changing wheel size
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2nd Gear
Joined: May 2005
Posts: 72
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From: Phoenix, AZ
changing wheel size
forgive my brainfart but if you go from a 17in wheel to say... anything else, you'd have to make an adjustment to the spedo right? i mean unless it measures actual dist/time, the spedo will give measurements in error due to the fact that per each rotation of the wheel, a larger wheel will travel more dist than a smaller one.
unless you are pedaling on a very old race bike, any spedo now a days on any vehicle takes the diameter of the wheel does a calc for circumference and then multiplys by the tach reading.
I see people talk about changing wheel size for what ever reason but i have yet to see a thread in which anyone mentioned adjusting the spedo.
just curious, thanks for your time.
unless you are pedaling on a very old race bike, any spedo now a days on any vehicle takes the diameter of the wheel does a calc for circumference and then multiplys by the tach reading.
I see people talk about changing wheel size for what ever reason but i have yet to see a thread in which anyone mentioned adjusting the spedo.
just curious, thanks for your time.
4th Gear
Joined: Apr 2005
Posts: 410
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From: Calgary, Alberta
Try the MINI2 FAQ (http://www.mini2.com/forum/faq.php?f...factory_wheels)
Or use the calculator at Tire Size Calculator. It shows exactly how much your speedometer reading will change with different tire sizes.
On street cars, it should have an overall diameter that is within ±3% of the factory specification. The ±3% variation is recommended for street cars in order to maintain accurate speed data going into the computer, thus keeping odometer and speedometer changes negligible. While a ±3% diameter increase or reduction in tire diameter may sound very limiting, in most cases it allows approximately a ±3/4" diameter change.
Assuming 24.00" (609.6mm) as the factory specification for overall diameter, any of the following tire sizes may be appropriate:
+-----------+-------------------+
| TIRE SIZE | DIAMETER |
+-----------+-------------------+
| 195/55-15 | 23.44in (595.5mm) |
| 205/40-17 | 23.46in (595.8mm) |
| 215/50-15 | 23.46in (596.0mm) |
| 215/45-16 | 23.62in (599.9mm) |
| 195/50-16 | 23.68in (601.4mm) |
| 185/60-15 | 23.74in (603.0mm) |
| 215/40-17 | 23.77in (603.8mm) |
| 205/55-15 | 23.88in (606.5mm) |
| 215/35-18 | 23.93in (607.7mm) |
| 175/65-15 | 23.96in (608.5mm) |
| 225/45-16 | 23.97in (608.9mm) |
| 205/50-16 | 24.07in (611.4mm) |
| 225/40-17 | 24.09in (611.8mm) |
| 225/35-18 | 24.20in (614.7mm) |
| 195/60-15 | 24.21in (615.0mm) |
| 205/45-17 | 24.26in (616.3mm) |
| 215/55-15 | 24.31in (617.5mm) |
| 195/55-16 | 24.44in (620.9mm) |
| 215/50-16 | 24.46in (621.4mm) |
| 185/65-15 | 24.47in (621.5mm) |
| 215/45-17 | 24.62in (625.3mm) |
+-----------+-------------------+
NOTES:
Stock fitments are highlighted
Fitment dependent on wheel offset and suspension setup
Tires availabilty may be limited in certain sizes
Assuming 24.00" (609.6mm) as the factory specification for overall diameter, any of the following tire sizes may be appropriate:
+-----------+-------------------+
| TIRE SIZE | DIAMETER |
+-----------+-------------------+
| 195/55-15 | 23.44in (595.5mm) |
| 205/40-17 | 23.46in (595.8mm) |
| 215/50-15 | 23.46in (596.0mm) |
| 215/45-16 | 23.62in (599.9mm) |
| 195/50-16 | 23.68in (601.4mm) |
| 185/60-15 | 23.74in (603.0mm) |
| 215/40-17 | 23.77in (603.8mm) |
| 205/55-15 | 23.88in (606.5mm) |
| 215/35-18 | 23.93in (607.7mm) |
| 175/65-15 | 23.96in (608.5mm) |
| 225/45-16 | 23.97in (608.9mm) |
| 205/50-16 | 24.07in (611.4mm) |
| 225/40-17 | 24.09in (611.8mm) |
| 225/35-18 | 24.20in (614.7mm) |
| 195/60-15 | 24.21in (615.0mm) |
| 205/45-17 | 24.26in (616.3mm) |
| 215/55-15 | 24.31in (617.5mm) |
| 195/55-16 | 24.44in (620.9mm) |
| 215/50-16 | 24.46in (621.4mm) |
| 185/65-15 | 24.47in (621.5mm) |
| 215/45-17 | 24.62in (625.3mm) |
+-----------+-------------------+
NOTES:
Stock fitments are highlighted
Fitment dependent on wheel offset and suspension setup
Tires availabilty may be limited in certain sizes
Originally Posted by CarbonChrome
forgive my brainfart but if you go from a 17in wheel to say... anything else, you'd have to make an adjustment to the spedo right? i mean unless it measures actual dist/time, the spedo will give measurements in error due to the fact that per each rotation of the wheel, a larger wheel will travel more dist than a smaller one.
unless you are pedaling on a very old race bike, any spedo now a days on any vehicle takes the diameter of the wheel does a calc for circumference and then multiplys by the tach reading.
