Got a New (Used) Car...But...

[alimoalem]

The car is a 1997 Nissan 200SX SE-R. My uncle had it at his auto shop in the back for a few months and forgot about it. One day he remembered it and knew I was looking for a car so he pretty much gave it to me.

Anyway, the car has 159,000 miles on it and the car was originally automatic. The previous owner (before my uncle) converted it to a 5-speed manual transmission.

*** brace yourself for newb questions ***

Engine Question: for every 500rpm in 5th gear, the car goes up 10mph. Translation: at 60mph, your engine's at 3000rpm. at 80mph, your engine's at 4000rpm. That seems pretty high, imo. What is a safe constant rpm for the engine to run at? I'm going to be going on > 1 hour trips quite often so i don't want to put prolonged stress on the engine.

Btw, if the manual tranny was stock, I would've assumed 3-4k rpm constantly is expected from the car but seeing how it's not stock, it concerns me.

Tire Questions: the car has 15" wheels stock (tires 195/55/15). Currently the car has 17's on it (tires 205/40/17). Do I have to be overly cautious when it comes to pot holes/bumps/etc. in the road or can low-profile tires take the same amount of beating as the "regular" tires?

Also, the rims are aluminum. Would that make any difference on how wary i should be of the aforementioned road hazards?

Thanks a lot in advance. Any help is really really appreciated.

 

[herm0016]

the rear end gears are probably not tall enough ( high enough ratio) to work well with the manual. put stock tires and wheels back on it, it will ride better and will not wear out the suspension as fast.

 

[alimoalem]

thanks for the quick reply herm0016.

my uncle said he could change the gear ratios but it sounded like a lot of work so i don't want to ask him for help with that if it's not necessary. that's why i'm asking about the rpms.

about the wheels, i like how it looks right now . i just don't know if they can handle as much impact as standard tires.

 

[Eli]

You can safely run the engine at any RPM between 0 and redline.

Its an SE-R. It has tall ratios. Thats normal. The car wasn't geared for highway cruising.

Realize that your speedometer is off if it has larger tires. You could easily be going 10MPH faster than it says you are.

 

[Black88GTA]

Originally posted by: alimoalem
thanks for the quick reply herm0016.

my uncle said he could change the gear ratios but it sounded like a lot of work so i don't want to ask him for help with that if it's not necessary. that's why i'm asking about the rpms.

about the wheels, i like how it looks right now . i just don't know if they can handle as much impact as standard tires.

You are much more likely to damage a tire / bend a rim with low profiles + 17s than you are with the stock setup. There's not as much flexible rubber sidewall to absorb impacts, so the rim is forced to absorb more abuse than one with a thicker tire on it.

Just dodge around potholes as much as possible, and go slowly over them when they are unavoidable. You'd have to hit one pretty hard to do permanent damage, even with low profiles.

 

[alimoalem]

really (to the redline thing)? thanks for the reply eli

i also thought about the tires being off and asked my dad about it and he confirmed but i calculated the diameter of the stock wheels and the current ones and it came out to be the same. the diameter is all that matters right?

btw, this is how i calculated the diameter. i got the radius of both wheels and multiplied by 2.

tires are 195/55/15 (stock) so 195mm*55% is the size of the wheel wall + 7.5" (half the rim length).
7.5" = 190.5mm
195mm *55% = 107.25
radius = 297.75, diameter = 595.5mm

current tire are 205/40/17...205mm*40% = 82mm. 8.5" is half the rim length.
8.5" = 215.9mm
205*40% = 82mm.
radius = 297.9mm, diameter = 595.8mm

now i realize this could be totally wrong, but mathematically it made sense to me

 

[alimoalem]

Originally posted by: Black88GTA

You are much more likely to damage a tire / bend a rim with low profiles + 17s than you are with the stock setup. There's not as much flexible rubber sidewall to absorb impacts, so the rim is forced to absorb more abuse than one with a thicker tire on it.

