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Wheel Cover fit over BFG A/T 275/65R17

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  • #16
    I've read all that. I think the biggest factor not included is how it is driven. Axle tramp can be an issue on standard tyres and is more a function of the way it is driven and pressure and road surface than width. And we are talking about going from a 265 to a 275 or 285 tyre. And height from a 31" tyre to a 33" tyre. And mostly going +10mm in width while keeping the same profile to gain another 15mm in diameter.

    Don't dispute what you saw but I don't see the evidence. Maybe in the bad old days when people were running silly wide BFG Comp T/As and thinking these were decent tyres.

    Too many variables expecially tyre tread depth and pattern and fitness for purpose.
    My 150 build - http://www.pradopoint.com/showthread.php?27423-A-Random-approach-to-a-Bluestorm-150-GXL-D4D-automatic

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    • #17
      Originally posted by Kitbags View Post
      Their investigations found that the failures were linked to the fitting of very wide tyres.
      How very wide are we talking about here? What are the 2 tyre sizes?
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      • #18
        Sorry duplicated post.
        Last edited by Kitbags; 27-05-2013, 09:04 PM. Reason: Duplicated Post
        2007 120 GX, automatic, diesel, 2in lift Bilsteins King springs, rear swaybar extended link pins, ARB lockers, TJM bull bar and bash plate, dual AGM batteries, Provent 200, Donaldson prefilter, Uniden UHF radio, IPF driving lights, Koita fog lights, roofrack

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        • #19
          No you have not read my post. I said all things are equal not how it is driven, tyre tread differences, and any other variable of the thousands a disputer can think of. Same tyre same vehicle same load same throttle and anything else you want to think of is the same apart from the tyre profile.
          Lets suppose you see a vehicle powering at 2500rpm under maximum load at say 20km and traction is lost. At that instant the power is still being applied. Without traction what speed do the wheels spin to? The same as when they had traction or do they speed up? Every one I have seen the wheels spin much faster. I see the vehicle speed over the ground also slow down when traction is lost. So the original vehicle speed of 20 km is now probably less than 10 km. Meanwhile the motor instantly revs out to say 3500rpm so the wheels are spinning at the equivalent of a vehicle speed of say 30kn. If the tyre gains traction gradually the load on the driveline is taken up gradually as the wheel slows as it progressively gets grip.
          If the wheel suddenly gains traction no tyre can instantly shift the vehicle so it almost instantly loses traction and jumps away from the ground.This process is then repeated over and over.Here is a shock load on the drive line that can and unfortunately does cause drive line failure.
          You say there is no proof. Sorry you never seen tyres bouncing in loss of traction situations.
          One other point. Try and pass your fingers between the inner sidewall of the front tyre and the suspension and you will be surprised at how close this upright is to the tyre.
          Your standard width tyre is carries by a stub axle that is engineered for that width and importantly rim profile. Two thirds of the tyre is over the inner wheel bearing so it is made much bigger and stronger than the outer wheel bearing. A wider tyre on a Prado must have the extra width carried by the outer bearing.The location of the inner sidewall remains the same as it is limited by the close fit suspension at least it is on my 2007 model.As the centre line of the wide tyre is now further over this smaller bearing it is carrying a greater load than intended by the manufacturers. If at the same time your wide tyre has a greater diameter than the OEM tyre you have put a further load on the stubaxle and bearings. You now have an extremely dangerous situation where drive line failure may be the least of your potential problems.
          My posts are merely pointing out that going to wider tyres has known pitfalls. If your aftermarket wide tyres are bouncing/shuddering in some loss of traction situations they are too wide and you risk damaging your vehicle. I will leave it to others to debate something that flies in the face of our love of the wide tyre.
          2007 120 GX, automatic, diesel, 2in lift Bilsteins King springs, rear swaybar extended link pins, ARB lockers, TJM bull bar and bash plate, dual AGM batteries, Provent 200, Donaldson prefilter, Uniden UHF radio, IPF driving lights, Koita fog lights, roofrack

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          • #20
            Dude... I think u have and well truely over analysed 10mm of tyre, it is only 5mm each side....for someone less educated like myself this thread has got a bit heavy.. MJ leave the comments up to someone more educated like yourself.
            [b]Rob[/b]

            [b]2016 Toyota Hilux SR5 D4D Auto Company Cruiser... [/b].
            [url=http://www.pradopoint.com/showthread.php?23866-Hutch-s-2012-150-GXL-V6-petrol-Auto]Hutch's 2012 Build up[/url]
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            • #21
              I can solve Erwin Schrodinger's wave equations and differential equations but I am giving up on this! Except for one comment that is wrong and may mislead others. The extra width, all 10mm of it, on factory wheels doesn't change the offset or track so there is no extra load on the bearings. The tyre sits equally across the rim with 5mm outside AND 5mm inside, just as Hutch said. As for the rest please be happy with your opinion. I just won't agree with it.
              My 150 build - http://www.pradopoint.com/showthread.php?27423-A-Random-approach-to-a-Bluestorm-150-GXL-D4D-automatic

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              • #22
                Originally posted by Kitbags View Post
                The length of a footprint is determined by the tyre height.
                The length of a footprint is determined by the width, tyre pressure and load on each tyre.