I see people talk about changing wheel size for what ever reason but i have yet to see a thread in which anyone mentioned adjusting the spedo.
just curious, thanks for your time.
unless you are pedaling on a very old race bike, any spedo now a days on any vehicle takes the diameter of the wheel does a calc for circumference and then multiplys by the tach reading.
I see people talk about changing wheel size for what ever reason but i have yet to see a thread in which anyone mentioned adjusting the spedo.
just curious, thanks for your time.
If you change your "rolling stock" size by a percentage greater than acceptable (2-3%), then yes, you'd need to alter your speedo, and probably gearing.
But when you change wheel size, you usually make the difference up with a change in tire size. Specifically the tire sidewall size. The total diameter of your new tires will be essentially the same as stock, but the sidewalls will be different.
Bigger wheel + smaller tire sidewall dimension = same total rolling stock.
Or.... Smaller wheel + bigger sidewall dimension = same total rolling stock.
Unless you feel like putting a lift kit on your mini. Now that'd be a sight!
EDIT: Now I typed all of that and realized it's basically posted above... DOH! I coulda just typed... "Yeah, what YYC said..."
6th Gear
Joined: Aug 2003
Posts: 1,474
Likes: 3
From: Over there -->
My 2004 MCS's speedometer reads a constant 3 mph fast on x-lites with 195/55-16 tires. Thus I could go up a bit in rolling stock circumference and still not read faster than actual MPH.
So, get a GPS or a friendly roadside radar setup and keep your speed constant as you pass. I did mine a 60 mph. Note the difference in what the speedometer reads and what the GPS/radar reads. Now, go to the tire size calculator and play around, making sure that the resulting speed increase (from standard 60 MPH) is no more than the difference noted above.
In effect, you have "calibrated" your speedometer by altering the circumference of your tires.
Theo
So, get a GPS or a friendly roadside radar setup and keep your speed constant as you pass. I did mine a 60 mph. Note the difference in what the speedometer reads and what the GPS/radar reads. Now, go to the tire size calculator and play around, making sure that the resulting speed increase (from standard 60 MPH) is no more than the difference noted above.
In effect, you have "calibrated" your speedometer by altering the circumference of your tires.
Theo
OVERDRIVE - Racing Champion
Joined: Feb 2003
Posts: 15,262
Likes: 72
From: Mililani, Hawaii
Personally I luv to drive with smaller diameter tires on the street like 205/50-15. The speedo error is great for making you think you're going faster but you're really not. 
Hey, that means I've got odometer error too!
Oh well. Time for the ultra tall tires to even out the error. 
Hey, that means I've got odometer error too!
Oh well. Time for the ultra tall tires to even out the error.
Thread Starter
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2nd Gear
Joined: May 2005
Posts: 72
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From: Phoenix, AZ
and so
if I wanted to/ended up going with tires that were more than that +/- 3% how would i go about adjusting the spedo and odo? Also why would i need to change the gearing?
I realize this is perhaps getting away from the purpose of the discussion zone but, oh well
I realize this is perhaps getting away from the purpose of the discussion zone but, oh well
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Originally Posted by CarbonChrome
if I wanted to/ended up going with tires that were more than that +/- 3% how would i go about adjusting the spedo and odo? Also why would i need to change the gearing?
I realize this is perhaps getting away from the purpose of the discussion zone but, oh well
I realize this is perhaps getting away from the purpose of the discussion zone but, oh well
You may know this, so forgive me for being redundant: But you will find that the car will most likely suffer nominally in performance and fuel consumption. The gearbox ratios are all engineered to get the best response from the engine's torque curve, while maintaining fuel mileage. When you vary one element of the powertrains relationship of parts excessively, you'll certainly notice. I wouldn't consider a few percentage point differences from stock "excessive" but more nominal.
By comparison, the folks who put huge tires and lift kits on thier trucks certainly are affecting all of the aformentioned areas.
6th Gear
Joined: Aug 2003
Posts: 1,474
Likes: 3
From: Over there -->
An owner cannot adjust the speedometer. This is done on purpose for legal reasons. Something about the high-side calibration getting MINI/BMW off the liability hook in certain circumstances. This would also mean that the dealer would not be able to adjust the speedo either.
