[sierra-morgs]

im sure this has been answered many times but im too lazy to search for the thread sooooo whats the largest tire size i can put on my 97 sierra without changing gear ratio for the stock engine,i have heard 31s wont matter but any bigger is a problem yes/no?

[ando_zook94]

i run 30's and its alright until u hit highway.. 31's would be abit worse..

[zooky08]

215's

[atari4x4]

i did a search & it said 37's are fine with stock gearing.

[86slowsierra]

215/75/r15 would be about the biggest.

do not run 31's with out fixing the gearing

[zukmeista]

86slowsierra wrote:

215/75/r15 would be about the biggest.

do not run 31's with out fixing the gearing

I don't understand what all the fuss is about. I just put 31's on my stocker and it drives fine on the road. Offroad, it's still fine for mud and slippery stuff, but doesn't crawl as well as it used to. Overall, it is just fine without any gearing alterations. Will be getting gears when I can afford it though, probably in another 10 years at this rate

[93zook]

i had 235/75's on mine, was great but didn't use 5th and low range suffered a bit.

[31zook]

@atari, yes stock H1 gearing will work. I have put magnets on my fuel line and a hyclone, it puts out about 35% more power.

[Scrawny]

sierra-morgs wrote:

im sure this has been answered many times but im too lazy to search for the thread sooooo whats the largest tire size i can put on my 97 sierra without changing gear ratio for the stock engine,i have heard 31s wont matter but any bigger is a problem yes/no?

So you expect everyone to repeat the same info that's already been discussed a billion times over just cos you're too lazy to search??

Stick 35's on with ya stock suspension and gearing!! That'll help me cos I've got shares in all the major clutch suppliers

[Chris88]

I have 31s on stock gears, works fine, 100kph in 4th if your on flat road, otherwise it's 80/90, hills kill it really have to get a run up and work the car hard to keep anywhere near traffic speed but not undrivable, I never had a problem off road, couple of steep hills had it strugleing but got up, I don't do alot of slow steep rock ledges that would be difficult. All in all you'll be just fine previding you have correct lift, don't mind a top speed of 90kph and can use a little common sence offroad, maybe use the search function next time this is something covered a million and one times haha

Hope this helps

[SierraDan]

31's with stock gearing is not fine. Don't lie to him.

31's with a 1ltr transfer is bearable to drive around town, but in the bush it's not awesome.

225's are the biggest I would go with stock gearing.

235's and up I'd be looking at a gearing fix.

[Chris88]

I am not lieing, I have 31s and stock gearing and my car goes just fine, I have never had a problem on or off road, as explained it's not ideal but perfectly drivable there are so many fear mongering on this forum sometimes. But saying I'm lieing, and any SA auszookers can back up my statement that it goes just fine. Not ideal ( as I thaught I maid clear) but wold just fine

[TZAR]

sierra-morgs wrote:

im sure this has been answered many times but im too lazy to search

I sure I have answered many times and am too lazy to do it again.......

[SierraDan]

Chris88 wrote:

I am not lieing, I have 31s and stock gearing and my car goes just fine, I have never had a problem on or off road, as explained it's not ideal but perfectly drivable there are so many fear mongering on this forum sometimes. But saying I'm lieing, and any SA auszookers can back up my statement that it goes just fine. Not ideal ( as I thaught I maid clear) but wold just fine

It does GO yes. You can DRIVE it yes. But its fucked.
The clutch slips when trying to drive up decent sized things.
The fuel economy is crap.
It has a very slow pick up trying to drive around town and you end up in second trying to get up a hill.
5th is not useable unless you have a decent downhill stretch.

It's shit. 1ltr transfer at the LEAST, even then its shit.

[ZookFan]

SierraDan wrote:

31's with stock gearing is not fine. Don't lie to him.

31's with a 1ltr transfer is bearable to drive around town, but in the bush it's not awesome.

225's are the biggest I would go with stock gearing.

235's and up I'd be looking at a gearing fix.

You got that right mate, so true!

[SuziBlu]

SierraDan wrote:

Chris88 wrote:

I am not lieing, I have 31s and stock gearing and my car goes just fine, I have never had a problem on or off road, as explained it's not ideal but perfectly drivable there are so many fear mongering on this forum sometimes. But saying I'm lieing, and any SA auszookers can back up my statement that it goes just fine. Not ideal ( as I thaught I maid clear) but wold just fine

It does GO yes. You can DRIVE it yes. But its fucked.
The clutch slips when trying to drive up decent sized things.
The fuel economy is crap.
It has a very slow pick up trying to drive around town and you end up in second trying to get up a hill.
5th is not useable unless you have a decent downhill stretch.