Just dodge around potholes as much as possible, and go slowly over them when they are unavoidable. You'd have to hit one pretty hard to do permanent damage, even with low profiles.

that's what i was looking for. ok so you know the right-most lanes that the 18-wheelers use? you know how on old roads they're cracked and stuff, REALLY badly in some places? the 200sx has a lot firmer suspension than the mazda protege i'm used to so i'll bounce around like a motherlover going over them, but you think it'll be relatively safe for the (aluminum) rims if i go over them at say 70? i know it depends on the road, etc, but just like the average cracks and bumps.

i know i know, true newb talking.

btw, thanks for the reply black88gta

 

[Black88GTA]

You're right - you'll bounce all over the place on the cracked areas. But you shouldn't damage anything over "average" broken areas of road. You'd only really have to worry about major potholes. One good hit to a giant hole can ruin your day.

Make sure you keep your tires properly inflated too - this is especially important on low profiles for exactly this reason. If tire pressure is low, and you hit a big pothole, you are more likely to dent a rim or mess up a tire.

 

[JulesMaximus]

Originally posted by: alimoalem

Originally posted by: Black88GTA

You are much more likely to damage a tire / bend a rim with low profiles + 17s than you are with the stock setup. There's not as much flexible rubber sidewall to absorb impacts, so the rim is forced to absorb more abuse than one with a thicker tire on it.

Just dodge around potholes as much as possible, and go slowly over them when they are unavoidable. You'd have to hit one pretty hard to do permanent damage, even with low profiles.

that's what i was looking for. ok so you know the right-most lanes that the 18-wheelers use? you know how on old roads they're cracked and stuff, REALLY badly in some places? the 200sx has a lot firmer suspension than the mazda protege i'm used to so i'll bounce around like a motherlover going over them, but you think it'll be relatively safe for the (aluminum) rims if i go over them at say 70? i know it depends on the road, etc, but just like the average cracks and bumps.

i know i know, true newb talking.

btw, thanks for the reply black88gta

Average cracks and bumps? On a freeway you'll be fine driving at freeway speeds. It's not as though the rims are that fragile. Your profile says you're in CA so how bad can the roads be? I wouldn't be overly concerned about your wheels. Just avoid any large potholes in the surface streets and you should be fine.

Sounds like the car has been lowered and/or suspension changed to firmer if you're bouncing around that much. A stock 200SX shouldn't ride that rough. You might want to invest in some better shocks and investigate whether the springs might have been cut (the cheap and unsafe way to lower a car).

 

[Black88GTA]

Originally posted by: JulesMaximus

Sounds like the car has been lowered and/or suspension changed to firmer if you're bouncing around that much. A stock 200SX shouldn't ride that rough. You might want to invest in some better shocks and investigate whether the springs might have been cut (the cheap and unsafe way to lower a car).

I don't think that's necessarily true...it's all a matter of perception. If OP is coming out of, say, a Camry, then the 200SX will feel very rough by comparison on stock suspension, especially with low profile tires on it.

Although, OP says the car was converted to a 5-speed and the rims were upgraded by the previous owner - so it is very likely that he modded other things as well, including the suspension. A firmer set of aftermarket springs / shocks will decrease body roll in corners, improving the car's handling at the expense of having a firmer / bumpier ride.

If, however, you determine that the springs have been cut - replace those as soon as you can. As JulesMaximus said, this is unsafe, and, it can lead to excessive tire wear, alignment, and handling problems due to the wheel camber being way off as a result of the shorter springs.

 

[NutBucket]

Originally posted by: herm0016
the rear end gears are probably not tall enough ( high enough ratio) to work well with the manual. put stock tires and wheels back on it, it will ride better and will not wear out the suspension as fast.

Except that this is a FWD car so the when the trans was swapped so was the final drive The numbers you're quoting sound about right for a small 4 banger.

 

[Kremerica]

Originally posted by: herm0016
the rear end gears are probably not tall enough ( high enough ratio) to work well with the manual. put stock tires and wheels back on it, it will ride better and will not wear out the suspension as fast.

I just wanted to add/clarify that herm0016 says the gears aren't high enough ratio, this is actually NUMERICALLY lower ratio.

