need crx tire advice
 

I have an '87 CRX. I have 175/70/13's now. I've read older post on here talking about Insight 15" wheels and taller tires.

I've owned my car 4/5 yrs., and have been quite frustrated that I'm turning 2,200-2,300 rpms at a mere 50mph. I heard the talk about taller tires changing that down to about 1,700 or so. I would love to see that.!! I don't have the scratch for high dollar LR tires, or buying even used 15 inch wheels right now. I wish I h

ad the diff. ratio of the original '84 1.3 !!!



Right now I need at least 2 better tires to even be safe. 2 are good.

My thought was to go to goodwill, buy a bathroom scale to buy light tires. Maybe I can trade off my 2 good 175/70's to help me get a better price on 4 used .. I want taller... so do I want 155/80's, 155/85's??? I'm willing to go skinny for a better CD, but what's the best height aspect for my stock rims??


If I'm staying w a 13inch every thing, is that difference going down to my dream 1,700 at mph. still possible, or is that rpm change only possible w like a 15 inch story?????


I can only go dirt cheap right now. HELP!!!!!!!!!!!!!!!!!!


I would like to pick a size common enough to be easily found used anywhere! Thanks!!!

The Honda Insight has 14" rims and the stock insight tires will be about the right size for the CRX but they are an odd size that are hard to find, very few choices to choose from, stock insight tires of course will give you a boost in mileage by being low rolling resistance light weight tires.
155/80 R13 tires would be better, your crx is light enough that it can handle narrower tires, but for the gear ratio... I would say to do a transmission swap, $150 and a day of work and you will have a better gear ratio.
What trim level of CRX do you have?

I appreciate the help!

I hear other guys rattle off DX or HF etc... is there something on my vin# that would give me a clue as to how to answer you???

Off the top of my head I don't know the vin number decoding, but an SI is going to be a 1.6L engine with fuel injection, the DX is going to be a 1.5L with a black steel air intake, the HF is going to have a silver aluminum air intake, DX does not have a tachometer but the SI and HF do.

The Civic Hybrid has 15" wheels I believe and a pretty good aero wheel surface. You need Low Rolling Resistance tires too. The size of the tire can make a difference in addition to the wheel. You might save the cash on the new wheels and look into larger tire sizes that fit your current wheels. Save $$$. Also, the overall diameter of the tire/wheel is inversely proportional to the RPMs rate. The power wheel/tire is basically a gear. You also want to take into account increased rotational mass from a heavier tire/wheel combo. See Sentra_SE's current discussion about switching to larger tires. He is having interesting results.

The 87 CRX is the first-generation one. The Si will have a 1.5 liter engine with MPFI (Multi-Point Fuel Injection). It will also have a moonroof. The DX or Standard version (I do not believe there is a badge on it) will have a 1.5 liter engine with a carburetor on it. The HF version has an engine whose size I cannot seem to find out, and it also has a single carburetor on it.

Spinning at 2300 RPMs at 50 MPH tells me that this is most likely an Si, or at least has an Si transmission on it.

175/70-13 would have sidewalls of roughly 175mm * 0.70 / 25.4mm/inch; 4.8 inches tall. Two sidewalls contribute to the overall diameter, so that's 13 + 4.8 + 4.8 = 22.6" overall diameter.

A 155/80-13 would have sidewalls of 155 * 0.80 / 25.4; 4.9 inches tall. The overall diameter would be 13 + 4.9 + 4.9 = 22.8". That's a difference of about 1%. Not enough to justify the change IMO. (And I actually rounded the 4.8" down from 4.82...., and rounded the 4.9 up from 4.88... so the actual change would be even less.)

It's hard to find passenger car tires in any aspect over 80.

In order to bring your 2300 RPMs down to 2000 RPM, you will need to increase the overall diameter of your tires by 15% of your original 22.6", which is just about 4". So you need to get sidewalls that are almost half-again as tall as your current ones. Which IMHO is not going to happen.

Going up to 15s means you only need sidewalls that are 3" taller than your current ones. Still very unlikely. And going with bigger wheels than that will really hurt your in-town MPG, not to mention acceleration and braking distances...

