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Senior Member
Joined: Feb 2000
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From: Antelope, CA
Back for more advice.
I should have stopped and got my facts together before asking for advice. I'm repeating this from my prevous post "Need some advice". I couldn't expect good advice if I didn't have my correct tire size. Hopefully I haven't confused everyone. I appreciate all the advice. Let me try this again. I bought the truck with about 28000 miles on it. It's a 1998 F150 XLT 4x4 ex-cab w/4.6 with not a scratch. I believe it had the original tires on it. I know the truck had the tow package on it which makes me believe the stock tires were 265's. Correct me if I'm wrong. When the deal was just about to finalize I told the salesperson I wanted brand new BFG tires put on the truck and he agreed. (at no additional charge thank you, I also talked him down from 26,500 to 20,890) I told him I wanted the largest tires without having to lift the truck. I have the BFG AllTerrain T/A ko tires. They are 285/75 R16. I'm almost possitive while going down the road the speedometer says I'm doing 55 but, actually I'm doing over 62. I've added a Superchip, K&N airintake kit and a exhaust. It's all the original pipes just a new high performance muffler. I'm towing a 21ft boat and the truck stuggles a little. Hopefully I haven't confused everyone by posting this stuff twice. Any more advice would be great. Gear size? Spark plugs? Other mods? Thanks again.
Member
Joined: Jun 1999
Posts: 52
Likes: 0
From: Monrovia, CA USA
rich - there are some other numbers in your tire size that are pretty important...For example if you went from 265/65 16's to 285/75 16's you increased your tire diameter from 29.56" to 32.83" which is a 3.27" increase and from what I understand a pretty big deal...I don't know how to figure out the torque lost but in your other post someone replied to me that increasing diameter 1.5" takes a 3.55 gear down to 3.40...What gearing do you have?
Your post concerned me because I just ordered the chip and was expecting some pretty decent gains but you stated that you really didn't see any...
My situation may be a bit different because I went from 265/70 17's to 285/75 16's which only increased the tire diameter 1.2" and my speedo is only off 2-2.9% between 55 and 75 mph which = 2 miles off (not a big deal to me). But in your scenario (if that is the correct tire size I used earlier) your speedo is off by 11.05% which is 6.07 miles at 55 (which makes sense because you said *the speedometer says I'm doing 55 but, actually I'm doing over 62*).
I got the tire size info from http://www.miata.net/garage/tirecalc.html (got it from the other post - thanks!)
Hope this helps and someone please correct me if I got any of my info wrong or if I am on the wrong track!!!
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'97 F150 Lariat 4x4, 4.6L V8, 3.55 LS, 285/75R16 BFG AT TA KO's, 16x8 Weld Racing Typhoon's, K&N Gen II FIPK, 4 Explorer Pro Comp ES 3000 Shocks, Superwhite Bulbs, Tinted Windows, Colonels Fiberglass Tonneau Cover painted to match, Tow Pkg, 6CD Changer
Mods to come: Superchip
http://dopealicious.tripod.com/page_3.htm
Your post concerned me because I just ordered the chip and was expecting some pretty decent gains but you stated that you really didn't see any...
My situation may be a bit different because I went from 265/70 17's to 285/75 16's which only increased the tire diameter 1.2" and my speedo is only off 2-2.9% between 55 and 75 mph which = 2 miles off (not a big deal to me). But in your scenario (if that is the correct tire size I used earlier) your speedo is off by 11.05% which is 6.07 miles at 55 (which makes sense because you said *the speedometer says I'm doing 55 but, actually I'm doing over 62*).
I got the tire size info from http://www.miata.net/garage/tirecalc.html (got it from the other post - thanks!)
Hope this helps and someone please correct me if I got any of my info wrong or if I am on the wrong track!!!
