Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs: | reply to pitroad01
Re: Tire size question
You are welcome! Glad to help when I can.  |
|
pitroad01
join:2006-07-10
Raleigh, NC
 ·Time Warner VOIP
 ·RoadRunner Cable
| reply to pitroad01
Well I purchased a set of P185/70/R14 and sold my old tires to a used tire shop for $40. I paid $336.82 for the new set ... so net paid to correct this mess was $296.42.
The car sure looks better with the taller tire and I took a drive with my GPS aboard and speed and distance are very close now. I think doc said "when your speedometer is reading 60mph you are actually traveling 59.96mph".
The info provided here saved me a lot of money
(I thought I would need to buy 15" rims and tires) and I do appreciate it. |
|
Its a Secret
Whatever
Premium
join:2008-02-23
U B Funny
·Shaw
| reply to Doctor Olds
said by Doctor Olds  :Your vehicle has to be squirrelly in the rain and snow or on muddy streets. Actually, rock solid in snow or rain, and I get the best (or worst) of both where i am. Not much mud though...  said by uber69er :Having raced for decades I am quite aware of tire inflation characteristics. I hear ya. Bike racer here. I go by the 10% pressure rise rule i.e. cold to hot shouldn't be more than a 10% rise in pressure. If so, it's under-inflated. But, I am a bit old school sometimes.
--
"In the future, that which is not mandatory will be illegal"
"Nobody knows the age of the human race, but everybody agrees that it is old enough to know better" - Anonymous |
|
uber69er
join:2009-03-19
North of You
| reply to Its a Secret
said by Its a Secret :Interesting Doc. I've filled my tires this way for years, and have never had a problem. They always run smooth, quiet and get exceptional mileage out of them. I've never experienced increased center wear either. I've got the same experience and hundreds of thousands of kilometers to prove it in rain snow you name it.
Plus Canada to Key West every winter. I do drop down to 32 psi in heavy snow. Must be lucky so far too.
Having raced for decades I am quite aware of tire inflation characteristics. |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| reply to Its a Secret
Your vehicle has to be squirrelly in the rain and snow or on muddy streets. You may have just been lucky up to now.
|
|
Its a Secret
Whatever
Premium
join:2008-02-23
U B Funny
·Shaw
| reply to Doctor Olds
Interesting Doc. I've filled my tires this way for years, and have never had a problem. They always run smooth, quiet and get exceptional mileage out of them. I've never experienced increased center wear either.
While I value your expertise, my personal experiences have shown me differently. Puzzling.
--
"In the future, that which is not mandatory will be illegal"
"Nobody knows the age of the human race, but everybody agrees that it is old enough to know better" - Anonymous |
|
pitroad01
join:2006-07-10
Raleigh, NC
·Time Warner VOIP
·RoadRunner Cable
| reply to pitroad01
Well I think I'm going with a set of Kumho P185/70R14. Can get a set installed/balanced/stems/tax for $340.85 'out the door'. Free rotation & balance for the life of the tire. It has a 85k mile warranty. Now I have to get rid of the P185/60/R14's that are currently on the car. Thanks for all the help. |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| reply to Its a Secret
said by Its a Secret :One other thing... I run 70% aspect ratios myself, but fill them to 40 psi 40 PSI is a lot higher than most 70 Series as they have a 35 PSI (Some 36 PSI) Max Pressure. 40 PSI tire inflation is a bit past the dangerous side when the max inflation is 35 PSI.
Air Pressure - Correct, Underinflated and Overinflated
»www.tirerack.com/tires/tiretech/···techid=1
Unless you have ordered and installed "extra load" tires (that designation would be stamp into the sidewall), you are driving under dangerous conditions. You have less tire contact patch with the road, you have increase noise and you have a higher risk of a blow out from foreign object impacting the tire as it is beyond it designed stiffness not to forget the accelerated wear of the center of the tire taking away any partial MPG increase you may see. Saving $10.00 to $15.00 on gas isn't smart when you throw away $50.00 to $75.00 worth of tire wear/tread life.
North American Load and Pressure Markings
»www.tirerack.com/tires/tiretech/···echid=21
Sizing System Tire Load Range Load Pressure
P-metric Light Load 35 psi
Standard Load 35 psi
Extra Load 41 psi
Euro-metric Standard 36 PSI
Reinforced or Extra Load 42 PSI
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
Its a Secret
Whatever
Premium
join:2008-02-23
U B Funny | reply to pitroad01
One other thing... I run 70% aspect ratios myself, but fill them to 40 psi with nitrogen to minimize sidewall flex, and get great wear life. Just a thought. |
|
Its a Secret
Whatever
Premium
join:2008-02-23
U B Funny | reply to pitroad01
You'll get better gas mileage as well.  |
|
pitroad01
join:2006-07-10
Raleigh, NC | reply to Doctor Olds
yea maybe the P185/70/R14
It would probably look a lot better then a really wide tire (225) |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| reply to BonezX
said by BonezX :if it doesn't clear the brake calipers or impedes proper cooling of the brakes it is a problem. also having smaller tires effects braking, as well as other things He already has had the 14" Rims and has been driving on them since he got the car and changing the tires size will not make any changes to the existing rims dimensions. The Value Edition Model in 2005 comes with the same 14" Rim.