And, of course, your speedometer will be reading a whole lot lower than you are actually driving, because it assumes the tires are the stock size!

The only real practical way to drop the cruising revs would be a transmission swap, or at least a gear swap. The speedometer would even read correctly (or as correctly as it does now anyway).

The folks on the Red Pepper Racing site know a whole lot about 1st-gen CRXes and the equivalent generation of Civic. You might look for more detailed info over there.

-soD

first generation of the civic hybrid had 14" wheels with the 4 bolt 100mm spacing, 2nd generation civic hybrids have 15" wheels but they use 5 bolts so they will not bolt on to older civics or CRX's.

I don't have an SI for sure!! Definitely have carb, my air cleaner cover is black, but I do have a fact tach, but no badging on the car.
I think they only badged w the 1.5 script the first couple of years.

The info that I've gotten so far is that the original early '84 1.3 CRX has a diff. ratio in the 'hood of 3.50-3.55 or so. The rest of the regular 1.5's I've heard were around 4.11 ???

I have some info that the 1.3 had a 4spd., not a 5; therefore I couldn't swap it in unless I only wanted a 4spd.

Then I wonder about garden variety Civic's all through the mid 80's that I think were 1.3's w 5 spds. That sounds perfect IF it had the mid-3's ratio.

I realize it was only that early 1.3 CRX that had the special alternator that was supposed to help achieve it's highway rating at about 67mpg.

I do have a sun/moon roof... can't tell if it's factory or not... in my climate I wish it wasn't there... it started leaking, and I sealed it shut ok, but it's still a slight CD blem even when closed!

I do have plastic front fenders instead of steel if that helps explain anything!!


It's like I have just enough knowledge about it to stay confused!!

I really appreciate the tire help. There's part of me that wants to go straight to a 155 for a better CD print, but a fraction of still wants the 70 aspect for looks, and my 1% of the time canyon racing by myself...which I would only PUSH a little in the dry only anyway!!! I'll have to sleep on this issue!!!!

Thank you everyone! Right now, I don't drive enough to justify a trans. swap!

With the 1.3L engine from 1984-87 the civic hatch back came with a 4 speed while the 1984 CRX 1.3L (only year a CRX had a 1.3L) came with a 5 speed my understanding is that the gear ratio in top gear on both of the 4 and 5 speed transmission was about the same but that you ended up with greater spacing between them, however the CRX HF has a taller gear ratio giving you slower engine RPM at highway speeds.
All CRX's from 1984-87 had plastic front fenders and that bit in front of the hood is plastic too, CRX HF's didn't have a passenger side mirror, no rear wiper but they do have a little rear fin, no sway bars, most of the time they did not have a dash clock (altho it was a dealer option) and they did have an extra lower lip on the front bumper to bring it down lower and the radiator is tiny! 15" by 15"

The DX trim level has a hand full of options, like the dash clock, passenger side mirror, sway bars, maybe rear wiper... but I don't remember and a full size radiator.

The tachometer is a bit odd to find, but it's also not hard to swap out and apparently all the wiring is there for it already if someone did put it in from another car.
If it was an SI that someone swapped engines from, then it would have a factory sun roof as well.

You might want to try 185/70R13's if you have enough room in your fender well.

I've tried to reduce your requirements to a common set.

Sumitomo T4, low rolling resistance tires, Tire Rack price does not include shipping, mounting and balancing.

175/70R13 - 1,036 lbs - 51 psi - 927 rev/mile - $52/ea
185/70R13 - 1,135 lbs - 51 psi - 907 rev/mile - $60/ea

If you go with oversized, Sumitomos, you need to read the specs on the rim width to match your wheels; the tread width; and the overall diameter. Take a string and ruler and measure where your current tires sit relative to the wheel well. Make sure there is enough clearance before buying.

If there is any question, consider buying one tire to mount on a spare wheel and then put it on the rear and test drive over some speed bumps. Then swap to the front and again test over some speed bumps. The one tire test approach is somewhat expensive because if you by a second one, more shipping cost. Worse, if the tire doesn't work out, getting credit back will entail some loss. But then you'll know for the second one.