It's shit. 1ltr transfer at the LEAST, even then its shit.

My 1.3 with stock gears and 31" claws went fine on 31s, not much could touch me off road, on road, 90k by the speedo was it, maybe 95k, but tht is 13% overdriven, so in theory I was doing around 110k, i could even tow a trailer full of wood in top gear.

I swapped over to 4.11 diff instead of 3.9s and a 1l Tcase, tis better, but stock an 31s is very do-able.

[atari4x4]

doing anything remotely technical with larger tyres & no gearing will leave you skull fucking your clutch to go anywhere without stalling.

[SierraDan]

atari4x4 wrote:

doing anything remotely technical with larger tyres & no gearing will leave you skull fucking your clutch to go anywhere without stalling.

Thats the nicer way of putting it

[Chris88]

i like skull fucking my clutch......shows it whos boss lol

[SuziBlu]

Technology and me live on different planets.

[JrZook]

SuziBlu wrote:

Technology and me live on different planets.

We already know that one

[sierra-morgs]

sounds like a fair bit of trouble for 31s, maybe 30 inch would be a better compromise i just need more clearance, my diff has copped a beating recently.
cheers for the replies

[JrZook]

zukmeista wrote:

86slowsierra wrote:

215/75/r15 would be about the biggest.

do not run 31's with out fixing the gearing

I don't understand what all the fuss is about. I just put 31's on my stocker and it drives fine on the road. Offroad, it's still fine for mud and slippery stuff, but doesn't crawl as well as it used to. Overall, it is just fine without any gearing alterations. Will be getting gears when I can afford it though, probably in another 10 years at this rate

Your definition of 'fine' must be different over there. Stock WT 1.3's with 31's are puss. Forget using 5th gear and cruising at 100 comfortably with some sort of fuel economy or doing any sort of controlled hill starts.

[Red89]

JrZook wrote:

Your definition of 'fine' must be different over there. Stock WT 1.3's with 31's are puss. Forget using 5th gear and cruising at 100 comfortably with some sort of fuel economy or doing any sort of controlled hill starts.

I think that is the point everyone is making 'fine' is a relative term

sierra-morgs wrote:

sounds like a fair bit of trouble for 31s, maybe 30 inch would be a better compromise i just need more clearance, my diff has copped a beating recently.
cheers for the replies

Not much point going to 30's instead of 31's you will still need to address gearing eventually. Personally I would go 31's, learn to live with it and aim for gears in under 12 months. I had 215r15's which are the same size as 235's and I felt it was fine, 31's were liveable, but I did get gearing with in 6 months to make life alot easier both on and off road.

[zukenutter]

Red89 wrote:

I had 215r15's which are the same size as 235's.

??

[SierraDan]

zukenutter wrote:

Red89 wrote:

I had 215r15's which are the same size as 235's.

??

[Red89]

zukenutter wrote:

Red89 wrote:

I had 215r15's which are the same size as 235's.

??

I lied they are 28, 235's are 29 my mistake.

[Myles]

I run 235/75/15's on my coily with stock gearing and it goes great.. Easily sits on 120kph in 5th gear.. Doesn't speed up quite as quick as it did when i ran 215's but it still goes fine (if your not drag racing every random P plater off at the lights you won't notice it Even with 4 people and lugguage for 2 nights it still goes fine on the highway up the sunshine coast etc..

[sierra-morgs]

120 easily!!! i dont think i have taken mine over 100 , it has got BFG muddies not sure on the exact size il have to check that out but i definitely need more ground clearance

[mnemonix]

I'm yet to see a sierra that will do 120 easily on larger tyres with a stock engine. And I've driven more than my fair share.

My swb would do 100kms comfortably in 5th gear even around hills.
When I went to 235/75 15's I gave up on using 5th, even on flat ground.
Hills I used to climb in 5th I now needed to go to 3rd, and would normally be forced to slow to around 70km/hour.

Gearing IS required onroad for this size or larger.
Offroad, lowrange is crippled. Your clutch will cop a hiding on anything other than a basic forest trail.