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| reply to pitroad01
said by pitroad01 :So what you are saying is that I could correct my problem with a 225/60/14 ...... I wonder if that tire would fit on my current 14" rim ? Actually the 70 Series fits better with the closest to the original revolutions per mile.
This helps visually:
»www.miata.net/garage/tirecalc.html
The second choice 225/60-14
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
BonezX
Basement Dweller
Premium
join:2004-04-13
Canada
1 edit | reply to aurgathor
said by aurgathor :Wheel diameter is mostly irrelevant, it's the outside diameter of the tire that matters. if it doesn't clear the brake calipers or impedes proper cooling of the brakes it is a problem.
also having smaller tires effects braking, as well as other things |
|
pitroad01
join:2006-07-10
Raleigh, NC | reply to Doctor Olds
So what you are saying is that I could correct my problem with a 225/60/14 ...... I wonder if that tire would fit on my current 14" rim ? |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| reply to pitroad01
If you want the same width tire then:
Original tire [195/60-15]
Sidewall: 4.61 in
Radius: 12.11 in
Diameter: 24.21 in
Circumf: 76.07 in
Revs/mile: 832.96
New Tire [215/60-14]
Sidewall: 5.08 in
Radius: 12.08 in
Diameter: 24.16 in
Circumf: 75.89 in
Revs/mile: 834.86
Speedometer reading with new tire is 0.23% too fast.
When your speedometer is reading 60mph you are actually traveling 59.86mph.
or
Original tire [195/60-15]
Sidewall: 4.61 in
Radius: 12.11 in
Diameter: 24.21 in
Circumf: 76.07 in
Revs/mile: 832.96
New Tire [225/60-14]
Sidewall: 5.31 in
Radius: 12.31 in
Diameter: 24.63 in
Circumf: 77.38 in
Revs/mile: 818.85
Speedometer reading with new tire is 1.72% too slow.
When your speedometer is reading 60mph you are actually traveling 61.02mph.
or 65 series (not as wide)
Original tire [195/60-15]
Sidewall: 4.61 in
Radius: 12.11 in
Diameter: 24.21 in
Circumf: 76.07 in
Revs/mile: 832.96
New Tire [205/65-14]
Sidewall: 5.25 in
Radius: 12.25 in
Diameter: 24.49 in
Circumf: 76.94 in
Revs/mile: 823.45
Speedometer reading with new tire is 1.15% too slow.
When your speedometer is reading 60mph you are actually traveling 60.68mph.
or 70 series
Original tire [195/60-15]
Sidewall: 4.61 in
Radius: 12.11 in
Diameter: 24.21 in
Circumf: 76.07 in
Revs/mile: 832.96
New Tire [185/70-14]
Sidewall: 5.10 in
Radius: 12.10 in
Diameter: 24.20 in
Circumf: 76.02 in
Revs/mile: 833.50
Speedometer reading with new tire is 0.07% too fast.
When your speedometer is reading 60mph you are actually traveling 59.96mph.
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
pitroad01
join:2006-07-10
Raleigh, NC
·Time Warner VOIP
·RoadRunner Cable
| reply to Doctor Olds
said by Doctor Olds :said by markwp2001 :I believe he got the 7% figure The difference value is seen in the post directly above yours which was determined by » www.tiresizecalculator.info/ after the tire sizes were posted. That's a neat site. I'm sure their numbers are correct. I guess I'm stuck. I was hoping they could make a change in the car processor to calculate speed and distance with a 14" tire but evidently they can't. I wonder if there is a certain size 14" that would work ? |
|
Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| reply to markwp2001
said by markwp2001 :I believe he got the 7% figure The difference value is seen in the post directly above yours which was determined by »www.tiresizecalculator.info/ after the tire sizes were posted.
--
What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
|
pitroad01
join:2006-07-10
Raleigh, NC
·Time Warner VOIP
·RoadRunner Cable
| reply to markwp2001
said by markwp2001 :said by Doctor Olds :said by pitroad01 :Well I found out that running 14" tires on a car that was built for 15" causes the speedometer and odometer to error. The tire size is programed into the cars processors. So my speed and mileage are off by about 7%. You are leaving out what size the Tire is that is installed on the 14" rim. Without knowing that and without knowing a few other factors you are possibly incorrect about the 7% difference. I believe he got the 7% figure by comparing his odometer reading to the GPS reading of miles driven. I threw out the figures I had recorded for the trip but it came to like 93% .... + or - a little. |
|
markwp2001
Spreadhead
Premium
join:2002-05-25
Long Beach, MS
| reply to Doctor Olds
said by Doctor Olds :said by pitroad01 :Well I found out that running 14" tires on a car that was built for 15" causes the speedometer and odometer to error. The tire size is programed into the cars processors. So my speed and mileage are off by about 7%. You are leaving out what size the Tire is that is installed on the 14" rim. Without knowing that and without knowing a few other factors you are possibly incorrect about the 7% difference. I believe he got the 7% figure by comparing his odometer reading to the GPS reading of miles driven.
--
Into music? tealeafgreen.com |
|