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'97 F150 Lariat 4x4, 4.6L V8, 3.55 LS, 285/75R16 BFG AT TA KO's, 16x8 Weld Racing Typhoon's, K&N Gen II FIPK, 4 Explorer Pro Comp ES 3000 Shocks, Superwhite Bulbs, Tinted Windows, Colonels Fiberglass Tonneau Cover painted to match, Tow Pkg, 6CD Changer
Mods to come: Superchip
http://dopealicious.tripod.com/page_3.htm
Former Sponsor
Joined: Mar 1998
Posts: 13,385
Likes: 4
From: Virginia
For both of you..... 
First, regardless of tire size changes, the Superchip always delivers it's power gains, as long as you use premium gas.
However, when you have a size change as big as Rich has, that is a drastic size change, and a 1.5" difference makes more of a change than from 3.55 to 3.40, *much* bigger. Yes, we've seen those calculations on several internet sires, and saome of them are quite good, but a 1.5 inch difference in this size we're talking about here does more than change a 3.55 to a 3.40. When we do these calculations for the customer, the way we do it is to first, determine how many rpms the vehicle should be turning at a given speed, and then calculate what gear ratio it's going to take to make the engine turn that number of rpms at a given speed. And this varies based on weight of the vehicle, what's it's being used for, etc. Some vehicles are perfectly fine turning only 1800 rpm at 70 mph in Overdrive, and some vehicles need to be turning at least 2200 rpm in Overdrive, etc. We have to take into consideration a number of things, and not just straight conversations. You want to get to a certain end result, and that is, acceptable performance and not lugging the motor at lower rpms than it's camshaft profiles are designed for.
I responded in great detail to all of the previous posts from Rich on this, so I'm not going to repeat all of that info, it's available in the last thread. And as I stated in that response, he's not going to feel any big difference from *any* change for as long as that engine is forced to lug well below it's power band with that big tire size change. That is the factor that is by far the largest at work in that configuration, it's not that the Superchip isn't doing anything, his truck's 4.6 engine is the same as everyone else's 4.6. What you have to remember is that the Superchip is, in round numbers, about a 10%-12% power-gainer. And adding 12% more peak horsepower, while an excellent gain for the cost, cannot begin to compensate for more than 3 inches of difference in tire size, as that is a huge change.
So let's not start getting panicky that somehow the Superchips doesn't work, there are many people here, that I'm sure both of you have read comments from, that are enjoying exactly what their Superchips are doing. You can expect to have about 10%-12% more power. You cannot expect a supercharger in a can.
Now just to give you some idea of when tire size changes start to have an impact on performance, anytime you increase or decrease effective tire height by much more than 1 inch or so, you can begin to pick up some issues. It usually takes a bit more than a 1 inch change, maybe around 1.5 or so, again, it will depend on the exact vehicle configuration and it's weight & load factors based on that. For example, on an automatic, we may need to make an adjustment for shift points. Or, we have have an out of range condition that triggers a top speed limiter to kick in, even though the normal top speed limiter has been removed. An out-of-range condition can cause another type of TS limiter to engage once again, which can only be corrected by restoring speedo accuracy. The computer takes vehicles speed from the VSS, and then also uses several other data streams to *verify* that VSS data. If these do not match, you can get an out of range condition when they are off by more than a certain percentage amount, and I can't tell you that exact figure, as it will vary in actual symptoms based on a number of factors.
For example, in this case, Rich is going to need to go probably to something like 4.10 - 4.20 gearing to compensate and get his engine back up into it's power band, and nothing else is going to "fix" this current problem. Even a supercharger isn't going to be very effective until the vehicle gets rolling and engine rpm's come up, so boost can be made. I mention this point about even a supercharger, because that is how much of an impact that large a change can easily make, especially when we're talking about a 2.5 ton pickup truck.
The bottom line is that only a change in gear ratios or tires size is going to solve this. If Rich would care to give us a call, as we've offered several times, we can get him the info on the exact ratio change he needs to implement.
Our bests to all,
------------------
Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
First, regardless of tire size changes, the Superchip always delivers it's power gains, as long as you use premium gas.
