Tuesday, Apr 15, 2014 at 13:39
33" 285/70/17 aren't to big BadDude but tyres need careful consideration as they are probably the thing you can change that has the most effect on a cars performance.
You may even be better with the mud tyres on alloy rims - its a balance and all should be considered together.
Yesterday we fitted some real tyres, 37" crawlers for the fun weekend ahead, and tyres like this can go much further in rocky muddy conditions but are a noiser pain mostly.
I believe that muddies are not the best tyre for most of our applications anymore as we have things like Cooper ST Maxx and equivalents available now.
These tyres are seriously strong and tougher than most muddies and don't leave big gaps between lugs that allow stakes in, and kept down noise increase.
Tyres have an effect on fuel consumption and power and gearing to, but this may be positive as
well as negative.
Leaving aside gearing for a second, contact patch area and weight of tyre/wheel are what determines those factors.
Generally when you go to bigger tyres they weigh more and this weight has to be accelerated up and down all the time and this cost fuel and power - gearing can make it worse again. (as a rule of thumb the effective increase in weight is about 2.5 times the actual increase)
Consider this , if you went from 32 to 33 inch tyres which add 2kg per wheel then used alloy wheels instead of steel which saves 3kg per wheel then you would be better off by 1kg and provided the air pressure was adjusted as it should be for same contact patch area then no more fuel would be used at same speed.
Gearing also needs to be considered and can again make things worse or better.
For example my car comes with 31" tyres and I have a set of smaller width 34 " tyres.
So not far from 10% change in gearing - in fact gearing change is so much that I can run the car in 4th instead of 5th gear.
This means that I can for around the same engine revs use 4th which is both stronger and a direct drive gear (not overdrive) which is again more efficent.
There are a few car dependant second order issues (I've kept the above simple) , but in your situation I'd consider the new breed of crossover mud/at tyres of larger diameter , keep pressures up when touring and consider matching them with alloys provided rims are not exposed, and enjoy the advantages of more ground clearance.
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Follow Up By: Member - OzBadDude - Tuesday, Apr 15, 2014 at 14:35
Tuesday, Apr 15, 2014 at 14:35
Great insights Robin.
There are issues in your reply that I hadn't thought of at all.
I'm thinking of going with the Mickey Thompson Baja MT. This is rated by them as 40% road and 60% dirt/mud. Rather than go with one of the 80% mud tyres.
I'll do this while I have separate tyres/wheels for road and off-road. When my road tyres wear out, I will probably just use the MTs until they wear out, then go with a more balanced crossover tyre.
Everyone should have really tough looking tyres at least once, right? :)
OzBadDude
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