Heh Matty said that the only problem he has "is the really low gearing" so I assumed he wants higher gearing.

Glad we got that all sorted out

Just to avoid confusion, the 1.4's 3.82 diff is the lowest geared diff available, the rest will all give higher gearing, right? See you were right to begin with Chris

The size of the wheels make no diference i`ve found. The wellers on 175/50`s are about half an inch smaller than stock steels with balloon tyres.

I need to up the ratios slightly so i can stay in second for longer so i think i need the highest ratio diff i can get. The difference between the highest and lowest ratios that fit won`t be massive anyway but might make it worth it.

Would it not be better to lower the gearing, and use third gear instead of second?

Tyre size will certainly affect the overall drive ratio. Of course it's not the wheel size that matters (as the depth of the tyre side wall must be taken into a/c), but the circumference of the tyre.

Think of tyres on the road as a rack and pinion gear set up. If the circumference of the tyres (cog) is twice as much (twice as many teeth) the wheel (cog) will travel twice as far after one revolution. Thus at any given engine speed, the car will travel at twice the speed.

Of course we aren't taking about doubling the wheel size, but a couple of inches will certainly cause a few percent difference. For example 13" wheels with 175/50's will have a circumference of 62.5 inches compared to 68.8 inches of 15" wheels with 175/50's. That's about 10% lower.

This site can be used for tyre size calculations http://www.miata.net/garage/tirecalc.html First found by Mick I believe, good find

Yeah i`m with you but running 15`s isn`t an option because i`ve tried them and it just doesn`t happen really! LOL! Also i found that again it made no real difference. I used vauxhall steelys with some half decent rubber (195/50 i think it was) and it had the same roling radius as boogo steels and tyres so was only just bigger than wellers and nice tyres.

Lowering the gearing isn`t an option either because judging from this thread i have the lowest there is?

Yeah, I'd be tempted to say a 3.36 out of a 360 GLE... especially as you have the power for it. will give you another 15-20% in second.

mattyboi wrote:
Lowering the gearing isn`t an option either because judging from this thread i have the lowest there is?

I know a man with a 4.78/1 for sale.

Chris_C wrote:I'm either redlining in second, or not quite on the power in third a lot of the time.

Stock 1.7s have an extremely wide torque band, so there's probably something wrong somewhere with either the fuelling or ignition to cause that. Also the distinct smell of petrol whenever I follow you gives another hint to your problem

A disadvantage of large carbs is that you can lose low down torque too.

sven360 wrote:I know a man with a 4.78/1 for sale.

Hey... I have potential dibs on that

pettaw wrote:Stock 1.7s have an extremely wide torque band, so there's probably something wrong somewhere with either the fuelling or ignition to cause that. Also the distinct smell of petrol whenever I follow you gives another hint to your problem

Shush No, I agree, my car isn't making what it should at the moment. But, it was doing this when I got the good dyno reading, i.e. damn nice torque figures, and I still have a fair amount of low down grunt, though I reckon I'm down 10%ish all over atm according to the butt dyno. When I can get the thing on my drive for a week or so and I can play with it then I'll suss it out. Also now needs a service, so I bet half my sparks arn't making it through either

Put a vario on it

Chris_C wrote:Yeah, I'd be tempted to say a 3.36 out of a 360 GLE... especially as you have the power for it. will give you another 15-20% in second.

Cool, best keep my eye out for one then! now where`d i put the breakers number.....................

Just looked at it, and you'll get about 13% more. From what I remember (it's been 18months/30,000 ish miles since I drive my 1.4) you'll find second at 5,500 is about 35-40mph (or equiv drifting amount), so you'll have about 40-45ish.

Well thankfully I'd imagine the 16v to give a fair few more RPM... so should get 60 in 2nd with the tall final drive.. I think?!

So the next question is...........is it easyer just to bang in a gearbox and diff from the glt as a whole or just get the dif?

I've never done a 300 diff, but a lot you have to get loadings set perfectly else they shred. Lots of peeps have done 300 diffs though, so can tell you more!

Gearbox... I seem to remember isn't many bolts, but you'd have to fight the halfshafts!

Definitely do the g/box and diff combo. I think you can change the input plate on the front of the g/box to adapt from a 340 one to a 360, but not 100% on that one.

Changing the diff is do-able, but its a real PITA, because the g/box and diff are joined right together, and you need to carefully set all the preloads etc on the shafts joining them. If you don't do it right, you can screw up the diff and g/box.