Tyre Problem on F250... a really weird one.

Submitted: Sunday, Aug 02, 2009 at 19:12
ThreadID: 125911 Views:3779 Replies:5 FollowUps:4
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This one's got me stumped.

Got a new set of wheels and tyres for the F250.
BFG AT 295/75/16 on an alloy 16x8.
Put them on look nice but the car pulls to the left, a lot!!! Need almost a 1/4 turn on the steering wheel to keep it straight.

Tyre bloke said this can happen and swap them side to side to see if this fixes it then we can do something about it.

Swapped them same result.

So then I put the old tyres back on GY Silent Armour 265/75/16 on 16x7 alloy.

Good as can be, straight no wander at all. Then I swapped them side to side. Perfect track down the highway.

So what's going on?

The BFG's are a bit taller and a bit wider but not much. So you wouldn't think that'd make the difference.

Is this doing something to the suspension or steering?
I took the RTC damper off and put it back on, no difference.
The wheels are made specifically for the F250 with correct offset.
Tyre pressures are correct and I did play with them with no change.

If anyone has any thoughts I'd be awfully keen to hear them.



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Reply By: Innkeepers - Monday, Aug 03, 2009 at 01:57

Monday, Aug 03, 2009 at 01:57
It seems to me that the wheel rims are the problem as you have used the 16x8 rims with the BFG and 16x7 wheel rims with the Good Year tyre. I would be 99% sure that the tyres are of good manufacture, so back to the rims.

I really think that the 16x8 rims are the problem...even though it is supposed to be the correct offset for the F-250.....is the offset any different to the 16x7??? That is, does the wheel extend in or out further than the 16x7 from the centre of the hub...answer should be yes if it's a wide rim....so is it an equal extension either side of the vertical plane of the hub?

If so then the rims may have been tagged and boxed incorrectly and it is NOT the correct offset for the F-250. Then try some different rims or rims from a different manufacturer.

Hope this leads you to a solution.

Cheers
Rick

If this is not the case then maybe the offset for the wider rim is not correct for the steering geometry set up for the 7'' rims.

AnswerID: 578494

Follow Up By: GoneTroppo - Monday, Aug 03, 2009 at 03:15

Monday, Aug 03, 2009 at 03:15
Thanks Rick, I hadn't really thought of the rims but of course they are part of the equasion.

I had a quick measure. 16x7 inner edge of rim to face of hub is 106mm
16x8 is 110mm. This is measured from the very edge of the wheel so thast may introduce a error factor in terms of wherethe tyre is actally seated on each one.

Not really sure if this proves or disproves the rim theory, what do you think?

Cheers
Chris
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FollowupID: 851577

Follow Up By: Innkeepers - Monday, Aug 03, 2009 at 03:59

Monday, Aug 03, 2009 at 03:59
Hi Chris,
Well you know that the 16x7 rims run true with the Good Years....so put the BFG's on the 16x7's for a short run up the road...the tyres will stand up a bit higher being a norrower rim, but if it runs true, then it's the rims....

Also, Scott maybe be on to something there too with the tyre pressures....although on any vehicle I've ever owned hard or soft the tyres never produced a quarter turn of steering wheel correction.

Cheers
Rick
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FollowupID: 851578

Follow Up By: GoneTroppo - Tuesday, Aug 04, 2009 at 01:11

Tuesday, Aug 04, 2009 at 01:11
Good point Rick, doing that tomorrow.

Re pressures I run 45 on the front although I tried from 35 to 55 just to eliminate this possibility.

Guess I'll know more this time tommorrow.
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FollowupID: 851579

Reply By: Silver and Tinks - Monday, Aug 03, 2009 at 03:47

Monday, Aug 03, 2009 at 03:47
Hi
we run 16 x 8 eagle rims and 285 x 75 x16 mud terrains on our F250 we had the castor adjusters fitted and had a wheel alignment done at a proper truck align shop.
narrellan truck align and our truck steered like an arrow all the way to Darwin and back over the last three months.

tyre pressures are also important with the big rubber we are running on the hwy 48 rear 46 front.

Scott
AnswerID: 578495

Follow Up By: Silver and Tinks - Tuesday, Aug 04, 2009 at 05:27

Tuesday, Aug 04, 2009 at 05:27
Having seen Franks comment about shocks
we have bilsteins on our F250

best wishes Scott
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FollowupID: 851580

Reply By: Andy1 - Monday, Aug 03, 2009 at 15:09

Monday, Aug 03, 2009 at 15:09
Is that "correct offset", for LHD or RHD? With the limited number of F250's in Aus it would seem most likely that the offset would be for RHD. Off to the truck alignment workshop?

Andy
AnswerID: 578496

Reply By: Frank Aus - Tuesday, Aug 04, 2009 at 03:36

Tuesday, Aug 04, 2009 at 03:36
I had the same problem, took the f250 up to Rockhampton and had a wheel alignmnet and a castor correction, whilst it was better, was still not as good as the goodyears, But then i found a front left shockie was kapaut, so changed that and install rancho,s from the states and hey presto straight down the road again, I also have front air bags and in the end i commoned the front air lines up, because if one lost a bit of pressure it would want to drift off the road. ie, if the front left went down to 20 psi and the right was 25 psi it made the truck want to wander off to the left etc. strange enough it didnt seem to matter with the 16x 7 though. but its a thought, pull your front shockies off and make sure they are ok.
AnswerID: 578497

Reply By: GoneTroppo - Wednesday, Aug 12, 2009 at 23:59

Wednesday, Aug 12, 2009 at 23:59
Problem fixed!!!

After swapping tyres every which way, side to side, back to front, 2 spares to front we pretty much eliminated the tyres as the problem.

So that leaves the wheels which are an inch wider.

Truck Wheel alignment place in Cairns fitted a different castor kit now it tracks like an arrow.

I asked the bloke about it and he felt that changing to a one inch wider wheel should not have made a difference. (He fitted the original castor kit after I fitted the OME suspension)

Thanks everyone for your suggestions/assistance I'm once again a happy Ford driver.

AnswerID: 578498

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