truck talk

[crazzywolfie]

depends on the tire. usually you have to get a wider tire to get a taller tire. the wider the tire the more rolling resistance there is. now usually in order to get larger tires with the same width you usually have to get larger rim.

 

[Bluethunder3320]

the tires on his truck are tall and skinny. next time i see it i will take pics...

so far so good with the ford! no more tire rubbing unless i turn full lock

 

[devino246]

depends on the tire. usually you have to get a wider tire to get a taller tire. the wider the tire the more rolling resistance there is. now usually in order to get larger tires with the same width you usually have to get larger rim.

The main reason is reduced torque output. With taller tires, your engine has to work harder to get the truck up to speed. In order to make your engine work harder, you have to depress the pedal further, using up more fuel.

 

[Kaptain Krunch]

20% is a bit of a leap for cars. Trucks, maybe.

EGR without EGR valve? That would lead to horrible drivability and performance issues.

was thinking the same, never heard of this myself? The EGR valve in your typical older vehicle runs off vacuum and is only open at low rpm, and during deceleration, at high rpm it generally is closed, so having a un-valved egr would seem like a very bad idea.

Also, as a side note removing the EGR is bad. Absolutely no point, a common misconception is that removing the egr will gain power, however that is 100% wrong in most cases. If you remove an egr setup, you will get spark knock due to increased combustion temps, and therefore you will have to retard the timing, losing any power you gained. Only reason to remove an egr would be for race purposes where high octane fuel is used, and fuel economy/emissions are unimportant.

 

[fowler]

The main reason is reduced torque output. With taller tires, your engine has to work harder to get the truck up to speed. In order to make your engine work harder, you have to depress the pedal further, using up more fuel.

Hence the reason 4x4 people either lower the ratio in the diff or transfer case

U get less torque but a higher top speed

If the vehical has serious over size tyres then the speedo may be inaccurate
if it reads off the gear box u will find it to be pesermistic and may get u in trouble with the cops

 

[Doc Sprocket]

Hence the reason 4x4 people either lower the ratio in the diff or transfer case

U get less torque but a higher top speed

Having a bit of trouble with this statement. Offroad enthusiast regear lower to get MORE starting torque, Top speed is often lost, but unimportant. Big, heavy tires throw the factory ratios right out the window. for the most part, the accepted rule of thumb is if you are increasing tire size by 10% or more over stock, you need to regear.

If the vehical has serious over size tyres then the speedo may be inaccurate
if it reads off the gear box u will find it to be pesermistic and may get u in trouble with the cops

The very moment you change tire diameter away from factory spec, the speedo's accuracy goes. What people often do not understand is that it's a percentile, not a fixed number. Example- "I put on bigger tires, now my speedo is out by 10 MPH". No- it isn't. It's out by a percentage. While it may be out 10 MPH when you are travelling 50 MPH, it would only be out 5 MPH when travelling at 25. Similarly, it would then therefore be out by a factor of 20 MPH if you were driving at 100 MPH.

Larger tires will cause your speedo to show SLOWER than your actual road speed, because you are physically travelling further per tire revolution.

 

[fowler]

Having a bit of trouble with this statement. Offroad enthusiast regear lower to get MORE starting torque,

The very moment you change tire diameter away from factory spec, the speedo's accuracy goes..
.

thats where i was going
they fit bigger tyres and they loose torque
so they regear to regain torque

the manufacturer usually gives u a spec of the trye size u can work between
bigger and smaller
but its only a few inchs either way

EDIT
oh i see where this went
my bad grammer
in the current state with no regearing he has lost torque but gained high speed

 

[crazzywolfie]

The main reason is reduced torque output. With taller tires, your engine has to work harder to get the truck up to speed. In order to make your engine work harder, you have to depress the pedal further, using up more fuel.

are you sure you understands tires? if you were to run taller tires that were narrower then your engine would require about the same amount of torque to turn as stock up to a certain size. its like a mountain bike tires vs road bike tires. they could both be the same size but the narrower road bike tire would take less torque to get moving and keep going at that speed apposed to mountain bike tires which are wide and slow to get going and take more power to keep at that speed.

 

[Bluethunder3320]

my speedo reads zero all the time, lol

but i hear having a tranny without overdrive is less fuel efficient because the engine has to turn faster. this can be similar to having really small tires. so both turning faster and slower hurt fuel economy?

 

[crazzywolfie]

you should really fix that speedo one day. rockauto has a speedo cable for $11 plus shipping. might also be able to get one at a local parts store for about the same price.

but i hear having a tranny without overdrive is less fuel efficient because the engine has to turn faster. this can be similar to having really small tires. so both turning faster and slower hurt fuel economy?

you got it. depends on what you mean by smaller but usually anything smaller than stock size is bad for gas mileage but sometime running larger tires can also hurt.

 

[Bluethunder3320]

my speedo cable is good, the outside gear is good, but it doesnt work... the gear inside the tail housing must be bad

 

[crazzywolfie]

i don't know fords well enough but i would guess you have to figure out what gears you already have. i think most of the parts are made of plastic so it would make sense how it could strip.

