Here is a great gearing calculator. It shows what MPH it will run at what RPM running what rear end gear and what tire size. Everything that should be considered:
5th gear on a S197 is .68. You will need that for the Trans gear ratio field.
Keep in mind you can't calculate a tires height by doing the "math" based on tires size. You can kinda compare one aspect ratio to another if checking the same tire, same brand. So if you were looking at a BFG Comp TA KD in 255/45-17 and wanted to know how much shorter a 255/40-17 is in the same tire is you can use this math:
255 x .45 x 2 / 25.4 + 17
In this case the 45 is an inch taller than the 45.
If messing with different tires and brands it's best to measure though. To do it right you need to measure your tire on the rim, aired up to the correct pres. and sitting on the ground.
By going with different rubber its not out of the realm of possibility to end up with a tire that is a inch and a half different than the OEM baloon tires. That size change would change your cruising speed (with 4.10's) 145rpm's.
The tire size has a lot to do with how the “gear” will act too. If you are running a 3.90 and swap the rubber out for something 1.5” shorter the net gearing will be almost identical to having a 4.10. Obviously tire height has a big impact on how the car feels. One guy may like his 3.90’s and another his 4.10’s but if they have different height tires they could have the same net gearing. So blindly saying to yourself “A lot of people like 4.10’s so that’s what I am going to get” may not get you the results that the people you took the advice from got. You may end up with a net gearing more like a 4.30, or a 3.90 so it’s worth checking.
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4.10s here and I love them. I also do a lot of highyway driving. I live about 35 miles away from work and about 85-90% of those miles are hwy. If your worried about gas mileage, don't.
4.10s here and I love them. I also do a lot of highyway driving. I live about 35 miles away from work and about 85-90% of those miles are hwy. If your worried about gas mileage, don't.
An answer like this exactly represents my post above and the fact that when someone says "I like X.XX" the net and therefore final gearing could be working like a 3.90-4.30. It is not even half an answer. Picking a gear without tire size consideration and target cruising RPM's is dumb considering how easy it is.
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An answer like this exactly represents my post above and the fact that when someone says "I like X.XX" the net and therefore final gearing could be working like a 3.90-4.30. It is not even half an answer. Picking a gear without tire size consideration and target cruising RPM's is dumb considering how easy it is.
When I return from deployment, I will be getting new rims and tires. Prior to deployment, my car 4.10s were working like 4.25-4.30 because by tires were only 25.7". If I get 295/45/18, I know the gearing would work like a 3.90 or so and if I go 285/40/18, it would work close to a 4.10.
When I return from deployment, I will be getting new rims and tires. Prior to deployment, my car 4.10s were working like 4.25-4.30 because by tires were only 25.7". If I get 295/45/18, I know the gearing would work like a 3.90 or so and if I go 285/40/18, it would work close to a 4.10.
Those 295/45's calculate out to be 28.4" tall (that's TALL)
The 285/40's calculate out to 27"
I thought the OEM Pirelli's were 26" tall. Can someone measure theirs????
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Those 295/45's calculate out to be 28.4" tall (that's TALL)
The 285/40's calculate out to 27"
I thought the OEM Pirelli's were 26" tall. Can someone measure theirs????
If measured, they will probably come out to around 26" but according to different manufactors the 235/55/17 is I believe 27.18". My BFG are supposed to be 25.7" but I measured them around 24.5".
I had FFRP 4:10's sitting around for about 2 years before I just got them installed.
I was running 13.7's to 13.9's depending on temperature at the 1/4 mile track.
I was previously dyno tuned with C&L intake and 91 octane tune with A/F at about 12.5.
Once these gears were installed I noticed a impressive difference right away.
I used the diablosport predator and it does not let you select the gear ratio of 4:10 to correct the speedometer. Instead you have to select 4:09.
Took it to the track and ran the exact same numbers at 100mph again....WTF?
It feels quicker and my gas mileage avg is aroun 14.
what is wrong?
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05 GT Redfire Metallic,IUP,Red Leather Accent Package,16lb aluminum rims ,Alarm with Remote Start,Eibach Progressive springs 1.3 front 1.7 rear,C & L intake, Diabalosport predator tune 91 octane A/F 12.5, SLP loudmouths,Modded run 13.88 @ 101.3mph
Max Power = 258.69
Max Torque = 262.86
4:10's installed now but now new numbers.
