Dave and i have been talking, and neither of us are sure how to work it out, or if it can be.
If you have.......
gearbox with a first of 3.5
low range of 4.7
diff ratio of 4.8
then you have a low range of about 78:1
now if you are running a 28 inch tyre the truck is going to crawl slower than if the same truck was running a 44. Is there away to workout the crawl ratio inrelation to the distance traveled? the over all crawl ratio of the truck and the different charteristics of the truck in a percentage of distance lost verse over all crawl ratio change?
question 2.
a hilux with 4.88 and 33's is said to be of factory ratio, if a hilux is fitted with 35's and 5.29's it is also said to be close to factory ratio. On paper the final drive works out to be different but add into the equation the fact that in theroy both ratios are factory, how do you work out the total distance of the rolling radius of the tyre in relation to the crawl ratio and why do two trucks, in theory with stock ratios, crawl and preform differently. Although the crawl ratio and tyre size are different the "over all" ratio would in theory be the same.
NICK AND DAVE
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crawl ratio/distance traveled question
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crawl ratio/distance traveled question
TECH SCREW GURU
NICK wrote:POS wrote::shock:
thats what we thought.
NICK
Yeah its a good one!
Have you asked SAM???
I do remember reading about the same thing in a yankie mag but i can't find it and i can't remember the ratio as i didn't really care at that point of time!
It shouldn't be too hard to work out!
All the Mechanical engineers out there should be able to do this with their eyes closed!
Factoring the gearing effect of different tyre sizes is simple cause the circumference of the tyre is proportinal to the diameter so if you want to compare different gearing with different tyre sizes just divide the overall gearing by the tyre size that that gearing is running to get an overall number that can be compared.
BUT for the life of me I carnt work out what you are actualling asking so I dont know if I have answered anything??
Sam
BUT for the life of me I carnt work out what you are actualling asking so I dont know if I have answered anything??
Sam
POS wrote:NICK wrote:POS wrote::shock:
thats what we thought.
NICK
Yeah its a good one!
Have you asked SAM???
I do remember reading about the same thing in a yankie mag but i can't find it and i can't remember the ratio as i didn't really care at that point of time!
It shouldn't be too hard to work out!
All the Mechanical engineers out there should be able to do this with their eyes closed!
it is one of those things that makes you go mmmmmmmmmmmm. there has to be an equation that will work it out.
eg, what diff gears do you need?
well it is the old ratio div. tyre size x new tyre size= new ratio
4.56/31x33=4.85
the above equation shows changing a 31 up to a 33, requires a 4.88 ratio to allow for the extra rolling dia.
NICK
TECH SCREW GURU
Strange Rover wrote:Factoring the gearing effect of different tyre sizes is simple cause the circumference of the tyre is proportinal to the diameter so if you want to compare different gearing with different tyre sizes just divide the overall gearing by the tyre size that that gearing is running to get an overall number that can be compared.
BUT for the life of me I carnt work out what you are actualling asking so I dont know if I have answered anything??
Sam
yeah we know that, but thats not what we asked.
mmmmmmm maybe try this,
if you have a 35 tyre and then fit a 39, what effect does this have on the crawl ratio of 80.1 at the ground. We realise the crawl ratio the axle remains the same, but effect on driven speed and distance changes in relation to tyre size.
NICK
TECH SCREW GURU
Strange Rover wrote:OK so instead of talking about overall gear ratio talk about distance travelled per 1000 revolutions of engine (use a thousand to make the numbers big enough)
so with 75:1 and 35in tyres you get
1000 x 3.14 x 35 / 75 = 1465 inches per 1000 revolutions of motor
Hows that??
Sam
so for example
1000x 3.14 x 44/ 75 = 1842 inches per 1000 revolutions of the axle, so the ratio of distance traveled has now changed and is 500 inch more, in reality altering the "overall" ratio.
NICK
TECH SCREW GURU
the 1000 is for the 1000 revolutions of the motor.
Once you take the tyre size into account you can no longer talk about overall ratio cause now its a distance and the overall ratio doesent make any sence.
