Styling 17" wheels on a Grande Punto

[Brianmerc]

Hi there,

My 18 year old son has a 2008 Grande Punto Stripe 1.2 and he wants to change the wheels. The current wheels are 15" and he wants to change to 17" Wolfraces. He's going into the alloy wheel specialist next week. I've told him to make sure the brakes will still be ok and that the larger wheels will not rub on the wheel arches, etc, etc. I'm sure the alloy wheel specialist will sort it all out as they are a reputable dealer but one thing I don't understand is how the speedo will still be accurate with the bigger wheels? Surely it will need recalibrating as 1 revolution of the 17" wheel will cover a greater distance/circumference than the 15" wheel!

Has anyone else changed out 15" wheels for 17"'s on a Grande Punto? Any help/advice appreciated.

 

[Ffoxy]

Hi there,

My 18 year old son has a 2008 Grande Punto Stripe 1.2 and he wants to change the wheels. The current wheels are 15" and he wants to change to 17" Wolfraces. He's going into the alloy wheel specialist next week. I've told him to make sure the brakes will still be ok and that the larger wheels will not rub on the wheel arches, etc, etc. I'm sure the alloy wheel specialist will sort it all out as they are a reputable dealer but one thing I don't understand is how the speedo will still be accurate with the bigger wheels? Surely it will need recalibrating as 1 revolution of the 17" wheel will cover a greater distance/circumference than the 15" wheel!

Has anyone else changed out 15" wheels for 17"'s on a Grande Punto? Any help/advice appreciated.

17's can be dodgy on a 1.2, not always, depends how the driver uses the car, 15's are easier on the gearbox & final drive for the low powered engine.

I'll pop a calculator on here later to help re-calculate tyre size for the larger rims by choosing a lower profile, which will probably make the ride harder /crashier.

Here you go
http://www.kouki.co.uk/utilities/vis...?wscr=1024x768

 

[JimbbobW1977]

Few stories of gear boxes going pop on 17'' on 1.2's especially with younger drivers as they tend to drive a lot harder.

 

[Thomas_Si]

I think the general advice when upgrading to 17's is to choose a lightweight set so as not to put too much extra strain on the gearbag, & drive it sensibly or it will give out at some point.

With regard to the tyres you need some tyres with a lower profile so that the overall diameter of wheel plus tyre is about the same as what you started with.

Re: Instead of 175 65 R15 you want 205 45 R17 if memory serves.

This page should answer any questions you might have:

http://www.carbibles.com/tyre_bible_pg2.html

I know a few people have gone with wheel spacers as well to make the rear wheel sit out a bit wider for asthetics as well.

Hopefully if they are a good dealer you shouldn't have any issues.

Finally make sure to get some kind of locking wheel nuts so the local rabble don't run off with them.

 

[sledge]

Increasing the diameter of a car wheel will increase the amount of torque needed to turn it at any given speed. Its weight or mass in this instance is of no consequence.

Remember O level physics????...Torque = Force x distance

Force stays the same, thats provided by the engine but the distance, in this case increases. The distance being the measurement from the centre of the wheel to its outside edge. Hence an increase in torque.

If the gearbox of the car can handle this increase in torque it will see......well its no problem. If it cant...well the results are going to be obvious. But bear in mind that there has been several somewhat dubious cases of 1.2 gearbox failure mentioned in here and the common factor seems to have been the fitment of larger diameter wheels....hhmmmmm.

Its my belief that the 1.2 gearbox has no reserve capacity for any extra prolonged torque and it is operating right at its design limit under normal use. Like my esteemed associate Ffoxy says.......do it and you are taking a chance, and if the driver is heavy footed, a rather large one.

 

[Thomas_Si]

Mass does have an effect in spinning the wheel up to speed, resistance to overcome is greater and requires more energy.

 

[Brianmerc]

All
Many thanks for your excellent feedback and advice, especially the tire calculator and car bible link. I'm not so sure now that it's the right thing to do, to make a change from 15" to 17".

