[viXit]

Originally Posted by Turbotechnixx

The drop in fuel efficiency was pretty instant. I realized it in the first 20 mins of driving. I have got my vehicle serviced just a month back (2000 kms back) so the question of service issue etc doesn't arrive. To rule out the possibility of bad fuel, I have emptied the tank entirely and refueled at a renowned fuel station. Still no change.

Because it's a new tyre coefficient of friction is more, hence lesser mileage. But your MID is wrong . it's not by 2kmpl

you should calculate mileage by tankfull to tankfull method, then you will get the correct measure of kmpl. it will barely be 0.5 kmpl and will be back to normal in no time.

The MID is showing wrong kmpl reading because it doesnt know that you have upsized your tyres.

Take a chill pill and enjoy your awesome car with the new tyres.

[evil_grin]

Originally Posted by Turbotechnixx

I have a Skoda Octavia TDi AT (2019).

But I am also not OK to compromise on the fuel efficiency of the vehicle by such a big margin.

As owners of D segment cars, especially fun ones like the Octavia, it doesn't behoove us to worry about minor things like fuel efficiency.

There are more important things to worry about.

Like trips to plan. Places to see.

[diavolo]

The diameter being higher, so can cover longer distance using same power is often flawed, these are taller tyres, say 5mm taller, so the vehicle profile increased, so more wind resistance.
Same contact patch, but higher profile means the tyres are bigger and more expensive also

[sunikkat]

That’s surprising. I am running on upsized 225/17/45 and have not noticed any drop in efficiency. Either it’s because my upsize is only 0.3% deviation or I am/was not closely observing the fuel efficiency to make a right comparison.
Personally I feel a profile of 60 is going to rob some fun out of the car.

[IshaanIan]

Originally Posted by RubberGuru1113

I had specifically listed down a few sizes where it is better to up-size rather than go with the OEM fitment size. Perhaps you didn't own any vehicles with a problematic stock-fitment size. Like I mentioned, if you cared to search this very forum you'll find entire threads dedicated to tyre failures on these sizes.

Could you perhaps add links to the threads that you are talking about where particular tyre sizes are found fault with? I understand that perhaps a tyre size might be annoying if it is not common and thus you do not get many tyre options for that size, but a problematic tyre size itself? I mean isn't that why you have different types of tyres and rubber compounds? Want more durability get something like a geolandar, want more comfort primacy/decibel/premiumcontacts, want more efficiency XM2, want more grip Advan/Potenza etc.?

[RubberGuru1113]

Originally Posted by IshaanIan

Could you perhaps add links to the threads that you are talking about where particular tyre sizes are found fault with? I understand that perhaps a tyre size might be annoying if it is not common and thus you do not get many tyre options for that size, but a problematic tyre size itself?

Hi, attaching 2 threads dedicated for people who faced issues on 195/55R16 (Baleno) and 205/50R17 (EcoSport). It's not just for uncommon/niche sizes, 195/55R16 is a fairly common size, comes as stock fitment on i20, Baleno, Verna, Ciaz, Polo/Vento Highline, etc., and while Baleno's case is more common (owing to the vehicle's popularity), I have personally seen the issue across models/brands.

https://www.team-bhp.com/forum/tyre-...-attitude.html (Apollo Tyres, their Alnac 4G sidewall issues, and their attitude)

https://www.team-bhp.com/forum/tyre-...-r17-size.html (Ford EcoSport Facelift: Tyre bulging issue (R17 size))

Apart from these, there are multiple posts on ownership threads and tyre/wheel upgrade threads.

What I referred to as "problematic sizes" are those where the profile is very low, resulting in a short sidewall which on bad roads are highly prone to cuts/damages. This can happen on any brand from Michelin to Ceat and has little to do with the quality of the tyres. Reason is that the short sidewall means the possibility of a complete sidewall collapse and impact damage becomes very high even for a slightly under-inflated tyre.

The phenomenon of pinch impact damage itself, I have explained on a different thread with visual aids, have quoted the same below, suggest that you navigate to the answer so that the pictures are visible.

