Tyre Size Recommendation Help.

[Jaffa]

I am tring to work out what tyre size I should be looking at.

Car is a 1L Sierra, until recently had standard gearing and 30" muddies.

Just got widetrack diffs complete with 5.11 gears, diffs were also setup for spring over, so I have converted to spring over now.

Ive done some calulations on a gear ratio calculator, but just wanted to double check my results,

Original
1st gear X Low Range X 4.11 diff
3.14 X 2.511 x 4.11 = 32.4 Final Ratio?

Now
1st Gear X Low Range X 5.11 Diff
3.14 X 2.511 x 5.11 = 40.2 Final Ratio

Call it 25% Difference, so if I go to 35" from my 30" that a 16% difference.

Sooooooooo.... my crawl ratio with 35 and new gears will be better than my 30's with 4.11's?

I just have a really bad feeling that Ive cocked up one of my calculations, and the cars not gonna move



Also, Im gonna get offset rims (probly about 30-40mm offset) Im after recommendations on what width tyres to get. Im thinking of getting Simex Etreme Trekker 2's in 35x11.5x15's.

On 35's do u think I'll have to do much guard chopping to help prevent rubbing. Suspension is Spring over, standard Shackels, no body lift.

Thanks for your help and sorry bout the long post

Brendan

[alien]

WT diffs SPOA and 35's sounds scary... thats a VERY tall zuk! =)

i'd be worried about breaking CV's and Axles - although it depends on driving style.

you've lowered the diff ration by 38% (WT is 3.7) - so a tyre 38% larger than stock 26" will bring u back to stock gearing. Hence a 35" tyre would be pretty much spot on.

Might be time to consider power steering too =P imagine 35's in a carpark! you'd have arnie arms in a week!

[Jaffa]

5.11 is 25% better than narrow tracks (that used to bu under it) at 4.11

The car isn't a daily driver, is just used for fun but will be driven on road for maximum 30-40km's to get to tracks.

If anyone else think 35's will be to big please tell me.

Brendan

[Jaffa]

<------------------ The pic in my avatar is it sitting on 32" mogrels on a stupidly offset rims, with spring over, just to give you an idea of the clearance in guards.

Brendan

[sierrajim]

don't forget that a standard whelbase zook on 35's can end up on its end. Just ask Dewse what his did on 33's.

WT diffs and 35's might be a little too big for your CV's. You may be better off looking at 33-small 34" tyres.

[grimbo]

Have you driven it on the 32's? Why not try thhem out see how you go and see if you need 35s compared to wanting 35s. Strength wise you might be able to get away with a 35 in Vic conditions as the majority of it is low traction stuff.

A 35" Simex will be a very stiff tyre on a Zuk and you'll find the ride will be terrible. With a sprung over swb Zuk on 35s you are definetly going to be finding out that your wheelbase might be a little short and on steep climbs/decents you may find it very tippy.

As I said try it out on the 32s for awhile get used to driving it SPOA and see if you actually need the bigger tyre

[DeWsE]

don't forget that a standard whelbase zook on 35's can end up on its end. Just ask Dewse what his did on 33's.

Yeah just ask.

You will find that the tires lift really bad. You will have really bad stability climbing and going down.

[redzook]

too big

[Jaffa]

Cool thanks for the suggestions guys.

The 32"'s arn't mine (1 rim is really bent so I cant drive on it properly) they are only on there so I could see what the offset was like.

The thing im woried about is gearing, Im not into rock hopping, mainly mud, so I dont want really low gearing, I still waqnt to be able to get a bit of wheel speed up. This is my first 4WD that I changed gears/diffs and tryed to pick tyre sizes to suit.

Brendan

[redzook]

the 35's with be right for the gear ratio

but u wont push the 35's easy they are alot heavier and give alot more traction requiring a lot more forse to push compared to the stock 26"

32 will aloww u to still get heeps of wheel speed wll las much as a zuk motor will allow

[alien]

yeh if its speed you want in the mud just use 3rd where you'd normally use 2nd etc... all the low range stuff i drive, even when doin 60-70km/hr on gravel in 4-low, i never go to 5th gear... so with those gear numbers, you'd likely find in low range 5th gear will be perfect for 70km/hr... and youll still have ultra low 1st gear should some rocks come along (not that youll stand much of a chance going 5th to 1st at 70km/hr but anyway...)

[Jaffa]

you'd likely find in low range 5th gear will be perfect for 70km/hr...

But I dont have 5th gear Its only a 4spd, I see your point though.

Thanks for your help peoples.

[grimbo]

yeh if its speed you want in the mud just use 3rd where you'd normally use 2nd etc... all the low range stuff i drive, even when doin 60-70km/hr on gravel in 4-low, i never go to 5th gear... so with those gear numbers, you'd likely find in low range 5th gear will be perfect for 70km/hr... and youll still have ultra low 1st gear should some rocks come along (not that youll stand much of a chance going 5th to 1st at 70km/hr but anyway...)

what are you doing 70km/h in low range for. If you are going that speed you should be in high range. You'll wreck your t/case going those speeds in low range. It must be revving its guts out at that speed

[alien]

haha well theres a few tracks i know pretty well, and in between rutted awesome areas theres some smoooooth access tracks... so most of us just give it a blat down the tracks and slow down before the next set of ruts. dont do it all the time - often its more fun in 2wd so i can go rally style and drift the corners.. lol

not revving its ass off in low though - doing about 3500-4000rpm in 4th from memory?

why would it do damage to use low range at high speeds? not like im redlining it, just cycling through the gears as i would in high range.

[Jaffa]

Just one last annoying question.

