#1: Wider tyres fitted, big decrease of maximum speed. Author: Ange47, Location: Bedford, UK.Posted: Thu Jan 10, 2013 4:12 pm ---- Hey guys, yesterday I finally got to replace my old and thin tyres (175/65/R14) with some new wider tyres (195/55/R15). I noticed almost no difference while driving through the city, but when I got to the highway to test the new tyres I noticed that my car hardly reached 90 mph. It is a 1.1 l and with the old tyres I could reach that speed without any strife. I am asking you guys because in UK, as far as I've understood, you can change your tyres to the size you want (or atleast sth like that), without being considered illegal, and so you all get wider tyres fitted on your 206's... Afterwards nobody knows better than you
(did I make many grammar mistakes? lol)
#2: Re: Wider tyres fitted, big decrease of maximum speed. Author: Dabamash, Location: The car in frontPosted: Thu Jan 10, 2013 5:15 pm ----
Ange47 wrote:
I noticed that my car hardly reached 90 mph.
You're going to get stick for this...
It's legal, but it's obviously going to impair your top speed and acceleration as your car is pulling a lot of extra weight. Not to mention the added traction.
#3: Re: Wider tyres fitted, big decrease of maximum speed. Author: Mr_Akina, Location: SomersetPosted: Thu Jan 10, 2013 5:19 pm ----
Quote::
(did I make many grammar mistakes? lol)
Better than my Italian!
Your problem is friction. You've now got more rubber in contact with the road and no more power to fight it. Your cornering grip is improved, but straight-line speed will decrease.
Oh, and your speedometer will be reading wrong because your wheel/tyre is bigger. If you are showing 60mph, you'll actually be doing nearer 58mph.
#4: Re: Wider tyres fitted, big decrease of maximum speed. Author: Edward, Location: In the garagePosted: Thu Jan 10, 2013 5:25 pm ---- Its more to do with aerodynamics...
#5: Re: Wider tyres fitted, big decrease of maximum speed. Author: Andrew, Location: Black Country Ay IPosted: Thu Jan 10, 2013 6:06 pm ---- Speedo reading is out maybe? As it should be 185/55/15 not 195 iirc
#6: Re: Wider tyres fitted, big decrease of maximum speed. Author: Junglingo, Location: HampshirePosted: Thu Jan 10, 2013 6:13 pm ---- yeah your speedo will be reading less than actual speed due to the bigger wheel size. the distance and time to do one full rotaion of the wheels is longer.
#7: Re: Wider tyres fitted, big decrease of maximum speed. Author: Ange47, Location: Bedford, UK.Posted: Thu Jan 10, 2013 7:58 pm ---- Thanks for your answers guys. Maybe I didn't get to the point. I just wanted to know if somebody who switched to wider tyres, experienced the same big loss of maximum speed. I know there are many people in this forum with 1.1 l or 1.4 l who did the same "upgrade"...
#8: Re: Wider tyres fitted, big decrease of maximum speed. Author: E5GDM, Location: EssexPosted: Fri Jan 11, 2013 2:28 am ----
Mr_Akina wrote:
Oh, and your speedometer will be reading wrong because your wheel/tyre is bigger. If you are showing 60mph, you'll actually be doing nearer 58mph.
Are you sure? As I think the reduction in tyre ratio will counter the increase in wheel diameter.
#9: Re: Wider tyres fitted, big decrease of maximum speed. Author: macca1411, Location: Westhoughton, LancashirePosted: Fri Jan 11, 2013 4:50 am ----
E5GDM wrote:
Mr_Akina wrote:
Oh, and your speedometer will be reading wrong because your wheel/tyre is bigger. If you are showing 60mph, you'll actually be doing nearer 58mph.
Are you sure? As I think the reduction in tyre ratio will counter the increase in wheel diameter.
E5 is right. With the 175/65/R14 the speedo will read 70mph when the actual speed of the car with 195/55R15 fitted will be around 71-72mph.
The difference is minimal but the speedo will show less than the actual speed.
There are 2 ways to find how far out your speedo is. The easy and cheapest way is to use GPS. Most sat-navs have a speed display incorporated into them, so just use one of them.
The other more expensive (and IMO, pointless) option is to have your speedo calibrated.
