Wierd, no speed limiter?
Guest
Posts: n/a
QUOTE
Decker:
135mph(speedo)+3.498%(205tires)=139.66MPH!
that would be MPH- % not + %. Also that number is for 60mph. The % will go up the higher your speed. Not exactly linear but should be somewhere near the 5-5.5% mark. So with that said 135mph speedo - 5% (205/40R17) = 128.25MPH.135mph(speedo)+3.498%(205tires)=139.66MPH!
The smaller the tire diameter the more the speedometer will put out a higher number than you are going. The Bigger the tire diameter the slower your speedo say. This is why the guys who lift their trucks need to get speedo recalibrated. Because they are going faster than the speedo says.
As a side note if you don't know a smaller diameter tire will allow you to get more HP at the wheels. smile.gif not much but its something.
Thread Starter
Senior Member
Joined: May 2001
Posts: 1,494
Likes: 0
scca, i don't know about that, i'm pretty sure its the other way around. going from smaller to larger, your car still reads the same amount of ratations per second but since you have a longer circumference then for every one revolution your off by 10mm. 205-195mm.
at 100revs/sec, your supposed to do 19,500mm instead of 20,500mm. stuff like that.
so if your saying that there's a 5% difference then it'd be 135*1.05=141mph. which
isn't a huge jump from 139.
at 100revs/sec, your supposed to do 19,500mm instead of 20,500mm. stuff like that.
so if your saying that there's a 5% difference then it'd be 135*1.05=141mph. which
isn't a huge jump from 139.
Senior Member
Joined: Feb 2002
Posts: 463
Likes: 0
I don't know whats all the big fuss about but i was told by random and from my own experience that Tibbies are speed gov. @ 125 mph.
Now about tire sizes...
*if your stock tire/rim combo is a P195/60R15 and you get 205/40R16, they should be the same dia. because eventhough the 2nd set has a larger rim, it has a shorter side wall.
*If you change the effective dia. of your tire/rim combo to a SMALLER size to that of your stock tire/rim combo, it will spin FASTER because the circumference AROUND the tire is SMALLER.
*If you change the effective dia. of your tire/rim combo to a LARGER size to that of your stock tire/rim combo, it will spin SLOWER because the circumference AROUND the tire is LARGER.
If you go SMALLER than stock, the speedo will read FASTER than normal.
If you go LARGER than stock, the speedo will read SLOWER than normal.
It's all about surface area.
Rich.
Now about tire sizes...
*if your stock tire/rim combo is a P195/60R15 and you get 205/40R16, they should be the same dia. because eventhough the 2nd set has a larger rim, it has a shorter side wall.
*If you change the effective dia. of your tire/rim combo to a SMALLER size to that of your stock tire/rim combo, it will spin FASTER because the circumference AROUND the tire is SMALLER.
*If you change the effective dia. of your tire/rim combo to a LARGER size to that of your stock tire/rim combo, it will spin SLOWER because the circumference AROUND the tire is LARGER.
If you go SMALLER than stock, the speedo will read FASTER than normal.
If you go LARGER than stock, the speedo will read SLOWER than normal.
It's all about surface area.
Rich.
Thread Starter
Senior Member
Joined: May 2001
Posts: 1,494
Likes: 0
yeah your right the 205 195 numbers are the width. Those would be pretty small tires!!!
i don't know what i was thinking, i checked back at the site. The stock circumpherence is 1870.81mm and the new one is 1936.16mm.
So assuming that there's a +5% change (above 100mph) and there's a 10% degree of error.
135*1.05=141.75mph max
so it would be anywhere from 127mph-141.75mph realistically. which makes it alot more realistic if it was 127mph smile.gif 141(is a pipe dream huh?)
anyway, stealing a formula from mario's 150mph post
using the formula
Power in kW p=(12.9x10**-6)*q*c*A*V*(V+WV)**2
if it was 127mph/204.40kph (minimum)
p=(12.9x10**-6)*1.202*0.33*2.5087*204.40*(204.40+0)**2
p=0.0000129*1.202*0.33*2.5087*204.40*((204.40)**2)
p=>109.62Kw 147wHP
if it was 141mph/226kph (maximum)
p=0.0000129*1.202*0.33*2.5087*226.93*((226.93)**2)
p=>150.01Kw 201wHP !! eek!
I beleive my hp to be around 160ish with my mods. Definetly being optimistic. So its more likely i was at the 130mph-ish mark then the 140mph-ish mark in real life. But so far i've learned alot from this
and for those interested i used this nifty Converter!
and this is the tire calculator!
[ April 15, 2002, 12:14 PM: Message edited by: Decker ]
i don't know what i was thinking, i checked back at the site. The stock circumpherence is 1870.81mm and the new one is 1936.16mm.
So assuming that there's a +5% change (above 100mph) and there's a 10% degree of error.
135*1.05=141.75mph max
so it would be anywhere from 127mph-141.75mph realistically. which makes it alot more realistic if it was 127mph smile.gif 141(is a pipe dream huh?)
anyway, stealing a formula from mario's 150mph post
using the formula
Power in kW p=(12.9x10**-6)*q*c*A*V*(V+WV)**2
if it was 127mph/204.40kph (minimum)
p=(12.9x10**-6)*1.202*0.33*2.5087*204.40*(204.40+0)**2
p=0.0000129*1.202*0.33*2.5087*204.40*((204.40)**2)
p=>109.62Kw 147wHP
if it was 141mph/226kph (maximum)
p=0.0000129*1.202*0.33*2.5087*226.93*((226.93)**2)
p=>150.01Kw 201wHP !! eek!
I beleive my hp to be around 160ish with my mods. Definetly being optimistic. So its more likely i was at the 130mph-ish mark then the 140mph-ish mark in real life. But so far i've learned alot from this
and for those interested i used this nifty Converter!and this is the tire calculator!
[ April 15, 2002, 12:14 PM: Message edited by: Decker ]
Guest
Posts: n/a
ok smaller tire = faster speed on speedo therefore the car will tihnk you are going further than you really are therefore the mileage will be higher therefore shortening your warrenty. And vice versa if bigger tires are used. The percentage would stay the same no matter how fast your going smile.gif I was wrong about that. But the difference you would notice still gets bigger the faster you go. smile.gif smaller tires make the speedo read too fast and the mileage to read too long.
Senior Member
Joined: Feb 2002
Posts: 463
Likes: 0
QUOTE
Canadian Prairie Shark:
205mm and 195mm are the tire width not height.
Hey buddy, you're right but i didn't just post "205" or "195". I posted to whole tire size...P205/40/R17 40 designating the side wall ratio from the width. A 40 series side wall will be much taller on a tire measuring 275 than that of a 205 because it's a ratio/percentage of the width that gives it's side wall height. I thought you guys already knew that......205mm and 195mm are the tire width not height.
Rich