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[2woody]

I thought the 5th gear speeds were on your current tyres. Never mind, I'll have a look-see if  it makes any difference.

[2woody]

very good explanation for R25 and R28 but what about R30 fitted to 2.2 dti and 3.2 V6 manual (police only) ? whats different on this box compere to other 2 boxes

thanks

never heard of it !

R25 and R28 only differ in the actual gears, so I assume shot-peened. Certainly bearings and synchro rings are the same.

[2woody]

I thought the 5th gear speeds were on your current tyres. Never mind, I'll have a look-see if  it makes any difference.

No, it doesn't really.

I've worked out what you thought you had when you did the 5th gear figures, so that's the 245 tyres, a 3.9 diff and the wide-ratio gearbox.

you measured the following

70mph = 3000 revs in 5th
80mph = 3400 revs in 5th
90mph = 3800 revs in 5th

what you should have measured if indeed you had the configuration that you thought

70mph = 2911 revs in 5th
80mph = 3327 revs in 5th
80mph = 3740 revs in 5th

As you can see, we're only talking less than 100 revs here, which is well within error of rev counter or our (my) matching of trends to measured figures.

The one thing that does stand out is the 4th gear figure, so I remain convinced that you have 3.7.

Anyway, this post was about improvements - fitting the 3.45 diff and correcting your tyre size will definitely do that.

On the subject of tyres, that's something else I need to look up. What I can say is don't use an on-line calculator, I can guarantee it'll be wrong !

[2woody]

I can find the following :-

235/35 at 823 wrpm
265/30 at 818 wrpm
275/30 at 811 wrpm

all from the Falken catalogue

they'll tramline mind you.

[Zippy2012]

I thought the 5th gear speeds were on your current tyres. Never mind, I'll have a look-see if  it makes any difference.

No, it doesn't really.

I've worked out what you thought you had when you did the 5th gear figures, so that's the 245 tyres, a 3.9 diff and the wide-ratio gearbox.

you measured the following

70mph = 3000 revs in 5th
80mph = 3400 revs in 5th
90mph = 3800 revs in 5th

what you should have measured if indeed you had the configuration that you thought

70mph = 2911 revs in 5th
80mph = 3327 revs in 5th
80mph = 3740 revs in 5th

As you can see, we're only talking less than 100 revs here, which is well within error of rev counter or our (my) matching of trends to measured figures.

The one thing that does stand out is the 4th gear figure, so I remain convinced that you have 3.7.

Anyway, this post was about improvements - fitting the 3.45 diff and correcting your tyre size will definitely do that.

On the subject of tyres, that's something else I need to look up. What I can say is don't use an on-line calculator, I can guarantee it'll be wrong !

prob my eyesight as the rev counter doesnt have 100rpm marks its slightly harder to work out bang on accuracy as you know, but ide say you are bang on right!! 
im wondering if fitting the 19s will be a mistake hard ride etc but should corner well tho...
only time will tell this weekend....
so can you just confurm kevs post that a 2.2dti & 2.5tds have the correct 3.45.1 rear diff?? & will saloon diff fit estate??? 

Cheers for your time 2woody defo a valued OOF member!!! 

[Kevin Wood]

I can find the following :-

235/35 at 823 wrpm
265/30 at 818 wrpm
275/30 at 811 wrpm

all from the Falken catalogue

they'll tramline mind you.

275/30 Falkens. <bides his time until Chrisgixer sees that> 

[aaronjb]

275/30 Falkens. <bides his time until Chrisgixer sees that> 

Heh - funny that, I just spotted what the M3 is currently shod with and very nearly took a picture just for Chris..

[Zippy2012]

i got a full set of conti in 19s that im going to fit, but looks like 2mro now because my mobile tyre mate coming at midday 2mro 
just debaiting which rears to fit... 275 30 19 or 275 35 19??

ummm.... 

[Kevin Wood]

275/30 Falkens. <bides his time until Chrisgixer sees that> 

Heh - funny that, I just spotted what the M3 is currently shod with and very nearly took a picture just for Chris..

 

At least other drivers will be expecting that to randomly change lane without indicating.

[Zippy2012]

chris's bmw..?? all beemer drivers are like that 

on the 245s i had to use the mid lane most of the way up m5 to bham because if i used lane 1 i had 2 choices hard shoulder or lane 2!! didnt even tramline in that lane because of the wide omega track it couldnt make its mind which lorry rutt to stick in!!!

[2woody]

3.45 definitely 2.5 diesel manual and auto and 2.2 diesel manual ( there's no auto )

I only used Falken as the example as they are rare amongst tyre manufacturers in publishing wheel revs per mile figures.