So I picked up my first mustang a few weeks ago while looking for an affordable replacement vehicle for my van which died permanently.

I am not terribly interested in the 20 inch rims it currently has but they will do until I find suitably appealing oem's to replace them. However my car does something that is terribly annoying and I figure the rims are responsible.

In the upper end of 4th I am at about 3 grand on the tach at 65mph but to make it into 5th I have to be going 70+ which hear in California can be kind of a pain depending on the flow of traffic.

So I was curious what people who have like models to me find their rpm's at with oem rims/tire sizes.

2000 Ford mustang base- 3.8L manual transmission.

 

not one person can help me with this?

 

you really need to measure the diameter of the tire (tread to tread), the rim size doesn't tell us much because there are many different tires that will fit them. it's the overall tire size that matters. if they are (average) tires it sounds like someone put a 4.11 (or higher) gear in the car. but it doesn't make sense that if your turning 3000 at 65 why you can't change to 5'th and drop the r's a bit.

 

its got some really really low profile tires on it. Overall I dont like the rims, too much chrome, too much weight. Im certain the transmission is stock. Besides the wiring it has for dvd and sound system stuff its pretty much bone stock.

Im more curious to know what people are getting rpm wise at 65mph in 4th gear on their stock tire/rim setup.

 

Honestly 3k rpm at 65 in 4th gear doesn't sound that far off. Again, why not just shift to 5th? You'll be around 2-2.5k rpm.

Heck I'll cruise at 55 in 5th most of the time.

 

Your speedometer may be off due to the oversized rims. If the diameter of the tires are larger then the stock, then your speedometer will be off. I’d have the speedometer calibrated and then rerun your RPM vs speed tests. Good luck...

 

Thank you both of you for your responses. I believe part of the problem was the lean code I was tripping (bad drivers side manifold) I replaced that and cleared the code and it runs way way better.

I also picked up a set of oem 16's so once I can afford to replace the tires that are on it I will be putting them back to stock and if need be I will do a tasteful suspension job to make the extra wheel well space more appropriate.

That should solve the speedo issue.

The problem with cruising in 5th at that speed is that at 2k and below in 5th is was almost bogging (I think this was due to the air/fuel mixture being off) seems much better now but I havnt been on the freeway at a time where I could actually hit 5th yet.

I wonder how far off its throwing my speedo. Soon it wont matter though.

 

Here is a tire size to speed calculator:

http://www.roadkillcustoms.com/hot-r...Calculator.asp

 

tyvm

 

With typical 20's, 65 really isn't 65. However, 5th gear will work better for you soon without those massive wheels to turn over. "Bogging" might just be the lack of power in a worn out 3.8L paired with the stock 3.27 gears in the rear end.

Stock diameter is roughly 25.5" on your 2000.