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A little help from members that are clued up on wheels.....
#1
I currently run a 2014 XTR multispace, Semi automatic.

I have tried doing the research myself, but just wondered from the collective if i have overlooked something important.

On my XTR i am running 205/65/15 tyres on stock steel wheels and have the chance of very good condition Citroen DS3 Clover design 17inch with 205/45/17 tyres.

After looking around on the internet, i'm sure these are going to fit fine ??  but on a tyre rolling radius comparison site it mentions the difference in speed at 70mph the actual speed is 68.85 mph, is this something i should be worried about or is there something i have forgot like will it effect the automatic gears ??

Hoping somebody can advise.....

[Image: 2q8wnsh.jpg]
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#2
It's nothing to worry about as the wheel get's bigger the profile of the tyre goes down  have a look at 205 /40/17 see if that put's it right. Smile 1.15 out is not bad
                                     Smile  It's too orangey for crow's It's just for me and my dog  Smile

                                                        Heart Heart Love a lot trust a few  Dodgy
 
                                                        

                                        
[-] The following 1 user says Thank You to Jed Clampit for this post:
  • Doodlebug
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#3
The wheel and tyre combination i have been offered is no good, looking at this :
http://www.1010tires.com/Tools/Tire-Size.../205-55R17

I need to go more for a 205 / 50 / 17

Plan B  Confused
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#4
Just go to a different site there are plenty on line or look on ebay find the wheels you like look for a phone number on the bottom of the page give the a ring 55/50 profile is to high with 17 you need some thing like 40/45.
                                     Smile  It's too orangey for crow's It's just for me and my dog  Smile

                                                        Heart Heart Love a lot trust a few  Dodgy
 
                                                        

                                        
[-] The following 1 user says Thank You to Jed Clampit for this post:
  • Doodlebug
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#5
For future reference, 205/50r17 keeps the rolling radius bang on pretty much and is the correct size for the 17” tyre size vs the 195/65r15
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#6
(24-03-2016, 10:55 PM)Doodlebug Wrote:  I currently run a 2014 XTR multispace, Semi automatic.

I have tried doing the research myself, but just wondered from the collective if i have overlooked something important.

On my XTR i am running 205/65/15 tyres on stock steel wheels and have the chance of very good condition Citroen DS3 Clover design 17inch with 205/45/17 tyres.

After looking around on the internet, i'm sure these are going to fit fine ??  but on a tyre rolling radius comparison site it mentions the difference in speed at 70mph the actual speed is 68.85 mph, is this something i should be worried about or is there something i have forgot like will it effect the automatic gears ??

Hoping somebody can advise.....

[Image: 2q8wnsh.jpg]

No speedo is 100% accurate. This is why the law allows 3% for inaccuracy in the design . Just be careful with your insurance , let them know you've changed your wheels .  If it helps my own car ,a MK  1 Berlingo is reading 5 mph an hour fast at 70 , better that way than reading low as that could mean that your potentially doing 75 at 70 mph .
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#7
(24-03-2016, 10:55 PM)Doodlebug Wrote:  I currently run a 2014 XTR multispace, Semi automatic.

I have tried doing the research myself, but just wondered from the collective if i have overlooked something important.

On my XTR i am running 205/65/15 tyres on stock steel wheels and have the chance of very good condition Citroen DS3 Clover design 17inch with 205/45/17 tyres.

After looking around on the internet, i'm sure these are going to fit fine ??  but on a tyre rolling radius comparison site it mentions the difference in speed at 70mph the actual speed is 68.85 mph, is this something i should be worried about or is there something i have forgot like will it effect the automatic gears ??

Hoping somebody can advise.....

