twodoorgaz Posted December 8, 2011 Share Posted December 8, 2011 Quick question here folks: Thought that LR4x4 would be a better place to post this querey given that it'll require a bit of scientific understanding rather than risking simply getting shouted-down on other forums. I'm having some rims set up by a specialist wheel manufacturer (almost certainly Matt Lee) for a custom/trick Landy project and need some feedback on my interpretation of some forces acting on the wheel bearings. The rims I'm having made are shown in the diagram attached, labelled as - "custom offset 5.5" LWB". For clarity I have shown the standard LWB rim and the Land Rover steel rim with the largest factory offset - the rarer FC wheel. Effectively these rims will be LWB with a bigger offset (the wheel disc will be welded to the rim outer in exactly the same position used on the FC wheel). We know that increased offset, either through extra offset wheels or through the use of wheel spacers increases the load/stress on wheel bearings... But, am I right in thinking that when I get my custom rims back and shod them with 750R16 tyres that the load/stresses I place on the wheel bearings will be greater than if I used a standard LWB steel rim but, at least to some extent, less than if I were to use a FC wheel with 750R16, 9.00x16 or 23585R16 tyres? I'm trying to reassure myself that the strain on the wheel bearing is within Land Rover tolerances for a Rover hub. I like to find a precedent before making a modification rather than simply relying on reports of "I've ran it like that for years and its been fine". As an added bonus it would appear that with the custom offset the face of the hub will be aligned with the centreline of the wheelrim (if that makes sense!), not sure if that is good for the axle but from a dynamic point of view it would seem preferable. Disclaimer: (just to avoid any sucking-through-teeth comments) he work will be done by a wheel specialist using the appropriate balancing/laser alignment/black magic and voodoo. I have considered using wheel spacers or 130/1-ton/FC/Rostyle/Wolf/Disco/aftermarket rims but they aren't appropriate for the custom requirements of the truck. And yes I'm aware of the costs involved (not bad actually). For further info on LR wheel offsets - this page is very useful: http://myweb.tiscali...tuff/wheels.htm Thank you! Quote Link to comment Share on other sites More sharing options...
Team Idris Posted December 8, 2011 Share Posted December 8, 2011 I'd say the perfect scenario occured if the centre line of the tyre was inline with centre line of two identical bearings. Then they split the load on average. I'd say the worse case scenario starts when the centre line of the tyre lines up with the outer bearing. Then it has the lions share of load and the inner bearing is just a guide. And pushing it further, so the tyre centre line is further out past the outer bearing, things get really heavy for the outer bearing. Then the inner bearing changes from a bottom load to a top load. Whatever the top force is on the inner bearing, it is added to the vehicle downforce on the outer bearing But all we really see is a reduction in bearing life. The outer bearing appears to be able to stand 100% of vehicle corner mass plus some more! So I wouldn't say there was a natural safe-point at which it suddenly went wrong with a little more offset? But a high offset with heavy offroad use will lead to a very short life if mud gets in there. So shorter inspection periods may be all you need to maintain a reliable vehicle. Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted December 8, 2011 Author Share Posted December 8, 2011 I've just noticed my lovely picture hasn't attached to the post - it really does say a thousand words! Its on my work PC so I'll attach it tomorrow! Quote Link to comment Share on other sites More sharing options...
muddy Posted December 8, 2011 Share Posted December 8, 2011 Might be worth considering what type of loads you will be placing upon the axle. Assuming a sailsbury axle has the same seperation as a rover type you could have a 110 hicap on its GVW + trailer noseweight placed upon the bearings and is considered 'safe' by LR. And if you have a 90 TC that will only really carry your shopping home you could have more 'offset load' placed on your bearings by the wheels and still be withing the factory limits. Does any of that make sense? I'm sure you picture says it all but you are effectivly getting a 5.5" wheel with the same distance from hub face to inner rim edge? as an FC wheel unlike '130' wheels that are a 5.5" wheel with an extra inch slapped on the outside? If this is right (probably not ) then the centre line of your tyre will actually be further inboard than a 750 on a FC rim and therfore place less stress on the wheelbearings. That all reads like mad rambleings but hey you might understand some of it. Will. Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted December 9, 2011 Author Share Posted December 9, 2011 Just before I have a proper read of your replies guys I thought I'd post the picture I meant to attach to the original post. Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted December 9, 2011 Author Share Posted December 9, 2011 Team Idris. That is a nice way of looking at the ideals of how the load is applied to the bearings and certainly supports my view. Muddy – it does make sense and again your thoughts seem to mirror mine – especially with a view to the “extra inch slapped on”. If we just consider the strain in relative terms (a spectrum ranging from a tiny SWB rim right up to a FC big-offset rim) then I think my custom rims will sit nicely within this ‘safe spectrum’. Effectively the rims I’ll be having made will be exactly the same as a FC rim except that the rim lip will be an inch closer to the hub. By that logic, if we assume that the FC rim with a 750R16 tyre places an acceptable load on the hub and bearings, then the custom rims would place less stress on the same parts as, while the inner face of the rim and wheel-centre will be in exactly the same relative position, the outer face of the rim and tyre would be closer to the hub (approx 1 inch). [Muddy, here we can say that the centreline of the tyre would be closer to the hub than it would be if the same tyre were fitted to the FC rim]. I’m sure that this is correct now, but being one of those people who needs input from others I’d welcome some confirmation of my pub-logic! The 110 load vs 90 pickup analogy is really useful, I would not want to rely on it (I would only fit the rims if they were strong enough for a fully loaded LWB) but as they will be fitted to a SWB SIII the reduced weight will offer additional peace of mind. Thanks folks! Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted December 9, 2011 Author Share Posted December 9, 2011 In summary (after all my waffle!)... I believe that fitting 750R16 tyres on FC rims onto a rover axle would place more stress/load on the hub and wheel bearings than fitting 750R16 tyres on my custom rims. If we take it that 750R16 tyres on FC rims on a SIII is within Land Rover tolerances then the same tyres on my custom rims MUST also be within those tolerances. Does this sound right? Quote Link to comment Share on other sites More sharing options...