This is my recollection, but then again, the 60's were good to me!!
Theo
This is my recollection, but then again, the 60's were good to me!!
Theo
OVERDRIVE - Racing Champion
Joined: Feb 2003
Posts: 15,262
Likes: 72
From: Mililani, Hawaii
Originally Posted by CarbonChrome
hmmm, okay then. heh its all moot anyway i have yet to see a rim for minis larger than 18inches:smile:
At edgeracing.com see
http://edgeracing.com/wheels/falken_wheel/
19x7.5" rims 4x100
Circuit Spec (gunmetal or silver) $175 each +42mm offset 26 pounds
Torque 5 chrome $245 +42mm offset 26.5 pounds
Torque 5 (gun metal or silver) $195 +42mm offset 25.5 pounds
At tirerack.com see
TIS wheels in 20x7.5"
http://www.tirerack.com/a.jsp?a=EZ3&url=/wheels/tis/tis.jsp
Four models TIS 02,03,06,and 07 chrome plated
Use tire 225/30-20 BFG G-Force KDW2 $265 each 25.5" tire diam!
http://www.centerlinewheels.com/whee...id=16&sw_id=85
Storm series 19x7.5" 4x100 bolt pattern +42mm wheel offset
Or Centerline RPMs in 19x7.5" 4x100 +42mm offset
http://www.centerlinewheels.com/whee..._id=4&sw_id=27
You can use a 215/35-19 tire but the outer tire diameter is going to be larger than stock at about 25.0" so a minimal drop of 0.5 or 3/4" might work or use coil overs with adjustable ride height to minimize rubbing.
Tirerack.com has many tires from about $150+ each (talk to Alex)
Avon tech M500
BFG G-Force T/A KDW2
Yokohama Parada Spec-2
Kumho Ecsta SPT KU31
Pirelli P Zero Nero M+S
Last edited by Alex@tirerack; May 17, 2005 at 12:04 PM. Reason: added tracking inforation, giving NAM more click thru credit!
Thread Starter
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2nd Gear
Joined: May 2005
Posts: 72
Likes: 0
From: Phoenix, AZ
oooooh, pretty!
so then lets say i went with something that size. i would need to make an adjustment to the spedo and odo (or rather, find someone that can make that adjustment for me) but JCW driver was saying that it would affect performance? aside from the fact that a larger tire actually has the percieved effect of smoothing out the road, I cant really see any other way the tire change would affect the performance. Any ideas?
so then lets say i went with something that size. i would need to make an adjustment to the spedo and odo (or rather, find someone that can make that adjustment for me) but JCW driver was saying that it would affect performance? aside from the fact that a larger tire actually has the percieved effect of smoothing out the road, I cant really see any other way the tire change would affect the performance. Any ideas?
The larger wheel tire combo will slow your car some, unless the overall weight (actually mass) is lower than stock. It will also make your odometer slightly inaccurate.
The Centerline rims are costly, but very light. Nice rims.
The Centerline rims are costly, but very light. Nice rims.
Thread Starter
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2nd Gear
Joined: May 2005
Posts: 72
Likes: 0
From: Phoenix, AZ
so the detriment to the car is just in the new (proposed) wheel's rotational mass? no problems then
um, about adjusting the speedo and odo, if neiter bmw/mini nor myself my legaly adjust my spedo/odo, um, where would i go to get that done?
um, about adjusting the speedo and odo, if neiter bmw/mini nor myself my legaly adjust my spedo/odo, um, where would i go to get that done?
6th Gear
Joined: Sep 2002
Posts: 3,343
Likes: 4
From: South Bend Indiana
Originally Posted by CarbonChrome
um, about adjusting the speedo and odo, if neiter bmw/mini nor myself my legaly adjust my spedo/odo, um, where would i go to get that done?
Alex
Thread Starter
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2nd Gear
Joined: May 2005
Posts: 72
Likes: 0
From: Phoenix, AZ
no disrespect or nothing and,
well, call me **** retentive but anything worth doing is worth doing right. if i get 22's i want a working spedo and odo to go with it. especially the odo since, if i were to sell the car i want an accurate representation of mileage.
easier just to say you dont know where to go than to tell me theres no point in getting the change made since its 'close enuf'.
easier just to say you dont know where to go than to tell me theres no point in getting the change made since its 'close enuf'.
6th Gear
Joined: Sep 2002
Posts: 3,343
Likes: 4
From: South Bend Indiana
No offence intended
easier just to say you dont know where to go than to tell me theres no point in getting the change made since its 'close enuf'.
Alex
Last edited by Alex@tirerack; May 18, 2005 at 07:13 AM.