So when your talking about rear gear ratios (not transmission gear ratios) and you compare a Ford 2.73 gear ratio vs. a Ford 4.10 gear ratio. The 4.10 is going to give you higher RPM at any speed than the 2.73 will at the same speed.

So the ratio on your car sounds like it has been increased NUMERICALLY which in turn increases the RPMs.

again, just clarifying the numerical distinction on gear ratios.


Also, on the tires, I wouldn't even worry about it. The comments above apply to all tires, if you hit a pothole hard with any tire if COULD pop. Today the low pro tires are just as rugged as the full size sidewall tires. You will get a slightly rougher ride from low pros vs. full size sidewall tires, but this has more to do with your suspension.

One thing to keep in mind with vehicles is that almost all parts are related, you can't isolate one system from another. Any change you make to the tires will affect more than just the tires, ex. braking performance, acceleration, weight, gas mileage. everything is related.

 

[mwmorph]

Don't worry about anything. Sporty, light cars with close gearing will hit higher rpms on the freeway. 5 speed MR2 Spyders stock did about 3800 at freeway speeds. You'll be fine.

Tires wise, your speedometer reading will be 0.1% too slow, you'll be fine. 40 profiles aren't that low, 17s aren't that big. Rid will be rougher than normal but it'll take everyday hazards just as well. The only difference between aluminum and steelies are that if a Steel rim bends, you can easily repair it by hammering it back at a shop, allow rims require skilled work to repair them.

 

[LS21]

thats exactly the right operating speed on it for that car (motor and tranny). any lower, and there would not be adequate power to accelerate on the freeway

 

[ElFenix]

Originally posted by: herm0016
the rear end gears are probably not tall enough ( high enough ratio) to work well with the manual. put stock tires and wheels back on it, it will ride better and will not wear out the suspension as fast.

what rear end gears?

 

[Eli]

Originally posted by: LS21
thats exactly the right operating speed on it for that car (motor and tranny). any lower, and there would not be adequate power to accelerate on the freeway

Thats what the different gears are for. Not all cars are like that. Just depends on what the engineers had in mind.

My Insight cruises along at 2,000RPM at 60MPH, and its about as powerless as it gets. If I want to accelerate from 60mph, I drop it down to 3rd.

 

[mwmorph]

Originally posted by: Eli

Originally posted by: LS21
thats exactly the right operating speed on it for that car (motor and tranny). any lower, and there would not be adequate power to accelerate on the freeway

Thats what the different gears are for. Not all cars are like that. Just depends on what the engineers had in mind.

My Insight cruises along at 2,000RPM at 60MPH, and its about as powerless as it gets. If I want to accelerate from 60mph, I drop it down to 3rd.

SE-Rs are sporty compacts, the insight... not so much.

 

[Eli]

Originally posted by: mwmorph

Originally posted by: Eli

Originally posted by: LS21
thats exactly the right operating speed on it for that car (motor and tranny). any lower, and there would not be adequate power to accelerate on the freeway

Thats what the different gears are for. Not all cars are like that. Just depends on what the engineers had in mind.

My Insight cruises along at 2,000RPM at 60MPH, and its about as powerless as it gets. If I want to accelerate from 60mph, I drop it down to 3rd.

SE-Rs are sporty compacts, the insight... not so much.

Which was exactly my point. Its geared like that because it makes the car more fun to drive, not because "it wouldn't have enough power to accelerate on the freeway".

 

[Eli]

So was his math regarding tire diameter correct? That is all that matters, but I thought 17s would throw his speedometer off quite a bit.

So the 17" rims + low profile tires are actually the same diameter as 15" rims with regular tires? Interesting.

 

[alimoalem]

JulesMaximus: the roads are fine, for the most part, but i go to berkeley, hayward and oakland somewhat often and not to the good areas, so freeway and city roads aren't maintained nearly as well as they should be (taxes). the road down to santa cruz isn't great in all parts either . i'll check on the springs issue, thanks for telling me about it.

