That's not bad without an overdrive. What gear is in the rear axle? I'm running 3.89:1 but never planned on highway driving. In my opinion traffic here in California is horrible. Just not suitable for a classic car.
Are your roller spring perches made by Opentracker Racing or did you find another source for them?
(11-14-2015, 01:15 PM)1969_Mach1 Wrote: That's not bad without an overdrive. What gear is in the rear axle? I'm running 3.89:1 but never planned on highway driving. In my opinion traffic here in California is horrible. Just not suitable for a classic car.
Are your roller spring perches made by Opentracker Racing or did you find another source for them?
Best Regards,
Mike
I am also running 3.89:1 gears. The taller tire really made a noticeable difference in the RPM's. The new tire diameter is 26.9" compared to 25.2" and I believe there is approximately 50-60 fewer revolutions per miles with the taller tire. As you know, there are tire calculators out there that do this math. I believe Steven has posted a good one here on the site.
If you really want to have some fun with math and determine how accurate your speedometer is you can use this formula to calculate MPH based on your tire size and gear ratio:
MPH=RPM x Tire Diameter/Gear Ratio x 336.
So here it goes with my set-up at 3,000 RPM's:
(3,000 x 26.9) = 80,7000 / (3.89 x 336) = 1,307.04
80,700/1,307.04 = 61.74 MPH (pretty accurate)
Of course GPS works too.
On another note, I ended up selling my old tires and wheels for $900 on the same day I put the new tires on. At the end of the day my out of pocket for this change ended up being $200. But look at everything that was corrected on the car, including the stance!
I did not purchase the roller perches from Opentracker which I know have a great reputation for performance suspensions parts. I believe I purchased them at Mustang Unlimited who are local here in CT. They are very convenient for me but over the years have given them way too much money!
Yeah, the correct tire and wheel setup makes a big difference. I eventually want to install either the 15x7 chrome Styled Steel wheels or I've recently seen a nice aluminum version Magnum 500 wheel in a Mustangs Plus sale flyer. These are relatively new and do a good job mimicking the Magnum 500's plus they weigh less. The wheels currently on my Mach 1 are original to the car so I definitely need to hold on to them.
I have only seen roller perches by Opentracker. I was wondering if there were any other good quality roller perches that are a little less costly. Ultimately, I'll probably end up with the Opentracker perches. Occasionally Mustangs Plus out of Sacramento CA has them on sale.
There is weight savings to be found with aluminum vs. steel rims but I did not have the opportunity to calculate the difference. However, I found this weight comparison that someone had posted online:
"I weighed a 15 x 7 GM wheel and a AR 15 x 8 cast aluminum wheel, they both had tires aprox the same size (205/75 or 215/70) and the cast wheel/tire weighed in at 39 lbs. and the steel wheel/tire weighed in at 47.5 lbs.
47.5 x 4 = 190 lbs. Steel.
39 x 4 = 156 lbs. Cast aluminum.
34 lb. weight savings"
I did see the aluminum/billet version of the Magnum wheels which I liked a lot but held off from buying them in order to keep the peace with the wife!
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