The rolling resistance has increased due to the wider tyres, and with a 1.1 you do not have enough torque to compensate for this, hence slower acceleration which results in a longer period to reach top speed. You may find that the performance increases slightly on a wet surface though.
You could adjust your tyre pressures to get the best performance, although I would suggest you stay within the manufacturers specifications.
You could start messing with gearbox and final drive ratios or changing the suspension set-up. But at the end of the day it's a 1.1. They were never designed for performance.
#10: Re: Wider tyres fitted, big decrease of maximum speed. Author: Steve206, Location: UKPosted: Fri Jan 11, 2013 5:45 am ---- In PP you can adjust your tyre and wheel size so it auto corrects the speedo reading.
#11: Re: Wider tyres fitted, big decrease of maximum speed. Author: Timon2210, Location: PalestinePosted: Fri Jan 11, 2013 7:41 am ----
Steve206 wrote:
In PP you can adjust your tyre and wheel size so it auto corrects the speedo reading.
I have a 1.4,with 195/55/15,and I didn't notice any diff. between driving in the city or the motor way,but things for 1.1 must be diff.
#12: Re: Wider tyres fitted, big decrease of maximum speed. Author: Mattie-RS, Location: A Track near you ;)Posted: Fri Jan 11, 2013 7:44 am ----
Edward wrote:
Its more to do with aerodynamics...
This and the extra weight!
There will be a slight change in speedo due to the change but that's it.
#13: Re: Wider tyres fitted, big decrease of maximum speed. Author: Ange47, Location: Bedford, UK.Posted: Fri Jan 11, 2013 8:11 am ----
Timon2210 wrote:
Steve206 wrote:
In PP you can adjust your tyre and wheel size so it auto corrects the speedo reading.
I have a 1.4,with 195/55/15,and I didn't notice any diff. between driving in the city or the motor way,but things for 1.1 must be diff.
Thanks for your reply Timon, I've always known that my 1.1 was "faster" than other people's 1.1's, maybe because we bought it back in 2002 and we've always owned it, so we've treated it as well as possible. But with the new tyres, while I'm on the highway it's like there are 5 people in the car. Luckily the "problem" shows up only on that kind of roads...
#14: Re: Wider tyres fitted, big decrease of maximum speed. Author: Mr_Akina, Location: SomersetPosted: Fri Jan 11, 2013 9:05 am ----
macca1411 wrote:
E5GDM wrote:
Mr_Akina wrote:
Oh, and your speedometer will be reading wrong because your wheel/tyre is bigger. If you are showing 60mph, you'll actually be doing nearer 58mph.
Are you sure? As I think the reduction in tyre ratio will counter the increase in wheel diameter.
E5 is right. With the 175/65/R14 the speedo will read 70mph when the actual speed of the car with 195/55R15 fitted will be around 71-72mph.
I'm pretty sure 195/55/15 will be a bigger overall diameter wheel compared to the 175/65/14, so the speedo will read faster than it is.
If it was a 195/45/15, then it would be doing 62mph instead of the 60mph the speedo is showing.
Either way, it's relatively nothing. You've put a heavier wheel on and increased the drag from the tyres. That's inevitably going to slow you down.
#15: Re: Wider tyres fitted, big decrease of maximum speed. Author: kandlbarrett, Location: SwindonPosted: Fri Jan 11, 2013 11:29 am ---- This website is a tyre size / speed calculator.
Your new tyre size will reduce your indicated speed by 2.02%. To keep the maths easy call it 2%
Your previously indicated 90 will now be an indicated 88.2.
Your tyres are wider so some extra rolling resistance just from that and different manufactures tyres also have different rolling resistance.
If your tracking is wrong the wider tyres will probably emphasise that and also have higher drag than your thinner ones, though I don't suspect by very much.
Check the pressures and have a 4 wheel alignment done - yes I know - I have a pet topic and it is 4 wheel alignment!
EDIT: If it was me with a 1.1 then I would be fitting the thinest tyres possible. Economy and possibly (I doubt it though) slightly higher top speed.
Either:-
155 / 75 /14 speedo reads the same (overall diameter is almost unchanged) and more economy from thinner tyres.
175 / 60 / 15 same width (hopefully no change to rolling resistance) and overall same diameter so speedo reads the same.
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