Originally Posted by RubberGuru1113

As a tyre industry professional, I would strongly dissuade you from going for 33 PSI and there is a scientific reason. the sidewall height for 225/50R17 is only 112.5 mm (when not under load), and subtracting the rubber part on the tread and the bead, it comes down to just under 80 mm.

The unit deflection of the tyre under load goes up by 25% @ 33 PSI compared to @ 36 PSI. Considering a pothole size of 50 mm (of which there are many in bangalore), in order to avoid impact damage on the inner side of the tyre, the loaded sidewall height has to be at least more than that 50 mm value, which would happen only at 36 PSI for a load of 600 kg per tyre (which would correspond to the full load condition of the BMW 3 series). On the other hand, we do not top up the pressure every day, and the average pressure loss is 1~1.5 PSI per week depending on type of usage. This is how I came up with the value 39, assuming a bi-weekly air top-up schedule which means at no point are his tyres at a pressure below 36 PSI.

To help understand how low pressure causes impact damage on potholes (especially for low profile tyres), I 'm attaching an image of how the tyres would deform so that you can visualize better.

Attachment 2356670


Hope this helps!

The taller the sidewall, higher the clearance inside the tyre, and lower possibility of impact damage. Of course there are multiple factors into play - vehicle load, pressure maintained, road conditions - but the tyre size and hence the clearance available for the sidewall to flex remains the same, and it is beyond doubt that increasing this clearance reduces the possibility of impact damage multifold, of course, keeping the diameter within permissible limits so that there is no fouling with the dampers/wheel arches.

Originally Posted by IshaanIan

I mean isn't that why you have different types of tyres and rubber compounds? Want more durability get something like a geolandar, want more comfort primacy/decibel/premiumcontacts, want more efficiency XM2, want more grip Advan/Potenza etc.?

You're 100% right - the materials used in a tyre will give different performance outputs like how you mentioned - like fuel efficiency, durability (tyre mileage), wet and dry traction, etc., but pinch impact has to do with the tyre's dimension itself, or more specifically, the clearance on the inside of the tyre, which is a value of around 30 mm lower than the tyre's section height. The loaded section height would be even lower than that. Refer the image below for clarity -



So if you ask me what is the right value, for smaller cars (upto Celerio/Tiago) I would have a thumb rule of minimum 110 mm in section height (section width multiplied by aspect ration) while for cars bigger than that I would have at least 115 mm.

Mentioning the section height of some sizes so you can get an idea :-

195/55R16 - 107
205/55R16 - 113
205/50R17 - 103
185/55R16 - 102
185/65R15 - 120
205/60R16 - 123

Another point to note is that on the Baleno, there are hardly any issues reported on the 185/65R15 whereas it is disproportionately more in 195/55R16.

[venkyhere]

I've said this earlier in this thread, repeating once again :

Before we delve into "why did the 65 profile consume more fuel than the 60 profile" type questions, the simplest thing that needs to be done by anyone when they swap tyres, is this :

The tyre already has three parameters describing it's 'nature' on it's own sidewall :
TRACTION AA/A/B/C
TREADWEAR <number>
TEMPERATURE A/B/C

The bigger the number or earlier the alphabet, the better that tyre is, in that regard. Taxi people will prefer a tyre with highest TREADWEAR (they want the tyre to go on and on) and wont care about traction or temperature ; whilst people who want to do trackdays will want a tyre with TRACTION AA, and TEMPERATURE A - they wont care about treadwear number being low.

So the first thing to do, when swapping tyres, is to compare what are these three things on the tyre going in, compared to what's coming out. Usually, tyres with high traction rating will be "softer" (ie press down more into the road, flex more before sliding off during acceleraton or braking, for as much as possible, without giving up their hold on the contact patch) - the price to pay is that they will have higher rolling resistance (more heat generated by sidewall flexing - that energy has to come from the driveshaft) which translates to marginally more fuel consumption.

When we have the old and new tyre side by side at the time of swapping, best to compare these three parameters, apart from the brand and the size/aspect etc.

