Wheel/Tyre sizes etc....

A

AlanJ

Elite
 North Yorks
Found this website which may be of use - excellent explanations of wheel/tyre sizes and markings which people may find of use.

http://www.carbibles.com/tyre_bible.html
 
i was wondering if its possible to increase my sidewall. im running 225/40/18s right now and im thinking of changing to 225/45/18 when they need replaced. i have no clue if im alowed to do this
 
My winter tyres are 255/40/18 and 225/45/18 and the speedo reads about 3% higher than the stock 255/35 and 225/40. This isn't really an issue as speedos usually read a little under speed anyway so it now reads the actual speed as checked by my GPS.
 
Does anyone know the widest tyres that I can fit on my BMW/BBS 18" 107 Elipsode Alloys, I want to go as wide as poss to try & protect the rims when 'kerb parking'

At the moment they have:
225 / 40 /18
225 / 35 /18


Regards,
Paul
 
Half Colin said:
My winter tyres are 255/40/18 and 225/45/18 and the speedo reads about 3% higher than the stock 255/35 and 225/40. This isn't really an issue as speedos usually read a little under speed anyway so it now reads the actual speed as checked by my GPS.
Click to expand...
Construction & Use regulations state that the speedo must never UNDER-read, but can OVER-read by upto 10% - but manufacturers usually work to a tighter tolerance of upto 5%.

Otherwise you'd have a defence for speeding owing to your speedo showing you doing 30mph when you were actually doing 33mph. It's also one of the reasons I don't have any pity for anyone crying about getting caught for being 'just over the limit', as you'd have to be speeding by your own speedo to have any chance of doing more than the speed limit.

If your's was under-reading previously, then you either had the wrong tyres on, or you have a problem with your speedo.
 
Whiteknight said:
Does anyone know the widest tyres that I can fit on my BMW/BBS 18" 107 Elipsode Alloys, I want to go as wide as poss to try & protect the rims when 'kerb parking'

At the moment they have:
225 / 40 /18
225 / 35 /18

If I go much wider, will I need spacers?

Regards,
Paul
Click to expand...


Maybe I should post this in a new topic, I have used the search, but can't find the answer :cry:
 
Whiteknight said:
Maybe I should post this in a new topic, I have used the search, but can't find the answer :cry:
Click to expand...
Why are you running a 225/35 on the rear? I thought the options were 225/40/18 all around, or 225/40/18 and 255/35/18 on front & rear respectively. Simply fitting the 255/35/18 to the rear 8.5j wheel will protect it a bit more.

If it's just rim protection your after then find a brand with a wider protection strip. And don't forget that a 225 tread isn't the same from all manufacturers, some measure it differently and others just have a wider tyre. A bit of research on your part will be required to find out exactly who/what makes the widest and the one with the most protection.
 
mmm-five said:
Half Colin said:
My winter tyres are 255/40/18 and 225/45/18 and the speedo reads about 3% higher than the stock 255/35 and 225/40. This isn't really an issue as speedos usually read a little under speed anyway so it now reads the actual speed as checked by my GPS.
Click to expand...
Construction & Use regulations state that the speedo must never UNDER-read, but can OVER-read by upto 10% - but manufacturers usually work to a tighter tolerance of upto 5%.

Otherwise you'd have a defence for speeding owing to your speedo showing you doing 30mph when you were actually doing 33mph. It's also one of the reasons I don't have any pity for anyone crying about getting caught for being 'just over the limit', as you'd have to be speeding by your own speedo to have any chance of doing more than the speed limit.

If your's was under-reading previously, then you either had the wrong tyres on, or you have a problem with your speedo.
Click to expand...
No, came across wrong - I meant the actual speed was under what was shown on the speedo so yes of course you are right the speedo is reading higher than the actual speed. With the higher profile tyres the speedo is reading about 3% less with the overall effect of it now showing near enough the actual speed.
 
Don't think that's possible - you just need to check with a GPS and mentally adjust. With stock tyres my speedo shows about 75 when the actual speed is 70 - with my higher profile winter tyres at 70 the speedo shows 70.
 
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