Thread: compensating for larger tyres

Originally Posted by DirtyDawg

Would running 4:1 diffs and a rock crawler T/C compensate for loss of low gearing by using 34"'s and above?? should do but what have you guys done to get back your snail pace low???

i had 4.7 ring and pinions on my 90, due to the 35' simex. They we Kam ones so alot stronger than Seris ones. The ones on the left are the 4.7's

Originally Posted by LandyAndy

Hi Mick
Have the 4.11s improved fuel economy and performance at highway speeds??????
How accurate is your speedo????
Andrew

Hi Andrew

As I changed tyres from standard to 32" plus the 4.11's fuel economy has dropped off slightly, but then I have also chipped it and added a few other things like bull bar etc all in a short space of time so where as before I may have got about 1000k's out of the 95lt tank, I know get about 800 - 850 depending on highway or round town.
I had the tyres fitted first and as mine is a manual I noticed immediately that it was very sluggish off the lights, but okay on the open road due to the revs not being as high. My speedo was about 10% out so I fitted a Truspeed correction unit which now brings my speedo back to accurate - very accurate in fact as confirmed by a GPS.
Mine is a manual so I would probably feel the gearing shortfall faster than an auto, certainly off the lights anyway. The torque converter in the auto would make up for the short fall slightly. It's in low range that you will really notice the difference. 1st gear low for me was quite frightening at first without the 4.11's......it motored along and I was constantly on the brake going down hill.
Now with the 4.11's fitted 1st low is very good indeed as it now travels slower than it did when standard (4.11's should take a car with 33" tyres back to standard) 2nd low is also good although the more hard driving I do I sometimes wish there was a gear between 1st & 2nd low as on very steep loose stuff, 1st is sometimes too low and the car wants to slide and 2nd low is too fast.......but then I am a stickler for perfection and am constantly trying to find perfection

Anyway, to answer your question in simple terms, all the mods I have made have definitely not enhanced fuel economy but then this is not a huge concern for me as it is still pretty good really....I worked out a while ago that with my current set up I am getting about 11.5 12lt /100k....I'm happy with that.

Hope this helps, Mick

Mick

With 32s and 4.11s the vehicle is overgeared too much...

For those disco owners wanting to run a 32 I suggest a 3.9 gearset...

It pairs beautifully with the 32s on a Disco.

PM if you want more info

Originally Posted by tombraider

Mick

With 32s and 4.11s the vehicle is overgeared too much...

For those disco owners wanting to run a 32 I suggest a 3.9 gearset...

It pairs beautifully with the 32s on a Disco.

PM if you want more info

What do you mean over geared exactly?

How do you guys get this economy my best was 11.3/100, that was on a flat stretch of road and only sitting on 100kph, but we average around 13l/100 in most normal driving and never average 11 to 12 and i run 31s and standard gearing with a chip.

I also usually fill when the light comes on, and normally put around 80 to 90ltrs in depending on when the light come and how far from a servo i am.

Also to get 850ks from a tank and 11ltrs/100k, you would need to use 95ltrs of diesel, which is 11.18l/100ks to be excact or 8.95ks per litre or 25.29 MPG.

730ks from 87ltrs is the best since the chip, thats 11.92ltrs/100ks and the needle was on the E line, it drops to 580k to 620ks when towing.

Baz.

Originally Posted by tombraider

Mick

With 32s and 4.11s the vehicle is overgeared too much...

For those disco owners wanting to run a 32 I suggest a 3.9 gearset...

It pairs beautifully with the 32s on a Disco.

PM if you want more info

3.9 gearset? I was pretty sure the next one up from 3.54 was 4.11? What do these come out of? What is the teeth count to get it to 3.9?

Have a poke around the Kamm diffs site, a couple of different options in there.

By my maths 32/29 * 3.54/4.11 = 95%, so its not a lot out.

Mines over geared to @#$#% on the 35s. the 1.4s have been replaced with 1.2Q disco gears. Say 15% up. Much better on the open road on 32s. But add the Simexes, & add another 15%. Its a 3 sped around town, & a 4 speed on the highway... Not really a problem, just have to be careful with the clutch on a hill start.

Add 49% maxidrive rockcrawlers, and most of the overlap between hi & lo is eliminated.

Regards
Max P

Originally Posted by Redback

How do you guys get this economy my best was 11.3/100, that was on a flat stretch of road and only sitting on 100kph, but we average around 13l/100 in most normal driving and never average 11 to 12 and i run 31s and standard gearing with a chip.

I also usually fill when the light comes on, and normally put around 80 to 90ltrs in depending on when the light come and how far from a servo i am.

Also to get 850ks from a tank and 11ltrs/100k, you would need to use 95ltrs of diesel, which is 11.18l/100ks to be excact or 8.95ks per litre or 25.29 MPG.

730ks from 87ltrs is the best since the chip, thats 11.92ltrs/100ks and the needle was on the E line, it drops to 580k to 620ks when towing.

Baz.

Hi Baz, my figures are there or there abouts and were calculated a while back. I normally try and let the fuel filter deal with some of the crap in the tank and run for about another 75-100 after the fuel light has come on.....yes I know, bad to run out of fuel in a deisel but I live in town and don't drive far during the week and know there is still tons left in the tank When filling up I normally end up fitting about 91 lts back into the tank......actually manged to fit 101 lts in the talk once, so either I am being ripped off or my tank has swollen

11.18 sounds about right to me though. I have started to drive it a bit harder or higher up the rev range which actually returns better fuel economy in my car......I hear that is how turbo deisels like to be run and it seems to ring true for me - plus mine is a manual which is more economical tha an auto am I right?

Hope this helps, Mick