I changed all 4 tyres on my CR-V a month ago and since then have noticed a drop in mpg from about 28 down to 24 mpg, a drop of about 15%. I have searched a number of tyre manufacturer's websites for information on roll resistance but could find little information. Does anyone know whether comparative figures are available for various makes and models of tyres? While my figures are only approximate, if they are representative, then this is a serious increase in motoring costs.
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GP, I know you probably thought of this already, however, have you double checked your air pressure? A lot of tyre chain staff just put a random figure in - I have seen anything from 20 lbs to the air line being left on until it blows off, depending on how much interest / distraction the current staff member is showing / suffering. Low tyre pressure can make a pretty big difference on the mpg, and if they were lazy all round, it might not be enough to make it feel real different, but enough to show on the mileage.
If that is ok, did you get brakes done, checked at the same time? Possibly suffering from the new brakes bedding in? Maybe got a handbrake that isn't releasing fully when you put the lever down?
Wouldn't think changing tyre make /pattern would make that much of a difference unless it was an extreme change - you are now running MUD A/Ts or slicks, however I am sure there are folks on here who may enlighten us.
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we lost 3 to 4 MPG on a 1.9 Diesel Punto by fitting reinforced tyres instead of the `fuel saver/eco` type.
The reinforced tyres have lasted double the mileage on the front end, still not sure whether it was worth it, but the extended tyre life was no surprise looking at the robustness of the reinforced. The `fuel savers` almost look like marshmallows in comparison.
That 3 to 4 MPG lost is based on an original 53 MPG on multi cold stop start work for the Punto D, and was done to solve a tyre wear problem caused by a heavy front end and cornering.
It handles better too and `turns in` sharper.
I was wondering whether to fit reinforced to the 1.3 multijet, but I think the fronts are going to get to around 24,000 on the `fuel savers` so I guess there is no point.
I thought eco low rolling resistance tyres were a con, but now I have had the empirical evidence, I believe in them... well... almost ;)
Greasy Pole, were your two sets of tyres both the `fuel saver` type?
Regards
Regards
Edited by oilrag on 12/02/2008 at 10:03
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Thank you Mr Wednesday for your thoughts. I didn't double check the pressures when the tyres were changed so it is just possible that they were not spot on although I am reasonably sure that they were ok.
The car had a main dealer service just before the tyres were changed. The service seemed fine and the handbrake releases ok so I don't think that is the problem.
I changed the tyres because they were getting a bit close to needing replacement and as we were going to Scotland in the New Year and taking friends, I wanted to be sure that the tyres had good tread. The original tyres were BFGoodrich 215/65R16 Traction T/A but the replacement tyres were Avon Ranger 65 discounted. I must admit that I never gave a thought to eco tyres and I only asked if they were compatible with the spare (BFGoodrich) which they said they were.
Oilrag, it seems from your comments that there might be something in this mileage thing from your experience. Roll resistance figures must be available to the car manufacturers but none of the tyre manufacturers that I visited on their websites gave any of that information. The original tyres I assume would have a low resistance figure but I don't know whether they are eco or not. The same applies to the new ones. What I also notice is more road noise and a smell of rubber, both of which suggest something but I'm not sure what!
I am at a loss what to do, whether it is worth changing the tyres but I need some facts before I do.
Regards
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I lost about 10% of my fuel economy when I switched from the awful Dunlop SP Sport 2000E's to Goodyear Eagle F1 GS-D3 all round.
Edited by Webmaster on 16/02/2008 at 12:09
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The original tyres were BFGoodrich 215/65R16 Traction T/A but the replacement tyres were Avon Ranger 65 discounted. I must admit that I never gave a thought to eco tyres and I only asked if they were compatible with the spare (BFGoodrich) which they said they were.
Not strictly to your question, but there's a common view that one shouldn't mix tyres on the same axle anyway; and on 4x4s generally, any material difference between tyres anywhere (including the amount of wear) is best regarded as a bad thing.
On the CR-V there is no centre differential. This is not a problem when everything is working as intended, because the 4wd only engages when there is slippage anyway. What you don't want though is any tendency for 4wd to engage when there is no slip as the transmission will wind up and damage something somewhere. The multiplate clutch is probably the weak (i.e. the least strong) point as there have been failures of these.
There's clearly a fair amount of tolerance to differences in rolling radius between wheels otherwise you'd have a problem every time you went round a corner, but I prefer to play safe. I rotate the wheels about every 7,000 miles and replace all 5 tyres at the same time. I have done about 90,000 miles on two of these cars without any problems (which I accept proves nothing statistically).
Edited by Manatee on 14/02/2008 at 08:54
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Two thoughts;
Compared to when they ere new the rolling circumferance of the your old tyres will have reduced by around 1.5% by the time you changed them due to the tread wearing off.
But more significantly I noticed when I was wandering around in the tyre fitters, where the tyres were stored upright on parralel bars, there was a big variation in the height of tyres of the same size from different manufacturers. It appeared to be as much as an inch in some cases - so perhaps your new tyres are just small for their size?
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Gongfarmer, that's a very interesting point regarding the varying heights of tyres from different manufacturers. I shall measure mine in the daylight! :) if the diameter does vary by as much as an inch then, if my maths is correct, the circumference would vary by about 2%. This in itself would not account for all the loss, and anyway, new tyres would generally be of a greater diameter than worn tyres, presumably giving longer mileage.
Manatee, thank you for your observations but do I understand correctly that you change all 5 tyres every 7000 miles or have I misunderstood completely? ;) You have a point though about mixing tyres! The spare that I have is completely unused but I did ask whether the new ones were compatible with it. I now wonder if I should go back to National to take it up with them.
Regards
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Greasy Pole, apologies for my sloppy wording. I swap all 5 wheels round with each other (there's a diagram of which goes where in the handbook) so as to even out wear and bring the spare into play. This I do roughly every 7,000 miles. They all wear out therefore at about the same time, at say 25,000 miles and I replace them all at once.
It's a bit of fag to swap them round, but I'm pretty sure the tyres last longer overall, as they wear more evenly across the tread when swapped about.
I doubt I'm making any material difference to the mechanical welfare of the car but at least I never have to have an odd tyre through wearing them out at different times and not being able to match the existing ones.
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Manatee, thanks for clearing that up :) and thanks to everyone for your comments. I think I will have to contact the manufacturers directly to seek an answer.
Greasy Pole
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