I recently went from the stock 235/70X16's to 305/70X16's on my 2000 SCab 4X4. Now my father-in-law tells me that oversized tires can cause drivetrain damage down the road. He says that stress from turning the larger tires in low speed/high torque situations (i.e. off roading & towing) can lead to play in the driveshafts and eventualy failure. Is this true for this size or only for the huge 35"+ tires? They fit my wheel well perfectly with no rubbing even in sharp turns. In fact, the truck handles amazingly with the new tires, I'm very pleased with them. That's why I'm concerned. There's NO WAY I'm going back to the smaller tires but I don't want to hurt my truck either. What can I do to prevent this damage?

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Stock Stuff:
Y2K SCab 4X4, Chesnut Metallic, 5.4L, 3.55 Limited Slip, Skid Plates, Factory AM/FM/CD, 40/60 Split Bench, Sliding Rear Window, Towing Package and Keyless Entry.

Extras so far:
305/70X16 GY Wrangler AT's on American Eagle Series 146 chrome wheels.

Future plans:
Spray in liner, chrome step bars, Lund hood deflector, chip?, K&N? we'll see.



[This message has been edited by onemilmhz (edited 07-27-2000).]

 

I have 275/60/r17 on mine. Stock. Lightnings come stock with 295's. Its not going to hurt a thing.

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99 F-150 Sport XLT Black x-cab 4.6L auto 3.55
K&N filter and dual series 40 flowmasters

[This message has been edited by this-end-up (edited 07-27-2000).]

 

The only thing you should consider is changing you gears; maybe to a 3.73 or 4.10?
Otherwise, your speedo is gonna be off.

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1999 F250 LD S/C XLT 4x4
5.4L, 3.73, 4R100 trans.
Flowmaster 40 series, K&N, Poweraid, Superchip, Rancho RSX shocks, Stull billet grille, 2-PIAA Pro80XT's (120W), 2-KC Daylighters (150W)
265/70 R17 BFG AT KO's on 17x8 American Racing Atlas rims
Kenwood 7000 CD, Alpine 3342 Signal Processor, Alpine MRV-F353 5Ch. Amp, Pioneer TS-A6865 3-way speakers. CompuStar alarm/autostart. Coming soon: MTX Thunderforms box

 

Relax......Despite what anyone may tell you, the F-150 is probably overdesigned. Everything breaks eventually, but the only reason you are "scolded" for going big is it slightly increases the chance of failure.....therefore the warranty gods frown on it. I recently went from 255/70/16's to 285/75/16's and couldn't be happier. And dude....spend the cash on the K&N.....the difference is like the worst tank of gas you ever had...to the best tank of gas. Way more throttle response and sweeeeeeeeeeeeeet passing. CHEERS!

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'97 F150 S/C 4x4 Lariat Black w all the factory toys 4.6 L K&N YUP! 285's next week! Can't wait to get this scanner working so I can show this beauty off *S*

 

Changing the gears also reduces drive shaft strain
I am concerned about the brakes though.
More force required to stop those bigger tires.

 

54regcab.....Definately more braking force required, but I've had a few panic stops since the bigger tires went on, and The braking seemed if anything more predictable, and the ABS seems less intrusive. I dont know if you have had this problem, but my ABS seemed to come on way too much. perhaps the better grip helps...the gy's I had on the truck were absolute GARBAGE!!!!! I'm sure I'll go through more shoes and pads, but if you want to play you have to pay...:> )

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'97 F150 S/C 4x4 Lariat Black w all the factory toys 4.6 L K&N YUP! 285's next week! Can't wait to get this scanner working so I can show this beauty off *S*

 

onemilmhz- the difference in tire HEIGHT that you described is not large enough to tear your truck apart with or without a gear change. My opinion only.

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2000 F-150 XL,RC,LB,5.4,4R70W,3.55LS,
Class III tow/Payload #3/Convenience pkgs.,
4-wheel disc/ABS,Chestnut/Parchment 40/60,
Ford bedliner & gas/wheel/spare locks,
3" cold air box modification,Superchip,
Dynomax ultra-flow welded 3" cat-back.

 

Thanks for the advise guys. I talked to my shop and they told me pretty much the same thing, not big enough to cause any damage. When my dad-in-law saw the pics I emailed him he agreed. I will need to reset my speedo though.

 

Tell your father-in-law he's right (technically).

It will make your wife ever so proud.

If you were going to have any failures due to your driving or having fun with the original setup -- it will be worse with your new tires.

On the other hand, perhaps you could have flogged your truck with only an annoyance here or there -- whereby your new set-up might result in one there or here.

You can just stand back and look at your truck and eyeball the extra leverage that your set-up puts on your suspension goodies -- and get a pretty good feel for the consequences. If it is a "damn, Homer, that's really a big change", then -- well, you guessed it. If it's merely a "Gee, Beevis, that's pretty cool", then you're in luck.

Braking requirements as a result of rolling radius of your tire are probably the most pronounced -- and MANDRAKE27 has his thumb on the issue. Brakes are sized for vehicle weight and wheel speed and (most importantly) rolling radius (leverage) of the tires.

You will most notice it from a high-speed snub -- where in a 'panic' situation, you may be surprized by fade with your new setup.

Maybe not...

Post some pix.

Enjoy...