Originally posted by: mwmorph

Originally posted by: Eli

Originally posted by: LS21
thats exactly the right operating speed on it for that car (motor and tranny). any lower, and there would not be adequate power to accelerate on the freeway

Thats what the different gears are for. Not all cars are like that. Just depends on what the engineers had in mind.

My Insight cruises along at 2,000RPM at 60MPH, and its about as powerless as it gets. If I want to accelerate from 60mph, I drop it down to 3rd.

SE-Rs are sporty compacts, the insight... not so much.

see, i was thinking what Eli was thinking (lower gears used for more power; higher, especially 5th, used for cruising) that's why i was concerned, but LS21 and mwmorph make sense so thanks for that (thanks for the mr2 comparison...comparisons always add comfort ).

thanks so much for all the help AT. a newb gives his thanks.


just ONE last thing...i was going to call nissan but they're closed today . do i have to inflate the tires to a different pressure? for the stock tires they were supposed to be either 33 or 30psi in the front and 30 or 33 psi in the back (forgot which needed more pressure). should i do the same?

Question for Eli: i just remembered...you were the one testing out different motor oils and getting back to AT with the results, right? do you have a link to the spreadsheet you have?

 

[Eli]

Yes, that was me...

My Focus is no-more, though. I only got to do two oil analysis using two oils.

I guess I could update the thread with the results, but they aren't really very telling.

The results were that after ~9500 miles, the Pennzoil Platinum 5W-20 was still good to go.

The Mobil1 Extended Performance 5W-20 needed to be changed after ~14600 miles, probably at like 12.5k. Iron wear levels were elevated.

I had switched back to the Pennzoil Platinum 5W-20, to see if I could get more than 12.5k out of it, but the car was totaled a couple of weeks later.

 

[alimoalem]

o that sucks...well thanks for trying. did you notice any gas mileage gains?

 

[LS21]

Originally posted by: Eli

Thats what the different gears are for. Not all cars are like that. Just depends on what the engineers had in mind.

My Insight cruises along at 2,000RPM at 60MPH, and its about as powerless as it gets. If I want to accelerate from 60mph, I drop it down to 3rd.

And what the engineers had in mind is the relative mind-comfort of the driver from NOT having to downshift to make a simple pass.

Insight is heavily more mileage-efficient-minded than a "normal" car.

For "normal" cars, there should be adequate power "on tap" in a cruising gear

 

[LS21]

Originally posted by: alimoalem
just ONE last thing...i was going to call nissan but they're closed today . do i have to inflate the tires to a different pressure? for the stock tires they were supposed to be either 33 or 30psi in the front and 30 or 33 psi in the back (forgot which needed more pressure). should i do the same?

unless youre racing, a few psi here or there wont make much of a difference. if i remember right, the recommended pressures (per door jamb) is 29 front 32 rear for the 1994 sentra se-r

(by all means the same car as 1996 200sx se-r)

the only thing to remember is that these are COLD measurements. just keep them at around ~30 and youre okay

 

[Eli]

Originally posted by: LS21

Originally posted by: alimoalem
just ONE last thing...i was going to call nissan but they're closed today . do i have to inflate the tires to a different pressure? for the stock tires they were supposed to be either 33 or 30psi in the front and 30 or 33 psi in the back (forgot which needed more pressure). should i do the same?

unless youre racing, a few psi here or there wont make much of a difference. if i remember right, the recommended pressures (per door jamb) is 29 front 32 rear for the 1994 sentra se-r

(by all means the same car as 1996 200sx se-r)

the only thing to remember is that these are COLD measurements. just keep them at around ~30 and youre okay

Actually, tire PSI is a huge factor in overall MPG.

For example, when I got the Insight.. I was only getting ~54mpg.

When I checked the tires, they were only at 30PSI. Pumping them up to 40 resulted in an increase of ~10mpg. :shocked:

Granted, the stock pressure is supposed to be 38/35 F/R, so its not really comparable... but yeah.

Running ~35PSI certainly wouldn't hurt anything, except maybe your ass.