                A taller tyre with a narrower width has a vastly different grip and slipping characteristic to a smaller diameter wider tread tyre.
                In this thread, we are talking about 275/65R17 which is wider and larger in diameter than a 265/65R17. How does this correlate in terms of change in grip with your above statement?

                The results were consistant. A taller tyre will start to slip in a progressive manner and will also gain traction in a progressive manner. The result is progressive loading on the driveline. The wider tyre will grip right up to the point of loss of traction then break traction instantly. It will also gain traction instantly when spinning.
                So going back to the topic of this thread, a 275/65R17 is wider AND taller than the factory tyre size. It is not just wider. How does it affect the driveline?

                Another characteristic of a wide tyre is the jumping up and down as it gains and loses and gains traction as it spins. This is felt by the driver as quick shuddering. This puts a severe shock load on the driveline. The weakest point in the vehicles differential(s) gearbox tailshaft(s) is found in a dramatic fashion. To state that drive line shock can not be caused by our tyres profile is totally incorrect.
                Different tyre compounds provide different grip levels. How would the average car owner know that if they fitted the same size tyres as the manufacturer recommended but the grip level is vastly different due to fitting a different brand (we've all read tyre tests where they compare slalom times, wet/dry braking), that the difference in grip levels will induce shock to the driveline outside of the manufacturer's design limits?

                Originally posted by Kitbags View Post
                Lets suppose you see a vehicle powering at 2500rpm under maximum load at say 20km and traction is lost. At that instant the power is still being applied. Without traction what speed do the wheels spin to? The same as when they had traction or do they speed up? Every one I have seen the wheels spin much faster.
                Is that with or without traction control, and if in an offroad situation, is that with or without lockers?

                If the tyre gains traction gradually the load on the driveline is taken up gradually as the wheel slows as it progressively gets grip.
                I'm not sure I fully understand the definition of "progressive grip". A tyre either grips or it doesn't.
                One other point. Try and pass your fingers between the inner sidewall of the front tyre and the suspension and you will be surprised at how close this upright is to the tyre.
                And this leads to....??
                A wider tyre on a Prado must have the extra width carried by the outer bearing.The location of the inner sidewall remains the same as it is limited by the close fit suspension
                Assuming using the same offset, the inner wall of a tyre will get closer to the suspension.

                As the centre line of the wide tyre is now further over this smaller bearing it is carrying a greater load than intended by the manufacturers.
                The centreline has not moved if using the same rim/offset.

                If at the same time your wide tyre has a greater diameter than the OEM tyre you have put a further load on the stubaxle and bearings.
                Where does the extra load come from?
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                • #23
                  Originally posted by mjrandom View Post
                  I am giving up on this!
                  Didn't see your post so must have taken me at least 19 minutes to reply in the above post
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                  • #24
                    I was going to do a detailed response but gave up, glad to see you did though. I think some of this could be moved to the snake oil / hiclone section! Slip angles are very complex things affected by everything we have talked about. I can stage a demo too to prove that white is black. Just come and see me any night there is a new moon.
                    My 150 build - http://www.pradopoint.com/showthread.php?27423-A-Random-approach-to-a-Bluestorm-150-GXL-D4D-automatic

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                    • #25
                      Well this escalated quickly

                      So I think we have established the 275 tyre doesn't fit under the 120 wheel cover.......

                      Thanks!
                      Black 120 Grande 2003 "MY4BEE", 4L V6 Petrol 4SP Auto, BFG All Terrain 275/65/R17, Rola Racks, ARB Deluxe Bar, AirbagMan OA6011 Airbag's, Bilstein Shocks, Front King Coils, Eclipse BEC108 reversing camera, LightForce Spotties, Ironman Awning, ARB Outback Storage Drawers, Uniden 80ch UHF, Waeco CFX-65DZ, Oztent RV3.
                      [URL="http://www.pradopoint.com/showthread.php?29118-MyPradoGrande-s-120-V6"]My Rig Build Up[/URL]

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                      • #26
                        I'll remember all this when I'm out at Barbagallos in my Cobra pulling 235+ down the hill prior to the right hander with my 295 Yokohamas smoking and sliding on those stock Jag hubs! (NOT).
                        Dave
                        Views expressed are mine alone and are not intended to compromise the integrity of my employer nor offend those who may read such views.
                        Bugger Bali, get out and see Australia before we sell it all to China.