Double check the Sumitomo T4 reviews against your likely driving. They are not listed as being good on ice and snow but that is what winter tires and chains are for.

Having two tires that won't pass inspection suggests there may be an alignment problem. Start with an analysis of the wear pattern and follow-up with a measurement and alignment. Also, find out if your car has adjustments for:

• front toe - pretty much universal
• front camber - ?? sometimes requires a camber bolt
• rear toe - ?? fixable with metal tabs or EZ-Shim
• rear camber - ?? fixable with metal tabs or EZ-shim

If you do get an alignment, get a copy of the new values and start a fresh thread about '4 wheel alignment.' This is a different problem from the tires.

There are web sites that claim the best tires should be on the rear to prevent the car from spinning out in marginal conditions. However, I found that having a pair of different sized tires, they should be tested in one configuration and then swapped, front-and-rear. Check the handling and maximum effort braking in sane conditions and choose what works for you.

GOOD LUCK!
Bob Wilson

So the 185's rev a little more than 2% less than the 175s? That should mean the difference between these two tires in terms of MPG at 5th gear highway speeds would be a little over 1% maybe? In a car like an 80's CRX that's possibly a difference of 1.5-2.0mpg at highway speeds, no? If true and the 185s fit my CRX, that's what I would buy. SentraSE-R and others, such as arcosine, seem to have found that despite the larger sizes (worse aero) and heavier weights, that the taller gearing is a net benefit (on the highway, at least).

You mean fewer revs and the correction should be relative to the stock tire, assuming it is the 175/70R13:

(907-927)/927 = -2.16%

Only if GPS speed limits are being used. Changing the tire size also impacts distance measured and indicated speed. A slower turning tire will lead to a lower indicated speed so drivers are tempted to drive a little faster and into higher, aerodynamic drag.

I'd have to see their data but I don't see anything wrong as long as the same-speeds were used.

Bob Wilson

Of course the stock size tire for the CRX HF is the 165/70 R13 and I've run 155/80R13 tires with good results, after all the car hardly weighs 2,000 pounds.

This makes it even better:

165/70R13 - 0,937 lbs - 51 psi - 949 rev/mile - $54/ea
175/70R13 - 1,036 lbs - 51 psi - 927 rev/mile - $52/ea - -2.32%
185/70R13 - 1,135 lbs - 51 psi - 907 rev/mile - $60/ea - -4.23%

If the 185/70R13 fits, there is potentially a 4% reduction in engine rpm.

Bob Wilson

So at a steady speed comparison between the current 165s and a new set of 185s, with a 4.23% reduction in RPM, you might get an improvement of 2+mpg (again, assuming a consistent highway speed comparison of the tires). To minimize possible increased aero drag you could build tire spats for front and back tires. To minimize the small weight increase you could find a little weight in the car to remove.

Oh! and if these LRR tires are replacing high RR tires, the benefit should be much greater than 2mpg.

Just remember that a larger diameter tire makes the speedometer show a lower speed than true and aerodynamic drag works on true speed. So at 50 mph true, the speedometer would show 50 * -4% = -2 mph or 50 - 2 = 48 mph. The driver would be tempted to run at an indicated 50 mph and be doing a true, 52 mph.

The only way larger diameter tires work is to use a GPS speedometer instead of the vehicle speedometer. Use sticky-tape over the speedometer to make sure the GPS reference is used.

Bob Wilson

The Odometer would be off too, no? But can't they be recalibrated by changing the gear? Or I wonder if it is even possible just to create a new speedometer dial using a computer paint program of some sort and overlay it onto the OEM, having "calibrated" it to show what you need.

What I do is use a calibration factor when I enter my miles and gallons. I know my larger tires need 106% to calculate the true distance. So I enter the corrected value in the miles but indicated miles and odometer in the comments.

In aviation, we had a magnetic compass correction card, usually just a few degrees, but over five hours at 120 mph, a few degrees is landing at the wrong airport. <grins>

Bob Wilson

I own an 84 dx1300. Can confirm it's a 5 speed transmission with tall gearing. The trans is out right now being reconditioned for re-installation.