Soren Frimodt Posted December 9, 2011 Share Posted December 9, 2011 Adding offset to the inside provides just as much strain on the bearings as adding to the outside (providing it's from the center between the two bearings of course) But with your setup I am convinced you will be safe. After all the hub-assy on a landrover is a very strong system, with very large bearings and material compared to most other 4x4's in the same weight class. But a thing that I have noticed through all my various land rovers, is that a Series hub-assy is in all aspects made stronger than that on a coiler. Funny thing really. Quote Link to comment Share on other sites More sharing options...
ejparrott Posted December 10, 2011 Share Posted December 10, 2011 Funny thing really. Not really, Series III's still using massivly over engineered British deisgn.....by the time of the coilers, accounts started influencing the design! Whilest no means an expert on such matters, I'm curious as to why the outer wheel bearing could at any point be considered as bearing all of the weight? I can appreciate that in certain conditions, such as cornering hard, one or other bearing may be placed under more load than the other, but would there not be a bending moment based around the stub shaft and hub assembly, so that whatever load is applied to the top of one bearing would be applied to the bottom of the other? I can see how the offset will affect the pivot point of this moment, but I still don't see how one bearing could be considered as taking all the load, unless they were to be out of adjustment? Quote Link to comment Share on other sites More sharing options...
Soren Frimodt Posted December 10, 2011 Share Posted December 10, 2011 ejparrot: Well yes, you're kind'a right, it will have that "bending force" but in theory you could place all the weight on a point just below the centerline of the one bearing, and all the weight would be on that one. But for the most it'll shift and generally be about the same on both bearings all the time. But as you don't have a pivot point between the two bearings, it has to use one of the bearings as the pivot point in that bending force. Hence in certain scenarios one bearing will have more load than the other. Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted December 11, 2011 Author Share Posted December 11, 2011 Thanks for the replies guys and to Soren for reassuring me a bit. I think it'll be definately less of a burdon on the axle than the same tyre on a LR-approved FC rim as such I think it'll be a winner. I'll end up with standard, common 750 tyres - nice and narrow so no extra strain on diffs - but with that tiny bit of extra offset that will help fill the arches (asthetics) as well as improving turning-circle and cornering (albeit slightly). Just waiting to hear back from Matt Lee - I had a quote a few years ago (v.reasonable) just need to see if it is a similar price now Quote Link to comment Share on other sites More sharing options...
twodoorgaz Posted January 4, 2012 Author Share Posted January 4, 2012 Much like waiting for a bus... While waiting to hear back from Matt Lee, 4 one ton rims came up at a good price so I bought them. Need a 5th tho if anyone knows of one. Quote Link to comment Share on other sites More sharing options...
Steve Hiatt Posted January 5, 2012 Share Posted January 5, 2012 In my experience of running wider offset wheels for a number of years it's the stub axle that's the weak link, not the bearings. Quote Link to comment Share on other sites More sharing options...
RobotMan Posted January 6, 2012 Share Posted January 6, 2012 It will also give you an increase in scrub radius. Not enough to be of concern. Quote Link to comment Share on other sites More sharing options...
Pinkrover Posted January 6, 2012 Share Posted January 6, 2012 I read this with interest, but slightly too late. I've just fitted some Mach 6 rims to my 101 after chatting to matt Lee I decided to go for the max offset, on 10" rims fitted with 315x75x16 tyres, so the inner wall of the 315 tyre is where the original 900x16 inner edge would be. This was to retain the turning circle and hopefully increase stability when laning. I have PS fitted and have found no issues yet though I may fit a slightly smaller pulley to the PS pump to boost the assistance when stationary. I did a 1000km trip over to Holand for new year and had no problems. I'll post again when I have put a few more Kilometers the wheels and tyres Quote Link to comment Share on other sites More sharing options...
Disco-Ron Posted January 8, 2012 Share Posted January 8, 2012 That 101 needs defender arches on it now.......... looks good though! Quote Link to comment Share on other sites More sharing options...
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