[RubberGuru1113]

Originally Posted by venkyhere

I've said this earlier in this thread, repeating once again :

Before we delve into "why did the 65 profile consume more fuel than the 60 profile" type questions, the simplest thing that needs to be done by anyone when they swap tyres, is this :

The tyre already has three parameters describing it's 'nature' on it's own sidewall :
TRACTION AA/A/B/C
TREADWEAR <number>
TEMPERATURE A/B/C

The bigger the number or earlier the alphabet, the better that tyre is, in that regard. Taxi people will prefer a tyre with highest TREADWEAR (they want the tyre to go on and on) and wont care about traction or temperature ; whilst people who want to do trackdays will want a tyre with TRACTION AA, and TEMPERATURE A - they wont care about treadwear number being low.

So the first thing to do, when swapping tyres, is to compare what are these three things on the tyre going in, compared to what's coming out. Usually, tyres with high traction rating will be "softer" (ie press down more into the road, flex more before sliding off during acceleraton or braking, for as much as possible, without giving up their hold on the contact patch) - the price to pay is that they will have higher rolling resistance (more heat generated by sidewall flexing - that energy has to come from the driveshaft) which translates to marginally more fuel consumption.

When we have the old and new tyre side by side at the time of swapping, best to compare these three parameters, apart from the brand and the size/aspect etc.

Hello! I work in the tyre industry and I’d warn you against placing too much importance on Treadwear/Traction/Temperature markings. They are called UTQG (Uniform tyre quality grading) and subject to legal scrutiny only in the USA. For tyres sold in other markets, the manufacturer only does a self grading and is not subject to legal scrutiny.

One can compare UTQG values of different tyres from the same manufacturer to get an idea of the difference in performance, but would strongly advise against making purchase decisions by comparing UTQG values of tyres from different manufacturers.

India has brought a (for now voluntary) energy efficiency labelling system for tyres like the star rating for home appliances, based on rolling resistance values as tested in an accredited lab. That can be a starting point. Eventually I think they would bring a labelling system like Europe for Wet Grip, Noise and Rolling Resistance.

[santhosh_lv]

Can you clarify the model of your Continental tyres were you using before and after your upgrade?

Rolling resistance plays a key role in FE. I had a Bridgestone 195/55R16 for my Fluidic Verna and I changed it to Continental Max Contact MC5 195/55R16. Here there is no upgrade to the profile, but my FE increased by 2 KMPL in the city and about 3 KMPL on highways. This is coz MC5s have lower rolling resistance and the amount of engine thrust required to push the car forward is less.

[Turbotechnixx]

Thank You all for your valuable inputs. I finally swapped my tyres back to the stock size. I am now running on 205/55/R16. Fuel efficiency figures has been restored to the usual.

[ASHUJNMC]

Originally Posted by Turbotechnixx

Hello guys,

I have a Skoda Octavia TDi AT (2019). The vehicle had come with 205/55 R16 tyres. After using the tyres for close to 43k kms I replaced them with Continental 205/60 R16 (note the difference in the ratio).

) I should get marginally lesser fuel consumption. But to my surprise I am getting a reduced average of nearly 2kmpl. I confronted the tyre seller for suggesting me to buy bigger sized tyres. He claimed that everyone goes for this upgrade and ideally there should be no deviation in average as more distance is covered per rotation by the bigger wheel.

But I am also not OK to compromise on the fuel efficiency of the vehicle by such a big margin. Please advise. Many Thanks.

I changed my Zest's old B250 with Yokohama Earth E1 at front and moved those older ones at back. New tyres were of the same specs and noticed 2 KMPL lesser FE. But changing to B290s didn't improve the FE again, probably because older rubber gets harder with lesser rolling resistance and newer will be softer with more rolling resistance compared to old one.

[Rama Naveen]

Hi Guys,

Please forgive me, if I have hit the wrong thread but felt this is most appropriate one as Iam really curious to get the experts opinion.

I own Tata Bold Diesel XT and I changed the stock tyres & alloys from 175/65 R15 to 175/70 R14 at 20k KMS.

Also I got Roger AB's installed. Together the Car provides great comfort and glides through tarmac or potholes smoothly. It has not affected the mileage too. They are running Good Year triple max assurance and just great.

Current mileage is 71000kms.

I was wondering in my next upgrade, will this be a safe move if I change tyres to 165/80 R14 ? I have uploaded the pic from https://www.calculator.net/tire-size-calculator.html?