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                        • #27
                          Originally posted by Bushbasher View Post
                          I'll remember all this when I'm out at Barbagallos in my Cobra pulling 235+ down the hill prior to the right hander with my 295 Yokohamas smoking and sliding on those stock Jag hubs! (NOT).
                          235 at Barbs on the main straight is not a bad effort in a car. I did similar speeds (240ish) on an R1 last year. Great fun

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                          • #28
                            Originally posted by Kitbags View Post
                            My post was about tyre tread width not the performance of other tyre variables So lets start with two tyres that have the same treads and construction. The only difference being tyre profile and diameter.
                            A tyre's grip is influenced by the length of the footprint in the direction of travel and the width of the footprint. The length of a footprint is determined by the tyre height. The taller the tyre the longer the foot print in the direction of travel. A taller tyre with a narrower width has a vastly different grip and slipping characteristic to a smaller diameter wider tread tyre. Although not as extreme a much wider tyre of the same diameter will display the same characteristics. Comparative tests of these two senarios loaded to tyre slipping loss of traction have been conducted.
                            I was a dealer for a company who were experienced a spate of drive line failures. These failures were examined by the manufacturers engineers. They determined they were caused by sudden shock loads not inherent weaknesses in the product. Their investigations found that the failures were linked to the fitting of very wide tyres. Both owners and dealers were replacing the standard tyres. They organised a series of demonstrations to show us the difference in traction characteristics. They were conducted with a load determining hydralic coupling on the same model vehicles so loads were exactly the same. I attended these offroad field trials. Vehicles were brought up to loss of traction then allowed to skid and gain traction again.
                            The results were consistant. A taller tyre will start to slip in a progressive manner and will also gain traction in a progressive manner. The result is progressive loading on the driveline. The wider tyre will grip right up to the point of loss of traction then break traction instantly. It will also gain traction instantly when spinning. Another characteristic of a wide tyre is the jumping up and down as it gains and loses and gains traction as it spins. This is felt by the driver as quick shuddering. This puts a severe shock load on the driveline. The weakest point in the vehicles differential(s) gearbox tailshaft(s) is found in a dramatic fashion. To state that drive line shock can not be caused by our tyres profile is totally incorrect.
                            Another traction determining factor is the pressure in the tyres. We have all seen tyres worn on the two outside edges of the tread caused by under inflation. The under inflated tyre has only the outer edges of the tread working and this results in premature wear of these outer parts of the tread. Look at the skid marks on highways. You will see some individual tyre skid marks that have only two parallel black skid marks with nothing in the center. The center of the tread has so little contact with the road that it does not even leave a skid mark. A wider tyre looks impressive but how much of that wide tread is fully working when tyres are let down? This is determined by the vehicles weight and the profile of the tread. Off road tyres have either a flat tread with heavier square shoulders or a more rounded tread and shoulder. There is nothing wrong with either. Problems arise when excessive over width tyres are fitted. Next time you watch an extreme rock crawl 4x4 event check out the jumping up and down of the extra wide tyred specialist 4x4s as they lose and gain traction. No wonder they fit huge strength driveline components. Even so they break drive line components regularly.You can actually see the above for yourself at tractor pull competitions held at machinery shows as well as on the extreme 4x4 TV shows.
                            The single most dominant factor in traction is the length of the footprint in the direction of travel. All other traction considerations are secondary. But hey wide tyres look cool, so tough,so if dats wat yu want. Free country your choice.
                            What a load of dribble.. You're talking extreme examples. The example in question is increasing tyre size from 265mm to 275mm. I'm pretty sure that's within tolerance of the driveline components..
                            120 V6 Auto. ARB Sahara bar. UHF. IPFs. Coopers A/T.

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                            • #29
                              Hey, reviving this thread to make sure I'm not missing something. Prado 120 (2008) - Just replaced my OE Dunlop AT's (265/65R17) with Bridgestone Dueler A/T D697's (265/65R17) and finding my spare wheel hard cover won't fit.

                              Granted, it's dark out and I can't really see what I'm doing...so just doing a sanity check here. Is the D697 that much thicker in the same size that I won't be able to fit the cover on, or was I just not giving it enough muscle? Don't want to break the cover! Might try again in the daylight, but appreciate anyone's input. Thanks!

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