[bede]

hi all have a gearing question i have 4.16.1 transfer gears and 4.8 diffs 4 speed gbox what size tyres can i run for good crawl speed, it also a 1lt

[royce]

probably dont wanna run any bigger than 31's or youll start to have a lot of trouble in rocks and stuff

[Gwagensteve]

I get 60:1 crawl based on your data.

What's a good crawl speed? What's a good tyre size for 60:1? It all depends on what you want to drive.

For us, 60:1 is pretty sweet with maybe a 31-33" tyre.

For the record, I like to compare crawl speed at peak torque.

A stock 1.3 sierra runs 14.6km/h @ peak torque in 1st low.
A stock 1.0 sierra runs 14km/h @ peak torque in 1st low
Your car on 31's will run 8.66km/h
on 33's 9.21km/h
on 34's 9.49

It should feel pretty good with any of those tyres, but it's very dependent on the driving you do. If you run very steep terrain, 60:1, 33's (for instance) and the tall 1st gear and tiny 1.0litre clutch might be hurting a bit, and you might prefer the 95:1 crawl ratio that 6.5 gears offer.

PS you are aware that even with 33" tyres you will be spinning at 4800rpm @ 100km/h?

Just some thoughts.
Steve.

[bede]

ok thanks might need 6.5 reduction gears than

[SuziBlu]

Gwagensteve wrote:

I get 60:1 crawl based on your data.

What's a good crawl speed? What's a good tyre size for 60:1? It all depends on what you want to drive.

For us, 60:1 is pretty sweet with maybe a 31-33" tyre.

For the record, I like to compare crawl speed at peak torque.

A stock 1.3 sierra runs 14.6km/h @ peak torque in 1st low.
A stock 1.0 sierra runs 14km/h @ peak torque in 1st low
Your car on 31's will run 8.66km/h
on 33's 9.21km/h
on 34's 9.49

It should feel pretty good with any of those tyres, but it's very dependent on the driving you do. If you run very steep terrain, 60:1, 33's (for instance) and the tall 1st gear and tiny 1.0litre clutch might be hurting a bit, and you might prefer the 95:1 crawl ratio that 6.5 gears offer.

PS you are aware that even with 33" tyres you will be spinning at 4800rpm @ 100km/h?

Just some thoughts.
Steve.

Steve, you talk of "peak torque", what is this in revs.

My 1.3s seem to love around the 4k mark, my 1.6 comes in a little lower.

[bede]

my zuk does not see the black top trailer queen mainly want to drive creeks rocks

[Gwagensteve]

Peak torque in a 1.3 is listed as at 3475 rpm. It's a little lower for the 1.6 at 3200 rpm (I think), but as you've noticed, the "sweet spot" - where the power and torque curves intersect, is about 4000rpm for the 1.3 and a touch lower for the 1.6 because of the longer stroke limiting revs a lowering and flattening the torque curve a bit.

The flatter the torque curve, the flatter the horsepower curve and the longer the sweet spot lasts (as in over a wider range of revs) which is why a 1.6 is more forgiving about what gear its in.

I can work out speeds at any revs but peak torque is a simple comparator, and useful for comparing different engine characteristics and their effect on gearing.

Steve.

[SuziBlu]

Cool, thanks

[whincup]

wow, thats actually a really good way work it out... would be really good to see dyno runs of the same car on different tyres, or the same car with different transfer gears...