New bigger alloys, drastic drop in mpg??

jefflucas28

Tuner
Points
62
Location
Hertfordshire
Car
2000 Clio S 1.4i 8v
Hi all,

Just fitted some 15" alloys, replacing the standard 14" alloys, however £20 worth of petrol used to get me 225 miles, now im on the red at 150:( miles.

Is it really meant to be that dramatic? any advice???

Cheers
 
1' should not make that much of a difference, providing they used a lesser profile on the tyre size
 
If the overall diameter is within 3% the extra width will increase fuel usage slightly. But not by this amount. I could be the cold weather. All engines are thirstier in the cold. Short journeys exacerbate this.

Tyre pressures?
 
they are definately within 3 %, im going to try a couple of tanks of petrol and see if its a regular thing. i cant be losing 40-60 miles in fuel, and what feels like a lot of power loss for the sake of some nice wheels...hmmmmm a learning curve indeed!
:-s
 
Is the rolling radius so much smaller that the speedometer and mileage recorder are simply recording much less mileage than has actually been covered? This could happen if you've fitted much lower sectional profile tyres than originally fitted. You really should stay within 3% either way, although 5% is no big deal as long as the wheels at the front remain clear of the bodywork and wheel arch liners on full lock.

Please send me the tyre dimensions for both sets and I'll work out the rolling circumference of both sets.
 
Is the rolling radius so much smaller that the speedometer and mileage recorder are simply recording much less mileage than has actually been covered? This could happen if you've fitted much lower sectional profile tyres than originally fitted. You really should stay within 3% either way, although 5% is no big deal as long as the wheels at the front remain clear of the bodywork and wheel arch liners on full lock.

Please send me the tyre dimensions for both sets and I'll work out the rolling circumference of both sets.
good point hdi,
and this is actually fact, because your speedo is set up in the factory for 14' wheels, with a bigger wheel, it takes longer to complete a full rotation, which would put out the clocks, the bigger the wheel the more differance

try a full tank of juice with the 15
do the exact route and driving style with the 14' and see what happenes
you never know, it could be the clocks that are confused:confused:
 
Yes i had suspected perhaps it was the speedo that was out. I've gone from 42mpg to 33mpg literally over night. Old tyre sizes were 175/60/14, now new ones are 195/50/15. I used the alloy wheel calculater thing and its saying there's a 32.86 mm difference. (Dunno if this helps hdi)

Have checked a double checked tyre pressure, ensured there's no rubbing within wheel arches and there's no contact when on full lock.

I've just cleaned out my K&N element (full of road salt), but im sure its not this as the change in mpg has come since fitting wheels.

Decided to take car in to garage just to have wheels checked out (tracking & balancing), just to ensure there isnt any obstruction or fault in installation etc.

Over all, very confusing. I'm thinking it can only be the car's speedo thats out. And in this case, im thinking now the mileage will be inaccurate. Something im not too keen on knowing about.

Any suggestions?? Thanks all :)
 
According to the calcs you are 1.77% up with a 10mm increase on rolling circumference and well within the 2.5% recommended so you should see no difference tbh.
 
Thanks stamford, i did think the difference was minimal (reason why i went for 15's)

Ok so maybe it could be my K&N element? Drove past 2 seperate gritters on M1 at 80mph on the way back from picking up the wheels. Front of car shower in salt, fed up cold air intake and on to element. But surely this wouldnt affect mpg that drastically? Actually it could have been that as ive only refill once sitting hitting the gritters......hmmmm i sense another learning curve coming up! :-S
 
You've increased the rolling radius by just over 1.9%. This should not cause such a drastic change in fuel usage.

It could be the cold weather - petrol engines particularly will demand richer fuelling during warm up phase.

I wouldn't take 'em off yet. I do not think the wheel/tyre combination is the problem. You might not even have a problem. You can really only compare fuel usage figures if you're using gathered data over several months
 
Last edited:
Going from Michelin Energy to a high rolling resistance tyre may increase fuel consumption but not by this much.

