th gear has a ratio of 0.825 and when you hit the calculate button, you get 158mph as top speed in 5th.
now if you change the final drive ratio to 4.444 and the 5th gear ratio to 0.76, you get the same speed.

i think it was Grand Tourismo 5 on the PS2 where I started mucking around with gear ratio's. A high speed track like the ring lends itself to a long gear set as top speed was more important than how quickly you get to that top speed.
Monza with all the twisty bits was the opposite. short box was better because it wasnt about how fast you could go, it was about how quickly you could accelerate.

[Tyler]

Wow thanks Andy that is quality, thanks Andy.. Gearbox's and ratios i could never really understand but your explantion and links were a great help... Was it you that brought the P1 box buddy??

[andy-m]

yep, was me. i'm collecting it sunday & jaffa is fitting it for me next saturday.
for me, its a longer gear set than what I have so my 0-60 wont be as good as my current JDM box but i'll have lower RPM at higher speeds and as I use it every day to get to work doin 50mph most of the time, it was a better choice for me than getting another low ratio box.
and judging by the car it came out of, its been well looked after !

[Tyler]

Deffinatly buddy, got yourself a real ggo deal there...



What are peoples thoughts on this?
http://www.ebay.co.uk/itm/2006845397...84.m1438.l2649