However, when you have a size change as big as Rich has, that is a drastic size change, and a 1.5" difference makes more of a change than from 3.55 to 3.40, *much* bigger. Yes, we've seen those calculations on several internet sires, and saome of them are quite good, but a 1.5 inch difference in this size we're talking about here does more than change a 3.55 to a 3.40. When we do these calculations for the customer, the way we do it is to first, determine how many rpms the vehicle should be turning at a given speed, and then calculate what gear ratio it's going to take to make the engine turn that number of rpms at a given speed. And this varies based on weight of the vehicle, what's it's being used for, etc. Some vehicles are perfectly fine turning only 1800 rpm at 70 mph in Overdrive, and some vehicles need to be turning at least 2200 rpm in Overdrive, etc. We have to take into consideration a number of things, and not just straight conversations. You want to get to a certain end result, and that is, acceptable performance and not lugging the motor at lower rpms than it's camshaft profiles are designed for.
I responded in great detail to all of the previous posts from Rich on this, so I'm not going to repeat all of that info, it's available in the last thread. And as I stated in that response, he's not going to feel any big difference from *any* change for as long as that engine is forced to lug well below it's power band with that big tire size change. That is the factor that is by far the largest at work in that configuration, it's not that the Superchip isn't doing anything, his truck's 4.6 engine is the same as everyone else's 4.6. What you have to remember is that the Superchip is, in round numbers, about a 10%-12% power-gainer. And adding 12% more peak horsepower, while an excellent gain for the cost, cannot begin to compensate for more than 3 inches of difference in tire size, as that is a huge change.
So let's not start getting panicky that somehow the Superchips doesn't work, there are many people here, that I'm sure both of you have read comments from, that are enjoying exactly what their Superchips are doing. You can expect to have about 10%-12% more power. You cannot expect a supercharger in a can.
Now just to give you some idea of when tire size changes start to have an impact on performance, anytime you increase or decrease effective tire height by much more than 1 inch or so, you can begin to pick up some issues. It usually takes a bit more than a 1 inch change, maybe around 1.5 or so, again, it will depend on the exact vehicle configuration and it's weight & load factors based on that. For example, on an automatic, we may need to make an adjustment for shift points. Or, we have have an out of range condition that triggers a top speed limiter to kick in, even though the normal top speed limiter has been removed. An out-of-range condition can cause another type of TS limiter to engage once again, which can only be corrected by restoring speedo accuracy. The computer takes vehicles speed from the VSS, and then also uses several other data streams to *verify* that VSS data. If these do not match, you can get an out of range condition when they are off by more than a certain percentage amount, and I can't tell you that exact figure, as it will vary in actual symptoms based on a number of factors.
For example, in this case, Rich is going to need to go probably to something like 4.10 - 4.20 gearing to compensate and get his engine back up into it's power band, and nothing else is going to "fix" this current problem. Even a supercharger isn't going to be very effective until the vehicle gets rolling and engine rpm's come up, so boost can be made. I mention this point about even a supercharger, because that is how much of an impact that large a change can easily make, especially when we're talking about a 2.5 ton pickup truck.
The bottom line is that only a change in gear ratios or tires size is going to solve this. If Rich would care to give us a call, as we've offered several times, we can get him the info on the exact ratio change he needs to implement.
Our bests to all,
------------------
Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
Senior Member
Joined: Mar 1999
Posts: 1,246
Likes: 0
From: Wilmington, NC
Rich: you might want to think about removing those oversize tires for something a bit less radical. Might not "look" as good but your engine would sure appriciate them in the long run.(this is only meant as an opinion)
Senior Member
Joined: Mar 2000
Posts: 411
Likes: 0
From: Pa
Yea,rich
Get the right tires on the truck. You & your truck will be happy. Much less $$ than a gear change. I've been running stock size for 20 years.