I'll keep you posted on how things develop.

 

[sledge]

Mass does have an effect in spinning the wheel up to speed, resistance to overcome is greater and requires more energy.

True but in this case its not an issue, neither is Power.......Mass is a factor when calculating acceleration rates however this issue relates soley to Torque, more specifically the amount the g/box will see as an increase with larger diameter wheels fitted. The rate of acceleration of the wheel, be it relatively fast or slow will not cause catastrophic damage to the gearbox and therefore does not even come into it......unless you know something I dont.

Mass is not a factor in the calculation of Torque if Force is known and in this case Force has not changed and is just a nominal value of no importance to the outcome, hence the "no consequence" comment.

Total Mass of the car needs to be known in order to calculate the amount of Torque needed to accelerate it. The Mass of the wheels on their own is not a factor. From the calculated value design parameters for the g/box can be established in the form of a maximum weight and Torque capacity but when you are dealing with a total of say 2000kg the 5kg or so saving that lightweight alloys might give you becomes totaly insignificant. You would save more Mass by never filling the car more than half full with petrol and if someone got in there with you it would really throw things out.

Note points 2 and 4

http://www.ehow.co.uk/how_5009233_calculate-required-torque-vehicle.html















http://www.calculatoredge.com/new/torque.htm

 

[Thomas_Si]

I would have thought that the highest load on the driveshafts, gearbag et al would be starting a car from still, rotational mass will have an impact in this regard as more torque is required to overcome the inertia forces to get the car moving.

We've opened a very old can of worms again haven't we lol:devil:

 

[sledge]

Sorry Tom.........I cant see any relevance in that statement nor does it even begin to make sense.

Get a copy of Kempes, read it and everything will make sense.

Kempe's Engineers Year Book Kempe's Engineer's Year Book: Amazon.co.uk: Jack H. Stephens, Quayle: Books

 

[Caravadossi]

My 18 year old son has a 2008 Grande Punto Stripe 1.2 and he wants to change the wheels. The current wheels are 15" and he wants to change to 17" Wolfraces ... I don't understand is how the speedo will still be accurate with the bigger wheels? Surely it will need recalibrating as 1 revolution of the 17" wheel will cover a greater distance/circumference than the 15" wheel!

Brian, consider - there are four overall within spec options given (certainly in my handbook) … 175/65R15, 205/45R17, 195/55R16 & 185/65R15 … however, the 205/45R17 falls outside the spec for the 1.2 & 1.4/8v models.

Whatever the contrasting argument for a size outside the FIAT design teams view & the `physics’ of it – what will your lad’s insurance company have to $ay on the matter?

On the speedo effect, enter your numbers into a tyre-calc – then note the revs/mile for each tyre. I believe they will show 833 (± 9) revs/mile - & within spec, & then I’d argue within the designed envelope for the speedo … & thus legal. For example, to follow your reasoning: one rev of the 17” (205/45R17) will cover a greater distance/circ than a 15” (175/65R15) – but will not cover a greater dist/circ than the 16” (195/55R16) … or the 15” (185/65R15).

-------------------------------------
GP 1.2/8v - 185/65R15

 

[Brianmerc]

Brian, consider - there are four overall within spec options given (certainly in my handbook) … 175/65R15, 205/45R17, 195/55R16 & 185/65R15 … however, the 205/45R17 falls outside the spec for the 1.2 & 1.4/8v models.

Whatever the contrasting argument for a size outside the FIAT design teams view & the `physics’ of it – what will your lad’s insurance company have to $ay on the matter?

On the speedo effect, enter your numbers into a tyre-calc – then note the revs/mile for each tyre. I believe they will show 833 (± 9) revs/mile - & within spec, & then I’d argue within the designed envelope for the speedo … & thus legal. For example, to follow your reasoning: one rev of the 17” (205/45R17) will cover a greater distance/circ than a 15” (175/65R15) – but will not cover a greater dist/circ than the 16” (195/55R16) … or the 15” (185/65R15).