Were any other modification done? Is the tracking/toe set correctly? Are the brakes dragging perhaps? Jack up the car and check the wheel bearings for rolling resistance, the wheels should all spin fairly freely.
 
Going from Michelin Energy to a high rolling resistance tyre may increase fuel consumption but not by this much.

Were any other modification done? Is the tracking/toe set correctly? Are the brakes dragging perhaps? Jack up the car and check the wheel bearings for rolling resistance, the wheels should all spin fairly freely.

I suspect it could be the brakes. The front wheels were really rolling that freely when i changed them over. But surely this would have been noticeable before the wheel change?!

Im gonna have to get her check out by a mechanic, my skills dont stretch as far as bearings and the like. Kwik fit here i come ! :-S
 
Things get knocked and it is easy to cause a problem, the hard part is tracking it down. It might have been a case of the bearing being on its way out and removing/fitting a new wheel was just enough of a jolt to do it.
 
I'd use a local garage. Explain the problem and ask them to CHECK the tracking. Balance is not an issue but they should also check the bearings for wear/play. You shouldn't have to pay too much for that.
 
ok so ive been to kwik fit, they got it up on the ramp and confirmed NO faults. Advised me to 'check the forums'!! Luckily didn't charge me anything so chuffed about that.

So still clueless about fuel loss but swung by halfords on way home and picked up new fuel&oil filters, and new oil & spark plugs and funnily enough found some grooved racing front discs(specifically for clio mark 2) in the clearance for £10 down from £92.99. not bad ay!

im starting to think the only answer is the computer is off. she just happens to need a service but i doubt this is the fault as the time frame from installing new wheels and losing the fuel is too close to be anything else.

does anyone know if i can get speedo recaliberated??

thanks :)
 
No, a 1.9% change in fuel consumption would be barely noticeable. TO be honest, why don't you just monitor your fuel usage over 2-3 weeks. Or fill the tank, record the mileage and then see how much it needs to fill 'er up again. That's the only true way to get a sensible reading.
 
yeah you're right - i'll sit tight for a week or so. If the mpg remains around 33 then they will have to come off. Original mpg was a good 42 with induction kit etc. I can always sell the wheels on. Shame though as they look proper 'tidy'.

:-S
 
There's no way that a modest change of wheel/tyre will cause an effect such as this. You're well within all the sensible parameters. Sit tight and see what transpires. Fill the tank and note the odometer reading. When it's down to 1/4 fill up, noting how many litres are required and note the mileage again.

Even if this seems to confirm your fears that the wheels are the problem, put the old 14" ones back on and do the same again.

Don't rush to conclusions with this issue - it would be a shame to sell on a set of wheels & tyres that you like very much on account of what might well be just a bit of over anxious reasoning.

Further, if there is another co-incident problem it will have to be fixed anyway.

Cheers,

Regards,

Paul.
 
Thanks garner and hdi.

Pgarner, the fact that you've changed to larger wheels and noticed no difference confirms my confusion. If that makes sense. Although i must add, a slight alteration such as wheel width and surface area on the road will affect my 75bhp clio far more than it will you 184.6 bhp bora.

Its very clear whats happening, in terms of fuel consumption, thankfully the clio is very simple. £20 equats to near enough 200+ miles (given the current cost of petrol) and £10 equats to 100 miles give or take 4/5 miles. Having topped up an additional £10 worth of petrol after running it nearly emptylast night, im finding myself on the red with the light about to come on after only 60 miles.

Quite a hefty loss as you can see, around 40%. Also, a noticeable loss of power. I'm beginning to think the 75bhp 8 valve engine simply cannot handle the extra traction. I'm realising that with an engine as 'weak' as this, things become very fragile if you want to maintain acceleration and general response.

Your thoughts?
 
Thanks garner and hdi.

Pgarner, the fact that you've changed to larger wheels and noticed no difference confirms my confusion. If that makes sense. Although i must add, a slight alteration such as wheel width and surface area on the road will affect my 75bhp clio far more than it will you 184.6 bhp bora.