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97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-Poweraid-3"
pvc air box mod-Granetelli MAF
Get the right tires on the truck. You & your truck will be happy. Much less $$ than a gear change. I've been running stock size for 20 years.
------------------
97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-Poweraid-3"
pvc air box mod-Granetelli MAF
Former Sponsor
Joined: Mar 1998
Posts: 13,385
Likes: 4
From: Virginia
HI Rich,
I got your email and responded, thanks!
Just to give you an idea, since yours is a 4WD vehicle, meaning you have to do both front and rear differentials, the cost can be anywhere from about as cheap as $800 if you get a great deal and help out on labor, or it can cost as much as $1800 to have both gear ratios changed as needs to be done to allow you to use those tires without killing the truck's performance. Realistically, figure somewhere around $1000-$1200 to have both done.
Your point about the cost of tires is well taken, as new tires are not exactly cheap, either, but the stock tires don't cost half as much as the numbers you quoted, I'm guessing those numbers were for the huge tires you have on there now, which of course you would not replace them with if you decide to change tire size instead of gear ratios to fix this problem. New tires in any of the stock sizes on the F-150 are well under $100, unless you go with true truck tires and not a highway design like all the factory tires are. So that gets your cost to about half of that $800, making them mnuch less expensize than changing gears.
Now, the decision you have to make is, is it worth it to you to get your performance back and still be able to use those huge tires? If it's worth the cost of changing gears front & rear, then you know the solution. If it's not, then going back to the standard size tires for that truck won't be very expensive.
If you really like the look you have now, then go for it, do the gear changes, and get your truck running like it's supposed to.
Either way, it's a fairly simple fix, one fairly cheap, the other kinda expensive.
Tough choice sometimes, I know.
------------------
Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
I got your email and responded, thanks!
Just to give you an idea, since yours is a 4WD vehicle, meaning you have to do both front and rear differentials, the cost can be anywhere from about as cheap as $800 if you get a great deal and help out on labor, or it can cost as much as $1800 to have both gear ratios changed as needs to be done to allow you to use those tires without killing the truck's performance. Realistically, figure somewhere around $1000-$1200 to have both done.
Your point about the cost of tires is well taken, as new tires are not exactly cheap, either, but the stock tires don't cost half as much as the numbers you quoted, I'm guessing those numbers were for the huge tires you have on there now, which of course you would not replace them with if you decide to change tire size instead of gear ratios to fix this problem. New tires in any of the stock sizes on the F-150 are well under $100, unless you go with true truck tires and not a highway design like all the factory tires are. So that gets your cost to about half of that $800, making them mnuch less expensize than changing gears.
Now, the decision you have to make is, is it worth it to you to get your performance back and still be able to use those huge tires? If it's worth the cost of changing gears front & rear, then you know the solution. If it's not, then going back to the standard size tires for that truck won't be very expensive.
If you really like the look you have now, then go for it, do the gear changes, and get your truck running like it's supposed to.
Either way, it's a fairly simple fix, one fairly cheap, the other kinda expensive.
Tough choice sometimes, I know.
------------------
Mike Troyer
Performance Products, Inc.
National Distributor of Superchips
(540) 862-9515
Email: mtroyer@compuserve.com
Performance Products F150Online Superchip ordering system: F150Online Superchip Ordering System
Thread Starter
|
Senior Member
Joined: Feb 2000
Posts: 418
Likes: 0
From: Antelope, CA
Thanks for all the posts and opinions. I will be contacting Mike Troyer with Superchips to figure out my best option. Everyone seems to think changing the tires is the best bet. Have you all priced tires lately? I believe these tires were around 185.00 each. After tax, install roadside warranty your talking about 800.00. Plus they only have about 8-10000 miles on them. Any ideas on cost for a gear change. (ballpark) Do I go to the dealer or maybe a transmission shop? Thanks again, and one thing I wanted to point out is I NEVER said I didn't think the superchip wasn't working or worth the money. Read all the threads and you'll know for yourself the Superchip is the best BANG for the buck.
