1990 lumina wheels

[dustyking65]

I was just wondering if anybody knows if i can go from the 14 in wheels that i have to the stock 16 in wheels without any problems. i want to do this so that i can put the cluster with gauges in it. and the speedometer will be off if the tire size is different. Any help??

[rick_x12]

I have a 93 Lumina sedan which had 14" wheels, I put on 16" from a Lumina Euro with no problems. The speedometer is still accurate. It
is the original boring sedan instrument panel, no tach, gauges, etc..
Hope that helps..

[Jonn]

Originally Posted by dustyking65

I was just wondering if anybody knows if i can go from the 14 in wheels that i have to the stock 16 in wheels without any problems. i want to do this so that i can put the cluster with gauges in it. and the speedometer will be off if the tire size is different. Any help??

Yeah, Lum wheels will fit about any GM that has that bolt circle, but not the other way around, and swapping lum to lum shouldnt be any problem at all, as for speedo, im sure if there is any diff. you can compensate.
Or else buy very low profile tires that have same ride height as original 14 inch tires.
I put a new rack and pinion in my 91, sposed to be 2 different racks, one for 14" wheels, another for larger, have no clue if any differece will be felt in steering tho. I "heard" one rack has a little less turning circle amount from lock to lock. I dunno. Another place says the one for larger wheels is "sport" steering, a bit heavier feel. But im sure either one is ok and you wont have any problem.

[dustyking65]

just wondering how if you put larger wheels on the speedometer would still be accurate. i put 205/70R14s on istead of 195/70R14s and ran it on the dyno. the tires arent that much bigger but there was still a 3 mph difference when the dyno said 35 the speedo said 32 (as did the scan tool). i was thinking that if i put the 16 in wheels on with the factory 16 in tires and got the instrument cluster from a car with 16 in wheels on them that the speedometer would still be accurate. am i thinking correctly. also if i put that cluster on will the gauges work or will i need to get the sending units from this "parts car" and put them in instead of the switches that are used to turn the lights on?

[Jonn]

Originally Posted by dustyking65

just wondering how if you put larger wheels on the speedometer would still be accurate. i put 205/70R14s on istead of 195/70R14s and ran it on the dyno. the tires arent that much bigger but there was still a 3 mph difference when the dyno said 35 the speedo said 32 (as did the scan tool). i was thinking that if i put the 16 in wheels on with the factory 16 in tires and got the instrument cluster from a car with 16 in wheels on them that the speedometer would still be accurate. am i thinking correctly. also if i put that cluster on will the gauges work or will i need to get the sending units from this "parts car" and put them in instead of the switches that are used to turn the lights on?

I think all guage sensors will have to be changed as well, as well as the connectors on them if they are different, i dont know for sure. Remember this car also has a VSS vehicle speed sensor. It feeds info to the speedometer and TCC.. I went from 195x75x14's to 205x70x14's and it made little difference in TCC or the speedo. But unless you stay very close to the stock 14" tire diameter, you will change the speedo reading, and who knows about the TCC..
My speedo isnt critical to me, hardly ever drive by it anyway.
Go to the tirerack.com and look up type of tire you have, and want, then look at the SPECS, they show the tire height, rpm's per mile, etc, then you can compare sizes. Id try to stay within a inch of original height

[dustyking65]

I was looking at the factory manual that i have for my car and i saw that in both the gauges and base cluster the VSS sends a 4000 pulse per mile signal to it. i am thinking that this is the mile per hour of the half shafts coming from the transmission. the cluster (which is matched to the tires) then converts it to actual vehicle speed. so as long as i keep the tires matched with the cluster i should be fine right? if this makes any sense let me know if i am thinking right or not. just so that you know i tried the cluster before and kept the same tires and it showed faster than i was going. so old tires and new cluster made a higher reading. new tires and old cluster made it show a lower reading. so new tires and new cluster would make an accurate reading. Just throwing out my thoughts. Let me know what you think

[cadgear]

These clusters will always be inaccurate ±3 MPH anyways, as they are not direct-link. The air gap between the coils makes for some inaccuracy. The only way to know how fast you're going is either via cop or scan tool, as one takes an outside reading and the other is direct from the VSS. Clusters that are digital like Caddy and Olds are not affected by the air gap, as they take the VSS reading direct.

As far as tire size inaccuracy, yes, there will be some. The VSS is mounted on the output shaft and by physics a larger size tire will travel a greater distance in the same amount of time. I.e., say the VSS sees 60mph. If you had the stock (or calibrated) tire size, then the car would move at close to 60mph. However, if you put a larger tire on, more area must be covered to keep the output shaft rotating at 60mph, therefore the vehicle will move faster than 60. Take it the other direction, if the tire size is smaller, less ground needs to be covered for the VSS to read 60mph, causing a higher-than-actual speed reading.

[dustyking65]

ok i understand all of that. if i put bigger tires on the speedo will be off a little. if i put the different cluster in will it make it closer to right?

[cadgear]

No, because the clusters (base and gages) run off the same VSS signal, and display using the same coil design. Unless you got a digital cluster (not offered on early Lumina models) you'll still have the air inaccuracy, which is not the same as the tire size inaccuracy. As far as what actually determines what size tires should go on the car (VSS or PCM calibration) I'm not sure.