Technical punto hgt top speed

[matty seasider]

when i was on a private road last week.......


i wanted to see if my hgt would reach the 127mph top speed fiat claim....

and i was dissapointed to find it would only get to 120mph....

would having 17"wheels make that much a difference??

have any of u punto hgt owners, driven your car with 15's and then swapped for 17's and noticed a big difference in power etc? as my car came with 17's so have never driven it with 15's on...

if anyone wants to do a swap with me, i have a set of tsw reflex 17" alloys with good tyres.....

would love the standard 15" fiat ones...

 

[DanGil]

It should still be pulling at 120 no problem.

 

[Decron]

Have you kept the rolling radius the same (Ie fitted smaller profile tyres)?

If the wheels have a larger circumfrence then in theory one revolution will cover more ground which means it should in theory increase your top end.

However, fitting larger wheels has a few draw backs which will easily outweigh this gain. The increased footprint increases drag/friction - responsible for reduced top speed, reduced acceleration and increased fuel consumption as the car can only convert so much of the energy to kinetic. It can also upset the handling and almost definately the ride.

The 17"s will also weight a lot more than the 15"s (Unless they are very expensive Mag/Ally types) and increasing the unsprung weight will also contribute to all of the above issues especially as the HGT motor as standard isn't exactly a torque monster.

I would have thought that they were slowing you down.