What you could do is say the the tyre size changes the gear ratio relative to a basic tyre size (say a 35in tyre)
So if you have 75:1 and 35s then the overall ratio is
75 x 35 / 35 = 75:1
Now if you had 44s then
75 x 35 / 44 = 60:1
Which means your overall comes back to 60:1 compared to a guy that had the same ratio and was running 35s.
Sam
Once you take the tyre size into account you can no longer talk about overall ratio cause now its a distance and the overall ratio doesent make any sence.
What you could do is say the the tyre size changes the gear ratio relative to a basic tyre size (say a 35in tyre)
So if you have 75:1 and 35s then the overall ratio is
75 x 35 / 35 = 75:1
Now if you had 44s then
75 x 35 / 44 = 60:1
Which means your overall comes back to 60:1 compared to a guy that had the same ratio and was running 35s.
Sam
Strange Rover wrote:the 1000 is for the 1000 revolutions of the motor.
Once you take the tyre size into account you can no longer talk about overall ratio cause now its a distance and the overall ratio doesent make any sence.
What you could do is say the the tyre size changes the gear ratio relative to a basic tyre size (say a 35in tyre)
So if you have 75:1 and 35s then the overall ratio is
75 x 35 / 35 = 75:1
Now if you had 44s then
75 x 35 / 44 = 60:1
Which means your overall comes back to 60:1 compared to a guy that had the same ratio and was running 35s.
Sam
After all that it seems so simple, we new you would know and that was exactly what we wanted to know.
Now what do you think the ideal crawl ratio and tyre size combo is in relation to the above statement?
TECH SCREW GURU
dont forget that torque at the wheel doesnt reduce by the same amount compared to circumference, becasue the radius is the leverage that the gearing is working against
35", loaded radius = 17", circumference = 107"
44", loaded radius = 20", circumference = 126"
so even though the distance travelled is different by 15% the reduction is torque at the wheel is only 15%
aw shnitz, forget i said anything
my brain hurts
35", loaded radius = 17", circumference = 107"
44", loaded radius = 20", circumference = 126"
so even though the distance travelled is different by 15% the reduction is torque at the wheel is only 15%
aw shnitz, forget i said anything
my brain hurts
if you could work out what you are actually asking, maybe people could help you!
the ratio will be he same no matter what size tyre u have, and is therefore pointless in this respect.
but the ratio of the distance travelled to rpm of the motor would be what you are looking at right?
but what are you actually asking?
the ratio will be he same no matter what size tyre u have, and is therefore pointless in this respect.
but the ratio of the distance travelled to rpm of the motor would be what you are looking at right?
but what are you actually asking?
you do not specifiy the rpm or time for the 35's to compare to?
ok, on 35's the rear axel would have to rotate 79.7 times,
on 44's the axel only needs to rotate 63.4 times
so with 75:1,
the engine need to rotate 5977.5 times on 35's
and 4755 on 44's.
so lets say u do the distance at 1500 rpm on the 35s, which would take 3.98 minutes on 35's.
to do it in the same time on 44's it would be doing 1194 RPM
ok, on 35's the rear axel would have to rotate 79.7 times,
on 44's the axel only needs to rotate 63.4 times
so with 75:1,
the engine need to rotate 5977.5 times on 35's
and 4755 on 44's.
so lets say u do the distance at 1500 rpm on the 35s, which would take 3.98 minutes on 35's.
to do it in the same time on 44's it would be doing 1194 RPM
napsta wrote:you do not specifiy the rpm or time for the 35's to compare to?
ok, on 35's the rear axel would have to rotate 79.7 times,
on 44's the axel only needs to rotate 63.4 times
so with 75:1,
the engine need to rotate 5977.5 times on 35's
and 4755 on 44's.
so lets say u do the distance at 1500 rpm on the 35s, which would take 3.98 minutes on 35's.
to do it in the same time on 44's it would be doing 1194 RPM
and both would take the same amount of time? take into account the fact that they were racing, they would be dead even side by side giving the fact that they would be doing the same distance and speed on a different tyre ratio distance.
nick
TECH SCREW GURU
83 lux wrote:HA HA NICK
from all that do you how no what you were asking about.
and do you no the answer to that question.
well now that i have got the answer to my first few questions, i will ask another, why is it you always get words back to front and leave afew out off every sentence?
NICK
TECH SCREW GURU
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