-------------------------------------
GP 1.2/8v - 185/65R15

Some great feedback guys, I'm very impressed with the level of technical knowledge on this forum. I'm a chartered mechanical engineer by background and a E320CDI Mercedes owner. Nothing like this level of technical expertise on the corresponding MB forum.

Thanks for the information on what the handbook says, a good guide, not be disregarded.

Re insurance I've yet to contact them but I suspect it may be a problem, especially as he's under 21.

Just off to take other son to play football, will be back on later.

 

[ut745]

Hi mate, my friend had changed his alloys on his 1.2 grande punto to 17" TSW alloys and then later to 17" Wolfrace alloys, he had no problems at all with them.... hope this helps.


these are the TSW's he had http://www.tsw-wheels.co.uk/?section=16&wheel_id=75

and heres the wolfrace alloys he had ... http://alloywheelsdirect.wolfrace.com/products/Wolfrace-Eurosport-Street-Hustle-7x17".html

 

[dpr59]

As a chemist I'm not brilliant at physics but....
Won't the torque figure come from the total rolling radius of the wheel and tyre.

Hence, maintaining the RR with the correct tyre profile for size will..
1. Maintain energy /stress in gearbox
2. Ensure speedo accuracy.

However the greater tyre footprint will increase grip levels and through this route inrease stresses in the areas already discussed, if driven aggressively.
ie it's be harder to spin the wheels up an a dry road.

Well, that's how I'd see the increase in any gearbox failures

 

[Ffoxy]

Hi mate, my friend had changed his alloys on his 1.2 grande punto to 17" TSW alloys and then later to 17" Wolfrace alloys, he had no problems at all with them.... hope this helps.


these are the TSW's he had http://www.tsw-wheels.co.uk/?section=16&wheel_id=75

and heres the wolfrace alloys he had ... http://alloywheelsdirect.wolfrace.com/products/Wolfrace-Eurosport-Street-Hustle-7x17".html

"Had"? There's time... unless he moved on and some other buyer got affected.

 

[Highlander]

DONT DO IT. My fishig club sec got a new Grande Punto 1.2 delivered new with 17 inch wheel option fitted. Gearbox went within a year Fiat wiped there hands of the claim, Dealer had to replace box.

cheers Ian

 

[Brianmerc]

DONT DO IT. My fishig club sec got a new Grande Punto 1.2 delivered new with 17 inch wheel option fitted. Gearbox went within a year Fiat wiped there hands of the claim, Dealer had to replace box.

cheers Ian

Seems like a very compelling reason not to do it!!

 

[ut745]

"Had"? There's time... unless he moved on and some other buyer got affected.

sorry I dont understand what you mean

 

[Ffoxy]

sorry I dont understand what you mean

OK, you used the word "had" twice which is implying the pest tense.
Hi mate, my friend had changed his alloys on his 1.2 grande punto to 17" TSW alloys and then later to 17" Wolfrace alloys, he had no problems at all with them.... hope this helps.

So your friend either doesnt have the car anymore or he took the 17's off, or sold the car before any problems occur.

One example of it being OK Posted in here doesnt outweigh the majority who have Posted in this Forum with resulting gearbox / final drive breakages.

Of course there may be thousands who have had no problem, they just dont Post in here.

But it would seem the smart thing to do is keep wheel sizes inside the spec of the designers by model type as the 1.2 doesnt seem strong enough to cope.

 

[dannygp]

I was going to suggest going for some Fiat alloys like I did and letting him choose colour, etc, to help with insurance. But lets face it, the car won't be driven 100% of the time in a manner that is needed to keep the gearbox in one piece.

Some things in life arent ment to be and unfortunatly I think he's going to shout at you when you tell him he can't get any