Here's a build link
1984 crx project - GasSavers.org - Helping You Save at the Pump Hypermiling and Fuel Efficiency Forum

Many tire shops carry inventories of used tires in good condition for cheap. Check around. Your gearing is taller than the si transmission, but would be improved with a 84 dx1300 transmission if you can find one.

Some useful info:
CRX Specs & Performance

These transmissions only weigh about 70lbs, so it can be swapped in a driveway with jack stands. Keep a look out on car-part.com! If you can get the money together for really good tires, the Michelin Destiny is a good choice. The best part is that all the tires in this size are very light to begin with. There would be less benefit to a LRR 13" due to this fact. Higher rated sidewall pressures are a good specification to look for.

I drive a 87 crx si it has stock 185-14" yes I concur high rpms. I see 2500rpms@about 50mph. this has led me to the trans swap cure. have already purchased the hf trans from a 89. not got any confirmation of a direct fit yet. waiting to lay hands on a 87 hf trans before it goes into the shop for a swap. hopefully very soon. if anyone knows about the fit of the 89hf into the 87 (2nd gen into 1stgen) I'd appreceate knowing.

IIRC, the transmissions from the 2nd-gen CRX (88-91) do not swap directly into the 1st-gen (83-87) chassis. :(

-soD

The 1984-87 engines and transmissions are not interchangeable with newer years.

appreciate the reply's, sorry if i encroached on the tire discussion, any ideas if modification of trans from 2nd gen is possible like one bolt doesnt line up or spline shafts dont fit if you could detail any on the problems concerning such an idea, maybe theres a possible way around(rig, hack, etc)

I've never set them side by side but starting in 1988 Honda standardized a lot more of their drive train, the first generation crx and civic had the CVCC engine and that tilted forward a few more degrees it seemed like, when Honda went way from carburetors they made a lot of changes.

I'm hoping to lay the first gen and second gen hf 5spds side by side soon, I'll let you know what I discover

I sure appreciate everyone's input! The trans. talk is every bit as important as the tires... they seem to go together here.
I'm not nearly as high tech as some of you, but usually I can get a speedo check from road construction your speed is ....... or town/school like digital signs, and simply remember where that truth is. Worst case, there's a speedo shop in Portland that could recalibrate!

I once had a discussion w a bicycle fan who thought a wireless digital bike speedo might work on a car if said unit could handle automotive speeds. Anyone have experience or thoughts here?

Well; I've slept on only the early responses here; so my mind is still mixed. 155 (low CD) vs. 185 for highway mpg I love to take long trips at 50mph or slightly less, and in every day life, I'm still mostly 75-80% highway or at least min. stoplights by careful choice! SO now I need to sleep on that a little more!! (lol) It was nice to get confirmation about a 185 fitting an '87

Final thought for now.... Have many of you read up on how special the '84 1.3 CRX alternator was supposed to be in its part in contributing to the 67mpg highway figure? I'm not trying to be lazy by not checking it out myself.. but one wonders about availability of such part NOW, after all these yrs., and what the price difference is compared to a JOE NORMAL alternator for the 84-87 range.... if other than '84 stock wiring could accept it.... if regular Civics, and 2nd Gen. CRX's could benefit from it enough to talk about???

All of the 2nd-gen CRXes, as far as I know, will "turn off" the alternator after the car has been driving a while. It is in the factory manuals, and I can see the system voltage drop to ~12.6 after a drive.

It is related to temperature (probably coolant temp) and the electrical load on the system as measured by the ELD (electrical load device or something like that), and probably to other things. If I turn my lights on, or the rear defroster, or even turn the cooling fan on speed 2 (with 1 the slowest and 4 the fastest) the voltage will go back up to 14-ish.

-soD

Pretty sure there is nothing special about the 84 alt. I've got one in my garage as a back up. It has the same connectors as 85-87 and seems to have the same size pulley.

1720 lbs, tall transmission, and 1.3 liters of fury are the highest contributing factors.