Its very clear whats happening, in terms of fuel consumption, thankfully the clio is very simple. £20 equats to near enough 200+ miles (given the current cost of petrol) and £10 equats to 100 miles give or take 4/5 miles. Having topped up an additional £10 worth of petrol after running it nearly emptylast night, im finding myself on the red with the light about to come on after only 60 miles.

Quite a hefty loss as you can see, around 40%. Also, a noticeable loss of power. I'm beginning to think the 75bhp 8 valve engine simply cannot handle the extra traction. I'm realising that with an engine as 'weak' as this, things become very fragile if you want to maintain acceleration and general response.

Your thoughts?

I really wouldn't have thought that you would loose that much from changing the wheels. Are you up to date with the services etc?
 
as it happens its been 12,000 miles since last service. Hence buying all the bits today in time for a service either one night this week or at the weekend.

However, surely its got to be something to do with the wheels as all this fuel loss malarky started straight after i put them on?!! I'm certain to go mad at this rate.

I think the only answer is to have her serviced, carry on as normal until friday and then make a decision. Can't afford to throw away 40% of fuel. No one can im sure.

:-:)-(
 
as it happens its been 12,000 miles since last service. Hence buying all the bits today in time for a service either one night this week or at the weekend.

However, surely its got to be something to do with the wheels as all this fuel loss malarky started straight after i put them on?!! I'm certain to go mad at this rate.

I think the only answer is to have her serviced, carry on as normal until friday and then make a decision. Can't afford to throw away 40% of fuel. No one can im sure.

:-:)-(

I think thats the way forwards mate try the service then decide. It may even sort out your prob...
 
Dont sell the new wheels until you have tried the old ones. I'd be interested to know if the new wheels are much heavier than the old ones? I'd still be surprised if the wheels were causing the loss of MPG.
 
waynne i honestly think it has to be the wheels, the loss of power also connects to this too.
i really dont want to get rid of them and then have the hassle of selling them on also. But the fuel loss is so obvious, i can't do one relatively short journey now without the needle dropping dramatically. Its a double kick in the balls to have not only a slow car but one that drinks like a dog on a hot day!

Im starting to long for my old wheels, purely for the effect they have on the car. I think if i do go back to the old ones. ill keep the 15's for a new car - they have interchangable centre badges so i can just source new badges if i dont get another renault.

Learning curve number 4,555,628,525,329!!!!!
 
I'm still thinking that this is an unfortunate coincidence. There's no way such a modest change in wheels and tyres could possibly cause this problem.
 
Well HDi im still going to give it a couple more refills and see whats happening, to be honest i feel as if i dont need to though, its happening infront of my very eyes every time i turnover the engine!

The oil change and filter changes may make a difference. but like i said before its too coincedental, the two factors, wheels changed, petrol lost etc.
 
Before you sell them though, try and week or so with the old wheels back in place. At least then you can assure yourself that the wheels were the cause.

How poor is the performance? And does the engine still pull smoothly, despite having even less power than normal?

Exhaust? Clean?
 
Oh no i wouldnt sell the wheels on immediately, i'd definately make sure all was back to normal before so. The engine does still pull nicely, but just takes longer in lower revs and feels like its generally pulling more weight. And the exhaust is fine as far as im aware.

ok to try to explain the power loss:


in third, i would build revs up slowly to get to 40mph, then once i'm crusiing at 40mph if i kick the throttle down, the induction kit kicks in and she flys off (very impressive for a 1400 8v) if i do that now, the response is noticably slower and not as...'responsive'. and other things like going up hill, generally sluggish and a sense of being 'weighed down'.

just leaving work now. back in an hour or so. thanks hdi.
 
How about weighing one of each of the wheels. Bathroom scales should give you an idea of the difference if it's that great. If the rolling mass is much larger it might be rotational inertia that you're feeling.
 

Similar threads


Please watch this on my YouTube channel & Subscribe.


Back
Top