What width tyre would you guy recommend 10.5 or 12.5's, I have to get new wheels anyway so thats not a problem, I understand the advantages and disadvantages of each, and dont care about looks, just want better performance.

Thanks

Brendan

[grimbo]

In Victoria I'd always say go with a tall skinny tyre, especially on a Zuk. Easier to fit, less weight and strain on components, they perform better in mud as they cut down for grip rather than spinning on top

[Mudzuki]

34 10.5 LTB Swamper

on 15x7s

hold the bead well and i have had no problems with stability on a SPOA with 5.12 in WT housings with 2"BL

[derelict_frog]

U mightnt be able to spin bigger tyres properly they might just grip and stall your engine, small tyres going fast are good in mud.

Any one know whats the standard gearing in NT diffs if a WT is 5.11? Because i don't have any gearing changes from standard and in the small amount of rocky bits im going just a bit faster than i want in L4 1st... but its a good speed in mud though...

[nicbeer]

U mightnt be able to spin bigger tyres properly they might just grip and stall your engine, small tyres going fast are good in mud.

Any one know whats the standard gearing in NT diffs if a WT is 5.11? Because i don't have any gearing changes from standard and in the small amount of rocky bits im going just a bit faster than i want in L4 1st... but its a good speed in mud though...

Std NT is 3.9
WT is 3.7
Vitara is 5.12 - can fit into sierra housings
1L is ?

[Jaffa]

1L is 4.11

[84ZOOKSTA]

I have a 84 zook with a 3inch body lift and i run 31inch x 10.5 simex centepedes extreme teckers they are more like a 32.5inch tyre and have very little tyre rubbing in the guards. i have tried to put a simex 32inch in there but since they are more like a 33.5inch tyre it did rub alot more and we all know that the tyre locking in the guards will start breaking CV's


I use a 15x7inch rim with a negative 15mm offset and they seem to be purfect.

Simon..

[derelict_frog]

Where do u measure the offset from?

[84ZOOKSTA]

Offset. Zero offset is where the hub mounts to the rim right in the middle off the rim. Say you has a 150mm wide rim then the zero offset would be 75mm from front and 75mm from the back.
The rims i use are a 15mm negative offset which means where it mounts on to the hub is 15mm closer to the back of the rim which inturn brings the rim 15mm further out from the car. A positive offset is the opposite if i was to have a positive 15mm offset it would be 15mm closet to the car.

Hope this helps a bit.

Simon.

[Jaffa]

Thought I'd post a follow up on what happened with tyres,

I borrowed a set of 32 mongrels off a mate and headed off on a trip....................... only made it 20kms before the motor blew up (I havn't cracked it open yet so I dont know what let go but their was lots of smoke and horrible banging noises)

Was my own fault though, I should have relised that 7000+rpm and foot literally flat to the floor for 15-20 minutes wasn't the best thing for it.

Oh well time for an engine conversion.

[Red_Zook]

Thought I'd post a follow up on what happened with tyres,

I borrowed a set of 32 mongrels off a mate and headed off on a trip....................... only made it 20kms before the motor blew up (I havn't cracked it open yet so I dont know what let go but their was lots of smoke and horrible banging noises)

Was my own fault though, I should have relised that 7000+rpm and foot literally flat to the floor for 15-20 minutes wasn't the best thing for it.

Oh well time for an engine conversion.

I SMEL BULLSHIT
Zook motors standard bounce at about 74k...
but they dont have nough power over about 6500 to hold the revs...
unless u were driving in first gear?
what are u expecting a motor to do if u hold it at high revs?
i want pics for prof!!
Phil

[derelict_frog]

LOL wth, they are 4 speed arnt they?

Couldnt u ask them all to slow down a bit?


3-4K rpm is good for highway driving :/



How slow were u goign before with the even smaller tyres?

[Jaffa]

What do you want pics of red zook?

If you dont beleive me that I was sitting on 7000rpm, then I spose you wont beleive me when I tell you that on my 30" muddies is was doing 7500rpm at 100kmph?

It is/was a 1ltr that was rebuilt about 10,000kms ago, so it was in reasonable condition, just wouldn't do what it did to it

Yes it is a 4 speed


BTW Red Zook, you sound like a dickhead.

[zukirolly]

Hey Jaffa/Brendan, are you the dood from Just Comm's/Just 4X4?
Send me a pm if so, i have a 1.3L with 5spd - done around 150k that might be of interest?
Maybe we can work out a deal...?

[Red_Zook]

What do you want pics of red zook?

If you dont beleive me that I was sitting on 7000rpm, then I spose you wont beleive me when I tell you that on my 30" muddies is was doing 7500rpm at 100kmph?

It is/was a 1ltr that was rebuilt about 10,000kms ago, so it was in reasonable condition, just wouldn't do what it did to it

Yes it is a 4 speed


BTW Red Zook, you sound like a dickhead.

Ok mate.. what eva you think...
but i recon if u drive at 100kph at 7000revs for 20min's u have to have a look at ya self.
and as i stated before i would HIGHLY doubt it would have enough pull at 7.5k to do 100kph...
i still say you are full of it mate (i already got a warning about this post)
and BTW I AINT NO DICK HEAD MATE! and i dont like being called that.
Phil

[JrZook]

With 30icn tyres, and im guessing the high ratio of the tcase to be 1.5:1 and 4 gear to equal 1:1 and diffs of 5.11.
At 7500rpm you should be doing around 140k's an hour.
That is wif the assumptionns that:
30inch tyres
high of 1.5:1
4th gear (top) 1:1 (correct if wrong)
diffs 5.11:1

But besides ease up fellas, a blown engine wow! No need to get cut up bout it. Peace out dudes!!!!!!!!!!!!!!!!!

Uni time,
cya'll hope ya get ur truck going again.