[Image: 2q8wnsh.jpg]
I upgraded to OZ wheels that are 16 inch. 215/55/16 XTR semi auto the same as yours 

[Image: attachment.php?aid=4113]
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#8
Use the speed on a sat nav or phone app to check your actual speed, you will see the difference between actual and speedo reading at various speeds. GPS is more accurate than speedometer which can read as much as 10% under your actual speed but you are not allowed any leeway in the other direction. If your speedo reads 70 when you are doing 75 you are going to have problems. There is no 3% allowance on speed limits this is entirely up to whoever is operating the speed trap and the magistrate on the day whether you get pulled and fined..
So where does this bit go then ?
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#9
(06-01-2019, 08:56 AM)ffrenchie Wrote:  Use the speed on a sat nav or phone app to check your actual speed, you will see the difference between actual and speedo reading at various speeds. GPS is more accurate than speedometer which can read as much as 10% under your actual speed but you are not allowed any leeway in the other direction. If your speedo reads 70 when you are doing 75 you are going to have problems. There is no 3% allowance on speed limits this is entirely up to whoever is operating the speed trap and the magistrate on the day whether you get pulled and fined..

Sat navs: agree entirely, and I check every car I drive this way for peace of mind, but a bit of advice from an old trucker: inner city areas (tall buildings) and dense forests cause satellite signal bounces which confuse sat navs! Do it in the open. Of course, this is not a flawless method and probably couldn't be used as evidence of not speeding in court!

My understanding of speedo tolerances is different to yours: what I've heard over the years is that they can legally display anywhere from -15% to +5% of actual speed (i.e when it reads 50 your actual speed could be anything from 42.5 to 52.5mph, or at 70 you could be going as fast as 73.5mph, but not 75); this was set decades ago when speedo design was primitive, but is kept today (and kept quiet) as it allows mfrs to 'underset' modern speedos to reduce speeding issues on the roads. Certainly, not every gatso flash results in a letter; imho this may be because prosecuting 'slight' offenders would result in too much paperwork and expense in dealing with all the 'but my speedo said I wasn't speeding' claims, which can legitimately be made and would require the offending speedo to be properly assessed. In any case, there does seem to be a grey area between too fast and not, at least in legal practice if not also in law.

Tachos on the other hand, the 'spies' fitted to PSVs and trucks etc., must be accurate to within +/-1% of actual speed and must be recalibrated regularly. Plus the cruise controls in the trucks I drive have an 'eco' function whereby you can set how far over or under the set cruising speed the truck can go before the cc brings its speed back into line. I like mine set at +/-1mph for accurate control, but it can be set to +/-5mph (or more with some models) to save a lot of fuel by not powering up hills, but this results in trucks charging down steep hills at around 60mph then crawling up them at 45, or so it seems. I personally prefer safety to economy and am glad my current employer hasn't yet learnt about the benefits of the eco setting.

When I'm driving on the flat on a motorway in a 50 limit, I find that if I cruise with my cc set any higher than about 47 +/-1 mph, I risk undertaking all the middle lane hogs! In other words, it subjectively seems that car speedos on average are about 5% under, give or take. So it's not so much about who is right as who is being considerate.
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#10
Hi - check out page 9 on this document:

http://library.college.police.uk/docs/ap...idance.pdf

There's the ACPO guidelines for UK speed enforcement - the '10% rule' or 'allowance' only applies at 20mph - by the time you get to 70 mph it's only + 3 mph. Above those limits then you get into the 'fixed penalty when education is not appropriate band' and that is 10% plus - but read the paragraph below the table about discretion - so if you're having a grumpy day and so is the Police Officer then anything goes [back in the day this was 'the attitude test' - no idea what it's called nowadays]. Smile nicely and be well behaved and you may get to go on a 'Speed Awareness Course' instead of picking up three points.

So go for the SatNav/GPS - it is interesting -  on the Berlingo it was always a bit hit and miss with the analogue dial but on the Mini with the digital readout we have an indicated 30 mph is around a real 28mph and 74 mph indicated is a true 70 mph on the GPS. On the van it's pretty similar with 63 mph indicated being a true 60 mph. Other than a Morris Minor that had been retrofitted with a Ford five speed gearbox I've not come across any car yet that under reads the true speed.

[edit - skip the next paragraph it's just me venting :-) ]

Finally ... Rasputin has hit a nail on the head for me - I do a lot of motorway mileage driving horses around - no outside lane, speed limited to 60 mph and 'undertaking' is (strictly speaking) driving without due care. The CLOC (Centre Lane Owners Club) have no idea how much grief/delay they can cause - only thing worse is when their SatNav yells at them to 'keep right for the M6' and they decide to cut across the two inner lanes 'cos they cannot read road signs and do not want to go around the M42. Grrrrr
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