Big Question : RPMS/Highways/20's....
#1
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Big Question : RPMS/Highways/20's....
I've never really noticed it until yesterday when I was on the highway with my 20's (chrome), and I was trying to go past 90... I know its not a good idea because the rims are at a higher risk of being damaged, but when I was at 90, my RPMS stayed between 5/6....... Not only was it so high, but it felt like I could not go any faster....
Fastest ive been is 120 mph without the rims, and the rpms were not shooting up through the roof.....
My question is: With rims, do you have to go slower on the highway (50-60ish) to not destroy your tranny/car...??
Also, driving fast with rims is a bad thing ... correct??
Fastest ive been is 120 mph without the rims, and the rpms were not shooting up through the roof.....
My question is: With rims, do you have to go slower on the highway (50-60ish) to not destroy your tranny/car...??
Also, driving fast with rims is a bad thing ... correct??
#2
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Originally Posted by gbpackers4
I've never really noticed it until yesterday when I was on the highway with my 20's (chrome), and I was trying to go past 90... I know its not a good idea because the rims are at a higher risk of being damaged, but when I was at 90, my RPMS stayed between 5/6....... Not only was it so high, but it felt like I could not go any faster....
Fastest ive been is 120 mph without the rims, and the rpms were not shooting up through the roof.....
My question is: With rims, do you have to go slower on the highway (50-60ish) to not destroy your tranny/car...??
Also, driving fast with rims is a bad thing ... correct??
Fastest ive been is 120 mph without the rims, and the rpms were not shooting up through the roof.....
My question is: With rims, do you have to go slower on the highway (50-60ish) to not destroy your tranny/car...??
Also, driving fast with rims is a bad thing ... correct??
Driving fast period is a bad thing if you don't know what your'e doing but rims are rims as long as they are mounted, balanced and torqued properly, as for rpm's unless your shifter was in overdrive off mode I don't know but 20's won't cause your rpm's to jump like that.
#3
Seems excessive to me. I've been to 90 a few times with my 20s and the revs weren't all that high.
The issue at hand here is the circumference of the wheel has changed which will in turn effect the overall gearing ratio in relationship to 1 full rotation of the tire. In effect, one rotation of the wheel will take longer to do thus increasing your revs to move the same distance.
In this instance it has less to do with weight, and more to do with circumference .
The issue at hand here is the circumference of the wheel has changed which will in turn effect the overall gearing ratio in relationship to 1 full rotation of the tire. In effect, one rotation of the wheel will take longer to do thus increasing your revs to move the same distance.
In this instance it has less to do with weight, and more to do with circumference .
#4
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ok, first of all, when you say 80 or 90 i think you are rerferring to just the speedo, right? if so, i can tell you one thing for sure, having 20s will NOT change any of your speedo setup. it will affect your REAL speed, but the speedo only looks at the speed sensor at the wheels calculating the revolutions, it won't know the overall diameter change
and 5000 to 6000 rpm at 90mph, something is terribly wrong with your car (if you are not accelerating hard at that time). on a stock gs400 for example, at 80mph cruising, it's about 2800rpm. at 90, i would say at most 4000 (should be lower than that). my car with the rear super lsd, that's what changes the rpm. and even with my lsd, at 80mph (on speedo) it's only 3000rpm
and for the record, i have 20s too
and 5000 to 6000 rpm at 90mph, something is terribly wrong with your car (if you are not accelerating hard at that time). on a stock gs400 for example, at 80mph cruising, it's about 2800rpm. at 90, i would say at most 4000 (should be lower than that). my car with the rear super lsd, that's what changes the rpm. and even with my lsd, at 80mph (on speedo) it's only 3000rpm
and for the record, i have 20s too
#6
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Originally Posted by Tranman
sounds like its not shifting into fifth gear...
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#8
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Originally Posted by JeffTsai
Bigger rims will actually make your speedo read lower than your actual speed. Since the circumference of the whole wheel is bigger now....if the speedo says you're going 80, in reality you are probably going 83-85 or so.
#9
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Something similar happened to me one day although I dont recall the speed nor the exact RPMs. I only noticed that the RPMs were way too high. I just bumped the shift to the right a little like I was manually shifting from 4 to D and all was well. Hasnt happened since though.
#10
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Originally Posted by JeffTsai
Bigger rims will actually make your speedo read lower than your actual speed. Since the circumference of the whole wheel is bigger now....if the speedo says you're going 80, in reality you are probably going 83-85 or so.
for example, if you have stock wheels (or any wheels in spec):
speedo = 80mph
rpm = 2800rpm
actual speed (by radar) = 80mph
if you have 20s with overspec diameters:
speed = 80mph
rpm = 2800rpm
actual speed (by radar) = 83mph (for example)
the above case is true. however, to the car it still think it's going at 80mph.
#12
Good grief. The size of the wheel makes absolutely no difference. It's the overall outside diameter of the tire that creates the difference.
You can put on 20s all you want as long as you keep the outside diameter of the tire as close to the stock size as possible.
And yes. Your speedometer / tachometer relationship doesn't change no matter what size tire/wheel combo you throw on.
Calculate actual speed difference here:
http://350zx.com/tire-wheel.html
You can put on 20s all you want as long as you keep the outside diameter of the tire as close to the stock size as possible.
And yes. Your speedometer / tachometer relationship doesn't change no matter what size tire/wheel combo you throw on.
Calculate actual speed difference here:
http://350zx.com/tire-wheel.html
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