I had FFRP 4:10's sitting around for about 2 years before I just got them installed.
I was running 13.7's to 13.9's depending on temperature at the 1/4 mile track.
I was previously dyno tuned with C&L intake and 91 octane tune with A/F at about 12.5.
Once these gears were installed I noticed a impressive difference right away.
I used the diablosport predator and it does not let you select the gear ratio of 4:10 to correct the speedometer. Instead you have to select 4:09.
Took it to the track and ran the exact same numbers at 100mph again....WTF?
It feels quicker and my gas mileage avg is aroun 14.
what is wrong?
The short answer: probably nothing.
Gearing doesn’t give you HP. It is a way of managing HP. There are an infinite number of variables at play when going down the ¼ that can effect times .2-.5 seconds so I wouldn’t even know where to start with what you are running into. One thing to keep in mind is that the gear change is not going to get you a .5 sec lower ET (in 99.9% of cases) all else being equal. Your gear may have netted you 2 10ths and something else may have taken 2 away. Net zero. You may have been geared better to run the ¼ previously and now it’s not as efficient as it was. Changing gears effects everything about going down the ¼. Your launch, your traction, your gear changes and possibly how many you need to do, etc, etc, etc.
And if your ET did go down because of shorter gearing your MPH will most likely go down too.
I run 3:55’s and never considered what would be best for a good ¼ mile ET because I don’t care about the dragstrip. The only reason my car has gone down the ¼ is that the track is 8 miles from my house. The way my car is geared I have two choices. I can hit the rev limiter just before the traps and loose time or I can make the gear change to 4th right before the traps once again loosing myself time. Going up or down in gear just one “size” could drop as much as a ½ sec off my ET (this is the .1% situation where gearing makes a big difference) because it would allow me to go through in 3rd gear going one direction or be in 4th a lot longer gearing it in the other. If you were having this same issue I’m sure you would have brought it up though.
Gearing your car is not “free time”. It’s about having the right setup for the situation. If all you care about is a good ET get the calculators out and figure out all of your factors then gear the car accordingly. Anything short of that and you will always have compromises. But if you do that you will have compromises driving it on the street. The “ideal” gearing for your car (100mph-ish trap speed) in the ¼ is about a 4.56. That would get you through the traps at 6000rpm’s in 4th gear. It would be fantastic for getting down the ¼, but would be a nightmare out on the street. And even if you went that dramatic with the gearing you would still probably not pick up a ½ sec in ET.
There is a reason that a lot of drag cars run 9” rear ends. You can swap center sections, and therefore gearing fast. Most “serious” drag cars will have alternate gearing in the trailer to deal with changing conditions. That is a clear indication that no “one” gear will ever always be ideal.
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id get 4.10s...but works 12.5 miles one way.....all highway...bummer
Meh, work for me is 30 miles away, all highway. 4.10's work OK for that.
That said I'm guessing when I finally get it to back to the track, I wouldn't be surprised if the 4.10 equation works out as 'less traction + extra 3-4 shift = slower 1/4 than with 3.31'
But that's ok...much more fun toolin' around w/ the 4.10's
I picked the 4.10's FRPP from AM, received them yesterday and installing them with a friend tomorrow. I bought the master bearing kit also and when i received it, i noticed it was made by motive or atleast the box says Motive Gear Bearing Kit. Are these kits good/reliable? I also bought 3 quarts of Royal Purple SAE 75W-90 Gear oil.
thanks
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Upgrades => Steeda UDP's /\ C & L Racer CAI /\ Comp Cams XFI SPR Stage 2 /\ Hurst shifter /\ Kooks LTH with catted X-pipe /\ Pypes Mid-muffler exhaust /\ FRPP 4.10 gears /\ Seq. tailights /\ 13" shorty ant /\ CMDP's /\ Ford 1 1/2 lowering springs /\ GT500 chin spoiler /\ Steeda GT Strut Tower Brace /\93 Octane tune from Brenspeed
not sure whats wrong 