 

[devino246]

are you sure you understands tires? if you were to run taller tires that were narrower then your engine would require about the same amount of torque to turn as stock up to a certain size. its like a mountain bike tires vs road bike tires. they could both be the same size but the narrower road bike tire would take less torque to get moving and keep going at that speed apposed to mountain bike tires which are wide and slow to get going and take more power to keep at that speed.

Yup, and the physics associated with 90% of the parts of the modern (and classic) automobile. Torque wasn't the proper word to use. The proper term would be force. Changing tire size will affect the amount of force applied by the wheels to the ground to move the vehicle.


Torque measured in ft.lbs. is a measurement of force applied at one foot from the center of rotation. So an axle outputting 100 ft.lbs. of torque, with a 1 foot radius wheel, will output 100 lbs of force.


Given two axles, both outputting 100ft.lbs. of torque, one axle with a 30" diameter tire, the other with a 26" diameter tire.


Axle one (30" tire) has a radius of 15". 100 ft.lbs. converts to 1200 in.lbs. 1200/15=80. So a 30" tire outputs 80ft.lbs. of force.

Axle two (26" tire) has a radius of 13". 100 ft.lbs. converts to 1200 in.lbs. 1200/13= 92.31. So a 26" tire outputs 92.31lbs. of force.

So the engine is exerting the same amount of force in both cases, yet axle 1 has less force being applied to the ground. So what happens if the guy driving the truck with axle 1 wants to accelerate faster? He gives the truck more gas, and down goes his fuel mileage.

you got it. depends on what you mean by smaller but usually anything smaller than stock size is bad for gas mileage but sometime running larger tires can also hurt.

You're making ridiculous generalizations. There are dozens of tranny gear-rear end-tire size combinations. Someone who intended to drive mostly on the highway may have ordered a truck with a rear end somewhere in the 2.8-3.5 range. Putting smaller tires on that would most certainly net better mileage around town.

 

[devino246]

my speedo cable is good, the outside gear is good, but it doesnt work... the gear inside the tail housing must be bad

Have you tried pulling the cable off the back of the gauge cluster and attempted to turn the inner cable? Have you also checked to see if the cable turns when you drive the truck?

 

[Bluethunder3320]

i have 3.55 gears. which i hear is optimal for all around driving.

i turned the cable with my fingers and the speedo moves, and the odometer moved a tiny bit too

cable does not turn when i drive


i do have a rough idea of my speed, though. i had a GPS. in 4th gear (im mainly in 4th) at 1,000 RPM im going 25, at 2,000 RPM im going just over 50

 

[crazzywolfie]

Yup, and the physics associated with 90% of the parts of the modern (and classic) automobile. Torque wasn't the proper word to use. The proper term would be force. Changing tire size will affect the amount of force applied by the wheels to the ground to move the vehicle.


Torque measured in ft.lbs. is a measurement of force applied at one foot from the center of rotation. So an axle outputting 100 ft.lbs. of torque, with a 1 foot radius wheel, will output 100 lbs of force.


Given two axles, both outputting 100ft.lbs. of torque, one axle with a 30" diameter tire, the other with a 26" diameter tire.


Axle one (30" tire) has a radius of 15". 100 ft.lbs. converts to 1200 in.lbs. 1200/15=80. So a 30" tire outputs 80ft.lbs. of force.

Axle two (26" tire) has a radius of 13". 100 ft.lbs. converts to 1200 in.lbs. 1200/13= 92.31. So a 26" tire outputs 92.31lbs. of force.

So the engine is exerting the same amount of force in both cases, yet axle 1 has less force being applied to the ground. So what happens if the guy driving the truck with axle 1 wants to accelerate faster? He gives the truck more gas, and down goes his fuel mileage.




You're making ridiculous generalizations. There are dozens of tranny gear-rear end-tire size combinations. Someone who intended to drive mostly on the highway may have ordered a truck with a rear end somewhere in the 2.8-3.5 range. Putting smaller tires on that would most certainly net better mileage around town.

you seem to miss everything. what does any of what you say have anything to to do with the width of the tire. are you telling me the widest 30" tire would require the exact same amount of force to turn as the narrowest 30" tire that you can get?

 

[devino246]

you seem to miss everything. what does any of what you say have anything to to do with the width of the tire. are you telling me the widest 30" tire would require the exact same amount of force to turn as the narrowest 30" tire that you can get?

My point is that tire diameter has more to do with gas mileage than tire width.

 

[Doc Sprocket]

Yes it does! In addition to the torque calculations, the related problem is rotating mass. More weight=harder to turn- that simple. Also harder to KEEP turning, and also harder to stop. Big honking 4x4's often need brake upgrades to go with it all.

One other point- wider tires DO rob a bit of power... Larger contact patch equated to additional friction.

 

[Bluethunder3320]

yeah the wider tires grab a lot more than the 31's i had on. with those i could burn out so easily. and even in the rain it was hard to keep them from spinning.

i dont think my trucks a 4x4 anymore, well i havent fixed the clanky driveshaft yet and just found out that my u joints in the front axle flop around too. i guess i could use them till they break.

just found the universal joints for my driveshaft for 10 bucks... woah i thought it was more like 150$

 

[cumminsbayou4x4]

we had to replace my dads universal joint in his 08 cummins it was a job betting it out and stuff