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Y2K™ Jim Gorka

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"

 

Hey Y2K I see you have four wheel disc ABS...was this a factory option on 2000's or is it an aftermarket setup? Do you know if rear discs are available for the 97? And if so do I have to scrap the abs? Just got back from a great walleye trip....(great fish bad scratches) You don't know anyone with scratchless paint do you? LOLOOOL HAd to pull out a 95 GMC 4x4 with a 5" lift and 35" MT claws on it hehehehe Mine's pretty much a stocker. FORD......Fan of rough Driving......Cheers

 

MANDRAKE27,

4 wheel disk and ABS were standard equipment on the 99 XLT and Lariat models! The set-up works exceptionally well!

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Paul...
99 F-150 XLT SC Sport, 4.6L, Auto, Captain Chairs, Class III Towing Package, 3.55 LS, Sliding Rear Window, White, 4X2, CD, Soft Factory Tonneau Cover, K&N Filter, WMS Velocity Tube, Line-X Spray on Bed Liner, Gibson Side Swept Cat Back System, Superchips Flip Chip, and the Original F150online Decal...

What more is there!

ptarnuzzer@ikon.com

 

Since I was 16, all I ever owned were Ford 4x4 trucks. I lifted every one of them and put bigger tires. My experience doing this tells me what I can get away with and what I can't before having to re-gear. I feel 35's are the upper limit you can go too before having a serious concern about the health of your trucks components and loss of low end power. You will notice some loss of low end due to the change in final drive ratio, but it really isn't all that bad if you don't drive like a maniac on the street, doing holeshots from every light.

My opinion is that Y2K is technically right. Larger tires do put more stress on the drivetrain and suspension but not just from the overall size increase. Weight of the tire/wheel makes a big difference as well as the wider width. Thats why it is a VERY GOOD idea that you replace the stock shocks with high quality aftermarket ones to help offset this increased leverage ratio. A steering stabilizer is also highly recommended to help cushion your steering components from the increased torque they will experience from the larger tires. The effects of larger tires can be compensated for, and if you only go a little larger you don't even need to do a thing.

When my new truck finally gets here, I definitely plan on going to around a 35 inch tire. My truck will have 3.73 gears and HD larger brakes which will help offset the tire size increase. I don't really off-road anymore or tow anything heavy. I ordered the truck with the 7700# payload just to get the lower gear ratio and heavier drivetrain so larger tires won't effect it as much. That and the fact I plan on keeping this truck for at least 10 years.

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Boss™

Just Ordered 2001 F-150 Lariat, Oxford White/Silver 4x4, medium graphite leather, SC, SB, SS, 99L 5.4L, 44E tran, 7700# payload, Class III Tow, 3.73LS, Skids, Capts chairs, 4W disc ABS, shift-on-fly, keyless, HD everything
Planned Mods:
"Protected by Smith&Wesson" sticker, Westin Chromed Stainless Nerf Bars, ARE LS II bed cover, Bedrug™, Gibson Swept Side Cat Back, K&N filter w/airbox mods, headers, Superchip, 3" body lift with at least 33's, alarm/pager/auto start system, stereo system

 

1milmhz, you have gone from a 29" tire to a 33" tire. This effectively raises you gear ratio to 3.05. Since Ford puts a 3.08 rear end in some of these trucks, I would say there in NO appreciable increase in driveline stress. Regards, m.a.t.

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1999 XLT SC, bright red, 4.2l, 5 speed, MAAP stainless nerfs, Prime Designs bug deflector, Astro Euro-Lid II, Mobil 1.

 

Mandrake27 - I somehow missed your question until now. I have the 7700# truck and it has a different axle than does yours -- and/but don't the new Y2K's (non-7700) come with rear disc too? If so, should be a bolt-on -- and the ABS should be smart enough to tell a lockup regardless of the brake type. The only question that I don't have an answer for is the biasing for the rear brakes -- question for someone closer to the hardware:

Is there any difference in the master cyllinder or any ratio valving between the disc and drum-style brakes? (I'll bet no).

Boss96Hog: I'm planning on having Nick with me until I retire -- so I'd like to make him last for 10-15 years too.

I like the idea of less un-sprung weight -- which means lighter tires and wheels -- makes the truck take stutter-bumps nicer.

While having no direct measurements, my eyeball-calculator tells me that the suspension assembly of the 4x4 is lighter than that of the 4x2 because of the torque rod vs coil spring.

The front ends of these new Fords are impressive. I wish they had zerk fittings -- but it appears that they're strong; and if the ball joints do become an issue, then surely some enterprising company will offer re-furb lower control arms at a reasonable price -- so I guess I'll not worry until then.

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Y2K™ Jim

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"

 

Wheel offset I think is the big issue here.
I've seen too many front ends that have constant alignment problems from wheels that stick out.
What happens is in the stock setup the wheel bearings are in line with the center of the wheel.
When ppl put on wider wheels all the strain goes on the outer wheel bearings.
I don't think a 1" wider wheel would hurt anything as it only throws everything off 1/2" off center.
Go much wider and you are sure to have problems, unless you upgrade the stock setup.
How many ricers (an extreme case) have you seen where the rear axle seems to be bowed?
Also, I had 5.5" stock rims on my old Nissan and went up to 8" and the steering drivabilty just was awful.
I ended up getting some 6" and everything weas back to normal, fortunately no permanent damage was done.