OVERDRIVE - Racing Champion
Joined: Feb 2003
Posts: 15,262
Likes: 72
From: Mililani, Hawaii
Originally Posted by Alex@tirerack
225/30/20 is only 4% deviant - Your speedo reads 60 mph, you're traveling 62.4
Alex
Alex
I don't know of any easy way to allow the speedo or odo to compensate for different outer tire diameters. But...
A search for "adjusting speedo calibration" shows:
http://www.turbotbird.com/techinfo/s...ng_desktop.htm
http://www.m.tsang.dial.pipex.com/dashboards.htm
http://www.dashboardprogramming.com/
For mechanical (gearing adjustment)
http://mgaguru.com/mgtech/dash/st201.htm
http://www.4x4wire.com/mitsubishi/tech/speedo-gear/
Originally Posted by CarbonChrome
so the detriment to the car is just in the new (proposed) wheel's rotational mass? no problems then
If you're going to get really ****, remember that a tire with full tread (10/32?) is bigger than a tire with minimal tread (3/32) - almost half an inch (7/32+7/32=14/32 or 7/16") in total diameter change over the life of the tire. Your speedo will only be right for a period of time.
OVERDRIVE - Racing Champion
Joined: Feb 2003
Posts: 15,262
Likes: 72
From: Mililani, Hawaii
Originally Posted by Eric_Rowland
No - it also changes the effective gearing of the car. A tire with a larger circumference will accellerate more slowly (given equal weight) than a tire wtih a smaller circumference because it's traveling a greater distance (doing more work.)
If you're going to get really ****, remember that a tire with full tread (10/32?) is bigger than a tire with minimal tread (3/32) - almost half an inch (7/32+7/32=14/32 or 7/16") in total diameter change over the life of the tire. Your speedo will only be right for a period of time.
If you're going to get really ****, remember that a tire with full tread (10/32?) is bigger than a tire with minimal tread (3/32) - almost half an inch (7/32+7/32=14/32 or 7/16") in total diameter change over the life of the tire. Your speedo will only be right for a period of time.
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2nd Gear
Joined: May 2005
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From: Phoenix, AZ
hehe, didnt even think about tire wear
and i do see what you mean about the gearing,
if the rotational mass were about the same and the wheels are larger than stock would'nt it also aside from slightly lowing acceleration have the effect of increased traction, just in the take off i mean. its been forever since i took physics so im just going to reason this out.
wheel A circumference == 1 wheel B circumference == 1.042
@wot A freespins 3 rotations, therefore B being larger and having roughly the same rotational mass would spin the same circumferential distance but fewer rotations then grabbig traction earlier. im thinking it would be earlier and not the same time because given the same rotational mass and no resistance a wheel spinning @1rpm with any diameter will still be traveling at 1rpm. Would not the same hold true for tires on a car?
oh right, also larger wheels meaning more land traveled per revolution would mean higher ungoverned top speed so better fuel economy, no?
thanks alot for all your help, and i appologize for being snippy, i had to deal with alot of evasiveness yesterday and i guess i took it out on the forum.
P.S. just woke up so my mathese may be stupid
and i do see what you mean about the gearing,
if the rotational mass were about the same and the wheels are larger than stock would'nt it also aside from slightly lowing acceleration have the effect of increased traction, just in the take off i mean. its been forever since i took physics so im just going to reason this out.
wheel A circumference == 1 wheel B circumference == 1.042
@wot A freespins 3 rotations, therefore B being larger and having roughly the same rotational mass would spin the same circumferential distance but fewer rotations then grabbig traction earlier. im thinking it would be earlier and not the same time because given the same rotational mass and no resistance a wheel spinning @1rpm with any diameter will still be traveling at 1rpm. Would not the same hold true for tires on a car?
oh right, also larger wheels meaning more land traveled per revolution would mean higher ungoverned top speed so better fuel economy, no?
thanks alot for all your help, and i appologize for being snippy, i had to deal with alot of evasiveness yesterday and i guess i took it out on the forum.
P.S. just woke up so my mathese may be stupid
OVERDRIVE - Racing Champion
Joined: Feb 2003
Posts: 15,262
Likes: 72
From: Mililani, Hawaii
Sizes like 195/55-16, 205/50-16 or 205/55-16.
For track and autocross you can do other sizes that are smaller tire diameter since it gives better gearing for going faster at lower speeds but you get speedo and odometer error if used on the street. An example is 205/45-16.
215/45-16 should fit rims 7-8" wide and the stock rim is 16x6.5" so it would not be a perfect fit but it is possible. When you put a wide tire on a narrow rim you make the tire tread effectively a little less so you loose some of the benefit of the 215mm width. Tire diameter is small at 23.6" vs 24.3" for stock.