New wheels = High Top Speed??
05-20-07, 07:03 PM
#1
New wheels = High Top Speed??
So i got some Konig rewinds 15x7 with 205/55 tires. I have a 85 with stock motor with a magnaflow muffler and with my stock 13's i really couldn't push more than 100 and last night I was cruising on the Interstate with a 2002 wrx and I kept up till 130. Now I'm not sure where that speed came from but it was shocking to me. Does the lighter wheel really make that big of a difference? Oh by the way Konig Rewinds Rock on the first Gens....Pics soon
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Yeah what Kentetsu said
05-20-07, 07:50 PM
#9
Are you sure the diameter is the same as stock? I have 245/50/15s on the widebody and my speedo reading is 10% less than actual speed. I would think that you would need to go to a 40 or 45 aspect to have the same diameter as stock. There are some tire ratio charts online, find one and compare the stock ratio to what you have now. The only possible explanation I can see atm if the tires are putting your engine in it's 'sweet spot' before the torque/hp curve drops off. Another thought is, does the WRX have stock tires on his car, maybe his speedo is off.
Best way to tell if the diameter is the same size is to look at the the revs/mile of each tire, i.e. how many times the tire makes a full revolution to travel a mile. Most tire shops have these charts.
Best way to tell if the diameter is the same size is to look at the the revs/mile of each tire, i.e. how many times the tire makes a full revolution to travel a mile. Most tire shops have these charts.
05-20-07, 10:07 PM
#15
love the braaaap
Your speedometer would be reading about 1.5% too fast, meaning that if your going 60mph according to the speedo, your actually going 59mph.
Got that from this site here: http://www.miata.net/garage/tirecalc.html
Got that from this site here: http://www.miata.net/garage/tirecalc.html
05-20-07, 11:33 PM
#18
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when i had the 83 limited wheels on my car it was capable of doing 120. mr. po po clocked me so I'm pretty sure i was really going that fast.
05-20-07, 11:59 PM
#19
Ok I'm glad I'm not the only nut here. It was quite strange for me. When I was going that fast, I honestly didn't believe it but when we all pulled over and asked how fast I didn't think it was possible. But with a slight down hill to the highway, I think that might have helped.
05-21-07, 12:15 AM
#20
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This is a very good tire size calculator http://www.miata.net/garage/tirecalc.html
tells you speedo difference in % and miles
tells you speedo difference in % and miles
05-21-07, 02:21 AM
#21
Terrified.
Ok I'm glad I'm not the only nut here. It was quite strange for me. When I was going that fast, I honestly didn't believe it but when we all pulled over and asked how fast I didn't think it was possible. But with a slight down hill to the highway, I think that might have helped.
05-21-07, 03:40 AM
#22
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Ok I have to respond to this!
I have an 83 GS with the stock wheels and tires, not even the good ones, off the top of my head I think theyre 185/65r13's. The previous owners had taken remarkable care and maintnence of the car, so everything was in really good shape.
Me and a friend were going to Boise from here.. I had just put on a holley intake. I-84 is a wonderful highway
He said it would take 8 hours, and I said we'll make it in 4 watch!!
So for 1 hour straight I was running between 110 and 135 mph.
On level ground the car maxed out at 120 with 2 ppl. and a bunch of stuff in the back.
I distinctly remember going around a corner and coming out of that turn at 120 mph. Right there was about a 2 mile straightaway at a very nice decline down hill.
WE HIT 133 MPH RIGHT AT 7000RPM
I was soooooo happy that the needle kept going past the top speed mark! I then
realized the car would hit 150 at 8000 rpm, but unfortunately didnt have that much power. At 133 the car handled like a dream, even hitting the next turn at that speed. The road leveled out and it was back to 120 mph at 6500 rpm. My right foot did not come off the floor at all
I have an 83 GS with the stock wheels and tires, not even the good ones, off the top of my head I think theyre 185/65r13's. The previous owners had taken remarkable care and maintnence of the car, so everything was in really good shape.
Me and a friend were going to Boise from here.. I had just put on a holley intake. I-84 is a wonderful highway
He said it would take 8 hours, and I said we'll make it in 4 watch!!
So for 1 hour straight I was running between 110 and 135 mph.
On level ground the car maxed out at 120 with 2 ppl. and a bunch of stuff in the back.
I distinctly remember going around a corner and coming out of that turn at 120 mph. Right there was about a 2 mile straightaway at a very nice decline down hill.
WE HIT 133 MPH RIGHT AT 7000RPM
I was soooooo happy that the needle kept going past the top speed mark! I then
realized the car would hit 150 at 8000 rpm, but unfortunately didnt have that much power. At 133 the car handled like a dream, even hitting the next turn at that speed. The road leveled out and it was back to 120 mph at 6500 rpm. My right foot did not come off the floor at all
05-21-07, 05:30 AM
#24
Speedo accuracy regardless of different
Diff Gears
Rolling wheel/tyre diameter
Gearbox gears
Speedo cable drive gears
Is absolutely ******* awful for a late 70s/early 80s car.
Don't be stupid and read the speedo like its Gospel.
I tested my car on a long drive. In australia we have Red marker pegs on the road every 1km on some stretches of our road. I worked out 135-140 was around 100kph on my car.
I have known inaccuracies of, different rolling diameter tyres, diff gears, wrong speedo drive for my rolling diameter (pretty sure it expects wheels around 14", and I have 13"s on lows
Diff Gears
Rolling wheel/tyre diameter
Gearbox gears
Speedo cable drive gears
Is absolutely ******* awful for a late 70s/early 80s car.
Don't be stupid and read the speedo like its Gospel.
I tested my car on a long drive. In australia we have Red marker pegs on the road every 1km on some stretches of our road. I worked out 135-140 was around 100kph on my car.
I have known inaccuracies of, different rolling diameter tyres, diff gears, wrong speedo drive for my rolling diameter (pretty sure it expects wheels around 14", and I have 13"s on lows
05-21-07, 06:54 AM
#25
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I have the same rim/tire combo and they are actually 4 pounds heavier each than the stock "+" wheels & tires. Take that back , I have 205/50 not 55. The car feels a little slower due to the wider tires, but is def. more stable in corners. This tire size was supposed to be closest to original rotational size but it does make my speedometer read slow. Per my gps I am running 3-4 mph faster @ 60 on the speedo. I have hit 130 (per the speedo) in an FB before, it took a while and hills helped. Scary as hell!